Science.gov

Sample records for space-based microlensing survey

  1. Galactic Planet Population and Astrophysics with a Space-Based Microlensing Survey

    NASA Astrophysics Data System (ADS)

    Blandford, Roger

    Microlensing surveys have detected hundreds of events in the direction of the Galactic bulge, providing valuable information on the population of faint stars otherwise undetectable in our Galaxy. Within this sample of events approximately 20 planets have been uncovered, with about half of them being either unbound or at large separation (greater than 100 AU) from their host star. The majority of the current microlensing planetary detections have come from rare, high- magnification events which are alerted and immediately followed on with high cadence ground- based observations from a network of collaborations around the world. These results have established that microlensing is an effective technique that can be used distinguish planets from their host star, in particular planets at large separation, a regime in which the radial velocity and transiting methods for planet detection lose sensitivity. The next step in studies of Galactic microlensing involve development of space-based surveys, which provide better angular resolution and the ability resolve more faint stars. In anticipation of proposed spaced-based microlensing surveys such as the WFIRST satellite, this research will develop theoretical tools to understand and interpret future large samples of Galactic microlensing observations. We will study how to optimize a space-based microlensing survey to obtain the maximal scientific output for the costs available. As part of this theoretical research we plan to develop a fast and efficient numerical code that can be distributed to the larger community, incorporating modern aspects of Galactic astrophysics into microlensing theory. The simulations will include effects that will become important for space-based surveys, such as the finite size of main sequence source stars and understanding the microlensing signals from multiple planets. A major output of our analysis will be a quantification of the planetary detection efficiency over the entire range of planet

  2. Mass Measurements of Isolated Objects from Space-based Microlensing

    NASA Astrophysics Data System (ADS)

    Zhu, Wei; Calchi Novati, S.; Gould, A.; Udalski, A.; Han, C.; Shvartzvald, Y.; Ranc, C.; Jørgensen, U. G.; Poleski, R.; Bozza, V.; Beichman, C.; Bryden, G.; Carey, S.; Gaudi, B. S.; Henderson, C. B.; Pogge, R. W.; Porritt, I.; Wibking, B.; Yee, J. C.; SPITZER Team; Pawlak, M.; Szymański, M. K.; Skowron, J.; Mróz, P.; Kozłowski, S.; Wyrzykowski, Ł.; Pietrukowicz, P.; Pietrzyński, G.; Soszyński, I.; Ulaczyk, K.; OGLE Group; Choi, J.-Y.; Park, H.; Jung, Y. K.; Shin, I.-G.; Albrow, M. D.; Park, B.-G.; Kim, S.-L.; Lee, C.-U.; Cha, S.-M.; Kim, D.-J.; Lee, Y.; KMTNET Group; Friedmann, M.; Kaspi, S.; Maoz, D.; WISE Group; Hundertmark, M.; Street, R. A.; Tsapras, Y.; Bramich, D. M.; Cassan, A.; Dominik, M.; Bachelet, E.; Dong, Subo; Figuera Jaimes, R.; Horne, K.; Mao, S.; Menzies, J.; Schmidt, R.; Snodgrass, C.; Steele, I. A.; Wambsganss, J.; RoboNeT Team; Skottfelt, J.; Andersen, M. I.; Burgdorf, M. J.; Ciceri, S.; D'Ago, G.; Evans, D. F.; Gu, S.-H.; Hinse, T. C.; Kerins, E.; Korhonen, H.; Kuffmeier, M.; Mancini, L.; Peixinho, N.; Popovas, A.; Rabus, M.; Rahvar, S.; Tronsgaard, R.; Scarpetta, G.; Southworth, J.; Surdej, J.; von Essen, C.; Wang, Y.-B.; Wertz, O.; MiNDSTEP Group

    2016-07-01

    We report on the mass and distance measurements of two single-lens events from the 2015 Spitzer microlensing campaign. With both finite-source effect and microlens parallax measurements, we find that the lens of OGLE-2015-BLG-1268 is very likely a brown dwarf (BD). Assuming that the source star lies behind the same amount of dust as the Bulge red clump, we find the lens is a 45 ± 7 {M}{{J}} BD at 5.9 ± 1.0 kpc. The lens of of the second event, OGLE-2015-BLG-0763, is a 0.50 ± 0.04 {M}ȯ star at 6.9 ± 1.0 kpc. We show that the probability to definitively measure the mass of isolated microlenses is dramatically increased once simultaneous ground- and space-based observations are conducted.

  3. Faint detection of exoplanets in microlensing surveys

    SciTech Connect

    Brown, Robert A.

    2014-06-20

    We propose a new approach to discovering faint microlensing signals below traditional thresholds, and for estimating the binary-lens mass ratio and the apparent separation from such signals. The events found will be helpful in accurately estimating the true distribution of planetary semimajor axes, which is an important goal of space microlensing surveys.

  4. Planet Sensitivity from Combined Ground- and Space-based Microlensing Observations

    NASA Astrophysics Data System (ADS)

    Zhu, Wei; Gould, Andrew; Beichman, Charles; Calchi Novati, Sebastiano; Carey, Sean; Gaudi, B. Scott; Henderson, Calen B.; Penny, Matthew; Shvartzvald, Yossi; Yee, Jennifer C.; Udalski, A.; Poleski, R.; Skowron, J.; Kozłowski, S.; Mróz, P.; Pietrukowicz, P.; Pietrzyński, G.; Szymański, M. K.; Soszyński, I.; Ulaczyk, K.; Wyrzykowski, Ł.; OGLE Collaboration; Abe, F.; Barry, R. K.; Bennett, D. P.; Bhattacharya, A.; Bond, I. A.; Freeman, M.; Fukui, A.; Hirao, Y.; Itow, Y.; Koshimoto, N.; Ling, H.; Masuda, K.; Matsubara, Y.; Muraki, Y.; Nagakane, M.; Ohnishi, K.; Saito, To.; Sullivan, D. J.; Sumi, T.; Suzuki, D.; Tristram, P. J.; Rattenbury, N.; Wakiyama, Y.; Yonehara, A.; MOA Collaboration; Maoz, D.; Kaspi, S.; Friedmann, M.; The Wise Group

    2015-12-01

    To move one step forward toward a Galactic distribution of planets, we present the first planet sensitivity analysis for microlensing events with simultaneous observations from space and the ground. We present this analysis for two such events, OGLE-2014-BLG-0939 and OGLE-2014-BLG-0124, which both show substantial planet sensitivity even though neither of them reached high magnification. This suggests that an ensemble of low to moderate magnification events can also yield significant planet sensitivity, and therefore probability, for detecting planets. The implications of our results to the ongoing and future space-based microlensing experiments to measure the Galactic distribution of planets are discussed.

  5. Discovering Extrasolar Planets with Microlensing Surveys

    NASA Astrophysics Data System (ADS)

    Wambsganss, J.

    2016-06-01

    An astronomical survey is commonly understood as a mapping of a large region of the sky, either photometrically (possibly in various filters/wavelength ranges) or spectroscopically. Often, catalogs of objects are produced/provided as the main product or a by-product. However, with the advent of large CCD cameras and dedicated telescopes with wide-field imaging capabilities, it became possible in the early 1990s, to map the same region of the sky over and over again. In principle, such data sets could be combined to get very deep stacked images of the regions of interest. However, I will report on a completely different use of such repeated maps: Exploring the time domain for particular kinds of stellar variability, namely microlens-induced magnifications in search of exoplanets. Such a time-domain microlensing survey was originally proposed by Bohdan Paczynski in 1986 in order to search for dark matter objects in the Galactic halo. Only a few years later three teams started this endeavour. I will report on the history and current state of gravitational microlensing surveys. By now, routinely 100 million stars in the Galactic Bulge are monitored a few times per week by so-called survey teams. All stars with constant apparent brightness and those following known variability patterns are filtered out in order to detect the roughly 2000 microlensing events per year which are produced by stellar lenses. These microlensing events are identified "online" while still in their early phases and then monitored with much higher cadence by so-called follow-up teams. The most interesting of such events are those produced by a star-plus-planet lens. By now of order 30 exoplanets have been discovered by these combined microlensing surveys. Microlensing searches for extrasolar planets are complementary to other exoplanet search techniques. There are two particular advantages: The microlensing method is sensitive down to Earth-mass planets even with ground-based telecopes, and it

  6. Stellar Angular Diameter Relations for Microlensing Surveys

    NASA Astrophysics Data System (ADS)

    Adams, Arthur; Boyajian, Tabetha S.; von Braun, Kaspar

    2016-01-01

    Determining the physical properties of microlensing events depends on having accurate angular radii of the source star. Using long-baseline optical interferometry we are able to determine the angular sizes of nearby stars with uncertainties less than 2 percent. We present empirical estimates of angular diameters for both dwarfs/subgiants and giant stars as functions of five color indices which are relevant to planned microlensing surveys. We find in all considered colors that metallicity does not play a statistically significant role in predicting stellar size for the samples of stars considered.

  7. Space Based Dark Energy Surveys

    NASA Astrophysics Data System (ADS)

    Dore, Olivier

    2016-03-01

    Dark energy, the name given to the cause of the accelerating expansion of the Universe, is one of the most tantalizing mystery in modern physics. Current cosmological models hold that dark energy is currently the dominant component of the Universe, but the exact nature of DE remains poorly understood. There are ambitious ground-based surveys underway that seek to understand DE and NASA is participating in the development of significantly more ambitious space-based surveys planned for the next decade. NASA has provided mission enabling technology to the European Space Agency's (ESA) Euclid mission in exchange for US scientists to participate in the Euclid mission. NASA is also developing the Wide Field Infrared Survey Telescope-Astrophysics Focused Telescope Asset (WFIRST) mission for possible launch in 2024. WFIRST was the highest ranked space mission in the Astro2010 Decadal Survey and the current design uses a 2.4m space telescope to go beyond what was then envisioned. Understanding DE is one of the primary science goals of WFIRST-AFTA. This talk will review the state of DE, the relevant activities of the Cosmic Structure Interest Group (CoSSIG) of the PhyPAG, and detail the status and complementarity between Euclid, WFIRST and ot ambitious ground-based efforts.

  8. The WFIRST Microlensing Survey: Expectations and Unexpectations

    NASA Astrophysics Data System (ADS)

    Gaudi, B. Scott; Penny, Matthew

    2016-01-01

    The WFIRST microlensing survey will provide the definitive determination of the demographics of cool planets with semimajor axes > 1 AU and masses greater than that of the Earth, including free-floating planets. Together with the results from Kepler, TESS, and PLATO, WFIRST will complete the statistical census of planets in the Galaxy. These expectations are based on the most basic and conservative assumptions about the data quality, and assumes that the analysis methodologies will be similar to that used for current ground-based microlensing. Yet, in fact, the data quality will be dramatically better, and information content substantially richer, for the WFIRST microlensing survey as compared to current ground-based surveys. Thus WFIRST should allow for orders of magnitude improvement in both sensitivity and science yield. We will review some of these expected improvements and opportunities (the "known unknowns"), and provide a "to do list" of what tasks will need to be completed in order to take advantage of these opportunities. We will then speculate on the opportunities that we may not be aware of yet (the "unknown unknowns"), how we might go about determining what those opportunities are, and how we might figure out what we will need to do to take advantage of them.This work was partially supported by NASA grant NNX14AF63G.

  9. Preparing for the Kepler K2 Microlensing Survey: A Call to Arms

    NASA Astrophysics Data System (ADS)

    Penny, Matthew

    2015-01-01

    In 2016 the ninth campaign of K2 (the extended, two-wheel Kepler mission) will be targeted towards the Galactic bulge, where it will perform the first wide-field, space-based microlensing survey. This survey will discover tens of both bound and free-floating planets by itself, but its real value will come from simultaneous ground-based observations that will provide parallax measurements enabling both mass and distance measurements for the majority of these planets and their hosts. These will include the first ever measurements of free-floating planet masses.K2's immediate public data release policy offers a huge one-time-only opportunity to build up the US's expertise in exoplanetary microlensing surveys in preparation for the WFIRST mission. Unbeknownst to most astronomers at home and abroad, the US also owns the best instrument in the world for conducting ground-based microlensing surveys -- DECam on the Blanco 4m, whose etendue is a factor of 20 larger than OGLE's at equal resolution. A simultaneous survey using ~80 half nights on DECam (as part of a NOAO large survey program) could also make its data immediately public, catapulting US astronomers to the forefront of planetary microlensing surveys, measuring masses of and distances to microlensing exoplanets on a never-before-possible scale. This is an opportunity that should not be missed and I will outline ways in which you can get involved.

  10. Testing LMC Microlensing Scenarios: The Discrimination Power of the SuperMACHO Microlensing Survey

    SciTech Connect

    Rest, A; Stubbs, C; Becker, A C; Miknaitis, G A; Miceli, A; Covarrubias, R; Hawley, S L; Smith, C; Suntzeff, N B; Olsen, K; Prieto, J; Hiriart, R; Welch, D L; Cook, K; Nikolaev, S; Proctor, G; Clocchiatti, A; Minniti, D; Garg, A; Challis, P; Keller, S C; Scmidt, B P

    2004-05-27

    Characterizing the nature and spatial distribution of the lensing objects that produce the observed microlensing optical depth toward the Large Magellanic Cloud (LMC) remains an open problem. They present an appraisal of the ability of the SuperMACHO Project, a next-generation microlensing survey pointed toward the LMC, to discriminate between various proposed lensing populations. they consider two scenarios: lensing by a uniform foreground screen of objects and self-lensing of LMC stars. The optical depth for ''screen-lensing'' is essentially constant across the face of the LMC; whereas, the optical depth for self-lensing shows a strong spatial dependence. they have carried out extensive simulations, based upon actual data obtained during the first year of the project, to assess the SuperMACHO survey's ability to discriminate between these two scenarios. In the simulations they predict the expected number of observed microlensing events for each of their fields by adding artificial stars to the images and estimating the spatial and temporal efficiency of detecting microlensing events using Monte-Carlo methods. They find that the event rate itself shows significant sensitivity to the choice of the LMC luminosity function shape and other parameters, limiting the conclusions which can be drawn from the absolute rate. By instead determining the differential event rate across the LMC, they can decrease the impact of these systematic uncertainties rendering the conclusions more robust. With this approach the SuperMACHO Project should be able to distinguish between the two categories of lens populations and provide important constraints on the nature of the lensing objects.

  11. Determination of Microlensing Selection Criteria for the SuperMACHO Survey

    SciTech Connect

    Garg, A

    2008-10-10

    The SuperMACHO project is a 5 year survey to determine the nature of the lens population responsible for the excess microlensing rate toward the Large Magellanic Cloud observed by the MACHO project [1]. The survey probes deeper than earlier surveys unveiling many more extragalactic contaminants, particularly type Ia supernovae and active galactic nuclei. Using {approx}10{sup 7} simulated light curves of both microlensing events and type Ia supernovae we determine selection criteria optimized to maximize the microlensing detection efficiency while minimizing the contamination rate from non-microlensing events. We discuss these simulations and the selection criteria.

  12. Microlensing Surveys of M31 in the Wide Field Imaging ERA

    SciTech Connect

    Baltz, E.

    2004-10-27

    The Andromeda Galaxy (M31) is the closest large galaxy to the Milky Way, thus it is an important laboratory for studying massive dark objects in galactic halos (MACHOs) by gravitational microlensing. Such studies strongly complement the studies of the Milky Way halo using the Large and Small Magellanic Clouds. We consider the possibilities for microlensing surveys of M31 using the next generation of wide field imaging telescopes with fields of view in the square degree range. We consider proposals for such imagers both on the ground and in space. For concreteness, we specialize to the SNAP proposal for a space telescope and the LSST proposal for a ground based telescope. We find that a modest space-based survey of 50 visits of one hour each is considerably better than current ground based surveys covering 5 years. Crucially, systematic effects can be considerably better controlled with a space telescope because of both the infrared sensitivity and the angular resolution. To be competitive, 8 meter class wide-field ground based imagers must take exposures of several hundred seconds with several day cadence.

  13. The exoplanet microlensing survey by the proposed WFIRST Observatory

    NASA Astrophysics Data System (ADS)

    Barry, Richard; Kruk, Jeffery; Anderson, Jay; Beaulieu, Jean-Philippe; Bennett, David P.; Catanzarite, Joseph; Cheng, Ed; Gaudi, Scott; Gehrels, Neil; Kane, Stephen; Lunine, Jonathan; Sumi, Takahiro; Tanner, Angelle; Traub, Wesley

    2011-10-01

    The New Worlds, New Horizons report released by the Astronomy and Astrophysics Decadal Survey Board in 2010 listed the Wide Field Infrared Survey Telescope (WFIRST) as the highest-priority large space mission for the coming decade. This observatory will provide wide-field imaging and slitless spectroscopy at near infrared wavelengths. The scientific goals are to obtain a statistical census of exoplanets using gravitational microlensing, measure the expansion history of and the growth of structure in the Universe by multiple methods, and perform other astronomical surveys to be selected through a guest observer program. A Science Definition Team has been established to assist NASA in the development of a Design Reference Mission that accomplishes this diverse array of science programs with a single observatory. In this paper we present the current WFIRST payload concept and the expected capabilities for planet detection. The observatory, with science goals that are complimentary to the Kepler exoplanet transit mission, is designed to complete the statistical census of planetary systems in the Galaxy, from habitable Earth-mass planets to free floating planets, including analogs to all of the planets in our Solar System except Mercury. The exoplanet microlensing survey will observe for 500 days spanning 5 years. This long temporal baseline will enable the determination of the masses for most detected exoplanets down to 0.1 Earth masses.

  14. The Exoplanet Microlensing Survey by the Proposed WFIRST Observatory

    NASA Technical Reports Server (NTRS)

    Barry, Richard; Kruk, Jeffrey; Anderson, Jay; Beaulieu, Jean-Philippe; Bennett, David P.; Catanzarite, Joseph; Cheng, Ed; Gaudi, Scott; Gehrels, Neil; Kane, Stephen; Lunine, Jonathan; Sumi, Takahiro; Tanner, Angelle; Traub, Wesley

    2012-01-01

    The New Worlds, New Horizons report released by the Astronomy and Astrophysics Decadal Survey Board in 2010 listed the Wide Field Infrared Survey Telescope (WFIRST) as the highest-priority large space mission for the . coming decade. This observatory will provide wide-field imaging and slitless spectroscopy at near infrared wavelengths. The scientific goals are to obtain a statistical census of exoplanets using gravitational microlensing. measure the expansion history of and the growth of structure in the Universe by multiple methods, and perform other astronomical surveys to be selected through a guest observer program. A Science Definition Team has been established to assist NASA in the development of a Design Reference Mission that accomplishes this diverse array of science programs with a single observatory. In this paper we present the current WFIRST payload concept and the expected capabilities for planet detection. The observatory. with science goals that are complimentary to the Kepler exoplanet transit mission, is designed to complete the statistical census of planetary systems in the Galaxy, from habitable Earth-mass planets to free floating planets, including analogs to all of the planets in our Solar System except Mercury. The exoplanet microlensing survey will observe for 500 days spanning 5 years. This long temporal baseline will enable the determination of the masses for most detected exoplanets down to 0.1 Earth masses.

  15. Synthesizing exoplanet demographics from radial velocity and microlensing surveys. I. Methodology

    SciTech Connect

    Clanton, Christian; Gaudi, B. Scott

    2014-08-20

    Motivated by the order of magnitude difference in the frequency of giant planets orbiting M dwarfs inferred by microlensing and radial velocity (RV) surveys, we present a method for comparing the statistical constraints on exoplanet demographics inferred from these methods. We first derive the mapping from the observable parameters of a microlensing-detected planet to those of an analogous planet orbiting an RV-monitored star. Using this mapping, we predict the distribution of RV observables for the planet population inferred from microlensing surveys, taking care to adopt reasonable priors for, and properly marginalize over, the unknown physical parameters of microlensing-detected systems. Finally, we use simple estimates of the detection limits for a fiducial RV survey to predict the number and properties of analogs of the microlensing planet population such an RV survey should detect. We find that RV and microlensing surveys have some overlap, specifically for super-Jupiter mass planets (m{sub p} ≳ 1 M {sub Jup}) with periods between ∼3-10 yr. However, the steeply falling planetary mass function inferred from microlensing implies that, in this region of overlap, RV surveys should infer a much smaller frequency than the overall giant planet frequency (m{sub p} ≳ 0.1 M {sub Jup}) inferred by microlensing. Our analysis demonstrates that it is possible to statistically compare and synthesize data sets from multiple exoplanet detection techniques in order to infer exoplanet demographics over wider regions of parameter space than are accessible to individual methods. In a companion paper, we apply our methodology to several representative microlensing and RV surveys to derive the frequency of planets around M dwarfs with orbits of ≲ 30 yr.

  16. Space-based infrared surveys of small bodies

    NASA Astrophysics Data System (ADS)

    Mommert, M.

    2014-07-01

    Most small bodies in the Solar System are too small and too distant to be spatially resolved, precluding a direct diameter derivation. Furthermore, measurements of the optical brightness alone only allow a rough estimate of the diameter, since the surface albedo is usually unknown and can have values between about 3 % and 60 % or more. The degeneracy can be resolved by considering the thermal emission of these objects, which is less prone to albedo effects and mainly a function of the diameter. Hence, the combination of optical and thermal-infrared observational data provides a means to independently derive an object's diameter and albedo. This technique is used in asteroid thermal models or more sophisticated thermophysical models (see, e.g., [1]). Infrared observations require cryogenic detectors and/or telescopes, depending on the actual wavelength range observed. Observations from the ground are additionally compromised by the variable transparency of Earth's atmosphere in major portions of the infrared wavelength ranges. Hence, space-based infrared telescopes, providing stable conditions and significantly better sensitivities than ground-based telescopes, are now used routinely to exploit this wavelength range. Two observation strategies are used with space-based infrared observatories: Space-based Infrared All-Sky Surveys. Asteroid surveys in the thermal infrared are less prone to albedo-related discovery bias compared to surveys with optical telescopes, providing a more complete picture of small body populations. The first space-based infrared survey of Solar System small bodies was performed with the Infrared Astronomical Satellite (IRAS) for 10 months in 1983. In the course of the 'IRAS Minor Planet Survey' [2], 2228 asteroids (3 new discoveries) and more than 25 comets (6 new discoveries) were observed. More recent space-based infrared all-sky asteroid surveys were performed by Akari (launched 2006) and the Wide-field Infrared Survey Explorer (WISE

  17. Microlensing detection of extrasolar planets.

    PubMed

    Giannini, Emanuela; Lunine, Jonathan I

    2013-05-01

    We review the method of exoplanetary microlensing with a focus on two-body planetary lensing systems. The physical properties of planetary systems can be successfully measured by means of a deep analysis of lightcurves and high-resolution imaging of planetary systems, countering the concern that microlensing cannot determine planetary masses and orbital radii. Ground-based observers have had success in diagnosing properties of multi-planet systems from a few events, but space-based observations will be much more powerful and statistically more complete. Since microlensing is most sensitive to exoplanets beyond the snow line, whose statistics, in turn, allow for testing current planetary formation and evolution theories, we investigate the retrieval of semi-major axis density by a microlensing space-based survey with realistic parameters. Making use of a published statistical method for projected exoplanets quantities (Brown 2011), we find that one year of such a survey might distinguish between simple power-law semi-major axis densities. We conclude by briefly reviewing ground-based results hinting at a high abundance of free-floating planets and describing the potential contribution of space-based missions to understanding the frequency and mass distribution of these intriguing objects, which could help unveil the formation processes of planetary systems. PMID:23604071

  18. Preparing for the WFIRST Microlensing Survey: Simulations, Requirements, Survey Strategies, and Precursor Observations

    NASA Astrophysics Data System (ADS)

    Gaudi, Bernard

    As one of the four primary investigations of the Wide Field Infrared Survey Telescope (WFIRST) mission, the microlensing survey will monitor several square degrees of the Galactic bulge for a total of roughly one year. Its primary science goal is to "Complete the statistical census of planetary systems in the Galaxy, from the outer habitable zone to free floating planets, including analogs of all of the planets in our Solar System with the mass of Mars or greater.'' WFIRST will therefore (a) measure the mass function of cold bound planets with masses greater than that of roughly twice the mass of the moon, including providing an estimate of the frequency of sub-Mars-mass embryos, (b) determine the frequency of free-floating planets with masses down to the Earth and below, (c) inform the frequency and habitability of potentially habitable worlds, and (d) revolutionize our understanding of the demographics of cold planets with its exquisite sensitivity to, and large expected yield of, planets in a broad and unexplored region of parameter space. In order for the microlensing survey to be successful, we must develop a plan to go from actual survey observations obtained by the WFIRST telescope and hardware to the final science products. This plan will involve many steps, the development of software, data reduction, and analysis tools at each step, and a list of requirements for each of these components. The overarching goal of this proposal is thus to develop a complete flowdown from the science goals of the microlensing survey to the mission design and hardware components. We have assembled a team of scientists with the breadth of expertise to achieve this primary goal. Our specific subgoals are as follows. Goal 1: We will refine the input Galactic models in order to provide improved microlensing event rates in the WFIRST fields. Goal 2: We will use the improved event rate estimates, along with improvements in our simulation methodology, to provide higher

  19. MOA-2011-BLG-322Lb: a `second generation survey' microlensing planet

    NASA Astrophysics Data System (ADS)

    Shvartzvald, Y.; Maoz, D.; Kaspi, S.; Sumi, T.; Udalski, A.; Gould, A.; Bennett, D. P.; Han, C.; Abe, F.; Bond, I. A.; Botzler, C. S.; Freeman, M.; Fukui, A.; Fukunaga, D.; Itow, Y.; Koshimoto, N.; Ling, C. H.; Masuda, K.; Matsubara, Y.; Muraki, Y.; Namba, S.; Ohnishi, K.; Rattenbury, N. J.; Saito, To.; Sullivan, D. J.; Sweatman, W. L.; Suzuki, D.; Tristram, P. J.; Wada, K.; Yock, P. C. M.; Skowron, J.; Kozłowski, S.; Szymański, M. K.; Kubiak, M.; Pietrzyński, G.; Soszyński, I.; Ulaczyk, K.; Wyrzykowski, Ł.; Poleski, R.; Pietrukowicz, P.

    2014-03-01

    Global `second-generation' microlensing surveys aim to discover and characterize extrasolar planets and their frequency, by means of round-the-clock high-cadence monitoring of a large area of the Galactic bulge, in a controlled experiment. We report the discovery of a giant planet in microlensing event MOA-2011-BLG-322. This moderate-magnification event, which displays a clear anomaly induced by a second lensing mass, was inside the footprint of our second-generation microlensing survey, involving MOA, OGLE and the Wise Observatory. The event was observed by the survey groups, without prompting alerts that could have led to dedicated follow-up observations. Fitting a microlensing model to the data, we find that the time-scale of the event was tE = 23.2 ± 0.8 d, and the mass ratio between the lens star and its companion is q = 0.028 ± 0.001. Finite-source effects are marginally detected, and upper limits on them help break some of the degeneracy in the system parameters. Using a Bayesian analysis that incorporates a Galactic structure model, we estimate the mass of the lens at 0.39^{+0.45}_{-0.19} M_{⊙}, at a distance of 7.56 ± 0.91 kpc. Thus, the companion is likely a planet of mass 11.6^{+13.4}_{-5.6} M_J, at a projected separation of 4.3^{+1.5}_{-1.2} AU, rather far beyond the snow line. This is the first pure-survey planet reported from a second-generation microlensing survey, and shows that survey data alone can be sufficient to characterize a planetary model. With the detection of additional survey-only planets, we will be able to constrain the frequency of extrasolar planets near their systems' snow lines.

  20. Identifying Microlenses In Large, Non-uniformly Sampled Surveys: The Case Of PTF

    NASA Astrophysics Data System (ADS)

    Price-Whelan, Adrian M.; Agúeros, M.; Fournier, A.; Ofek, E.; Street, R.

    2012-05-01

    Many current photometric, time-domain surveys are driven by specific goals, such as supernova searches, transiting exoplanet discoveries, or stellar variability studies, which set the cadence with which individual fields get re-imaged. In the case of the Palomar Transient Factory (PTF), several such sub-surveys are being conducted in parallel, leading to an extremely non-uniform sampling gradient over the survey footprint of nearly 20,000 deg^2: while the typical 7.26 deg^2 PTF field has been imaged 15 times, 1000 deg^2 of the survey has been observed more than 150 times. We use the existing PTF data to study the trade-off between a large survey footprint and irregular sampling when searching for microlensing events, and to examine the probability that such events can be recovered in these data. We conduct Monte Carlo simulations to evaluate our detection efficiency in a hypothetical survey field as a function of both the baseline and number of observations. We also apply variability statistics to systematically differentiate between periodic, transient, and flat light curves. Preliminary results suggest that both recovery and discovery of microlensing events are possible with a careful consideration of photometric systematics. This work can help inform predictions about the observability of microlensing signals in future wide-field time-domain surveys such as that of LSST.

  1. Prospects for Gaia and other space-based surveys .

    NASA Astrophysics Data System (ADS)

    Bailer-Jones, Coryn A. L.

    Gaia is a fully-approved all-sky astrometric and photometric survey due for launch in 2011. It will measure accurate parallaxes and proper motions for everything brighter than G=20 (ca. 109 stars). Its primary objective is to study the composition, origin and evolution of our Galaxy from the 3D structure, 3D velocities, abundances and ages of its stars. In some respects it can be considered as a cosmological survey at redshift zero. Several other upcoming space-based surveys, in particular JWST and Herschel, will study star and galaxy formation in the early (high-redshift) universe. In this paper I briefly describe these missions, as well as SIM and Jasmine, and explain why they need to observe from space. I then discuss some Galactic science contributions of Gaia concerning dark matter, the search for substructure, stellar populations and the mass-luminosity relation. The Gaia data are complex and require the development of novel analysis methods; here I summarize the principle of the astrometric processing. In the last two sections I outline how the Gaia data can be exploited in connection with other observational and theoretical work in order to build up a more comprehensive picture of galactic evolution.

  2. Microlens Masses from Astrometry and Parallax in Space-based Surveys: From Planets to Black Holes

    NASA Astrophysics Data System (ADS)

    Gould, Andrew; Yee, Jennifer C.

    2014-03-01

    We show that space-based microlensing experiments can recover lens masses and distances for a large fraction of all events (those with individual photometric errors <~ 0.01 mag) using a combination of one-dimensional microlens parallaxes and astrometric microlensing. This will provide a powerful probe of the mass distributions of planets, black holes, and neutron stars, the distribution of planets as a function of Galactic environment, and the velocity distributions of black holes and neutron stars. While systematics are in principle a significant concern, we show that it is possible to vet against all systematics (known and unknown) using single-epoch precursor observations with the Hubble Space Telescope roughly 10 years before the space mission.

  3. Microlens masses from astrometry and parallax in space-based surveys: From planets to black holes

    SciTech Connect

    Gould, Andrew; Yee, Jennifer C.

    2014-03-20

    We show that space-based microlensing experiments can recover lens masses and distances for a large fraction of all events (those with individual photometric errors ≲ 0.01 mag) using a combination of one-dimensional microlens parallaxes and astrometric microlensing. This will provide a powerful probe of the mass distributions of planets, black holes, and neutron stars, the distribution of planets as a function of Galactic environment, and the velocity distributions of black holes and neutron stars. While systematics are in principle a significant concern, we show that it is possible to vet against all systematics (known and unknown) using single-epoch precursor observations with the Hubble Space Telescope roughly 10 years before the space mission.

  4. Extinction and the rate of superstring microlensing detection for WFIRST survey of the Bulge

    NASA Astrophysics Data System (ADS)

    Morris, Taylor Andrew; Chernoff, David F.

    2015-01-01

    A network of superstrings produced during the epoch of inflation gives birth to long-lived string loops if, as current observational constraints imply, the string tension G μ/c2 < 10-9. String loops track dark matter when galaxy formation occurs. As part of an ongoing Cornell project we investigate the detection rate of string loop microlensing of stars within the Galaxy and make detailed estimates for the WFIRST survey of the Bulge. In particular, here we compare the rate estimates for different models of J-band extinction. Most of the stars microlensed by strings reside near the Galactic center and the range of variation in extinction models induces a factor of 5 in the overall rate. While this rate-sensitivity is non-trivial we conclude that the overall microlensing rate is sufficiently large that detecting strings over a tension range 10-14 to 10-10 is feasible. For a well-defined model of the string loop population, stellar blending and our effective magnitude cutoff in the WFIRST survey currently dominate our rate uncertainties. For example, detection rates at S/N=102 (cutoff of 23) are about an order of magnitude less than rates at marginal S/N (cutoff of 27). Future work will explore the effective cutoff and the resultant rates.

  5. A GRAPHICS PROCESSING UNIT-ENABLED, HIGH-RESOLUTION COSMOLOGICAL MICROLENSING PARAMETER SURVEY

    SciTech Connect

    Bate, N. F.; Fluke, C. J.

    2012-01-10

    In the era of synoptic surveys, the number of known gravitationally lensed quasars is set to increase by over an order of magnitude. These new discoveries will enable a move from single-quasar studies to investigations of statistical samples, presenting new opportunities to test theoretical models for the structure of quasar accretion disks and broad emission line regions (BELRs). As one crucial step in preparing for this influx of new lensed systems, a large-scale exploration of microlensing convergence-shear parameter space is warranted, requiring the computation of O(10{sup 5}) high-resolution magnification maps. Based on properties of known lensed quasars, and expectations from accretion disk/BELR modeling, we identify regions of convergence-shear parameter space, map sizes, smooth matter fractions, and pixel resolutions that should be covered. We describe how the computationally time-consuming task of producing {approx}290,000 magnification maps with sufficient resolution (10,000{sup 2} pixel map{sup -1}) to probe scales from the inner edge of the accretion disk to the BELR can be achieved in {approx}400 days on a 100 teraflop s{sup -1} high-performance computing facility, where the processing performance is achieved with graphics processing units. We illustrate a use-case for the parameter survey by investigating the effects of varying the lens macro-model on accretion disk constraints in the lensed quasar Q2237+0305. We find that although all constraints are consistent within their current error bars, models with more densely packed microlenses tend to predict shallower accretion disk radial temperature profiles. With a large parameter survey such as the one described here, such systematics on microlensing measurements could be fully explored.

  6. K2 Microlensing and Campaign 9

    NASA Astrophysics Data System (ADS)

    Penny, Matthew

    2016-06-01

    Campaign 9 of K2 will observe a contiguous 3.7 deg^2 region of the Galactic bulge in order to search for microlensing events and measure microlens parallaxes. It will also perform targeted follow-up of approximately 50 microlensing events spread throughout the Kepler focal plane. Parallax measurements are a critical ingredient for measurements of both the lens mass and distance, which contribute to our understanding of the formation of cold exoplanets, and the formation of planets as a function of Galactic environment. Additionally, as the first un-targeted, space-based microlensing survey, K2C9 offers us the first chance to measure the masses and kinematics of a large population of free-floating planet candidates, whose large abundance has been a puzzle since their discovery.I will review the scientific goals of the K2C9 survey, which will be well underway, and report on the ongoing activity of the K2 Campaign 9 Microlensing Science Team and the wider microlensing community, with a focus on the progress that has been made towards analyzing K2 data in crowded fields.

  7. Criteria for Sample Selection to Maximize Planet Sensitivity and Yield from Space-Based Microlens Parallax Surveys

    NASA Astrophysics Data System (ADS)

    Yee, Jennifer C.; Gould, Andrew; Beichman, Charles; Calchi Novati, Sebastiano; Carey, Sean; Gaudi, B. Scott; Henderson, Calen B.; Nataf, David; Penny, Matthew; Shvartzvald, Yossi; Zhu, Wei

    2015-09-01

    Space-based microlens parallax measurements are a powerful tool for understanding planet populations, especially their distribution throughout the Galaxy. However, if space-based observations of the microlensing events must be specifically targeted, it is crucial that microlensing events enter the parallax sample without reference to the known presence or absence of planets. Hence, it is vital to define objective criteria for selecting events where possible and to carefully consider and minimize the selection biases where not possible so that the final sample represents a controlled experiment. We present objective criteria for initiating observations and determining their cadence for a subset of events, and we define procedures for isolating subjective decision making from information about detected planets for the remainder of events. We also define procedures to resolve conflicts between subjective and objective selections. These procedures maximize the planet sensitivity of the sample as a whole by allowing for planet detections even if they occur before satellite observations for objectively selected events and by helping to trigger fruitful follow-up observations for subjectively chosen events. This paper represents our public commitment to these procedures, which is a necessary component of enforcing objectivity on the experimental protocol. They will be implemented for the 2015 Spitzer microlensing campaign.

  8. Microlensing Optical Depth towards the Galactic Bulge Using Clump Giants from the MACHO Survey

    SciTech Connect

    Popowski, P; Griest, K; Thomas, C L; Cook, K H; Bennett, D P; Becker, A C; Alves, D R; Minniti, D; Drake, A J; Alcock, C; Allsman, R A; Axelrod, T S; Freeman, K C; Geha, M; Lehner, M J; Marshall, S L; Nelson, C A; Peterson, B A; Quinn, P J; Stubbs, C W; Sutherland, W; Vandehei, T; Welch, D

    2005-07-14

    Using 7 years of MACHO survey data, we present a new determination of the optical depth to microlensing towards the Galactic bulge. We select the sample of 62 microlensing events (60 unique) on clump giant sources and perform a detailed efficiency analysis. We use only the clump giant sources because these are bright bulge stars and are not as strongly affected by blending as other events. Using a subsample of 42 clump events concentrated in an area of 4.5 deg{sup 2} with 739000 clump giant stars, we find {tau} = 2.17{sub -0.38}{sup +0.47} x 10{sup -6} at (l,b) = (1{sup o}.50, -2{sup o}.68), somewhat smaller than found in most previous MACHO studies, but in excellent agreement with recent theoretical predictions. We also present the optical depth in each of the 19 fields in which we detected events, and find limits on optical depth for fields with no events. The errors in optical depth in individual fields are dominated by Poisson noise. We measure optical depth gradients of (1.06 {+-} 0.71) x 10{sup -6}deg{sup -1} and (0.29 {+-} 0.43) x 10{sup -6}deg{sup -1} in the galactic latitude b and longitude l directions, respectively. Finally, we discuss the possibility of anomalous duration distribution of events in the field 104 centered on (l,b) = (3{sup o}.11, -3{sup o}.01) as well as investigate spatial clustering of events in all fields.

  9. Statistical searches for microlensing events in large, non-uniformly sampled time-domain surveys: A test using palomar transient factory data

    SciTech Connect

    Price-Whelan, Adrian M.; Agüeros, Marcel A.; Fournier, Amanda P.; Street, Rachel; Ofek, Eran O.; Covey, Kevin R.; Levitan, David; Sesar, Branimir; Laher, Russ R.; Surace, Jason

    2014-01-20

    Many photometric time-domain surveys are driven by specific goals, such as searches for supernovae or transiting exoplanets, which set the cadence with which fields are re-imaged. In the case of the Palomar Transient Factory (PTF), several sub-surveys are conducted in parallel, leading to non-uniform sampling over its ∼20,000 deg{sup 2} footprint. While the median 7.26 deg{sup 2} PTF field has been imaged ∼40 times in the R band, ∼2300 deg{sup 2} have been observed >100 times. We use PTF data to study the trade off between searching for microlensing events in a survey whose footprint is much larger than that of typical microlensing searches, but with far-from-optimal time sampling. To examine the probability that microlensing events can be recovered in these data, we test statistics used on uniformly sampled data to identify variables and transients. We find that the von Neumann ratio performs best for identifying simulated microlensing events in our data. We develop a selection method using this statistic and apply it to data from fields with >10 R-band observations, 1.1 × 10{sup 9} light curves, uncovering three candidate microlensing events. We lack simultaneous, multi-color photometry to confirm these as microlensing events. However, their number is consistent with predictions for the event rate in the PTF footprint over the survey's three years of operations, as estimated from near-field microlensing models. This work can help constrain all-sky event rate predictions and tests microlensing signal recovery in large data sets, which will be useful to future time-domain surveys, such as that planned with the Large Synoptic Survey Telescope.

  10. Microlensing Planets

    NASA Astrophysics Data System (ADS)

    Gould, Andrew

    The theory and practice of microlensing planet searches is developed in a systematic way, from an elementary treatment of the deflection of light by a massive body to a thorough discussion of the most recent results. The main concepts of planetary microlensing, including microlensing events, finite-source effects, and microlens parallax, are first introduced within the simpler context of point-lens events. These ideas are then applied to binary (and hence planetary) lenses and are integrated with concepts specific to binaries, including caustic topologies, orbital motion, and degeneracies, with an emphasis on analytic understanding. The most important results from microlensing planet searches are then reviewed, with emphasis both on understanding the historical process of discovery and the means by which scientific conclusions were drawn from light-curve analysis. Finally, the future prospects of microlensing planets searches are critically evaluated. Citations to original works provide the reader with multiple entry points into the literature.

  11. Optimal survey strategies and predicted planet yields for the Korean microlensing telescope network

    SciTech Connect

    Henderson, Calen B.; Gaudi, B. Scott; Skowron, Jan; Penny, Matthew T.; Gould, Andrew P.; Han, Cheongho; Nataf, David

    2014-10-10

    The Korean Microlensing Telescope Network (KMTNet) will consist of three 1.6 m telescopes each with a 4 deg{sup 2} field of view (FoV) and will be dedicated to monitoring the Galactic Bulge to detect exoplanets via gravitational microlensing. KMTNet's combination of aperture size, FoV, cadence, and longitudinal coverage will provide a unique opportunity to probe exoplanet demographics in an unbiased way. Here we present simulations that optimize the observing strategy for and predict the planetary yields of KMTNet. We find preferences for four target fields located in the central Bulge and an exposure time of t {sub exp} = 120 s, leading to the detection of ∼2200 microlensing events per year. We estimate the planet detection rates for planets with mass and separation across the ranges 0.1 ≤ M{sub p} /M {sub ⊕} ≤ 1000 and 0.4 ≤ a/AU ≤ 16, respectively. Normalizing these rates to the cool-planet mass function of Cassan et al., we predict KMTNet will be approximately uniformly sensitive to planets with mass 5 ≤ M{sub p} /M {sub ⊕} ≤ 1000 and will detect ∼20 planets per year per dex in mass across that range. For lower-mass planets with mass 0.1 ≤ M{sub p} /M {sub ⊕} < 5, we predict KMTNet will detect ∼10 planets per year. We also compute the yields KMTNet will obtain for free-floating planets (FFPs) and predict KMTNet will detect ∼1 Earth-mass FFP per year, assuming an underlying population of one such planet per star in the Galaxy. Lastly, we investigate the dependence of these detection rates on the number of observatories, the photometric precision limit, and optimistic assumptions regarding seeing, throughput, and flux measurement uncertainties.

  12. Synthesizing exoplanet demographics from radial velocity and microlensing surveys. II. The frequency of planets orbiting M dwarfs

    SciTech Connect

    Clanton, Christian; Gaudi, B. Scott

    2014-08-20

    In contrast to radial velocity (RV) surveys, results from microlensing surveys indicate that giant planets with masses greater than the critical mass for core accretion (∼0.1 M {sub Jup}) are relatively common around low-mass stars. Using the methodology developed in the first paper, we predict the sensitivity of M-dwarf RV surveys to analogs of the population of planets inferred by microlensing. We find that RV surveys should detect a handful of super-Jovian (>M {sub Jup}) planets at the longest periods being probed. These planets are indeed found by RV surveys, implying that the demographic constraints inferred from these two methods are consistent. Finally, we combine the results from both methods to estimate planet frequencies spanning wide regions of parameter space. We find that the frequency of Jupiters and super-Jupiters (1 ≲ m{sub p} sin i/M {sub Jup} ≲ 13) with periods 1 ≤ P/days ≤ 10{sup 4} is f{sub J}=0.029{sub −0.015}{sup +0.013}, a median factor of 4.3 (1.5-14 at 95% confidence) smaller than the inferred frequency of such planets around FGK stars of 0.11 ± 0.02. However, we find the frequency of all giant planets with 30 ≲ m{sub p} sin i/M {sub ⊕} ≲ 10{sup 4} and 1 ≤ P/days ≤ 10{sup 4} to be f{sub G}=0.15{sub −0.07}{sup +0.06}, only a median factor of 2.2 (0.73-5.9 at 95% confidence) smaller than the inferred frequency of such planets orbiting FGK stars of 0.31 ± 0.07. For a more conservative definition of giant planets (50 ≲ m{sub p} sin i/M {sub ⊕} ≲ 10{sup 4}), we find f{sub G{sup ′}}=0.11±0.05, a median factor of 2.2 (0.73-6.7 at 95% confidence) smaller than that inferred for FGK stars of 0.25 ± 0.05. Finally, we find the frequency of all planets with 1 ≤ m{sub p} sin i/M {sub ⊕} ≤ 10{sup 4} and 1 ≤ P/days ≤ 10{sup 4} to be f{sub p} = 1.9 ± 0.5.

  13. Synthesizing Exoplanet Demographics from Radial Velocity and Microlensing Surveys. II. The Frequency of Planets Orbiting M Dwarfs

    NASA Astrophysics Data System (ADS)

    Clanton, Christian; Gaudi, B. Scott

    2014-08-01

    In contrast to radial velocity (RV) surveys, results from microlensing surveys indicate that giant planets with masses greater than the critical mass for core accretion (~0.1 M Jup) are relatively common around low-mass stars. Using the methodology developed in the first paper, we predict the sensitivity of M-dwarf RV surveys to analogs of the population of planets inferred by microlensing. We find that RV surveys should detect a handful of super-Jovian (>M Jup) planets at the longest periods being probed. These planets are indeed found by RV surveys, implying that the demographic constraints inferred from these two methods are consistent. Finally, we combine the results from both methods to estimate planet frequencies spanning wide regions of parameter space. We find that the frequency of Jupiters and super-Jupiters (1 <~ mp sin i/M Jup <~ 13) with periods 1 <= P/days <= 104 is f_J=0.029^{+0.013}_{-0.015}, a median factor of 4.3 (1.5-14 at 95% confidence) smaller than the inferred frequency of such planets around FGK stars of 0.11 ± 0.02. However, we find the frequency of all giant planets with 30 <~ mp sin i/M ⊕ <~ 104 and 1 <= P/days <= 104 to be f_G=0.15^{+0.06}_{-0.07}, only a median factor of 2.2 (0.73-5.9 at 95% confidence) smaller than the inferred frequency of such planets orbiting FGK stars of 0.31 ± 0.07. For a more conservative definition of giant planets (50 <~ mp sin i/M ⊕ <~ 104), we find f_G^{\\prime }=0.11+/- 0.05, a median factor of 2.2 (0.73-6.7 at 95% confidence) smaller than that inferred for FGK stars of 0.25 ± 0.05. Finally, we find the frequency of all planets with 1 <= mp sin i/M ⊕ <= 104 and 1 <= P/days <= 104 to be fp = 1.9 ± 0.5.

  14. Interferometric observation of microlensing events

    NASA Astrophysics Data System (ADS)

    Cassan, Arnaud; Ranc, Clément

    2016-05-01

    Interferometric observations of microlensing events have the potential to provide unique constraints on the physical properties of the lensing systems. In this work, we first present a formalism that closely combines interferometric and microlensing observable quantities, which lead us to define an original microlensing (u, v) plane. We run simulations of long-baseline interferometric observations and photometric light curves to decide which observational strategy is required to obtain a precise measurement on vector Einstein radius. We finally perform a detailed analysis of the expected number of targets in the light of new microlensing surveys (2011+) which currently deliver 2000 alerts per year. We find that a few events are already at reach of long-baseline interferometers (CHARA, VLTI), and a rate of about six events per year is expected with a limiting magnitude of K ≃ 10. This number would increase by an order of magnitude by raising it to K ≃ 11. We thus expect that a new route for characterizing microlensing events will be opened by the upcoming generations of interferometers.

  15. Rapidly rotating lenses: repeating features in the light curves of short-period binary microlenses

    NASA Astrophysics Data System (ADS)

    Penny, Matthew T.; Kerins, Eamonn; Mao, Shude

    2011-11-01

    Microlensing is most sensitive to binary lenses with relatively large orbital separations, and as such, typical binary microlensing events show little or no orbital motion during the event. However, despite the strength of binary microlensing features falling off rapidly as the lens separation decreases, we show that it is possible to detect repeating features in the light curve of binary microlenses that complete several orbits during the microlensing event. We investigate the light-curve features of such rapidly rotating lens (RRL) events. We derive analytical limits on the range of parameters where these effects are detectable, and confirm these numerically. Using a population synthesis Galactic model, we estimate the RRL event rate for a ground-based and a space-based microlensing survey to be 0.32fb and 7.8fb events per year, respectively, assuming year-round monitoring, where fb is the binary fraction. We detail how RRL event parameters can be quickly estimated from their light curves, and suggest a method to model RRL events using timing measurements of light-curve features. Modelling RRL light curves will yield the lens orbital period and possibly measurements of all orbital elements, including the inclination and eccentricity. Measurement of the period from the light curve allows a mass-distance relation to be defined, which when combined with a measurement of microlens parallax or finite-source effects can yield a mass measurement to a twofold degeneracy. With sub-per cent accuracy photometry, it is possible to detect planetary companions, but the likelihood of this is very small.

  16. Gravitational microlensing I: A unique astrophysical tool

    NASA Astrophysics Data System (ADS)

    Rahvar, Sohrab

    2015-04-01

    In this paper, we review the astrophysical application of gravitational microlensing. After introducing the history of gravitational lensing, we present the key equations and concept of microlensing. The most frequent microlensing events are single-lens events and historically it has been used for searching dark matter in the form of compact astrophysical halo objects in the Galactic halo. We discuss about the degeneracy problem in the parameters of lens and perturbation effects that can partially break the degeneracy between the lens parameters. The rest of paper is about the astrophysical applications of microlensing. One of the important applications is in the stellar physics by probing the surface of source stars in the high magnification microlensing events. The astrometric and polarimetric observations will be complimentary for probing the atmosphere and stellar spots on the surface of source stars. Finally we discuss about the future projects as space-based telescopes for parallax and astrometry observations of microlensing events. With this project, we would expect to produce a complete stellar and remnant mass function and study the structure of Galaxy in term of distribution of stars along our line of sight towards the center of galaxy.

  17. Thermally tunable polymer microlenses

    NASA Astrophysics Data System (ADS)

    Huang, Xian; Cheng, Chao-Min; Wang, Li; Wang, Bin; Su, Chih-Chuan; Ho, Mon-Shu; LeDuc, Philip R.; Lin, Qiao

    2008-06-01

    Polymer microlenses capable of using heat to control its focal length are presented. The microlenses are created by exposing droplets of the polymer SU-8 to UV light. By altering the temperature of the microlenses via on-chip heating, their curvature and focal length are actively controlled without mechanical movements. By directly and indirectly measuring temperature-dependent changes of the focal length, we test the ability of the microlenses as a tunable imaging component. The microlenses have potential use in applications such as laser systems, functional biomimetics, and endoscopy.

  18. Synthesizing Exoplanet Demographics: A Single Population of Long-period Planetary Companions to M Dwarfs Consistent with Microlensing, Radial Velocity, and Direct Imaging Surveys

    NASA Astrophysics Data System (ADS)

    Clanton, Christian; Gaudi, B. Scott

    2016-03-01

    We present the first study to synthesize results from five different exoplanet surveys using three independent detection methods: microlensing, radial velocity, and direct imaging. The constraints derived herein represent the most comprehensive picture of the demographics of large-separation (≳2 AU) planets orbiting the most common stars in our Galaxy that has been constructed to date. We assume a simple, joint power-law planet distribution function of the form {d}2{N}{{pl}}/(d{log} {m}p d{log} a)={ A }{({m}p/{M}{{Sat}})}α {(a/2.5{{AU}})}β with an outer cutoff radius of the separation distribution function of aout. Generating populations of planets from these models and mapping them into the relevant observables for each survey, we use actual or estimated detection sensitivities to determine the expected observations for each survey. Comparing with the reported results, we derive constraints on the parameters \\{α ,β ,{ A },{a}{{out}}\\} that describe a single population of planets that is simultaneously consistent with the results of microlensing, radial velocity, and direct imaging surveys. We find median and 68% confindence intervals of α =-{0.86}-0.19+0.21 (-{0.85}-0.19+0.21), β ={1.1}-1.4+1.9 ({1.1}-1.3+1.9), { A }={0.21}-0.15+0.20 {{dex}}-2 ({0.21}-0.15+0.20 {{dex}}-2), and {a}{{out}}={10}-4.7+26 AU ({12}-6.2+50 AU) assuming “hot-start” (“cold-start”) planet evolutionary models. These values are consistent with all current knowledge of planets on orbits beyond ∼2 AU around single M dwarfs.

  19. Prospects for Gaia and other planned space-based Galactic surveys

    NASA Astrophysics Data System (ADS)

    Bailer-Jones, C. A. L.

    2006-08-01

    Gaia is an all sky astrometric and photometric survey mission which will observe all objects in the sky brighter than magnitude G=20 (V=20-22), some 10^ 9 stars. Gaia will achieve an astrometric accuracy of 12- 25 μas at G=15 (providing a distance accuracy of 1-2% at 1 kpc) and 100-300 μas at G=20 and will measure radial velocities to a precision of 1-10 km/s for brighter sources. To characterize all sources (which are detected in real time), each is observed via low dispersion integral field spectrophotometry. The data processing for Gaia is very complex (self-calibrating; heterogeneous data; little prior information; intrinsically iterative) and is being undertaken by a large consortium of institutes. Fully exploiting the resulting data products will likewise be a challenge: Gaia will be a first in combining photometric and 6D phase space information on such a large scale. The scientific potential is immense. For example, using the kinematics and 3D positions of large numbers of stars across the whole Galaxy we can map its large and small scale structures and thus from a chronology of its formation and evolution (e.g. merger history). Gaia will measure both the gravitational potential of the Galaxy and the stellar luminosity function, from which the distribution of dark matter can be accurately mapped on small scales (< 1 Mpc) for the first time. Accurate distances to thousands of globular and open clusters will significantly improve models of stellar structure and evolution, and the detection of tens of millions of binary systems will permit a calibration of the stellar Mass-Luminosity relation over a wide range of masses and to high accuracy. Gaia is a fully-funded ESA mission due for launch in late 2011. With a nominal mission of five years and 2-3 years planned for post-mission processing, the final catalogue will only be available in about 2020. As it is the only large scale, high-accuracy astrometry mission under construction, it will be a unique source

  20. Minimizing follow-up for space-based transit surveys using full lightcurve analysis

    NASA Astrophysics Data System (ADS)

    Nefs, S. V.; Snellen, I. A. G.; de Mooij, E. J. W.

    2012-07-01

    Context. One of the biggest challenges facing large transit surveys is the elimination of false-positives from the vast number of transit candidates. A large amount of expensive follow-up time is spent on verifying the nature of these systems. Aims: We investigate to what extent information from the lightcurves can identify blend scenarios and eliminate them as planet candidates, to significantly decrease the amount of follow-up observing time required to identify the true exoplanet systems. Methods: If a lightcurve has a sufficiently high signal-to-noise ratio, a distinction can be made between the lightcurve of a stellar binary blended with a third star and the lightcurve of a transiting exoplanet system. We first simulate lightcurves of stellar blends and transiting planet systems to determine what signal-to-noise level is required to make the distinction between blended and non-blended systems as function of transit depth and impact parameter. Subsequently we test our method on real data from the first IRa01 field observed by the CoRoT satellite, concentrating on the 51 candidates already identified by the CoRoT team. Results: Our simulations show that blend scenarios can be constrained for transiting systems at low impact parameters. At high impact parameter, blended and non-blended systems are indistinguishable from each other because they both produce V-shaped transits. About 70% of the planet candidates in the CoRoT IRa01 field are best fit with an impact parameter of b > 0.85, while less than 15% are expected in this range considering random orbital inclinations. By applying a cut at b < 0.85, meaning that ~15% of the potential planet population would be missed, the candidate sample decreases from 41 to 11. The lightcurves of 6 of those are best fit with such low host star densities that the planet-to-star size ratii imply unrealistic planet radii of R > 2 RJup. Two of the five remaining systems, CoRoT1b and CoRoT4b, have been identified as planets by the

  1. Dynamics and Origin of Extra-solar Planetary Systems and Microlensing Detection of Extra-solar Planets

    NASA Technical Reports Server (NTRS)

    Peale, S. J.

    2003-01-01

    We compare a space-based microlensing search for planets, with a ground based microlensing search originally proposed by D. Tytler (Beichman, et al. 1996). Perturbations of microlensing light curves when the lens star has a planetary companion are sought by one wide angle survey telescope and an array of three or four followup narrow angle telescopes distributed in longitude that follow events with high precision, high time resolution photometry. Alternative ground based programs are considered briefly. With the four 2 meter telescopes distributed in longitude in the southern hemisphere in the Tytler proposal, observational constraints on a ground-based search for planets during microlensing events toward the center of the galaxy are severe. Probably less than 100 events could be monitored per year with high precision, high time resolution photometry with only about 42% coverage on the average regardless of how many events were discovered by the survey telescope. Statistics for the occurrence and properties for Jupiter-mass planets would be meaningful but relatively meager four years after the program was started, and meaningful statistics for Earth-mass planets would be non existent. In contrast, the 14,500 events in a proposed 4 year space based program (GEST = Galactic Exoplanet Survey Telescope) would yield very sound statistics on the occurrence, masses and separations of Jupiter-mass planets, and significant constraints on similar properties for Earth-mass planets. The significance of the Jupiter statistics would be to establish the frequency of planetary systems like our own, where terrestrial planets could exist inside the orbits of the giants.

  2. Accurately Mapping M31's Microlensing Population

    NASA Astrophysics Data System (ADS)

    Crotts, Arlin

    2004-07-01

    We propose to augment an existing microlensing survey of M31 with source identifications provided by a modest amount of ACS {and WFPC2 parallel} observations to yield an accurate measurement of the masses responsible for microlensing in M31, and presumably much of its dark matter. The main benefit of these data is the determination of the physical {or "einstein"} timescale of each microlensing event, rather than an effective {"FWHM"} timescale, allowing masses to be determined more than twice as accurately as without HST data. The einstein timescale is the ratio of the lensing cross-sectional radius and relative velocities. Velocities are known from kinematics, and the cross-section is directly proportional to the {unknown} lensing mass. We cannot easily measure these quantities without knowing the amplification, hence the baseline magnitude, which requires the resolution of HST to find the source star. This makes a crucial difference because M31 lens m ass determinations can be more accurate than those towards the Magellanic Clouds through our Galaxy's halo {for the same number of microlensing events} due to the better constrained geometry in the M31 microlensing situation. Furthermore, our larger survey, just completed, should yield at least 100 M31 microlensing events, more than any Magellanic survey. A small amount of ACS+WFPC2 imaging will deliver the potential of this large database {about 350 nights}. For the whole survey {and a delta-function mass distribution} the mass error should approach only about 15%, or about 6% error in slope for a power-law distribution. These results will better allow us to pinpoint the lens halo fraction, and the shape of the halo lens spatial distribution, and allow generalization/comparison of the nature of halo dark matter in spiral galaxies. In addition, we will be able to establish the baseline magnitude for about 50, 000 variable stars, as well as measure an unprecedentedly deta iled color-magnitude diagram and luminosity

  3. The Angstrom Project: a new microlensing candidate

    NASA Astrophysics Data System (ADS)

    Kerins, E.; Darnley, M. J.; Newsam, A. M.; Duke, J. P.; Gould, A.; Street, C. Han B.-G. Park R. A.

    2008-12-01

    We report the discovery of a new microlensing candidate in M31 by the Angstrom Project M31 bulge microlensing survey using the Liverpool Telescope (La Palma). The candidate was discovered using difference imaging techniques by the Angstrom Project Alert System (APAS) in a series of Sloan i'-band images of the bulge of M31.

  4. Evaluating the effect of stellar multiplicity on the point spread function of space-based weak lensing surveys

    NASA Astrophysics Data System (ADS)

    Kuntzer, T.; Courbin, F.; Meylan, G.

    2016-02-01

    The next generation of space-based telescopes used for weak lensing surveys will require exquisite point spread function (PSF) determination. Previously negligible effects may become important in the reconstruction of the PSF, in part because of the improved spatial resolution. In this paper, we show that unresolved multiple star systems can affect the ellipticity and size of the PSF and that this effect is not cancelled even when using many stars in the reconstruction process. We estimate the error in the reconstruction of the PSF due to the binaries in the star sample both analytically and with image simulations for different PSFs and stellar populations. The simulations support our analytical finding that the error on the size of the PSF is a function of the multiple stars distribution and of the intrinsic value of the size of the PSF, i.e. if all stars were single. Similarly, the modification of each of the complex ellipticity components (e1,e2) depends on the distribution of multiple stars and on the intrinsic complex ellipticity. Using image simulations, we also show that the predicted error in the PSF shape is a theoretical limit that can be reached only if large number of stars (up to thousands) are used together to build the PSF at any desired spatial position. For a lower number of stars, the PSF reconstruction is worse. Finally, we compute the effect of binarity for different stellar magnitudes and show that bright stars alter the PSF size and ellipticity more than faint stars. This may affect the design of PSF calibration strategies and the choice of the related calibration fields.

  5. PLANETESIMAL DISK MICROLENSING

    SciTech Connect

    Heng, Kevin; Keeton, Charles R. E-mail: keeton@physics.rutgers.ed

    2009-12-10

    Motivated by debris disk studies, we investigate the gravitational microlensing of background starlight by a planetesimal disk around a foreground star. We use dynamical survival models to construct a plausible example of a planetesimal disk and study its microlensing properties using established ideas of microlensing by small bodies. When a solar-type source star passes behind a planetesimal disk, the microlensing light curve may exhibit short-term, low-amplitude residuals caused by planetesimals several orders of magnitude below Earth mass. The minimum planetesimal mass probed depends on the photometric sensitivity and the size of the source star, and is lower when the planetesimal lens is located closer to us. Planetesimal lenses may be found more nearby than stellar lenses because the steepness of the planetesimal mass distribution changes how the microlensing signal depends on the lens/source distance ratio. Microlensing searches for planetesimals require essentially continuous monitoring programs that are already feasible and can potentially set constraints on models of debris disks, the progeny of the supposed extrasolar analogues of Kuiper Belts.

  6. Detection of planets in extremely weak central perturbation microlensing events via next-generation ground-based surveys

    SciTech Connect

    Chung, Sun-Ju; Lee, Chung-Uk; Koo, Jae-Rim E-mail: leecu@kasi.re.kr

    2014-04-20

    Even though the recently discovered high-magnification event MOA-2010-BLG-311 had complete coverage over its peak, confident planet detection did not happen due to extremely weak central perturbations (EWCPs, fractional deviations of ≲ 2%). For confident detection of planets in EWCP events, it is necessary to have both high cadence monitoring and high photometric accuracy better than those of current follow-up observation systems. The next-generation ground-based observation project, Korea Microlensing Telescope Network (KMTNet), satisfies these conditions. We estimate the probability of occurrence of EWCP events with fractional deviations of ≤2% in high-magnification events and the efficiency of detecting planets in the EWCP events using the KMTNet. From this study, we find that the EWCP events occur with a frequency of >50% in the case of ≲ 100 M {sub E} planets with separations of 0.2 AU ≲ d ≲ 20 AU. We find that for main-sequence and sub-giant source stars, ≳ 1 M {sub E} planets in EWCP events with deviations ≤2% can be detected with frequency >50% in a certain range that changes with the planet mass. However, it is difficult to detect planets in EWCP events of bright stars like giant stars because it is easy for KMTNet to be saturated around the peak of the events because of its constant exposure time. EWCP events are caused by close, intermediate, and wide planetary systems with low-mass planets and close and wide planetary systems with massive planets. Therefore, we expect that a much greater variety of planetary systems than those already detected, which are mostly intermediate planetary systems, regardless of the planet mass, will be significantly detected in the near future.

  7. Astrometric microlensing with the GAIA satellite

    NASA Astrophysics Data System (ADS)

    Belokurov, V. A.; Evans, N. W.

    2002-04-01

    GAIA is the `super-Hipparcos ' survey satellite selected as a Cornerstone 6 mission by the European Space Agency. GAIA can measure microlensing by the brightening of source stars. For the broad G -band photometer, the all-sky source-averaged photometric optical depth is ~10-7 . There are ~1300 photometric microlensing events for which GAIA will measure at least one data point on the amplified light curve. GAIA can also measure microlensing by the small excursions of the light centroid that occur during events. The all-sky source-averaged astrometric microlensing optical depth is ~2.5×10-5 . Some ~25000 sources will have a significant variation of the centroid shift, together with a closest approach, during the lifetime of the mission. This is not the actual number of events that can be extracted from the GAIA data set, as the false detection rate has not been assessed. A covariance analysis is used to study the propagation of errors and the estimation of parameters from realistic sampling of the GAIA data stream of transits in the along-scan direction during microlensing events. The mass of the lens can be calculated to good accuracy if the lens is nearby so that the angular Einstein radius θ E is large; if the Einstein radius projected on to the observer plane r~ E is approximately an astronomical unit; or if the duration of the astrometric event is long (>~1yr) or the source star is bright . Monte Carlo simulations are used to study the ~2500 events for which the mass can be recovered with an error of <50 per cent. These high-quality events are dominated by disc lenses within a few tens of parsecs and source stars within a few hundred parsecs. We show that the local mass function can be recovered from the high-quality sample to good accuracy. GAIA is the first instrument with the capability of measuring the mass locally in very faint objects such as black holes and very cool white and brown dwarfs. For only ~5 per cent of all astrometric events will GAIA record

  8. Gravitational Microlensing Events as a Target for the SETI project

    NASA Astrophysics Data System (ADS)

    Rahvar, Sohrab

    2016-09-01

    The detection of signals from a possible extrasolar technological civilization is one of the most challenging efforts of science. In this work, we propose using natural telescopes made of single or binary gravitational lensing systems to magnify leakage of electromagnetic signals from a remote planet that harbors Extraterrestrial Intelligent (ETI) technology. Currently, gravitational microlensing surveys are monitoring a large area of the Galactic bulge to search for microlensing events, finding more than 2000 events per year. These lenses are capable of playing the role of natural telescopes, and, in some instances, they can magnify radio band signals from planets orbiting around the source stars in gravitational microlensing systems. Assuming that the frequency of electromagnetic waves used for telecommunication in ETIs is similar to ours, we propose follow-up observation of microlensing events with radio telescopes such as the Square Kilometre Array (SKA), the Low Frequency Demonstrators, and the Mileura Wide-Field Array. Amplifying signals from the leakage of broadcasting by an Earth-like civilization will allow us to detect them as far as the center of the Milky Way galaxy. Our analysis shows that in binary microlensing systems, the probability of amplification of signals from ETIs is more than that in single microlensing events. Finally, we propose the use of the target of opportunity mode for follow-up observations of binary microlensing events with SKA as a new observational program for searching ETIs. Using optimistic values for the factors of the Drake equation provides detection of about one event per year.

  9. Theory of dispersive microlenses

    NASA Technical Reports Server (NTRS)

    Herman, B.; Gal, George

    1993-01-01

    A dispersive microlens is a miniature optical element which simultaneously focuses and disperses light. Arrays of dispersive mircolenses have potential applications in multicolor focal planes. They have a 100 percent optical fill factor and can focus light down to detectors of diffraction spot size, freeing up areas on the focal plane for on-chip analog signal processing. Use of dispersive microlenses allows inband color separation within a pixel and perfect scene registration. A dual-color separation has the potential for temperature discrimination. We discuss the design of dispersive microlenses and present sample results for efficient designs.

  10. Microlensing Signature of Binary Black Holes

    NASA Technical Reports Server (NTRS)

    Schnittman, Jeremy; Sahu, Kailash; Littenberg, Tyson

    2012-01-01

    We calculate the light curves of galactic bulge stars magnified via microlensing by stellar-mass binary black holes along the line-of-sight. We show the sensitivity to measuring various lens parameters for a range of survey cadences and photometric precision. Using public data from the OGLE collaboration, we identify two candidates for massive binary systems, and discuss implications for theories of star formation and binary evolution.

  11. A study of the performance of the transit detection tool DST in space-based surveys. Application of the CoRoT pipeline to Kepler data

    NASA Astrophysics Data System (ADS)

    Cabrera, J.; Csizmadia, Sz.; Erikson, A.; Rauer, H.; Kirste, S.

    2012-12-01

    Context. Transit detection algorithms are mathematical tools used for detecting planets in the photometric data of transit surveys. In this work we study their application to space-based surveys. Aims: Space missions are exploring the parameter space of the transit surveys where classical algorithms do not perform optimally, either because of the challenging signal-to-noise ratio of the signal or its non-periodic characteristics. We have developed an algorithm addressing these challenges for the mission CoRoT. Here we extend the application to the data from the space mission Kepler. We aim at understanding the performances of algorithms in different data sets. Methods: We built a simple analytical model of the transit signal and developed a strategy for the search that improves the detection performance for transiting planets. We analyzed Kepler data with a set of stellar activity filtering and transit detection tools from the CoRoT community that are designed for the search of transiting planets. Results: We present a new algorithm and its performances compared to one of the most widely used techniques in the literature using CoRoT data. Additionally, we analyzed Kepler data corresponding to quarter Q1 and compare our results with the most recent list of planetary candidates from the Kepler survey. We found candidates that went unnoticed by the Kepler team when analyzing longer data sets. We study the impact of instrumental features on the production of false alarms and false positives. These results show that the analysis of space mission data advocates the use of complementary detrending and transit detection tools also for future space-based transit surveys such as PLATO.

  12. Difference Image Analysis of Galactic Microlensing. II. Microlensing Events

    SciTech Connect

    Alcock, C.; Allsman, R. A.; Alves, D.; Axelrod, T. S.; Becker, A. C.; Bennett, D. P.; Cook, K. H.; Drake, A. J.; Freeman, K. C.; Griest, K.

    1999-09-01

    The MACHO collaboration has been carrying out difference image analysis (DIA) since 1996 with the aim of increasing the sensitivity to the detection of gravitational microlensing. This is a preliminary report on the application of DIA to galactic bulge images in one field. We show how the DIA technique significantly increases the number of detected lensing events, by removing the positional dependence of traditional photometry schemes and lowering the microlensing event detection threshold. This technique, unlike PSF photometry, gives the unblended colors and positions of the microlensing source stars. We present a set of criteria for selecting microlensing events from objects discovered with this technique. The 16 pixel and classical microlensing events discovered with the DIA technique are presented. (c) (c) 1999. The American Astronomical Society.

  13. Astrophysical applications of gravitational microlensing

    NASA Astrophysics Data System (ADS)

    Dong, Subo

    The first few topics are on searching and characterizing extrasolar planets by means of high-magnification microlensing events. The detection efficiency analysis of the A max ~ 3000 event OGLE-2004-BLG-343 is presented. Due to human error, intensive monitoring did not begin until 43 minutes after peak, at which point the magnification had fallen to A ~ 1200. It is shown that, had a similar event been well sampled over the peak, it would have been sensitive to almost all Neptune-mass planets over a factor of 5 in projected separation and even would have had some sensitivity to Earth-mass planets. New algorithms optimized for fast evaluation of binary-lens models with finite-sources effects have been developed. These algorithms have enabled efficient and thorough parameter-space searches in modeling planetary high- magnification events. The detection of the cool, Jovian-mass planet MOA-2007- BLG-400Lb, discovered from an A max = 628 event with severe finite-source effects, is reported. Detailed analysis yields a fairly precise planet/star mass ratio of q = ([Special characters omitted.] ) × 10^-3 , while the planet/ star projected separation is subject to a strong close/wide degeneracy. Photometric and astrometric measurements from Hubble Space Telescope, as well as constraints from higher order effects extracted from the ground-based light curve (microlens parallax, planetary orbital motion and finite-source effects) are used to constrain the nature of planetary event OGLE-2005-BLG-071Lb. Our primary analysis leads to the conclusion that the host is an M = 0.46 ± 0.04 [Special characters omitted.] M dwarf and that the planet has mass M p = 3.8 ± 0.4 M Jupiter , which is likely to be the most massive planet yet discovered that is hosted by an M dwarf. Next a spaced-based microlens parallax is determined for the first time using Spitzer and ground-based observations for binary-lens event OGLE-2005-SMC-001. The parallax measurement yields a projected velocity v

  14. A Space-Based Near-Earth Object Survey Telescope in Support of Human Exploration, Solar System Science, and Planetary Defense

    NASA Technical Reports Server (NTRS)

    Abell, Paul A.

    2011-01-01

    Human exploration of near-Earth objects (NEOs) beginning in 2025 is one of the stated objectives of U.S. National Space Policy. Piloted missions to these bodies would further development of deep space mission systems and technologies, obtain better understanding of the origin and evolution of our Solar System, and support research for asteroid deflection and hazard mitigation strategies. As such, mission concepts have received much interest from the exploration, science, and planetary defense communities. One particular system that has been suggested by all three of these communities is a space-based NEO survey telescope. Such an asset is crucial for enabling affordable human missions to NEOs circa 2025 and learning about the primordial population of objects that could present a hazard to the Earth in the future.

  15. A new parameter space study of cosmological microlensing

    NASA Astrophysics Data System (ADS)

    Vernardos, G.; Fluke, C. J.

    2013-09-01

    Cosmological gravitational microlensing is a useful technique for understanding the structure of the inner parts of a quasar, especially the accretion disc and the central supermassive black hole. So far, most of the cosmological microlensing studies have focused on single objects from ˜90 currently known lensed quasars. However, present and planned all-sky surveys are expected to discover thousands of new lensed systems. Using a graphics processing unit (GPU) accelerated ray-shooting code, we have generated 2550 magnification maps uniformly across the convergence (κ) and shear (γ) parameter space of interest to microlensing. We examine the effect of random realizations of the microlens positions on map properties such as the magnification probability distribution (MPD). It is shown that for most of the parameter space a single map is representative of an average behaviour. All of the simulations have been carried out on the GPU Supercomputer for Theoretical Astrophysics Research.

  16. The MACHO Project HST Follow-Up: The Large Magellanic Cloud Microlensing Source Stars

    SciTech Connect

    Nelson, C.A.; Drake, A.J.; Cook, K.H.; Bennett, D.P.; Popowski, P.; Dalal, N.; Nikolaev, S.; Alcock, C.; Axelrod, T.S.; Becker, A.C. Freeman, K.C.; Geha, M.; Griest, K.; Keller, S.C.; Lehner, M.J.; Marshall, S.L.; Minniti, D.; Pratt, M.R.; Quinn, P.J.; Stubbs, C.W.; Sutherland, W.; /Oxford U. /Oran, Sci. Tech. U. /Garching, Max Planck Inst. /McMaster U.

    2009-06-25

    We present Hubble Space Telescope (HST) WFPC2 photometry of 13 microlensed source stars from the 5.7 year Large Magellanic Cloud (LMC) survey conducted by the MACHO Project. The microlensing source stars are identified by deriving accurate centroids in the ground-based MACHO images using difference image analysis (DIA) and then transforming the DIA coordinates to the HST frame. None of these sources is coincident with a background galaxy, which rules out the possibility that the MACHO LMC microlensing sample is contaminated with misidentified supernovae or AGN in galaxies behind the LMC. This supports the conclusion that the MACHO LMC microlensing sample has only a small amount of contamination due to non-microlensing forms of variability. We compare the WFPC2 source star magnitudes with the lensed flux predictions derived from microlensing fits to the light curve data. In most cases the source star brightness is accurately predicted. Finally, we develop a statistic which constrains the location of the Large Magellanic Cloud (LMC) microlensing source stars with respect to the distributions of stars and dust in the LMC and compare this to the predictions of various models of LMC microlensing. This test excludes at {approx}> 90% confidence level models where more than 80% of the source stars lie behind the LMC. Exotic models that attempt to explain the excess LMC microlensing optical depth seen by MACHO with a population of background sources are disfavored or excluded by this test. Models in which most of the lenses reside in a halo or spheroid distribution associated with either the Milky Way or the LMC are consistent which these data, but LMC halo or spheroid models are favored by the combined MACHO and EROS microlensing results.

  17. Kicked Neutron Stars and Microlensing

    NASA Astrophysics Data System (ADS)

    Mollerach, Silvia; Roulet, Esteban

    1997-04-01

    Because of the large kick velocities with which neutron stars are born in supernova explosions, their spatial distribution is more extended than that of their progenitor stars. The large scale height of the neutron stars above the disk plane makes them potential candidates for microlensing of stars in the Large Magellanic Cloud. Adopting for the distribution of kicks the measured velocities of young pulsars, we obtain a microlensing optical depth of τ ~ 2N10 × 10-8 (where N10 is the total number of neutron stars born in the disk in units of 1010). The event duration distribution has the interesting property of being peaked at T ~ 60-80 days, but for the rates to be relevant for the present microlensing searches, it would require N10 >~ 1, a value larger than the usually adopted ones (N10 ~ 0.1-0.2).

  18. Liquid Tunable Microlenses based on MEMS techniques

    PubMed Central

    Zeng, Xuefeng; Jiang, Hongrui

    2013-01-01

    The recent rapid development in microlens technology has provided many opportunities for miniaturized optical systems, and has found a wide range of applications. Of these microlenses, tunable-focus microlenses are of special interest as their focal lengths can be tuned using micro-scale actuators integrated with the lens structure. Realization of such tunable microlens generally relies on the microelectromechanical system (MEMS) technologies. Here, we review the recent progress in tunable liquid microlenses. The underlying physics relevant to these microlenses are first discussed, followed by description of three main categories of tunable microlenses involving MEMS techniques, mechanically driven, electrically driven, and those integrated within microfluidic systems. PMID:24163480

  19. Liquid tunable microlenses based on MEMS techniques

    NASA Astrophysics Data System (ADS)

    Zeng, Xuefeng; Jiang, Hongrui

    2013-08-01

    The recent rapid development in microlens technology has provided many opportunities for miniaturized optical systems, and has found a wide range of applications. Of these microlenses, tunable-focus microlenses are of special interest as their focal lengths can be tuned using micro-scale actuators integrated with the lens structure. Realization of such tunable microlens generally relies on the microelectromechanical system (MEMS) technologies. Here, we review the recent progress in tunable liquid microlenses. The underlying physics relevant to these microlenses are first discussed, followed by description of three main categories of tunable microlenses involving MEMS techniques, mechanically driven, electrically driven and those integrated within microfluidic systems.

  20. Microlensing Parallax for Observers in Heliocentric Motion

    NASA Astrophysics Data System (ADS)

    Calchi Novati, S.; Scarpetta, G.

    2016-06-01

    Motivated by the ongoing Spitzer observational campaign, and the forthcoming K2 one, we revisit, working in an heliocentric reference frame, the geometrical foundation for the analysis of the microlensing parallax, as measured with the simultaneous observation of the same microlensing event from two observers with relative distance of order au. For the case of observers at rest, we discuss the well-known fourfold microlensing parallax degeneracy and determine an equation for the degenerate directions of the lens trajectory. For the case of observers in motion, we write down an extension of the Gould relationship between the microlensing parallax and the observable quantities and, at the same time, highlight the functional dependence of these same quantities from the timescale of the underlying microlensing event. Furthermore, through a series of examples, we show the importance of taking into account themotion of the observers to correctly recover the parameters of the underlying microlensing event. In particular, we discuss the cases of the amplitude of the microlensing parallax and that of the difference of the timescales between the observed microlensing events, which are key to understand the breaking of the microlensing parallax degeneracy. Finally, we consider the case of the simultaneous observation of the same microlensing event from the ground and two satellites, a case relevant for the expected joint K2 and Spitzer observational programs in 2016.

  1. The effect of macromodel uncertainties on microlensing modelling of lensed quasars

    NASA Astrophysics Data System (ADS)

    Vernardos, G.; Fluke, C. J.

    2014-12-01

    Cosmological gravitational microlensing has been proven to be a powerful tool to constrain the structure of multiply imaged quasars, especially the accretion disc and central supermassive black hole system. However, the derived constraints on models may be affected by large systematic errors introduced in the various stages of modelling, namely, the macromodels, the microlensing magnification maps, and the convolution with realistic disc profiles. In particular, it has been known that different macromodels of the galaxy lens that fit the observations equally well, can lead to different values of convergence, κ, and shear, γ, required to generate magnification maps. So far, ˜25 microlensed quasars have been studied using microlensing techniques, where each system has been modelled and analysed individually, or in small samples. This is about to change due to the upcoming synoptic all-sky surveys, which are expected to discover thousands of quasars suitable for microlensing studies. In this study, we investigate the connection between macromodels of the galaxy lens and microlensing magnification maps throughout the parameter space in preparation for future studies of large statistical samples of systems displaying microlensing. In particular, we use 55 900 maps produced by the GERLUMPH parameter survey (available online at http://gerlumph.swin.edu.au) and identify regions of parameter space where macromodel uncertainties (Δκ, Δγ) lead to statistically different magnification maps. Strategies for mitigating the effect of Δκ, Δγ uncertainties are discussed in order to understand and control this potential source of systematic errors in accretion disc constraints derived from microlensing.

  2. Microlensing Towards M31: Candidates and Perspectives

    NASA Astrophysics Data System (ADS)

    Calchi Novati, S.

    2004-01-01

    Recent results of the SLOTT-AGAPE and POINT-AGAPE collaborations on a search for microlensing events in direction of the Andromeda galaxy, by using the pixel method, are reported. The detection of 4 microlensing events, some likely to be due to self--lensing, is discussed. One microlensing light curve is shown to be compatible with a binary lens. The present analysis still does not allow us to draw conclusions on the MACHO content of the M31 galaxy.

  3. Microlensing Towards M31:. Candidates and Perspectives

    NASA Astrophysics Data System (ADS)

    Novati, S. Calchi

    Recent results of the SLOTT-AGAPB and POINT-AGAPE collaborations on a search for microlensing events in direction of the Andromeda galaxy, by using the pixel method, are reported. The detection of 4 microlensing events, some likely to be due to self-lensing, is discussed. One microlensing light curve is shown to be compatible with a binary lens. The present analysis still does not allow us to draw conclusions on the MACHO content of the M31 galaxy.

  4. Gravitational microlensing results from MACHO

    SciTech Connect

    Alcock, C.; MACHO Collaboration

    1996-09-01

    The MACHO project is searching for dark qter inthe form of massive compact haio objects (Machos), by monitoring the brightness of millions of stars in the Magellanic Clouds to search for gravitational microlensing events. Analysis of our 1st 2.3 years of data for 8.5 million stars in the LMC yields 8 candidate microlensing events, well in excess of the {approx} 1 event expected from lensing by known low-mass stars. The event timescales range from 34 to 145 days, and the estimated optical depth is N 2x10{sup -7}, about half of that expected from a `standard` halo. Likelihood analysis indicates the typical lens mass is 0.5{sup +0.3}{sub -0.2}M{sub {circle_dot}}, suggesting they may be old white dwarfs.

  5. Quasar microlensing and dark matter

    NASA Technical Reports Server (NTRS)

    Rix, Hans-Walter; Hogan, Craig J.

    1988-01-01

    The amplification of quasar brightness due to gravitational lensing by foreground objects is discussed. It is shown that a recently published sample of X-ray-selected quasars behind foreground galaxies shows a statistically significant brightening compared to a control sample. Correlations with galaxy redshift and impact parameter predicted by microlensing are also demonstrated. A technique is described to measure the mean density of the lenses from a small number of identified cases of microlensing. It is shown that, in this sample, amplification bias is important in determining the mean intensity enhancement and must be included in the density estimate. Assuming that at least two of the four intrinsically brightest quasars behind galaxies are indeed microlensed, the present data yield a formal lower limit on the mean density parameter of lenses Omega(l) greater than 0.25 at 95 percent confidence. These data also imply that a considerable quantity of dark matter exists in macroscopic objects outside the visible parts of galaxies but is still highly correlated with them.

  6. HST imaging of MEGA Microlensing Candidates in M31

    SciTech Connect

    Cseresnjes, Patrick; Crotts, Arlin P.S.; de Jong, Jelte T.A.; Bergier, Alex; Baltz, Edward A.; Gyuk, Geza; Kuijken, Konrad; Widrow, Lawrence M.; /Columbia U., Astron. Astrophys. /Kapteyn Astron. Inst., Groningen /KIPAC, Menlo Park /Chicago U., Astron. Astrophys. Ctr. /Leiden Observ. /Queen's U., Kingston

    2005-07-14

    We investigate HST/ACS and WFPC2 images at the positions of five candidate microlensing events from a large survey of variability in M31 (MEGA). Three closely match unresolved sources, and two produce only flux upper limits. All are confined to regions of the color-magnitude diagram where stellar variability is unlikely to be easily confused with microlensing. Red variable stars cannot explain these events (although background supernova are possible for two). If these lenses arise in M31's halo, they are due to masses 0.08 < m/M{sub {circle_dot}} < 0.85 (95% certainty, for a {delta}-function mass distribution), brown dwarfs for disk/disk, and stellar masses for disk/bulge ''self-lensing''.

  7. Microlensing by Kuiper, Oort, and Free-Floating Planets

    NASA Astrophysics Data System (ADS)

    Gould, Andrew

    2016-08-01

    Microlensing is generally thought to probe planetary systems only out to a few Einstein radii. Microlensing events generated by bound planets beyond about 10 Einstein radii generally do not yield any trace of their hosts, and so would be classified as free floating planets (FFPs). I show that it is already possible, using adaptive optics (AO), to constrain the presence of potential hosts to FFP candidates at separations comparable to the Oort Cloud. With next-generation telescopes, planets at Kuiper-Belt separations can be probed. Next generation telescopes will also permit routine vetting for all FFP candidates, simply by obtaining second epochs 4-8 years after the event.At present, the search for such hosts is restricted to within the ``confusion limit'' of θ_\\confus ˜ 0.25'' but future WFIRST (Wide Field Infrared Survey Telescope) observations will allow one to probe beyond this confusion limit as well.

  8. The frequency of snowline-region planets from four years of OGLE-MOA-Wise second-generation microlensing

    NASA Astrophysics Data System (ADS)

    Shvartzvald, Y.; Maoz, D.; Udalski, A.; Sumi, T.; Friedmann, M.; Kaspi, S.; Poleski, R.; Szymański, M. K.; Skowron, J.; Kozłowski, S.; Wyrzykowski, Ł.; Mróz, P.; Pietrukowicz, P.; Pietrzyński, G.; Soszyński, I.; Ulaczyk, K.; Abe, F.; Barry, R. K.; Bennett, D. P.; Bhattacharya, A.; Bond, I. A.; Freeman, M.; Inayama, K.; Itow, Y.; Koshimoto, N.; Ling, C. H.; Masuda, K.; Fukui, A.; Matsubara, Y.; Muraki, Y.; Ohnishi, K.; Rattenbury, N. J.; Saito, To.; Sullivan, D. J.; Suzuki, D.; Tristram, P. J.; Wakiyama, Y.; Yonehara, A.

    2016-04-01

    We present a statistical analysis of the first four seasons from a `second-generation' microlensing survey for extrasolar planets, consisting of near-continuous time coverage of 8 deg2 of the Galactic bulge by the Optical Gravitational Lens Experiment (OGLE), Microlensing Observations in Astrophysics (MOA), and Wise microlensing surveys. During this period, 224 microlensing events were observed by all three groups. Over 12 per cent of the events showed a deviation from single-lens microlensing, and for ˜one-third of those the anomaly is likely caused by a planetary companion. For each of the 224 events, we have performed numerical ray-tracing simulations to calculate the detection efficiency of possible companions as a function of companion-to-host mass ratio and separation. Accounting for the detection efficiency, we find that 55^{+34}_{-22} per cent of microlensed stars host a snowline planet. Moreover, we find that Neptune-mass planets are ˜10 times more common than Jupiter-mass planets. The companion-to-host mass-ratio distribution shows a deficit at q ˜ 10-2, separating the distribution into two companion populations, analogous to the stellar-companion and planet populations, seen in radial-velocity surveys around solar-like stars. Our survey, however, which probes mainly lower mass stars, suggests a minimum in the distribution in the super-Jupiter mass range, and a relatively high occurrence of brown-dwarf companions.

  9. Space Based Communications

    NASA Technical Reports Server (NTRS)

    Simpson, James; Denson, Erik; Valencia, Lisa; Birr, Richard

    2003-01-01

    Current space lift launches on the Eastern and Western Range require extensive ground-based real-time tracking, communications and command/control systems. These are expensive to maintain and operate and cover only limited geographical areas. Future spaceports will require new technologies to provide greater launch and landing opportunities, support simultaneous missions, and offer enhanced decision support models and simulation capabilities. These ranges must also have lower costs and reduced complexity while continuing to provide unsurpassed safety to the public, flight crew, personnel, vehicles and facilities. Commercial and government space-based assets for tracking and communications offer many attractive possibilities to help achieve these goals. This paper describes two NASA proof-of-concept projects that seek-to exploit the advantages of a space-based range: Iridium Flight Modem and Space-Based Telemetry and Range Safety (STARS). Iridium Flight Modem uses the commercial satellite system Iridium for extremely low cost, low rate two-way communications and has been successfully tested on four aircraft flights. A sister project at Goddard Space Flight Center's (GSFC) Wallops Flight Facility (WFF) using the Globalstar system has been tested on one rocket. The basic Iridium Flight Modem system consists of a L1 carrier Coarse/Acquisition (C/A)-Code Global Positioning System (GPS) receiver, an on-board computer, and a standard commercial satellite modem and antennas. STARS uses the much higher data rate NASA owned Tracking and Data Relay Satellite System (TDRSS), a C/A-Code GPS receiver, an experimental low-power transceiver, custom built command and data handler processor, and digitized flight termination system (FTS) commands. STARS is scheduled to fly on an F-15 at Dryden Flight Research Center in the spring of 2003, with follow-on tests over the next several years.

  10. Space Base One

    NASA Astrophysics Data System (ADS)

    Snead, James M.

    Space Base One (SB1) is a 'good enough' (rather than 'best') performance engineering-oriented, permanently manned space station design employing Space Shuttle External Tank manufacturing capabilities, Space Shuttle-derived launch systems such as the Shuttle-C, and subsystem technologies under development for Space Station Freedom. The structure of SB1 is geometrically simple in arrangement, consisting of paired spokes radiating from a central hub. Attention is given to the assembly sequence for an initial operational capability phase of SB1 development.

  11. The OGLE-III planet detection efficiency from six years of microlensing observations (2003-2008)

    NASA Astrophysics Data System (ADS)

    Tsapras, Y.; Hundertmark, M.; Wyrzykowski, Ł.; Horne, K.; Udalski, A.; Snodgrass, C.; Street, R.; Bramich, D. M.; Dominik, M.; Bozza, V.; Figuera Jaimes, R.; Kains, N.; Skowron, J.; Szymański, M. K.; Pietrzyński, G.; Soszyński, I.; Ulaczyk, K.; Kozłowski, S.; Pietrukowicz, P.; Poleski, R.

    2016-04-01

    We use six years (2003-2008) of Optical Gravitational Lensing Experiment-III microlensing observations to derive the survey detection efficiency for a range of planetary masses and projected distances from the host star. We perform an independent analysis of the microlensing light curves to extract the event parameters and compute the planet detection probability given the data. 2433 light curves satisfy our quality selection criteria and are retained for further processing. The aggregate of the detection probabilities over the range explored yields the expected number of microlensing planet detections. We employ a Galactic model to convert this distribution from dimensionless to physical units, α/au and M⊕. The survey sensitivity to small planets is highest in the range 1-4 au, shifting to slightly larger separations for more massive ones.

  12. GERLUMPH DATA RELEASE 1: HIGH-RESOLUTION COSMOLOGICAL MICROLENSING MAGNIFICATION MAPS AND eResearch TOOLS

    SciTech Connect

    Vernardos, G.; Fluke, C. J.; Croton, D.; Bate, N. F.

    2014-03-01

    As synoptic all-sky surveys begin to discover new multiply lensed quasars, the flow of data will enable statistical cosmological microlensing studies of sufficient size to constrain quasar accretion disk and supermassive black hole properties. In preparation for this new era, we are undertaking the GPU-Enabled, High Resolution cosmological MicroLensing parameter survey (GERLUMPH). We present here the GERLUMPH Data Release 1, which consists of 12,342 high resolution cosmological microlensing magnification maps and provides the first uniform coverage of the convergence, shear, and smooth matter fraction parameter space. We use these maps to perform a comprehensive numerical investigation of the mass-sheet degeneracy, finding excellent agreement with its predictions. We study the effect of smooth matter on microlensing induced magnification fluctuations. In particular, in the minima and saddle-point regions, fluctuations are enhanced only along the critical line, while in the maxima region they are always enhanced for high smooth matter fractions (≈0.9). We describe our approach to data management, including the use of an SQL database with a Web interface for data access and online analysis, obviating the need for individuals to download large volumes of data. In combination with existing observational databases and online applications, the GERLUMPH archive represents a fundamental component of a new microlensing eResearch cloud. Our maps and tools are publicly available at http://gerlumph.swin.edu.au/.

  13. Space-Based Range

    NASA Technical Reports Server (NTRS)

    2008-01-01

    Space-Based Range (SBR), previously known as Space-Based Telemetry and Range Safety (STARS), is a multicenter NASA proof-of-concept project to determine if space-based communications using NASA's Tracking and Data Relay Satellite System (TDRSS) can support the Range Safety functions of acquiring tracking data and generating flight termination signals, while also providing broadband Range User data such as voice, video, and vehicle/payload data. There was a successful test of the Range Safety system at Wallops Flight Facility (WFF) on December 20, 2005, on a two-stage Terrier-Orion spin-stabilized sounding rocket. SBR transmitted GPS tracking data and maintained links with two TDRSS satellites simultaneously during the 10-min flight. The payload section deployed a parachute, landed in the Atlantic Ocean about 90 miles downrange from the launch site, and was successfully recovered. During the Terrier-Orion tests flights, more than 99 percent of all forward commands and more than 95 percent of all return frames were successfully received and processed. The time latency necessary for a command to travel from WFF over landlines to White Sands Complex and then to the vehicle via TDRSS, be processed onboard, and then be sent back to WFF was between 1.0 s and 1.1 s. The forward-link margins for TDRS-10 (TDRS East [TDE]) were 11 dB to 12 dB plus or minus 2 dB, and for TDRS-4 (TDRS Spare [TDS]) were 9 dB to 10 dB plus or minus 1.5 dB. The return-link margins for both TDE and TDS were 6 dB to 8 dB plus or minus 3 dB. There were 11 flights on an F-15B at Dryden Flight Research Center (DFRC) between November 2006 and February 2007. The Range User system tested a 184-element TDRSS Ku-band (15 GHz) phased-array antenna with data rates of 5 Mbps and 10 Mbps. This data was a combination of black-and-white cockpit video, Range Safety tracking and transceiver data, and aircraft and antenna controller data streams. IP data formatting was used.

  14. Eclipsing negative-parity image of gravitational microlensing by a giant-lens star

    NASA Astrophysics Data System (ADS)

    Rahvar, Sohrab

    2016-07-01

    Gravitational microlensing has been used as a powerful tool for astrophysical studies and exoplanet detections. In the gravitational microlensing, we have two images with negative and positive parities. The negative-parity image is a fainter image and is produced at a closer angular separation with respect to the lens star. In the case of a red-giant lens star and large impact parameter of lensing, this image can be eclipsed by the lens star. The result would be dimming the flux receiving from the combination of the source and the lens stars and the light curve resembles to an eclipsing binary system. In this work, we introduce this phenomenon and propose an observational procedure for detecting this eclipse. The follow-up microlensing telescopes with lucky imaging camera or space-based telescopes can produce high-resolution images from the events with reddish sources and confirm the possibility of blending due to the lens star. After conforming a red-giant lens star and source star, we can use the advance photometric methods and detect the relative flux change during the eclipse in the order of 10-4-10-3. Observation of the eclipse provides the angular size of source star in the unit of Einstein angle and combination of this observation with the parallax observation enable us to calculate the mass of lens star. Finally, we analysed seven microlensing event and show the feasibility of observation of this effect in future observations.

  15. The Angstrom Project: M31 microlensing alert ANG-08B-M31-07

    NASA Astrophysics Data System (ADS)

    Darnley, M. J.; Kerins, E.; Newsam, A. M.; Duke, J. P.; Gould, A.; Street, C. Han B.-G. Park R. A.

    2008-12-01

    We report an ongoing microlensing candidate in M31 by the Angstrom Project M31 bulge microlensing survey using the Liverpool Telescope (La Palma). The candidate was detected from difference imaging photometry generated by the Angstrom Project Alert System (APAS) in a series of Sloan i'-band images of the bulge of M31.

  16. SPACE BASED INTERCEPTOR SCALING

    SciTech Connect

    G. CANAVAN

    2001-02-01

    Space Based Interceptor (SBI) have ranges that are adequate to address rogue ICBMs. They are not overly sensitive to 30-60 s delay times. Current technologies would support boost phase intercept with about 150 interceptors. Higher acceleration and velocity could reduce than number by about a factor of 3 at the cost of heavier and more expensive Kinetic Kill Vehicles (KKVs). 6g SBI would reduce optimal constellation costs by about 35%; 8g SBI would reduce them another 20%. Interceptor ranges fall rapidly with theater missile range. Constellations increase significantly for ranges under 3,000 km, even with advanced interceptor technology. For distributed launches, these estimates recover earlier strategic scalings, which demonstrate the improved absentee ratio for larger or multiple launch areas. Constellations increase with the number of missiles and the number of interceptors launched at each. The economic estimates above suggest that two SBI per missile with a modest midcourse underlay is appropriate. The SBI KKV technology would appear to be common for space- and surface-based boost phase systems, and could have synergisms with improved midcourse intercept and discrimination systems. While advanced technology could be helpful in reducing costs, particularly for short range theater missiles, current technology appears adequate for pressing rogue ICBM, accidental, and unauthorized launches.

  17. The advantages of using a Lucky Imaging camera for observations of microlensing events

    NASA Astrophysics Data System (ADS)

    Sajadian, Sedighe; Rahvar, Sohrab; Dominik, Martin; Hundertmark, Markus

    2016-05-01

    In this work, we study the advantages of using a Lucky Imaging camera for the observations of potential planetary microlensing events. Our aim is to reduce the blending effect and enhance exoplanet signals in binary lensing systems composed of an exoplanet and the corresponding parent star. We simulate planetary microlensing light curves based on present microlensing surveys and follow-up telescopes where one of them is equipped with a Lucky Imaging camera. This camera is used at the Danish 1.54-m follow-up telescope. Using a specific observational strategy, for an Earth-mass planet in the resonance regime, where the detection probability in crowded fields is smaller, Lucky Imaging observations improve the detection efficiency which reaches 2 per cent. Given the difficulty of detecting the signal of an Earth-mass planet in crowded-field imaging even in the resonance regime with conventional cameras, we show that Lucky Imaging can substantially improve the detection efficiency.

  18. Microlenses and their applications in endoscopes

    NASA Astrophysics Data System (ADS)

    Zeng, Xuefeng

    Microlenses have been developed in the past and play an important role in many fields, including optical communication, photolithography, imaging systems and lab on chips. Microlenses with fixed focal length and tunable focus have their individual applications. Several methods and mechanisms have been reported to realize microlenses; however, they have their advantages and disadvantages. In this work, two kinds of microlenses are studied: microlens arrays with fixed focal length and liquid tunable-focus microlenses actuated by stimuli-responsive hydrogels. The design, fabrication, testing and applications of these microlenses are explored. The gist of these microlenses is to utilize surface tension of liquid-air and/or immiscible liquid-liquid interfaces because surface tension dominates over gravity at the micro-scale. Microlens arrays with fixed focal length, made of polydimethylsiloxane (PDMS), are fabricated through liquid-phase photopolymerization and molding. Liquid menisci of photopolymerizable solutions at liquid-air interfaces are first formed and cured under ultraviolet (UV) radiance to obtain the mold. The resultant polymerized mold is then transferred to PDMS utilizing two molding steps to form a microlens array. The liquid tunable-focus microlens is formed by a water-oil interface that is pinned at a hydrophobic-hydrophilic boundary at the top edge of an aperture. Multiple hydrogel microstructures, whose volume is responsive to a certain stimuli, are formed around the lens aperture under UV radiance and regulate the pressure across the meniscus of the water-oil interface, varying the focal length of the microlens. The liquid tunable-focus microlenses responsive to infrared (IR) light are integrated at the end of fiber endoscopes and can scan the areas of interest with minimal back-and-forth movements of the scopes themselves. The operation of the microlens and the image acquisition are realized through light transmitted via optical fibers. Benefitting

  19. Influence of chemical processing on the imaging properties of microlenses

    NASA Astrophysics Data System (ADS)

    Vasiljević, Darko; Murić, Branka; Pantelić, Dejan; Panić, Bratimir

    2009-07-01

    Microlenses are produced by irradiation of a layer of tot'hema and eosin sensitized gelatin (TESG) by using a laser beam (Nd:YAG 2nd harmonic; 532 nm). All the microlenses obtained are concave with a parabolic profile. After the production, the microlenses are chemically processed with various concentrations of alum. The following imaging properties of microlenses were calculated and analyzed: the root mean square (rms) wavefront aberration, the geometric encircled energy and the spot diagram. The microlenses with higher concentrations of alum in solution had a greater effective focal length and better image quality. The microlenses chemically processed with 10% alum solution had near-diffraction-limited performance.

  20. Relativity and Exoplanets: Gravitational Microlensing, Doppler Beaming, and More

    NASA Astrophysics Data System (ADS)

    Gaudi, Scott

    2016-03-01

    Perhaps surprisingly, the theories of both special and general relativity play important roles in several areas of exoplanet research. I will review the most important and intriguing of these applications. The most obvious case is gravitational microlensing, which has become a fairly routine method of finding planets, and is poised to become even more important in the next decade. I will also briefly survey the numerous other areas where relativity plays a role in exoplanet theory and observations, including photometric Doppler beaming, general relativistic precession, transits of compact objects, and even (potentially) gravitational wave experiments.

  1. The Angstrom Project: two new microlensing/nova transients

    NASA Astrophysics Data System (ADS)

    Kerins, Eamonn

    2008-11-01

    We report the discovery of two new optical transients in M31 by the Angstrom Project M31 bulge microlensing survey using the Liverpool Telescope (La Palma). These transients were discovered using difference imaging techniques by the Angstrom Project Alert System (APAS) in a series of Sloan i'-band images of the bulge of M31.

  2. Space-based detectors

    NASA Astrophysics Data System (ADS)

    Sesana, A.; Weber, W. J.; Killow, C. J.; Perreur-Lloyd, M.; Robertson, D. I.; Ward, H.; Fitzsimons, E. D.; Bryant, J.; Cruise, A. M.; Dixon, G.; Hoyland, D.; Smith, D.; Bogenstahl, J.; McNamara, P. W.; Gerndt, R.; Flatscher, R.; Hechenblaikner, G.; Hewitson, M.; Gerberding, O.; Barke, S.; Brause, N.; Bykov, I.; Danzmann, K.; Enggaard, A.; Gianolio, A.; Vendt Hansen, T.; Heinzel, G.; Hornstrup, A.; Jennrich, O.; Kullmann, J.; Møller-Pedersen, S.; Rasmussen, T.; Reiche, J.; Sodnik, Z.; Suess, M.; Armano, M.; Sumner, T.; Bender, P. L.; Akutsu, T.; Sathyaprakash, B. S.

    2014-12-01

    The parallel session C5 on Space-Based Detectors gave a broad overview over the planned space missions related to gravitational wave detection. Overviews of the revolutionary science to be expected from LISA was given by Alberto Sesana and Sasha Buchman. The launch of LISA Pathfinder (LPF) is planned for 2015. This mission and its payload "LISA Technology Package" will demonstrate key technologies for LISA. In this context, reference masses in free fall for LISA, and gravitational physics in general, was described by William Weber, laser interferometry at the pico-metre level and the optical bench of LPF was presented by Christian Killow and the performance of the LPF optical metrology system by Paul McNamara. While LPF will not yet be sensitive to gravitational waves, it may nevertheless be used to explore fundamental physics questions, which was discussed by Michele Armano. Some parts of the LISA technology that are not going to be demonstrated by LPF, but under intensive development at the moment, were presented by Oliver Jennrich and Oliver Gerberding. Looking into the future, Japan is studying the design of a mid-frequency detector called DECIGO, which was discussed by Tomotada Akutsu. Using atom interferometry for gravitational wave detection has also been recently proposed, and it was critically reviewed by Peter Bender. In the nearer future, the launch of GRACE Follow-On (for Earth gravity observation) is scheduled for 2017, and it will include a Laser Ranging Interferometer as technology demonstrator. This will be the first inter-spacecraft laser interferometer and has many aspects in common with the LISA long arm, as discussed by Andrew Sutton.

  3. Microlensing by the galactic bar

    NASA Technical Reports Server (NTRS)

    Zhao, Hongsheng; Spergel, David N.; Rich, R. Michael

    1995-01-01

    We compute the optical depth and duration distribution of microlensing events towrd Baade's window in a model composed of a Galactic disk and a bar. The bar model is a self-consistent dynamical model built out of individual orbits that has been populated to be consistent with the COBE maps of the Galaxy and kinematic observations of the Galactic bulge. We find that most of the lenses are in the bulge with a line-of-sight distance 6.25 kpc (adopting R(sub 0) = 8 kpc). The microlensing optical depth of a 2 x 10(exp 10) solar mass bar plus a truncated disk is (2.2 +/- 0.45) x 10(exp -6), consistent with the large optical depth (3.2 +/- 1.2) x 10(exp -6) found by Udalski et al. (1994). This model optical depth is enhanced over the predictions of axisymmetric models by Kiraga & Paczynski (1994) by slightly more than a factor of 2, since the bar is elongated along the line of sight. The large Einstein radius and small transverse velocity dispersion also predict a longer event duration in the self-consistent bar model than in the Kiraga-Paczynski model. The event rate and duration distribution also depend on the lower mass cutoff of the lens mass function. With a 0.1 solar mass cutoff, five to seven events (depending on the contribution of disk lenses) with a logarithmic mean duration of 20 days are expected for the Optical Gravitational Lensing Experiment (OGLE) according to our model, while Udalski et al. (1994) observed nine events with durations from 8 to 62 days. On the other hand, if most of the lenses are brown dwarfs, our model predicts too many short-duration events. A Kolmogorov-Smirnov test finds only 7% probability for the model with 0.01 solar mass cutoff to be consistent with current data.

  4. Stellar Rotation Effects in Polarimetric Microlensing

    NASA Astrophysics Data System (ADS)

    Sajadian, Sedighe

    2016-07-01

    It is well known that the polarization signal in microlensing events of hot stars is larger than that of main-sequence stars. Most hot stars rotate rapidly around their stellar axes. The stellar rotation creates ellipticity and gravity-darkening effects that break the spherical symmetry of the source's shape and the circular symmetry of the source's surface brightness respectively. Hence, it causes a net polarization signal for the source star. This polarization signal should be considered in polarimetric microlensing of fast rotating stars. For moderately rotating stars, lensing can magnify or even characterize small polarization signals due to the stellar rotation through polarimetric observations. The gravity-darkening effect due to a rotating source star creates asymmetric perturbations in polarimetric and photometric microlensing curves whose maximum occurs when the lens trajectory crosses the projected position of the rotation pole on the sky plane. The stellar ellipticity creates a time shift (i) in the position of the second peak of the polarimetric curves in transit microlensing events and (ii) in the peak position of the polarimetric curves with respect to the photometric peak position in bypass microlensing events. By measuring this time shift via polarimetric observations of microlensing events, we can evaluate the ellipticity of the projected source surface on the sky plane. Given the characterizations of the FOcal Reducer and low dispersion Spectrograph (FORS2) polarimeter at the Very Large Telescope, the probability of observing this time shift is very small. The more accurate polarimeters of the next generation may well measure these time shifts and evaluate the ellipticity of microlensing source stars.

  5. Candidate gravitational microlensing events for future direct lens imaging

    SciTech Connect

    Henderson, C. B.; Gould, A.; Gaudi, B. S.; Park, H.; Han, C.; Sumi, T.; Koshimoto, N.; Udalski, A.; Tsapras, Y.; Bozza, V.; Abe, F.; Fukunaga, D.; Itow, Y.; Masuda, K.; Bennett, D. P.; Bond, I. A.; Ling, C. H.; Botzler, C. S.; Freeman, M.; Fukui, A.; Collaboration: MOA Collaboration; OGLE Collaboration; μFUN Collaboration; RoboNet Collaboration; and others

    2014-10-10

    The mass of the lenses giving rise to Galactic microlensing events can be constrained by measuring the relative lens-source proper motion and lens flux. The flux of the lens can be separated from that of the source, companions to the source, and unrelated nearby stars with high-resolution images taken when the lens and source are spatially resolved. For typical ground-based adaptive optics (AO) or space-based observations, this requires either inordinately long time baselines or high relative proper motions. We provide a list of microlensing events toward the Galactic bulge with high relative lens-source proper motion that are therefore good candidates for constraining the lens mass with future high-resolution imaging. We investigate all events from 2004 to 2013 that display detectable finite-source effects, a feature that allows us to measure the proper motion. In total, we present 20 events with μ ≳ 8 mas yr{sup –1}. Of these, 14 were culled from previous analyses while 6 are new, including OGLE-2004-BLG-368, MOA-2005-BLG-36, OGLE-2012-BLG-0211, OGLE-2012-BLG-0456, MOA-2012-BLG-532, and MOA-2013-BLG-029. In ≲12 yr from the time of each event the lens and source of each event will be sufficiently separated for ground-based telescopes with AO systems or space telescopes to resolve each component and further characterize the lens system. Furthermore, for the most recent events, comparison of the lens flux estimates from images taken immediately to those estimated from images taken when the lens and source are resolved can be used to empirically check the robustness of the single-epoch method currently being used to estimate lens masses for many events.

  6. Candidate Gravitational Microlensing Events for Future Direct Lens Imaging

    NASA Astrophysics Data System (ADS)

    Henderson, C. B.; Park, H.; Sumi, T.; Udalski, A.; Gould, A.; Tsapras, Y.; Han, C.; Gaudi, B. S.; Bozza, V.; Abe, F.; Bennett, D. P.; Bond, I. A.; Botzler, C. S.; Freeman, M.; Fukui, A.; Fukunaga, D.; Itow, Y.; Koshimoto, N.; Ling, C. H.; Masuda, K.; Matsubara, Y.; Muraki, Y.; Namba, S.; Ohnishi, K.; Rattenbury, N. J.; Saito, To; Sullivan, D. J.; Suzuki, D.; Sweatman, W. L.; Tristram, P. J.; Tsurumi, N.; Wada, K.; Yamai, N.; Yock, P. C. M.; Yonehara, A.; MOA Collaboration; Szymański, M. K.; Kubiak, M.; Pietrzyński, G.; Soszyński, I.; Skowron, J.; Kozłowski, S.; Poleski, R.; Ulaczyk, K.; Wyrzykowski, Ł.; Pietrukowicz, P.; OGLE Collaboration; Almeida, L. A.; Bos, M.; Choi, J.-Y.; Christie, G. W.; Depoy, D. L.; Dong, S.; Friedmann, M.; Hwang, K.-H.; Jablonski, F.; Jung, Y. K.; Kaspi, S.; Lee, C.-U.; Maoz, D.; McCormick, J.; Moorhouse, D.; Natusch, T.; Ngan, H.; Pogge, R. W.; Shin, I.-G.; Shvartzvald, Y.; Tan, T.-G.; Thornley, G.; Yee, J. C.; μFUN Collaboration; Allan, A.; Bramich, D. M.; Browne, P.; Dominik, M.; Horne, K.; Hundertmark, M.; Figuera Jaimes, R.; Kains, N.; Snodgrass, C.; Steele, I. A.; Street, R. A.; RoboNet Collaboration

    2014-10-01

    The mass of the lenses giving rise to Galactic microlensing events can be constrained by measuring the relative lens-source proper motion and lens flux. The flux of the lens can be separated from that of the source, companions to the source, and unrelated nearby stars with high-resolution images taken when the lens and source are spatially resolved. For typical ground-based adaptive optics (AO) or space-based observations, this requires either inordinately long time baselines or high relative proper motions. We provide a list of microlensing events toward the Galactic bulge with high relative lens-source proper motion that are therefore good candidates for constraining the lens mass with future high-resolution imaging. We investigate all events from 2004 to 2013 that display detectable finite-source effects, a feature that allows us to measure the proper motion. In total, we present 20 events with μ >~ 8 mas yr-1. Of these, 14 were culled from previous analyses while 6 are new, including OGLE-2004-BLG-368, MOA-2005-BLG-36, OGLE-2012-BLG-0211, OGLE-2012-BLG-0456, MOA-2012-BLG-532, and MOA-2013-BLG-029. In lsim12 yr from the time of each event the lens and source of each event will be sufficiently separated for ground-based telescopes with AO systems or space telescopes to resolve each component and further characterize the lens system. Furthermore, for the most recent events, comparison of the lens flux estimates from images taken immediately to those estimated from images taken when the lens and source are resolved can be used to empirically check the robustness of the single-epoch method currently being used to estimate lens masses for many events.

  7. A PUZZLE INVOLVING GALACTIC BULGE MICROLENSING EVENTS

    SciTech Connect

    Cohen, Judith G.; Gould, Andrew; Johnson, Jennifer A.; Thompson, Ian B.; Feltzing, Sofia; Bensby, Thomas; Huang Wenjin; Melendez, Jorge; Lucatello, Sara; Asplund, Martin E-mail: gould@astronomy.ohio-state.edu E-mail: ian@obs.carnegiescience.edu E-mail: tbensby@eso.org E-mail: jorge@astro.up.pt E-mail: asplund@MPA-Garching.MPG.DE

    2010-03-01

    We study a sample of 16 microlensed Galactic bulge main-sequence turnoff region stars for which high-dispersion spectra have been obtained with detailed abundance analyses. We demonstrate that there is a very strong and highly statistically significant correlation between the maximum magnification of the microlensed bulge star and the value of the [Fe/H] deduced from the high resolution spectrum of each object. Physics demands that this correlation, assuming it to be real, be the result of some sample bias. We suggest several possible explanations, but are forced to reject them all, and are left puzzled. To obtain a reliable metallicity distribution in the Galactic bulge based on microlensed dwarf stars, it will be necessary to resolve this issue through the course of additional observations.

  8. Microlensing candidate selection and detection efficiency for the SuperMACHO Dark Matter search

    NASA Astrophysics Data System (ADS)

    Garg, Arti

    One of the outstanding questions in modern cosmology is understanding the composition of the Dark Matter within our own Galaxy. The 5.7 year MACHO project which was completed in 2000, provided a rather vexing answer to this question. The MACHO project sought to place constraints on the fraction of the Galactic Dark Matter composed of MAssive Compact Halo Objects (MACHOs), or sub- stellar mass objects in the Milky Way halo. To accomplish this goal, the MACHO team measured the rate of gravitational microlensing toward the Magellanic Clouds to infer the MACHO concentration along the line-of-sight. The project's finding was vexing in that while the largest Milky Way halo mass fraction consistent with the results was not sufficient to explain all the "missing" matter in the Galaxy, the rate of microlensing observed could not be explained by known populations of objects. The SuperMACHO project seeks to independently verify the optical depth toward the Large Magellanic Cloud and also provide additional clues regarding the location of the lens. By determining the differential rate of microlensing across the face of the LMC, SuperMACHO distinguishes between "screen-" and "self-" lensing scenarios. This thesis describes the selection criteria used to arrive at a candidate set of microlensing events from the SuperMACHO survey and the efficiency with which the SuperMACHO project detects microlensing. The efficiency analysis is accomplished by simulating light curves over a spatial and temporal subset of the survey data. Assuming the optical depth observed by the MACHO project, we expect 14 microlensing events to pass our tighter set of selection criteria in this subset of data. Because type Ia supernovae remain a persistent contaminant in the SuperMACHO candidate set, this thesis also describes a method for determining the expected number of supernova contaminants in the SuperMACHO candidate set. We expect between 6 and 12 type Ia supernovae depending on which supernova rate

  9. Augmenting WFIRST Microlensing with a Ground-Based Telescope Network

    NASA Astrophysics Data System (ADS)

    Zhu, Wei; Gould, Andrew

    2016-06-01

    Augmenting the Wide Field Infrared Survey Telescope (WFIRST) microlensing campaigns with intensive observations from a ground-based network of wide-field survey telescopes would have several major advantages. First, it would enable full two-dimensional (2-D) vector microlens parallax measurements for a substantial fraction of low-mass lenses as well as planetary and binary events that show caustic crossing features. For a significant fraction of the free-floating planet (FFP) events and all caustic-crossing planetary/binary events, these 2-D parallax measurements directly lead to complete solutions (mass, distance, transverse velocity) of the lens object (or lens system). For even more events, the complementary ground-based observations will yield 1-D parallax measurements. Together with the 1-D parallaxes from WFIRST alone, they can probe the entire mass range M > M_Earth. For luminous lenses, such 1-D parallax measurements can be promoted to complete solutions (mass, distance, transverse velocity) by high-resolution imaging. This would provide crucial information not only about the hosts of planets and other lenses, but also enable a much more precise Galactic model. Other benefits of such a survey include improved understanding of binaries (particularly with low mass primaries), and sensitivity to distant ice-giant and gas-giant companions of WFIRST lenses that cannot be detected by WFIRST itself due to its restricted observing windows. Existing ground-based microlensing surveys can be employed if WFIRST is pointed at lower-extinction fields than is currently envisaged. This would come at some cost to the event rate. Therefore the benefits of improved characterization of lenses must be weighed against these costs.

  10. Chalcogenide glass microlenses by inkjet printing

    SciTech Connect

    Sanchez, Eric A.; Waldmann, Maike; Arnold, Craig B.

    2011-05-10

    We demonstrate micrometer scale mid-IR lenses for integrated optics, using solution-based inkjet printing techniques and subsequent processing. Arsenic sulfide spherical microlenses with diameters of 10-350 {mu}m and focal lengths of 10-700 {mu}m have been fabricated. The baking conditions can be used to tune the precise focal length.

  11. Empirical microlensing event rates predicted by a phenomenological model

    NASA Astrophysics Data System (ADS)

    Poleski, Radosław

    2016-02-01

    Estimating the number of microlensing events observed in different parts of the Galactic bulge is a crucial point in planning microlensing experiments. Reliable estimates are especially important if observing resources are scarce, as is the case for space missions: K2, WFIRST, and Euclid. Here we show that the number of detected events can be reliably estimated based on statistics of stars observed in targeted fields. The statistics can be estimated relatively easily, which makes presented method suitable for planning future microlensing experiments.

  12. Is Space-based Interferometry Dead?

    NASA Astrophysics Data System (ADS)

    Leisawitz, David; Benford, D.; Blain, A.; Carr, J.; Fich, M.; Fischer, J.; Goldsmith, P.; Greaves, J.; Griffin, M.; Helou, G.; Ivison, R.; Kuchner, M.; Lyon, R.; Matsuo, H.; Rinehart, S. A.; Serabyn, E.; Shibai, H.; Silverberg, R.; Staguhn, J.; Unwin, S.; Wilner, D.; Wootten, A.; Wright, E. L.

    2011-05-01

    In the wake of the Decadal Survey and a January 2011 meeting of NASA's Exoplanet Exploration Program Analysis Group (ExoPAG), one might be tempted to conclude that space interferometry is dead. We explain why this slogan is hyperbole, summarize the steps currently being taken to prepare for a space-based far-IR interferometer, and reiterate the science case for an imaging and spectroscopic interferometer - SPIRIT - that would operate in space at long infrared wavelengths. Space-based interferometry is alive and well, but the center of activity has shifted to a spectral region (25 to 400 microns) in which no alternative measurement technique can provide information essential to answering several scientific questions deemed compelling by the Decadal Survey. Astrophysicists will use SPIRIT to: discover how the conditions for habitability arise during planetary system formation; find and characterize exoplanets by measuring their sculpting effects on protoplanetary and debris disks; and study the formation, merger history, and star formation history of galaxies.

  13. Microlensing of quasar ultraviolet iron emission

    SciTech Connect

    Guerras, E.; Mediavilla, E.; Kochanek, C. S.; Muñoz, J. A.; Falco, E.; Motta, V.; Rojas, K.

    2013-12-01

    We measure the differential microlensing of the UV Fe II and Fe III emission line blends between 14 quasar image pairs in 13 gravitational lenses. We find that the UV iron emission is strongly microlensed in four cases with amplitudes comparable to that of the continuum. Statistically modeling the magnifications, we infer a typical size of r{sub s}∼4√(M/M{sub ⊙}) light-days for the Fe line-emitting regions, which is comparable to the size of the region generating the UV continuum (∼3-7 light-days). This may indicate that a significant part of the UV Fe II and Fe III emission originates in the quasar accretion disk.

  14. Halo cold dark matter and microlensing

    SciTech Connect

    Gates, Evalyn; Turner, Michael S.

    1993-12-01

    There is good evidence that most of the baryons in the Universe are dark and some evidence that most of the matter in the Universe is nonbaryonic with cold dark matter (cdm) being a promising possibility. We discuss expectations for the abundance of baryons and cdm in the halo of our galaxy and locally. We show that in plausible cdm models the local density of cdm is at least $10^{-25}\\gcmm3$. We also discuss what one can learn about the the local cdm density from microlensing of stars in the LMC by dark stars in the halo and, based upon a suite of reasonable two-component halo models, conclude that microlensing is not a sensitive probe of the local cdm density.

  15. The MACHO project: Microlensing and variable stars

    SciTech Connect

    Alcock, C.; Alves, D. R.; Axelrod, T. S.; Bennett, D. P.; Marshall, S. L.; Minniti, D.

    1996-10-01

    The MACHO Project monitors millions of stars in the Large Magellanic Cloud, the Small Magellanic Cloud and the bulge of the Milky Way searching for the gravitational microlensing signature of baryonic dark matter. This Project has yielded surprising results. An analysis of two years of data monitoring the Large Magellanic Cloud points to {approximately} 50% of the mass of the Milky Way`s halo in compact objects of {approximately} 0.5 solar mass. An analysis of one year of monitoring the bulge has yielded more microlensing than predicted without invocation of a massive bar or significant disk dark matter. The huge database of light curves created by this search is yielding information on extremely rare types of astrophysical variability as well as providing temporal detail for the study of well known variable astrophysical phenomena. The variable star catalog created from this database is previewed and example light curves are presented. 31 refs., 7 figs., 1 tab.

  16. Topics in microlensing and dark energy

    NASA Astrophysics Data System (ADS)

    Yashar, Mark

    In this dissertation we describe two separate research projects. The first project involves the utilization and development of reddening models, color magnitude diagrams (CMDs), and microlensing population models of the Large Magellanic Cloud (LMC) to constrain the locations of micro-lensing source stars and micro-lensing objects in the Large Magellanic Cloud and the Milky Way (MW) halo using data of 13 microlensing source stars obtained by the MACHO (massive compact halo objects) collaboration with the Hubble Space Telescope. This analysis suggests that the source stars are located in the LMC disk and the lenses are located in the MW halo. For the second project, we report on the results of a Markov Chain Monte Carlo (MCMC) analysis of an inverse power law (IPL) quintessence model using the Dark Energy Task Force (DETF) simulated data models as a representation of future dark energy experiments. Simulated data sets were generated for a Lambda cold dark matter (L CDM ) background cosmology as well as a case where the dark energy is provided by a specific IPL fiducial model. The results are presented in the form of error contours generated by these two background cosmologies which are then used to consider the effects of future dark energy projects on IPL scalar field models and are able to demonstrate the power of DETF Stage 4 data sets in the context of the IPL model. We find that the respective increase in constraining power with higher quality data sets produced by our analysis gives results that are broadly consistent with the DETF results for the w 0 - w a parameterization of dark energy. Finally, using our simulated data sets constructed around a fiducial IPL model, we find that for a universe containing dark energy described by such a scalar field, a cosmological constant can be excluded by Stage 4 data at the 3s level.

  17. Improved Theoretical Predictions of Microlensing Rates for the Detection of Primordial Black Hole Dark Matter

    NASA Astrophysics Data System (ADS)

    Cieplak, Agnieszka M.; Griest, Kim

    2013-04-01

    Primordial black holes (PBHs) remain a dark matter (DM) candidate of the Standard Model of Particle Physics. Previously, we proposed a new method of constraining the remaining PBH DM mass range using microlensing of stars monitored by NASA's Kepler mission. We improve this analysis using a more accurate treatment of the population of the Kepler source stars, their variability, and limb darkening. We extend the theoretically detectable PBH DM mass range down to 2 × 10-10 M ⊙, two orders of magnitude below current limits and one-third order of magnitude below our previous estimate. We address how to extract the DM properties, such as mass and spatial distribution, if PBH microlensing events were detected. We correct an error in a well-known finite-source limb-darkening microlensing formula and also examine the effects of varying the light curve cadence on PBH DM detectability. We also introduce an approximation for estimating the predicted rate of detection per star as a function of the star's properties, thus allowing for selection of source stars in future missions, and extend our analysis to planned surveys, such as the Wide-Field Infrared Survey Telescope.

  18. MICROLENSING DISCOVERY OF A POPULATION OF VERY TIGHT, VERY LOW MASS BINARY BROWN DWARFS

    SciTech Connect

    Choi, J.-Y.; Han, C.; Udalski, A.; Sumi, T.; Gaudi, B. S.; Gould, A.; Bennett, D. P.; Dominik, M.; Beaulieu, J.-P.; Tsapras, Y.; Bozza, V.; Abe, F.; Furusawa, K.; Itow, Y.; Bond, I. A.; Ling, C. H.; Botzler, C. S.; Freeman, M.; Chote, P.; Fukui, A.; Collaboration: MOA Collaboration; OGLE Collaboration; muFUN Collaboration; MiNDSTEp Consortium; PLANET Collaboration; RoboNet Collaboration; and others

    2013-05-10

    Although many models have been proposed, the physical mechanisms responsible for the formation of low-mass brown dwarfs (BDs) are poorly understood. The multiplicity properties and minimum mass of the BD mass function provide critical empirical diagnostics of these mechanisms. We present the discovery via gravitational microlensing of two very low mass, very tight binary systems. These binaries have directly and precisely measured total system masses of 0.025 M{sub Sun} and 0.034 M{sub Sun }, and projected separations of 0.31 AU and 0.19 AU, making them the lowest-mass and tightest field BD binaries known. The discovery of a population of such binaries indicates that BD binaries can robustly form at least down to masses of {approx}0.02 M{sub Sun }. Future microlensing surveys will measure a mass-selected sample of BD binary systems, which can then be directly compared to similar samples of stellar binaries.

  19. WFIRST-AFTA: What Can We Learn by Detecting Thousands of Cold Exoplanets via Microlensing?

    NASA Astrophysics Data System (ADS)

    Penny, Matthew

    2014-06-01

    The WFIRST-AFTA microlensing survey will monitor a few hundred million stars in the Galactic bulge every ~15 minutes to measure the microlensing signatures of thousands of both bound and free-floating planets with masses ranging from super-Jupiters down to that of Ganymede. This huge sample of cold planets will perfectly compliment the sample of warm and hot planets that have been found by Kepler and will be further expanded by TESS and PLATO. I will review the measurements that WFIRST-AFTA will make for each of the planets it finds, and attempt to predict the impact that these will have on our understanding of exoplanet demographics and the planet formation process.

  20. Detectability of orbital motion in stellar binary and planetary microlenses

    NASA Astrophysics Data System (ADS)

    Penny, Matthew T.; Mao, Shude; Kerins, Eamonn

    2011-03-01

    A standard binary microlensing event light curve allows just two parameters of the lensing system to be measured: the mass ratio of the companion to its host and the projected separation of the components in units of the Einstein radius. However, other exotic effects can provide more information about the lensing system. Orbital motion in the lens is one such effect, which, if detected, can be used to constrain the physical properties of the lens. To determine the fraction of binary-lens light curves affected by orbital motion (the detection efficiency), we simulate light curves of orbiting binary star and star-planet (planetary) lenses and simulate the continuous, high-cadence photometric monitoring that will be conducted by the next generation of microlensing surveys that are beginning to enter operation. The effect of orbital motion is measured by fitting simulated light-curve data with standard static binary microlensing models; light curves that are poorly fitted by these models are considered to be detections of orbital motion. We correct for systematic false positive detections by also fitting the light curves of static binary lenses. For a continuous monitoring survey without intensive follow-up of high-magnification events, we find the orbital motion detection efficiency for planetary events with caustic crossings to be 0.061 ± 0.010, consistent with observational results, and 0.0130 ± 0.0055 for events without caustic crossings (smooth events). Similarly, for stellar binaries, the orbital motion detection efficiency is 0.098 ± 0.011 for events with caustic crossings and is 0.048 ± 0.006 for smooth events. These result in combined (caustic-crossing and smooth) orbital motion detection efficiencies of 0.029 ± 0.005 for planetary lenses and 0.070 ± 0.006 for stellar binary lenses. We also investigate how various microlensing parameters affect the orbital motion detectability. We find that the orbital motion detection efficiency increases as the binary

  1. Using microlensed quasars to probe the structure of the Milky Way

    NASA Astrophysics Data System (ADS)

    Wang, Jian; Smith, Martin C.

    2011-01-01

    This paper presents an investigation into the gravitational microlensing of quasars by stars and stellar remnants in the Milky Way. We present predictions for the all-sky microlensing optical depth, time-scale distributions and event rates for future large-area sky surveys. As expected, the total event rate increases rapidly with increasing magnitude limit, reflecting the fact that the number density of quasars is a steep function of magnitude. Surveys, such as Pan-STARRS and LSST, should be able to detect more than 10 events per year, with typical event durations of around 1 month. Since microlensing of quasar sources suffers from fewer degeneracies than lensing of Milky Way sources, they could be used as a powerful tool for recovering the mass of the lensing object in a robust, often model-independent, manner. As a consequence, for a subset of these events, it will be possible to directly `weigh' the star (or stellar remnant) that is causing the lensing signal, either through higher order microlensing effects and/or high-precision astrometric observations of the lens star (using e.g. Gaia or SIM-lite). This means that such events could play a crucial role in stellar astronomy. Given the current operational timelines for Pan-STARRS and LSST, by the end of the decade, they could potentially detect up to 100 events. Although this is still too few events to place detailed constraints on Galactic models, consistency checks can be carried out and such samples could lead to exciting and unexpected discoveries.

  2. Adventures in the microlensing cloud: Large datasets, eResearch tools, and GPUs

    NASA Astrophysics Data System (ADS)

    Vernardos, G.; Fluke, C. J.

    2014-10-01

    As astronomy enters the petascale data era, astronomers are faced with new challenges relating to storage, access and management of data. A shift from the traditional approach of combining data and analysis at the desktop to the use of remote services, pushing the computation to the data, is now underway. In the field of cosmological gravitational microlensing, future synoptic all-sky surveys are expected to bring the number of multiply imaged quasars from the few tens that are currently known to a few thousands. This inflow of observational data, together with computationally demanding theoretical modeling via the production of microlensing magnification maps, requires a new approach. We present our technical solutions to supporting the GPU-Enabled, High Resolution cosmological MicroLensing parameter survey (GERLUMPH). This extensive dataset for cosmological microlensing modeling comprises over 70 000 individual magnification maps and ˜106 related results. We describe our approaches to hosting, organizing, and serving ˜ 30 TB of data and metadata products. We present a set of online analysis tools developed with PHP, JavaScript and WebGL to support access and analysis of GELRUMPH data in a Web browser. We discuss our use of graphics processing units (GPUs) to accelerate data production, and we release the core of the GPU-D direct inverse ray-shooting code (Thompson et al., 2010, 2014) used to generate the magnification maps. All of the GERLUMPH data and tools are available online from http://gerlumph.swin.edu.au. This project made use of gSTAR, the GPU Supercomputer for Theoretical Astrophysical Research.

  3. Space-Based Lidar Systems

    NASA Technical Reports Server (NTRS)

    Sun, Xiaoli

    2012-01-01

    An overview of space-based lidar systems is presented. from the first laser altimeter on APOLLO 15 mission in 1971 to the Mercury Laser Altimeter on MESSENGER mission currently in orbit, and those currently under development. Lidar, which stands for Light Detection And Ranging, is a powerful tool in remote sensing from space. Compared to radars, lidars operate at a much shorter wavelength with a much narrower beam and much smaller transmitter and receiver. Compared to passive remote sensing instruments. lidars carry their own light sources and can continue measuring day and night. and over polar regions. There are mainly two types of lidars depending on the types of measurements. lidars that are designed to measure the distance and properties of hard targets are often called laser rangers or laser altimeters. They are used to obtain the surface elevation and global shape of a planet from the laser pulse time-of-night and the spacecraft orbit position. lidars that are designed to measure the backscattering and absorption of a volume scatter, such as clouds and aerosols, are often just called lidars and categorized by their measurements. such as cloud and aerosol lidar, wind lidar, CO2 lidar, and so on. The advantages of space-based lidar systems over ground based lidars are the abilities of global coverage and continuous measurements.

  4. Searching for MACHOs with microlensing

    SciTech Connect

    Alcock, C.

    1996-04-01

    Baryonic matter, in the form of Machos (Massive Compact Halo Objects), might be a significant constituent of the dark matter that dominates the Milky Way. This article describes the experimental searches for Machos that exploit the gravitational microlens magnification of extragalactic stars. These surveys monitor millions of stars, in some cases every night, looking for magnification events. The early results from the surveys have yielded some spectacular events, and pose a significant new puzzle for galactic structure: toward the Large Magellanic Cloud we see fewer events than anticipated for a standard dark halo dominated by Machos, but toward the galactic bulge, the event rate is much higher than anticipated. This is a field of research that is ripe with opportunities for beginning (and senior) scientists.

  5. Gravitational microlensing searches and results

    SciTech Connect

    Alcock, C.

    1997-05-08

    Baryonic matter, in the form of Machos (MAssive Compact Halo Objects), might be a significant constituent of the dark matter that dominates the Milky Way. This article describes how surveys for Machos exploit the gravitational microlens magnification of extragalactic stars. The experimental searches for this effect monitor millions of stars, in some cases every night, looking for magnification events. The early results of these surveys indicate that Machos make up a significant fraction of the dark matter in the Milky Way, and that these objects have stellar masses. Truly substellar objects do not contribute much to the total. Additionally, the relatively high event rate towards the Galactic bulge seems to require that the bulge be elongated, and massive.

  6. Space based astronomy: Teacher's guide with activities

    NASA Technical Reports Server (NTRS)

    Rosenberg, Carla B. (Editor); Weiler, Edward; Morrow, Cherilyn; Bacon, Pamela M.; Thorne, Muriel; Blanchard, Paul A.; Howard, Sethane; Pengra, Patricia R.; Brown, Deborah A.; Winrich, Ralph

    1994-01-01

    This curriculum guide uses hands-on activities to help students and teachers understand the significance of space-based astronomy - astronomical observations made from outer space. The guide contains few of the traditional activities found in many astronomy guides such as constellation studies, lunar phases, and planetary orbits. Instead, it tells the story of why it is important to observe celestial objects from outer space and how to study the entire electromagnetic spectrum. The guide begins with a survey of astronomy related NASA spacecraft. This is followed by a collection of activities in four units: (1) the atmospheric filter; (2) the electromagnetic spectrum; (3) collecting electromagnetic radiation; and (4) down to Earth. A curriculum index identifies the curriculum areas each activity addresses. The guide concludes with a glossary, reference list, a NASA Resources list, and an evaluation card. It is designed for students in grades 5 through 8.

  7. Microlensing Events from the 11 Year Observations of the Wendelstein Calar Alto Pixellensing Project

    NASA Astrophysics Data System (ADS)

    Lee, C.-H.; Riffeser, A.; Seitz, S.; Bender, R.; Koppenhoefer, J.

    2015-06-01

    We present the results of the decade-long M31 observation from the Wendelstein Calar Alto Pixellensing Project (WeCAPP). WeCAPP has monitored M31 from 1997 until 2008 in both R- and I-filters, and thus provides the longest baseline of all M31 microlensing surveys. The data are analyzed with difference imaging analysis, which is most suitable for studying variability in crowded stellar fields. We extracted light curves based on each pixel, and devised selection criteria that are optimized to identify microlensing events. This leads to 10 new events, and adds up to a total of 12 microlensing events from WeCAPP, for which we derive their timescales, flux excesses, and colors from their light curves. The colors of the lensed stars fall in the range (R - I) = 0.56 to 1.36, with a median of 1.0 mag, in agreement with our expectation that the sources are most likely bright, red stars at the post-main-sequence stage. The event FWHM timescales range from 0.5 to 14 days, with a median of 3 days, in good agreement with predictions based on the model of Riffeser et al.

  8. Magnification bias in galactic microlensing searches

    NASA Technical Reports Server (NTRS)

    Nemiroff, Robert J.

    1994-01-01

    It is shown that a significant amount of detectable gravitational microlensing events that could potentially be found by Massively Parallel Photometry (MAPP) project (such as the MACHO, EROS, and OGLE collaborations) will occur for stars too dim to be easily noticed individually by these projects. This is the result of a large magnification bias effect, a bias of including high-magnification events in any flux-limited sample. The probablility of detecting these events may be as high as 2.3 times the lensing probability of stars currently being monitored by MAPP collaborations.

  9. Searches for Exoplanets with Gravitational Microlensing

    NASA Astrophysics Data System (ADS)

    Zakharov, Alexander

    2016-07-01

    There are different methods for finding exoplanets such as radial spectral shifts, astrometrical measurements, transits, timing etc. Gravitational microlensing (including pixel-lensing) is among the most promising techniques with the potentiality of detecting Earth-like planets at distances about a few astronomical units from their host star. We emphasize the importance of polarization measurements which can help to resolve degeneracies in theoretical models. In particular, the polarization angle could give additional information about the relative position of the lens with respect to the source.

  10. Space-Based Astronomy: A Teacher's Guide with Activities.

    ERIC Educational Resources Information Center

    National Aeronautics and Space Administration, Washington, DC.

    This curriculum guide uses hands-on activities to help grade 5-8 students and teachers understand the significance of space-based astronomy--astronomical observations made from outside the Earth's atmosphere. The guide begins with a survey of astronomy-related spacecraft that the National Aeronautics and Space Administration (NASA) has sent into…

  11. On space-based SETI

    NASA Technical Reports Server (NTRS)

    Stuiver, Willem

    1990-01-01

    Space-based antenna systems for the search of signals from extra-terrestrial intelligence are discussed. Independent studies of the ecliptic solar-sailing transfer problem from the geosynchronous departure orbit to Sun-Earth collinear transterrestrial liberation point were conducted. They were based on a relatively simple mathematical model describing attitude-controlled spacecraft motion in the ecliptic plane as governed by solar and terrestrial gravitational attraction together with the solar radiation pressure. The resulting equations of motion were integrated numerically for a relevant range of values of spacecraft area-to-mass ratio and for an appropriate spacecraft attitude-control law known to lead to Earth escape. Experimentation with varying initial conditions in the departure orbit, and with attitude-control law modification after having achieved Earth escape, established the feasibility of component deployment by means of solar sailing. Details are presented.

  12. Large Magellanic Cloud Microlensing Optical Depth with Imperfect Event Selection

    NASA Astrophysics Data System (ADS)

    Bennett, David P.

    2005-11-01

    I present a new analysis of the MACHO Project 5.7 yr Large Magellanic Cloud (LMC) microlensing data set that incorporates the effects of contamination of the microlensing event sample by variable stars. Photometric monitoring of MACHO LMC microlensing event candidates by the EROS and OGLE groups has revealed that one of these events is likely to be a variable star, while additional data have confirmed that many of the other events are very likely to be microlensing. These additional data on the nature of the MACHO microlensing candidates are incorporated into a simple likelihood analysis to derive a probability distribution for the number of MACHO microlens candidates that are true microlensing events. This analysis shows that 10-12 of the 13 events that passed the MACHO selection criteria are likely to be microlensing events, with the other 1-3 being variable stars. This likelihood analysis is also used to show that the main conclusions of the MACHO LMC analysis are unchanged by the variable star contamination. The microlensing optical depth toward the LMC is τ=(1.0+/-0.3)×10-7. If this is due to microlensing by known stellar populations plus an additional population of lens objects in the Galactic halo, then the new halo population would account for 16% of the mass of a standard Galactic halo. The MACHO detection exceeds the expected background of two events expected from ordinary stars in standard models of the Milky Way and LMC at the 99.98% confidence level. The background prediction is increased to three events if maximal disk models are assumed for both the Milky Way and LMC, but this model fails to account for the full signal seen by MACHO at the 99.8% confidence level.

  13. Halo Microlensing and Dark Baryons

    NASA Astrophysics Data System (ADS)

    Crotts, A. P. S.

    1993-12-01

    (While Pierce lectures review past accomplishments, customarily, this talk concerns efforts which we have pursued for some years and which are now reaching fruition. We present elsewhere at this meeting results from research cited for the Prize.) Dark matter exists in the halos of spiral galaxies, and the least radical alternative for its identity is normal matter produced by primordial nucleosynthesis. This matter could easily be hidden in large, condensed objects. Paczynski pointed out in 1986 that if condensations of Galactic halo matter are sufficiently massive, they will produce detectable amplification of background starlight by gravitational lensing. Several groups recently reported possible detections of this effect after surveying large numbers of stars in the Galactic Bulge and LMC. The connection between these events and massive, dark halos is unclear and likely to remain so for some time, given the rate at which they are detected. Following Paczynski's realization, we stressed that a much higher event rate, a statistical control sample, sensitivity to a much broader mass range, and modulation of the predicted lensing rate with galactocentric distance can all be realized by a different experiment: observing the halo of M31 (and the Galaxy) using stars in M31. In some ways, M31 is a more difficult target than the LMC or the Bulge, given the faintness of its stars, but our observations in 1991 and 1993 indicate that these problems have been surmounted. We can detect stellar variability even under extremely crowded conditions like those in M31's inner disk, and can monitor a sufficient number of stars to study halo lensing. We present results from our initial survey which indicates that the required sensitivity can be reached to confirm or reject the hypothesis that sub-solar masses like those detected in our Galaxy make up the missing spiral galaxy mass. It is possible that we may use the data already obtained (and still being analyzed) to place

  14. Determination of Stellar Shape via Microlensing

    NASA Astrophysics Data System (ADS)

    Rattenbury, Nicholas J.; Yock, Phil; Bond, Ian

    2006-06-01

    Einstein predicted that light from a distant ``source'' star would be deflected by the gravitational field of an intervening ``lens'' star: the phenomenon known as gravitational microlensing. The lens star produces magnified and distorted images of the source, and as the lens passes between the observer and the source, the magnification changes. For lens systems in our Galaxy, events occur on timescales of weeks to months. Lens systems comprised of more than one object can produce complex light curves. Such light curves can be analysed to obtain information about both the lens and the source systems. These analyses include the detection of low-mass extra-solar planets and the limb-darkening characteristics of distant stars. In this paper, we present the results from one extreme microlensing event for which the limb-darkening of the 5 kpc distant source star was determined, as well as limits on the shape of the projected source star profile. The effective resolution of these measurements is approximately 0.04 microarcsec.

  15. MICROLENSING BINARIES WITH CANDIDATE BROWN DWARF COMPANIONS

    SciTech Connect

    Shin, I.-G.; Han, C.; Gould, A.; Skowron, J.; Udalski, A.; Szymanski, M. K.; Kubiak, M.; Soszynski, I.; Pietrzynski, G.; Poleski, R.; Ulaczyk, K.; Pietrukowicz, P.; Kozlowski, S.; Wyrzykowski, L.; Sumi, T.; Dominik, M.; Beaulieu, J.-P.; Tsapras, Y.; Bozza, V.; Abe, F.; Collaboration: OGLE Collaboration; MOA Collaboration; muFUN Collaboration; and others

    2012-12-01

    Brown dwarfs are important objects because they may provide a missing link between stars and planets, two populations that have dramatically different formation histories. In this paper, we present the candidate binaries with brown dwarf companions that are found by analyzing binary microlensing events discovered during the 2004-2011 observation seasons. Based on the low mass ratio criterion of q < 0.2, we found seven candidate events: OGLE-2004-BLG-035, OGLE-2004-BLG-039, OGLE-2007-BLG-006, OGLE-2007-BLG-399/MOA-2007-BLG-334, MOA-2011-BLG-104/OGLE-2011-BLG-0172, MOA-2011-BLG-149, and MOA-201-BLG-278/OGLE-2011-BLG-012N. Among them, we are able to confirm that the companions of the lenses of MOA-2011-BLG-104/OGLE-2011-BLG-0172 and MOA-2011-BLG-149 are brown dwarfs by determining the mass of the lens based on the simultaneous measurement of the Einstein radius and the lens parallax. The measured masses of the brown dwarf companions are 0.02 {+-} 0.01 M {sub Sun} and 0.019 {+-} 0.002 M {sub Sun} for MOA-2011-BLG-104/OGLE-2011-BLG-0172 and MOA-2011-BLG-149, respectively, and both companions are orbiting low-mass M dwarf host stars. More microlensing brown dwarfs are expected to be detected as the number of lensing events with well-covered light curves increases with new-generation searches.

  16. Microlenses with focal length controlled by chemical processes

    NASA Astrophysics Data System (ADS)

    Muric, B. D.; Panic, B. M.

    2012-05-01

    The influence of chemical processing on the optical properties of microlenses formed on a gelatin-sensitized layer was investigated. The gelatin is sensitized with tot'hema and eosin, irradiated with a Gaussian profile laser beam and subsequently chemically processed. Microlenses with a focal length of 400 μm were obtained after alcohol processing. Additionally, focal lengths could be controlled by varying the alum concentration, and lenses with focal length up to 1.2 mm were obtained. The microlenses become stable after alum processing. Their optical properties remain unchanged.

  17. Resolving the Nature of the LMC Microlensing Event LMC-5

    SciTech Connect

    Drake, A J; Cook, K H; Keller, S C

    2004-04-22

    The authors present the results from an analysis of Hubble Space Telescope High Resolution Camera data for the Large Magellanic Cloud microlensing event MACHO-LMC-5. By determining the parallax and proper motion of this object they find that the lens is an M dwarf star at a distance of 578{sub -53}{sup +65}pc with a proper motion of 21.39 {+-} 0.04 mas/yr. Based on the kinematics and location of this star is it more likely to be part of the Galactic thick disk than thin disk population. They confirm that the microlensing event LMC-5 is a jerk-parallax microlensing event.

  18. MOA-II Galactic Microlensing Constraints: The Inner Milky Way has a Low Dark Matter Fraction and a Near Maximal Disk

    NASA Astrophysics Data System (ADS)

    Wegg, Christopher; Gerhard, Ortwin; Portail, Matthieu

    2016-08-01

    Microlensing provides a unique tool to break the stellar to dark matter degeneracy in the inner Milky Way. We combine N-body dynamical models fitted to the Milky Way's Boxy/Peanut bulge with exponential disk models outside this, and compute the microlensing properties. Considering the range of models consistent with the revised MOA-II data, we find low dark matter fractions in the inner Galaxy: at the peak of their stellar rotation curve a fraction fv = (0.88 ± 0.07) of the circular velocity is baryonic (at 1σ, fv > 0.72 at 2σ). These results are in agreement with constraints from the EROS-II microlensing survey of brighter resolved stars, where we find fv = (0.9 ± 0.1) at 1σ. Our fiducial model of a disk with scale length 2.6 kpc, and a bulge with a low dark matter fraction of 12%, agrees with both the revised MOA-II and EROS-II microlensing data. The required baryonic fractions, and the resultant low contribution from dark matter, are consistent with the NFW profiles produced by dissipationless cosmological simulations in Milky Way mass galaxies. They are also consistent with recent prescriptions for the mild adiabatic contraction of Milky Way mass haloes without the need for strong feedback, but there is some tension with recent measurements of the local dark matter density. Microlensing optical depths from the larger OGLE-III sample could improve these constraints further when available.

  19. Gravitational microlensing by a single star plus external shear

    NASA Technical Reports Server (NTRS)

    Mao, Shude

    1992-01-01

    Gravitational microlensing by a single star plus external shear is considered. It is shown that for a general cusp the magnification probability distribution follows pc(A)dA of about (A exp -7/2)dA for sufficiently large magnifications. An adaptive grid technique is developed to calculate the magnification probability distributions. The results could be useful for cases of microlensing where the surface-mass density is low.

  20. Microlensing observations rapid search for exoplanets: MORSE code for GPUs

    NASA Astrophysics Data System (ADS)

    McDougall, Alistair; Albrow, Michael D.

    2016-02-01

    The rapid analysis of ongoing gravitational microlensing events has been integral to the successful detection and characterization of cool planets orbiting low-mass stars in the Galaxy. In this paper, we present an implementation of search and fit techniques on graphical processing unit (GPU) hardware. The method allows for the rapid identification of candidate planetary microlensing events and their subsequent follow-up for detailed characterization.

  1. Difference Image Analysis of Galactic Microlensing. I. Data Analysis

    SciTech Connect

    Alcock, C.; Allsman, R. A.; Alves, D.; Axelrod, T. S.; Becker, A. C.; Bennett, D. P.; Cook, K. H.; Drake, A. J.; Freeman, K. C.; Griest, K.

    1999-08-20

    This is a preliminary report on the application of Difference Image Analysis (DIA) to Galactic bulge images. The aim of this analysis is to increase the sensitivity to the detection of gravitational microlensing. We discuss how the DIA technique simplifies the process of discovering microlensing events by detecting only objects that have variable flux. We illustrate how the DIA technique is not limited to detection of so-called ''pixel lensing'' events but can also be used to improve photometry for classical microlensing events by removing the effects of blending. We will present a method whereby DIA can be used to reveal the true unblended colors, positions, and light curves of microlensing events. We discuss the need for a technique to obtain the accurate microlensing timescales from blended sources and present a possible solution to this problem using the existing Hubble Space Telescope color-magnitude diagrams of the Galactic bulge and LMC. The use of such a solution with both classical and pixel microlensing searches is discussed. We show that one of the major causes of systematic noise in DIA is differential refraction. A technique for removing this systematic by effectively registering images to a common air mass is presented. Improvements to commonly used image differencing techniques are discussed. (c) 1999 The American Astronomical Society.

  2. CHEAP SPACE-BASED MICROLENS PARALLAXES FOR HIGH-MAGNIFICATION EVENTS

    SciTech Connect

    Gould, Andrew; Yee, Jennifer C. E-mail: jyee@astronomy.ohio-state.edu

    2012-08-10

    We show that for high-magnification (A{sub max} {approx}> 100) microlensing events, accurate microlens parallaxes can be obtained from three or fewer photometric measurements from a small telescope on a satellite in solar orbit at O(AU) from Earth. This is 1-2 orders of magnitude less observing resources than are required for standard space-based parallaxes. Such microlens parallax measurements would yield accurate mass and distance measurements to the lens for all cases in which finite-source effects were observed from the ground over peak. This would include virtually all high-magnification events with detected planets and a substantial fraction of those without. Hence, it would permit accurate estimates of the Galactic distribution of planets.

  3. Speeding up low-mass planetary microlensing simulations and modeling: The caustic region of influence

    SciTech Connect

    Penny, Matthew T.

    2014-08-01

    Extensive simulations of planetary microlensing are necessary both before and after a survey is conducted: before to design and optimize the survey and after to understand its detection efficiency. The major bottleneck in such computations is the computation of light curves. However, for low-mass planets, most of these computations are wasteful, as most light curves do not contain detectable planetary signatures. In this paper, I develop a parameterization of the binary microlens that is conducive to avoiding light curve computations. I empirically find analytic expressions describing the limits of the parameter space that contain the vast majority of low-mass planet detections. Through a large-scale simulation, I measure the (in)completeness of the parameterization and the speed-up it is possible to achieve. For Earth-mass planets in a wide range of orbits, it is possible to speed up simulations by a factor of ∼30-125 (depending on the survey's annual duty-cycle) at the cost of missing ∼1% of detections (which is actually a smaller loss than for the arbitrary parameter limits typically applied in microlensing simulations). The benefits of the parameterization probably outweigh the costs for planets below 100 M{sub ⊕}. For planets at the sensitivity limit of AFTA-WFIRST, simulation speed-ups of a factor ∼1000 or more are possible.

  4. Microlensing of the broad line region in 17 lensed quasars

    NASA Astrophysics Data System (ADS)

    Sluse, D.; Hutsemékers, D.; Courbin, F.; Meylan, G.; Wambsganss, J.

    2012-08-01

    When an image of a strongly lensed quasar is microlensed, the different components of its spectrum are expected to be differentially magnified owing to the different sizes of the corresponding emitting region. Chromatic changes are expected to be observed in the continuum while the emission lines should be deformed as a function of the size, geometry and kinematics of the regions from which they originate. Microlensing of the emission lines has been reported only in a handful of systems so far. In this paper we search for microlensing deformations of the optical spectra of pairs of images in 17 lensed quasars with bolometric luminosities between 1044.7 - 47.4 erg/s and black hole masses 107.6 - 9.8 M⊙. This sample is composed of 13 pairs of previously unpublished spectra and four pairs of spectra from literature. Our analysis is based on a simple spectral decomposition technique which allows us to isolate the microlensed fraction of the flux independently of a detailed modeling of the quasar emission lines. Using this technique, we detect microlensing of the continuum in 85% of the systems. Among them, 80% show microlensing of the broad emission lines. Focusing on the most common emission lines in our spectra (C III] and Mg II) we detect microlensing of either the blue or the red wing, or of both wings with the same amplitude. This observation implies that the broad line region is not in general spherically symmetric. In addition, the frequent detection of microlensing of the blue and red wings independently but not simultaneously with a different amplitude, does not support existing microlensing simulations of a biconical outflow. Our analysis also provides the intrinsic flux ratio between the lensed images and the magnitude of the microlensing affecting the continuum. These two quantities are particularly relevant for the determination of the fraction of matter in clumpy form in galaxies and for the detection of dark matter substructures via the identification

  5. MEASURING MICROLENSING USING SPECTRA OF MULTIPLY LENSED QUASARS

    SciTech Connect

    Motta, V.; Mediavilla, E.; Munoz, J. A. E-mail: emg@iac.es E-mail: jmunoz@uv.es

    2012-08-10

    We report on a program of spectroscopic observations of gravitationally lensed QSOs with multiple images. We seek to establish whether microlensing is occurring in each QSO image using only single-epoch observations. We calculate flux ratios for the cores of emission lines in image pairs to set a baseline for no microlensing. The offset of the continuum flux ratios relative to this baseline yields the microlensing magnification free from extinction, as extinction affects the continuum and the lines equally. When we find chromatic microlensing, we attempt to constrain the size of the QSO accretion disk. SDSSJ1004+4112 and HE1104-1805 show chromatic microlensing with amplitudes 0.2 < |{Delta}m| < 0.6 and 0.2 < |{Delta}m| < 0.4 mag, respectively. Modeling the accretion disk with a Gaussian source (I{proportional_to}exp (- R{sup 2}/2r{sup 2}{sub s})) of size r{sub s} {proportional_to}{lambda}{sup p} and using magnification maps to simulate microlensing, we find r{sub s} ({lambda}3363) = 7 {+-} 3 lt-day(18.1 {+-} 7.8 Multiplication-Sign 10{sup 15} cm) and p = 1.1 {+-} 0.4 for SDSS1004+4112, and r{sub s} ({lambda}3363) = 6 {+-} 2 lt-day(15.5 {+-} 5.2 Multiplication-Sign 10{sup 15} cm) and p = 0.7 {+-} 0.1 for HE1104-1805. For SDSSJ1029+2623, we find strong chromaticity of {approx}0.4 mag in the continuum flux ratio, which probably arises from microlensing, although not all the available data fit within this explanation. For Q0957+561, we measure B - A magnitude differences of 0.4 mag, much greater than the {approx}0.05 mag amplitude usually inferred from light-curve variability. It may substantially modify the current interpretations of microlensing in this system, likely favoring the hypothesis of smaller sources and/or larger microdeflectors. For HS0818+1227, our data yield possible evidence of microlensing.

  6. Free-floating planets from core accretion theory: microlensing predictions

    NASA Astrophysics Data System (ADS)

    Ma, Sizheng; Mao, Shude; Ida, Shigeru; Zhu, Wei; Lin, Douglas N. C.

    2016-09-01

    We calculate the microlensing event rate and typical time-scales for the free-floating planet (FFP) population that is predicted by the core accretion theory of planet formation. The event rate is found to be ˜1.8 × 10-3 of that for the stellar population. While the stellar microlensing event time-scale peaks at around 20 d, the median time-scale for FFP events (˜0.1 d) is much shorter. Our values for the event rate and the median time-scale are significantly smaller than those required to explain the Sumi et al. result, by factors of ˜13 and ˜16, respectively. The inclusion of planets at wide separations does not change the results significantly. This discrepancy may be too significant for standard versions of both the core accretion theory and the gravitational instability model to explain satisfactorily. Therefore, either a modification to the planet formation theory is required or other explanations to the excess of short-time-scale microlensing events are needed. Our predictions can be tested by ongoing microlensing experiment such as Korean Microlensing Telescope Network, and by future satellite missions such as WFIRST and Euclid.

  7. Short duration microlensing events: Searching for rogue planets

    NASA Astrophysics Data System (ADS)

    St. Laurent, Kathryn E.; Di Stefano, Rosanne; Primini, Francis A.; Lew, Wei Peng; Gau, Lai Su; Benson, Sophie

    2015-01-01

    Einstein described gravitational microlensing in 1936, at the same time suggesting it to be an unobservable phenomenon. He did not foresee technological advancements that would lead to microlensing becoming a productive tool for astronomy. Of particular interest may be the role it has begun to play in the discovery of rogue planets - exoplanets that are not bound to a star or stars. Rogue planets may be formed independently, or they may be formed in the confines of a stellar system and then ejected by gravitational interactions. Currently fewer than a dozen rogue planets are known but estimates of their abundance conservatively start at double the number of stars in our galaxy.The Optical Gravitational Lensing Experiment (OGLE) and Microlensing Observations in Astrophysics (MOA) teams have collectively detected approximately 2500 events this year alone. A significant portion of these events are of short duration, with an Einstein crossing time of less than 10 days. Microlensing events generally occur on a timescale of weeks to months, so short duration events are an interesting class for study, particularly with regard to searches for rogue planets. We have undertaken a systematic study and categorization of the short duration microlensing events from recent OGLE and MOA alerts, with a special eye to identifying exoplanet candidates.

  8. GRAVITATIONAL MICROLENSING BY THE ELLIS WORMHOLE

    SciTech Connect

    Abe, F.

    2010-12-10

    A method to calculate light curves of the gravitational microlensing of the Ellis wormhole is derived in the weak-field limit. In this limit, lensing by the wormhole produces one image outside the Einstein ring and another image inside. The weak-field hypothesis is a good approximation in Galactic lensing if the throat radius is less than 10{sup 11} km. The light curves calculated have gutters of approximately 4% immediately outside the Einstein ring crossing times. The magnification of the Ellis wormhole lensing is generally less than that of Schwarzschild lensing. The optical depths and event rates are calculated for the Galactic bulge and Large Magellanic Cloud fields according to bound and unbound hypotheses. If the wormholes have throat radii between 100 and 10{sup 7} km, are bound to the galaxy, and have a number density that is approximately that of ordinary stars, detection can be achieved by reanalyzing past data. If the wormholes are unbound, detection using past data is impossible.

  9. Probability distributions for the magnification of quasars due to microlensing

    NASA Technical Reports Server (NTRS)

    Wambsganss, Joachim

    1992-01-01

    Gravitational microlensing can magnify the flux of a lensed quasar considerably and therefore possibly influence quasar source counts or the observed quasar luminosity function. A large number of distributions of magnification probabilities due to gravitational microlensing for finite sources are presented, with a reasonable coverage of microlensing parameter space (i.e., surface mass density, external shear, mass spectrum of lensing objects). These probability distributions were obtained from smoothing two-dimensional magnification patterns with Gaussian source profiles. Different source sizes ranging from 10 exp 14 cm to 5 x 10 exp 16 cm were explored. The probability distributions show a large variety of shapes. Coefficients of fitted slopes for large magnifications are presented.

  10. Searching for intermediate-mass black holes with gravitational microlensing

    NASA Astrophysics Data System (ADS)

    Kains, Noé; Bramich, Dan; Sahu, Kailash C.; Calamida, Annalisa

    2016-06-01

    Despite a lot of indirect observational evidence, no intermediate-mass black hole (IMBH) has been detected unambiguously so far. A clear detection would shed light on the possible role of IMBHs in the formation of supermassive black holes, and on the evolution of Galaxies. This could be achieved with gravitational microlensing. We present the results of simulations to estimate the expected astrometric microlensing rates by IMBHs in globular clusters, and show that microlensing has the potential to detect signals that can be unambiguously attributed to an IMBH in several Galactic globular clusters. We also discuss the implication of our simulations for archival studies with available Hubble Space Telescope data, and the impact of JWST and WFIRST on possible future detections.

  11. Discovery of a Jupiter/Saturn Analog with Gravitational Microlensing

    SciTech Connect

    Gaudi, B; Bennett, D; Udalski, A; Gould, A; Christie, G; Maoz, D; Dong, S; McCormick, J; Szymanski, M; Tristram, P; Nikolaev, S; Paczynski, B; Kubiak, M; Pietrzynski, G; Soszynski, I; Szewczyk, O; Ulaczyk, K; Wyrzykowski, L; DePoy, D; Han, C; Kaspi, S; Lee, C; Mallia, F; Natusch, T; Pogge, R; Park, B; Abe, F; Bond, I; Botzler, C; Fukui, A; Hearnshaw, J; Itow, Y; Kamiya, K; Korpela, A; Kilmartin, P; Lin, W; Masuda, K; Matsubara, Y; Motomura, M; Muraki, Y; Nakamura, S; Okumura, T; Ohnishi, K; Rattenbury, N; Sako, T; Saito, T; Sato, S; Skuljan, L; Sullivan, D; Sumi, T; Sweatman, W; Yock, P; Albrow, M; Beaulieu, J; Burgdorf, M; Cook, K; Coutures, C; Dominik, M; Dieters, S; Fouque, P; Greenhill, J; Horne, K; Steele, I; Tsapras, Y; Chaboyer, B; Crocker, A; Frank, S; Macintosh, B

    2007-11-08

    Searches for extrasolar planets have uncovered an astonishing diversity of planetary systems, yet the frequency of solar system analogs remains unknown. The gravitational microlensing planet search method is potentially sensitive to multiple-planet systems containing analogs of all the solar system planets except Mercury. We report the first detection of a multiple-planet system with microlensing. We identify two planets with masses of {approx} 0.71 and {approx} 0.27 times the mass of Jupiter and orbital separations of {approx} 2.3 and {approx} 4.6 astronomical units orbiting a primary of mass {approx} 0.50 solar masses. This system resembles a scaled version of our solar system in that the mass ratio, separation ratio, and equilibrium temperatures of the planets are similar to those of Jupiter and Saturn. These planets could not have been detected with other techniques; their discovery from only 6 confirmed microlensing planet detections suggests that solar system analogs may be common.

  12. CHARACTERIZATION OF MICROLENSING PLANETS WITH MODERATELY WIDE SEPARATIONS

    SciTech Connect

    Han, Cheongho

    2009-08-01

    In future high-cadence microlensing surveys, planets can be detected through a new channel of an independent event produced by the planet itself. The two populations of planets to be detected through this channel are wide-separation planets and free-floating planets. Although they appear as similar short timescale events, the two populations of planets are widely different in nature and thus distinguishing them is important. In this paper, we investigate the lensing properties of events produced by planets with moderately wide separations from host stars. We find that the lensing behavior of these events is well described by the Chang-Refsdal lensing, and the shear caused by the primary not only produces a caustic but also makes the magnification contour elongated along the primary-planet axis. The elongated magnification contour implies that the light curves of these planetary events are generally asymmetric, and thus the asymmetry can be used to distinguish the events from those produced by free-floating planets. The asymmetry can be noticed from the overall shape of the light curve and thus can hardly be missed unlike the very short duration central perturbation caused by the caustic. In addition, the asymmetry occurs regardless of the event magnification, and thus the bound nature of the planet can be identified for majority of these events. The close approximation of the lensing light curve to that of the Chang-Refsdal lensing implies that the analysis of the light curve yields only the information about the projected separation between the host star and the planet.

  13. CHARACTERIZING LOW-MASS BINARIES FROM OBSERVATION OF LONG-TIMESCALE CAUSTIC-CROSSING GRAVITATIONAL MICROLENSING EVENTS

    SciTech Connect

    Shin, I.-G.; Han, C.; Choi, J.-Y.; Udalski, A.; Szymanski, M. K.; Kubiak, M.; Soszynski, I.; Pietrzynski, G.; Poleski, R.; Ulaczyk, K.; Pietrukowicz, P.; Kozlowski, S.; Wyrzykowski, L.; Sumi, T.; Gould, A.; Skowron, J.; Bozza, V.; Dominik, M.; Horne, K.; Fouque, P.; Collaboration: OGLE Collaboration; MOA Collaboration; RoboNet Collaboration; MiNDSTEp Consortium; muFUN Collaboration; PLANET Collaboration; and others

    2012-08-20

    Despite the astrophysical importance of binary star systems, detections are limited to those located in small ranges of separations, distances, and masses and thus it is necessary to use a variety of observational techniques for a complete view of stellar multiplicity across a broad range of physical parameters. In this paper, we report the detections and measurements of two binaries discovered from observations of microlensing events MOA-2011-BLG-090 and OGLE-2011-BLG-0417. Determinations of the binary masses are possible by simultaneously measuring the Einstein radius and the lens parallax. The measured masses of the binary components are 0.43 M{sub Sun} and 0.39 M{sub Sun} for MOA-2011-BLG-090 and 0.57 M{sub Sun} and 0.17 M{sub Sun} for OGLE-2011-BLG-0417 and thus both lens components of MOA-2011-BLG-090 and one component of OGLE-2011-BLG-0417 are M dwarfs, demonstrating the usefulness of microlensing in detecting binaries composed of low-mass components. From modeling of the light curves considering full Keplerian motion of the lens, we also measure the orbital parameters of the binaries. The blended light of OGLE-2011-BLG-0417 comes very likely from the lens itself, making it possible to check the microlensing orbital solution by follow-up radial-velocity observation. For both events, the caustic-crossing parts of the light curves, which are critical for determining the physical lens parameters, were resolved by high-cadence survey observations and thus it is expected that the number of microlensing binaries with measured physical parameters will increase in the future.

  14. Reevaluating the feasibility of ground-based Earth-mass microlensing planet detections

    SciTech Connect

    Jung, Youn Kil; Park, Hyuk; Han, Cheongho; Hwang, Kyu-Ha; Shin, In-Gu; Choi, Joon-Young

    2014-05-10

    An important strength of the microlensing method to detect extrasolar planets is its high sensitivity to low-mass planets. However, many believe that microlensing detections of Earth-mass planets from ground-based observation would be difficult because of limits set by finite-source effects. This view comes from the previous estimation of planet detection probability based on the fractional deviation of planetary signals; however, a proper probability estimation is required when considering the source brightness, which is directly related to the photometric precision. In this paper, we reevaluate the feasibility of low-mass planet detections by considering photometric precision for different populations of source stars. From this, we find that the contribution of improved photometric precision to the planetary signal of a giant-source event is large enough to compensate for the decrease in magnification excess caused by finite-source effects. As a result, we conclude that giant-source events are suitable targets for Earth-mass planet detections with significantly higher detection probability than events involved with source stars of smaller radii, and we predict that Earth-mass planets could be detected by prospective high-cadence surveys.

  15. Signatures of rotating binaries in microlensing experiments

    NASA Astrophysics Data System (ADS)

    Nucita, A. A.; Giordano, M.; De Paolis, F.; Ingrosso, G.

    2014-03-01

    Gravitational microlensing offers a powerful method with which to probe a variety of binary-lens systems, as the binarity of the lens introduces deviations from the typical (single-lens) Paczyński behaviour in the event light curves. Generally, a static binary lens is considered to fit the observed light curve and, when the orbital motion is taken into account, an oversimplified model is usually employed. In this paper, we treat the binary-lens motion in a realistic way and focus on simulated events that are fitted well by a Paczyński curve. We show that an accurate timing analysis of the residuals (calculated with respect to the best-fitting Paczyński model) is usually sufficient to infer the orbital period of the binary lens. It goes without saying that the independently estimated period may be used to further constrain the orbital parameters obtained by the best-fitting procedure, which often gives degenerate solutions. We also present a preliminary analysis of the event OGLE-2011-BLG-1127 / MOA-2011-BLG-322, which has been recognized to be the result of a binary lens. The period analysis results in a periodicity of ≃12 d, which confirms the oscillation of the observed data around the best-fitting model. The estimated periodicity is probably associated with an intrinsic variability of the source star, and therefore there is an opportunity to use this technique to investigate either the intrinsic variability of the source or the effects induced by the binary-lens orbital motion.

  16. Seismology and space-based geodesy

    NASA Technical Reports Server (NTRS)

    Tralli, David M.; Tajima, Fumiko

    1993-01-01

    The potential of space-based geodetic measurement of crustal deformation in the context of seismology is explored. The achievements of seismological source theory and data analyses, mechanical modeling of fault zone behavior, and advances in space-based geodesy are reviewed, with emphasis on realizable contributions of space-based geodetic measurements specifically to seismology. The fundamental relationships between crustal deformation associated with an earthquake and the geodetically observable data are summarized. The response and spatial and temporal resolution of the geodetic data necessary to understand deformation at various phases of the earthquake cycle is stressed. The use of VLBI, SLR, and GPS measurements for studying global geodynamics properties that can be investigated to some extent with seismic data is discussed. The potential contributions of continuously operating strain monitoring networks and globally distributed geodetic observatories to existing worldwide modern digital seismographic networks are evaluated in reference to mutually addressable problems in seismology, geophysics, and tectonics.

  17. Requirements for Space-Based Wind Lidar

    NASA Technical Reports Server (NTRS)

    Atlas, Robert M.; Einaudi, Franco (Technical Monitor)

    2002-01-01

    Global wind profiles are needed for a wide range of meteorological applications. Since the 1980's, observing system simulation experiments have been conducted in order to evaluate the potential impact of space-based wind profiler data on numerical weather prediction, and to evaluate trade-offs in lidar design. These experiments indicated tremendous potential for satellite lidar observations to improve atmospheric analyses and forecasts. More recent experiments are aimed at assessing the precise requirements for space-based lidar wind profile data and to evaluate the potential for alternative technologies. At the workshop, OSSE methodology, and results from experiments conducted at the DAO to the define requirements for space-based lidar wind will be presented.

  18. Gravitational Microlensing in Modified Gravity Theories - Inverse-Square Theorem

    NASA Astrophysics Data System (ADS)

    Asada, H.

    2011-02-01

    Microlensing studies are usually based on the lens equation that is valid only to the first order in the gravitational constant G and lens mass M. We consider corrections to the conventional lens equation in terms of differentiable functions, so that they can express not only the second-order effects of GM in general relativity but also modified gravity theories. As a generalization of Ebina et al. (Prog. Theor. Phys. 104 (2000), 1317), we show that, provided that the spacetime is static, spherically symmetric and asymptotically flat, the total amplification by microlensing remains unchanged at the linear order of the correction to the deflection angle, if and only if the correction takes a particular form as the inverse square of the impact parameter, whereas the magnification factor for each image is corrected. It is concluded that the light curve shape by microlensing is inevitably changed and will thus allow us to probe modified gravity, unless a modificati on to the deflection angle takes the particular form. No systematic deviation in microlensing observations has been reported. For instance, therefore, the Yukawa-type correction is constrained as the characteristic length > 10^{14} m.

  19. Compact IR laser for calibration of space based sensors

    SciTech Connect

    Kietrick, K.M.; Dezenberg, G.; Hamilton, C.; Vann, J.; LaSala, J.

    1996-04-17

    An Er:YAG laser, operating at 2.94 microns, has been developed for in-theater calibration of space based infrared sensors. The laser is used to illuminate a spaceborne sensor focal plane from a surveyed ground reference point. The known reference point is compared to the laser position reported by the sensor, and boresight corrections are made. The Er:YAG laser is side pumped by a InGaAs diode array and is tuned to an atmospheric microwindow with and intracavity etalon. This technology is being directly applied to meet Army requirements for enhanced deep strike targeting information supplied to theater weapons systems.

  20. Effect of Binary Source Companions on the Microlensing Optical Depth Determination toward the Galactic Bulge Field

    NASA Astrophysics Data System (ADS)

    Han, Cheongho

    2005-11-01

    Currently, gravitational microlensing survey experiments toward the Galactic bulge field use two different methods of minimizing the blending effect for the accurate determination of the optical depth τ. One is measuring τ based on clump giant (CG) source stars, and the other is using ``difference image analysis'' (DIA) photometry to measure the unblended source flux variation. Despite the expectation that the two estimates should be the same assuming that blending is properly considered, the estimates based on CG stars systematically fall below the DIA results based on all events with source stars down to the detection limit. Prompted by the gap, we investigate the previously unconsidered effect of companion-associated events on τ determination. Although the image of a companion is blended with that of its primary star and thus not resolved, the event associated with the companion can be detected if the companion flux is highly magnified. Therefore, companions work effectively as source stars to microlensing, and thus the neglect of them in the source star count could result in a wrong τ estimation. By carrying out simulations based on the assumption that companions follow the same luminosity function as primary stars, we estimate that the contribution of the companion-associated events to the total event rate is ~5fbi% for current surveys and can reach up to ~6fbi% for future surveys monitoring fainter stars, where fbi is the binary frequency. Therefore, we conclude that the companion-associated events comprise a nonnegligible fraction of all events. However, their contribution to the optical depth is not large enough to explain the systematic difference between the optical depth estimates based on the two different methods.

  1. Microlensing of sub-parsec massive binary black holes in lensed QSOs: Light curves and size-wavelength relation

    SciTech Connect

    Yan, Chang-Shuo; Lu, Youjun; Mao, Shude; Yu, Qingjuan; Wambsganss, Joachim E-mail: luyj@nao.cas.cn

    2014-04-01

    Sub-parsec binary massive black holes (BBHs) have long been thought to exist in many QSOs but remain observationally elusive. In this paper, we propose a novel method to probe sub-parsec BBHs through microlensing of lensed QSOs. If a QSO hosts a sub-parsec BBH in its center, it is expected that the BBH is surrounded by a circumbinary disk, each component of the BBH is surrounded by a small accretion disk, and a gap is opened by the secondary component in between the circumbinary disk and the two small disks. Assuming such a BBH structure, we generate mock microlensing light curves for some QSO systems that host BBHs with typical physical parameters. We show that microlensing light curves of a BBH QSO system at the infrared-optical-UV bands can be significantly different from those of corresponding QSO system with a single massive black hole (MBH), mainly because of the existence of the gap and the rotation of the BBH (and its associated small disks) around the center of mass. We estimate the half-light radii of the emission region at different wavelengths from mock light curves and find that the obtained half-light radius versus wavelength relations of BBH QSO systems can be much flatter than those of single MBH QSO systems at a wavelength range determined by the BBH parameters, such as the total mass, mass ratio, separation, accretion rates, etc. The difference is primarily due to the existence of the gap. Such unique features on the light curves and half-light radius-wavelength relations of BBH QSO systems can be used to select and probe sub-parsec BBHs in a large number of lensed QSOs to be discovered by current and future surveys, including the Panoramic Survey Telescope and Rapid Response System, the Large Synoptic Survey telescope, and Euclid.

  2. Improved Predictions of Kepler Microlensing Rates for Primordial Black Hole Dark Matter

    NASA Astrophysics Data System (ADS)

    Cieplak, Agnieszka; Griest, K.

    2013-01-01

    Primordial Black Holes (PBHs) remain a viable Dark Matter (DM) candidate of the Standard Model of Particle Physics. Previously, we have proposed a new method to constrain the remaining PBH DM mass range using microlensing of Kepler source stars, with the possibility of closing up to 40% of the remaining mass window. Here we re-address this analysis using a more accurate treatment of the distribution of the source stars, including limb-darkening as well as reflecting a more accurate number of variable stars. Including the extended Kepler mission the theoretically detectable PBH DM mass range could be extended down to 2*10^-10 solar masses. We address the possible PBH parameters that could be detected if such an event would be observed as well as possible improvements for future survey satellite missions.

  3. A New Method of Detecting Primordial Black Hole Dark Matter using Microlensing

    NASA Astrophysics Data System (ADS)

    Cieplak, Agnieszka; Griest, K.; Lehner, M. J.

    2012-01-01

    Primordial Black Holes (PBHs) are the only remaining Dark Matter (DM) candidate of the Standard Model of Particle Physics. We present a new method of constraining up to 40% of the remaining mass range of the PBH DM using microlensing of stars targeted by NASA's Kepler mission. Kepler's exceptional photometric precision and finite-source effects allow for a higher microlensing rate than previously thought. We introduce a new formalism with these effects for the optical depth and microlensing rate.

  4. Overview of characterization and metrology techniques for microlenses and microlens arrays

    NASA Astrophysics Data System (ADS)

    Kim, Myun-Sik; Allegre, Lisa; Sunarjo, Jonathan; Noell, Wilfried; Voelkel, Reinhard

    2015-05-01

    We review various metrology techniques for the characterization of refractive microlenses and microlens arrays (MLAs). The limitations and strength of each technique are analyzed. The goal is to obtain more stable and repeatable metrology routines for micro-optics manufacturing. This analysis comprises both techniques for the characterization of individual microlenses and the analysis of a very large number of microlenses in array configurations. Metrology of spherical and aspherical lens profiles, surface properties, aberrations, Strehl ratio, and focal properties will be presented.

  5. Space-based monitoring of ground deformation

    NASA Astrophysics Data System (ADS)

    Nobakht Ersi, Fereydoun; Safari, Abdolreza; Gamse, Sonja

    2016-07-01

    Ground deformation monitoring is valuable to understanding of the behaviour of natural phenomena. Space-Based measurement systems such as Global Positioning System are useful tools for continuous monitoring of ground deformation. Ground deformation analysis based on space geodetic techniques have provided a new, more accurate, and reliable source of information for geodetic positioning which is used to detect deformations of the Ground surface. This type of studies using displacement fields derived from repeated measurments of space-based geodetic networks indicates how crucial role the space geodetic methods play in geodynamics. The main scope of this contribution is to monitor of ground deformation by obtained measurements from GPS sites. We present ground deformation analysis in three steps: a global congruency test on daily coordinates of permanent GPS stations to specify in which epochs deformations occur, the localization of the deformed GPS sites and the determination of deformations.

  6. Adaptive control of space based robot manipulators

    NASA Technical Reports Server (NTRS)

    Walker, Michael W.; Wee, Liang-Boon

    1991-01-01

    For space based robots in which the base is free to move, motion planning and control is complicated by uncertainties in the inertial properties of the manipulator and its load. A new adaptive control method is presented for space based robots which achieves globally stable trajectory tracking in the presence of uncertainties in the inertial parameters of the system. A partition is made of the fifteen degree of freedom system dynamics into two parts: a nine degree of freedom invertible portion and a six degree of freedom noninvertible portion. The controller is then designed to achieve trajectory tracking of the invertible portion of the system. This portion consist of the manipulator joint positions and the orientation of the base. The motion of the noninvertible portion is bounded, but unpredictable. This portion consist of the position of the robot's base and the position of the reaction wheel.

  7. A space-based microwave radar concept

    NASA Technical Reports Server (NTRS)

    Chakraborty, D.

    1992-01-01

    A space-based microwave radar (SBR) concept is defined using a tether trans-receive antenna supported between two gravity gradient low earth-orbiting satellites. A cluster of four tether antennas each of 6 km maximum length and 1.5 km separation between tethers constitutes a radar. A system of eight to eleven such clusters constitutes the overall radar scheme which will cover approximately one third of the earth surface for detecting sea-based targets. Issues identified are the array structure, coherence of tethered arrays, grating lobe energy clamping, clutter effects, communications, system requirements and the overall radar system concept including stability considerations. This paper presents the base-line definition of an alternate space-based radar scheme.

  8. Toward a Space based Gravitational Wave Observatory

    NASA Technical Reports Server (NTRS)

    Stebbins, Robin T.

    2015-01-01

    A space-based GW observatory will produce spectacular science. The LISA mission concept: (a) Long history, (b) Very well-studied, including de-scopes, (c) NASAs Astrophysics Strategic Plan calls for a minority role in ESAs L3 mission opportunity. To that end, NASA is Participating in LPF and ST7 Developing appropriate technology for a LISA-like mission Preparing to seek an endorsement for L3 participation from the 2020 decadal review.

  9. The origin of the microlensing events observed towards the LMC and the stellar counterpart of the Magellanic stream

    NASA Astrophysics Data System (ADS)

    Besla, Gurtina; Hernquist, Lars; Loeb, Abraham

    2013-01-01

    We introduce a novel theoretical model to explain the longstanding puzzle of the nature of the microlensing events reported towards the Large Magellanic Cloud (LMC) by the massive compact halo object (MACHO) and Optical Gravitational Lensing Experiment (OGLE) collaborations. We propose that a population of tidally stripped stars from the Small Magellanic Cloud (SMC) located ˜4-10 kpc behind a lensing population of LMC disc stars can naturally explain the observed event durations (17-71 d), event frequencies and spatial distribution of the reported events. Differences in the event frequencies reported by the OGLE (˜0.33 yr-1) and MACHO (˜1.75 yr-1) surveys appear to be naturally accounted for by their different detection efficiencies and sensitivity to faint sources. The presented models of the Magellanic System were constructed without prior consideration of the microlensing implications. These results favour a scenario for the interaction history of the Magellanic Clouds, wherein the Clouds are on their first infall towards the Milky Way and the SMC has recently collided with the LMC 100-300 Myr ago, leading to a large number of faint sources distributed non-uniformly behind the LMC disc. In contrast to self-lensing models, microlensing events are also expected to occur in fields off the LMC's stellar bar since the stellar debris is not expected to be concentrated in the bar region. This scenario leads to a number of observational tests: the sources are low-metallicity SMC stars; they exhibit high velocities relative to LMC disc stars that may be detectable via proper motion studies and, most notably, there should exist a stellar counterpart to the gaseous Magellanic Stream and Bridge with a V-band surface brightness of >34 mag arcsec-2. In particular, the stellar Bridge should contain enough RR Lyrae stars to be detected by the ongoing OGLE survey of this region.

  10. OGLE-2011-BLG-0417: A RADIAL VELOCITY TESTBED FOR MICROLENSING

    SciTech Connect

    Gould, Andrew; Yee, Jennifer C.; Shin, In-Gu; Han, Cheongho; Udalski, Andrzej

    2013-05-10

    Microlensing experiments are returning increasingly detailed information about the planetary and binary systems that are being detected, far beyond what was originally expected. In several cases the lens mass and distance are measured, and a few very special cases have yielded complete eight-parameter Kepler solutions, i.e., the masses of both components, five Kepler invariants, and the phase. We identify one such case that is suitable for a precision test that could be carried out by comparing Doppler radial velocity (RV) measurements with the predictions from the microlensing solution. The lens primary is reasonably bright (I = 16.3, V = 18.2) and is expected to have a relatively large RV semi-amplitude (K {approx} 6.35 km s{sup -1}).

  11. Using Microlensing Maps to Determine Spin of Black Holes

    NASA Astrophysics Data System (ADS)

    Guerra, Juan; O'Dowd, Matthew; Webster, Rachel L.; Labrie, Kathleen; Ford, Saavik; McKernan, Barry; Bate, Nicholas

    2016-01-01

    Quasar accretion disks are expected to have central cavities corresponding to their Supermassive Black Hole's (SMBH) Innermost Stable Circular Orbit (ISCO). Cavity size depends on black hole mass, spin, and relative accretion direction, and so given a mass estimate, measurement of ISCO size constrains SMBH spin; such a measurement would be invaluable in determining the role of spin in AGN emission processes, and also in understanding SMBH growth by constraining the magnitude of accretion events. While not spatially resolvable, ISCO cavities are expected to leave a signature on the light curves of gravitationally lensed quasars when they undergo a strong microlensing event. Using simulations of these events for Q2237+030, the Einstein Cross, we have shown that ISCO width can be measured using current observatories if monitored through a cusp-crossing microlensing event.

  12. Broadband Plasmonic Microlenses based on Patches of Nanoholes

    PubMed Central

    Gao, Hanwei; Hyun, Jerome K.; Lee, Min Hyung; Yang, Jiun-Chan; Lauhon, Lincoln J.; Odom, Teri W.

    2010-01-01

    This paper reports a new type of diffractive microlens based on finite-areas of 2D arrays of circular nanoholes (patches). The plasmonic microlenses can focus single wavelengths of light across the entire visible spectrum as well as broadband white light with little divergence. The focal length is determined primarily by the overall size of the patch and is tolerant to significant changes in patch substructure, including lattice geometry and local order of the circular nanoholes. The optical throughput, however, depends sensitively on the patch substructure and is determined by the wavelengths of surface plasmon resonances. This simple diffractive lens design enables millions of broadband plasmonic microlenses to be fabricated in parallel using soft nanolithographic techniques. PMID:20839781

  13. A method for the microlensed flux variance of QSOs

    NASA Astrophysics Data System (ADS)

    Goodman, Jeremy; Sun, Ai-Lei

    2014-06-01

    A fast and practical method is described for calculating the microlensed flux variance of an arbitrary source by uncorrelated stars. The required inputs are the mean convergence and shear due to the smoothed potential of the lensing galaxy, the stellar mass function, and the absolute square of the Fourier transform of the surface brightness in the source plane. The mathematical approach follows previous authors but has been generalized, streamlined, and implemented in publicly available code. Examples of its application are given for Dexter and Agol's inhomogeneous-disc models as well as the usual Gaussian sources. Since the quantity calculated is a second moment of the magnification, it is only logarithmically sensitive to the sizes of very compact sources. However, for the inferred sizes of actual quasi-stellar objects (QSOs), it has some discriminatory power and may lend itself to simple statistical tests. At the very least, it should be useful for testing the convergence of microlensing simulations.

  14. Forward electrohydrodynamic inkjet printing of optical microlenses on microfluidic devices.

    PubMed

    Vespini, V; Coppola, S; Todino, M; Paturzo, M; Bianco, V; Grilli, S; Ferraro, P

    2016-01-21

    We report a novel method for direct printing of viscous polymers based on a pyro-electrohydrodynamic repulsion system capable of overcoming limitations on the material type, geometry and thickness of the receiving substrate. In fact, the results demonstrate that high viscosity polymers can be easily manipulated for optical functionalizing of lab-on-a-chip devices through demonstration of direct printing of polymer microlenses onto microfluidic chips and optical fibre terminations. The present system has great potential for applications from biomolecules to nano-electronics. Moreover, in order to prove the effectiveness of the system, the optical performance of such microlenses has been characterized by testing their imaging capabilities when the fibroblast cells were allowed to flow inside the microfluidic channel, showing one of their possible applications on-board a LoC platform. PMID:26660423

  15. Microlensing in the Q0957 + 561 gravitational mirage

    SciTech Connect

    Schild, R.E.; Smith, R.C. )

    1991-03-01

    Analysis of the 10 yr record from monitoring the continuum brightness of Q0957 + 561 A, B shows a systematic increase of the B relative to the A component. The B brightness has leveled off in the last 2 yr at a value 32 percent higher than would be predicted from the ratio of Mg II 2798 A emission line strengths. This is taken to be the signature of microlensing by a star or stars in the lens galaxy. 11 refs.

  16. Gravitational Microlensing as a probe of Quasar Structure

    NASA Astrophysics Data System (ADS)

    Floyd, David

    2011-01-01

    Gravitational microlensing provides information at the micro-to-nano arcsecond scale necessary to probe the structure of the central engine of quasars. We can now determine the radius of the broad line emitting regions, and measure the temperature profile of the continuum emitting region using single-epoch observations. I will present X-shooter spectroscopy that provides new insight into the accretion mechanism, and the structure of the broad line region.

  17. Fabrication, replication, and characterization of microlenses for optofluidic applications

    NASA Astrophysics Data System (ADS)

    Jonusauskas, L.; Žukauskas, A.; Danilevicius, P.; Malinauskas, M.

    2013-03-01

    Here we report Direct Laser Writing (DLW) based fabrication of aspheric microlenses out of hybrid organicinorganic photopolymer ORMOSIL. Using the advantages of the flexible manufacturing technique the produced microlenses are embedded inside a fluidic channel. Applying the soft-lithography molding technique the structures are transferred to the elastomer PDMS and hydrogel PEG-DA-258 materials. Measurements show that such replica transferring can reproduce the initial structures into other materials on desired substrates with no noticeable losses of quality. Furthermore, it makes femtosecond laser redundant once the original structure is made. The embedded structures are immersed into several liquid media (acetone, methanol) and the focusing performance corresponding to the change of the optical path length of the microlenses is obtained. It well matches with the estimated values. In conclusion, we report a combination of laser fabrication and replication methods as an efficient way to produce optofluidic components, which can be used for light based sensing, trapping or other applications such as MOEMS devices.

  18. Predictions for microlensing planetary events from core accretion theory

    SciTech Connect

    Zhu, Wei; Mao, Shude; Penny, Matthew; Gould, Andrew; Gendron, Rieul

    2014-06-10

    We conduct the first microlensing simulation in the context of a planet formation model. The planet population is taken from the Ida and Lin core accretion model for 0.3 M {sub ☉} stars. With 6690 microlensing events, we find that for a simplified Korea Microlensing Telescopes Network (KMTNet), the fraction of planetary events is 2.9%, out of which 5.5% show multiple-planet signatures. The numbers of super-Earths, super-Neptunes, and super-Jupiters detected are expected to be almost equal. Our simulation shows that high-magnification events and massive planets are favored by planet detections, which is consistent with previous expectation. However, we notice that extremely high-magnification events are less sensitive to planets, which is possibly because the 10 minute sampling of KMTNet is not intensive enough to capture the subtle anomalies that occur near the peak. This suggests that while KMTNet observations can be systematically analyzed without reference to any follow-up data, follow-up observations will be essential in extracting the full science potential of very high magnification events. The uniformly high-cadence observations expected for KMTNet also result in ∼55% of all detected planets not being caustic crossing, and more low-mass planets even down to Mars mass being detected via planetary caustics. We also find that the distributions of orbital inclinations and planet mass ratios in multiple-planet events agree with the intrinsic distributions.

  19. Discovery of a Jupiter/Saturn analog with gravitational microlensing.

    PubMed

    Gaudi, B S; Bennett, D P; Udalski, A; Gould, A; Christie, G W; Maoz, D; Dong, S; McCormick, J; Szymanski, M K; Tristram, P J; Nikolaev, S; Paczynski, B; Kubiak, M; Pietrzynski, G; Soszynski, I; Szewczyk, O; Ulaczyk, K; Wyrzykowski, L; Depoy, D L; Han, C; Kaspi, S; Lee, C-U; Mallia, F; Natusch, T; Pogge, R W; Park, B-G; Abe, F; Bond, I A; Botzler, C S; Fukui, A; Hearnshaw, J B; Itow, Y; Kamiya, K; Korpela, A V; Kilmartin, P M; Lin, W; Masuda, K; Matsubara, Y; Motomura, M; Muraki, Y; Nakamura, S; Okumura, T; Ohnishi, K; Rattenbury, N J; Sako, T; Saito, To; Sato, S; Skuljan, L; Sullivan, D J; Sumi, T; Sweatman, W L; Yock, P C M; Albrow, M D; Allan, A; Beaulieu, J-P; Burgdorf, M J; Cook, K H; Coutures, C; Dominik, M; Dieters, S; Fouqué, P; Greenhill, J; Horne, K; Steele, I; Tsapras, Y; Chaboyer, B; Crocker, A; Frank, S; Macintosh, B

    2008-02-15

    Searches for extrasolar planets have uncovered an astonishing diversity of planetary systems, yet the frequency of solar system analogs remains unknown. The gravitational microlensing planet search method is potentially sensitive to multiple-planet systems containing analogs of all the solar system planets except Mercury. We report the detection of a multiple-planet system with microlensing. We identify two planets with masses of approximately 0.71 and approximately 0.27 times the mass of Jupiter and orbital separations of approximately 2.3 and approximately 4.6 astronomical units orbiting a primary star of mass approximately 0.50 solar mass at a distance of approximately 1.5 kiloparsecs. This system resembles a scaled version of our solar system in that the mass ratio, separation ratio, and equilibrium temperatures of the planets are similar to those of Jupiter and Saturn. These planets could not have been detected with other techniques; their discovery from only six confirmed microlensing planet detections suggests that solar system analogs may be common. PMID:18276883

  20. Parallax and Orbital Effects in Astrometric Microlensing with Binary Sources

    NASA Astrophysics Data System (ADS)

    Nucita, A. A.; De Paolis, F.; Ingrosso, G.; Giordano, M.; Manni, L.

    2016-06-01

    In gravitational microlensing, binary systems may act as lenses or sources. Identifying lens binarity is generally easy, in particular in events characterized by caustic crossing since the resulting light curve exhibits strong deviations from a smooth single-lensing light curve. In contrast, light curves with minor deviations from a Paczyński behavior do not allow one to identify the source binarity. A consequence of gravitational microlensing is the shift of the position of the multiple image centroid with respect to the source star location — the so-called astrometric microlensing signal. When the astrometric signal is considered, the presence of a binary source manifests with a path that largely differs from that expected for single source events. Here, we investigate the astrometric signatures of binary sources taking into account their orbital motion and the parallax effect due to the Earth’s motion, which turn out not to be negligible in most cases. We also show that considering the above-mentioned effects is important in the analysis of astrometric data in order to correctly estimate the lens-event parameters.

  1. Quasar-microlensing versus star-microlensing evidence of small-planetary-mass objects as the dominant inner-halo galactic dark matter

    NASA Astrophysics Data System (ADS)

    Gibson, Carl H.; Schild, Rudolph E.

    2011-11-01

    We examine recent results of two kinds of microlensing experiments intended to detect galactic dark matter objects, and we suggest that the lack of short period star-microlensing events observed for stars near the Galaxy does not preclude either the "rogue planets" identified from quasar-microlensing by Schild 1996 as the missing-mass of a lens galaxy, or the "Primordial Fog Particles" (PFPs) in Proto-Globular-star-Cluster (PGC) clumps predicted by Gibson 1996 - 2000 as the dominant inner-halo galactic dark matter component from a new hydrodynamic gravitational structure formation theory. We point out that hydro-gravitational processes acting on a massive population of such micro-brown-dwarfs in their nonlinear accretional cascades to form stars gives intermittent lognormal number density np distributions for the PFPs within the PGC gas-stabilized-clumps. Hence, star-microlensing searches that focus on a small fraction of the sky assuming a uniform distribution for np are subject to vast underestimates of the mean ⟨np⟩mean. Sparse independent samples give modes 10-4 - 10-6 smaller than means of the highly skewed lognormal distributions expected. Quasar-microlensing searches with higher optical depths are less affected by np intermittency. We attempt to reconcile the results of the star-microlensing and quasar-microlensing studies, with particular reference to the necessarily hydrogenous and primordial small-planetary-mass range. We conclude that star microlensing searches cannot exclude and are unlikely even to detect these low-mass candidate-galactic-dark-matter-objects so easily observed by quasar-microlensing and so robustly predicted by the new theory.

  2. The microlensing event rate and optical depth toward the galactic bulge from MOA-II

    SciTech Connect

    Sumi, T.; Suzuki, D.; Wada, K.; Collaboration: MOA Collaboratoin; and others

    2013-12-01

    We present measurements of the microlensing optical depth and event rate toward the Galactic Bulge (GB) based on two years of the MOA-II survey. This sample contains ∼1000 microlensing events, with an Einstein radius crossing time of t {sub E} ≤ 200 days in 22 bulge fields covering ∼42 deg{sup 2} between –5° < l < 10° and –7° < b < –1°. Our event rate and optical depth analysis uses 474 events with well-defined microlensing parameters. In the central fields with |l| < 5°, we find an event rate of Γ = [2.39 ± 1.1]e {sup [0.60±0.05](3–|b|)} × 10{sup –5} star{sup –1} yr{sup –1} and an optical depth (for events with t {sub E} ≤ 200 days) of τ{sub 200} = [2.35 ± 0.18]e {sup [0.51±0.07](3–|b|)} × 10{sup –6} for the 427 events, using all sources brighter than I{sub s} ≤ 20 mag. The distribution of observed fields is centered at (l, b) = (0.°38, –3.°72). We find that the event rate is maximized at low latitudes and a longitude of l ≈ 1°. For the 111 events in 3.2 deg{sup 2} of the central GB at |b| ≤ 3.°0 and 0.°0 ≤ l ≤ 2.°0, centered at (l, b) = (0.°97, –2.°26), we find Γ=4.57{sub −0.46}{sup +0.51}×10{sup −5} star{sup –1} yr{sup –1} and τ{sub 200}=3.64{sub −0.45}{sup +0.51}×10{sup −6}. We also consider a red clump giant (RCG) star sample with I{sub s} < 17.5, and we find that the event rate for the RCG sample is slightly lower than but consistent with the all-source event rate. The main difference is the lack of long duration events in the RCG sample due to a known selection effect. Our results are consistent with previous optical depth measurements, but they are somewhat lower than previous all-source measurements, and slightly higher than previous RCG optical depth measurements. This suggests that the previously observed difference in optical depth measurements between all-source and RCG samples may largely be due to statistical fluctuations. These event rate measurements toward the central GB

  3. Space-based Tests of Relativistic Gravitation

    NASA Astrophysics Data System (ADS)

    Turyshev, Vyacheslav G.

    Since its initial publication, Einstein's general theory of relativity had been tested to a very high precision and presently is considered to be the standard theory of gravitation, especially when the phenomena in astrophysics, cosmology, and fundamental physics are concerned. As such, this theory has many practically important applications including spacecraft navigation, relativistic geodesy, time transfer, etc. Here we discuss the foundations of general relativity, present its current empirical status, and highlight the need for the new generation of high-accuracy tests. We present some space-based gravitational experiments and discuss anticipated advances in our understanding of the fundamental laws of nature.

  4. Space Based Range Demonstration and Certification (SBRDC)

    NASA Technical Reports Server (NTRS)

    Sakahara, Robert

    2005-01-01

    This viewgraph presentation describes the development, utilization and testing of technologies for range safety and range user systems. The contents include: 1) Space Based Range (SBR) Goals and Objectives; 2) Today s United States Range; 3) Future Range; 4) Another Vision for the Future Range; 5) STARS Project Goals; 6) STARS Content; 7) STARS Configuration Flight Demonstrations 1 & 2; 8) Spaceport And Range Technologies STARS Objectives and Results; 9) Spaceport And Range Technologies STARS FD2 Objectives; 10) Range Safety Hardware; 11) Range User Hardware; and 12) Past/Future Flight Demo Plans

  5. Space transfer vehicles and space basing

    NASA Technical Reports Server (NTRS)

    Kelley, Joe

    1991-01-01

    The topics covered include the following: (1) space basing agenda; (2) mission scenario 4E-5B, crew and Lunar Excursion Vehicle (LEV) delivery; (3) final concept candidate, crew concept 4E-2B; (4) space transfer vehicle (STV) concept 4E-5B; (5) configuration summary for crew concept 4E-5B; (6) configuration definition for crew concept 4E-5B; (7) low earth orbit node assembly and checkout operations; (8) criteria for operation objectives; (9) LTV and STV main engines; (10) Space Station Freedom impacts; (11) aerobrakes; and (12) on orbit operations. This document is presented in viewgraph form.

  6. Imprints of the quasar structure in time-delay light curves: Microlensing-aided reverberation mapping

    NASA Astrophysics Data System (ADS)

    Sluse, D.; Tewes, M.

    2014-11-01

    The advent of large area photometric surveys has raised a great deal of interest in the possibility of using broadband photometric data, instead of spectra, to measure the size of the broad line region of active galactic nuclei. We describe here a new method that uses time-delay lensed quasars where one or several images are affected by microlensing due to stars in the lensing galaxy. Because microlensing decreases (or increases) the flux of the continuum compared to the broad line region, it changes the contrast between these two emission components. We show that this effect can be used to effectively disentangle the intrinsic variability of those two regions, offering the opportunity to perform reverberation mapping based on single-band photometric data. Based on simulated light curves generated using a damped random walk model of quasar variability, we show that measurement of the size of the broad line region can be achieved using this method, provided one spectrum has been obtained independently during the monitoring. This method is complementary to photometric reverberation mapping and could also be extended to multi-band data. Because the effect described above produces a variability pattern in difference light curves between pairs of lensed images that is correlated with the time-lagged continuum variability, it can potentially produce systematic errors in measurement of time delays between pairs of lensed images. Simple simulations indicate that time-delay measurement techniques that use a sufficiently flexible model for the extrinsic variability are not affected by this effect and produce accurate time delays.

  7. MERLIN: a space-based methane monitor

    NASA Astrophysics Data System (ADS)

    Stephan, C.; Alpers, M.; Millet, B.; Ehret, G.; Flamant, P.; Deniel, C.

    2011-10-01

    Methane is a powerful greenhouse gas. The radiative forcing caused by methane contributes significantly to the warming of the atmosphere. To better understand the complex global Methane Cycle, it is necessary to apply space-based measurements techniques in order to obtain global coverage at high precision The Methane Remote Sensing Lidar Mission (MERLIN) is a joint French-German cooperation on a micro satellite mission for space-based measurement of spatial and temporal gradients of atmospheric methane columns on a global scale. MERLIN will be the first Integrated Path Differential Absorption LIDAR for methane monitoring from space. In contrast to passive methane missions, the LIDAR instrument allows to retrieve methane fluxes at all-latitudes, allseasons and during night as it is not relying on sunlight. First scientific studies show a substantial reduction of the prior methane flux uncertainties in key observational regions when using synthetic MERLIN observations in the flux inversion experiments. Furthermore, MERLIN observations can help to quantify and verify in scientific credible way national emission reduction scenarios as formulated in the Kyoto protocol. This paper reports on the present status of MERLIN and gives an overview on the joint mission concept with the German LIDAR on the French satellite platform MYRIADE.

  8. Space-based Operations Grid Prototype

    NASA Technical Reports Server (NTRS)

    Bradford, Robert N.; Welch, Clara L.

    2003-01-01

    The Space based Operations Grid is intended to integrate the "high end" network services and compute resources that a remote payload investigator needs. This includes integrating and enhancing existing services such as access to telemetry, payload commanding, payload planning and internet voice distribution as well as the addition of services such as video conferencing, collaborative design, modeling or visualization, text messaging, application sharing, and access to existing compute or data grids. Grid technology addresses some of the greatest challenges and opportunities presented by the current trends in technology, i.e. how to take advantage of ever increasing bandwidth, how to manage virtual organizations and how to deal with the increasing threats to information technology security. We will discuss the pros and cons of using grid technology in space-based operations and share current plans for the prototype. It is hoped that early on the prototype can incorporate many of the existing as well as future services that are discussed in the first paragraph above to cooperating International Space Station Principle Investigators both nationally and internationally.

  9. ARTEMiS (Automated Robotic Terrestrial Exoplanet Microlensing Search): A possible expert-system based cooperative effort to hunt for planets of Earth mass and below

    NASA Astrophysics Data System (ADS)

    Dominik, M.; Horne, K.; Allan, A.; Rattenbury, N. J.; Tsapras, Y.; Snodgrass, C.; Bode, M. F.; Burgdorf, M. J.; Fraser, S. N.; Kerins, E.; Mottram, C. J.; Steele, I. A.; Street, R. A.; Wheatley, P. J.; Wyrzykowski, Ł.

    2008-03-01

    The technique of gravitational microlensing is currently unique in its ability to provide a sample of terrestrial exoplanets around both Galactic disk and bulge stars, allowing to measure their abundance and determine their distribution with respect to mass and orbital separation. Thus, valuable information for testing models of planet formation and orbital migration is gathered, constituting an important piece in the puzzle for the existence of life forms throughout the Universe. In order to achieve these goals in reasonable time, a well-coordinated effort involving a network of either 2m or 4×1m telescopes at each site is required. It could lead to the first detection of an Earth-mass planet outside the Solar system, and even planets less massive than Earth could be discovered. From April 2008, ARTEMiS (Automated Robotic Terrestrial Exoplanet Microlensing Search) is planned to provide a platform for a three-step strategy of survey, follow-up, and anomaly monitoring. As an expert system embedded in eSTAR (e-Science Telescopes for Astronomical Research), ARTEMiS will give advice for follow-up based on a priority algorithm that selects targets to be observed in order to maximize the expected number of planet detections, and will also alert on deviations from ordinary microlensing light curves by means of the SIGNALMEN anomaly detector. While the use of the VOEvent (Virtual Observatory Event) protocol allows a direct interaction with the telescopes that are part of the HTN (Heterogeneous Telescope Networks) consortium, additional interfaces provide means of communication with all existing microlensing campaigns that rely on human observers. The success of discovering a planet by microlensing critically depends on the availability of a telescope in a suitable location at the right time, which can mean within 10 min. To encourage follow-up observations, microlensing campaigns are therefore releasing photometric data in real time. On ongoing planetary anomalies, world

  10. Space-based Science Operations Grid Prototype

    NASA Technical Reports Server (NTRS)

    Bradford, Robert N.; Welch, Clara L.; Redman, Sandra

    2004-01-01

    Grid technology is the up and coming technology that is enabling widely disparate services to be offered to users that is very economical, easy to use and not available on a wide basis. Under the Grid concept disparate organizations generally defined as "virtual organizations" can share services i.e. sharing discipline specific computer applications, required to accomplish the specific scientific and engineering organizational goals and objectives. Grids are emerging as the new technology of the future. Grid technology has been enabled by the evolution of increasingly high speed networking. Without the evolution of high speed networking Grid technology would not have emerged. NASA/Marshall Space Flight Center's (MSFC) Flight Projects Directorate, Ground Systems Department is developing a Space-based Science Operations Grid prototype to provide to scientists and engineers the tools necessary to operate space-based science payloads/experiments and for scientists to conduct public and educational outreach. In addition Grid technology can provide new services not currently available to users. These services include mission voice and video, application sharing, telemetry management and display, payload and experiment commanding, data mining, high order data processing, discipline specific application sharing and data storage, all from a single grid portal. The Prototype will provide most of these services in a first step demonstration of integrated Grid and space-based science operations technologies. It will initially be based on the International Space Station science operational services located at the Payload Operations Integration Center at MSFC, but can be applied to many NASA projects including free flying satellites and future projects. The Prototype will use the Internet2 Abilene Research and Education Network that is currently a 10 Gb backbone network to reach the University of Alabama at Huntsville and several other, as yet unidentified, Space Station based

  11. Broadband Metallic Planar Microlenses in an Array: the Focusing Coupling Effect.

    PubMed

    Yu, Yiting; Wang, Ping; Zhu, Yechuan; Diao, Jinshuai

    2016-12-01

    The microlens arrays (MLAs) are widely utilized for various applications. However, when the lens size and the spacing between two adjacent microlenses are of the length scale of the working wavelength, the diffraction effect plays a vital role in the final focusing performance. We suggest a kind of broadband metallic planar microlenses, based on which the ultra-compact microlens arrays are also constructed. The focusing coupling effect revealing for such devices is then investigated in detail by using the finite-difference time-domain (FDTD) method, with the emphasis on the changing spacing between adjacent microlenses, the working wavelength, the diameter of microlenses, and the array size. The results show that a larger spacing, a larger lens size, a shorter wavelength, or a smaller array scale can lead to a weaker focusing coupling effect. This research provides an important technological reference to design an array of metallic planar microlenses with the well-controlled focusing performance. PMID:26922796

  12. Influence of TESG layer viscoelasticity on the imaging properties of microlenses

    NASA Astrophysics Data System (ADS)

    Vasiljević, Darko; Murić, Branka; Pantelić, Dejan; Panić, Bratimir

    2012-05-01

    Microlenses were produced by the irradiation of a layer of tot'hema and eosin sensitized gelatin (TESG) with laser light (second harmonic Nd:YAG, 532 nm). For this research, eight microlenses were written on a dog-bone-shaped TESG layer. After production, microlenses were uniaxially stretched on a tensile testing machine. Each microlens had different amounts of strain (0, 30, 60, 80, 120, 140, 180 and 240% strain). The influence of TESG layer extensibility on the imaging properties of microlenses was characterized by calculating the root mean square wavefront aberration, the modulation transfer function and the geometrical spot diagram. All microlenses had very good imaging properties and the microlens with 0% strain had diffraction-limited performance.

  13. Broadband Metallic Planar Microlenses in an Array: the Focusing Coupling Effect

    NASA Astrophysics Data System (ADS)

    Yu, Yiting; Wang, Ping; Zhu, Yechuan; Diao, Jinshuai

    2016-02-01

    The microlens arrays (MLAs) are widely utilized for various applications. However, when the lens size and the spacing between two adjacent microlenses are of the length scale of the working wavelength, the diffraction effect plays a vital role in the final focusing performance. We suggest a kind of broadband metallic planar microlenses, based on which the ultra-compact microlens arrays are also constructed. The focusing coupling effect revealing for such devices is then investigated in detail by using the finite-difference time-domain (FDTD) method, with the emphasis on the changing spacing between adjacent microlenses, the working wavelength, the diameter of microlenses, and the array size. The results show that a larger spacing, a larger lens size, a shorter wavelength, or a smaller array scale can lead to a weaker focusing coupling effect. This research provides an important technological reference to design an array of metallic planar microlenses with the well-controlled focusing performance.

  14. Space Based Gravitational Wave Observatories (SGOs)

    NASA Technical Reports Server (NTRS)

    Livas, Jeff

    2014-01-01

    Space-based Gravitational-wave Observatories (SGOs) will enable the systematic study of the frequency band from 0.0001 - 1 Hz of gravitational waves, where a rich array of astrophysical sources is expected. ESA has selected The Gravitational Universe as the science theme for the L3 mission opportunity with a nominal launch date in 2034. This will be at a minimum 15 years after ground-based detectors and pulsar timing arrays announce their first detections and at least 18 years after the LISA Pathfinder Mission will have demonstrated key technologies in a dedicated space mission. It is therefore important to develop mission concepts that can take advantage of the momentum in the field and the investment in both technology development and a precision measurement community on a more near-term timescale than the L3 opportunity. This talk will discuss a mission concept based on the LISA baseline that resulted from a recent mission architecture study.

  15. Gravitational microlensing by double stars and planetary systems

    NASA Technical Reports Server (NTRS)

    Mao, Shunde; Paczynski, Bohdan

    1991-01-01

    Almost all stars are in binary systems. When the separation between the two components is comparable to the Einstein ring radius corresponding to the combined mass of the binary acting as a gravitational lens, then an extra pair of images can be created, and the light curve of a lensed source becomes complicated. It is estimated that about 10 percent of all lensing episodes of the Galactic bulge stars will strongly display the binary nature of the lens. The effect is strong even if the companion is a planet. A massive search for microlensing of the Galactic bulge stars may lead to a discovery of the first extrasolar planetary systems.

  16. Confocal microscopy and variable-focal length microlenses

    NASA Astrophysics Data System (ADS)

    Mac Raighne, Aaron M.; Yang, Lisong; Dunbar, L. Andrea; McCabe, Eithne M.; Scharf, Toralf

    2004-07-01

    Confocal microscopy has a unique optical sectioning property which allows three-dimensional images at different depths. Use of a microlens array is a potential alternative to the Nipkow disk for parallel imaging with high throughput in real-time confocal microscopy. The use of variable-focal-length microlenses can provide a way to axially scan the foci electronically avoiding the inflexible mechanical movement of the lens or the sample. Here we demonstrate a combination of a variable-focal-length microlens array and a fiber optic bundle as a way to create a high throughput aperture array that would be potentially applied as confocal imaging in vivo biological specimens. Variable focal length microlenses that we use consist of a liquid crystal film sandwiched between a pair of conductive substrates with patterned electrodes. The incident side of the microlens array was determined by examining the focus distribution in the axial direction. The variation of the focal length obtained by changing the voltage and corresponding focus intensity were measured through a conventional microscope. Meanwhile, the fiber bundle was characterized by coupling with either coherent or incoherent light source. We use the fiber bundle as both a multiple aperture and an image-carrying element and combine it with a microlens array to built up a confocal system. Axial responses are measured in two optical arrangements as a route to investigate endoscope potential.

  17. Caustic Structures and Detectability of Circumbinary Planets in Microlensing

    NASA Astrophysics Data System (ADS)

    Luhn, Jacob K.; Penny, Matthew T.; Gaudi, B. Scott

    2016-08-01

    Recent discoveries of circumbinary planets in Kepler data show that there is a viable channel of planet formation around binary main-sequence stars. Motivated by these discoveries, we have investigated the caustic structures and detectability of circumbinary planets in microlensing events. We have produced a suite of animations of caustics as a function of the projected separation and angle of the binary host to efficiently explore caustic structures over the entire circumbinary parameter space. Aided by these animations, we have derived a semi-empirical analytic expression for the location of planetary caustics, which are displaced in circumbinary lenses relative to those of planets with a single host. We have used this expression to show that the dominant source of caustic motion will be due to the planet’s orbital motion and not that of the binary star. Finally, we estimate the fraction of circumbinary microlensing events that are recognizable as such to be significant (5%–50%) for binary projected separations in the range 0.1–0.5 in units of Einstein radii.

  18. Empirical study of simulated two-planet microlensing events

    SciTech Connect

    Zhu, Wei; Gould, Andrew; Penny, Matthew; Mao, Shude; Gendron, Rieul

    2014-10-10

    We undertake the first study of two-planet microlensing models recovered from simulations of microlensing events generated by realistic multiplanet systems in which 292 planetary events, including 16 two-planet events, were detected from 6690 simulated light curves. We find that when two planets are recovered, their parameters are usually close to those of the two planets in the system most responsible for the perturbations. However, in 1 of the 16 examples, the apparent mass of both detected planets was more than doubled by the unmodeled influence of a third, massive planet. This fraction is larger than but statistically consistent with the roughly 1.5% rate of serious mass errors due to unmodeled planetary companions for the 274 cases from the same simulation in which a single planet is recovered. We conjecture that an analogous effect due to unmodeled stellar companions may occur more frequently. For 7 out of 23 cases in which two planets in the system would have been detected separately, only one planet was recovered because the perturbations due to the two planets had similar forms. This is a small fraction (7/274) of all recovered single-planet models, but almost a third of all events that might plausibly have led to two-planet models. Still, in these cases, the recovered planet tends to have parameters similar to one of the two real planets most responsible for the anomaly.

  19. Studying wave optics in the light curves of exoplanet microlensing

    NASA Astrophysics Data System (ADS)

    Mehrabi, Ahmad; Rahvar, Sohrab

    2013-05-01

    We study the wave optics features of gravitational microlensing by a binary lens composed of a planet and a parent star. In this system, the source star near the caustic line produces a pair of images in which they can play the role of secondary sources for the observer. This optical system is similar to the Young double-slit experiment. The coherent wavefronts from a source on the lens plane can form a diffraction pattern on the observer plane. This diffraction pattern has two modes from the close- and wide-pair images. From the observational point of view, we study the possibility of detecting this effect through the Square Kilometre Array (SKA) project in the resonance and high-magnification channels of binary lensing. While the red giant sources do not seem to satisfy the spatial coherency condition, during the caustic crossing a small part of a source traversing the caustic line can produce coherent pair images. Observations of wave optics effects at longer wavelengths accompanied by optical observations of a microlensing event provide extra information on the parameter space of the planet. These observations can provide a new basis for the study of exoplanets.

  20. Galactic Bulge Microlensing Events from the MACHO Collaboration

    SciTech Connect

    Thomas, C L; Griest, K; Popowski, P; Cook, K H; Drake, A J; Minniti, D; Myer, D G; Alcock, C; Allsman, R A; Alves, D R; Axelrod, T S; Becker, A C; Bennett, D P; Freeman, K C; Geha, M; Lehner, M J; Marshall, S L; Nelson, C A; Peterson, B A; Quinn, P J; Stubbs, C W; Sutherland, W; Vandehei, T; Welch, D L

    2005-06-16

    The authors present a catalog of 450 relatively high signal-to-noise microlensing events observed by the MACHO collaboration between 1993 and 1999. The events are distributed throughout the fields and, as expected, they show clear concentration toward the Galactic center. No optical depth is given for this sample since no blending efficiency calculation has been performed, and they find evidence for substantial blending. In a companion paper they give optical depths for the sub-sample of events on clump giant source stars, where blending is a less significant effect. Several events with sources that may belong to the Sagittarius dwarf galaxy are identified. For these events even relatively low dispersion spectra could suffice to classify these events as either consistent with Sagittarius membership or as non-Sagittarius sources. Several unusual events, such as microlensing of periodic variable source stars, binary lens events, and an event showing extended source effects are identified. They also identify a number of contaminating background events as cataclysmic variable stars.

  1. Microlensing planet detection via geosynchronous and low Earth orbit satellites

    NASA Astrophysics Data System (ADS)

    Mogavero, F.; Beaulieu, J. P.

    2016-01-01

    Planet detection through microlensing is usually limited by a well-known degeneracy in the Einstein timescale tE, which prevents mass and distance of the lens to be univocally determined. It has been shown that a satellite in geosynchronous orbit could provide masses and distances for most standard planetary events (tE ≈ 20 days) via a microlens parallax measurement. This paper extends the analysis to shorter Einstein timescales, tE ≈ 1 day, when dealing with the case of Jupiter-mass lenses. We then study the capabilities of a low Earth orbit satellite on even shorter timescales, tE ≈ 0.1 days. A Fisher matrix analysis is employed to predict how the 1-σ error on parallax depends on tE and the peak magnification of the microlensing event. It is shown that a geosynchronous satellite could detect parallaxes for Jupiter-mass free floaters and discover planetary systems around very low-mass brown dwarfs. Moreover, a low Earth orbit satellite could lead to the discovery of Earth-mass free-floating planets. Limitations to these results can be the strong requirements on the photometry, the effects of blending, and in the case of the low orbit, the Earth's umbra.

  2. Gravitational microlensing as a probe for dark matter clumps

    NASA Astrophysics Data System (ADS)

    Fedorova, E.; Sliusar, V. M.; Zhdanov, V. I.; Alexandrov, A. N.; Del Popolo, A.; Surdej, J.

    2016-04-01

    Extended dark matter (DM) substructures may play the role of microlenses in the Milky Way and in extragalactic gravitational lens systems (GLSs). We compare microlensing effects caused by point masses (Schwarzschild lenses) and extended clumps of matter using a simple model for the lens mapping. A superposition of the point mass and the extended clump is also considered. For special choices of the parameters, this model may represent a cusped clump of cold DM, a cored clump of self-interacting dark matter (SIDM) or an ultra-compact minihalo of DM surrounding a massive point-like object. We built the resulting micro-amplification curves for various parameters of one clump moving with respect to the source in order to estimate differences between the light curves caused by clumps and by point lenses. The results show that it may be difficult to distinguish between these models. However, some region of the clump parameters can be restricted by considering the high amplification events at the present level of photometric accuracy. Then we estimate the statistical properties of the amplification curves in extragalactic GLSs. For this purpose, an ensemble of amplification curves is generated yielding the autocorrelation functions (ACFs) of the curves for different choices of the system parameters. We find that there can be a significant difference between these ACFs if the clump size is comparable with typical Einstein radii; as a rule, the contribution of clumps makes the ACFs less steep.

  3. Space-based Search for Transiting Exoplanets Orbiting Bright Stars

    NASA Astrophysics Data System (ADS)

    Tsvetanov, Zlatan

    At the current stage of research transiting planets hold the key to advancing our knowledge of exoplanets as they are the only targets that allow determination of many of the key plane-tary parameters. Because the employed techniques are differential (either photometry or spec-troscopy) and the planet is significantly fainter the host star the dominant limitation is simply the number of photons. This puts a very high premium on transiting planets with bright parent stars. The ExoPlanet Task Force recognized the high value of planets transiting bright stars and identified the need to perform a wide area space-based transit survey. In this presentation I will describe a program that addresses the ExoPTF recommendation by using the output of one of the instruments on the currently operating space mission STEREO. STEREO is the third mission in NASA's Solar Terrestrial Probes program. It uses two nearly identical spacecrafts -one on an Earth-leading orbit and one on an Earth-trailing orbit -each equipped with a suit of five small telescopes to provide a stereoscopic view of the coronal mass ejections (CME) as they propagate away from the Sun. As each of these telescopes observes a portion of the heliospehre, they also image the star field in the background. For the purposes of this study we will consider only the images obtained by the HI-1 instruments. Other instruments, although showing the stellar background as well, do not have the data output suitable for a search for transiting exoplanets. This project described here has the potential of delivering a number of very high value targets for follow-up studies with a wide range of facilities, both ground-based and space-based. It will provide a complete survey of all bright stars (<10m) for 18% of the sky. The photometric data series have the sensitivity to detect all transiting hot-Jupiters and other gas giants with periods up to ˜20 days and even some Neptune size planets orbiting bright and/or late type stars. On

  4. Space-based lasers - Ultimate ABM system

    NASA Astrophysics Data System (ADS)

    Henderson, W. D.

    1982-05-01

    Technical details and the possibilities of near term development of a series of space-based high energy lasers (HEL) capable of providing an effective missile and hostile aircraft defense system are discussed. The crucial parameter is the deposition of sufficient kill energy on any chosen target, and is estimated to be a few tens of kilojoules/sq cm, with a wavelength of 1 micron, at a range of 3000 km, and with a dwell time of 1/2 sec. The chemical laser is asserted to be receiving most R and D activity, while the free electron laser is also a candidate for the mission. Targeting thousands of ballistic missiles in the boost phase before deployment of MIRVs is noted to be a formidable problem, while the existence of the HEL satellites will result in threats of attack from ASATs, nuclear ASATs, space mines, or other HEL satellites. A more in-depth study is indicated before decisions are made to embark on a full scale HEL program.

  5. Space-based ballistic-missile defense

    SciTech Connect

    Bethe, H.A.; Garwin, R.L.; Gottfried, K.; Kendall, H.W.

    1984-10-01

    This article, based on a forthcoming book by the Union for Concerned Scientists, focuses on the technical aspects of the issue of space-based ballistic-missile defense. After analysis, the authors conclude that the questionable performance of the proposed defense, the ease with which it could be overwhelmed or circumvented, and its potential as an antisatellite system would cause grievous damage to the security of the US if the Strategic Defense Initiative were to be pursued. The path toward greater security lies in quite another direction, they feel. Although research on ballistic-missile defense should continue at the traditional level of expenditure and within the constraints of the ABM Treaty, every effort should be made to negotiate a bilateral ban on the testing and use of space weapons. The authors think it is essential that such an agreement cover all altitudes, because a ban on high-altitude antisatellite weapons alone would not viable if directed energy weapons were developed for ballistic-missile defense. Further, the Star Wars program, unlikely ever to protect the entire nation against a nuclear attack, would nonetheless trigger a major expansion of the arms race.

  6. Crosstalk reduction in free space optical interconnects systems using microlenses with Gaussian transmittance

    NASA Astrophysics Data System (ADS)

    Al-Ababneh, Nedal

    2014-05-01

    A novel method to reduce the diffraction crosstalk for micro-lens based free space optical interconnects is presented. Instead of using microlenses with uniform transmittance apertures, the use of microlenses with non-uniform transmittance apertures is proposed. It is shown that the diffraction crosstalk which exists in the free space interconnects systems that use microlenses with uniform transmittance apertures can be substantially reduced by using microlenses with Gaussian transmittance. The optical field at the detectors array using both the uniform and Gaussian apertures have been derived and used to calculate the crosstalk. Numerical results have been introduced to show the improvement of the signal-to-crosstalk ratio when using the Gaussian transmittance for the microlens.

  7. A Space Based Solar Power Satellite System

    NASA Astrophysics Data System (ADS)

    Engel, J. M.; Polling, D.; Ustamujic, F.; Yaldiz, R.; et al.

    2002-01-01

    . Based on the expected revenues from about 300 customers, SPoTS needs a significant contribution from public funding to be commercial viable. However, even though the system might seem to be a huge investment first, it provides a unique steppingstone for future space based wireless transfer of energy to the Earth. Also the public funding is considered as an interest free loan and is due to be paid back over de lifetime period of SPoTS. These features make the SPoTS very attractive in comparison to other space projects of the same science field.

  8. Flat Panel Space Based Space Surveillance Sensor

    NASA Astrophysics Data System (ADS)

    Kendrick, R.; Duncan, A.; Wilm, J.; Thurman, S. T.; Stubbs, D. M.; Ogden, C.

    2013-09-01

    limited telescope is, therefore, replaced by in-process integration and test as part of the PIC fabrication that substantially reduces associated schedule and cost. The low profile and low SWaP of a SPIDER system enables high resolution imaging with a payload that is similar in size and aspect ratio to a solar panel. This allows high resolution low cost options for space based space surveillance telescopes. The low SWaP design enables hosted payloads, cubesat designs as well as traditional bus options that are lower cost. We present a description of the concept and preliminary simulation and experimental data that demonstrate the imaging capabilities of the SPIDER technique.

  9. Magnetic space-based field measurements

    NASA Technical Reports Server (NTRS)

    Langel, R. A.

    1981-01-01

    Satellite measurements of the geomagnetic field began with the launch of Sputnik 3 in May 1958 and have continued sporadically in the intervening years. A list of spacecraft that have made significant contributions to an understanding of the near-earth geomagnetic field is presented. A new era in near-earth magnetic field measurements began with NASA's launch of Magsat in October 1979. Attention is given to geomagnetic field modeling, crustal magnetic anomaly studies, and investigations of the inner earth. It is concluded that satellite-based magnetic field measurements make global surveys practical for both field modeling and for the mapping of large-scale crustal anomalies. They are the only practical method of accurately modeling the global secular variation. Magsat is providing a significant contribution, both because of the timeliness of the survey and because its vector measurement capability represents an advance in the technology of such measurements.

  10. Real time and in situ monitoring of microlenses fabricated with deep proton writing

    NASA Astrophysics Data System (ADS)

    Gomez, Virginia; Ottevaere, Heidi; Thienpont, Hugo

    2008-04-01

    Micro-optical components are of growing interest and used in very different applications such as displays, biophotonics, optical-data communication... More in particular, refractive microlenses and refractive microlens arrays are widely used. The fabrication of these components has been extensively investigated and today different technologies are already commercially available such as thermal reflow, laser ablation, reactive ion etching, microject printing... These technologies allow the fabrication of high-quality microlenses in different materials, however these fabrication methods are often too expensive and too time-consuming for prototyping. In our facilities, we implemented Deep Proton Writing (DPW) as a rapid prototyping technology to fabricate plastic refractive microlenses and microlens arrays. To reduce the calibration time and minimize the influence of uncontrollable external parameters we built a transmission Mach-Zehnder interferometer allowing to monitor in situ and in real-time the growing of the refractive microlenses. This means that we can stop the growing process of the microlenses as soon as the predefined specifications are reached. Additionally we can determine out of this interferometric data the geometrical properties and optical quality of each of the microlenses. We have studied the precision and accuracy of our interferometer for the characterization of the latter components. In this paper, we will present the latest results showing the performance of our set-up and the resulting enhancements of our technology.

  11. Caustic-induced features in microlensing magnification probability distributions

    NASA Technical Reports Server (NTRS)

    Rauch, Kevin P.; Mao, Shude; Wambsganss, Joachim; Paczynski, Bohdan

    1992-01-01

    Numerical simulations have uncovered a previously unrecognized 'bump' in the macroimage magnification probabilities produced by a planar distribution of point masses. The result could be relevant to cases of microlensing by star fields in single galaxies, for which this lensing geometry is an excellent approximation. The bump is produced by bright pairs of microimages formed by sources lying near the caustics of the lens. The numerically calculated probabilities for the magnifications in the range between 3 and 30 are significantly higher than those given by the asymptotic relation derived by Schneider. The bump present in the two-dimensional lenses appears not to exist in the magnification probability distribution produced by a fully three-dimensional lens.

  12. Oil droplets of bird eyes: microlenses acting as spectral filters

    PubMed Central

    Stavenga, Doekele G.; Wilts, Bodo D.

    2014-01-01

    An important component of the cone photoreceptors of bird eyes is the oil droplets located in front of the visual-pigment-containing outer segments. The droplets vary in colour and are transparent, clear, pale or rather intensely yellow or red owing to various concentrations of carotenoid pigments. Quantitative modelling of the filter characteristics using known carotenoid pigment spectra indicates that the pigments’ absorption spectra are modified by the high concentrations that are present in the yellow and red droplets. The high carotenoid concentrations not only cause strong spectral filtering but also a distinctly increased refractive index at longer wavelengths. The oil droplets therefore act as powerful spherical microlenses, effectively channelling the spectrally filtered light into the photoreceptor's outer segment, possibly thereby compensating for the light loss caused by the spectral filtering. The spectral filtering causes narrow-band photoreceptor spectral sensitivities, which are well suited for spectral discrimination, especially in birds that have feathers coloured by carotenoid pigments. PMID:24395968

  13. Gravitational Microlensing by Ellis Wormhole: Second Order Effects

    NASA Astrophysics Data System (ADS)

    Lukmanova, Regina; Kulbakova, Aliya; Izmailov, Ramil; Potapov, Alexander A.

    2016-07-01

    Gravitational lensing is the effect of light bending in a gravitational field. It can be used as a possible observational method to detect or exclude the existence of wormholes. In this work, we extend the work by Abe on gravitational microlensing by Ellis wormhole by including the second order deflection term. Using the lens equation and definition of Einstein radius, we find the angular locations of the physical image inside and outside Einstein ring. The work contains a comparative analysis of light curves between the Schwarzschild black hole and the Ellis wormhole that can be used to distinguish such objects though such distinctions are too minute to be observable even in the near future. We also tabulate the optical depth and event rate for lensing by bulge and Large Magellanic Cloud (LMC) stars.

  14. THE IMPORTANCE OF BINARY GRAVITATIONAL MICROLENSING EVENTS THROUGH HIGH-MAGNIFICATION CHANNEL

    SciTech Connect

    Han, Cheongho; Hwang, Kyu-Ha E-mail: kyuha@astroph.chungbuk.ac.k

    2009-12-20

    We estimate the detection efficiency of binary gravitational lensing events through the channel of high-magnification events. From this estimation, we find that binaries in the separation ranges of 0.1 approx< s approx< 10, 0.2 approx< s approx< 5, and 0.3 approx< s approx< 3 can be detected with approx100% efficiency for events with magnifications higher than A = 100, 50, and 10, respectively, where s represents the projected separation between the lens components normalized by the Einstein radius. We also find that the range of high efficiency covers nearly the whole mass-ratio range of stellar companions. Due to the high efficiency in wide ranges of parameter space, we point out that the majority of binary-lens events will be detected through the high-magnification channel in lensing surveys that focus on high-magnification events for efficient detections of microlensing planets. In addition to the high efficiency, the simplicity of the efficiency estimation makes the sample of these binaries useful in the statistical studies of the distributions of binary companions as functions of mass ratio and separation. We also discuss other implications of these events.

  15. Observational limits on Omega in stars, brown dwarfs, and stellar remnants from gravitational microlensing

    NASA Technical Reports Server (NTRS)

    Dalcanton, Julianne J.; Canizares, Claude R.; Granados, Arno; Steidel, Charles C.; Stocke, John T.

    1994-01-01

    Microlensing by compact objects with masses between approximately 0.001 solar masses and approximately 300 solar masses will amplify the continuum emission of a quasar, without significantly changing its line emission. Thus, compact objects with masses associated with stars, subdwarfs, and stellar remnants will reduce the apparent equivalent widths of quasar emission lines. It is possible to detect this population of lenses by searching for an increase in the number of small equivalent width quasars with redshift. This increase was looked for, but not found, in quasar samples taken from the Einstein Medium Sensitivity Survey and the Steidel & Sargent absorption-line studies. Thus, Omega(sub c), the cosmological density of compact objects relative to the critical density, is less than or approximately equal to 0.1 in the mass range 0.01 solar masses-20 solar masses (for Omega less than 0.6). For any value of Omega, Omega(sub c) less than or approximately equal to 0.2 in the larger mass range 0.001 solar masses-60 solar masses, and Omega(sub c) less than 1 for 0.001 solar masses-300 solar masses. Subdwarfs, stellar objects, or their remnants (e.g., MACHOS) cannot close the universe.

  16. The Importance of Binary Gravitational Microlensing Events Through High-Magnification Channel

    NASA Astrophysics Data System (ADS)

    Han, Cheongho; Hwang, Kyu-Ha

    2009-12-01

    We estimate the detection efficiency of binary gravitational lensing events through the channel of high-magnification events. From this estimation, we find that binaries in the separation ranges of 0.1 lsim s lsim 10, 0.2 lsim s lsim 5, and 0.3 lsim s lsim 3 can be detected with ~100% efficiency for events with magnifications higher than A = 100, 50, and 10, respectively, where s represents the projected separation between the lens components normalized by the Einstein radius. We also find that the range of high efficiency covers nearly the whole mass-ratio range of stellar companions. Due to the high efficiency in wide ranges of parameter space, we point out that the majority of binary-lens events will be detected through the high-magnification channel in lensing surveys that focus on high-magnification events for efficient detections of microlensing planets. In addition to the high efficiency, the simplicity of the efficiency estimation makes the sample of these binaries useful in the statistical studies of the distributions of binary companions as functions of mass ratio and separation. We also discuss other implications of these events.

  17. M dwarfs, microlensing, and the mass budget of the Galaxy

    NASA Technical Reports Server (NTRS)

    Bahcall, John N.; Flynn, Chris; Gould, Andrew; Kirhakos, Sofia

    1994-01-01

    We show that faint red stars do not contribute significantly to the mass budget of the Galaxy or to microlensing statistics. Our results are obtained by analyzing two long exposures of a high-latitude field taken with the Wide Field Camera (WFC) on the newly repaired Hubble Space Telescope (HST). Stars are easily distinguished from galaxies essentially to the limiting magnitudes of the images. We find five stars with 2.0 less than V - I less than 3.0 and I less than 25.3 and no stars with V - I greater than 3.0. Therefore, main-sequence stars with M(sub I) greater than 10 that are above the hydrogen-burning limit in the dark halo or the spheroid contribute less than 6% of the unseen matter. Faint red disk stars, M-dwarfs, contribute at most 15% to the mass of the disk. We parameterize the faint end of the cumulative distribution of stars, Phi, as a function of luminosity L(sub V), d Phi/d ln L(sub V) proportional to L(sub V exp -gamma). For spheroid stars, gamma less than 0.32 over the range 6 less than M(sub V) less than 17, with 98% confidence. The disk luminosity function falls, gamma less than 0, for 15 approximately less than M(sub V) approximately less than 19. Faint red stars in the disk or thick disk, and stars with M(sub V) less than 16 in the spheroid contribute tau less than 10(exp -8) to the optical depth to microlensing toward the Large Magellanic Cloud.

  18. Magnetic space-based field measurements

    NASA Technical Reports Server (NTRS)

    Langel, R. A.

    1981-01-01

    Because the near Earth magnetic field is a complex combination of fields from outside the Earth of fields from its core and of fields from its crust, measurements from space prove to be the only practical way to obtain timely, global surveys. Due to difficulty in making accurate vector measurements, early satellites such as Sputnik and Vanguard measured only the magnitude survey. The attitude accuracy was 20 arc sec. Both the Earth's core fields and the fields arising from its crust were mapped from satellite data. The standard model of the core consists of a scalar potential represented by a spherical harmonics series. Models of the crustal field are relatively new. Mathematical representation is achieved in localized areas by arrays of dipoles appropriately located in the Earth's crust. Measurements of the Earth's field are used in navigation, to map charged particles in the magnetosphere, to study fluid properties in the Earth's core, to infer conductivity of the upper mantels, and to delineate regional scale geological features.

  19. First Space-based Microlens Parallax Measurement of an Isolated Star: Spitzer Observations of OGLE-2014-BLG-0939

    NASA Astrophysics Data System (ADS)

    Yee, J. C.; Udalski, A.; Calchi Novati, S.; Gould, A.; Carey, S.; Poleski, R.; Gaudi, B. S.; Pogge, R. W.; Skowron, J.; Kozłowski, S.; Mróz, P.; Pietrukowicz, P.; Pietrzyński, G.; Szymański, M. K.; Soszyński, I.; Ulaczyk, K.; Wyrzykowski, Ł.

    2015-04-01

    We present the first space-based microlens parallax measurement of an isolated star. From the striking differences in the lightcurve as seen from Earth and from Spitzer (˜ 1 AU to the west), we infer a projected velocity {{\\tilde{v}}hel}˜ 250 km {{s}-1}, which strongly favors a lens in the Galactic Disk with mass M=0.23+/- 0.07 {{M}⊙ } and distance {{D}L}=3.1+/- 0.4 kpc. An ensemble of such measurements drawn from our ongoing program could be used to measure the single-lens mass function including dark objects, and also is necessary for measuring the Galactic distribution of planets since the ensemble reflects the underlying Galactic distribution of microlenses. We study the application of the many ideas to break the four-fold degeneracy first predicted by Refsdal 50 years ago. We find that this degeneracy is clearly broken, but by two unanticipated mechanisms: a weak constraint on the orbital parallax from the ground-based data and a definitive measurement of the source proper motion.

  20. TIME DELAY AND ACCRETION DISK SIZE MEASUREMENTS IN THE LENSED QUASAR SBS 0909+532 FROM MULTIWAVELENGTH MICROLENSING ANALYSIS

    SciTech Connect

    Hainline, Laura J.; Morgan, Christopher W.; MacLeod, Chelsea L.; Landaal, Zachary D.; Kochanek, C. S.; Harris, Hugh C.; Tilleman, Trudy; Goicoechea, L. J.; Shalyapin, V. N.

    2013-09-01

    We present three complete seasons and two half-seasons of Sloan Digital Sky Survey (SDSS) r-band photometry of the gravitationally lensed quasar SBS 0909+532 from the U.S. Naval Observatory, as well as two seasons each of SDSS g-band and r-band monitoring from the Liverpool Robotic Telescope. Using Monte Carlo simulations to simultaneously measure the system's time delay and model the r-band microlensing variability, we confirm and significantly refine the precision of the system's time delay to {Delta}t{sub AB} = 50{sub -4}{sup +2} days, where the stated uncertainties represent the bounds of the formal 1{sigma} confidence interval. There may be a conflict between the time delay measurement and a lens consisting of a single galaxy. While models based on the Hubble Space Telescope astrometry and a relatively compact stellar distribution can reproduce the observed delay, the models have somewhat less dark matter than we would typically expect. We also carry out a joint analysis of the microlensing variability in the r and g bands to constrain the size of the quasar's continuum source at these wavelengths, obtaining log {l_brace}(r{sub s,r}/cm)[cos i/0.5]{sup 1/2}{r_brace} = 15.3 {+-} 0.3 and log {l_brace}(r{sub s,g}/cm)[cos i/0.5]{sup 1/2}{r_brace} = 14.8 {+-} 0.9, respectively. Our current results do not formally constrain the temperature profile of the accretion disk but are consistent with the expectations of standard thin disk theory.

  1. MICROLENSING-BASED ESTIMATE OF THE MASS FRACTION IN COMPACT OBJECTS IN LENS GALAXIES

    SciTech Connect

    Mediavilla, E.; Guerras, E.; Canovas, H.; Oscoz, A.; Falco, E.; Motta, V.; Jean, C.; Mosquera, A. M.

    2009-12-01

    We estimate the fraction of mass that is composed of compact objects in gravitational lens galaxies. This study is based on microlensing measurements (obtained from the literature) of a sample of 29 quasar image pairs seen through 20 lens galaxies. We determine the baseline for no microlensing magnification between two images from the ratios of emission line fluxes. Relative to this baseline, the ratio between the continua of the two images gives the difference in microlensing magnification. The histogram of observed microlensing events peaks close to no magnification and is concentrated below 0.6 mag, although two events of high magnification, DELTAm approx 1.5, are also present. We study the likelihood of the microlensing measurements using frequency distributions obtained from simulated microlensing magnification maps for different values of the fraction of mass in compact objects, alpha. The concentration of microlensing measurements close to DELTAm approx 0 can be explained only by simulations corresponding to very low values of alpha (10% or less). A maximum likelihood test yields alpha = 0.05{sup +0.09}{sub -0.03} (90% confidence interval) for a quasar continuum source of intrinsic size r{sub s{sub 0}}approx2.6x10{sup 15} cm. This estimate is valid in the 0.1-10 M {sub sun} range of microlens masses. We study the dependence of the estimate of alpha with r{sub s{sub 0}}, and find that alpha approx< 0.1 for r{sub s{sub 0}}approx<1.3x10{sup 16} cm. High values of alpha are possible only for source sizes much larger than commonly expected (r{sub s{sub 0}}>>2.6x10{sup 16} cm). Regarding the current controversy about Milky Way/LMC and M31 microlensing studies, our work supports the hypothesis of a very low content in MACHOS (Massive Compact Halo Objects). In fact, according to our study, quasar microlensing probably arises from the normal star populations of lens galaxies and there is no statistical evidence for MACHOS in the dark halos.

  2. BINARY MICROLENSING EVENT OGLE-2009-BLG-020 GIVES VERIFIABLE MASS, DISTANCE, AND ORBIT PREDICTIONS

    SciTech Connect

    Skowron, J.; Gould, A.; Nelson, C. R.; Kozlowski, S.; Udalski, A.; Poleski, R.; Ulaczyk, K.; Kubiak, M.; Szymanski, M. K.; Dong, Subo; Monard, L. A. G.; Han, C.; McCormick, J.; Moorhouse, D.; Thornley, G.; Maury, A.; Bramich, D. M.; Greenhill, J.; Bond, I.; Wyrzykowski, L.

    2011-09-01

    We present the first example of binary microlensing for which the parameter measurements can be verified (or contradicted) by future Doppler observations. This test is made possible by a confluence of two relatively unusual circumstances. First, the binary lens is bright enough (I = 15.6) to permit Doppler measurements. Second, we measure not only the usual seven binary-lens parameters, but also the 'microlens parallax' (which yields the binary mass) and two components of the instantaneous orbital velocity. Thus, we measure, effectively, six 'Kepler+1' parameters (two instantaneous positions, two instantaneous velocities, the binary total mass, and the mass ratio). Since Doppler observations of the brighter binary component determine five Kepler parameters (period, velocity amplitude, eccentricity, phase, and position of periapsis), while the same spectroscopy yields the mass of the primary, the combined Doppler + microlensing observations would be overconstrained by 6 + (5 + 1) - (7 + 1) = 4 degrees of freedom. This makes possible an extremely strong test of the microlensing solution. We also introduce a uniform microlensing notation for single and binary lenses, define conventions, summarize all known microlensing degeneracies, and extend a set of parameters to describe full Keplerian motion of the binary lenses.

  3. Gravitational microlensing of a reverberating quasar broad-line region - I. Method and qualitative results

    NASA Astrophysics Data System (ADS)

    Garsden, H.; Bate, N. F.; Lewis, G. F.

    2011-12-01

    The kinematics and morphology of the broad emission-line region (BELR) of quasars are the subject of significant debate. The two leading methods for constraining BELR properties are microlensing and reverberation mapping. Here we combine these two methods with a study of the microlensing behaviour of the BELR in Q2237+0305, as a change in continuum emission (a 'flare') passes through it. Beginning with some generic models of the BELR - sphere, bicones, disc - we slice in velocity and time to produce brightness profiles of the BELR over the duration of the flare. These are numerically microlensed to determine whether microlensing of reverberation mapping provides new information about the properties of BELRs. We describe our method and show images of the models as they are flaring, and the unlensed and lensed spectra that are produced. Qualitative results and a discussion of the spectra are given in this paper, highlighting some effects that could be observed. Our conclusion is that the influence of microlensing, while not strong, can produce significant observable effects that will help in differentiating the properties of BELRs. Research undertaken as part of the Commonwealth Cosmology Initiative (CCI: ), an international collaboration supported by the Australian Research Council.

  4. COSMIC ERROR CAUSED BY THE GRAVITATIONAL MICROLENSING EFFECT IN HIGH-PRECISION ASTROMETRY

    SciTech Connect

    Yano, Taihei

    2012-10-01

    We have investigated an expected deviation of the positions or the proper motions of stars as the cosmic error caused by the gravitational microlensing effect. In observing stars in the Galactic bulge region, we obtain an expected deviation of a star positions by the gravitational microlensing effect of about 7 {mu}as. We have also estimated the expected deviation of the proper motions of stars in the Galactic bulge caused by the gravitational microlensing effect. The expected deviation of the proper motions is mainly caused by the lens object located at the nearest angular distance from the source star. Each deviation of the proper motion has a value of less than 0.02 {mu}as yr{sup -1} for 99% of the sources. We have investigated the correlation of the deviation of Galactic bulge stars caused by the gravitational microlensing effect. The value of the correlation angle of the positional deviation is estimated to be about 1 arcmin. In the same way, we have estimated the correlation angle of the deviation of the proper motions. The angle is estimated to be about 1 arcsec. The following difference distinguishes the deviation of the position and that of the proper motion. The positional deviation is affected not only by lenses near the source but also by the lenses far from the source. On the other hand, the deviation of the proper motion by microlensing is mainly only caused by the nearest lens from the source. This difference causes that of the correlation angle.

  5. DISCOVERY OF ENERGY-DEPENDENT X-RAY MICROLENSING IN Q2237+0305

    SciTech Connect

    Chen Bin; Dai Xinyu; Kochanek, C. S.; Blackburne, Jeffrey A.; Chartas, George; Kozlowski, Szymon

    2011-10-20

    We present our long-term Chandra X-ray monitoring data for the gravitationally lensed quasar Q2237+0305 with 20 epochs spanning 10 years. We easily detect microlensing variability between the images in the full (0.2-8 keV), soft (0.2-2 keV), and hard (2-8 keV) bands at very high confidence. We also detect, for the first time, chromatic microlensing differences between the soft and hard X-ray bands. The hard X-ray band is more strongly microlensed than the soft band, suggesting that the corona above the accretion disk thought to generate the X-rays has a non-uniform electron distribution, in which the hotter and more energetic electrons occupy more compact regions surrounding the black holes. Both the hard and soft X-ray bands are more strongly microlensed than the optical (rest-frame UV) emission, indicating that the X-ray emission is more compact than the optical, confirming the microlensing results from other lenses.

  6. Acoustic Shaping: Enabling Technology for a Space-Based Economy

    NASA Astrophysics Data System (ADS)

    Komerath, N. M.; Matos, C. A.; Coker, A.; Wanis, S.; Hausaman, J.; Ames, R. G.; Tan, X. Y.

    1999-01-01

    This abstract presents three points for discussion: (1) Key to the development of civilization in space, is a space-based marketplace, where the need to compete in earth-based markets is removed, along with the constraint of launch costs from Earth. (2) A body of technical results, obtained by the authors' team, indicates promise for non-contact manufacturing in space, of low-cost items required for human presence in space. This is presented along with various other techniques which hold promise. (3) The economics of starting a space-based production company are heavily dependent on the presence of a rudimentary infrastructure. A national-level investment in space-based infrastructure, would be an essential catalyst for the development of a space-based economy. Some suggestions for the beginnings of this infrastructure are repeated from the literature.

  7. An expert systems application to space base data processing

    NASA Technical Reports Server (NTRS)

    Babb, Stephen M.

    1988-01-01

    The advent of space vehicles with their increased data requirements are reflected in the complexity of future telemetry systems. Space based operations with its immense operating costs will shift the burden of data processing and routine analysis from the space station to the Orbital Transfer Vehicle (OTV). A research and development project is described which addresses the real time onboard data processing tasks associated with a space based vehicle, specifically focusing on an implementation of an expert system.

  8. MICROLENSING BINARIES DISCOVERED THROUGH HIGH-MAGNIFICATION CHANNEL

    SciTech Connect

    Shin, I.-G.; Choi, J.-Y.; Park, S.-Y.; Han, C.; Gould, A.; Gaudi, B. S.; Sumi, T.; Udalski, A.; Beaulieu, J.-P.; Dominik, M.; Allen, W.; Bos, M.; Christie, G. W.; Depoy, D. L.; Dong, S.; Drummond, J.; Gal-Yam, A.; Hung, L.-W.; Janczak, J.; Kaspi, S.; Collaboration: muFUN Collaboration; MOA Collaboration; OGLE Collaboration; PLANET Collaboration; RoboNet Collaboration; MiNDSTEp Consortium; and others

    2012-02-20

    Microlensing can provide a useful tool to probe binary distributions down to low-mass limits of binary companions. In this paper, we analyze the light curves of eight binary-lensing events detected through the channel of high-magnification events during the seasons from 2007 to 2010. The perturbations, which are confined near the peak of the light curves, can be easily distinguished from the central perturbations caused by planets. However, the degeneracy between close and wide binary solutions cannot be resolved with a 3{sigma} confidence level for three events, implying that the degeneracy would be an important obstacle in studying binary distributions. The dependence of the degeneracy on the lensing parameters is consistent with a theoretical prediction that the degeneracy becomes severe as the binary separation and the mass ratio deviate from the values of resonant caustics. The measured mass ratio of the event OGLE-2008-BLG-510/MOA-2008-BLG-369 is q {approx} 0.1, making the companion of the lens a strong brown dwarf candidate.

  9. Adaptable acylindrical microlenses fabricated by femtosecond laser micromachining

    NASA Astrophysics Data System (ADS)

    Paiè, Petra; Bragheri, Francesca; Claude, Theo; Osellame, Roberto

    2015-03-01

    Microfluidic lenses are a powerful tool for many lab on a chip applications ranging from sensing to detection and also to imaging purpose, with the great advantage to increase the degree of integration and compactness of these micro devices. In this work we present the realization of such a compact microfluidic lens with reconfigurable optical properties. The technique used to realize the device we present is femtosecond laser micromachining followed by chemical etching, which allows to easily fabricate 3D microfluidic devices with an arbitrary shape. Thanks to that it has been possible to easily fabricate different lens made up by cylindrical microchannel in fused silica glasses filled with liquids with a proper refractive index. The optical properties of these devices are tested and shown to be in a good agreement with the theoretical model previously implemented. Furthermore we have also optimized the design of these microlenses in order to reduce the effects of spherical aberrations in the focal region, thus allowing us to obtain a set of different acylindrical microfluidic lenses, whose validation is also reported. In this work the lens adaptability can be achieved by replacing the liquid inside the microchannel, so that we can easily tune the feature of the focused beam. Thus increasing the possible range of applications of these micro optical elements, as an example we report on the validation of the device as a fast integrated optofluidic shutter.

  10. Prospects for Observing Ultracompact Binaries with Space-Based Gravitational Wave Interferometers and Optical Telescopes

    NASA Technical Reports Server (NTRS)

    Littenberg, T. B.; Larson, S. L.; Nelemans, G.; Cornish, N. J.

    2012-01-01

    Space-based gravitational wave interferometers are sensitive to the galactic population of ultracompact binaries. An important subset of the ultracompact binary population are those stars that can be individually resolved by both gravitational wave interferometers and electromagnetic telescopes. The aim of this paper is to quantify the multimessenger potential of space-based interferometers with arm-lengths between 1 and 5 Gm. The Fisher information matrix is used to estimate the number of binaries from a model of the Milky Way which are localized on the sky by the gravitational wave detector to within 1 and 10 deg(exp 2) and bright enough to be detected by a magnitude-limited survey.We find, depending on the choice ofGW detector characteristics, limiting magnitude and observing strategy, that up to several hundred gravitational wave sources could be detected in electromagnetic follow-up observations.

  11. Probing the gravitational Faraday rotation using quasar X-ray microlensing.

    PubMed

    Chen, Bin

    2015-01-01

    The effect of gravitational Faraday rotation was predicted in the 1950s, but there is currently no practical method for measuring this effect. Measuring this effect is important because it will provide new evidence for correctness of general relativity, in particular, in the strong field limit. We predict that the observed degree and angle of the X-ray polarization of a cosmologically distant quasar microlensed by the random star field in a foreground galaxy or cluster lens vary rapidly and concurrently with flux during caustic-crossing events using the first simulation of quasar X-ray microlensing polarization light curves. Therefore, it is possible to detect gravitational Faraday rotation by monitoring the X-ray polarization of gravitationally microlensed quasars. Detecting this effect will also confirm the strong gravity nature of quasar X-ray emission. PMID:26574051

  12. Microlensing of Kepler stars as a method of detecting primordial black hole dark matter.

    PubMed

    Griest, Kim; Lehner, Matthew J; Cieplak, Agnieszka M; Jain, Bhuvnesh

    2011-12-01

    If the dark matter consists of primordial black holes (PBHs), we show that gravitational lensing of stars being monitored by NASA's Kepler search for extrasolar planets can cause significant numbers of detectable microlensing events. A search through the roughly 150,000 light curves would result in large numbers of detectable events for PBHs in the mass range 5×10(-10) M(⊙) to 10(-4) M(⊙). Nondetection of these events would close almost 2 orders of magnitude of the mass window for PBH dark matter. The microlensing rate is higher than previously noticed due to a combination of the exceptional photometric precision of the Kepler mission and the increase in cross section due to the large angular sizes of the relatively nearby Kepler field stars. We also present a new formalism for calculating optical depth and microlensing rates in the presence of large finite-source effects. PMID:22182077

  13. New Limits on Primordial Black Hole Dark Matter from an Analysis of Kepler Source Microlensing Data

    NASA Astrophysics Data System (ADS)

    Griest, Kim; Cieplak, Agnieszka M.; Lehner, Matthew J.

    2013-11-01

    We present new limits on the allowed masses of a dark matter (DM) halo consisting of primordial black holes (PBH) (or any other massive compact halo object). We analyze two years of data from the Kepler satellite, searching for short-duration bumps caused by gravitational microlensing. After removing background events consisting of variable stars, flare events, and comets or asteroids moving through the Kepler field, we find no microlensing candidates. We measure the efficiency of our selection criteria by adding millions of simulated microlensing lensing events into the Kepler light curves. We find that PBH DM with masses in the range 2×10-9M⊙ to 10-7M⊙ cannot make up the entirety of the DM in the Milky Way. At the low-mass end, this decreases the allowed mass range by more than an order of magnititude.

  14. Microlensing of Kepler Stars as a Method of Detecting Primordial Black Hole Dark Matter

    NASA Astrophysics Data System (ADS)

    Griest, Kim; Lehner, Matthew J.; Cieplak, Agnieszka M.; Jain, Bhuvnesh

    2011-12-01

    If the dark matter consists of primordial black holes (PBHs), we show that gravitational lensing of stars being monitored by NASA’s Kepler search for extrasolar planets can cause significant numbers of detectable microlensing events. A search through the roughly 150 000 light curves would result in large numbers of detectable events for PBHs in the mass range 5×10-10M⊙ to 10-4M⊙. Nondetection of these events would close almost 2 orders of magnitude of the mass window for PBH dark matter. The microlensing rate is higher than previously noticed due to a combination of the exceptional photometric precision of the Kepler mission and the increase in cross section due to the large angular sizes of the relatively nearby Kepler field stars. We also present a new formalism for calculating optical depth and microlensing rates in the presence of large finite-source effects.

  15. Probing the gravitational Faraday rotation using quasar X-ray microlensing

    PubMed Central

    Chen, Bin

    2015-01-01

    The effect of gravitational Faraday rotation was predicted in the 1950s, but there is currently no practical method for measuring this effect. Measuring this effect is important because it will provide new evidence for correctness of general relativity, in particular, in the strong field limit. We predict that the observed degree and angle of the X-ray polarization of a cosmologically distant quasar microlensed by the random star field in a foreground galaxy or cluster lens vary rapidly and concurrently with flux during caustic-crossing events using the first simulation of quasar X-ray microlensing polarization light curves. Therefore, it is possible to detect gravitational Faraday rotation by monitoring the X-ray polarization of gravitationally microlensed quasars. Detecting this effect will also confirm the strong gravity nature of quasar X-ray emission. PMID:26574051

  16. New limits on primordial black hole dark matter from an analysis of Kepler source microlensing data.

    PubMed

    Griest, Kim; Cieplak, Agnieszka M; Lehner, Matthew J

    2013-11-01

    We present new limits on the allowed masses of a dark matter (DM) halo consisting of primordial black holes (PBH) (or any other massive compact halo object). We analyze two years of data from the Kepler satellite, searching for short-duration bumps caused by gravitational microlensing. After removing background events consisting of variable stars, flare events, and comets or asteroids moving through the Kepler field, we find no microlensing candidates. We measure the efficiency of our selection criteria by adding millions of simulated microlensing lensing events into the Kepler light curves. We find that PBH DM with masses in the range 2 × 10(-9) M[Symbol: see text] to 10(-7)M[Symbol: see text] cannot make up the entirety of the DM in the Milky Way. At the low-mass end, this decreases the allowed mass range by more than an order of magnititude. PMID:24237504

  17. Future Photovoltaic Power Generation for Space-Based Power Utilities

    NASA Astrophysics Data System (ADS)

    Bailey, S.; Landis, G.; Raffaelle, R.; Hepp, A.

    2002-01-01

    A recent NASA program, Space Solar Power Exploratory Research and Technology (SERT), investigated the technologies needed to provide cost-competitive ground baseload electrical power from space based solar energy conversion. This goal mandated low cost, light weight gigawatt (GW) power generation. Investment in solar power generation technologies would also benefit high power military, commercial and science missions. These missions are generally those involving solar electric propulsion, surface power systems to sustain an outpost or a permanent colony on the surface of the moon or mars, space based lasers or radar, or as large earth orbiting power stations which can serve as central utilities for other orbiting spacecraft, or as in the SERT program, potentially beaming power to the earth itself. This paper will discuss requirements for the two latter options, the current state of the art of space solar cells, and a variety of both evolving thin film cells as well as new technologies which may impact the future choice of space solar cells for a high power mission application. The space world has primarily transitioned to commercially available III-V (GaInP/GaAs/Ge) cells with 24-26% air mass zero (AMO) efficiencies. Research in the III-V multi-junction solar cells has focused on fabricating either lattice-mismatched materials with optimum stacking bandgaps or new lattice matched materials with optimum bandgaps. In the near term this will yield a 30% commercially available space cell and in the far term possibly a 40% cell. Cost reduction would be achieved if these cells could be grown on a silicon rather than a germanium substrate since the substrate is ~65% of the cell cost or, better yet, on a polyimide or possibly a ceramic substrate. An overview of multi-junction cell characteristics will be presented here. Thin film cells require substantially less material and have promised the advantage of large area, low cost manufacturing. However, space cell requirements

  18. Determining the Mass of Proxima Centauri through Astrometric Microlensing

    NASA Astrophysics Data System (ADS)

    Sahu, Kailash

    2012-10-01

    We propose to determine the mass of our nearest neighbor, Proxima Centauri, using the novel technique of astrometric microlensing. Proxima is a dM6e star, with an estimated mass of about 0.12 Msun, lying at a distance of 1.3 pc and having a large proper motion of 3.8 arcsec/yr. In a reprise of the famous 1919 solar eclipse that verified general relativity, Proxima will pass in front of a pair of 18th-magnitude background stars in 2015, affording us two independent opportunities to measure the relativistic deflection. The first passage will occur in May 2015 {impact parameter 1.5 arcsec}, and the second in June 2015 {impact parameter 1.4 arcsec}. As Proxima passes in front, it will cause a relativistic deflection of the background stars' images by 0.5 milliarcsec, an amount readily detectable with HST/WFC3.The gravitational deflection angle depends only upon the distances and relative positions of the stars, and the mass of the lens {Proxima}. Since the distance to Proxima is well known from accurate parallax measurements, and the relative stellar positions can be determined precisely before the event, the astrometric measurement offers a unique and direct method to measure the mass of a single, isolated star. We anticipate better than 10% accuracy for the mass determination. The mass of Proxima is of special interest because it is the nearest M dwarf, representing the most common type of star in the Galaxy, for which the mass-luminosity relation is still uncertain at present.

  19. Determining the Mass of Proxima Centauri through Astrometric Microlensing

    NASA Astrophysics Data System (ADS)

    Sahu, Kailash

    2013-10-01

    We propose to determine the mass of our nearest neighbor, Proxima Centauri, using the novel technique of astrometric microlensing. Proxima is a dM6e star, with an estimated mass of about 0.12 Msun, lying at a distance of 1.3 pc and having a large proper motion of 3.8 arcsec/yr. In a reprise of the famous 1919 solar eclipse that verified general relativity, Proxima will pass in front of a pair of 18th-magnitude background stars in 2015, affording us two independent opportunities to measure the relativistic deflection. The first passage will occur in May 2015 {impact parameter 1.5 arcsec}, and the second in June 2015 {impact parameter 1.4 arcsec}. As Proxima passes in front, it will cause a relativistic deflection of the background stars' images by 0.5 milliarcsec, an amount readily detectable with HST/WFC3.The gravitational deflection angle depends only upon the distances and relative positions of the stars, and the mass of the lens {Proxima}. Since the distance to Proxima is well known from accurate parallax measurements, and the relative stellar positions can be determined precisely before the event, the astrometric measurement offers a unique and direct method to measure the mass of a single, isolated star. We anticipate better than 10% accuracy for the mass determination. The mass of Proxima is of special interest because it is the nearest M dwarf, representing the most common type of star in the Galaxy, for which the mass-luminosity relation is still uncertain at present.

  20. Determining the Mass of Proxima Centauri through Astrometric Microlensing

    NASA Astrophysics Data System (ADS)

    Sahu, Kailash

    2014-10-01

    We propose to determine the mass of our nearest neighbor, Proxima Centauri, using the novel technique of astrometric microlensing. Proxima is a dM6e star, with an estimated mass of about 0.12 Msun, lying at a distance of 1.3 pc and having a large proper motion of 3.8 arcsec/yr. In a reprise of the famous 1919 solar eclipse that verified general relativity, Proxima will pass in front of a pair of 18th-magnitude background stars in 2015, affording us two independent opportunities to measure the relativistic deflection. The first passage will occur in May 2015 (impact parameter 1.5 arcsec), and the second in June 2015 (impact parameter 1.4 arcsec). As Proxima passes in front, it will cause a relativistic deflection of the background stars' images by ~0.5 milliarcsec, an amount readily detectable with HST/WFC3.The gravitational deflection angle depends only upon the distances and relative positions of the stars, and the mass of the lens (Proxima). Since the distance to Proxima is well known from accurate parallax measurements, and the relative stellar positions can be determined precisely before the event, the astrometric measurement offers a unique and direct method to measure the mass of a single, isolated star. We anticipate better than 10% accuracy for the mass determination. The mass of Proxima is of special interest because it is the nearest M dwarf, representing the most common type of star in the Galaxy, for which the mass-luminosity relation is still uncertain at present.

  1. Galactic Distribution of Planets From High-Magnification Microlensing Events

    NASA Astrophysics Data System (ADS)

    Gould, Andrew; Yee, Jennifer; Carey, Sean

    2015-10-01

    We will use Spitzer to measure microlens parallaxes for ~14 microlensing events that are high-magnification (as seen from Earth), in order to determine the Galactic distribution of planets. Simultaneous observations from Spitzer and Earth yield parallaxes because they are separated by ~1 AU, which is of order the size of the Einstein radius projected on the observer plane. Hence, Earth and Spitzer see substantially different lightcurves for the same event. These Spitzer parallaxes enable measurements of the distances to the lenses (and their masses), which is a crucial element for measuring the Galactic distribution of planets. High-mag events are exceptionally sensitive to planets: Gould+ (2010) detected 6 planets from 13 high-mag events. However, previously it was believed impossible to measure their parallaxes using Spitzer: scheduling constraints imply a 3-10 day delay from event recognition to first observation, while high-mag events are typically recognized only 1-2 days before peak. By combining aggressive observing protocols, a completely new photometry pipeline, and new mathematical techniques, we successfully measured parallaxes for 7 events with peak magnification A>100 and another ~7 with 50

  2. Control of Space-Based Electron Beam Free Form Fabrication

    NASA Technical Reports Server (NTRS)

    Seifzer. W. J.; Taminger, K. M.

    2007-01-01

    Engineering a closed-loop control system for an electron beam welder for space-based additive manufacturing is challenging. For earth and space based applications, components must work in a vacuum and optical components become occluded with metal vapor deposition. For extraterrestrial applications added components increase launch weight, increase complexity, and increase space flight certification efforts. Here we present a software tool that closely couples path planning and E-beam parameter controls into the build process to increase flexibility. In an environment where data collection hinders real-time control, another approach is considered that will still yield a high quality build.

  3. Space-based augmentation for global navigation satellite systems.

    PubMed

    Grewal, Mohinder S

    2012-03-01

    This paper describes space-based augmentation for global navigation satellite systems (GNSS). Space-based augmentations increase the accuracy and integrity of the GNSS, thereby enhancing users' safety. The corrections for ephemeris, ionospheric delay, and clocks are calculated from reference station measurements of GNSS data in wide-area master stations and broadcast via geostationary earth orbit (GEO) satellites. This paper discusses the clock models, satellite orbit determination, ionospheric delay estimation, multipath mitigation, and GEO uplink subsystem (GUS) as used in the Wide Area Augmentation System developed by the FAA. PMID:22481784

  4. Intelligibility and Space-based Voice with Relaxed Delay Constraints

    NASA Technical Reports Server (NTRS)

    Nguyen, Sam; Okino, Clayton; Cheng, Michael

    2008-01-01

    The inherent aspects and flaws surrounding space based communication is technically described and the math surrounding encoding and decoding LT Codes is examined. Utilizing LT codes as a means of reducing packet erasures due to corrupted packets on an RF link can result in higher voice quality. PESQ-MOS measure was used to analyze voice degradation over space links tested for LT codec size and number of 10ms per packet.Extensions utilizing LT codes to improve the packet erasure performance and combining the use of ASR could provide for a solid means of identifying the benefit in terms of intelligibility of voice communications in space-based networks

  5. Technology for a NASA Space-Based Science Operations Grid

    NASA Technical Reports Server (NTRS)

    Bradford, Robert N.; Redman, Sandra H.

    2003-01-01

    This viewgraph representation presents an overview of a proposal to develop a space-based operations grid in support of space-based science experiments. The development of such a grid would provide a dynamic, secure and scalable architecture based on standards and next-generation reusable software and would enable greater science collaboration and productivity through the use of shared resources and distributed computing. The authors propose developing this concept for use on payload experiments carried aboard the International Space Station. Topics covered include: grid definitions, portals, grid development and coordination, grid technology and potential uses of such a grid.

  6. Space-based aperture array for ultra-long wavelength radio astronomy

    NASA Astrophysics Data System (ADS)

    Rajan, Raj Thilak; Boonstra, Albert-Jan; Bentum, Mark; Klein-Wolt, Marc; Belien, Frederik; Arts, Michel; Saks, Noah; van der Veen, Alle-Jan

    2016-02-01

    The past decade has seen the advent of various radio astronomy arrays, particularly for low-frequency observations below 100 MHz. These developments have been primarily driven by interesting and fundamental scientific questions, such as studying the dark ages and epoch of re-ionization, by detecting the highly red-shifted 21 cm line emission. However, Earth-based radio astronomy observations at frequencies below 30 MHz are severely restricted due to man-made interference, ionospheric distortion and almost complete non-transparency of the ionosphere below 10 MHz. Therefore, this narrow spectral band remains possibly the last unexplored frequency range in radio astronomy. A straightforward solution to study the universe at these frequencies is to deploy a space-based antenna array far away from Earths' ionosphere. In the past, such space-based radio astronomy studies were principally limited by technology and computing resources, however current processing and communication trends indicate otherwise. Furthermore, successful space-based missions which mapped the sky in this frequency regime, such as the lunar orbiter RAE-2, were restricted by very poor spatial resolution. Recently concluded studies, such as DARIS (Disturbuted Aperture Array for Radio Astronomy In Space) have shown the ready feasibility of a 9 satellite constellation using off the shelf components. The aim of this article is to discuss the current trends and technologies towards the feasibility of a space-based aperture array for astronomical observations in the Ultra-Long Wavelength (ULW) regime of greater than 10 m i.e., below 30 MHz. We briefly present the achievable science cases, and discuss the system design for selected scenarios such as extra-galactic surveys. An extensive discussion is presented on various sub-systems of the potential satellite array, such as radio astronomical antenna design, the on-board signal processing, communication architectures and joint space-time estimation of the

  7. National Coordination Office for Space-Based PNT

    NASA Astrophysics Data System (ADS)

    Shaw, M. E.

    2008-12-01

    In December 2004, President Bush issued the US Policy on space-based positioning, navigation, and timing (PNT), providing guidance on the management of the Global Positioning System (GPS) and other space- based PNT systems. The policy established the National Executive Committee (EXCOM) to advise and coordinate federal agencies on matters related to space-based PNT. Chaired jointly by the deputy secretaries of defense and transportation, the EXCOM includes equivalent level officials from the Departments of State, the Interior, Agriculture, Commerce, and Homeland Security, the Joint Chiefs of Staff, and the National Aeronautics and Space Administration (NASA). A National Coordination Office (NCO) supports the EXCOM through an interagency staff. Since establishing the EXCOM and NCO in 2005, the organizations have quickly grown in influence and effectiveness, leading or managing many interagency initiatives including the development of a Five-Year National Space-Based PNT Plan, the Space-Based PNT Interference Detection and Mitigation (IDM) Plan, and other strategic documents. The NCO has also facilitated interagency coordination on numerous policy issues and on external communications intended to spread a consistent, positive US message about space-based PNT. Role of the NCO - The purpose of the EXCOM is to provide top-level guidance to US agencies regarding space-based PNT infrastructure. The president established it at the deputy secretary level to ensure its strategic recommendations effect real change in agency budgets. Recognizing such high-level officials could only meet every few months, the president directed the EXCOM to establish an NCO to carry out its day-to-day business, including overseeing the implementation of EXCOM action items across the member agencies. These range from the resolution of funding issues to the assessment of strategic policy options. They also include the completion of specific tasks and documents requested by the EXCOM co

  8. MICROLENSING OF QUASAR BROAD EMISSION LINES: CONSTRAINTS ON BROAD LINE REGION SIZE

    SciTech Connect

    Guerras, E.; Mediavilla, E.; Kochanek, C. S.; Munoz, J. A.; Falco, E.; Motta, V.

    2013-02-20

    We measure the differential microlensing of the broad emission lines between 18 quasar image pairs in 16 gravitational lenses. We find that the broad emission lines are in general weakly microlensed. The results show, at a modest level of confidence (1.8{sigma}), that high ionization lines such as C IV are more strongly microlensed than low ionization lines such as H{beta}, indicating that the high ionization line emission regions are more compact. If we statistically model the distribution of microlensing magnifications, we obtain estimates for the broad line region size of r{sub s} = 24{sup +22} {sub -15} and r{sub s} = 55{sup +150} {sub -35} lt-day (90% confidence) for the high and low ionization lines, respectively. When the samples are divided into higher and lower luminosity quasars, we find that the line emission regions of more luminous quasars are larger, with a slope consistent with the expected scaling from photoionization models. Our estimates also agree well with the results from local reveberation mapping studies.

  9. Digital holographic characterization of liquid microlenses array fabricated in electrode-less configuration

    NASA Astrophysics Data System (ADS)

    Miccio, L.; Vespini, V.; Grilli, S.; Paturzo, M.; Finizio, A.; De Nicola, S.; Ferraro, P.

    2009-06-01

    We show how thin liquid film on polar dielectric substrate can form an array of liquid micro-lenses. The effect is driven by the pyroelectric effect leading to a new concept in electro-wetting (EW). EW is a viable method for actuation of liquids in microfluidic systems and requires the design and fabrication of complex electrodes for suitable actuation of liquids. When compared to conventional electrowetting devices, the pyroelectric effect allowed to have an electrode-less and circuitless configuration. In our case the surface electric charge induced by the thermal stimulus is able to pattern selectively the surface wettability according to geometry of the ferroelectric domains micro-engineered into the lithium niobate crystal. We show that different geometries of liquid microlenses can be obtained showing also a tuneability of the focal lenses down to 1.6 mm. Thousand of liquid microlenses, each with 100 μm diameter, can be formed and actuated. Also different geometries such as hemi-cylindrical and toroidal liquid structures can be easily obtained. By means of a digital holography method, an accurate characterization of the micro-lenses curvature is performed and presented. The preliminary results concerning the imaging capability of the micro-lens array are also reported. Microlens array can find application in medical stereo-endoscopy, imaging, telecommunication and optical data storage too.

  10. Dark Matter in the Galactic Bulge: A Microlensing Point of View

    NASA Astrophysics Data System (ADS)

    Alard, C.

    The recent results obtained by the different microlensing projects towards the Bulge of the Milky Way raise the problem of dark matter in the inner part of our Galaxy. The observations may suggest an important contribution of low mass objects to the lensing rates. However, these observations are affected by important biases in the brown dwarf regime. More reliable estimates of the lensing rates can be obtained from analyses restricted to the Bulge giant sources. Unfortunately, most of the microlensing events detected by the different collaborations are associated with sources much fainter than the Bulge giant, it makes the interpretation of the results difficult. However, the rapid progress of the Microlensing technique promise that reliable estimates of the mass function at the low mass end will be obtained in the incoming years. Estimates of the amount of dark matter by various techniques, depend on the model of Galactic structure that is adopted. In particular, the microlensing projects brings new evidence for a massive bar in the inner part of our Galaxy. We will review the most recent data on this topic, and will examine the remaining uncertainties on the bar models. Finally, I will show how the unperfect knowledge of the Galactic structure affects the determination of the mass function towards the center of the Galaxy. To conclude we will compare the Milky way to Galaxies of similar types. In particular we will examine the distribution of dark matter in the central area of barred spiral galaxies.

  11. Optically recorded tunable microlenses based on dye-doped liquid crystal cells

    NASA Astrophysics Data System (ADS)

    Lucchetti, Liana; Tasseva, Jordanka

    2012-04-01

    We report on optically recorded microlenses in conventional liquid crystal cells doped with the azo-dye methyl-red. The focal length can be tuned electrically and changed in a wide range with just a small variation of the applied dc voltage. No patterned electrodes, built-in polymeric lens, or patterned molecular reorientation are required.

  12. Quasi-toric planar microlenses for oblique-incidence light beams

    NASA Astrophysics Data System (ADS)

    Kurita, Hisakazu; Kawai, Shigeru

    1997-02-01

    Novel quasi-toric planar microlenses (PML s) suitable for planar optics are proposed. The PML s have elliptical apertures, and they are astigmatism free for oblique-incidence light beams. A simple PML model is proposed for designing the quasi-toric PML. Fabricated quasi-toric PML s were evaluated to demonstrate their chip-to-chip interconnection probability.

  13. Relativity effects for space-based coherent lidar experiments

    NASA Technical Reports Server (NTRS)

    Gudimetla, V. S. Rao

    1996-01-01

    An effort was initiated last year in the Astrionics Laboratory at Marshall Space Flight Center to examine and incorporate, if necessary, the effects of relativity in the design of space-based lidar systems. A space-based lidar system, named AEOLUS, is under development at Marshall Space Flight Center and it will be used to accurately measure atmospheric wind profiles. Effects of relativity were also observed in the performance of space-based systems, for example in case of global positioning systems, and corrections were incorporated into the design of instruments. During the last summer, the effects of special relativity on the design of space-based lidar systems were studied in detail, by analyzing the problem of laser scattering off a fixed target when the source and a co-located receiver are moving on a spacecraft. Since the proposed lidar system uses a coherent detection system, errors even in the order of a few microradians must be corrected to achieve a good signal-to-noise ratio. Previous analysis assumed that the ground is flat and the spacecraft is moving parallel to the ground, and developed analytical expressions for the location, direction and Doppler shift of the returning radiation. Because of the assumptions used in that analysis, only special relativity effects were involved. In this report, that analysis is extended to include general relativity and calculate its effects on the design.

  14. Contamination in the MACHO data set and the puzzle of Large Magellanic Cloud microlensing

    NASA Astrophysics Data System (ADS)

    Griest, Kim; Thomas, Christian L.

    2005-05-01

    In a recent series of three papers, Belokurov, Evans & Le Du and Evans & Belokurov reanalysed the MACHO collaboration data and gave alternative sets of microlensing events and an alternative optical depth to microlensing towards the Large Magellanic Cloud (LMC). Although these authors examined less than 0.2 per cent of the data, they reported that by using a neural net program they had reliably selected a better (and smaller) set of microlensing candidates. Estimating the optical depth from this smaller set, they claimed that the MACHO collaboration overestimated the optical depth by a significant factor and that the MACHO microlensing experiment is consistent with lensing by known stars in the Milky Way and LMC. As we show below, the analysis by these authors contains several errors, and as a result their conclusions are incorrect. Their efficiency analysis is in error, and since they did not search through the entire MACHO data set, they do not know how many microlensing events their neural net would find in the data nor what optical depth their method would give. Examination of their selected events suggests that their method misses low signal-to-noise ratio events and thus would have lower efficiency than the MACHO selection criteria. In addition, their method is likely to give many more false positives (non-lensing events identified as lensing). Both effects would increase their estimated optical depth. Finally, we note that the EROS discovery that LMC event 23 is a variable star reduces the MACHO collaboration estimates of optical depth and the Macho halo fraction by around 8 per cent, and does open the question of additional contamination.

  15. Arrays of microlenses with variable focal lengths fabricated by restructuring polymer surfaces with an ink-jet device

    NASA Astrophysics Data System (ADS)

    Pericet-Camara, Ramon; Best, Andreas; Nett, Sebastian K.; Gutmann, Jochen S.; Bonaccurso, Elmar

    2007-07-01

    We report of a method for fabricating two-dimensional, regular arrays of polymer microlenses with focal lengths variable between 0.2 and 4.5 mm. We first make concave microlenses by ink-jetting solvent on a polymer substrate with a commercial drop-on-demand device. Solvent evaporation restructures the surface by a series of combined effects, which are discussed. In the second step we obtain convex elastomeric microlenses by casting the template made in the first step. We demonstrate the good optical quality of the microlenses by characterising their surfaces with atomic force microscopy and white light interferometry, and by directly measuring their focal lengths with ad-hoc confocal laser scanning microscopy.

  16. Arrays of microlenses with variable focal lengths fabricated by restructuring polymer surfaces with an ink-jet device.

    PubMed

    Pericet-Camara, Ramon; Best, Andreas; Nett, Sebastian K; Gutmann, Jochen S; Bonaccurso, Elmar

    2007-07-23

    We report of a method for fabricating two-dimensional, regular arrays of polymer microlenses with focal lengths variable between 0.2 and 4.5 mm. We first make concave microlenses by ink-jetting solvent on a polymer substrate with a commercial drop-on-demand device. Solvent evaporation restructures the surface by a series of combined effects, which are discussed. In the second step we obtain convex elastomeric microlenses by casting the template made in the first step. We demonstrate the good optical quality of the microlenses by characterising their surfaces with atomic force microscopy and white light interferometry, and by directly measuring their focal lengths with ad-hoc confocal laser scanning microscopy. PMID:19547338

  17. Highly indistinguishable photons from deterministic quantum-dot microlenses utilizing three-dimensional in situ electron-beam lithography

    NASA Astrophysics Data System (ADS)

    Gschrey, M.; Thoma, A.; Schnauber, P.; Seifried, M.; Schmidt, R.; Wohlfeil, B.; Krüger, L.; Schulze, J.-H.; Heindel, T.; Burger, S.; Schmidt, F.; Strittmatter, A.; Rodt, S.; Reitzenstein, S.

    2015-07-01

    The success of advanced quantum communication relies crucially on non-classical light sources emitting single indistinguishable photons at high flux rates and purity. We report on deterministically fabricated microlenses with single quantum dots inside which fulfil these requirements in a flexible and robust quantum device approach. In our concept we combine cathodoluminescence spectroscopy with advanced in situ three-dimensional electron-beam lithography at cryogenic temperatures to pattern monolithic microlenses precisely aligned to pre-selected single quantum dots above a distributed Bragg reflector. We demonstrate that the resulting deterministic quantum-dot microlenses enhance the photon-extraction efficiency to (23+/-3)%. Furthermore we prove that such microlenses assure close to pure emission of triggered single photons with a high degree of photon indistinguishability up to (80+/-7)% at saturation. As a unique feature, both single-photon purity and photon indistinguishability are preserved at high excitation power and pulsed excitation, even above saturation of the quantum emitter.

  18. Self-aligned process for forming microlenses at the tips of vertical silicon nanowires by atomic layer deposition

    SciTech Connect

    Dan, Yaping Chen, Kaixiang; Crozier, Kenneth B.

    2015-01-01

    The microlens is a key enabling technology in optoelectronics, permitting light to be efficiently coupled to and from devices such as image sensors and light-emitting diodes. Their ubiquitous nature motivates the development of new fabrication techniques, since existing methods face challenges as microlenses are scaled to smaller dimensions. Here, the authors demonstrate the formation of microlenses at the tips of vertically oriented silicon nanowires via a rapid atomic layer deposition process. The nature of the process is such that the microlenses are centered on the nanowires, and there is a self-limiting effect on the final sizes of the microlenses arising from the nanowire spacing. Finite difference time domain electromagnetic simulations are performed of microlens focusing properties, including showing their ability to enhance visible-wavelength absorption in silicon nanowires.

  19. Distant Retrograde Orbits for space-based Near Earth Objects detection

    NASA Astrophysics Data System (ADS)

    Stramacchia, Michele; Colombo, Camilla; Bernelli-Zazzera, Franco

    2016-09-01

    We analyse a concept for the detection of Potentially Hazardous Asteroids (PHAs) from a space-based network of telescopes on retrograde Distant Periodic Orbits. Planar periodic orbits are designed in the Sun-Earth circular restricted three-body problem, starting from initial conditions in the Hill's problem available from the literature. A family of retrograde orbits centred at the Earth is selected as baseline, based on their maximum distance from Earth, larger than the Earth-L2 distance. Indeed, spacecraft on such orbits can detect PHAs incoming from the Sun direction, which could not otherwise be monitored from current Earth-based systems. A trade-off on the orbit amplitude, asteroid diameter to be detected, and the constellation size is performed considering current visible sensor telescope technology. The Chelyabinsk meteor scenario is studied and the potential warning time that could be gained with a space-based survey system with respect to an Earth based-survey system is shown.

  20. Technology for subsystems of space-based plant growth facilities

    NASA Technical Reports Server (NTRS)

    Bula, R. J.; Morrow, R. C.; Tibbitts, T. W.; Corey, R. B.

    1990-01-01

    Technologies for different subsystems of space-based plant growth facilities are being developed at the Wisconsin Center for Space Automation and Robotics, a NASA Center for the Commercial Development of Space. The technologies include concepts for water and nutrient delivery, for nutrient composition control, and for irradiation. Effort is being concentrated on these subsystems because available technologies cannot be effectively utilized for space applications.

  1. A super-jupiter orbiting a late-type star: A refined analysis of microlensing event OGLE-2012-BLG-0406

    SciTech Connect

    Tsapras, Y.; Street, R. A.; Choi, J.-Y.; Han, C.; Bozza, V.; Gould, A.; Dominik, M.; Browne, P.; Horne, K.; Hundertmark, M.; Beaulieu, J.-P.; Udalski, A.; Jørgensen, U. G.; Sumi, T.; Bramich, D. M.; Kains, N.; Ipatov, S.; Alsubai, K. A.; Snodgrass, C.; Steele, I. A.; Collaboration: RoboNet Collaboration; MiNDSTEp Collaboration; OGLE Collaboration; PLANET Collaboration; μFUN Collaboration; MOA Collaboration; and others

    2014-02-10

    We present a detailed analysis of survey and follow-up observations of microlensing event OGLE-2012-BLG-0406 based on data obtained from 10 different observatories. Intensive coverage of the light curve, especially the perturbation part, allowed us to accurately measure the parallax effect and lens orbital motion. Combining our measurement of the lens parallax with the angular Einstein radius determined from finite-source effects, we estimate the physical parameters of the lens system. We find that the event was caused by a 2.73 ± 0.43 M {sub J} planet orbiting a 0.44 ± 0.07 M {sub ☉} early M-type star. The distance to the lens is 4.97 ± 0.29 kpc and the projected separation between the host star and its planet at the time of the event is 3.45 ± 0.26 AU. We find that the additional coverage provided by follow-up observations, especially during the planetary perturbation, leads to a more accurate determination of the physical parameters of the lens.

  2. A Super-Jupiter Orbiting a Late-type Star: A Refined Analysis of Microlensing Event OGLE-2012-BLG-0406

    NASA Astrophysics Data System (ADS)

    Tsapras, Y.; Choi, J.-Y.; Street, R. A.; Han, C.; Bozza, V.; Gould, A.; Dominik, M.; Beaulieu, J.-P.; Udalski, A.; Jørgensen, U. G.; Sumi, T.; Bramich, D. M.; Browne, P.; Horne, K.; Hundertmark, M.; Ipatov, S.; Kains, N.; Snodgrass, C.; Steele, I. A.; RoboNet Collaboration; Alsubai, K. A.; Andersen, J. M.; Calchi Novati, S.; Damerdji, Y.; Diehl, C.; Elyiv, A.; Giannini, E.; Hardis, S.; Harpsøe, K.; Hinse, T. C.; Juncher, D.; Kerins, E.; Korhonen, H.; Liebig, C.; Mancini, L.; Mathiasen, M.; Penny, M. T.; Rabus, M.; Rahvar, S.; Scarpetta, G.; Skottfelt, J.; Southworth, J.; Surdej, J.; Tregloan-Reed, J.; Vilela, C.; Wambsganss, J.; MiNDSTEp Collaboration; Skowron, J.; Poleski, R.; Kozłowski, S.; Wyrzykowski, Ł.; Szymański, M. K.; Kubiak, M.; Pietrukowicz, P.; Pietrzyński, G.; Soszyński, I.; Ulaczyk, K.; OGLE Collaboration; Albrow, M. D.; Bachelet, E.; Barry, R.; Batista, V.; Bhattacharya, A.; Brillant, S.; Caldwell, J. A. R.; Cassan, A.; Cole, A.; Corrales, E.; Coutures, Ch.; Dieters, S.; Dominis Prester, D.; Donatowicz, J.; Fouqué, P.; Greenhill, J.; Kane, S. R.; Kubas, D.; Marquette, J.-B.; Menzies, J.; Père, C.; Pollard, K. R.; Zub, M.; PLANET Collaboration; Christie, G.; DePoy, D. L.; Dong, S.; Drummond, J.; Gaudi, B. S.; Henderson, C. B.; Hwang, K. H.; Jung, Y. K.; Kavka, A.; Koo, J.-R.; Lee, C.-U.; Maoz, D.; Monard, L. A. G.; Natusch, T.; Ngan, H.; Park, H.; Pogge, R. W.; Porritt, I.; Shin, I.-G.; Shvartzvald, Y.; Tan, T. G.; Yee, J. C.; μFUN Collaboration; Abe, F.; Bennett, D. P.; Bond, I. A.; Botzler, C. S.; Freeman, M.; Fukui, A.; Fukunaga, D.; Itow, Y.; Koshimoto, N.; Ling, C. H.; Masuda, K.; Matsubara, Y.; Muraki, Y.; Namba, S.; Ohnishi, K.; Rattenbury, N. J.; Saito, To.; Sullivan, D. J.; Sweatman, W. L.; Suzuki, D.; Tristram, P. J.; Tsurumi, N.; Wada, K.; Yamai, N.; Yock, P. C. M.; Yonehara, A.; MOA Collaboration

    2014-02-01

    We present a detailed analysis of survey and follow-up observations of microlensing event OGLE-2012-BLG-0406 based on data obtained from 10 different observatories. Intensive coverage of the light curve, especially the perturbation part, allowed us to accurately measure the parallax effect and lens orbital motion. Combining our measurement of the lens parallax with the angular Einstein radius determined from finite-source effects, we estimate the physical parameters of the lens system. We find that the event was caused by a 2.73 ± 0.43 M J planet orbiting a 0.44 ± 0.07 M ⊙ early M-type star. The distance to the lens is 4.97 ± 0.29 kpc and the projected separation between the host star and its planet at the time of the event is 3.45 ± 0.26 AU. We find that the additional coverage provided by follow-up observations, especially during the planetary perturbation, leads to a more accurate determination of the physical parameters of the lens.

  3. Earth & Space-Based Power Generation Systems - A Comparison Study

    NASA Astrophysics Data System (ADS)

    Zerta, M.; Blandow, V.; Collins, P.; Guillet, J.; Nordmann, Thomas; Schmidt, Patrick; Weindorf, Werner; Zittel, Werner

    2004-12-01

    The objective of the study [1] is to comparatively assess the economic viability, energy investment, risk and reliability issues of broad-scale introduction of terrestrial and space based solar power systems for a European power supply in 2030 at various scenario power levels. The scenario design in terms of base load and non-base load cases is only suited to gain principle knowledge about both terrestrial and space-based solar power system architectures. The comparative cost, energy, risk and reliability discussions and evaluations are based on highly asymmetrical input data due to different magnitudes of practical experiences. However, under the study assumptions given, space- based solar power systems may potentially provide a firm power supply and could be economically competitive to terrestrial solar power systems if space transportation costs in the lower hundreds EUR/kg payload are achieved. The energy payback time could be in the range of other solar power technologies far below their operational lifetimes. Risks attributed with SPS are mainly in the field of health and public acceptance of microwave power transmission, the general R&D risk and geopolitical implications.

  4. Space-Based Range Safety and Future Space Range Applications

    NASA Technical Reports Server (NTRS)

    Whiteman, Donald E.; Valencia, Lisa M.; Simpson, James C.

    2005-01-01

    The National Aeronautics and Space Administration (NASA) Space-Based Telemetry and Range Safety (STARS) study is a multiphase project to demonstrate the performance, flexibility and cost savings that can be realized by using space-based assets for the Range Safety [global positioning system (GPS) metric tracking data, flight termination command and range safety data relay] and Range User (telemetry) functions during vehicle launches and landings. Phase 1 included flight testing S-band Range Safety and Range User hardware in 2003 onboard a high-dynamic aircraft platform at Dryden Flight Research Center (Edwards, California, USA) using the NASA Tracking and Data Relay Satellite System (TDRSS) as the communications link. The current effort, Phase 2, includes hardware and packaging upgrades to the S-band Range Safety system and development of a high data rate Ku-band Range User system. The enhanced Phase 2 Range Safety Unit (RSU) provided real-time video for three days during the historic Global Flyer (Scaled Composites, Mojave, California, USA) flight in March, 2005. Additional Phase 2 testing will include a sounding rocket test of the Range Safety system and aircraft flight testing of both systems. Future testing will include a flight test on a launch vehicle platform. This paper discusses both Range Safety and Range User developments and testing with emphasis on the Range Safety system. The operational concept of a future space-based range is also discussed.

  5. Space-Based Range Safety and Future Space Range Applications

    NASA Technical Reports Server (NTRS)

    Whiteman, Donald E.; Valencia, Lisa M.; Simpson, James C.

    2005-01-01

    The National Aeronautics and Space Administration Space-Based Telemetry and Range Safety study is a multiphase project to demonstrate the performance, flexibility and cost savings that can be realized by using space-based assets for the Range Safety (global positioning system metric tracking data, flight termination command and range safety data relay) and Range User (telemetry) functions during vehicle launches and landings. Phase 1 included flight testing S-band Range Safety and Range User hardware in 2003 onboard a high-dynamic aircraft platform at Dryden Flight Research Center (Edwards, California) using the NASA Tracking and Data Relay Satellite System as the communications link. The current effort, Phase 2, includes hardware and packaging upgrades to the S-band Range Safety system and development of a high data rate Ku-band Range User system. The enhanced Phase 2 Range Safety Unit provided real-time video for three days during the historic GlobalFlyer (Scaled Composites, Mojave, California) flight in March, 2005. Additional Phase 2 testing will include a sounding rocket test of the Range Safety system and aircraft flight testing of both systems. Future testing will include a flight test on a launch vehicle platform. This report discusses both Range Safety and Range User developments and testing with emphasis on the Range Safety system. The operational concept of a future space-based range is also discussed.

  6. Stellar, Remnant, Planetary, and Dark-Object Masses from Astrometric Microlensing

    NASA Technical Reports Server (NTRS)

    Gould, Andrew P.; Bennett, David P.; Boden, Andrew; Depoy, Darren L.; Gaudi, Scott B.; Griest, Kim; Han, Cheongho; Paczynski, Bohdan; Reid, I. Neill

    2004-01-01

    The primary goal of our project is to make a complete census of the stellar population of the Galaxy. We are broadening the term stellar here to include both ordinary stars and dark stars. Ordinary stars, burning their nuclear fuel and shining, can perhaps best be studied with traditional astronomical techniques, but dark stars, by which we include old brown dwarfs, black holes, old white dwarfs, neutron stars, and perhaps exotic objects such as mirror matter stars or primordial black holes, can only be studied by their gravitational effects. Traditionally, these objects have been probed in binaries, and thus selected in a way that may or may not be representative of their respective field populations. The only way to examine the field population of these stars is through microlensing, the deflection of light from a visible star in the background by an object (dark or not) in the foreground. When lensed, there are two images of the background star. Although these images cannot be resolved when the lens has a stellar mass, the lensing effect can be detected in two ways: photometrically, i.e. by measuring the magnification of the source by the lens, and astrometrically, i.e. by measuring the shift in the centroid of the two images. Photometric microlensing experiments have detected hundreds of microlensing events over the past decade. Despite its successes, photometric microlensing has so far been somewhat frustrating because these events are difficult to interpret. Almost nothing is known about the masses of individual lenses and very little is known about the statistical properties of the lenses treated as a whole, such as their average mass. Although probably over 100 of the lenses are in fact dark objects, we can't determine which they are, let alone investigate finer details such as what their masses are, and where they are in the Galaxy. With SIM, we will break the microlensing degeneracy, and allow detailed interpretation of individual microlensing events. We

  7. Besançon Galactic model analysis of MOA-II microlensing: evidence for a mass deficit in the inner bulge

    NASA Astrophysics Data System (ADS)

    Awiphan, S.; Kerins, E.; Robin, A. C.

    2016-02-01

    Galactic bulge microlensing surveys provide a probe of Galactic structure. We present the first field-by-field comparison between microlensing observations and the Besançon population synthesis Galactic model. Using an updated version of the model we provide maps of optical depth, average event duration and event rate for resolved source populations and for difference imaging analysis (DIA) events. We also compare the predicted event time-scale distribution to that observed. The simulation follows the selection criteria of the MOA-II survey. We modify the Besançon model to include M dwarfs and brown dwarfs. Our best-fitting model requires a brown dwarf mass function slope of -0.4. The model provides good agreement with the observed average duration, and respectable consistency with the shape of the time-scale distribution (reduced χ2 ≃ 2.2). The DIA and resolved source limiting yields bracket the observed number of events by MOA-II (2.17 × and 0.83 × the number observed, respectively). We perform a two-dimensional fit to the event spatial distribution to predict the optical depth and event rate across the Galactic bulge. The most serious difficulty for the model is that it provides only ˜50 per cent of the measured optical depth and event rate per star at low Galactic latitude around the inner bulge (|b| < 3°). This discrepancy most likely is associated with known underestimated extinction and star counts in the innermost regions and therefore provides additional support for a missing inner stellar population.

  8. MOA 2010-BLG-477Lb: CONSTRAINING THE MASS OF A MICROLENSING PLANET FROM MICROLENSING PARALLAX, ORBITAL MOTION, AND DETECTION OF BLENDED LIGHT

    SciTech Connect

    Bachelet, E.; Fouque, P.; Shin, I.-G.; Han, C.; Gould, A.; Dong, Subo; Marshall, J.; Skowron, J.; Menzies, J. W.; Beaulieu, J.-P.; Marquette, J.-B.; Bennett, D. P.; Bond, I. A.; Heyrovsky, D.; Street, R. A.; Sumi, T.; Udalski, A.; Abe, L.; Agabi, K.; Albrow, M. D.; Collaboration: PLANET Collaboration; FUN muCollaboration; MOA Collaboration; OGLE Collaboration; RoboNet Collaboration; MiNDSTEp Consortium; and others

    2012-07-20

    Microlensing detections of cool planets are important for the construction of an unbiased sample to estimate the frequency of planets beyond the snow line, which is where giant planets are thought to form according to the core accretion theory of planet formation. In this paper, we report the discovery of a giant planet detected from the analysis of the light curve of a high-magnification microlensing event MOA 2010-BLG-477. The measured planet-star mass ratio is q = (2.181 {+-} 0.004) Multiplication-Sign 10{sup -3} and the projected separation is s = 1.1228 {+-} 0.0006 in units of the Einstein radius. The angular Einstein radius is unusually large {theta}{sub E} = 1.38 {+-} 0.11 mas. Combining this measurement with constraints on the 'microlens parallax' and the lens flux, we can only limit the host mass to the range 0.13 < M/M{sub Sun} < 1.0. In this particular case, the strong degeneracy between microlensing parallax and planet orbital motion prevents us from measuring more accurate host and planet masses. However, we find that adding Bayesian priors from two effects (Galactic model and Keplerian orbit) each independently favors the upper end of this mass range, yielding star and planet masses of M{sub *} = 0.67{sup +0.33}{sub -0.13} M{sub Sun} and m{sub p} = 1.5{sup +0.8}{sub -0.3} M{sub JUP} at a distance of D = 2.3 {+-} 0.6 kpc, and with a semi-major axis of a = 2{sup +3}{sub -1} AU. Finally, we show that the lens mass can be determined from future high-resolution near-IR adaptive optics observations independently from two effects, photometric and astrometric.

  9. Precision compression molding of glass microlenses and microlens arrays--an experimental study.

    PubMed

    Firestone, G C; Yi, A Y

    2005-10-10

    An innovative manufacturing process utilizing high-temperature compression molding to fabricate aspherical microlenses by using optical glasses, such as BK7, K-PG325, and soda-lime glass, is investigated. In a departure from conventional approaches, a unique hollow contactless mold design is adopted. Polished glass substrates and the mold assembly are heated above the glass transition temperature first, followed by initial forming, then annealing. The forming rate is controlled in real time to ensure mold position accuracy. Mold materials used include tungsten carbides, 316 stainless steel, 715 copper nickel, and aluminum alloys. The geometric control of the microlenses or microlens arrays can be precisely controlled by the forming temperature, forming speed, mold design, and annealing time. PMID:16237925

  10. Fabrication of axicon microlenses on capillaries and microstructured fibers by wet etching.

    PubMed

    Bachus, Kyle; Filho, Elton Soares de Lima; Wlodarczyk, Kamila; Oleschuk, Richard; Messaddeq, Younes; Loock, Hans-Peter

    2016-09-01

    A facile method is presented for the fabrication of microlenses at the facet of fused silica capillaries and microstructured fibers. After submersion in hydrogen fluoride solution water is pumped slowly through the center hole of the capillary microchannel to create an etchant gradient extending from the capillary axis. The desired axicon angle is generated by adjusting the etching time and/or concentration of the etchant. Similarly, flow- assisted HF etching of a custom microstructured fiber containing nine microchannels produces nine individual microlenses simultaneously at the fiber facet, where each microaxicon lens shows a similar focusing pattern. A theoretical model of the flow-assisted etching process is used to determine the axicon angle and post angle. Also, a simple ray-based model was applied to characterize the focusing properties of the microaxicons in good agreement with experimental observations. PMID:27607641

  11. An efficient method to compute microlensed light curves for point sources

    NASA Technical Reports Server (NTRS)

    Witt, Hans J.

    1993-01-01

    We present a method to compute microlensed light curves for point sources. This method has the general advantage that all microimages contributing to the light curve are found. While a source moves along a straight line, all micro images are located either on the primary image track or on the secondary image tracks (loops). The primary image track extends from - infinity to + infinity and is made of many sequents which are continuously connected. All the secondary image tracks (loops) begin and end on the lensing point masses. The method can be applied to any microlensing situation with point masses in the deflector plane, even for the overcritical case and surface densities close to the critical. Furthermore, we present general rules to evaluate the light curve for a straight track arbitrary placed in the caustic network of a sample of many point masses.

  12. A ROBUST DETERMINATION OF THE SIZE OF QUASAR ACCRETION DISKS USING GRAVITATIONAL MICROLENSING

    SciTech Connect

    Jimenez-Vicente, J.; Mediavilla, E.; Kochanek, C. S.

    2012-06-01

    Using microlensing measurements for a sample of 27 image pairs of 19 lensed quasars we determine a maximum likelihood estimate for the accretion disk size of an average quasar of r{sub s} = 4.0{sup +2.4}{sub -3.1} lt-day at rest frame ({lambda}) = 1736 Angstrom-Sign for microlenses with a mean mass of (M) = 0.3 M{sub Sun }. This value, in good agreement with previous results from smaller samples, is roughly a factor of five greater than the predictions of the standard thin disk model. The individual size estimates for the 19 quasars in our sample are also in excellent agreement with the results of the joint maximum likelihood analysis.

  13. A NEW MICROLENSING EVENT IN THE DOUBLY IMAGED QUASAR Q 0957+561

    SciTech Connect

    Hainline, Laura J.; Morgan, Christopher W.; Beach, Joseph N.; Le, Truong X.; Kochanek, C. S.; Harris, Hugh C.; Tilleman, Trudy; Fadely, Ross; Falco, Emilio E. E-mail: cmorgan@usna.edu E-mail: m113678@usna.edu E-mail: hch@nofs.navy.mil E-mail: rfadely@haverford.edu

    2012-01-10

    We present evidence for ultraviolet/optical microlensing in the gravitationally lensed quasar Q 0957+561. We combine new measurements from our optical monitoring campaign at the United States Naval Observatory, Flagstaff, with measurements from the literature and find that the time-delay-corrected r-band flux ratio m{sub A} - m{sub B} has increased by {approx}0.1 mag over a period of five years beginning in the fall of 2005. We apply our Monte Carlo microlensing analysis procedure to the composite light curves, obtaining a measurement of the optical accretion disk size, log ((r{sub s} /cm)[cos (i)/0.5]{sup 1/2}) = 16.2 {+-} 0.5, that is consistent with the quasar accretion disk size-black hole mass relation.

  14. Microlensing probes the AGN structure of the lensed quasar J1131-1231

    NASA Astrophysics Data System (ADS)

    Sluse, D.; Claeskens, J.-F.; Hutsemékers, D.; Surdej, J.

    2008-04-01

    We present the analysis of single epoch long slit spectra of the three brightest images of the gravitationally lensed system J1131-1231. These spectra provide one of the clearest observational evidence for differential micro-lensing of broad emission lines (BELs) in a gravitationally lensed quasar. The micro-lensing effect enables us: (1) to confirm that the width of the emission lines is anti-correlated to the size of the emitting region; (2) to show that the bulk of Fe II is emitted in the outer parts of the Broad Line Region (BLR) while another fraction of Fe II is produced in a compact region; (3) to derive interesting informations on the origin of the narrow intrinsic Mg II absorption doublet observed in that system.

  15. Red Noise Versus Planetary Interpretations in the Microlensing Event Ogle-2013-BLG-446

    NASA Astrophysics Data System (ADS)

    Bachelet, E.; Bramich, D. M.; Han, C.; Greenhill, J.; Street, R. A.; Gould, A.; D'Ago, G.; AlSubai, K.; Dominik, M.; Figuera Jaimes, R.; Horne, K.; Hundertmark, M.; Kains, N.; Snodgrass, C.; Steele, I. A.; Tsapras, Y.; RoboNet Collaboration; Albrow, M. D.; Batista, V.; Beaulieu, J.-P.; Bennett, D. P.; Brillant, S.; Caldwell, J. A. R.; Cassan, A.; Cole, A.; Coutures, C.; Dieters, S.; Dominis Prester, D.; Donatowicz, J.; Fouqué, P.; Hill, K.; Marquette, J.-B.; Menzies, J.; Pere, C.; Ranc, C.; Wambsganss, J.; Warren, D.; PLANET Collaboration; de Almeida, L. Andrade; Choi, J.-Y.; DePoy, D. L.; Dong, S.; Hung, L.-W.; Hwang, K.-H.; Jablonski, F.; Jung, Y. K.; Kaspi, S.; Klein, N.; Lee, C.-U.; Maoz, D.; Muñoz, J. A.; Nataf, D.; Park, H.; Pogge, R. W.; Polishook, D.; Shin, I.-G.; Shporer, A.; Yee, J. C.; μFUN Collaboration; Abe, F.; Bhattacharya, A.; Bond, I. A.; Botzler, C. S.; Freeman, M.; Fukui, A.; Itow, Y.; Koshimoto, N.; Ling, C. H.; Masuda, K.; Matsubara, Y.; Muraki, Y.; Ohnishi, K.; Philpott, L. C.; Rattenbury, N.; Saito, To.; Sullivan, D. J.; Sumi, T.; Suzuki, D.; Tristram, P. J.; Yonehara, A.; The MOA Collaboration; Bozza, V.; Calchi Novati, S.; Ciceri, S.; Galianni, P.; Gu, S.-H.; Harpsøe, K.; Hinse, T. C.; Jørgensen, U. G.; Juncher, D.; Korhonen, H.; Mancini, L.; Melchiorre, C.; Popovas, A.; Postiglione, A.; Rabus, M.; Rahvar, S.; Schmidt, R. W.; Scarpetta, G.; Skottfelt, J.; Southworth, John; Stabile, An.; Surdej, J.; Wang, X.-B.; Wertz, O.; The MiNDSTEp Collaboration

    2015-10-01

    For all exoplanet candidates, the reliability of a claimed detection needs to be assessed through a careful study of systematic errors in the data to minimize the false positives rate. We present a method to investigate such systematics in microlensing data sets using the microlensing event OGLE-2013-BLG-0446 as a case study. The event was observed from multiple sites around the world and its high magnification (Amax ˜ 3000) allowed us to investigate the effects of terrestrial and annual parallax. Real-time modeling of the event while it was still ongoing suggested the presence of an extremely low-mass companion (˜3M⊕) to the lensing star, leading to substantial follow-up coverage of the light curve. We test and compare different models for the light curve and conclude that the data do not favor the planetary interpretation when systematic errors are taken into account.

  16. OGLE-2005-BLG-153: MICROLENSING DISCOVERY AND CHARACTERIZATION OF A VERY LOW MASS BINARY

    SciTech Connect

    Hwang, K.-H.; Han, C.; Ryu, Y.-H.; Udalski, A.; Kubiak, M.; Szymanski, M. K.; Pietrzynski, G.; Soszynski, I.; Szewczyk, O.; Ulaczyk, K.; Wyrzykowski, L.; Bond, I. A.; Beaulieu, J.-P.; Dominik, M.; Horne, K.; Gould, A.; Gaudi, B. S.; Abe, F.; Botzler, C. S.; Hearnshaw, J. B.

    2010-11-01

    The mass function and statistics of binaries provide important diagnostics of the star formation process. Despite this importance, the mass function at low masses remains poorly known due to observational difficulties caused by the faintness of the objects. Here we report the microlensing discovery and characterization of a binary lens composed of very low mass stars just above the hydrogen-burning limit. From the combined measurements of the Einstein radius and microlens parallax, we measure the masses of the binary components of 0.10 {+-} 0.01 M{sub sun} and 0.09 {+-} 0.01 M{sub sun}. This discovery demonstrates that microlensing will provide a method to measure the mass function of all Galactic populations of very low mass binaries that is independent of the biases caused by the luminosity of the population.

  17. REVEALING THE STRUCTURE OF AN ACCRETION DISK THROUGH ENERGY-DEPENDENT X-RAY MICROLENSING

    SciTech Connect

    Chartas, G.; Moore, D.; Kochanek, C. S.; Mosquera, A. M.; Blackburne, J. A.; Dai, X.

    2012-10-01

    We present results from monitoring observations of the gravitationally lensed quasar RX J1131-1231 performed with the Chandra X-Ray Observatory. The X-ray observations were planned with relatively long exposures that allowed a search for energy-dependent microlensing in the soft (0.2-2 keV) and hard (2-10 keV) light curves of the images of RX J1131-1231. We detect significant microlensing in the X-ray light curves of images A and D, and energy-dependent microlensing of image D. The magnification of the soft band appears to be larger than that in the hard band by a factor of {approx}1.3 when image D becomes more magnified. This can be explained by the difference between a compact, softer-spectrum corona that is producing a more extended, harder spectrum reflection component off the disk. This is supported by the evolution of the fluorescent iron line in image D over three consecutive time-averaged phases of the light curve. In the first period, an Fe line at E = 6.35{sup +0.14}{sub -0.14} keV is detected (at >99% confidence). In the second period, two Fe lines are detected, one at E = 5.50{sup +0.03}{sub -0.08} keV (detected at >99% confidence) and another at E = 6.04{sup +0.10}{sub -0.07} keV (marginally detected at >90% confidence), and in the third period, a broadened Fe line at 6.42{sup +0.16}{sub -0.14} keV is detected (at >99% confidence). This evolution of the Fe line profile during the microlensing event is consistent with the line distortion expected when a caustic passes over the inner disk where the shape of the fluorescent Fe line is distorted by general relativistic and Doppler effects.

  18. A femtosecond laser-induced two-photon photopolymerization technique for structuring microlenses

    NASA Astrophysics Data System (ADS)

    Malinauskas, Mangirdas; Gilbergs, Holger; Žukauskas, Albertas; Purlys, Vytautas; Paipulas, Domas; Gadonas, Roaldas

    2010-03-01

    Light-initiated quasi-instant solidification of a liquid polymer is attractive for its ultra-precise spatial and temporal control of the photochemical reaction. In this paper we present microlenses structured by femtosecond laser-induced photopolymerization. Due to nonlinear phenomena the fabrication resolution is not restricted to the diffraction limit for the applied laser excitation wavelength but is determined by the intensity of a focused beam. Furthermore, pin-point structuring enables one to produce three-dimensional structures of any form from the photopolymer. The smallest structural elements of 200 nm lateral dimensions can be achieved reproducibly by using high numerical aperture oil immersion focusing optics (NA = 1.4). Axial resolution (which is fundamentally a few times worse than lateral resolution due to the distribution of light intensity in the focal region) can be controlled to a precision of a few hundred nanometers by decreasing the scanning step. In our work we applied the commercially available and widely used zirconium-silicon based hybrid sol-gel photopolymer (Ormosil, SZ2080). Arrays of custom-parameter spherical microlenses for microscopy applications have been fabricated. Their surface roughness, focal distance and imaging quality were tested. The obtained results show potential for fast and flexible fabrication of custom-parameter microlenses by the proposed technique.

  19. One or more bound planets per Milky Way star from microlensing observations.

    PubMed

    Cassan, A; Kubas, D; Beaulieu, J-P; Dominik, M; Horne, K; Greenhill, J; Wambsganss, J; Menzies, J; Williams, A; Jørgensen, U G; Udalski, A; Bennett, D P; Albrow, M D; Batista, V; Brillant, S; Caldwell, J A R; Cole, A; Coutures, Ch; Cook, K H; Dieters, S; Prester, D Dominis; Donatowicz, J; Fouqué, P; Hill, K; Kains, N; Kane, S; Marquette, J-B; Martin, R; Pollard, K R; Sahu, K C; Vinter, C; Warren, D; Watson, B; Zub, M; Sumi, T; Szymański, M K; Kubiak, M; Poleski, R; Soszynski, I; Ulaczyk, K; Pietrzyński, G; Wyrzykowski, L

    2012-01-12

    Most known extrasolar planets (exoplanets) have been discovered using the radial velocity or transit methods. Both are biased towards planets that are relatively close to their parent stars, and studies find that around 17-30% (refs 4, 5) of solar-like stars host a planet. Gravitational microlensing, on the other hand, probes planets that are further away from their stars. Recently, a population of planets that are unbound or very far from their stars was discovered by microlensing. These planets are at least as numerous as the stars in the Milky Way. Here we report a statistical analysis of microlensing data (gathered in 2002-07) that reveals the fraction of bound planets 0.5-10 AU (Sun-Earth distance) from their stars. We find that 17(+6)(-9)% of stars host Jupiter-mass planets (0.3-10 M(J), where M(J) = 318 M(⊕) and M(⊕) is Earth's mass). Cool Neptunes (10-30 M(⊕)) and super-Earths (5-10 M(⊕)) are even more common: their respective abundances per star are 52(+22)(-29)% and 62(+35)(-37)%. We conclude that stars are orbited by planets as a rule, rather than the exception. PMID:22237108

  20. Test of relativistic gravity using microlensing of relativistically broadened lines in gravitationally lensed quasars

    NASA Astrophysics Data System (ADS)

    Neronov, A.; Vovk, Ie.

    2016-01-01

    We show that observation of the time-dependent effect of microlensing of relativistically broadened emission lines (such as e.g. the Fe K α line in x rays) in strongly lensed quasars could provide data on celestial mechanics of circular orbits in the direct vicinity of the horizon of supermassive black holes. This information can be extracted from the observation of evolution of the red/blue edge of the magnified line just before and just after the period of crossing of the innermost stable circular orbit by the microlensing caustic. The functional form of this evolution is insensitive to numerous astrophysical parameters of the accreting black hole and of the microlensing caustics network system (as opposed to the evolution of the full line spectrum). Measurement of the temporal evolution of the red/blue edge could provide a precision measurement of the radial dependence of the gravitational redshift and of velocity of the circular orbits, down to the innermost stable circular orbit. These measurements could be used to discriminate between general relativity and alternative models of the relativistic gravity in which the dynamics of photons and massive bodies orbiting the gravitating center is different from that of the geodesics in the Schwarzschild or Kerr space-times.

  1. Gravitational microlensing by low-mass objects in the globular cluster M22.

    PubMed

    Sahu, K C; Casertano, S; Livio, M; Gilliland, R L; Panagia, N; Albrow, M D; Potter, M

    2001-06-28

    Gravitational microlensing offers a means of determining directly the masses of objects ranging from planets to stars, provided that the distances and motions of the lenses and sources can be determined. A globular cluster observed against the dense stellar field of the Galactic bulge presents ideal conditions for such observations because the probability of lensing is high and the distances and kinematics of the lenses and sources are well constrained. The abundance of low-mass objects in a globular cluster is of particular interest, because it may be representative of the very early stages of star formation in the Universe, and therefore indicative of the amount of dark baryonic matter in such clusters. Here we report a microlensing event associated with the globular cluster M22. We determine the mass of the lens to be 0.13(+0.03)(-0.02) solar masses. We have also detected six events that are unresolved in time. If these are also microlensing events, they imply that a non-negligible fraction of the cluster mass resides in the form of free-floating planetary-mass objects. PMID:11429596

  2. Black hole, neutron star and white dwarf candidates from microlensing with OGLE-III★

    NASA Astrophysics Data System (ADS)

    Wyrzykowski, Ł.; Kostrzewa-Rutkowska, Z.; Skowron, J.; Rybicki, K. A.; Mróz, P.; Kozłowski, S.; Udalski, A.; Szymański, M. K.; Pietrzyński, G.; Soszyński, I.; Ulaczyk, K.; Pietrukowicz, P.; Poleski, R.; Pawlak, M.; Iłkiewicz, K.; Rattenbury, N. J.

    2016-05-01

    Most stellar remnants so far have been found in binary systems, where they interact with matter from their companions. Isolated neutron stars and black holes are difficult to find as they are dark, yet they are predicted to exist in our Galaxy in vast numbers. We explored the OGLE-III data base of 150 million objects observed in years 2001-2009 and found 59 microlensing events exhibiting a parallax effect due to the Earth's motion around the Sun. Combining parallax and brightness measurements from microlensing light curves with expected proper motions in the Milky Way, we identified 13 microlensing events which are consistent with having a white dwarf, neutron star or a black hole lens and we estimated their masses and distances. The most massive of our black hole candidates has 9.3 M⊙ and is at a distance of 2.4 kpc. The distribution of masses of our candidates indicates a continuum in mass distribution with no mass gap between neutron stars and black holes. We also present predictions on how such events will be observed by the astrometric Gaia mission.

  3. 3D imaging and characterization of microlenses and microlens arrays using nonlinear microscopy

    NASA Astrophysics Data System (ADS)

    Krmpot, Aleksandar J.; Tserevelakis, George J.; Murić, Branka D.; Filippidis, George; Pantelić, Dejan V.

    2013-05-01

    In this work, nonlinear laser scanning microscopy was employed for the characterization and three-dimensional (3D) imaging of microlenses and microlens arrays. Third-harmonic generation and two-photon excitation fluorescence (TPEF) signals were recorded and the obtained data were further processed in order to generate 3D reconstructions of the examined samples. Femtosecond laser pulses (1028 nm) were utilized for excitation. Microlenses were manufactured on Tot'hema and eosin sensitized gelatin layers using a green (532 nm) continuous wave laser beam using the direct laser writing method. The profiles of the microlens surface were obtained from the radial cross-sections, using a triple-Gaussian fit. The analytical shapes of the profiles were also used for ray tracing. Furthermore, the volumes of the microlenses were determined with high precision. The TPEF signal arising from the volume of the material was recorded and the respective 3D spatial fluorescence distribution of the samples was mapped. Nonlinear microscopy modalities have been shown to be a powerful diagnostic tool for microlens characterization as they enable in-depth investigations of the structural properties of the samples, in a nondestructive manner.

  4. THE EFFECT OF A TIME-VARYING ACCRETION DISK SIZE ON QUASAR MICROLENSING LIGHT CURVES

    SciTech Connect

    Blackburne, Jeffrey A.; Kochanek, Christopher S. E-mail: ckochanek@astronomy.ohio-state.ed

    2010-08-01

    Microlensing perturbations to the magnification of gravitationally lensed quasar images are dependent on the angular size of the quasar. If quasar variability at visible wavelengths is caused by a change in the area of the accretion disk, it will affect the microlensing magnification. We derive the expected signal, assuming that the luminosity scales with some power of the disk area, and estimate its amplitude using simulations. We discuss the prospects for detecting the effect in real-world data and for using it to estimate the logarithmic slope of the luminosity's dependence on disk area. Such an estimate would provide a direct test of the standard thin accretion disk model. We tried fitting six seasons of the light curves of the lensed quasar HE 0435-1223 including this effect as a modification to the Kochanek et al. approach to estimating time delays. We find a dramatic improvement in the goodness of fit and relatively plausible parameters, but a robust estimate will require a full numerical calculation in order to correctly model the strong correlations between the structure of the microlensing magnification patterns and the magnitude of the effect. We also comment briefly on the effect of this phenomenon for the stability of time-delay estimates.

  5. OGLE-III MICROLENSING EVENTS AND THE STRUCTURE OF THE GALACTIC BULGE

    SciTech Connect

    Wyrzykowski, Łukasz; Rynkiewicz, Alicja E.; Skowron, Jan; Kozłowski, Szymon; Udalski, Andrzej; Szymański, Michał K.; Kubiak, Marcin; Soszyński, Igor; Pietrzyński, Grzegorz; Poleski, Radosław; Pietrukowicz, Paweł; Pawlak, Michał

    2015-01-01

    We present and study the largest and most comprehensive catalog of microlensing events ever constructed. The sample of standard microlensing events comprises 3718 unique events from 2001-2009 with 1409 events that had not been detected before in real-time by the Early Warning System of the Optical Gravitational Lensing Experiment. The search pipeline uses machine learning algorithms to help find rare phenomena among 150 million objects and to derive the detection efficiency. Applications of the catalog can be numerous, from analyzing individual events to large statistical studies of the Galactic mass, kinematics distributions, and planetary abundances. We derive maps of the mean Einstein ring crossing time of events spanning 31 deg{sup 2} toward the Galactic center and compare the observed distributions with the most recent models. We find good agreement within the observed region and we see the signature of the tilt of the bar in the microlensing data. However, the asymmetry of the mean timescales seems to rise more steeply than predicted, indicating either a somewhat different orientation of the bar or a larger bar width. The map of events with sources in the Galactic bulge shows a dependence of the mean timescale on the Galactic latitude, signaling an increasing contribution from disk lenses closer to the plane relative to the height of the disk. Our data present a perfect set for comparing and enhancing new models of the central parts of the Milky Way and creating a three-dimensional picture of the Galaxy.

  6. Key techniques for space-based solar pumped semiconductor lasers

    NASA Astrophysics Data System (ADS)

    He, Yang; Xiong, Sheng-jun; Liu, Xiao-long; Han, Wei-hua

    2014-12-01

    In space, the absence of atmospheric turbulence, absorption, dispersion and aerosol factors on laser transmission. Therefore, space-based laser has important values in satellite communication, satellite attitude controlling, space debris clearing, and long distance energy transmission, etc. On the other hand, solar energy is a kind of clean and renewable resources, the average intensity of solar irradiation on the earth is 1353W/m2, and it is even higher in space. Therefore, the space-based solar pumped lasers has attracted much research in recent years, most research focuses on solar pumped solid state lasers and solar pumped fiber lasers. The two lasing principle is based on stimulated emission of the rare earth ions such as Nd, Yb, Cr. The rare earth ions absorb light only in narrow bands. This leads to inefficient absorption of the broad-band solar spectrum, and increases the system heating load, which make the system solar to laser power conversion efficiency very low. As a solar pumped semiconductor lasers could absorb all photons with energy greater than the bandgap. Thus, solar pumped semiconductor lasers could have considerably higher efficiencies than other solar pumped lasers. Besides, solar pumped semiconductor lasers has smaller volume chip, simpler structure and better heat dissipation, it can be mounted on a small satellite platform, can compose satellite array, which can greatly improve the output power of the system, and have flexible character. This paper summarizes the research progress of space-based solar pumped semiconductor lasers, analyses of the key technologies based on several application areas, including the processing of semiconductor chip, the design of small and efficient solar condenser, and the cooling system of lasers, etc. We conclude that the solar pumped vertical cavity surface-emitting semiconductor lasers will have a wide application prospects in the space.

  7. Space-based millimeter-wave debris tracking radar

    NASA Technical Reports Server (NTRS)

    Chang, Kai; Pollock, Michael A.; Skrehot, Michael K.

    1991-01-01

    NORAD system currently tracks and predicts orbits of space objects of 80 mm or larger in diameter. The small debris of less than 80 mm, traveling at high speed, could cause damage to Space Station or space vehicles. To overcome this problem, a 35 GHz space-based millimeter-wave radar system is proposed to track the particles ranging in size from 4 mm to 80 mm up to a range of 25 Km. The system requires a large phased array which should be developed in monolithic circuits for cost reduction.

  8. Space-based visible all-reflective stray light telescope

    NASA Astrophysics Data System (ADS)

    Wang, Dexter; Gardner, Leo R.; Wong, Wallace K.; Hadfield, Peter

    1991-08-01

    A 6-inch diameter aperture space-based visible telescope has been optimized to perform surveillance against the space background with earth albedo as a primary source of straylight. A three mirror off-axis anastigmat has been designed to cover a 1.4 degree(s) by 6.6 degree(s) field- of-view with 60 (mu) radian spatial resolution. The telescope body and optics are constructed of 6061-T6 aluminum to provide a thermally stable optical system. The optical elements are 'superfinished' to minimize scatter. Extensive baffles and stops are utilized to further reduce straylight. The telescope will be used on the Midcourse Space Experiment platform.

  9. Space-Based Gravitational-wave Mission Concept Studies

    NASA Technical Reports Server (NTRS)

    Livas, Jeffrey C.

    2012-01-01

    The LISA Mission Concept has been under study for over two decades as a spacebased gravitational-wave detector capable of observing astrophysical sources in the 0.0001 to 1 Hz band. The concept has consistently received strong recommendations from various review panels based on the expected science, most recently from the US Astr02010 Decadal Review. Budget constraints have led both the US and European Space agencies to search for lower cost options. We report results from the US effort to explore the tradeoffs between mission cost and science return, and in particular a family of mission concepts referred to as SGO (Space-based Gravitational-wave Observatory).

  10. Space based chemical lasers for ballistic missile defense (BMD)

    NASA Astrophysics Data System (ADS)

    Griff, N.; Kline, D. C.

    The potential for space-based chemical lasers (SBCLs) for use in ballisitic missile defense is discussed. The requirements for such use are reviewed, and the concept of phasing SBCL modules together on-orbit to obtain very high brightness systems is examined. The application of SBCLs to interactive discrimination is considered, and the readiness of SBCLs with regard to beam control, optics, acquisition/pointing/tracking, rapid retargeting, and coherent beam combination is addressed. The survivability of SBCLs in the context of an entire SDI system is discussed, including possible adversarial responses and design features to increase survivability.

  11. Two Phase Flow and Space-Based Applications

    NASA Technical Reports Server (NTRS)

    McQuillen, John

    1999-01-01

    A reduced gravity environment offers the ability to remove the effect of buoyancy on two phase flows whereby density differences that normally would promote relative velocities between the phases and also alter the shape of the interface are removed. However, besides being a potent research tool, there are also many space-based technologies that will either utilize or encounter two-phase flow behavior, and as a consequence, several questions must be addressed. This paper presents some of these technologies missions. Finally, this paper gives a description of web-sites for some funding.

  12. Decomposability and scalability in space-based observatory scheduling

    NASA Technical Reports Server (NTRS)

    Muscettola, Nicola; Smith, Stephen F.

    1992-01-01

    In this paper, we discuss issues of problem and model decomposition within the HSTS scheduling framework. HSTS was developed and originally applied in the context of the Hubble Space Telescope (HST) scheduling problem, motivated by the limitations of the current solution and, more generally, the insufficiency of classical planning and scheduling approaches in this problem context. We first summarize the salient architectural characteristics of HSTS and their relationship to previous scheduling and AI planning research. Then, we describe some key problem decomposition techniques supported by HSTS and underlying our integrated planning and scheduling approach, and we discuss the leverage they provide in solving space-based observatory scheduling problems.

  13. Comet/Asteroid Protection System (CAPS): Preliminary Space-Based Concept and Study Results

    NASA Technical Reports Server (NTRS)

    Mazanek, Daniel D.; Roithmayr, Carlos M.; Antol, Jeffrey; Park, Sang-Young; Koons, Robert H.; Bremer, James C.; Murphy, Douglas G.; Hoffman, James A.; Kumar, Renjith R.; Seywald, Hans

    2005-01-01

    There exists an infrequent, but significant hazard to life and property due to impacting asteroids and comets. There is currently no specific search for long-period comets, smaller near-Earth asteroids, or smaller short-period comets. These objects represent a threat with potentially little or no warning time using conventional ground-based telescopes. These planetary bodies also represent a significant resource for commercial exploitation, long-term sustained space exploration, and scientific research. The Comet/Asteroid Protection System (CAPS) is a future space-based system concept that provides permanent, continuous asteroid and comet monitoring, and rapid, controlled modification of the orbital trajectories of selected bodies. CAPS would expand the current detection effort to include long-period comets, as well as small asteroids and short-period comets capable of regional destruction. A space-based detection system, despite being more costly and complex than Earth-based initiatives, is the most promising way of expanding the range of detectable objects, and surveying the entire celestial sky on a regular basis. CAPS would provide an orbit modification system capable of diverting kilometer class objects, and modifying the orbits of smaller asteroids for impact defense and resource utilization. This Technical Memorandum provides a compilation of key related topics and analyses performed during the CAPS study, which was performed under the Revolutionary Aerospace Systems Concepts (RASC) program, and discusses technologies that could enable the implementation of this future system.

  14. Reanalyses of Anomalous Gravitational Microlensing Events in the OGLE-III Early Warning System Database with Combined Data

    NASA Astrophysics Data System (ADS)

    Jeong, J.; Park, H.; Han, C.; Gould, A.; Udalski, A.; Szymański, M. K.; Pietrzyński, G.; Soszyński, I.; Poleski, R.; Ulaczyk, K.; Wyrzykowski, Ł.; OGLE Collaboration; Abe, F.; Bennett, D. P.; Bond, I. A.; Botzler, C. S.; Freeman, M.; Fukui, A.; Fukunaga, D.; Itow, Y.; Koshimoto, N.; Masuda, K.; Matsubara, Y.; Muraki, Y.; Namba, S.; Ohnishi, K.; Rattenbury, N. J.; Saito, To.; Sullivan, D. J.; Sweatman, W. L.; Sumi, T.; Suzuki, D.; Tristram, P. J.; Tsurumi, N.; Wada, K.; Yamai, N.; Yock, P. C. M.; Yonehara, A.; MOA Collaboration; Albrow, M. D.; Batista, V.; Beaulieu, J.-P.; Caldwell, J. A. R.; Cassan, A.; Cole, A.; Coutures, C.; Dieters, S.; Dominik, M.; Dominis Prester, D.; Donatowicz, J.; Fouqué, P.; Greenhill, J.; Hoffman, M.; Huber, M.; Jørgensen, U. G.; Kane, S. R.; Kubas, D.; Martin, R.; Marquette, J.-B.; Menzies, J.; Pitrou, C.; Pollard, K.; Sahu, K. C.; Vinter, C.; Wambsganss, J.; Williams, A.; PLANET Collaboration; Allen, W.; Bolt, G.; Choi, J.-Y.; Christie, G. W.; DePoy, D. L.; Drummond, J.; Gaudi, B. S.; Hwang, K.-H.; Jung, Y. K.; Lee, C.-U.; Mallia, F.; Maoz, D.; Maury, A.; McCormick, J.; Monard, L. A. G.; Moorhouse, D.; Natusch, T.; Ofek, E. O.; Park, B.-G.; Pogge, R. W.; Santallo, R.; Shin, I.-G.; Thornley, G.; Yee, J. C.; μFUN Collaboration; Bramich, D. M.; Burgdorf, M.; Horne, K.; Hundertmark, M.; Kains, N.; Snodgrass, C.; Steele, I.; Street, R.; Tsapras, Y.; RoboNet Collaboration

    2015-05-01

    We reanalyze microlensing events in the published list of anomalous events that were observed from the Optical Gravitational Lensing Experiment (OGLE) lensing survey conducted during the 2004-2008 period. In order to check the existence of possible degenerate solutions and extract extra information, we conduct analyses based on combined data from other survey and follow-up observation and consider higher-order effects. Among the analyzed events, we present analyses of eight events for which either new solutions are identified or additional information is obtained. We find that the previous binary-source interpretations of five events are better interpreted by binary-lens models. These events include OGLE-2006-BLG-238, OGLE-2007-BLG-159, OGLE-2007-BLG-491, OGLE-2008-BLG-143, and OGLE-2008-BLG-210. With additional data covering caustic crossings, we detect finite-source effects for six events including OGLE-2006-BLG-215, OGLE-2006-BLG-238, OGLE-2006-BLG-450, OGLE-2008-BLG-143, OGLE-2008-BLG-210, and OGLE-2008-BLG-513. Among them, we are able to measure the Einstein radii of three events for which multi-band data are available. These events are OGLE-2006-BLG-238, OGLE-2008-BLG-210, and OGLE-2008-BLG-513. For OGLE-2008-BLG-143, we detect higher-order effects induced by the changes of the observer’s position caused by the orbital motion of the Earth around the Sun. In addition, we present degenerate solutions resulting from the known close/wide or ecliptic degeneracy. Finally, we note that the masses of the binary companions of the lenses of OGLE-2006-BLG-450 and OGLE-2008-BLG-210 are in the brown-dwarf regime.

  15. Future Prospects for Space-Based Gamma Ray Astronomy

    NASA Astrophysics Data System (ADS)

    McConnell, Mark

    2015-04-01

    The gamma-ray sky offers a unique view into broad range of astrophysical phenomena, from nearby solar flares, to galactic pulsars, to gamma-ray bursts at the furthest reaches of the Universe. The Fermi mission has dramatically demonstrated the broad range of topics that can be addressed by gamma-ray observations. The full range of gamma-ray energies is quite broad, covering the electromagnetic spectrum at energies above about 100 keV. The energy range below several hundred GeV is the domain of space-based gamma-ray observatories, a range that is not completely covered by the Fermi LAT instrument. The gamma ray community has recently embarked on an effort to define the next steps for space-based gamma ray astronomy. These discussions are being facilitated through the Gamma-ray Science Interest Group (GammaSIG), which exists to provide community input to NASA in regards to current and future needs of the gamma-ray astrophysics community. The GammaSIG, as a part of the Physics of the Cosmos Program Analysis Group, provides a forum open to all members of the gamma-ray community. The GammaSIG is currently working to bring the community together with a common vision that will be expressed in the form of a community roadmap. This talk will summarize some of the latest results from active gamma ray observatories, including both Fermi and INTEGRAL, and will summarize the status of the community roadmap effort.

  16. Maritime traffic monitoring using a space-based AIS receiver

    NASA Astrophysics Data System (ADS)

    Eriksen, Torkild; Høye, Gudrun; Narheim, Bjørn; Meland, Bente Jensløkken

    2006-05-01

    The Automatic Identification System (AIS) is a maritime safety and vessel traffic system imposed by the International Maritime Organization (IMO). The system broadcasts position reports and short messages with information about the ship and the voyage. Using frequencies in the maritime VHF band, the coverage is similar to other VHF applications, and is essentially dependent on the altitude of the antenna. For ship-to-ship communications the range is typically 20 nautical miles and for ship-to-shore up to 40 nm. A space-based AIS receiver in low earth orbit will have a range to the horizon of more than 1000 nm, giving an excellent opportunity for large-area ocean surveillance. The Norwegian Defence Research Establishment (FFI) has performed a feasibility study on reception of AIS messages from space. The results show that a ship detection probability of near 100% can be obtained for up to 1000 ships within the coverage area, and that for a standard AIS receiver a signal power margin of 10-20 dB can be achieved. On this background, swath-width analyses for European scenarios are done. It is argued that space-based reception of AIS messages is a promising way of achieving long-range identification and tracking services at marginal cost.

  17. Concept for lightweight spaced-based deposition technology

    SciTech Connect

    Fulton, Michael; Anders, Andre

    2006-02-28

    In this contribution we will describe a technology path to very high quality coatings fabricated in the vacuum of space. To accomplish the ambitious goals set out in NASA's Lunar-Mars proposal, advanced thin-film deposition technology will be required. The ability to deposit thin-film coatings in the vacuum of lunar-space could be extremely valuable for executing this new space mission. Developing lightweight space-based deposition technology (goal:<300 g, including power supply) will enable the future fabrication and repair of flexible large-area space antennae and fixed telescope mirrors for lunar-station observatories. Filtered Cathodic Arc (FCA) is a proven terrestrial energetic thin-film deposition technology that does not need any processing gas but is well suited for ultra-high vacuum operation. Recently, miniaturized cathodic arcs have already been developed and considered for space propulsion. It is proposed to combine miniaturized pulsed FCA technology and robotics to create a robust, enabling space-based deposition system for the fabrication, improvement, and repair of thin films, especially of silver and aluminum, on telescope mirrors and eventually on large area flexible substrates. Using miniature power supplies with inductive storage, the typical low-voltage supply systems used in space are adequate. It is shown that high-value, small area coatings are within the reach of existing technology, while medium and large area coatings are challenging in terms of lightweight technology and economics.

  18. Future Prospects for Space-Based Gamma Ray Astronomy

    NASA Astrophysics Data System (ADS)

    McConnell, Mark

    2016-03-01

    The gamma-ray sky offers a unique view into broad range of high energy astrophysical phenomena, from nearby solar flares, to galactic pulsars, to gamma-ray bursts at the furthest reaches of the Universe. In recent years, results from the Fermi mission have further demonstrated the broad range of topics that can be addressed by gamma-ray observations. The full range of gamma-ray energies is quite broad, from about 100 keV up to about 100 TeV. The energy range below several hundred GeV is the domain of space-based gamma-ray observatories, a range that is not completely covered by the Fermi LAT instrument. The gamma ray community has embarked on an effort to define the next steps for space-based gamma ray astronomy. These discussions are being facilitated through the Gamma-ray Science Interest Group (GammaSIG), which exists to provide community input to NASA in regards to current and future needs of the gamma-ray astrophysics community. Through a series of workshops and symposia, the GammaSIG is working to bring the community together with one common vision, a vision that will be expressed in the form of a community roadmap. This talk will summarize some of the latest results from active gamma ray observatories and will summarize the status of the community roadmap effort.

  19. Overview of the space-based laser (SBL) program

    NASA Astrophysics Data System (ADS)

    Riker, James F.

    2002-06-01

    The Space Based Laser (SBL) program is concerned with both near-term feasibility of space lasers and also the desired operational capability for a robust SBL constellation. For the near term system, we have defined an Integrated Flight Experiment (IFX) that will integrate a high power laser device, a beam control system, and a large beam director, performing a lethal engagement against a boosting missile in the 2010-2014 time period. For the operational system, the program was conducted its Affordability and Architecture Study (AAS) for Dr. Jacques Gansler (former USD(AT&L)). We arrived at a particular set of solutions for a prescribed threat. These solutions include both pure SBL constellations and also combinations of SBL satellites and space-based relay mirrors (SBM). We also considered Air Borne Lasers (ABL) and Ground Based lasers (GBL) as complements to the SBL and SBM. In this paper, we describe the current status of both the IFX program, which is the principal recipient of current funding, and also a nascent SBL Technology program to address the needs of the operational system. For the technology program, we analyzed the specific technology areas we need to develop in order to realize the most pay off for operational SBL systems.

  20. 33-Foot-Diameter Space Station Leading to Space Base

    NASA Technical Reports Server (NTRS)

    1969-01-01

    This picture illustrates a concept of a 33-Foot-Diameter Space Station Leading to a Space Base. In-house work of the Marshall Space Flight Center, as well as a Phase B contract with the McDornel Douglas Astronautics Company, resulted in a preliminary design for a space station in 1969 and l970. The Marshall-McDonnel Douglas approach envisioned the use of two common modules as the core configuration of a 12-man space station. Each common module was 33 feet in diameter and 40 feet in length and provided the building blocks, not only for the space station, but also for a 50-man space base. Coupled together, the two modules would form a four-deck facility: two decks for laboratories and two decks for operations and living quarters. Zero-gravity would be the normal mode of operation, although the station would have an artificial gravity capability. This general-purpose orbital facility was to provide wide-ranging research capabilities. The design of the facility was driven by the need to accommodate a broad spectrum of activities in support of astronomy, astrophysics, aerospace medicine, biology, materials processing, space physics, and space manufacturing. To serve the needs of Earth observations, the station was to be placed in a 242-nautical-mile orbit at a 55-degree inclination. An Intermediate-21 vehicle (comprised of Saturn S-IC and S-II stages) would have launched the station in 1977.

  1. Special Relativity Corrections for Space-Based Lidars

    NASA Technical Reports Server (NTRS)

    RaoGudimetla, Venkata S.; Kavaya, Michael J.

    1999-01-01

    The theory of special relativity is used to analyze some of the physical phenomena associated with space-based coherent Doppler lidars aimed at Earth and the atmosphere. Two important cases of diffuse scattering and retroreflection by lidar targets are treated. For the case of diffuse scattering, we show that for a coaligned transmitter and receiver on the moving satellite, there is no angle between transmitted and returned radiation. However, the ray that enters the receiver does not correspond to a retroreflected ray by the target. For the retroreflection case there is misalignment between the transmitted ray and the received ray. In addition, the Doppler shift in the frequency and the amount of tip for the receiver aperture when needed are calculated, The error in estimating wind because of the Doppler shift in the frequency due to special relativity effects is examined. The results are then applied to a proposed space-based pulsed coherent Doppler lidar at NASA's Marshall Space Flight Center for wind and aerosol backscatter measurements. The lidar uses an orbiting spacecraft with a pulsed laser source and measures the Doppler shift between the transmitted and the received frequencies to determine the atmospheric wind velocities. We show that the special relativity effects are small for the proposed system.

  2. Quantifying the tracking capability of space-based AIS systems

    NASA Astrophysics Data System (ADS)

    Skauen, Andreas Nordmo

    2016-01-01

    The Norwegian Defence Research Establishment (FFI) has operated three Automatic Identification System (AIS) receivers in space. Two are on dedicated nano-satellites, AISSat-1 and AISSat-2. The third, the NORAIS Receiver, was installed on the International Space Station. A general method for calculating the upper bound on the tracking capability of a space-based AIS system has been developed and the results from the algorithm applied to AISSat-1 and the NORAIS Receiver individually. In addition, a constellation of AISSat-1 and AISSat-2 is presented. The tracking capability is defined as the probability of re-detecting ships as they move around the globe and is explained to represent and upper bound on a space-based AIS system performance. AISSat-1 and AISSat-2 operates on the nominal AIS1 and AIS2 channels, while the NORAIS Receiver data used are from operations on the dedicated space AIS channels, AIS3 and AIS4. The improved tracking capability of operations on the space AIS channels is presented.

  3. Special relativity corrections for space-based lidars.

    PubMed

    Gudimetla, V S; Kavaya, M J

    1999-10-20

    The theory of special relativity is used to analyze some of the physical phenomena associated with space-based coherent Doppler lidars aimed at Earth and the atmosphere. Two important cases of diffuse scattering and retroreflection by lidar targets are treated. For the case of diffuse scattering, we show that for a coaligned transmitter and receiver on the moving satellite, there is no angle between transmitted and returned radiation. However, the ray that enters the receiver does not correspond to a retroreflected ray by the target. For the retroreflection case there is misalignment between the transmitted ray and the received ray. In addition, the Doppler shift in the frequency and the amount of tip for the receiver aperture when needed are calculated. The error in estimating wind because of the Doppler shift in the frequency due to special relativity effects is examined. The results are then applied to a proposed space-based pulsed coherent Doppler lidar at NASA's Marshall Space Flight Center for wind and aerosol backscatter measurements. The lidar uses an orbiting spacecraft with a pulsed laser source and measures the Doppler shift between the transmitted and the received frequencies to determine the atmospheric wind velocities. We show that the special relativity effects are small for the proposed system. PMID:18324167

  4. The different origins of high- and low-ionization broad emission lines revealed by gravitational microlensing in the Einstein cross

    NASA Astrophysics Data System (ADS)

    Braibant, L.; Hutsemékers, D.; Sluse, D.; Anguita, T.

    2016-07-01

    We investigate the kinematics and ionization structure of the broad emission line region of the gravitationally lensed quasar QSO2237+0305 (the Einstein cross) using differential microlensing in the high- and low-ionization broad emission lines. We combine visible and near-infrared spectra of the four images of the lensed quasar and detect a large-amplitude microlensing effect distorting the high-ionization CIV and low-ionization Hα line profiles in image A. While microlensing only magnifies the red wing of the Balmer line, it symmetrically magnifies the wings of the CIV emission line. Given that the same microlensing pattern magnifies both the high- and low-ionization broad emission line regions, these dissimilar distortions of the line profiles suggest that the high- and low-ionization regions are governed by different kinematics. Since this quasar is likely viewed at intermediate inclination, we argue that the differential magnification of the blue and red wings of Hα favors a flattened, virialized, low-ionization region whereas the symmetric microlensing effect measured in CIV can be reproduced by an emission line formed in a polar wind, without the need of fine-tuned caustic configurations. Based on observations made with the ESO-VLT, Paranal, Chile; Proposals 076.B-0197 and 076.B-0607 (PI: Courbin).

  5. Numerical Simulation of Refractive-Microlensed HgCdTe Infrared Focal Plane Arrays Operating in Optical Systems

    NASA Astrophysics Data System (ADS)

    Li, Yang; Ye, Zhen-Hua; Hu, Wei-Da; Lei, Wen; Gao, Yan-Lin; He, Kai; Hua, Hua; Zhang, Peng; Chen, Yi-Yu; Lin, Chun; Hu, Xiao-Ning; Ding, Rui-Jun; He, Li

    2014-08-01

    The optoelectronic performance of the mid-wavelength HgCdTe infrared focal plane array (IRFPA) with refractive microlenses integrated on its CdZnTe substrate has been numerically simulated. A reduced light-distribution model based on scalar Kirchhoff diffraction theory was adopted to reveal the true behavior of IRFPAs operating in an optical system under imaging conditions. The pixel crosstalk obtained and the energy-gathering characteristics demonstrated that the microlenses can delay the rise in crosstalk when the image point shifts toward pixel boundaries, and can restrict the major optical absorption process in any case within a narrow region around the pixel center. The dependence of the microlenses' effects on the system's properties was also analyzed; this showed that intermediate relative aperture and small microlens radius are required for optimized device performance. Simulation results also indicated that for detectors farther from the center of the field of view, the efficacy of microlenses in crosstalk suppression and energy gathering is still maintained, except for a negligible difference in the lateral magnification from an ordinary array without microlenses.

  6. 78 FR 68816 - Proposed Information Collection; Comment Request; NOAA Space-Based Data Collection System (DCS...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-11-15

    ... National Oceanic and Atmospheric Administration Proposed Information Collection; Comment Request; NOAA Space- Based Data Collection System (DCS) Agreements AGENCY: National Oceanic and Atmospheric... National Ocean and Atmospheric Administration (NOAA) operates two space-based data collection systems...

  7. 75 FR 59686 - Proposed Information Collection; Comment Request; NOAA Space-Based Data Collection System (DCS...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-09-28

    ... National Oceanic and Atmospheric Administration Proposed Information Collection; Comment Request; NOAA Space- Based Data Collection System (DCS) Agreements AGENCY: National Oceanic and Atmospheric... space-based data collection systems (DCS), the Geostationary Operational Environmental Satellite...

  8. Navigation and control considerations for space based orbital maneuvering systems

    NASA Technical Reports Server (NTRS)

    Brandon, L.

    1984-01-01

    Various design areas of concern in navigation and control of space-based orbital maneuvering systems such as those on the Orbiter are discussed, with note taken of approach maneuvers. Design problems occur in the areas of storage modes, sensing, activation methods, navigation, target/mission determination, rendezvous and docking schemes, reliability, and commonality between low- and high-energy maneuvering vehicles. Navigation may be in autonomous or nonautonomous modes and may include ground-baed computations and commands via the TDRSS or NORAD systems. Autonomous operations would interface with the GPS. All the concepts discussed are significant for the planned orbital transfer and orbital maneuvering vehicles, which would be used to place satellites in orbit and repair or retrieve them.

  9. Infrared Fibers for Use in Space-Based Smart Structures

    NASA Technical Reports Server (NTRS)

    Tucker, Dennis S.; Nettles, Alan T.; Brantley, Lott W. (Technical Monitor)

    2001-01-01

    Infrared optical fibers are finding a number of applications including laser surgery, remote sensing, and nuclear radiation resistant links. Utilizing these fibers in space-based structures is another application, which can be exploited. Acoustic and thermal sensing are two areas in which these fibers could be utilized. In particular, fibers could be embedded in IM7/8552 toughened epoxy and incorporated into space structures both external and internal. ZBLAN optical fibers are a candidate, which have been studied extensively over the past 20 years for terrestrial applications. For the past seven years the effects of gravity on the crystallization behavior of ZBLAN optical fiber has been studied. It has been found that ZBLAN crystallization is suppressed in microgravity. This lack of crystallization leads to a fiber with better transmission characteristics than its terrestrial counterpart.

  10. Studying inflation with future space-based gravitational wave detectors

    SciTech Connect

    Jinno, Ryusuke; Moroi, Takeo; Takahashi, Tomo E-mail: moroi@phys.s.u-tokyo.ac.jp

    2014-12-01

    Motivated by recent progress in our understanding of the B-mode polarization of cosmic microwave background (CMB), which provides important information about the inflationary gravitational waves (IGWs), we study the possibility to acquire information about the early universe using future space-based gravitational wave (GW) detectors. We perform a detailed statistical analysis to estimate how well we can determine the reheating temperature after inflation as well as the amplitude, the tensor spectral index, and the running of the inflationary gravitational waves. We discuss how the accuracies depend on noise parameters of the detector and the minimum frequency available in the analysis. Implication of such a study on the test of inflation models is also discussed.

  11. Phytoplankton photocompensation from space-based fluorescence measurements

    NASA Astrophysics Data System (ADS)

    Morrison, J. Ruairidh; Goodwin, Deborah S.

    2010-03-01

    Recent satellite-derived observations linked global scale phytoplankton fluorescence variability with iron stress and hinted at photophysiological responses associated with changing light levels. These photocompensation reactions, the sum of photoacclimation and photoadaptation, were examined with climatological data for the Gulf of Maine. Significant seasonal variability was observed in the fluorescence quantum yield that was unrelated to patterns of biomass. Up to 89% of the variability in the fluorescence quantum yield was explained by a physiology-based photocompensation model. Spatial variability in seasonal patterns was associated with differing hydrodynamic regimes. This variability in the quantum yield demonstrates that satellite-based fluorescence is inappropriate for phytoplankton biomass determinations. More importantly, the work presented here provides the modeling foundation for fluorescence-based investigations of temporal and spatial variability in phytoplankton physiology associated with growth irradiance. These space-based physiological observations have the potential to decrease uncertainties in future ocean color derived primary productivity estimates.

  12. Multi-Tethered Space-Based Interferometers: Particle System Model

    NASA Technical Reports Server (NTRS)

    Gates, Stephen S.

    2001-01-01

    Dynamics models are presented for a class of space-based interferometers comprised of multiple component bodies, interconnected in various arrangements, by low-mass flexible tethers of variable length. The tethered constellations are to perform coordinated rotational scanning accompanied by baseline dimensional changes, as well as spin axis realignments and spin-up/spin-down maneuvers. The mechanical idealization is a system of N point masses interconnected by massless tethers of variable length. Both extensible and inextensible tethers are considered. Expressions for system angular and linear momenta are developed. The unrestricted nonlinear motion equations are derived via Lagranges equations. Rheonomic constraints are introduced to allow prescribed motion of any degrees of freedom, and the associated physical forces are determined. The linearized equations of motion are obtained for the steady rotation of a system with extensible tethers of constant unstrained length.

  13. Space-Based Information Infrastructure Architecture for Broadband Services

    NASA Technical Reports Server (NTRS)

    Price, Kent M.; Inukai, Tom; Razdan, Rajendev; Lazeav, Yvonne M.

    1996-01-01

    This study addressed four tasks: (1) identify satellite-addressable information infrastructure markets; (2) perform network analysis for space-based information infrastructure; (3) develop conceptual architectures; and (4) economic assessment of architectures. The report concludes that satellites will have a major role in the national and global information infrastructure, requiring seamless integration between terrestrial and satellite networks. The proposed LEO, MEO, and GEO satellite systems have satellite characteristics that vary widely. They include delay, delay variations, poorer link quality and beam/satellite handover. The barriers against seamless interoperability between satellite and terrestrial networks are discussed. These barriers are the lack of compatible parameters, standards and protocols, which are presently being evaluated and reduced.

  14. MEMS-Based Communications Systems for Space-Based Applications

    NASA Technical Reports Server (NTRS)

    DeLosSantos, Hector J.; Brunner, Robert A.; Lam, Juan F.; Hackett, Le Roy H.; Lohr, Ross F., Jr.; Larson, Lawrence E.; Loo, Robert Y.; Matloubian, Mehran; Tangonan, Gregory L.

    1995-01-01

    As user demand for higher capacity and flexibility in communications satellites increases, new ways to cope with the inherent limitations posed by the prohibitive mass and power consumption, needed to satisfy those requirements, are under investigation. Recent studies suggest that while new satellite architectures are necessary to enable multi-user, multi-data rate, multi-location satellite links, these new architectures will inevitably increase power consumption, and in turn, spacecraft mass, to such an extent that their successful implementation will demand novel lightweight/low power hardware approaches. In this paper, following a brief introduction to the fundamentals of communications satellites, we address the impact of micro-electro-mechanical systems (MEMS) technology, in particular micro-electro-mechanical (MEM) switches to mitigate the above mentioned problems and show that low-loss/wide bandwidth MEM switches will go a long way towards enabling higher capacity and flexibility space-based communications systems.

  15. Atmospheric Cloud Forecasting in Support of Space Based Applications

    NASA Astrophysics Data System (ADS)

    Alliss, R. J.; Felton, B.; Apling, D.

    2013-09-01

    Many space based applications from imaging to communications are impacted by the atmosphere. Atmospheric impacts such as optical turbulence and clouds are the main drivers for these types of systems. For example, in space based optical communications, clouds will produce channel fades on the order of many hundreds of decibels (dB) thereby breaking the communication link. Optical turbulence can also produce fades but can be compensated for by adaptive optics. The ability to forecast the current and future location and optical thickness of clouds for spaced based to ground optical communications is therefore critical in order to achieve a highly reliable system. We have developed an innovative method for producing such forecasts. These forecasts are intended to provide lead times on the order of several hours so that communication links can be transferred from a current clear ground location to another more desirable ground site. The system is referred to as the Cloud Propagator Forecast (CPF) and it operates on successive, satellite remotely sensed, cloud analyses to produce reliable probability forecasts of future cloud cover conditions at each point location or for the expectation of the amount of skycover in a local skydome about each point location. The forecasting algorithm is a combination of empirical Lagrangian and Eulerian regression over multiple spatial scales, but treats time auto-regressively. Input cloud masks are transformed into proxies first. A cloud cover proxy is a variable which has a more Gaussian distribution than literal cloud cover. For a given pixel, the cloud cover proxy is computed first by determining whether at the initialization time the pixel was clear or cloudy. Clear pixels will be assigned only positive proxies; cloudy pixels will be given only negative proxies. The degree the assigned proxy is different than zero depends on the fraction of pixels in a small neighboring space which have similar cloudy/clearness. The neighboring

  16. Dehumidification via membrane separation for space-based applications

    NASA Technical Reports Server (NTRS)

    Gienger, Jane Kucera; Ray, Roderick J.; Chullen, Cinda

    1988-01-01

    The paper describes the development of a membrane-based dehumidification process for space-based applications, such as spacecraft cabins and EVA space suits. Results presented are from: (1) screening tests conducted to determine the efficacy of various membranes to separate water vapor from air, and (2) parametric and long-term tests of membranes operated at conditions that simulate the range of environmental conditions (e.g., temperature and relative humidity) expected in the planned Space Station. Also included in this paper is a discussion of preliminary designs of membrane-based dehumidification processes for the Space Station and EVA space suits. These designs result in compact and energy-efficient systems that offer significant advantages over conventional dehumidification processes.

  17. One GHz digitizer for space based laser altimeter

    NASA Technical Reports Server (NTRS)

    Staples, Edward J.

    1991-01-01

    This is the final report for the research and development of the one GHz digitizer for space based laser altimeter. A feasibility model was designed, built, and tested. Only partial testing of essential functions of the digitizer was completed. Hybrid technology was incorporated which allows analog storage (memory) of the digitally sampled data. The actual sampling rate is 62.5 MHz, but executed in 16 parallel channels, to provide an effective sampling rate of one GHz. The average power consumption of the one GHz digitizer is not more than 1.5 Watts. A one GHz oscillator is incorporated for timing purposes. This signal is also made available externally for system timing. A software package was also developed for internal use (controls, commands, etc.) and for data communication with the host computer. The digitizer is equipped with an onboard microprocessor for this purpose.

  18. ISS Space-Based Science Operations Grid for the Ground Systems Architecture Workshop (GSAW)

    NASA Technical Reports Server (NTRS)

    Welch, Clara; Bradford, Bob

    2003-01-01

    Contents include the following:What is grid? Benefits of a grid to space-based science operations. Our approach. Score of prototype grid. The security question. Short term objectives. Long term objectives. Space-based services required for operations. The prototype. Score of prototype grid. Prototype service layout. Space-based science grid service components.

  19. 76 FR 30202 - National Space-Based Positioning, Navigation, and Timing (PNT) Advisory Board; Meeting

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-05-24

    ... following topics: Update on U.S. Space-Based PNT Policy and Global Positioning System (GPS) modernization... SPACE ADMINISTRATION National Space-Based Positioning, Navigation, and Timing (PNT) Advisory Board.... Space-Based Positioning, Navigation, and Timing (PNT) Policy, the National Aeronautics and...

  20. Space Based Ornithology: On the Wings of Migration and Biophysics

    NASA Technical Reports Server (NTRS)

    Smith, James A.

    2005-01-01

    The study of bird migration on a global scale is one of the compelling and challenging problems of modern biology with major implications for human health and conservation biology. Migration and conservation efforts cross national boundaries and are subject to numerous international agreements and treaties. Space based technology offers new opportunities to shed understanding on the distribution and migration of organisms on the planet and their sensitivity to human disturbances and environmental changes. Migration is an incredibly diverse and complex behavior. A broad outline of space based research must address three fundamental questions: (1) where could birds be, i.e. what is their fundamental niche constrained by their biophysical limits? (2) where do we actually find birds, i.e. what is their realizable niche as modified by local or regional abiotic and biotic factors, and (3) how do they get there (and how do we know?), that is what are their migration patterns and associated mechanisms? Our working hypothesis is that individual organism biophysical models of energy and water balance, driven by satellite measurements of spatio-temporal gradients in climate and habitat, will help us to explain the variability in avian species richness and distribution. Dynamic state variable modeling provides one tool for studying bird migration across multiple scales and can be linked to mechanistic models describing the time and energy budget states of migrating birds. Such models yield an understanding of how a migratory flyway and its component habitats function as a whole and link stop-over ecology with biological conservation and management. Further these models provide an ecological forecasting tool for science and application users to address what are the possible consequences of loss of wetlands, flooding, drought or other natural disasters such as hurricanes on avian biodiversity and bird migration.

  1. Characterizing Exoplanets with 2-meter Class Space-based Coronagraphs

    NASA Astrophysics Data System (ADS)

    Robinson, T. D.; Marley, M. S.; Stapelfeldt, K. R.

    2015-12-01

    Several concepts now exist for small, space-based missions to directly characterize exoplanets in reflected light. In this presentation, we explore how instrumental and astrophysical parameters will affect the ability of such missions to obtain spectral and photometric observations that are useful for characterizing their planetary targets. We discuss the development of an instrument noise model suitable for studying the spectral characterization potential of a coronagraph-equipped, space-based telescope. To be consistent with near-future missions and technologies, we assume a baseline set of telescope and instrument parameters that include a 2 meter diameter primary aperture, an operational wavelength range of 0.4-1.0 μm, and an instrument spectral resolution of λ/Δλ=70. We present applications of our baseline noise simulator to a variety of spectral models of different planet types, emphasizing Earth-like planets. With our exoplanet spectral models, we explore wavelength-dependent planet-star flux ratios for main sequence stars of various effective temperatures, and discuss how coronagraph inner and outer working angle constraints will influence the potential to study different types of planets. For planets most favorable to spectroscopic characterization—including nearby Earth twins and super-Earths—we study the integration times required to achieve moderate signal-to-noise ratio spectra. We also explore the sensitivity of the integration times required to detect the base of key absorption bands (for water vapor and molecular oxygen) to coronagraph raw contrast performance, exozodiacal light levels, and the distance to the planetary system. We will also discuss prospects for detecting ocean glint, a habitability signature, from nearby Earth-like planets, as well as the extension of our models to a more distant future Large UV-Optical-InfraRed (LUVOIR) mission.

  2. The Heated Halo for Space-Based Blackbody Emissivity Measurement

    NASA Astrophysics Data System (ADS)

    Gero, P.; Taylor, J. K.; Best, F. A.; Revercomb, H. E.; Garcia, R. K.; Adler, D. P.; Ciganovich, N. N.; Knuteson, R. O.; Tobin, D. C.

    2012-12-01

    The accuracy of radiance measurements with space-based infrared spectrometers is contingent on the quality of the calibration subsystem, as well as knowledge of its uncertainty. Upcoming climate benchmark missions call for measurement uncertainties better than 0.1 K (k=3) in radiance temperature for the detection of spectral climate signatures. Blackbody cavities impart the most accurate calibration for spaceborne infrared sensors, provided that their temperature and emissivity is traceably determined on-orbit. The On-Orbit Absolute Radiance Standard (OARS) has been developed at the University of Wisconsin and has undergone further refinement under the NASA Instrument Incubator Program (IIP) to meet the stringent requirements of the next generation of infrared remote sensing instruments. It provides on-orbit determination of both traceable temperature and emissivity for calibration blackbodies. The Heated Halo is the component of the OARS that provides a robust and compact method to measure the spectral emissivity of a blackbody in situ. A carefully baffled thermal source is placed in front of a blackbody in an infrared spectrometer system, and the combined radiance of the blackbody and Heated Halo reflection is observed. Knowledge of key temperatures and the viewing geometry allow the blackbody cavity spectral emissivity to be calculated. We present the results from the Heated Halo methodology implemented with a new Absolute Radiance Interferometer (ARI), which is a prototype space-based infrared spectrometer designed for climate benchmarking. We show the evolution of the technical readiness level of this technology and we compare our findings to models and other experimental methods of emissivity determination.

  3. Sensitivity studies for a space-based methane lidar mission

    NASA Astrophysics Data System (ADS)

    Kiemle, C.; Quatrevalet, M.; Ehret, G.; Amediek, A.; Fix, A.; Wirth, M.

    2011-10-01

    Methane is the third most important greenhouse gas in the atmosphere after water vapour and carbon dioxide. A major handicap to quantify the emissions at the Earth's surface in order to better understand biosphere-atmosphere exchange processes and potential climate feedbacks is the lack of accurate and global observations of methane. Space-based integrated path differential absorption (IPDA) lidar has potential to fill this gap, and a Methane Remote Lidar Mission (MERLIN) on a small satellite in polar orbit was proposed by DLR and CNES in the frame of a German-French climate monitoring initiative. System simulations are used to identify key performance parameters and to find an advantageous instrument configuration, given the environmental, technological, and budget constraints. The sensitivity studies use representative averages of the atmospheric and surface state to estimate the measurement precision, i.e. the random uncertainty due to instrument noise. Key performance parameters for MERLIN are average laser power, telescope size, orbit height, surface reflectance, and detector noise. A modest-size lidar instrument with 0.45 W average laser power and 0.55 m telescope diameter on a 506 km orbit could provide 50-km averaged methane column measurement along the sub-satellite track with a precision of about 1% over vegetation. The use of a methane absorption trough at 1.65 μm improves the near-surface measurement sensitivity and vastly relaxes the wavelength stability requirement that was identified as one of the major technological risks in the pre-phase A studies for A-SCOPE, a space-based IPDA lidar for carbon dioxide at the European Space Agency. Minimal humidity and temperature sensitivity at this wavelength position will enable accurate measurements in tropical wetlands, key regions with largely uncertain methane emissions. In contrast to actual passive remote sensors, measurements in Polar Regions will be possible and biases due to aerosol layers and thin

  4. Sensitivity studies for a space-based methane lidar mission

    NASA Astrophysics Data System (ADS)

    Kiemle, C.; Quatrevalet, M.; Ehret, G.; Amediek, A.; Fix, A.; Wirth, M.

    2011-06-01

    Methane is the third most important greenhouse gas in the atmosphere after water vapour and carbon dioxide. A major handicap to quantify the emissions at the Earth's surface in order to better understand biosphere-atmosphere exchange processes and potential climate feedbacks is the lack of accurate and global observations of methane. Space-based integrated path differential absorption (IPDA) lidar has potential to fill this gap, and a Methane Remote Lidar Mission (MERLIN) on a small satellite in Polar orbit was proposed by DLR and CNES in the frame of a German-French climate monitoring initiative. System simulations are used to identify key performance parameters and to find an advantageous instrument configuration, given the environmental, technological, and budget constraints. The sensitivity studies use representative averages of the atmospheric and surface state to estimate the measurement precision, i.e. the random uncertainty due to instrument noise. Key performance parameters for MERLIN are average laser power, telescope size, orbit height, surface reflectance, and detector noise. A modest-size lidar instrument with 0.45 W average laser power and 0.55 m telescope diameter on a 506 km orbit could provide 50-km averaged methane column measurement along the sub-satellite track with a precision of about 1 % over vegetation. The use of a methane absorption trough at 1.65 μm improves the near-surface measurement sensitivity and vastly relaxes the wavelength stability requirement that was identified as one of the major technological risks in the pre-phase A studies for A-SCOPE, a space-based IPDA lidar for carbon dioxide at the European Space Agency. Minimal humidity and temperature sensitivity at this wavelength position will enable accurate measurements in tropical wetlands, key regions with largely uncertain methane emissions. In contrast to actual passive remote sensors, measurements in Polar Regions will be possible and biases due to aerosol layers and thin

  5. Two Stars Two Ways: Confirming a Microlensing Binary Lens Solution with a Spectroscopic Measurement of the Orbit

    NASA Astrophysics Data System (ADS)

    Yee, Jennifer C.; Johnson, John Asher; Skowron, Jan; Gould, Andrew; Pineda, J. Sebastian; Eastman, Jason; Vanderburg, Andrew; Howard, Andrew

    2016-04-01

    Light curves of microlensing events involving stellar binaries and planetary systems can provide information about the orbital elements of the system due to orbital modulations of the caustic structure. Accurately measuring the orbit in either the stellar or planetary case requires detailed modeling of subtle deviations in the light curve. At the same time, the natural, Cartesian parameterization of a microlensing binary is partially degenerate with the microlens parallax. Hence, it is desirable to perform independent tests of the predictions of microlens orbit models using radial velocity (RV) time series of the lens binary system. To this end, we present 3.5 years of RV monitoring of the binary lens system OGLE-2009-BLG-020 L, for which Skowron et al. constrained all internal parameters of the 200-700 day orbit. Our RV measurements reveal an orbit that is consistent with the predictions of the microlens light curve analysis, thereby providing the first confirmation of orbital elements inferred from microlensing events.

  6. ASTROMETRIC IMAGE CENTROID DISPLACEMENTS DUE TO GRAVITATIONAL MICROLENSING BY THE ELLIS WORMHOLE

    SciTech Connect

    Toki, Yukiharu; Kitamura, Takao; Asada, Hideki; Abe, Fumio

    2011-10-20

    Continuing work initiated in an earlier publication, we study the gravitational microlensing effects of the Ellis wormhole in the weak-field limit. First, we find a suitable coordinate transformation, such that the lens equation and analytic expressions of the lensed image positions can become much simpler. Second, we prove that two images always appear for the weak-field lens by the Ellis wormhole. By using these analytic results, we discuss astrometric image centroid displacements due to gravitational microlensing by the Ellis wormhole. The astrometric image centroid trajectory by the Ellis wormhole is different from the standard one by a spherical lensing object that is expressed by the Schwarzschild metric. The anomalous shift of the image centroid by the Ellis wormhole lens is smaller than that by the Schwarzschild lens, provided that the impact parameter and the Einstein ring radius are the same. Therefore, the lensed image centroid by the Ellis wormhole moves slower. Such a difference, although it is very small, will be, in principle, applicable for detecting or constraining the Ellis wormhole by using future high-precision astrometry observations. In particular, the image centroid position gives us additional information, so that the parameter degeneracy existing in photometric microlensing can be partially broken. The anomalous shift reaches the order of a few micro arcseconds, if our galaxy hosts a wormhole with throat radius larger than 10{sup 5} km. When the source moves tangentially to the Einstein ring, for instance, the maximum position shift of the image centroid by the Ellis wormhole is 0.18 normalized by the Einstein ring radius. For the same source trajectory, the maximum difference between the centroid displacement by the Ellis wormhole lens and that by the Schwarzschild one with the same Einstein ring radius is -0.16 in the units of the Einstein radius, where the negative means that the astrometric displacement by the Ellis wormhole lens is

  7. Another channel to detect close-in binary companions via gravitational microlensing

    NASA Astrophysics Data System (ADS)

    Chang, Heon-Young; Han, Cheongho

    2001-10-01

    Gaudi & Gould showed that close companions of remote binary systems can be efficiently detected by using gravitational microlensing via the deviations in the lensing light curves induced by the existence of the lens companions. In this paper, we introduce another channel to detect faint close-in binary companions by using microlensing. This method utilizes a caustic-crossing binary lens event with a source also composed of binary stars, where the companion is a faint star. Detection of the companion is possible because the flux of the companion can be highly amplified when it crosses the lens caustic. The detection is facilitated since the companion is more amplified than the primary because it, in general, has a smaller size than the primary, and thus experiences less finite source effect. The method is an extension of the previous one suggested to detect close-in giant planets by Graff & Gaudi and Lewis & Ibata and further developed by Ashton & Lewis. From the simulations of realistic Galactic bulge events, we find that companions of K-type main-sequence or brighter stars can be efficiently detected from the current type of microlensing follow-up observations by using the proposed method. We also find that compared with the method of detecting lens companions for which the efficiency drops significantly for binaries with separations <~0.2 of the angular Einstein ring radius, θE, the proposed method has an important advantage of being able to detect companions with substantially smaller separations down to ~(O)10-2θE.

  8. VizieR Online Data Catalog: Microlensing maps for a cusp configuration (Sluse+, 2013)

    NASA Astrophysics Data System (ADS)

    Sluse, D.; Kishimoto, M.; Anguita, T.; Wucknitz, O.; Wambsganss, J.

    2013-03-01

    The microlensing maps (see maps.dat) are generated with the inverse ray-shooting code developped by Prof. J. Wambsganss (Wambsganss 1990, PhD thesis). They are computed for a saddle-point image with (kappa,gamma)=(0.47,0.57) and for a minimum image with (kappa,gamma)=(0.42,0.50). Those values match those found for images A & B of the lensed AGN J1131-1231 (assuming a Singular Isothermal Ellipsoid+shear lens model). Each map has been computed for 3 different fraction of kappa_star (i.e. convergence in form of compact objects): 0.07, 0.30, 1.0. For each case, there is a high resolution map of 100eta0x100eta0 (eta0 = microlensing Einstein radius =3*10+16cm) and a low resolution map of 250eta0x250eta0. Source profiles (sources.dat) are calculated for the same two resolution (i.e. low/high). Three source brightness profiles are provided: a uniform disc, a ring-like uniform compact torus, a ring-like extended torus. The torus characteristics are described in Table 1 of the main paper. The source profile is calculated for 3 different luminosities (10+44.2, 10+45, 10+46erg/s/cm2) and rest-frame wavelengths (1.0, 2.2, 4.4um) as described in sources.dat. Source profiles which are larger that the microlensing maps are not calculated and are listed in nosources.dat. (4 data files).

  9. OGLE-III Microlensing Events and the Structure of the Galactic Bulge

    NASA Astrophysics Data System (ADS)

    Wyrzykowski, Łukasz; Rynkiewicz, Alicja E.; Skowron, Jan; Kozłowski, Szymon; Udalski, Andrzej; Szymański, Michał K.; Kubiak, Marcin; Soszyński, Igor; Pietrzyński, Grzegorz; Poleski, Radosław; Pietrukowicz, Paweł; Pawlak, Michał

    2015-01-01

    We present and study the largest and most comprehensive catalog of microlensing events ever constructed. The sample of standard microlensing events comprises 3718 unique events from 2001-2009 with 1409 events that had not been detected before in real-time by the Early Warning System of the Optical Gravitational Lensing Experiment. The search pipeline uses machine learning algorithms to help find rare phenomena among 150 million objects and to derive the detection efficiency. Applications of the catalog can be numerous, from analyzing individual events to large statistical studies of the Galactic mass, kinematics distributions, and planetary abundances. We derive maps of the mean Einstein ring crossing time of events spanning 31 deg2 toward the Galactic center and compare the observed distributions with the most recent models. We find good agreement within the observed region and we see the signature of the tilt of the bar in the microlensing data. However, the asymmetry of the mean timescales seems to rise more steeply than predicted, indicating either a somewhat different orientation of the bar or a larger bar width. The map of events with sources in the Galactic bulge shows a dependence of the mean timescale on the Galactic latitude, signaling an increasing contribution from disk lenses closer to the plane relative to the height of the disk. Our data present a perfect set for comparing and enhancing new models of the central parts of the Milky Way and creating a three-dimensional picture of the Galaxy. Based on observations obtained with the 1.3 m Warsaw telescope at the Las Campanas Observatory of the Carnegie Institution for Science.

  10. Single Crystal DMs for Space-Based Observatories

    NASA Astrophysics Data System (ADS)

    Bierden, Paul

    We propose to demonstrate the feasibility of a new manufacturing process for large aperture, high-actuator count microelectromechanical deformable mirrors (MEMS-DMs). These DMs are designed to fill a critical technology gap in NASA s plan for high- contrast space-based exoplanet observatories. We will manufacture a prototype DM with a continuous mirror facesheet, having an active aperture of 50mm diameter, supported by 2040 electrostatic actuators (50 across the diameter of the active aperture), spaced at a pitch of 1mm. The DM will be manufactured using silicon microfabrication tools. The strategic motivation for the proposed project is to advance MEMS DMs as an enabling technology in NASA s rapidly emerging program for extrasolar planet exploration. That goal is supported by an Astro2010 white paper on Technologies for Direct Optical Imaging of Exoplanets, which concluded that DMs are a critical component for all proposed internal coronagraph instrument concepts. That white paper pointed to great strides made by DM developers in the past decade, and acknowledged the components made by Boston Micromachines Corporation to be the most notable MEMS-based technology option. The principal manufacturing innovation in this project will be assembly of the DM through fusion bonding of three separate single crystal silicon wafers comprising the device s substrate, actuator array, and facesheet. The most significant challenge of this project will be to develop processes that allow reliable fusion bonds between multiple compliant silicon layers while yielding an optically flat surface and a robust electromechanical system. The compliance of the DM, which is required for its electromechanical function, will make it challenging to achieve the intimate, planar contact that is generally needed for success in fusion bonding. The manufacturing approach will use photolithography and reactive ion etching to pattern structural layers. Three wafer-scale devices will be patterned and

  11. Design, fabrication, and characterization of thermoplastic microlenses for fiber-optic probe imaging.

    PubMed

    Shinoj, V K; Murukeshan, V M; Tor, S B; Loh, N H; Lye, S W

    2014-02-20

    Microlens-ended fibers could find great usefulness in future biomedical applications, particularly in endoscopic imaging applications. In this context, this paper focuses on microlens-attached specialty optical fibers such as imaging fiber that can be used for probe imaging applications. Stand-alone self-aligned polymer microlenses have been fabricated by microcompression molding. The fabrication parameters have been optimized for different materials, such as poly(methyl methacrylate) (PMMA), polycarbonate (PC Lexan 123R), Zeonor 1060R (ZNR), and Topas COC. A comparison study of the focusing and spatial resolution of the fabricated lenses is performed prior to employing them for fiber-optic fluorescence imaging applications. PMID:24663305

  12. Strong chromatic microlensing in HE0047–1756 and SDSS1155+6346

    SciTech Connect

    Rojas, K.; Motta, V.; Mediavilla, E.; Jiménez-Vicente, J.; Muñoz, J. A. E-mail: veronica.motta@uv.cl E-mail: falco@cfa.harvard.edu E-mail: jmunoz@uv.es

    2014-12-10

    We use spectra of the double-lensed quasars HE0047–1756 and SDSS1155+6346 to study their unresolved structure through the impact of microlensing. There is no significant evidence of microlensing in the emission line profiles except for the Lyα line of SDSS1155+6346, which shows strong differences in the shapes for images A and B. However, the continuum of the B image spectrum in SDSS1155+6346 is strongly contaminated by the lens galaxy, and these differences should be considered with caution. Using the flux ratios of the emission lines for image pairs as a baseline to remove macro-magnification and extinction, we have detected strong chromatic microlensing in the continuum measured by CASTLES (www.cfa.harvard.edu/castles/) in both lens systems, with amplitudes 0.09(λ16000) ≲ |Δm| ≲ 0.8(λ5439) for HE0047–1756, and 0.2(λ16000) ≲ |Δm| ≲ 0.8(λ5439) for SDSS1155+6346. Using magnification maps to simulate microlensing and modeling the accretion disk as a Gaussian source (I ∝ exp(–R {sup 2}/2r {sub s}{sup 2})) of size r {sub s} ∝ λ {sup p}, we find r {sub s} = 2.5{sub −1.4}{sup +3.0} √(M/0.3M{sub ⊙}) lt-day and p = 2.3 ± 0.8 at the rest frame for λ = 2045 for HE0047–1756 (log prior) and r {sub s} = 5.5{sub −3.3}{sup +8.2} √(M/0.3M{sub ⊙}) lt-day and p = 1.5 ± 0.6 at the rest frame of λ = 1398 for SDSS1155+6346 (log prior). Contrary to other studied lens systems, the chromaticity detected in HE0047–1756 and SDSS1155+6346 is large enough to fulfill the thin disk prediction. The inferred sizes, however, are very large compared to the predictions of this model, especially in the case of SDSS1155+6346.

  13. Strong Chromatic Microlensing in HE0047-1756 and SDSS1155+6346

    NASA Astrophysics Data System (ADS)

    Rojas, K.; Motta, V.; Mediavilla, E.; Falco, E.; Jiménez-Vicente, J.; Muñoz, J. A.

    2014-12-01

    We use spectra of the double-lensed quasars HE0047-1756 and SDSS1155+6346 to study their unresolved structure through the impact of microlensing. There is no significant evidence of microlensing in the emission line profiles except for the Lyα line of SDSS1155+6346, which shows strong differences in the shapes for images A and B. However, the continuum of the B image spectrum in SDSS1155+6346 is strongly contaminated by the lens galaxy, and these differences should be considered with caution. Using the flux ratios of the emission lines for image pairs as a baseline to remove macro-magnification and extinction, we have detected strong chromatic microlensing in the continuum measured by CASTLES (www.cfa.harvard.edu/castles/) in both lens systems, with amplitudes 0.09(λ16000) <~ |Δm| <~ 0.8(λ5439) for HE0047-1756, and 0.2(λ16000) <~ |Δm| <~ 0.8(λ5439) for SDSS1155+6346. Using magnification maps to simulate microlensing and modeling the accretion disk as a Gaussian source (I vprop exp(-R 2/2r ^2_s)) of size r s vprop λ p , we find r s = 2.5-1.4+3.0 \\sqrt{M/0.3M⊙ } lt-day and p = 2.3 ± 0.8 at the rest frame for λ = 2045 for HE0047-1756 (log prior) and r s = 5.5-3.3+8.2 \\sqrt{M/0.3M⊙ } lt-day and p = 1.5 ± 0.6 at the rest frame of λ = 1398 for SDSS1155+6346 (log prior). Contrary to other studied lens systems, the chromaticity detected in HE0047-1756 and SDSS1155+6346 is large enough to fulfill the thin disk prediction. The inferred sizes, however, are very large compared to the predictions of this model, especially in the case of SDSS1155+6346.

  14. Special relativity effects for space-based coherent lidar experiments

    NASA Technical Reports Server (NTRS)

    Raogudimetla, V. S.

    1994-01-01

    There is a great need to develop a system that can measure accurately atmospheric wind profiles because an accurate data of wind profiles in the atmosphere constitutes single most input for reliable simulations of global climate numerical methods. Also such data helps us understand atmospheric circulation and climate dynamics better. Because of this need for accurate wind measurements, a space-based Laser Atmospheric Winds Sounder (LAWS) is being designed at MSFC to measure wind profiles in the lower atmosphere of the earth with an accuracy of 1 m/s at lower altitudes to 5m/s at higher altitudes. This system uses an orbiting spacecraft with a pulsed laser source and measures the Doppler shift between the transmitted and received frequencies to estimate the atmospheric wind velocities. If a significant return from the ground (sea) is possible, the spacecraft speed and height are estimated from it and these results and the Doppler shift are then used to estimate the wind velocities in the atmosphere. It is expected that at the proposed wavelengths, there will be enough backscatter from the aerosols but there may no be significant return from the ground. So a coherent (heterodyne) detection system is being proposed for signal processing because it can provide high signal to noise ratio and sensitivity and thus make the best use of low ground return. However, for a heterodyne detection scheme to provide the best results, it is important that the receiving aperture be aligned properly for the proposed wind sounder, this amounts to only a few microradians tolerance in alignment. It is suspected that the satellite motion relative to the ground may introduce errors in the order of a few microradians because of special relativity. Hence, the problem of laser scattering off a moving fixed target when the source and receiver are moving, which was not treated in the past in the literature, was analyzed in the following, using relativistic electrodynamics and applied to the

  15. Orbits design for LEO space based solar power satellite system

    NASA Astrophysics Data System (ADS)

    Addanki, Neelima Krishna Murthy

    2011-12-01

    Space Based Solar Power satellites use solar arrays to generate clean, green, and renewable electricity in space and transmit it to earth via microwave, radiowave or laser beams to corresponding receivers (ground stations). These traditionally are large structures orbiting around earth at the geo-synchronous altitude. This thesis introduces a new architecture for a Space Based Solar Power satellite constellation. The proposed concept reduces the high cost involved in the construction of the space satellite and in the multiple launches to the geo-synchronous altitude. The proposed concept is a constellation of Low Earth Orbit satellites that are smaller in size than the conventional system. 7For this application a Repeated Sun-Synchronous Track Circular Orbit is considered (RSSTO). In these orbits, the spacecraft re-visits the same locations on earth periodically every given desired number of days with the line of nodes of the spacecraft's orbit fixed relative to the Sun. A wide range of solutions are studied, and, in this thesis, a two-orbit constellation design is chosen and simulated. The number of satellites is chosen based on the electric power demands in a given set of global cities. The orbits of the satellites are designed such that their ground tracks visit a maximum number of ground stations during the revisit period. In the simulation, the locations of the ground stations are chosen close to big cities, in USA and worldwide, so that the space power constellation beams down power directly to locations of high electric power demands. The j2 perturbations are included in the mathematical model used in orbit design. The Coverage time of each spacecraft over a ground site and the gap time between two consecutive spacecrafts visiting a ground site are simulated in order to evaluate the coverage continuity of the proposed solar power constellation. It has been observed from simulations that there always periods in which s spacecraft does not communicate with any

  16. Space-Based Thermal Infrared Studies of Asteroids

    NASA Astrophysics Data System (ADS)

    Mainzer, A.; Usui, F.; Trilling, D. E.

    Large-area surveys operating at mid-infrared wavelengths have proven to be a valuable means of discovering and characterizing minor planets. Through the use of radiometric models, it is possible to derive physical properties such as diameters, albedos, and thermal inertia for large numbers of objects. Modern detector array technology has resulted in a significant improvement in spatial resolution and sensitivity compared with previous generations of spacebased infrared telescopes, giving rise to a commensurate increase in the number of objects that have been observed at these wavelengths. Spacebased infrared surveys of asteroids therefore offer an effective method of rapidly gathering information about the orbital and physical properties of small-body populations. The AKARI, Wide-field Infrared Survey Explorer (WISE)/ Near- Earth Object Wide-field Infrared Survey Explorer (NEOWISE), Spitzer Space Telescope, and Herschel Space Observatory missions have significantly increased the number of minor planets with well-determined diameters and albedos.

  17. Utilization of commercial communications systems for space based research applications

    NASA Astrophysics Data System (ADS)

    Overmyer, Carolyn; Thompson, Clark

    1998-01-01

    With the increase in utilization of space for research and development activities, the need for a communication system which improves the availability of payload uplink and downlink with the ground becomes increasingly more critical. At the same time, experiment developers are experiencing a tightening of their budgets for space based research. They don't have the capability to develop a unique communication interface that requires unique software and hardware packages. They would prefer to use commercial protocols and standards available through off-the-shelf components. Also, the need for secure communication is critical to keep proprietary data from being distributed to competing organizations. In order to meet the user community needs, SPACEHAB is currently in the process of developing and testing a system designed specifically for the user community called the SPACEHAB Universal Communication System (SHUCS). The purpose of this paper is to present customer requirements, the SHUCS design approach and top level operations, terrestrial test results, and flight testing scheduled for STS-91 and -95.

  18. Space-based laser-driven MHD generator: Feasibility study

    NASA Technical Reports Server (NTRS)

    Choi, S. H.

    1986-01-01

    The feasibility of a laser-driven MHD generator, as a candidate receiver for a space-based laser power transmission system, was investigated. On the basis of reasonable parameters obtained in the literature, a model of the laser-driven MHD generator was developed with the assumptions of a steady, turbulent, two-dimensional flow. These assumptions were based on the continuous and steady generation of plasmas by the exposure of the continuous wave laser beam thus inducing a steady back pressure that enables the medium to flow steadily. The model considered here took the turbulent nature of plasmas into account in the two-dimensional geometry of the generator. For these conditions with the plasma parameters defining the thermal conductivity, viscosity, electrical conductivity for the plasma flow, a generator efficiency of 53.3% was calculated. If turbulent effects and nonequilibrium ionization are taken into account, the efficiency is 43.2%. The study shows that the laser-driven MHD system has potential as a laser power receiver for space applications because of its high energy conversion efficiency, high energy density and relatively simple mechanism as compared to other energy conversion cycles.

  19. UV lifetime laser demonstrator for space-based applications

    NASA Astrophysics Data System (ADS)

    Albert, Michael; Puffenburger, Kent; Schum, Tom; Fitzpatrick, Fran; Litvinovitch, Slava; Jones, Darrell; Rudd, Joseph; Hovis, Floyd

    2015-09-01

    A long-lived UV laser is an enabling technology for a number of high-priority, space-based lidar instruments. These include next generation cloud and aerosol lidars that incorporates a UV channel, direct detection 3-D wind lidars, and ozone DIAL (differential absorption lidar) system. In previous SBIR funded work we developed techniques for increasing the survivability of components in high power UV lasers and demonstrated improved operational lifetimes. In this Phase III ESTO funded effort we are designing and building a TRL (Technology Readiness Level) 6 demonstrator that will have increased output power and a space-qualifiable package that is mechanically robust and thermally-stable. For full space compatibility, thermal control will be through pure conductive cooling. Contamination control processes and optical coatings will be chosen that are compatible with lifetimes in excess of 1 billion shots. The 1064nm output will be frequency tripled to provide greater than 100mJ pulses of 355nm light at 150 Hz. After completing the laser module build in the third quarter of 2015 we will initiate lifetime testing, followed by thermal/vacuum (TVAC) and vibration testing to demonstrate that the design is at TRL 6.

  20. Beamed Energy and the Economics of Space Based Solar Power

    NASA Astrophysics Data System (ADS)

    Keith Henson, H.

    2010-05-01

    For space based solar power to replace fossil fuel, it must sell for 1-2 cents per kWh. To reach this sales price requires a launch cost to GEO of ˜100/kg. Proposed to reach this cost figure at 100 tonne/hour are two stages to GEO where a Skylon-rocket-plane first stage provides five km/sec and a laser stage provides 6.64 km/sec. The combination appears to reduce the cost to GEO to under 100/kg at a materials flow rate of ˜1 million tonnes per year, enough to initially construct 200 GW per year of power satellites. An extended Pro Forma business case indicates that peak investment to profitability might be ˜65 B. Over a 25-year period, production rises to two TW per year to undercut and replace most other sources of energy. Energy on this scale solves other supply problems such as water and liquid fuels. It could even allow removal of CO2 from the air and storage of carbon as synthetic oil in empty oil fields.

  1. Space-based solar power conversion and delivery systems study

    NASA Technical Reports Server (NTRS)

    1976-01-01

    Even at reduced rates of growth, the demand for electric power is expected to more than triple between now and 1995, and to triple again over the period 1995-2020. Without the development of new power sources and advanced transmission technologies, it may not be possible to supply electric energy at prices that are conductive to generalized economic welfare. Solar power is renewable and its conversion and transmission from space may be advantageous. The goal of this study is to assess the economic merit of space-based photovoltaic systems for power generation and a power relay satellite for power transmission. In this study, satellite solar power generation and transmission systems, as represented by current configurations of the Satellite Solar Station (SSPS) and the Power Relay Satellite (PRS), are compared with current and future terrestrial power generation and transmission systems to determine their technical and economic suitability for meeting power demands in the period of 1990 and beyond while meeting ever-increasing environmental and social constraints.

  2. A space-based radio frequency transient event classifier

    SciTech Connect

    Moore, K.R.; Blain, C.P.; Caffrey, M.P.; Franz, R.C.; Henneke, K.M.; Jones, R.G.

    1998-03-01

    The Department of Energy is currently investigating economical and reliable techniques for space-based nuclear weapon treaty verification. Nuclear weapon detonations produce RF transients that are signatures of illegal nuclear weapons tests. However, there are many other sources of RF signals, both natural and man-made. Direct digitization of RF signals requires rates of 300 MSamples per second and produces 10{sup 13} samples per day of data to analyze. it is impractical to store and downlink all digitized RF data from such a satellite without a prohibitively expensive increase in the number and capacities of ground stations. Reliable and robust data processing and information extraction must be performed onboard the spacecraft in order to reduce downlinked data to a reasonable volume. The FORTE (Fast On-Orbit Recording of Transient Events) satellite records RF transients in space. These transients will be classified onboard the spacecraft with an Event Classifier specialized hardware that performs signal preprocessing and neural network classification. The authors describe the Event Classifier requirements, scientific constraints, design and implementation.

  3. Space-Based Chemical Lasers in strategic defense

    SciTech Connect

    Wildt, D. )

    1992-07-01

    The Strategic Defense Initiative Organization (SDIO) has made significant progress in developing Space-Based chemical Laser (SBL) technologies and in studying the SBLs global defense capability. In this mission, a constellation of several orbiting laser platforms provides continuous global defense by intercepting threatening missiles in their boost phase, including short range ballistic missiles (SRBMs). An optional smaller constellation provides defense against launches from the low and midlatitude regions. In addition, SBLs have utility in other important related missions such as surveillance, air defense and discrimination. The hardware necessary to build such a system has been developed to the point where it is mature and ready for demonstration in space. Advances have been made in each of the following major areas of the SBL: laser device; optics/beam control; beam pointing; ATP (acquisition, tracking and pointing); uncooled optics; and laser lethality. Integration of the key laser and beam control technologies is now occurring in the ground-based ALI experiment, and a space demonstration experiment, Star LITE, is in the planning and concept development phase.

  4. Planet Diversity Yields with Space-based Direct Imaging Telescopes

    NASA Astrophysics Data System (ADS)

    Domagal-Goldman, Shawn; Kopparapu, Ravi Kumar; Hébrard, Eric; Stark, Chris; Robinson, Tyler D.; Roberge, Aki; Mandell, Avi; McElwain, Michael W.; Clampin, Mark; Meadows, Victoria; Arney, Giada; Advanced Technology Large Aperture Space Telescope Science Team, Exoplanet Climate Group

    2016-01-01

    In this presentation, we will estimate the yield for a diversity of planets from future space-based flagship telescopes. We first divvy up planets into categories that are based on current observables, and that should impact the spectra we hope to observe in the future. The two main classification parameters we use here are the size of a planet and the energy flux into the planet's atmosphere. These two parameters are measureable or inferable from present-day observations, and should have a strong influence on future spectroscopy observations from JWST, WFIRST (with a coronagraph and/or starshade), and concept flagship missions that would fly some time after WFIRST. This allows us to calculate "ηplanet" values for each kind of planet. These η values then allow calculations of the expected yields from direct imaging missions, by leveraging the models and prior work by Stark and colleagues (2014, 2015). That work estimated the yields for potentially Earth-like worlds (i.e. of a size and stellar irradiation consistent with definitions of the habitable zone) for telescopes with a variety of observational parameters. We will do the same thing here, but for a wider variety of planets. This will allow us to discuss the implications of architecture and instrument properties on the diversity of worlds that future direct imaging missions would observe.

  5. Possible Space-Based Gravitational-Wave Observatory Mission Concept

    NASA Technical Reports Server (NTRS)

    Livas, Jeffrey C.

    2015-01-01

    The existence of gravitational waves was established by the discovery of the Binary Pulsar PSR 1913+16 by Hulse and Taylor in 1974, for which they were awarded the 1983 Nobel Prize. However, it is the exploitation of these gravitational waves for the extraction of the astrophysical parameters of the sources that will open the first new astronomical window since the development of gamma ray telescopes in the 1970's and enable a new era of discovery and understanding of the Universe. Direct detection is expected in at least two frequency bands from the ground before the end of the decade with Advanced LIGO and Pulsar Timing Arrays. However, many of the most exciting sources will be continuously observable in the band from 0.1-100 mHz, accessible only from space due to seismic noise and gravity gradients in that band that disturb ground-based observatories. This poster will discuss a possible mission concept, Space-based Gravitational-wave Observatory (SGO-Mid) developed from the original Laser Interferometer Space Antenna (LISA) reference mission but updated to reduce risk and cost.

  6. Space-based observation of the extensive airshowers

    NASA Astrophysics Data System (ADS)

    Ebisuzaki, T.

    2013-06-01

    Space based observations of extensive air showers constitute the next experimental challenge for the study of the universe at extreme energy. Space observation will allow a "quantum jump" in the observational area available to detect the UV light tracks produced by particles with energies higher than 1020 eV. These are thought to reach the Earth almost undeflected by the cosmic magnetic field. This new technique will contribute to establish the new field of astronomy and astrophysics performed with charged particles and neutrinos at the highest energies. This idea was created by the incredible efforts of three outstanding comic ray physicists: John Linsley, Livio Scarsi, and Yoshiyuki Takahashi. This challenging technique has four significant merits in comparison with ground-based observations: 1) Very large observational area, 2) Well constrained distances of the showers, 3) Clear and stable atmospheric transmission in the above half troposphere, 4) Uniform Exposure across both the north and south skies. Four proposed and planned missions constitute the roadmap of the community: TUS, JEM-EUSO, KLPVE, and Super-EUSO will contribute step-by-step to establish this challenging field of research.

  7. Estimating moisture transport over oceans using space-based observations

    NASA Technical Reports Server (NTRS)

    Liu, W. Timothy; Wenqing, Tang

    2005-01-01

    The moisture transport integrated over the depth of the atmosphere (0) is estimated over oceans using satellite data. The transport is the product of the precipitable water and an equivalent velocity (ue), which, by definition, is the depth-averaged wind velocity weighted by humidity. An artificial neural network is employed to construct a relation between the surface wind velocity measured by the spaceborne scatterometer and coincident ue derived using humidity and wind profiles measured by rawinsondes and produced by reanalysis of operational numerical weather prediction (NWP). On the basis of this relation, 0 fields are produced over global tropical and subtropical oceans (40_N- 40_S) at 0.25_ latitude-longitude and twice daily resolutions from August 1999 to December 2003 using surface wind vector from QuikSCAT and precipitable water from the Tropical Rain Measuring Mission. The derived ue were found to capture the major temporal variability when compared with radiosonde measurements. The average error over global oceans, when compared with NWP data, was comparable with the instrument accuracy specification of space-based scatterometers. The global distribution exhibits the known characteristics of, and reveals more detailed variability than in, previous data.

  8. Architectures for a Space-based Gravitational-Wave Observatory

    NASA Astrophysics Data System (ADS)

    Stebbins, Robin

    2015-04-01

    The European Space Agency (ESA) selected the science theme, the ``Gravitational Universe,'' for the third large mission opportunity, known as L3, under its Cosmic Vision Programme. The planned launch date is 2034. ESA is considering a 20% participation by an international partner, and NASA's Astrophysics Division has begun negotiating a NASA role. We have studied the design consequences of a NASA contribution, evaluated the science benefits and identified the technology requirements for hardware that could be delivered by NASA. The European community proposed a strawman mission concept, called eLISA, having two measurement arms, derived from the well studied LISA (Laser Interferometer Space Antenna) concept. The US community is promoting a mission concept known as SGO Mid (Space-based Gravitational-wave Observatory Mid-sized), a three arm LISA-like concept. If NASA were to partner with ESA, the eLISA concept could be transformed to SGO Mid by the addition of a third arm, thereby augmenting science, reducing risk and reducing non-recurring engineering costs. The characteristics of the mission concepts and the relative science performance of eLISA, SGO Mid and LISA are described.

  9. CHEMICAL COMPOSITION OF FAINT (I approx 21 mag) MICROLENSED BULGE DWARF OGLE-2007-BLG-514S

    SciTech Connect

    Epstein, Courtney R.; Johnson, Jennifer A.; Dong, Subo; Gould, Andrew; Udalski, Andrzej; Becker, George E-mail: jaj@astronomy.ohio-state.ed E-mail: dong@ias.ed E-mail: gdb@ast.cam.ac.u

    2010-01-20

    We present a high-resolution spectrum of a microlensed G dwarf in the Galactic bulge with spectroscopic temperature T{sub eff} = 5600 +- 180 K. This I approx 21 mag star was magnified by a factor ranging from 1160 to 1300 at the time of observation. Its high metallicity ([Fe/H] = 0.33 +- 0.15 dex) places this star at the upper end of the bulge giant metallicity distribution. Using a Kolmogorov-Smirnov test, we find a 1.6% probability that the published microlensed bulge dwarfs share an underlying distribution with bulge giants, properly accounting for a radial bulge metallicity gradient. We obtain abundance measurements for 15 elements and perform a rigorous error analysis that includes covariances between parameters. This star, like bulge giants with the same metallicity, shows no alpha enhancement. It confirms the chemical abundance trends observed in previously analyzed bulge dwarfs. At supersolar metallicities, we observe a discrepancy between bulge giant and bulge dwarf Na abundances.

  10. Microlensed dual-fiber probe for depth-resolved fluorescence measurements

    NASA Astrophysics Data System (ADS)

    Choi, Hae Young; Ryu, Seon Young; Kim, Jae Young; Kim, Geon Hee; Park, Seong Jun; Lee, Byeong Ha; Chang, Ki Soo

    2011-07-01

    We propose and demonstrate a compact microlensed dual-fiber probe that has a good collection efficiency and a high depth-resolution ability for fluorescence measurements. The probe is formed with a conventional fusion splicer creating a common focusing lens on two fibers placed side by side. The collection efficiency of the fabricated probe was evaluated by measuring the fluorescence signal of a fresh ginkgo leaf. It was shown experimentally that the proposed probe could effectively collect the fluorescence signal with a six-fold increase compared to that of a general flat-tipped probe. The beam propagation method was used to design a probe with an optimized working distance and an improved resolving depth. It was found that the working distance depends mainly on the radius of curvature of the lens, whereas the resolving depth is determined by the core diameters of the illumination and collection fibers. The depth-resolved ability of probes with working distances of ~100 μm and 300 μm was validated by using a two-layer tissue phantom. The experimental results demonstrate that the microlensed dual-fiber probe has the potential to facilitate depth-resolved fluorescence detection of epithelial tissue.

  11. DARK MATTER MASS FRACTION IN LENS GALAXIES: NEW ESTIMATES FROM MICROLENSING

    SciTech Connect

    Jiménez-Vicente, J.; Mediavilla, E.; Muñoz, J. A.

    2015-02-01

    We present a joint estimate of the stellar/dark matter mass fraction in lens galaxies and the average size of the accretion disk of lensed quasars based on microlensing measurements of 27 quasar image pairs seen through 19 lens galaxies. The Bayesian estimate for the fraction of the surface mass density in the form of stars is α = 0.21 ± 0.14 near the Einstein radius of the lenses (∼1-2 effective radii). The estimate for the average accretion disk size is R{sub 1/2}=7.9{sub −2.6}{sup +3.8}√(M/0.3 M{sub ⊙}) light days. The fraction of mass in stars at these radii is significantly larger than previous estimates from microlensing studies assuming quasars were point-like. The corresponding local dark matter fraction of 79% is in good agreement with other estimates based on strong lensing or kinematics. The size of the accretion disk inferred in the present study is slightly larger than previous estimates.

  12. Searching for intermediate-mass black holes in globular clusters with gravitational microlensing

    NASA Astrophysics Data System (ADS)

    Kains, N.; Bramich, D. M.; Sahu, K. C.; Calamida, A.

    2016-08-01

    We discuss the potential of the gravitational microlensing method as a unique tool to detect unambiguous signals caused by intermediate-mass black holes in globular clusters. We select clusters near the line of sight to the Galactic bulge and the Small Magellanic Cloud, estimate the density of background stars for each of them, and carry out simulations in order to estimate the probabilities of detecting the astrometric signatures caused by black hole lensing. We find that for several clusters, the probability of detecting such an event is significant with available archival data from the Hubble Space Telescope. Specifically, we find that M 22 is the cluster with the best chances of yielding an intermediate-mass black hole (IMBH) detection via astrometric microlensing. If M 22 hosts an IMBH of mass 105 M⊙, then the probability that at least one star will yield a detectable signal over an observational baseline of 20 years is ˜86 per cent, while the probability of a null result is around 14 per cent. For an IMBH of mass 106 M⊙, the detection probability rises to >99 per cent. Future observing facilities will also extend the available time baseline, improving the chance of detections for the clusters we consider.

  13. MOA-2011-BLG-028Lb: A Neptune-mass Microlensing Planet in the Galactic Bulge

    NASA Astrophysics Data System (ADS)

    Skowron, J.; Udalski, A.; Poleski, R.; Kozłowski, S.; Szymański, M. K.; Wyrzykowski, Ł.; Ulaczyk, K.; Pietrukowicz, P.; Pietrzyński, G.; Soszyński, I.; The OGLE Collaboration; Abe, F.; Bennett, D. P.; Bhattacharya, A.; Bond, I. A.; Freeman, M.; Fukui, A.; Hirao, Y.; Itow, Y.; Koshimoto, N.; Ling, C. H.; Masuda, K.; Matsubara, Y.; Muraki, Y.; Nagakane, M.; Ohnishi, K.; Rattenbury, N.; Saito, To.; Sullivan, D. J.; Sumi, T.; Suzuki, D.; Tristram, P. J.; Yonehara, A.; The MOA Collaboration; Dominik, M.; Jørgensen, U. G.; Bozza, V.; Harpsøe, K.; Hundertmark, M.; Skottfelt, J.; The MiNDSTEp Collaboration

    2016-03-01

    We present the discovery of a Neptune-mass planet orbiting a 0.8+/- 0.3{M}ȯ star in the Galactic bulge. The planet manifested itself during the microlensing event MOA-2011-BLG-028/OGLE-2011-BLG-0203 as a low-mass companion to the lens star. The analysis of the light curve provides the measurement of the mass ratio (1.2+/- 0.2)× {10}-4, which indicates that the mass of the planet is 12–60 Earth masses. The lensing system is located at 7.3 ± 0.7 kpc away from the Earth near the direction of Baade’s Window. The projected separation of the planet at the time of the microlensing event was 3.1–5.2 au. Although the microlens parallax effect is not detected in the light curve of this event, preventing the actual mass measurement, the uncertainties of mass and distance estimation are narrowed by the measurement of the source star proper motion on the OGLE-III images spanning eight years, and by the low amount of blended light seen, proving that the host star cannot be too bright and massive. We also discuss the inclusion of undetected parallax and orbital motion effects into the models and their influence onto the final physical parameters estimates. Based on observations obtained with the 1.3 m Warsaw telescope at the Las Campanas Observatory operated by the Carnegie Institution of Washington.

  14. X-ray microlensing in the quadruply lensed quasar Q2237+0305

    NASA Astrophysics Data System (ADS)

    Zimmer, F.; Schmidt, R. W.; Wambsganss, J.

    2011-05-01

    We use archival data of NASA's Chandra X-ray telescope to compile an X-ray light curve of all four images of the quadruply lensed quasar Q2237+0305 (zQ= 1.695) from 2006 January to 2007 January. We fit simulated point spread functions to the four individual quasar images using Cash's C-statistic to account for the Poissonian nature of the X-ray signal. The quasar images display strong flux variations up to a factor of ˜4 within one month. We can disentangle the intrinsic quasar variability from flux variations due to gravitational microlensing by looking at the flux ratios of the individual quasar images. Doing this, we find evidence for microlensing in image A. In particular, the time sequence of the flux ratio A/B in the X-ray regime correlates with the corresponding sequence in the optical monitoring by OGLE in the V band. The amplitudes in the X-ray light curve are larger. For the most prominent peak, the increase of the X-ray ratio A/B is larger by a factor of ˜1.6 compared to the signal in the optical. In agreement with theory and other observations of multiply-imaged quasars, this suggests that the X-ray emission region of this quasar is significantly smaller than the optical emission region.

  15. New aperture photometry of QSO 0957+561; application to time delay and microlensing

    NASA Astrophysics Data System (ADS)

    Ovaldsen, J. E.; Teuber, J.; Schild, R. E.; Stabell, R.

    2003-05-01

    We present a re-reduction of archival CCD frames of the doubly imaged quasar 0957+561 using a new photometry code. Aperture photometry with corrections for both cross contamination between the quasar images and galaxy contamination is performed on about 2650 R-band images from a five year period (1992-1997). From the brightness data a time delay of 424.9 +/- 1.2 days is derived using two different statistical techniques. The amount of gravitational microlensing in the quasar light curves is briefly investigated, and we find unambiguous evidence of both long term and short term microlensing. We also note the unusual circumstance regarding time delay estimates for this gravitational lens. Estimates by different observers from different data sets or even with the same data sets give lag estimates differing by typically 8 days, and error bars of only a day or two. This probably indicates several complexities where the result of each estimate depends upon the details of the calculation.

  16. Microlensing towards the LMC revisited by adopting a non-Gaussian velocity distribution for the sources

    NASA Astrophysics Data System (ADS)

    Mancini, L.

    2009-03-01

    Aims: We discuss whether the Gaussian is a reasonable approximation of the velocity distribution of stellar systems that are not spherically distributed. Methods: By using a non-Gaussian velocity distribution to describe the sources in the Large Magellanic Cloud (LMC), we reinvestigate the expected microlensing parameters of a lens population isotropically distributed either in the Milky Way halo or in the LMC (self lensing). We compare our estimates with the experimental results of the MACHO collaboration. Results: An interesting result that emerges from our analysis is that, moving from the Gaussian to the non-Gaussian case, we do not observe any change in the form of the distribution curves describing the rate of microlensing events for lenses in the Galactic halo. The corresponding expected timescales and number of expected events also do not vary. Conversely, with respect to the self-lensing case, we observe a moderate increase in the rate and number of expected events. We conclude that the error in the estimate of the most likely value for the MACHO mass and the Galactic halo fraction in form of MACHOs, calculated with a Gaussian velocity distribution for the LMC sources, is not higher than 2%.

  17. MACHO project 2nd year LMC microlensing results and dark matter implications

    SciTech Connect

    Alcock, C.; Allsman, R.A.; Alves, D.

    1996-02-01

    The MACHO Project is searching for galactic dark matter in the form of massive compact halo objects (Machos). Millions of stars in the Large Magellanic Cloud (LMC), Small Magellanic Cloud (SMC), and Galactic bulge are photometrically monitored in an attempt to detect rare gravitational microlensing events caused by otherwise invisible Machos. Analysis of two years of photometry on 8.5 million stars in the LMC reveals 8 candidate microlensing events, far more than the one event expected from lensing by low-mass stars in known galactic populations. Five these eight events we estimate the optical depth towards the LMC from events with 2 < i < 200 days to be r2 280 about 2.9+1 4/-0.8 X 10-7. This exceeds the optical depth of 0.5 x 10-7 expected for known stars and is to be compared with an optical depth of 4.7 X 10-7 predicted for a `standard` halo composed entirely of Machos. The total mass in this lensing population is 2 +1.2/-0.7 x 10+11 Mo (within 50 kpc from the Galactic center). Event timescales yield a most probable Macho Mass of 0.5 +0.3/-0.2 Mo, although this value is quite model dependent. -0.2

  18. OGLE-2014-BLG-0257L: A Microlensing Brown Dwarf Orbiting a Low-mass M Dwarf

    NASA Astrophysics Data System (ADS)

    Han, C.; Jung, Y. K.; Udalski, A.; Gould, A.; Bozza, V.; Szymański, M. K.; Soszyński, I.; Poleski, R.; Kozłowski, S.; Pietrukowicz, P.; Skowron, J.; Ulaczyk, K.; Wyrzykowski, Ł.; OGLE Collaboration

    2016-05-01

    In this paper, we report the discovery of a binary composed of a brown dwarf (BD) and a low-mass M dwarf from observation of the microlensing event OGLE-2014-BLG-0257. The resolution of the very brief caustic crossing combined with the detection of subtle continuous deviation in the lensing light curve induced by the Earth’s orbital motion enable us to precisely measure both the Einstein radius {θ }{{E}} and the lens parallax {π }{{E}}, which are the two quantities needed to unambiguously determine the mass and distance to the lens. It is found that the companion is a substellar BD with a mass of 0.036+/- 0.005 {M}ȯ (37.7+/- 5.2 {M}{{J}}) and it is orbiting an M dwarf with a mass of 0.19+/- 0.02 {M}ȯ . The binary is located at a distance of 1.25 ± 0.13 kpc toward the Galactic bulge and the projected separation between the binary components is 0.61 ± 0.07 au. The separation scaled by the mass of the host is 3.2 {{au}}/{M}ȯ . Based on the assumption that separations scale with masses, the discovered BD is located in the BD desert. With the growing sample of BDs in various environments, microlensing will provide a powerful probe of BDs in the Galaxy.

  19. Interpretation of a short-term anomaly in the gravitational microlensing event MOA-2012-BLG-486

    SciTech Connect

    Hwang, K.-H.; Choi, J.-Y.; Han, C.; Bond, I. A.; Sumi, T.; Koshimoto, N.; Gaudi, B. S.; Gould, A.; Bozza, V.; Beaulieu, J.-P.; Tsapras, Y.; Abe, F.; Fukunaga, D.; Itow, Y.; Bennett, D. P.; Botzler, C. S.; Freeman, M.; Chote, P.; Harris, P.; Fukui, A.; Collaboration: MOA Collaboration; μFUN Collaboration; PLANET Collaboration; RoboNet Collaboration; and others

    2013-11-20

    A planetary microlensing signal is generally characterized by a short-term perturbation to the standard single lensing light curve. A subset of binary-source events can produce perturbations that mimic planetary signals, thereby introducing an ambiguity between the planetary and binary-source interpretations. In this paper, we present the analysis of the microlensing event MOA-2012-BLG-486, for which the light curve exhibits a short-lived perturbation. Routine modeling not considering data taken in different passbands yields a best-fit planetary model that is slightly preferred over the best-fit binary-source model. However, when allowed for a change in the color during the perturbation, we find that the binary-source model yields a significantly better fit and thus the degeneracy is clearly resolved. This event not only signifies the importance of considering various interpretations of short-term anomalies, but also demonstrates the importance of multi-band data for checking the possibility of false-positive planetary signals.

  20. Microlenses focal length measurement using Z-scan and parallel moiré deflectometry

    NASA Astrophysics Data System (ADS)

    Rasouli, Saifollah; Rajabi, Y.; Sarabi, H.

    2013-12-01

    In this paper, a simple and accurate method based on Z-scan and parallel moiré deflectometry for measuring the focal length of microlenses is reported. A laser beam is focused by one lens and is re-collimated by another lens, and then strikes a parallel moiré deflectometer. In the presence of a microlens near the focal point of the first lens, the radius of curvature of the beam is changed; the parallel moiré fringes are formed only due to the beam divergence or convergence. The focal length of the microlens is obtained from the moiré fringe period graph without the need to know the position of the principal planes. This method is simple, more reliable, and completely automated. The implementation of the method is straightforward. Since a focused laser beam and Z-scan in free space are used, it can be employed for determining small focal lengths of small size microlenses without serious limitation on their size.

  1. New Microlensing Constraints of Primordial Black Hole Dark Matter based on First Two Years of Kepler Data

    NASA Astrophysics Data System (ADS)

    Cieplak, Agnieszka; Griest, K.; Lehner, M.

    2014-01-01

    Primordial Black Holes (PBHs) remain one of the few Dark Matter (DM) candidates left within the Standard Model of Particle Physics. We have previously found that previous PBH DM limits could theoretically be extended by two orders of magnitude by using the microlensing of the source stars monitored by the Kepler satellite due to its photometric precision and the large projected cross section of the nearby stars. Here we present the experimental results of our study of the first two years of Kepler stellar lightcurves. After eliminating background events such as variable stars, flares, and comets, we have found no microlensing events. We were therefore able to calculate our efficiency of detection by introducing millions of fake microlensing events which included limb-darkening and a corrected finite-source microlensing formalism. By performing this Monte Carlo analysis, we have found that PBHs with masses between 2 × 10-9 M⊙ and 10-7 M⊙ cannot constitute the entirety of the DM, thereby constraining a full order of magnitude of the previously allowed PBH DM mass range.

  2. Highly indistinguishable photons from deterministic quantum-dot microlenses utilizing three-dimensional in situ electron-beam lithography

    PubMed Central

    Gschrey, M.; Thoma, A.; Schnauber, P.; Seifried, M.; Schmidt, R.; Wohlfeil, B.; Krüger, L.; Schulze, J. -H.; Heindel, T.; Burger, S.; Schmidt, F.; Strittmatter, A.; Rodt, S.; Reitzenstein, S.

    2015-01-01

    The success of advanced quantum communication relies crucially on non-classical light sources emitting single indistinguishable photons at high flux rates and purity. We report on deterministically fabricated microlenses with single quantum dots inside which fulfil these requirements in a flexible and robust quantum device approach. In our concept we combine cathodoluminescence spectroscopy with advanced in situ three-dimensional electron-beam lithography at cryogenic temperatures to pattern monolithic microlenses precisely aligned to pre-selected single quantum dots above a distributed Bragg reflector. We demonstrate that the resulting deterministic quantum-dot microlenses enhance the photon-extraction efficiency to (23±3)%. Furthermore we prove that such microlenses assure close to pure emission of triggered single photons with a high degree of photon indistinguishability up to (80±7)% at saturation. As a unique feature, both single-photon purity and photon indistinguishability are preserved at high excitation power and pulsed excitation, even above saturation of the quantum emitter. PMID:26179766

  3. Highly indistinguishable photons from deterministic quantum-dot microlenses utilizing three-dimensional in situ electron-beam lithography.

    PubMed

    Gschrey, M; Thoma, A; Schnauber, P; Seifried, M; Schmidt, R; Wohlfeil, B; Krüger, L; Schulze, J-H; Heindel, T; Burger, S; Schmidt, F; Strittmatter, A; Rodt, S; Reitzenstein, S

    2015-01-01

    The success of advanced quantum communication relies crucially on non-classical light sources emitting single indistinguishable photons at high flux rates and purity. We report on deterministically fabricated microlenses with single quantum dots inside which fulfil these requirements in a flexible and robust quantum device approach. In our concept we combine cathodoluminescence spectroscopy with advanced in situ three-dimensional electron-beam lithography at cryogenic temperatures to pattern monolithic microlenses precisely aligned to pre-selected single quantum dots above a distributed Bragg reflector. We demonstrate that the resulting deterministic quantum-dot microlenses enhance the photon-extraction efficiency to (23±3)%. Furthermore we prove that such microlenses assure close to pure emission of triggered single photons with a high degree of photon indistinguishability up to (80±7)% at saturation. As a unique feature, both single-photon purity and photon indistinguishability are preserved at high excitation power and pulsed excitation, even above saturation of the quantum emitter. PMID:26179766

  4. Just in Time in Space or Space Based JIT

    NASA Technical Reports Server (NTRS)

    VanOrsdel, Kathleen G.

    1995-01-01

    Our satellite systems are mega-buck items. In today's cost conscious world, we need to reduce the overall costs of satellites if our space program is to survive. One way to accomplish this would be through on-orbit maintenance of parts on the orbiting craft. In order to accomplish maintenance at a low cost I advance the hypothesis of having parts and pieces (spares) waiting. Waiting in the sense of having something when you need it, or just-in-time. The JIT concept can actually be applied to space processes. Its definition has to be changed just enough to encompass the needs of space. Our space engineers tell us which parts and pieces the satellite systems might be needing once in orbit. These items are stored in space for the time of need and can be ready when they are needed -- or Space Based JIT. When a system has a problem, the repair facility is near by and through human or robotics intervention, it can be brought back into service. Through a JIT process, overall system costs could be reduced as standardization of parts is built into satellite systems to facilitate reduced numbers of parts being stored. Launch costs will be contained as fewer spare pieces need to be included in the launch vehicle and the space program will continue to thrive even in this era of reduced budgets. The concept of using an orbiting parts servicer and human or robotics maintenance/repair capabilities would extend satellite life-cycle and reduce system replacement launches. Reductions of this nature throughout the satellite program result in cost savings.

  5. Project SPARC: Space-Based Aeroassisted Reusable Craft

    NASA Technical Reports Server (NTRS)

    1990-01-01

    Future United States' space facilities include a Space Station in low Earth orbit (LEO) and a Geosynchronous Operations Support Center, or GeoShack, in geosynchronous orbit (GEO). One possible mode of transfer between the two orbits is an aerobraking vehicle. When traveling from GEO to LEO, the Earth's atmosphere can be used to aerodynamically reduce the velocity of the vehicle, which reduces the amount of propulsive change in velocity required for the mission. An aerobrake is added to the vehicle for this purpose, but the additional mass increases propellant requirements. This increase must not exceed the amount of propellant saved during the aeropass. The design and development of an aerobraking vehicle that will transfer crew and cargo between the Space Station and GeoShack is examined. The vehicle is referred to as Project SPARC, a SPace-based Aeroassisted Reusable Craft. SPARC consists of a removable 45 ft diameter aerobrake, two modified Pratt and Whitney Advanced Expander Engines with a liquid oxygen/liquid hydrogen propellant, a removable crew module with a maximum capacity of five, and standard sized payload bays providing a maximum payload capacity of 28,000 lbm. The aerobrake, a rigid, ellipsoidally blunted elliptical cone, provides lift at zero angle-of-attack due to a 73 deg rake angle, and is covered with a flexible multi-layer thermal protection system. Maximum dry mass of the vehicle without payload is 20,535 lbm, and the maximum propellant requirement is 79,753 lbm at an oxidizer to fuel ratio of 6/1. Key advantages of SPARC include its capability to meet mission changes, and its removable aerobrake and crew module.

  6. Cost of space-based laser ballistic missile defense.

    PubMed

    Field, G; Spergel, D

    1986-03-21

    Orbiting platforms carrying infrared lasers have been proposed as weapons forming the first tier of a ballistic missile defense system under the President's Strategic Defense Initiative. As each laser platform can destroy a limited number of missiles, one of several methods of countering such a system is to increase the number of offensive missiles. Hence it is important to know whether the cost-exchange ratio, defined as the ratio of the cost to the defense of destroying a missile to the cost to the offense of deploying an additional missile, is greater or less than 1. Although the technology to be used in a ballistic missile defense system is still extremely uncertain, it is useful to examine methods for calculating the cost-exchange ratio. As an example, the cost of an orbiting infrared laser ballistic missile defense system employed against intercontinental ballistic missiles launched simultaneously from a small area is compared to the cost of additional offensive missiles. If one adopts lower limits to the costs for the defense and upper limits to the costs for the offense, the cost-exchange ratio comes out substantially greater than 1. If these estimates are confirmed, such a ballistic missile defense system would be unable to maintain its effectiveness at less cost than it would take to proliferate the ballistic missiles necessary to overcome it and would therefore not satisfy the President's requirements for an effective strategic defense. Although the method is illustrated by applying it to a space-based infrared laser system, it should be straightforward to apply it to other proposed systems. PMID:17748077

  7. The proposal for new space-based gravitational experiments

    NASA Astrophysics Data System (ADS)

    Milyukov, Vadim; Sazhin, Mikhail; Zharov, Vladimir

    The development of space technologies opens new perspectives in solving the fundamental problems of gravity. We propose the experimental investigation of General Relativity (GR) in space experiments in following: a) measurement of post-Newtonian parameters (PPN), b) gravity wave detection in the low frequency band. The accuracy, with which GR is currently confirmed, is fractions of percent: 2.3× 10(-5) . However, in spite of the remarkable success of GR in the weak-field approximation, there are many reasons to consider alternative relativistic theories of gravity that predict the existence of effects other than GR, thus motivating new fundamental gravitational experiments. In this connection, the experimental measurements of PPN of parameters play a special role. To improve the accuracy of measurement of geodetic effects in the gravitational field of the Earth the clusters of spacecrafts, connected by microwave radio links and optical links, are widely used. Such a scheme allows to suppress effectively a coherent noise acting on the spacecraft, and to measure the distance between the satellites within a fraction of a millimeter. This technology was already tested for GRACE and GRAIL NASA missions. Furthermore, there are technologies allowing to effectively compensate non-gravitational noise to the level of 10(-10) - 10(-12) \\ m/s(2/sqrt{Hz}) . The project, which assume the lunch of cluster of the spacecrafts intended to study fundamental processes in the Universe, including the measurement of the PPN parameters and low frequency gravitational waves, is proposed in this report. We study the space-based systems in a configuration of few spacecrafts on different orbits in the gravitational field of the Earth for measuring these effects. Measurements of distances between spacecrafts are performed using microwave radio links, laser interferometry and ultra stable frequency standards. Developed modern technologies for distant measurements allow to reach the accuracy

  8. Validation Issues of a Space-based Methane Lidar

    NASA Astrophysics Data System (ADS)

    Kiemle, C.; Fix, A.; Ehret, G.; Flamant, P.

    2014-12-01

    Space-based lidar missions targeting greenhouse gases are expected to close observational gaps, e.g., over subarctic permafrost and tropical wetlands, where in-situ and passive remote sensing techniques have difficulties. In the frame of a joint climate monitoring initiative, a "Methane Remote Lidar Mission" (MERLIN) was proposed by the German and French space agencies DLR and CNES. MERLIN is now in Phase B, in which all mission components are planned in detail. Launch is foreseen in 2019. The instrument is an integrated path differential absorption (IPDA) lidar which, installed on a low earth orbit platform provided by CNES, uses the surface backscatter to measure the atmospheric methane column. The globally observed concentration gradients will primarily help inverse numerical models to better infer regional methane fluxes. The lidar signals are able to travel through optically thin cloud and aerosol layers without producing a bias, and MERLIN's small field of view, of order 100 m, is expected to provide observations in broken cloud environments, often encountered in the tropics. As IPDA is a novel technique, calibration and validation will be essential. It is foreseen to validate MERLIN by under-flying the satellite with another IPDA lidar, CHARM-F, and a passive remote sensor, both airborne. However, active and passive remote sensors have different, pressure and temperature dependent measurements sensitivities (weighting functions), different fields of view, and do not sample the total methane column on-board an aircraft. Furthermore, since the methane profile is not constant, its column depends on the height of the boundary layer and of the tropopause. We investigate the impact of these issues on the expected validation accuracy, and we examine whether the ground-based Total Carbon Column Observing Network (TCCON) may be useful for validation, too. Finally, validation opportunities are dependent on the location and size of cloud-free regions, since clouds with

  9. Data analysis for space-based gravitational wave detectors

    NASA Astrophysics Data System (ADS)

    Crowder, Jefferson Osborn

    With the launch of the Laser Interferometer Space Antenna (LISA) expected for the next decade, the nascent field of gravitational wave astronomy will be taking a giant leap forward. The data that will be gathered from space-borne gravitational wave detectors such as LISA will provide an expansive look through a new window on the Universe. This dissertation is presented to help open that window by exploring some of the techniques and methods that will be needed to understand the data from these detectors. The first original work presented here investigates the resolution of LISA and follow-on space-based gravitational wave missions. This work presents the methods of measuring the precision of these detectors and gives results for their resolving power for a large class of expected gravitational wave sources. The second original investigation involves the effect that multiple gravitational wave sources will have on the resolution of LISA. Previous results concerning detector resolution were limited to isolated sources of gravitational waves. As LISA is an all-sky detector, it is necessary to understand the role played by concurrent detection of numerous sources. This work derives an extension of the Fisher Information Matrix approach for determining parameter resolution, and applies it to multiple sources for LISA. The next original work is an exploration of the method of genetic algorithms on the problem of extracting the binary parameters of gravitational wave sources from the LISA data stream. These are global algorithms providing a means to cover the entire search space of parameter values. This work describes the basics of and provides the results for such genetic algorithm-based searches, with a focus on improving algorithm efficiency. The last original work included is a study of Markov Chain Monte Carlo (MCMC) methods applied to parameter extraction of gravitational wave sources in the LISA data stream. This work shows how an MCMC approach provides a global

  10. Space-based societal applications—Relevance in developing countries

    NASA Astrophysics Data System (ADS)

    Bhaskaranarayana, A.; Varadarajan, C.; Hegde, V. S.

    2009-11-01

    (ISRO) is already a part of the International initiative called Satellite Aided Search and Rescue System. The programme to set up satellite-based Village Resource Centres (VRCs) across India, for providing a variety of services relevant to the rural communities, is also a unique societal application of space technology. The VRCs are envisaged as single window delivery mechanism for a variety of space-based products and services, such as tele-education; telemedicine; information on natural resources for planning and development at local level; interactive advisories on agriculture, fisheries, land and water resources management, livestock management, etc.; interactive vocational training towards alternative livelihood; e-governance; weather information; etc. This paper describes the various possibilities and potentials of Satcom and Remote Sensing technologies for societal applications. The initiatives taken by Indian Space Research Organisation in this direction are highlighted.

  11. Modeling space-based multispectral imaging systems with DIRSIG

    NASA Astrophysics Data System (ADS)

    Brown, Scott D.; Sanders, Niek J.; Goodenough, Adam A.; Gartley, Michael

    2011-06-01

    The Landsat Data Continuity Mission (LDCM) focuses on a next generation global coverage, imaging system to replace the aging Landsat 5 and Landsat 7 systems. The major difference in the new system is the migration from the multi-spectral whiskbroom design employed by the previous generation of sensors to modular focal plane, multi-spectral pushbroom architecture. Further complicating the design shift is that the reflective and thermal acquisition capability is split across two instruments spatially separated on the satellite bus. One of the focuses of the science and engineering teams prior to launch is the ability to provide seamless data continuity with the historic Landsat data archive. Specifically, the challenges of registering and calibrating data from the new system so that long-term science studies are minimally impacted by the change in the system design. In order to provide the science and engineering teams with simulated pre-launch data, an effort was undertaken to create a robust end-to-end model of the LDCM system. The modeling environment is intended to be flexible and incorporate measured data from the actual system components as they were completed and integrated. The output of the modeling environment needs to include not only radiometrically robust imagery, but also the meta-data necessary to exercise the processing pipeline. This paper describes how the Digital Imaging and Remote Sensing Image Generation (DIRSIG) model has been utilized to model space-based, multi-spectral imaging (MSI) systems in support of systems engineering trade studies. A mechanism to incorporate measured focal plane projections through the forward optics is described. A hierarchal description of the satellite system is presented including the details of how a multiple instrument platform is described and modeled, including the hierarchical management of temporally correlated jitter that allows engineers to explore impacts of different jitter sources on instrument

  12. OGLE-2015-BLG-0479LA,B: Binary Gravitational Microlens Characterized by Simultaneous Ground-based and Space-based Observations

    NASA Astrophysics Data System (ADS)

    Han, C.; Udalski, A.; Gould, A.; Zhu, Wei; Street, R. A.; Yee, J. C.; Beichman, C.; Bryden, C.; Calchi Novati, S.; Carey, S.; Fausnaugh, M.; Gaudi, B. S.; Henderson, Calen B.; Shvartzvald, Y.; Wibking, B.; (The Spitzer Microlensing Team; Szymański, M. K.; Soszyński, I.; Skowron, J.; Mróz, P.; Poleski, R.; Pietrukowicz, P.; Kozłowski, S.; Ulaczyk, K.; Wyrzykowski, Ł.; Pawlak, M.; (The OGLE Collaboration; Tsapras, Y.; Hundertmark, M.; Bachelet, E.; Dominik, M.; Bramich, D. M.; Cassan, A.; Figuera Jaimes, R.; Horne, K.; Ranc, C.; Schmidt, R.; Snodgrass, C.; Wambsganss, J.; Steele, I. A.; Menzies, J.; Mao, S.; (The RoboNet collaboration; Bozza, V.; Jørgensen, U. G.; Alsubai, K. A.; Ciceri, S.; D’Ago, G.; Haugbølle, T.; Hessman, F. V.; Hinse, T. C.; Juncher, D.; Korhonen, H.; Mancini, L.; Popovas, A.; Rabus, M.; Rahvar, S.; Scarpetta, G.; Skottfelt, J.; Southworth, J.; Starkey, D.; Surdej, J.; Wertz, O.; Zarucki, M.; MiNDSTEp Consortium, (The; Pogge, R. W.; DePoy, D. L.; (The μFUN Collaboration

    2016-09-01

    We present a combined analysis of the observations of the gravitational microlensing event OGLE-2015-BLG-0479 taken both from the ground and by the Spitzer Space Telescope. The light curves seen from the ground and from space exhibit a time offset of ∼13 days between the caustic spikes, indicating that the relative lens-source positions seen from the two places are displaced by parallax effects. From modeling the light curves, we measure the space-based microlens parallax. Combined with the angular Einstein radius measured by analyzing the caustic crossings, we determine the mass and distance of the lens. We find that the lens is a binary composed of two G-type stars with masses of ∼1.0 M ⊙ and ∼0.9 M ⊙ located at a distance of ∼3 kpc. In addition, we are able to constrain the complete orbital parameters of the lens thanks to the precise measurement of the microlens parallax derived from the joint analysis. In contrast to the binary event OGLE-2014-BLG-1050, which was also observed by Spitzer, we find that the interpretation of OGLE-2015-BLG-0479 does not suffer from the degeneracy between (±, ±) and (±, ∓) solutions, confirming that the four-fold parallax degeneracy in single-lens events collapses into the two-fold degeneracy for the general case of binary-lens events. The location of the blend in the color–magnitude diagram is consistent with the lens properties, suggesting that the blend is the lens itself. The blend is bright enough for spectroscopy and thus this possibility can be checked from future follow-up observations.

  13. AN EFFICIENT METHOD FOR MODELING HIGH-MAGNIFICATION PLANETARY MICROLENSING EVENTS

    SciTech Connect

    Bennett, David P.

    2010-06-20

    I present a previously unpublished method for calculating and modeling multiple lens microlensing events that is based on the image centered ray-shooting approach of Bennett and Rhie. It has been used to model a wide variety of binary and triple lens systems, but it is designed to efficiently model high-magnification planetary microlensing events, because these high-magnification events are, by far, the most challenging events to model. It is designed to be efficient enough to handle complicated microlensing events, which include more than two lens masses and lens orbital motion. This method uses a polar coordinate integration grid with a smaller grid spacing in the radial direction than in the angular direction, and it employs an integration scheme specifically designed to handle limb-darkened sources. I present tests that show that these features achieve second-order accuracy for the light curves of a number of high-magnification planetary events. They improve the precision of the calculations by a factor of >100 compared to first-order integration schemes with the same grid spacing in both directions (for a fixed number of grid points). This method also includes a {chi}{sup 2} minimization method, based on the Metropolis algorithm, that allows the jump function to vary in a way that allows quick convergence to {chi}{sup 2} minima. Finally, I introduce a global parameter space search strategy that allows a blind search of parameter space for light curve models without requiring {chi}{sup 2} minimization over a large grid of fixed parameters. Instead, the parameter space is explored on a grid of initial conditions for a set of {chi}{sup 2} minimizations using the full parameter space. While this method may be somewhat faster than methods that find the {chi}{sup 2} minima over a large grid of parameters, I argue that the main strength of this method is for events with the signals of multiple planets, where a much higher dimensional parameter space must be explored

  14. Commercial off the Shelf Ground Control Supports Calibration and Conflation from Ground to Space Based Sensors

    NASA Astrophysics Data System (ADS)

    Danielová, M.; Hummel, P.

    2016-06-01

    The need for rapid deployment of aerial and satellite imagery in support of GIS and engineering integration projects require new sources of geodetic control to ensure the accuracy for geospatial projects. In the past, teams of surveyors would need to deploy to project areas to provide targeted or photo identifiable points that are used to provide data for orthorecificaion, QA/QC and calibration for multi-platform sensors. The challenge of integrating street view, UAS, airborne and Space based sensors to produce the common operational picture requires control to tie multiple sources together. Today commercial off the shelf delivery of existing photo identifiable control is increasing the speed of deployment of this data without having to revisit sites over and over again. The presentation will discuss the processes developed by CompassData to build a global library of 40,000 control points available today. International Organization for Standardization (ISO) based processes and initiatives ensure consistent quality of survey data, photo identifiable features selected and meta data to support photogrammetrist, engineers and GIS professionals to quickly deliver projects with better accuracy.

  15. A Ten Year Record of Space Based Lightning Measurements

    NASA Astrophysics Data System (ADS)

    Conover, H.; Hardin, D. M.; Goodman, M.; Blakeslee, R.; Graves, S.; Jones, S.; Harrison, S.; Drewry, M.; Nair, M.

    2009-12-01

    The Lightning Imaging Sensor (LIS) is a space based instrument used to detect the distribution and variability of total lightning (cloud-to-cloud, intracloud, and cloud-to-ground lightning) that occurs in the tropical regions of the globe. LIS was launched in November 1997 aboard NASA’s Tropical Rainfall Measuring Mission (TRMM). The LIS sensor contains a staring imager which is optimized to locate and detect lightning with storm-scale resolution of 3-6 km (3 at nadir, 6 at limb) over a large region (550-550 km) of the Earth's surface. The field of view (FOV) is sufficient to observe a point on the Earth or a cloud for 80 seconds, adequate to estimate the flashing rate of many storms. The instrument records the time of occurrence of a lightning event, measures the radiant energy, and estimates the location. The excellent performance of LIS has lead to numerous scientific discoveries such as: The global lightning flash rate is on the order of 40 flashes per second as compared to the commonly accepted value of 100, an estimate that dates back to 1925. Seventy percent of all lightning activity occurs in the tropics, with the global distribution dominated by the summertime lightning activity over the N. Hemisphere land masses. A new understanding on the interplay among the intensification of updraft, lightning bursts, and the onset of severe weather lead to establishment of a validation campaign that further explored relationships between lightning and severe weather. Findings to date indicate that high flash rate storms have a high probability of becoming severe. A ten year global lightning data archive has been developed from the Lightning Imaging Sensor. This archive is maintained at the Global Hydrology Resource Center (GHRC) in Huntsville Alabama, one of NASA’s Earth science data centers, managed by the Information Technology and Systems Center of UAHuntsville. This is the most comprehensive global lightning data archive ever produced and is noteworthy for its

  16. Non Radiation Hardened Microprocessors in Spaced Based Remote Sensing Systems

    NASA Technical Reports Server (NTRS)

    Decoursey, Robert J.; Estes, Robert F.; Melton, Ryan

    2006-01-01

    The CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) mission is a comprehensive suite of active and passive sensors including a 20Hz 230mj Nd:YAG lidar, a visible wavelength Earth-looking camera and an imaging infrared radiometer. CALIPSO flies in formation with the Earth Observing System Post-Meridian (EOS PM) train, provides continuous, near-simultaneous measurements and is a planned 3 year mission. CALIPSO was launched into a 98 degree sun synchronous Earth orbit in April of 2006 to study clouds and aerosols and acquires over 5 gigabytes of data every 24 hours. The ground track of one CALIPSO orbit as well as high and low intensity South Atlantic Anomaly outlines is shown. CALIPSO passes through the SAA several times each day. Spaced based remote sensing systems that include multiple instruments and/or instruments such as lidar generate large volumes of data and require robust real-time hardware and software mechanisms and high throughput processors. Due to onboard storage restrictions and telemetry downlink limitations these systems must pre-process and reduce the data before sending it to the ground. This onboard processing and realtime requirement load may mean that newer more powerful processors are needed even though acceptable radiation-hardened versions have not yet been released. CALIPSO's single board computer payload controller processor is actually a set of four (4) voting non-radiation hardened COTS Power PC 603r's built on a single width VME card by General Dynamics Advanced Information Systems (GDAIS). Significant radiation concerns for CALIPSO and other Low Earth Orbit (LEO) satellites include the South Atlantic Anomaly (SAA), the north and south poles and strong solar events. Over much of South America and extending into the South Atlantic Ocean the Van Allen radiation belts dip to just 200-800km and spacecraft entering this area are subjected to high energy protons and experience higher than normal Single Event Upset

  17. 78 FR 65006 - National Space-Based Positioning, Navigation, and Timing (PNT) Advisory Board; Meeting

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-10-30

    ... SPACE ADMINISTRATION National Space-Based Positioning, Navigation, and Timing (PNT) Advisory Board; Meeting AGENCY: National Aeronautics and Space Administration (NASA). ACTION: Notice of meeting. SUMMARY... President's 2004 U.S. Space-Based Positioning, Navigation, and Timing (PNT) Policy, the National...

  18. 78 FR 23598 - National Space-Based Positioning, Navigation, and Timing (PNT) Advisory Board; Meeting

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-04-19

    ... SPACE ADMINISTRATION National Space-Based Positioning, Navigation, and Timing (PNT) Advisory Board; Meeting AGENCY: National Aeronautics and Space Administration (NASA). ACTION: Notice of Meeting. SUMMARY... President's 2004 U.S. Space-Based Positioning, Navigation, and Timing (PNT) Policy, the National...

  19. 76 FR 65540 - National Space-Based Positioning, Navigation, and Timing (PNT) Advisory Board; Meeting

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-10-21

    ... SPACE ADMINISTRATION National Space-Based Positioning, Navigation, and Timing (PNT) Advisory Board; Meeting AGENCY: National Aeronautics and Space Administration (NASA). ACTION: Notice of meeting. SUMMARY...'s 2004 U.S. Space-Based Positioning, Navigation, and Timing Policy, the National Aeronautics...

  20. 77 FR 44288 - National Space-Based Positioning, Navigation, and Timing (PNT) Advisory Board; Meeting

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-07-27

    ... SPACE ADMINISTRATION National Space-Based Positioning, Navigation, and Timing (PNT) Advisory Board; Meeting AGENCY: National Aeronautics and Space Administration (NASA). ACTION: Notice of meeting. SUMMARY... President's 2004 U.S. Space-Based Positioning, Navigation, and Timing (PNT) Policy, the National...

  1. Simulator for Microlens Planet Surveys

    NASA Astrophysics Data System (ADS)

    Ipatov, Sergei I.; Horne, Keith; Alsubai, Khalid A.; Bramich, Daniel M.; Dominik, Martin; Hundertmark, Markus P. G.; Liebig, Christine; Snodgrass, Colin D. B.; Street, Rachel A.; Tsapras, Yiannis

    2014-04-01

    We summarize the status of a computer simulator for microlens planet surveys. The simulator generates synthetic light curves of microlensing events observed with specified networks of telescopes over specified periods of time. Particular attention is paid to models for sky brightness and seeing, calibrated by fitting to data from the OGLE survey and RoboNet observations in 2011. Time intervals during which events are observable are identified by accounting for positions of the Sun and the Moon, and other restrictions on telescope pointing. Simulated observations are then generated for an algorithm that adjusts target priorities in real time with the aim of maximizing planet detection zone area summed over all the available events. The exoplanet detection capability of observations was compared for several telescopes.

  2. Enhanced light extraction from UV LEDs using spin-on glass microlenses

    NASA Astrophysics Data System (ADS)

    Liu, Chi-Min; Su, Guo-Dung J.

    2016-05-01

    In this paper, we present a cost-effective method for fabricating spin-on glass (SOG) microlens arrays (MLAs) on ultra-violet light-emitting diodes. The SOG MLA is formed using thermal reflow molds and multiple replication processes, which can reduce the cost of the solution process. In this paper, we fabricate SOG MLA of different sizes, where the diameter of each microlens is approximately 50, 100, 150, and 200 μm. In each case, the light extraction efficiency is improved by 21.86%, 14.01%, 10.35%, and 7.31%, respectively. We also discuss the effects of different-shaped SOG microlenses, namely circular, square, and hexagonal. The light extraction efficiency is improved by 7.31%, 9.60%, and 13.80% for the circular, square, and hexagonal SOG MLAs, respectively. By applying an optimized lens pattern, an increase in light extraction efficiency of 21.86% is achieved.

  3. VizieR Online Data Catalog: OGLE-III Galactic bulge microlensing events (Wyrzykowski+, 2015)

    NASA Astrophysics Data System (ADS)

    Wyrzykowski, L.; Rynkiewicz, A. E.; Skowron, J.; Kozlowski, S.; Udalski, A.; Szymanski, M. K.; Kubiak, M.; Soszynski, I.; Pietrzynski, G.; Poleski, R.; Pietrukowicz, P.; Pawlak, M.

    2015-02-01

    The data used in this work were photometry of 150 million objects toward more than 31deg2 of the Galactic bulge observed in almost 74000 frames, i.e., about 11000 billion data points. We selected 91 fields out of all 177 ever observed by the Optical Gravitational Lensing Experiment (OGLE) Udalski et al. (2008AcA....58...69U) in its third phase from 2001 July until 2009 May, which had at least 250 observations. We use the re-reduced data obtained after the end of OGLE-III. For the final sample of microlensing events, we additionally produced new photometry which took into account the exact position of each event on the difference imaging technique (DIA, Wozniak 2000, J/AcA/50/421) image (see section 2). (4 data files).

  4. Energy Dependent X-Ray Microlensing and the Structure of Quasars

    NASA Astrophysics Data System (ADS)

    Kochanek, C.

    2012-10-01

    The structure of the X-ray emitting regions of quasars remains an open question. Using microlensing in lensed quasars, we can now constrain the sizes, finding that they are compact compared to the UV emission {2500A} with 1/2 light radii of 10-30 gravitational radii. We propose measuring the relative sizes of the hard and soft X-ray emission, better constraining the overall X-ray sizes and comparing them to the hottest regions of the accretion disk by coarsely monitoring 6 lenses with CXO {6 epochs each} and 5 with HST/UV {2 epochs}. In essence, the variability amplitudes of the X-ray/UV compared to our well-sampled optical light curves allows us to measure the sizes. We request 2/3 {1/3} of the time in Cycle 14 {15} for a total of 864 ks {with slew tax} and 12 HST orbits.

  5. Energy Dependent X-Ray Microlensing and the Structure of Quasars

    NASA Astrophysics Data System (ADS)

    Kochanek, Christopher

    2012-09-01

    The structure of the X-ray emitting regions of quasars remains an open question. Using microlensing in lensed quasars, we can now constrain the sizes, finding that they are compact compared to the UV emission (2500A) with 1/2 light radii of ~10-30 gravitational radii. We propose measuring the relative sizes of the hard and soft X-ray emission, better constraining the overall X-ray sizes and comparing them to the hottest regions of the accretion disk by coarsely monitoring 6 lenses with CXO (6 epochs each) and 5 with HST/UV (2 epochs). In essence, the variability amplitudes of the X-ray/UV compared to our well-sampled optical light curves allows us to measure the sizes. We request ~2/3 (1/3) of the time in Cycle 14 (15) for a total of 864~ks (with slew tax) and 12 HST orbits.

  6. Search for low-mass exoplanets by gravitational microlensing at high magnification.

    PubMed

    Abe, F; Bennett, D P; Bond, I A; Eguchi, S; Furuta, Y; Hearnshaw, J B; Kamiya, K; Kilmartin, P M; Kurata, Y; Masuda, K; Matsubara, Y; Muraki, Y; Noda, S; Okajima, K; Rakich, A; Rattenbury, N J; Sako, T; Sekiguchi, T; Sullivan, D J; Sumi, T; Tristram, P J; Yanagisawa, T; Yock, P C M; Gal-Yam, A; Lipkin, Y; Maoz, D; Ofek, E O; Udalski, A; Szewczyk, O; Zebrun, K; Soszynski, I; Szymanski, M K; Kubiak, M; Pietrzynski, G; Wyrzykowski, L

    2004-08-27

    Observations of the gravitational microlensing event MOA 2003-BLG-32/OGLE 2003-BLG-219 are presented, for which the peak magnification was over 500, the highest yet reported. Continuous observations around the peak enabled a sensitive search for planets orbiting the lens star. No planets were detected. Planets 1.3 times heavier than Earth were excluded from more than 50% of the projected annular region from approximately 2.3 to 3.6 astronomical units surrounding the lens star, Uranus-mass planets were excluded from 0.9 to 8.7 astronomical units, and planets 1.3 times heavier than Saturn were excluded from 0.2 to 60 astronomical units. These are the largest regions of sensitivity yet achieved in searches for extrasolar planets orbiting any star. PMID:15333833

  7. OGLE-2011-BLG-0265Lb: A Jovian Microlensing Planet Orbiting an M Dwarf

    NASA Astrophysics Data System (ADS)

    Skowron, J.; Shin, I.-G.; Udalski, A.; Han, C.; Sumi, T.; Shvartzvald, Y.; Gould, A.; Dominis Prester, D.; Street, R. A.; Jørgensen, U. G.; Bennett, D. P.; Bozza, V.; Szymański, M. K.; Kubiak, M.; Pietrzyński, G.; Soszyński, I.; Poleski, R.; Kozłowski, S.; Pietrukowicz, P.; Ulaczyk, K.; Wyrzykowski, Ł.; OGLE Collaboration; Abe, F.; Bhattacharya, A.; Bond, I. A.; Botzler, C. S.; Freeman, M.; Fukui, A.; Fukunaga, D.; Itow, Y.; Ling, C. H.; Koshimoto, N.; Masuda, K.; Matsubara, Y.; Muraki, Y.; Namba, S.; Ohnishi, K.; Philpott, L. C.; Rattenbury, N.; Saito, T.; Sullivan, D. J.; Suzuki, D.; Tristram, P. J.; Yock, P. C. M.; MOA Collaboration; Maoz, D.; Kaspi, S.; Friedmann, M.; Wise Group; Almeida, L. A.; Batista, V.; Christie, G.; Choi, J.-Y.; DePoy, D. L.; Gaudi, B. S.; Henderson, C.; Hwang, K.-H.; Jablonski, F.; Jung, Y. K.; Lee, C.-U.; McCormick, J.; Natusch, T.; Ngan, H.; Park, H.; Pogge, R. W.; Yee, J. C.; μFUN Collaboration; Albrow, M. D.; Bachelet, E.; Beaulieu, J.-P.; Brillant, S.; Caldwell, J. A. R.; Cassan, A.; Cole, A.; Corrales, E.; Coutures, Ch.; Dieters, S.; Donatowicz, J.; Fouqué, P.; Greenhill, J.; Kains, N.; Kane, S. R.; Kubas, D.; Marquette, J.-B.; Martin, R.; Menzies, J.; Pollard, K. R.; Ranc, C.; Sahu, K. C.; Wambsganss, J.; Williams, A.; Wouters, D.; PLANET Collaboration; Tsapras, Y.; Bramich, D. M.; Horne, K.; Hundertmark, M.; Snodgrass, C.; Steele, I. A.; RoboNet Collaboration; Alsubai, K. A.; Browne, P.; Burgdorf, M. J.; Calchi Novati, S.; Dodds, P.; Dominik, M.; Dreizler, S.; Fang, X.-S.; Gu, C.-H.; Hardis; Harpsøe, K.; Hessman, F. V.; Hinse, T. C.; Hornstrup, A.; Jessen-Hansen, J.; Kerins, E.; Liebig, C.; Lund, M.; Lundkvist, M.; Mancini, L.; Mathiasen, M.; Penny, M. T.; Rahvar, S.; Ricci, D.; Scarpetta, G.; Skottfelt, J.; Southworth, J.; Surdej, J.; Tregloan-Reed, J.; Wertz, O.; MiNDSTEp Consortium

    2015-05-01

    We report the discovery of a Jupiter-mass planet orbiting an M-dwarf star that gave rise to the microlensing event OGLE-2011-BLG-0265. Such a system is very rare among known planetary systems and thus the discovery is important for theoretical studies of planetary formation and evolution. High-cadence temporal coverage of the planetary signal, combined with extended observations throughout the event, allows us to accurately model the observed light curve. However, the final microlensing solution remains degenerate, yielding two possible configurations of the planet and the host star. In the case of the preferred solution, the mass of the planet is {{M}p}=0.9+/- 0.3 {{M}J}, and the planet is orbiting a star with a mass M=0.22+/- 0.06 {{M}⊙ }. The second possible configuration (2σ away) consists of a planet with {{M}p}=0.6+/- 0.3 {{M}J} and host star with M=0.14+/- 0.06 {{M}⊙ }. The system is located in the Galactic disk 3-4 kpc toward the Galactic bulge. In both cases, with an orbit size of 1.5-2.0 AU, the planet is a “cold Jupiter”—located well beyond the “snow line” of the host star. Currently available data make the secure selection of the correct solution difficult, but there are prospects for lifting the degeneracy with additional follow-up observations in the future, when the lens and source star separate.

  8. MOA-2011-BLG-293LB: First microlensing planet possibly in the habitable zone

    SciTech Connect

    Batista, V.; Gould, A.; Yee, J. C.; Gaudi, B. S.; Beaulieu, J.-P.; Bennett, D. P.; Fukui, A.; Sumi, T.; Udalski, A. E-mail: gould@astronomy.ohio-state.edu E-mail: beaulieu@iap.fr E-mail: afukui@oao.nao.ac.jp E-mail: udalski@astrouw.edu.pl

    2014-01-01

    We used Keck adaptive optics observations to identify the first planet discovered by microlensing to lie in or near the habitable zone, i.e., at projected separation r = 1.1 ± 0.1 AU from its M{sub L} = 0.86 ± 0.06 M {sub ☉} host, being the highest microlensing mass definitely identified. The planet has a mass m{sub p} = 4.8 ± 0.3 M {sub Jup}, and could in principle have habitable moons. This is also the first planet to be identified as being in the Galactic bulge with good confidence: D{sub L} = 7.72 ± 0.44 kpc. The planet/host masses and distance were previously not known, but only estimated using Bayesian priors based on a Galactic model. These estimates had suggested that the planet might be a super-Jupiter orbiting an M dwarf, a very rare class of planets. We obtained high-resolution JHK images using Keck adaptive optics to detect the lens and so test this hypothesis. We clearly detect light from a G dwarf at the position of the event, and exclude all interpretations other than that this is the lens with high confidence (95%), using a new astrometric technique. The calibrated magnitude of the planet host star is H{sub L} = 19.16 ± 0.13. We infer the following probabilities for the three possible orbital configurations of the gas giant planet: 53% to be in the habitable zone, 35% to be near the habitable zone, and 12% to be beyond the snow line, depending on the atmospherical conditions and the uncertainties on the semimajor axis.

  9. Using graphical and pictorial representations to teach introductory astronomy students about the detection of extrasolar planets via gravitational microlensing

    NASA Astrophysics Data System (ADS)

    Wallace, Colin S.; Chambers, Timothy G.; Prather, Edward E.; Brissenden, Gina

    2016-05-01

    The detection and study of extrasolar planets is an exciting and thriving field in modern astrophysics and an increasingly popular topic in introductory astronomy courses. One detection method relies on searching for stars whose light has been gravitationally microlensed by an extrasolar planet. In order to facilitate instructors' abilities to bring this interesting mix of general relativity and extrasolar planet detection into the introductory astronomy classroom, we have developed a new Lecture-Tutorial called "Detecting Exoplanets with Gravitational Microlensing." In this paper, we describe how this new Lecture-Tutorial's representations of astrophysical phenomena, which we selected and created based on theoretically motivated considerations of their pedagogical affordances, are used to help introductory astronomy students develop more expert-like reasoning abilities.

  10. Elastomeric inverse moulding and vacuum casting process characterization for the fabrication of arrays of concave refractive microlenses

    NASA Astrophysics Data System (ADS)

    Desmet, L.; Van Overmeire, S.; Van Erps, J.; Ottevaere, H.; Debaes, C.; Thienpont, H.

    2007-01-01

    We present a complete and precise quantitative characterization of the different process steps used in an elastomeric inverse moulding and vacuum casting technique. We use the latter replication technique to fabricate concave replicas from an array of convex thermal reflow microlenses. During the inverse elastomeric moulding we obtain a secondary silicone mould of the original silicone mould in which the master component is embedded. Using vacuum casting, we are then able to cast out of the second mould several optical transparent poly-urethane arrays of concave refractive microlenses. We select ten particular representative microlenses on the original, the silicone moulds and replica sample and quantitatively characterize and statistically compare them during the various fabrication steps. For this purpose, we use several state-of-the-art and ultra-precise characterization tools such as a stereo microscope, a stylus surface profilometer, a non-contact optical profilometer, a Mach-Zehnder interferometer, a Twyman-Green interferometer and an atomic force microscope to compare various microlens parameters such as the lens height, the diameter, the paraxial focal length, the radius of curvature, the Strehl ratio, the peak-to-valley and the root-mean-square wave aberrations and the surface roughness. When appropriate, the microlens parameter under test is measured with several different measuring tools to check for consistency in the measurement data. Although none of the lens samples shows diffraction-limited performance, we prove that the obtained replicated arrays of concave microlenses exhibit sufficiently low surface roughness and sufficiently high lens quality for various imaging applications.

  11. Searching for extra-solar planets and probing the atmosphere of Bulge giant stars through gravitational microlensing

    NASA Astrophysics Data System (ADS)

    Cassan, Arnaud

    2005-12-01

    A galactic microlensing effect occurs when a luminous object (the source) located in the Bulge of the Milky Way is temporarily magnified by an intervening star (the "microlens'') passing close to its line of sight. This phenomenom is used for searching extra-solar planets and constraining their abundance, as well as probing the atmosphere of Bulge giant stars. The PLANET collaboration (Probing Lensing Anomalies NETwork) monitors carefully chosen ongoing microlensing events on a round-the-clock basis from observatories in the southern hemisphere. Mathematical and numerical methods are developed to deal with both the highly non-linear equations and the wide parameter space plagued with many local minima. Microlensing exoplanet detection is possible because planets can induce perturbations to the standard lensing light curves. Its sensitivity can go down to Earth-mass planets, thanks to gravitational caustics that arise from a binary lens. If crossed by the source, additional secondary magnification peaks in the light curve can occur. OGLE 2005-BLG-390Lb is the third extra-solar planet detected by this method so far, and its discovery is reported here. It is the lightest exoplanet to date - about five Earth masses - located at a rather large distance of its star, that is about three astronomical units. A selection of microlensing events monitored during the 1995-2004 period was used to derive limits on exoplanets abundance around red dwarf stars. The method is described and detection efficiency diagrams are provided as a basis of the statistical analysis. Last, a differential magnification effect over the disk of the source star is used as a tool to probe Bulge giants stellar atmospheres. Limb-darkening parameters of a set of stars have been measured and compared to atmosphere models. Moreover, a high-resolution spectroscopic monitoring of a Bulge G5III giant at 9 kpc made possible both the measurement of the individual lines equivalent width and the direct detection

  12. Integrated NASA Lidar System Strategy for Space-Based Remote Sensing

    NASA Technical Reports Server (NTRS)

    Singh, Upendra N.; Heaps, William S.; Krebs, Carolyn A. (Technical Monitor)

    2002-01-01

    Recent peer reviews of' NASA's space-based lidar missions and of the technology readiness of lasers appropriate for space-based lidars indicated a critical need for an integrated research and development strategy to move laser transmitter technology from low technical readiness levels to the higher levels required for space missions. This paper presents a multi-Center efforts leading to formulation of an integrated NASA strategy to provide the technology and maturity of systems necessary to make Lidar/Laser systems viable for space-based study and monitoring of the earth's atmosphere.

  13. Alaska at the Crossroads of Migration: Space Based Ornithology

    NASA Technical Reports Server (NTRS)

    Deppe, Jill; Wessels, Konrad; Smith, James A.

    2007-01-01

    Understanding bird migration on a global scale is one of the most compelling and challenging problems of modern biology with major implications for human health and conservation biology. Revolutionary advances in remote sensing now provide us with near real-time measurements of atmospheric and land surface conditions at high spatial resolution over entire continents. We use spatially-explicit, individual based bird migration models driven by numerical weather prediction models of atmospheric conditions, dynamic habitat suitability maps derived from remotely sensed land surface conditions, biophysiological models, and biological field data to simulate migration routes, timing, energy budgets, and survival of individual birds and populations. Long-distance migratory birds travel annually between breeding grounds in Alaska and wintering grounds in Latin Amierica. Approximately 25% of these species are potential vectors of Avian Influenza. Alaska is at the crossroads of Asian and New World migratory flyways and is likely to be a point of introduction of Asian H5N1 AI into the western hemisphere. If/when an infected bird is detected, a pressing question will be where was this bird several days ago, and where is it likely to go after it was released from the survey site? Answers to such questions will increase effectiveness of AI surveillance and mitigation measures. From a conservation perspective, Alaska's diverse landscape provides breeding sites for many migrants, and climatic and land surface changes along migratory flyways in the western hemisphere may reduce bird survival and physical condition upon arrival at Alaskan breeding territories, success and migrant populations.

  14. Design and fabrication of a chirped array of refractive ellipsoidal micro-lenses for an apposition eye camera objective

    NASA Astrophysics Data System (ADS)

    Wippermann, Frank; Duparré, Jacques; Schreiber, Peter; Dannberg, Peter

    2005-09-01

    Apposition compound eye camera objectives are one approach for a vast reduction of the optical system length of an imaging optical sensor. Despite imaging the complete field of view through one aperture like in classical lenses, these objectives split the overall field of view in separated channels which are located adjoined like in insect eyes. Due to the splitting each channel can be optimized for reduction of aberrations occuring under oblique incidence. A correction for astigmatism, field curvature and distortion occurring under oblique incidence can be accomplished by the use of anamorphic micro-lenses leading to an improved resolution of the camera objective. In contrast to regular arrays of equally shaped and equidistant positioned micro-lenses the parameters of the lenses like radii of curvature, center position and angular orientation are functions of the position within the array. These functions can be derived analytically leading to a complete description of the array parameters. We present design considerations for a chirped array containing 130x130 individually shaped ellipsoidal micro-lenses. Melting of photo-resist is employed as fabrication technology for achieving diffraction limited performance. Detailed considerations for the semi-automated layout generation of the photo lithographical masks as well as characterization data of first realized prototypes of the array are given.

  15. OGLE-2012-BLG-0455/MOA-2012-BLG-206: Microlensing event with ambiguity in planetary interpretations caused by incomplete coverage of planetary signal

    SciTech Connect

    Park, H.; Han, C.; Choi, J.-Y.; Hwang, K.-H.; Jung, Y. K.; Shin, I.-G.; Gould, A.; Gaudi, B. S.; Kavka, A.; Pogge, R. W.; Udalski, A.; Sumi, T.; Fouqué, P.; Christie, G.; Natusch, T.; Ngan, H.; Depoy, D. L.; Dong, Subo; Lee, C.-U.; Monard, L. A. G.; Collaboration: μFUN Collaboration; OGLE Collaboration; MOA Collaboration; and others

    2014-05-20

    Characterizing a microlensing planet is done by modeling an observed lensing light curve. In this process, it is often confronted that solutions of different lensing parameters result in similar light curves, causing difficulties in uniquely interpreting the lens system, and thus understanding the causes of different types of degeneracy is important. In this work, we show that incomplete coverage of a planetary perturbation can result in degenerate solutions even for events where the planetary signal is detected with a high level of statistical significance. We demonstrate the degeneracy for an actually observed event OGLE-2012-BLG-0455/MOA-2012-BLG-206. The peak of this high-magnification event (A {sub max} ∼ 400) exhibits very strong deviation from a point-lens model with Δχ{sup 2} ≳ 4000 for data sets with a total of 6963 measurements. From detailed modeling of the light curve, we find that the deviation can be explained by four distinct solutions, i.e., two very different sets of solutions, each with a twofold degeneracy. While the twofold (so-called close/wide) degeneracy is well understood, the degeneracy between the radically different solutions is not previously known. The model light curves of this degeneracy differ substantially in the parts that were not covered by observation, indicating that the degeneracy is caused by the incomplete coverage of the perturbation. It is expected that the frequency of the degeneracy introduced in this work will be greatly reduced with the improvement of the current lensing survey and follow-up experiments and the advent of new surveys.

  16. Application of sunlight and lamps for plant irradiation in space bases

    NASA Technical Reports Server (NTRS)

    Sager, J. C.; Wheeler, R. M.

    1992-01-01

    The radiation sources used for plant growth on a space base must meet the biological requirements for photosynthesis and photomorphogenesis. In addition, the sources must be energy and volume efficient, while maintaining the required irradiance levels, spectral, spatial and temporal distribution. These requirements are not easily met, but as the biological and mission requirements are better defined, then specific facility designs can begin to accommodate both the biological requirements and the physical limitations of a space-based plant growth system.

  17. Application of sunlight and lamps for plant irradiation in space bases.

    PubMed

    Sager, J C; Wheeler, R M

    1992-01-01

    The radiation sources used for plant growth on a space base must meet the biological requirements for photosynthesis and photomorphogenesis. In addition the sources must be energy and volume efficient, while maintaining the required irradiance levels, spectral, spatial and temporal distribution. These requirements are not easily met, but as the biological and mission requirements are better defined, then specific facility designs can begin to accommodate both the biological requirements and the physical limitations of a space based plant growth system. PMID:11537059

  18. Space-based radio telescopes and an orbiting deep-space relay station

    NASA Technical Reports Server (NTRS)

    Powell, R. V.

    1979-01-01

    Foremost among the candidates for early utilization of the Shuttle-launched self-deployable structures are the space-based radio telescopes. Several space-based telescopes are examined including an orbiting VLBI terminal, an orbiting submillimeter telescope, and a large ambient deployable IR telescope. Particular consideration is given to the high-gain Orbiting Deep-Space Relay Station for communication with deep-space probes. Details of deployable antenna technology are discussed.

  19. Autonomous Sub-Pixel Satellite Track Endpoint Determination for Space Based Images

    SciTech Connect

    Simms, L M

    2011-03-07

    An algorithm for determining satellite track endpoints with sub-pixel resolution in spaced-based images is presented. The algorithm allows for significant curvature in the imaged track due to rotation of the spacecraft capturing the image. The motivation behind the subpixel endpoint determination is first presented, followed by a description of the methodology used. Results from running the algorithm on real ground-based and simulated spaced-based images are shown to highlight its effectiveness.

  20. On the age of Galactic bulge microlensed dwarf and subgiant stars

    NASA Astrophysics Data System (ADS)

    Valle, G.; Dell'Omodarme, M.; Prada Moroni, P. G.; Degl'Innocenti, S.

    2015-05-01

    Context. Recent results by Bensby and collaborators on the ages of microlensed dwarf and subgiant stars in the Galactic bulge have challenged the picture of an exclusively old stellar population, because ages significantly younger than 9 Gyr have been found. Aims: However, these age estimates have not been independently confirmed with different techniques and theoretical stellar models. One of the aims of this paper is to verify these results by means of a grid-based method. We also quantify the systematic biases that might be induced by some assumptions adopted to compute stellar models. In particular, we explore the impact of increasing the initial helium abundance, neglecting the element microscopic diffusion, and changing the mixing-length calibration in theoretical stellar track computations. Methods: We adopt the SCEPtER pipeline with a newly computed stellar model grid for metallicities [Fe/H] from - 2.00 dex to 0.55 dex, and masses in the range [0.60; 1.60] M⊙ from the zero-age main sequence to the helium flash at the red giant branch tip. By means of Monte Carlo simulations we show for the considered evolutionary phases that our technique provides unbiased age estimates. Results: Our age results are in good agreement with Bensby and collaborators findings and show 16 stars younger than 5 Gyr and 28 younger than 9 Gyr over a sample of 58. The effect of a helium enhancement as large as ΔY/ ΔZ = 5 is quite modest, resulting in a mean age increase of metal rich stars of 0.6 Gyr. Even simultaneously adopting a high helium content and the upper values of age estimates, there is evidence of 4 stars younger than 5 Gyr and 15 younger than 9 Gyr. For stars younger than 5 Gyr, the use of stellar models computed by neglecting microscopic diffusion or by assuming a super-solar mixing-length value leads to a mean increase in the age estimates of about 0.4 Gyr and 0.5 Gyr respectively. Even considering the upper values for the age estimates, there are four stars

  1. Feasibility of performing space surveillance tasks with a proposed space-based optical architecture

    NASA Astrophysics Data System (ADS)

    Flohrer, Tim; Krag, Holger; Klinkrad, Heiner; Schildknecht, Thomas

    Under ESA contract an industrial consortium including Aboa Space Research Oy (ASRO), the Astronomical Institute of the University of Bern (AIUB), and the Dutch National Aerospace Laboratory (NLR), proposed the observation concept, developed a suitable sensor architecture, and assessed the performance of a space-based optical (SBO) telescope in 2005. The goal of the SBO instrumentation was to analyse how the existing knowledge gap in the space debris population in the millimetre and centimetre regime may be closed by means of a passive op-tical instrument. SBO was requested to provide statistical information on the space debris population, in terms of number of objects and size distribution. The SBO was considered to be a cost-efficient instrumentation of 20 cm aperture and 6 deg field-of-view with flexible integration requirements. It should be possible to integrate the SBO easily as a secondary payload on satellites launched into low-Earth orbits (LEO), or into geostationary orbit (GEO). Thus the selected mission concept only allowed for fix-mounted telescopes, and the pointing direction could be requested freely. It was shown in the performance analysis that the statistical information on small-sized space debris can only be collected if the observation ranges are comparatively small. Two of the most promising concepts were to observe objects in LEO from a sensor placed into a sun-synchronous LEO, while objects in GEO should be observed from a GEO satellite. Since 2007 ESA focuses space surveillance and tracking activities in the Space Situational Awareness (SSA) preparatory program. Ground-based radars and optical telescopes are stud-ied for the build-up and to maintenance of a catalogue of objects. In this paper we analyse how the SBO architecture could contribute to the space surveillance tasks survey and tracking. We assume that the SBO instrumentation is placed into a circular sun-synchronous orbit at 800 km altitude. We discuss the observation conditions of

  2. Fabrication of polymer microlenses on single mode optical fibers for light coupling

    NASA Astrophysics Data System (ADS)

    Zaboub, Monsef; Guessoum, Assia; Demagh, Nacer-Eddine; Guermat, Abdelhak

    2016-05-01

    In this paper, we present a technique for producing fibers optics micro-collimators composed of polydimethylsiloxane PDMS microlenses of different radii of curvature. The waist and working distance values obtained enable the optimization of optical coupling between optical fibers, fibers and optical sources, and fibers and detectors. The principal is based on the injection of polydimethylsiloxane (PDMS) into a conical micro-cavity chemically etched at the end of optical fibers. A spherical microlens is then formed that is self-centered with respect to the axis of the fiber. Typically, an optimal radius of curvature of 10.08 μm is obtained. This optimized micro-collimator is characterized by a working distance of 19.27 μm and a waist equal to 2.28 μm for an SMF 9/125 μm fiber. The simulation and experimental results reveal an optical coupling efficiency that can reach a value of 99.75%.

  3. Astrometric Microlensing Constraints on a Massive Body in the Outer Solar System with Gaia

    NASA Astrophysics Data System (ADS)

    Gaudi, B. Scott; Bloom, Joshua S.

    2005-12-01

    A body in solar orbit beyond the Kuiper Belt exhibits an annual parallax that exceeds its apparent proper motion by up to many orders of magnitude. Apparent motion of this body along the parallactic ellipse will deflect the angular position of background stars due to astrometric microlensing (``induced parallax''). By synoptically sampling the astrometric position of background stars over the entire sky, constraints on the existence (and basic properties) of a massive nearby body may be inferred. With a simple simulation, we estimate the signal-to-noise ratio for detecting such a body-as a function of mass, heliocentric distance, and ecliptic latitude-using the anticipated sensitivity and temporal cadences from Gaia (launch date 2011). A Jupiter-mass (MJ) object at 2000 AU is detectable by Gaia over the whole sky above 5 σ, with even stronger constraints if it lies near the ecliptic plane. Hypotheses for the mass (~3MJ), distance (~20,000 AU), and location of the proposed perturber (``Planet X''), which gives rise to long-period comets, may be testable.

  4. Integral-field spectrophotometry of the quadruple QSO HE 0435-1223: Evidence for microlensing

    NASA Astrophysics Data System (ADS)

    Wisotzki, L.; Becker, T.; Christensen, L.; Helms, A.; Jahnke, K.; Kelz, A.; Roth, M. M.; Sanchez, S. F.

    2003-09-01

    We present the first spatially resolved spectroscopic observations of the recently discovered quadruple QSO and gravitational lens HE 0435-1223. Using the Potsdam Multi-Aperture Spectrophotometer (PMAS), we show that all four QSO components have very similar but not identical spectra. In particular, the spectral slopes of components A, B, and D are indistinguishable, implying that extinction due to dust plays no major role in the lensing galaxy. While also the emission line profiles are identical within the error bars, as expected from lensing, the equivalent widths show significant differences between components. Most likely, microlensing is responsible for this phenomenon. This is also consistent with the fact that component D, which shows the highest relative continuum level, has brightened by 0.07 mag since Dec. 2001. We find that the emission line flux ratios between the components are in better agreement with simple lens models than broad band or continuum measurements, but that the discrepancies between model and data are still unacceptably large. Finally, we present a detection of the lensing galaxy, although this is close to the limits of the data. Comparing with a model galaxy spectrum, we obtain a redshift estimate of zlens=0.44+/- 0.02.

  5. Light micro-lensing effect in biosilica shells of diatoms microalgae

    NASA Astrophysics Data System (ADS)

    De Tommasi, E.; De Stefano, L.; Rea, I.; Moretti, L.; De Stefano, M.; Rendina, I.

    2008-04-01

    Diatoms are monocellular micro-algae provided with external valves, the frustules, made of amorphous hydrated silica. Frustules present patterns of regular arrays of holes, the areolae, characterized by sub-micrometric dimensions. In particular, frustules from centric diatoms are characterized by a radial disposition of areolae and exhibit several optical properties, such as photoluminescence variations in presence of organic vapors and photonic-crystal-like behaviour as long as propagation of electromagnetic field is concerned. We have studied the transmission of coherent light, at different wavelengths, through single frustules of Coscinodiscus Walesii diatoms, a centric species characterized by a diameter of about 150 μm. The frustules showed the ability to focalize the light in a spot of a few μm2, the focal length depending on the wavelength of the incident radiation. This focusing effect takes place at the centre of the frustule, where no areolae are present and, as it is confirmed by numerical simulations, it is probably due to coherent superposition of unfocused wave fronts coming from the surrounding areolae. Diatoms-based micro-lenses could be used in the production of lensed optical fibers without modifying the glass core and, in general, they could be exploited with success in most of the optical micro-arrays.

  6. A Microlensing Measurement of Dark Matter Fractions in Three Lensing Galaxies

    NASA Astrophysics Data System (ADS)

    Bate, N. F.; Floyd, D. J. E.; Webster, R. L.; Wyithe, J. S. B.

    2011-04-01

    Direct measurements of dark matter distributions in galaxies are currently only possible through the use of gravitational lensing observations. Combinations of lens modeling and stellar velocity dispersion measurements provide the best constraints on dark matter distributions in individual galaxies, however they can be quite complex. In this paper, we use observations and simulations of gravitational microlensing to measure the smooth (dark) matter mass fraction at the position of lensed images in three lens galaxies: MG 0414+0534, SDSS J0924+0219, and Q2237+0305. The first two systems consist of early-type lens galaxies, and both display a flux ratio anomaly in their close image pair. Anomalies such as these suggest that a high smooth matter percentage is likely, and indeed we prefer ~50% smooth matter in MG 0414+0534 and ~80% in SDSS J0924+0219 at the projected locations of the lensed images. Q2237+0305 differs somewhat in that its lensed images lie in the central kiloparsec of the barred spiral lens galaxy, where we expect stars to dominate the mass distribution. In this system, we find a smooth matter percentage that is consistent with zero. This paper uses data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

  7. Beyond the Wobbles: Teaching Students About Detecting Planets with the Transit and Gravitational Microlensing Methods

    NASA Astrophysics Data System (ADS)

    Prather, Edward E.; Wallace, Colin Scott; Chambers, Timothy G.; Brissenden, Gina; Traub, Wesley A.; Greene, W. M.; Biferno, Anya A.; Rodriguez, Joshua

    2015-01-01

    Members of the Center for Astronomy Education (CAE) at the University of Arizona's Steward Observatory in collaboration with JPL scientists, visualization experts, and education and public outreach professionals with the Exoplanet Exploration Program (ExEP) have recently completed classroom field-testing of a new suite of educational materials to help learners better understand how extrasolar planets are detected using the transit and gravitational microlensing techniques. This collaboration has created a set of evidence-based Think-Pair-Share questions, Lecture-Tutorials, animations, presentation slides, and instrucotrs guide that can be used together or separately to actively engage learners in reasoning about the data and scientific representations associated with these exciting new extrasolar planet detection methods. In this talk we present several of the conceptually challenging collaborative learning tasks that students encounter with this new suite of educational materials and some of the assessment questions we are using to assess the efficacy of their use in general education, college-level astronomy courses.

  8. A New Nonplanetary Interpretation of the Microlensing Event OGLE-2013-BLG-0723

    NASA Astrophysics Data System (ADS)

    Han, Cheongho; Bennett, David P.; Udalski, Andrzej; Jung, Youn Kil

    2016-07-01

    Recently, the discovery of a Venus-mass planet orbiting a brown-dwarf host in a binary system was reported from the analysis of the microlensing event OGLE-2013-BLG-0723. We reanalyze the event considering the possibility of other interpretations. From this, we find a new solution where the lens is composed of two bodies, in contrast to the three-body solution of the previous analysis. The new solution better explains the observed light curve than the previous solution with Δχ 2 ∼ 202, suggesting that the new solution is a correct model for the event. From the estimation of the physical parameters based on the new interpretation, we find that the lens system is composed of two low-mass stars with ∼0.2 M ⊙ and ∼0.1 M ⊙ and located at a distance of ∼3 kpc. The fact that the physical parameters correspond to those of the most common lens population located at a distance with a large lensing probability further supports the likelihood of the new interpretation. Considering that two dramatically different solutions can approximately explain the observed light curve, the event suggests the need for carefully testing all possible lens-system geometries.

  9. What can we learn about quasars and unification scheme with the microlensing technique?

    NASA Astrophysics Data System (ADS)

    Sluse, D.

    2015-09-01

    Our understanding of the gravitational lensing phenomenon has deeply progressed since the discovery of the "first" gravitationally lensed object in 1979 by Walsh and collaborators. With more than hundreds of quasars known to be multiply imaged by a foreground galaxy, gravitational lensing is now a powerful astrophysical and cosmological tool. The stars located in lensing galaxies produce small deflections of the light rays coming from distant quasars which adds to the main deflection from the lensing galaxy. Because the deflection caused by the stars is small, the micro-images they produce remain unresolved. Only a flickering of the flux and spectral deformation of lensed quasars images are observed. I will explain how this micro-lensing effect, can be used to study the inner region of distant quasars. Specifically, I will zoom out from the inner accretion disc up to the torus, and give an overview of the information which can be retrieved at each of these scales. I will give a special emphasis on the constraint we can put on the orientation/geometry of the various emitting regions (i.e. disc, broad line region, torus) at each of these scales.

  10. Upcoming Microlensing by Proxima Centauri: A Rare Opportunity for Mass Determination and Planet Detection

    NASA Astrophysics Data System (ADS)

    Sahu, Kailash C.; Bond, H. E.; Anderson, J.; Dominik, M.

    2013-06-01

    Proxima Centauri will pass close to two background stars in 2014 and 2016, with impact parameters of about 1.6 and 0.5 arc seconds. Because Proxima is so nearby, its angular Einstein ring radius is large 28 milli arc sec) and will lead to detectable relativistic deflections of the images of the background stars even at those angular separations. Measurement of the astrometric shifts offers a unique opportunity for an accurate determination of the mass of Proxima. Although the background stars are >8.5 mag fainter than Proxima, the large contrast is mitigated by the relatively large separations at which the gravitational deflection is still detectable, and well within the capabilities of the Hubble Space Telescope. The upcoming events also offer the opportunity to detect and determine the masses of planetary companions, either through additional astrometric shifts, or in rare circumstances through a photometric microlensing event, leading to a brightening of the source star. These events would have durations of a few hours to several days.

  11. A MICROLENSING MEASUREMENT OF DARK MATTER FRACTIONS IN THREE LENSING GALAXIES

    SciTech Connect

    Bate, N. F.; Webster, R. L.; Wyithe, J. S. B.; Floyd, D. J. E.

    2011-04-10

    Direct measurements of dark matter distributions in galaxies are currently only possible through the use of gravitational lensing observations. Combinations of lens modeling and stellar velocity dispersion measurements provide the best constraints on dark matter distributions in individual galaxies, however they can be quite complex. In this paper, we use observations and simulations of gravitational microlensing to measure the smooth (dark) matter mass fraction at the position of lensed images in three lens galaxies: MG 0414+0534, SDSS J0924+0219, and Q2237+0305. The first two systems consist of early-type lens galaxies, and both display a flux ratio anomaly in their close image pair. Anomalies such as these suggest that a high smooth matter percentage is likely, and indeed we prefer {approx}50% smooth matter in MG 0414+0534 and {approx}80% in SDSS J0924+0219 at the projected locations of the lensed images. Q2237+0305 differs somewhat in that its lensed images lie in the central kiloparsec of the barred spiral lens galaxy, where we expect stars to dominate the mass distribution. In this system, we find a smooth matter percentage that is consistent with zero.

  12. Gravitational microlensing - Powerful combination of ray-shooting and parametric representation of caustics

    NASA Technical Reports Server (NTRS)

    Wambsganss, J.; Witt, H. J.; Schneider, P.

    1992-01-01

    We present a combination of two very different methods for numerically calculating the effects of gravitational microlensing: the backward-ray-tracing that results in two-dimensional magnification patterns, and the parametric representation of caustic lines; they are in a way complementary to each other. The combination of these methods is much more powerful than the sum of its parts. It allows to determine the total magnification and the number of microimages as a function of source position. The mean number of microimages is calculated analytically and compared to the numerical results. The peaks in the lightcurves, as obtained from one-dimensional tracks through the magnification pattern, can now be divided into two groups: those which correspond to a source crossing a caustic, and those which are due to sources passing outside cusps. We determine the frequencies of those two types of events as a function of the surface mass density, and the probability distributions of their magnitudes. We find that for low surface mass density as many as 40 percent of all events in a lightcurve are not due to caustic crossings, but rather due to passings outside cusps.

  13. Nano- and microlenses as concepts for enhanced performance of solar cells

    NASA Astrophysics Data System (ADS)

    Schmid, Martina; Manley, Phillip

    2015-01-01

    Both metallic nanoparticles exhibiting plasmonic effects and dielectric nanoparticles coupling the light into resonant modes have shown successful applications to photovoltaics. On a larger scale, microconcentrator optics promise to enhance solar cell efficiency and to reduce material consumption. Here, we want to create a link between the concentrators on the nano- and on the microscale. From metallic nanospheres, we turn to dielectric ones and then look at increasing radii to approach the microscale. The lenses are investigated with respect to their interaction with light using three-dimensional simulations with the finite-element method. Resulting maps of local electric field distributions reveal the focusing behavior of the dielectric spheres. For larger lens sizes, ray tracing calculations, which give ray distributions in agreement with electric field intensities, can be applied. Calculations of back focal lengths in geometrical optics coincide with ray tracing results and allow insight into how the focal length can be tuned as a function of particle size, substrate refractive index, and the shape of the microlens. Despite the similarities we find for the nano- and the microlenses, integration into solar cells needs to be carefully adjusted, depending on the goals of material saving, concentration level, focal distance, and lens size.

  14. Detection ability of space-based optical observation system to space debris

    NASA Astrophysics Data System (ADS)

    Zhao, Sisi; Ruan, Ningjuan; Zhuang, Xuxia

    2015-10-01

    For supplying the reference to the spaced-based optical observation system design and performance analysis, the space-based observation mode for space debris is established. Considering the geometry size, the material characteristics, and the distribution region of the debris, the visual magnitude of space debris is calculated in the condition of different detection range and different phase angle. Based on the typical instance, the simulation analysis of the space debris detection ability of space-based optical observation system, which is in LEO orbit and Sub-GEO orbit respectively, is carried out. The results show that the LEO spaced-based optical observation system having an aperture of 25cm can detect the LEO 3cm space debris, which is 100km far away and has the relative velocity of 1km/s, and can also detect the GEO 1m space object, which is 37000km far away and has the relative velocity of 4km/s. The Sub-GEO spaced-based optical observation system having an aperture of 25cm can detect the GEO 1cm space debris, which is 800km far away and has the relative velocity of 15m/s.

  15. PROSPECTS FOR CHARACTERIZING HOST STARS OF THE PLANETARY SYSTEM DETECTIONS PREDICTED FOR THE KOREAN MICROLENSING TELESCOPE NETWORK

    SciTech Connect

    Henderson, Calen B.

    2015-02-10

    I investigate the possibility of constraining the flux of the lens (i.e., host star) for the types of planetary systems the Korean Microlensing Telescope Network is predicted to find. I examine the potential to obtain lens flux measurements by (1) imaging the lens once it is spatially resolved from the source, (2) measuring the elongation of the point-spread function of the microlensing target (lens+source) when the lens and source are still unresolved, and (3) taking prompt follow-up photometry. In each case I simulate the observing programs for a representative example of current ground-based adaptive optics (AO) facilities (specifically NACO on the Very Large Telescope), future ground-based AO facilities (GMTIFS on the Giant Magellan Telescope, GMT), and future space telescopes (NIRCAM on the James Webb Space Telescope, JWST). Given the predicted distribution of relative lens-source proper motions, I find that the lens flux could be measured to a precision of σ{sub H{sub ℓ}}≤0.1 for ≳60% of planet detections ≥5 yr after each microlensing event for a simulated observing program using GMT, which images resolved lenses. NIRCAM on JWST would be able to carry out equivalently high-precision measurements for ∼28% of events Δt = 10 yr after each event by imaging resolved lenses. I also explore the effects various blend components would have on the mass derived from prompt follow-up photometry, including companions to the lens, companions to the source, and unassociated interloping stars. I find that undetected blend stars would cause catastrophic failures (i.e., >50% fractional uncertainty in the inferred lens mass) for ≲ (16 · f {sub bin})% of planet detections, where f {sub bin} is the binary fraction, with the majority of these failures occurring for host stars with mass ≲0.3 M {sub ☉}.

  16. Modeling for space-based visible imaging characteristics of space object

    NASA Astrophysics Data System (ADS)

    Sun, Cheng-Ming; Yuan, Yan; Zhou, Zhi-liang

    2015-09-01

    In order to enhance the capability of space-based surveillance, the detailed modeling for visible imaging characteristics of space object is described in this paper. Firstly, a space-based imaging detection model is built based on the scattering visible radiation from space object. The model consists of radiation transmission based on the bidirectional reflectance distribution function (BRDF) and grayscale transformation based on the 256 levels. Then, according to the position of the sun, object and detector, the imaging conditions such as imaging angle and size are analyzed. Finally, the grayscale images of the HuanJing-1 satellite are simulated. It shows the grayscales for the different regions of the object appear great difference, indicating that the space-based detector needs a larger dynamic range.

  17. Protection of Space-based observations and the International Telecommunication Union (ITU)

    NASA Astrophysics Data System (ADS)

    Ohishi, Masatoshi

    International Telecommunication Union (ITU) is the organization to discuss and establish protection criteria and measures for the space-based observations. The measures are described in the Radio Regulations (RR), that has a status of the international treaty. ITU holds the World Radiocommunication Conference (WRC) every 3-4 years, and the latest one, WRC-2007, established the protection measure for the Radioastron. In the discussion on this issue, the IUCAF and its members played important role, however, only a few people who are familiar with the space-based radio astronomy observations participated in the discussion. It is highly desirable for the space-based radio astronomy researchers to participate in the ITU activity through IUCAF where COSPAR has the official representatives. I will review the ITU structure and the results of WRC-2007 for the COSPAR members to understand the IUCAF and ITU activities.

  18. Preliminary design of reactor power systems for the manned space base.

    NASA Technical Reports Server (NTRS)

    Mckhann, G. G.; Coggi, J. V.; Diamond, S. D.

    1972-01-01

    The results of design integration studies of uranium-zirconium hydride (UZr-Hx) reactor power systems for the NASA space base study program are presented. The power conversion systems investigated include the Brayton cycle, the organic Rankine cycle, the SNAP-8 mercury Rankine cycle, and thermoelectric (PbTe). The proposed space base has a 10-year life and requires 100 kWe of power. Two 50-kWe power systems with a nominal replacement life of 5 years are utilized. Parametric design data such as life, weight, radiator area, reactor outlet-temperature, reactor thermal power, and power conversion system efficiency are presented and used for the design and integration of the system with the space base.

  19. Long-term monitoring, time delay, and microlensing in the gravitational lens system Q0142-100

    SciTech Connect

    Oscoz, A.; Serra-Ricart, M.; Mediavilla, E.

    2013-12-20

    We present 12 yr of monitoring of the gravitational lens Q0142-100 from the Teide Observatory. The data, taken from 1999 to 2010, comprise 105 observing nights with the IAC80 Telescope. The application of the δ{sup 2} method to the dataset leads to a value for the time delay between both components of the system of 72 ± 22 days (68% confidence level), consistent within uncertainties with the most recent results. With this value in mind a possible microlensing event is detected in Q0142-100.

  20. Sample band spreading phenomena in ground and space-based electrophoretic separators

    NASA Technical Reports Server (NTRS)

    Rhodes, Percy H.; Snyder, Robert S.

    1986-01-01

    Sample stream spreading in the transverse direction (direction perpendicular to the chamber center plane) is calculated for two ground-based and one space-based continuous flow electrophoresis chambers. The magnitude of transverse sample stream spreading is shown to be a function of the difference in electrical conductivity between the sample and curtain buffer. Sample/buffer conductivity mismatch distorts the normally uniform electrical field in the vicinity of the sample to produce transverse field components which, in turn, deflect sample material toward the chamber walls. These results indicate that nongravity effects are important and must be resolved in order for space-based continuous flow electrophoresis to achieve its maximum potential.

  1. Ground Support for the Space-Based Range Flight Demonstration 2

    NASA Technical Reports Server (NTRS)

    Burkes, Darryl A.

    2007-01-01

    The primary objective of the NASA Space-Based Range Demonstration and Certification program was to develop and demonstrate space-based range capabilities. The Flight Demonstration 2 flights at NASA Dryden Flight Research Center were conducted to support Range Safety (commanding and position reporting) and high-rate (5 Mbps) Range User (video and data) requirements. Required ground support infrastructure included a flight termination system computer, the ground-data distribution network to send range safety commands and receive range safety and range user telemetry data and video, and the ground processing systems at the Dryden Mission Control Center to process range safety and range user telemetry data and video.

  2. An optimum organizational structure for a large earth-orbiting multidisciplinary Space Base

    NASA Technical Reports Server (NTRS)

    Ragusa, J. M.

    1973-01-01

    The purpose of this exploratory study was to identify an optimum hypothetical organizational structure for a large earth-orbiting multidisciplinary research and applications (R&A) Space Base manned by a mixed crew of technologists. Since such a facility does not presently exist, in situ empirical testing was not possible. Study activity was, therefore, concerned with the identification of a desired organizational structural model rather than the empirical testing of it. The essential finding of this research was that a four-level project type 'total matrix' model will optimize the efficiency and effectiveness of Space Base technologists.

  3. The detection capability of space-based combined system for space debris

    NASA Astrophysics Data System (ADS)

    Zhang, Yalin; Wang, Chao; Fu, Qiang; Zhan, Juntong; Han, Long

    2016-01-01

    It is urgent to tracking and making a catalog for space debris, since they are such serious threats to spacecraft. Space-based detection possess a great of development potential for its low energy consumption, high precision and miniaturization and other features. This paper discussed the capability of space-based combined system that is laser ranging and imaging integrated communication system. With the diameter of 15cm of space debris, the limit distance of communication, ranging and imaging system are discussed. The result shows that the limit distance of communication and energy imaging is longer, and the main factor to limit the distance is ranging and diffraction limit of imaging system.

  4. A PLANETARY LENSING FEATURE IN CAUSTIC-CROSSING HIGH-MAGNIFICATION MICROLENSING EVENTS

    SciTech Connect

    Chung, Sun-Ju; Hwang, Kyu-Ha; Ryu, Yoon-Hyun; Lee, Chung-Uk E-mail: kyuha@kasi.re.kr E-mail: leecu@kasi.re.kr

    2012-05-20

    Current microlensing follow-up observations focus on high-magnification events because of the high efficiency of planet detection. However, central perturbations of high-magnification events caused by a planet can also be produced by a very close or a very wide binary companion, and the two kinds of central perturbations are not generally distinguished without time consuming detailed modeling (a planet-binary degeneracy). Hence, it is important to resolve the planet-binary degeneracy that occurs in high-magnification events. In this paper, we investigate caustic-crossing high-magnification events caused by a planet and a wide binary companion. From this investigation, we find that because of the different magnification excess patterns inside the central caustics induced by the planet and the binary companion, the light curves of the caustic-crossing planetary-lensing events exhibit a feature that is discriminated from those of the caustic-crossing binary-lensing events, and the feature can be used to immediately distinguish between the planetary and binary companions. The planetary-lensing feature appears in the interpeak region between the two peaks of the caustic-crossings. The structure of the interpeak region for the planetary-lensing events is smooth and convex or boxy, whereas the structure for the binary-lensing events is smooth and concave. We also investigate the effect of a finite background source star on the planetary-lensing feature in the caustic-crossing high-magnification events. From this, we find that the convex-shaped interpeak structure appears in a certain range that changes with the mass ratio of the planet to the planet-hosting star.

  5. Planar micro-nano-coils for electrically driving liquid crystal microlenses based on wireless power transmission

    NASA Astrophysics Data System (ADS)

    Chen, Cheng; Hu, Wei; Luo, Jun; Lei, Yu; Tong, Qing; Zhang, Xinyu; Sang, Hongshi; Xie, Changsheng

    2015-12-01

    In this paper, the planar micro-nano-coils (PMNCs) with diverse planar spiral structures are designed for electrically driving and controlling liquid crystal microlenses (LCMs) based on wireless power transmission approaches. The PMNCs with different basic shapes are fabricated, including typical micro-triangle, micro-square, micro-pentagon, micro-hexagon, and micro-circle. According to the designed microstructures, using loop iterative approximation means based on Greenhouse algorithm, the inductance values of the microcoils can be calculated through combining self-inductance with mutual-inductance. In experiments, both the wet and dry etching technologies are adapted to obtain the desired PMNCs over aluminum-coated glass substrates. The etching technologies utilized by us are implemented on initial glass substrates spread by photoresist mask, which has been processed by common ultraviolet lithography. And the wet and dry etching technologies are different in the way of eroding aluminum film. Usually, the wet etching is a kind of the chemical reaction of alkali element in the developing liquid used, but the dry etching is a type of physical etching process such as the ion beam etching so as to fabricate microstructures with smaller size than that of wet etching. After the fabrication of the PMNCs, the electrical testing circuit for the inductance of the PMNCs is built to obtain their actual inductance values. By comparing inductances with theoretical prediction, the improved PMNCs are proposed for driving and controlling LCMs, which demonstrates enhanced light transmission efficiency of the PMNCs, and makes it more efficient to adjust LCMs developed by us.

  6. DETERMINING THE PHYSICAL LENS PARAMETERS OF THE BINARY GRAVITATIONAL MICROLENSING EVENT MOA-2009-BLG-016

    SciTech Connect

    Hwang, K.-H.; Han, C.; Bond, I. A.; Lin, W.; Ling, C. H.; Miyake, N.; Abe, F.; Fukui, A.; Furusawa, K.; Hayashi, F.; Hosaka, S.; Itow, Y.; Kamiya, K.; Makita, S.; Masuda, K.; Bennett, D. P.; Botzler, C. S.; Hearnshaw, J. B.; Kilmartin, P. M.; Korpela, A.

    2010-07-01

    We report the result of the analysis of the light curve of the microlensing event MOA-2009-BLG-016. The light curve is characterized by a short-duration anomaly near the peak and an overall asymmetry. We find that the peak anomaly is due to a binary companion to the primary lens and the asymmetry of the light curve is explained by the parallax effect caused by the acceleration of the observer over the course of the event due to the orbital motion of the Earth around the Sun. In addition, we detect evidence for the effect of the finite size of the source near the peak of the event, which allows us to measure the angular Einstein radius of the lens system. The Einstein radius combined with the microlens parallax allows us to determine the total mass of the lens and the distance to the lens. We identify three distinct classes of degenerate solutions for the binary lens parameters, where two are manifestations of the previously identified degeneracies of close/wide binaries and positive/negative impact parameters, while the third class is caused by the symmetric cycloid shape of the caustic. We find that, for the best-fit solution, the estimated mass of the lower-mass component of the binary is (0.04 {+-} 0.01) M{sub sun}, implying a brown-dwarf companion. However, there exists a solution that is worse only by {Delta}{chi}{sup 2} {approx} 3 for which the mass of the secondary is above the hydrogen-burning limit. Unfortunately, resolving these two degenerate solutions will be difficult as the relative lens-source proper motions for both are similar and small ({approx}1 mas yr{sup -1}) and thus the lens will remain blended with the source for the next several decades.

  7. Properties of Microlensing Events by Wide-separation Planets with a Moon

    NASA Astrophysics Data System (ADS)

    Chung, Sun-Ju; Ryu, Yoon-Hyun

    2016-07-01

    We investigate the properties of microlensing events caused by planetary systems where planets with a moon are widely separated from their host stars. From this investigation, we find that the moon feature generally appears as a very short-duration perturbation on the smooth asymmetric light curve of the lensing event induced by the wide-separation planet; thus it can be easily discriminated from the planet feature responsible for the overall asymmetric light curve. For typical Galactic lensing events with an Einstein radius of ∼2 au, the asymmetry of the light curves due to bound planets can be noticed up to ∼20 au. We also find that the perturbations of wide planetary systems become dominated by the moon as the projected star–planet separation increases, and eventually the light curves of events produced by such systems appear as the single lensing light curve of the planet itself with a very short-duration perturbation induced by the moon, which is a representative light curve of the event induced by a star and a planet, except on the Einstein timescale of the planet. We also study the effect of a finite source star on the moon feature in wide planetary lensing events. From this study, we find that when the lunar caustic is sufficiently separated from the planetary caustic, the lower limit on the ratio of the size of the lunar caustic to the source radius causing a ≥5% lunar deviation depends mostly on the projected planet–moon separation regardless of the moon/star mass ratio, and it decreases as the planet–moon separation becomes smaller or larger than the planetary Einstein radius.

  8. Frequency of Solar-like Systems and of Ice and Gas Giants Beyond the Snow Line from High-magnification Microlensing Events in 2005-2008

    NASA Astrophysics Data System (ADS)

    Gould, A.; Dong, Subo; Gaudi, B. S.; Udalski, A.; Bond, I. A.; Greenhill, J.; Street, R. A.; Dominik, M.; Sumi, T.; Szymański, M. K.; Han, C.; Allen, W.; Bolt, G.; Bos, M.; Christie, G. W.; DePoy, D. L.; Drummond, J.; Eastman, J. D.; Gal-Yam, A.; Higgins, D.; Janczak, J.; Kaspi, S.; Kozłowski, S.; Lee, C.-U.; Mallia, F.; Maury, A.; Maoz, D.; McCormick, J.; Monard, L. A. G.; Moorhouse, D.; Morgan, N.; Natusch, T.; Ofek, E. O.; Park, B.-G.; Pogge, R. W.; Polishook, D.; Santallo, R.; Shporer, A.; Spector, O.; Thornley, G.; Yee, J. C.; μFUN Collaboration; Kubiak, M.; Pietrzyński, G.; Soszyński, I.; Szewczyk, O.; Wyrzykowski, Ł.; Ulaczyk, K.; Poleski, R.; OGLE Collaboration; Abe, F.; Bennett, D. P.; Botzler, C. S.; Douchin, D.; Freeman, M.; Fukui, A.; Furusawa, K.; Hearnshaw, J. B.; Hosaka, S.; Itow, Y.; Kamiya, K.; Kilmartin, P. M.; Korpela, A.; Lin, W.; Ling, C. H.; Makita, S.; Masuda, K.; Matsubara, Y.; Miyake, N.; Muraki, Y.; Nagaya, M.; Nishimoto, K.; Ohnishi, K.; Okumura, T.; Perrott, Y. C.; Philpott, L.; Rattenbury, N.; Saito, To.; Sako, T.; Sullivan, D. J.; Sweatman, W. L.; Tristram, P. J.; von Seggern, E.; Yock, P. C. M.; MOA Collaboration; Albrow, M.; Batista, V.; Beaulieu, J. P.; Brillant, S.; Caldwell, J.; Calitz, J. J.; Cassan, A.; Cole, A.; Cook, K.; Coutures, C.; Dieters, S.; Dominis Prester, D.; Donatowicz, J.; Fouqué, P.; Hill, K.; Hoffman, M.; Jablonski, F.; Kane, S. R.; Kains, N.; Kubas, D.; Marquette, J.-B.; Martin, R.; Martioli, E.; Meintjes, P.; Menzies, J.; Pedretti, E.; Pollard, K.; Sahu, K. C.; Vinter, C.; Wambsganss, J.; Watson, R.; Williams, A.; Zub, M.; PLANET Collaboration; Allan, A.; Bode, M. F.; Bramich, D. M.; Burgdorf, M. J.; Clay, N.; Fraser, S.; Hawkins, E.; Horne, K.; Kerins, E.; Lister, T. A.; Mottram, C.; Saunders, E. S.; Snodgrass, C.; Steele, I. A.; Tsapras, Y.; RoboNet Collaboration; Jørgensen, U. G.; Anguita, T.; Bozza, V.; Calchi Novati, S.; Harpsøe, K.; Hinse, T. C.; Hundertmark, M.; Kjærgaard, P.; Liebig, C.; Mancini, L.; Masi, G.; Mathiasen, M.; Rahvar, S.; Ricci, D.; Scarpetta, G.; Southworth, J.; Surdej, J.; Thöne, C. C.; MiNDSTEp Consortium

    2010-09-01

    We present the first measurement of the planet frequency beyond the "snow line," for the planet-to-star mass-ratio interval -4.5 < log q < -2, corresponding to the range of ice giants to gas giants. We find {d^2 N{_pl}\\over d log q d log s} = (0.36± 0.15) dex^{-2} the mean mass ratio q = 5 × 10-4 with no discernible deviation from a flat (Öpik's law) distribution in log-projected separation s. The determination is based on a sample of six planets detected from intensive follow-up observations of high-magnification (A>200) microlensing events during 2005-2008. The sampled host stars have a typical mass M host ~ 0.5 M sun, and detection is sensitive to planets over a range of planet-star-projected separations (s -1 max R E, s max R E), where R E ~ 3.5 AU(M host/M sun)1/2 is the Einstein radius and s max ~ (q/10-4.3)1/3. This corresponds to deprojected separations roughly three times the "snow line." We show that the observations of these events have the properties of a "controlled experiment," which is what permits measurement of absolute planet frequency. High-magnification events are rare, but the survey-plus-follow-up high-magnification channel is very efficient: half of all high-mag events were successfully monitored and half of these yielded planet detections. The extremely high sensitivity of high-mag events leads to a policy of monitoring them as intensively as possible, independent of whether they show evidence of planets. This is what allows us to construct an unbiased sample. The planet frequency derived from microlensing is a factor 8 larger than the one derived from Doppler studies at factor ~25 smaller star-planet separations (i.e., periods 2-2000 days). However, this difference is basically consistent with the gradient derived from Doppler studies (when extrapolated well beyond the separations from which it is measured). This suggests a universal separation distribution across 2 dex in planet-star separation, 2 dex in mass ratio, and 0.3 dex in host

  9. FREQUENCY OF SOLAR-LIKE SYSTEMS AND OF ICE AND GAS GIANTS BEYOND THE SNOW LINE FROM HIGH-MAGNIFICATION MICROLENSING EVENTS IN 2005-2008

    SciTech Connect

    Gould, A.; Dong, Subo; Gaudi, B. S.; Han, C. E-mail: gaudi@astronomy.ohio-state.ed

    2010-09-10

    We present the first measurement of the planet frequency beyond the 'snow line', for the planet-to-star mass-ratio interval -4.5 < log q < -2, corresponding to the range of ice giants to gas giants. We find (d{sup 2}N{sub pl})/(d log q d log s) = (0.36{+-}0.15) dex{sup -2} at the mean mass ratio q = 5 x 10{sup -4} with no discernible deviation from a flat (Oepik's law) distribution in log-projected separation s. The determination is based on a sample of six planets detected from intensive follow-up observations of high-magnification (A>200) microlensing events during 2005-2008. The sampled host stars have a typical mass M{sub host} {approx} 0.5 M {sub sun}, and detection is sensitive to planets over a range of planet-star-projected separations (s {sup -1}{sub max} R {sub E}, s{sub max} R {sub E}), where R {sub E} {approx} 3.5 AU(M{sub host}/M{sub sun}){sup 1/2} is the Einstein radius and s {sub max} {approx} (q/10{sup -4.3}){sup 1/3}. This corresponds to deprojected separations roughly three times the 'snow line'. We show that the observations of these events have the properties of a 'controlled experiment', which is what permits measurement of absolute planet frequency. High-magnification events are rare, but the survey-plus-follow-up high-magnification channel is very efficient: half of all high-mag events were successfully monitored and half of these yielded planet detections. The extremely high sensitivity of high-mag events leads to a policy of monitoring them as intensively as possible, independent of whether they show evidence of planets. This is what allows us to construct an unbiased sample. The planet frequency derived from microlensing is a factor 8 larger than the one derived from Doppler studies at factor {approx}25 smaller star-planet separations (i.e., periods 2-2000 days). However, this difference is basically consistent with the gradient derived from Doppler studies (when extrapolated well beyond the separations from which it is measured). This

  10. Space-based infrared scanning sensor LOS determination and calibration using star observation

    NASA Astrophysics Data System (ADS)

    Chen, Jun; Xu, Zhan; An, Wei; Deng, Xin-Pu; Yang, Jun-Gang

    2015-10-01

    This paper provides a novel methodology for removing sensor bias from a space based infrared (IR) system (SBIRS) through the use of stars detected in the background field of the sensor. Space based IR system uses the LOS (line of sight) of target for target location. LOS determination and calibration is the key precondition of accurate location and tracking of targets in Space based IR system and the LOS calibration of scanning sensor is one of the difficulties. The subsequent changes of sensor bias are not been taking into account in the conventional LOS determination and calibration process. Based on the analysis of the imaging process of scanning sensor, a theoretical model based on the estimation of bias angles using star observation is proposed. By establishing the process model of the bias angles and the observation model of stars, using an extended Kalman filter (EKF) to estimate the bias angles, and then calibrating the sensor LOS. Time domain simulations results indicate that the proposed method has a high precision and smooth performance for sensor LOS determination and calibration. The timeliness and precision of target tracking process in the space based infrared (IR) tracking system could be met with the proposed algorithm.

  11. Quantifying Spatial and Seasonal Variability in Atmospheric Ammonia with In Situ and Space-Based Observations

    EPA Science Inventory

    Ammonia plays an important role in many biogeochemical processes, yet atmospheric mixing ratios arc not well known. Recently, methods have been developed for retrieving NH3 from space-based observations, but they have not been compared to in situ measurements. We have ...

  12. Antenna Autocalibration and Metrology Approach for the AFR/JPL Space-Based Radar

    NASA Technical Reports Server (NTRS)

    McWatters, Dalia; Michel, Thierry; Freedman, Adam; Cable, Vaughn

    2003-01-01

    The Air Force Research Laboratory (AFRL) and the Jet Propulsion Laboratory (JPL) are collaborating in the technology development for a space based radar (SBR) system that would feature a large aperture lightweight antenna for a joint mission later in this decade.

  13. Ground-Based and Space-Based Laser Beam Power Applications

    NASA Technical Reports Server (NTRS)

    Bozek, John M.

    1995-01-01

    A space power system based on laser beam power is sized to reduce mass, increase operational capabilities, and reduce complexity. The advantages of laser systems over solar-based systems are compared as a function of application. Power produced from the conversion of a laser beam that has been generated on the Earth's surface and beamed into cislunar space resulted in decreased round-trip time for Earth satellite electric propulsion tugs and a substantial landed mass savings for a lunar surface mission. The mass of a space-based laser system (generator in space and receiver near user) that beams down to an extraterrestrial airplane, orbiting spacecraft, surface outpost, or rover is calculated and compared to a solar system. In general, the advantage of low mass for these space-based laser systems is limited to high solar eclipse time missions at distances inside Jupiter. The power system mass is less in a continuously moving Mars rover or surface outpost using space-based laser technology than in a comparable solar-based power system, but only during dust storm conditions. Even at large distances for the Sun, the user-site portion of a space-based laser power system (e.g., the laser receiver component) is substantially less massive than a solar-based system with requisite on-board electrochemical energy storage.

  14. Nuclear reactor power as applied to a space-based radar mission

    NASA Technical Reports Server (NTRS)

    Jaffe, L.; Beatty, R.; Bhandari, P.; Chow, E.; Deininger, W.; Ewell, R.; Fujita, T.; Grossman, M.; Bloomfield, H.; Heller, J.

    1988-01-01

    A space-based radar mission and spacecraft are examined to determine system requirements for a 300 kWe space nuclear reactor power system. The spacecraft configuration and its orbit, launch vehicle, and propulsion are described. Mission profiles are addressed, and storage in assembly orbit is considered. Dynamics and attitude control and the problems of nuclear and thermal radiation are examined.

  15. INTERPRETATION OF STRONG SHORT-TERM CENTRAL PERTURBATIONS IN THE LIGHT CURVES OF MODERATE-MAGNIFICATION MICROLENSING EVENTS

    SciTech Connect

    Han, C.; Hwang, K.-H.; Kim, D.; Udalski, A.; Szymanski, M. K.; Kubiak, M.; Pietrzynski, G.; Soszynski, I.; Ulaczyk, K.; Abe, F.; Fukui, A.; Furusawa, K.; Itow, Y.; Monard, L. A. B.; McCormick, J.; Szewczyk, O.; Wyrzykowski, L.; Bond, I. A.; Botzler, C. S.; Hearnshaw, J. B.

    2009-11-10

    To improve the planet detection efficiency, current planetary microlensing experiments are focused on high-magnification events searching for planetary signals near the peak of lensing light curves. However, it is known that central perturbations can also be produced by binary companions and thus it is important to distinguish planetary signals from those induced by binary companions. In this paper, we analyze the light curves of microlensing events OGLE-2007-BLG-137/MOA-2007-BLG-091, OGLE-2007-BLG-355/MOA-2007-BLG-278, and MOA-2007-BLG-199/OGLE-2007-BLG-419, for all of which exhibit short-term perturbations near the peaks of the light curves. From detailed modeling of the light curves, we find that the perturbations of the events are caused by binary companions rather than planets. From a close examination of the light curves combined with the underlying physical geometry of the lens system obtained from modeling, we find that the short timescale caustic-crossing feature occurring at a low or a moderate base magnification with an additional secondary perturbation is a typical feature of binary-lens events and thus can be used for the discrimination between the binary and planetary interpretations.

  16. Interpretation of Strong Short-Term Central Perturbations in the Light Curves of Moderate-Magnification Microlensing Events

    NASA Astrophysics Data System (ADS)

    Han, C.; Hwang, K.-H.; Kim, D.; Udalski, A.; Abe, F.; Monard, L. A. B.; McCormick, J.; Szymański, M. K.; Kubiak, M.; Pietrzyński, G.; Soszyński, I.; Szewczyk, O.; Wyrzykowski, Ł.; Ulaczyk, K.; OGLE Collaboration; Bond, I. A.; Botzler, C. S.; Fukui, A.; Furusawa, K.; Hearnshaw, J. B.; Itow, Y.; Kamiya, K.; Kilmartin, P. M.; Korpela, A.; Lin, W.; Ling, C. H.; Masuda, K.; Matsubara, Y.; Miyake, N.; Muraki, Y.; Nagaya, M.; Ohnishi, K.; Tokumura, T.; Perrott, Y. C.; Rattenbury, N.; Saito, To.; Sako, T.; Skuljan, L.; Sullivan, D. S.; Sumi, T.; Sweatman, W. L.; Tristram, P. J.; Yock, P. C. M.; MOA Collaboration; Allen, W.; Christie, G. W.; De Poy, D. L.; Dong, S.; Gaudi, B. S.; Gould, A.; Lee, C.-U.; Natusch, T.; Park, B.-G.; Pogge, R. W.; μFUN Collaboration; Albrow, M. D.; Allan, A.; Batista, V.; Beaulieu, J. P.; Bennett, D. P.; Brillant, S.; Bode, M.; Bramich, D. M.; Burgdorf, M.; Caldwell, J. A. R.; Calitz, H.; Cassan, A.; Corrales, E.; Dieters, S.; Prester, D. D.; Dominik, M.; Donatowicz, J.; Fouque, P.; Greenhill, J.; Hill, K.; Hoffman, M.; Horne, K.; Jørgensen, U. G.; Kains, N.; Kubas, D.; Marquette, J. B.; Martin, R.; Meintjes, P.; Menzies, J.; Pollard, K. R.; Sahu, K. C.; Snodgrass, C.; Steele, I.; Street, R.; Tsapras, Y.; Wambsganss, J.; Williams, A.; Zub, M.; PLANET/RoboNet Collaboration

    2009-11-01

    To improve the planet detection efficiency, current planetary microlensing experiments are focused on high-magnification events searching for planetary signals near the peak of lensing light curves. However, it is known that central perturbations can also be produced by binary companions and thus it is important to distinguish planetary signals from those induced by binary companions. In this paper, we analyze the light curves of microlensing events OGLE-2007-BLG-137/MOA-2007-BLG-091, OGLE-2007-BLG-355/MOA-2007-BLG-278, and MOA-2007-BLG-199/OGLE-2007-BLG-419, for all of which exhibit short-term perturbations near the peaks of the light curves. From detailed modeling of the light curves, we find that the perturbations of the events are caused by binary companions rather than planets. From a close examination of the light curves combined with the underlying physical geometry of the lens system obtained from modeling, we find that the short timescale caustic-crossing feature occurring at a low or a moderate base magnification with an additional secondary perturbation is a typical feature of binary-lens events and thus can be used for the discrimination between the binary and planetary interpretations.

  17. Detecting cold H2 globules in the outer Galactic disc by microlensing towards the Maffei 1 elliptical

    NASA Astrophysics Data System (ADS)

    Fux, R.

    2005-02-01

    A candidate source of dark matter in spiral galaxies is cold molecular hydrogen globules with a condensed central core and a disc-like space distribution probably similar to that of neutral hydrogen. This paper shows that the H2 cores are sufficiently compact and massive to be detected by microlensing in the outer Galactic disc and that the Maffei 1 elliptical galaxy, at a distance of 3 Mpc and Galactic latitude b=-0.6°, offers an ideal target for such an experiment. The microlensing optical depth of H2 cores along the line of sight to this galaxy is estimated to τ˜ 0.7× 10-6 if most of the dark mass in the Milky Way resides in such cores, and the typical event timescale to ⪉ 1 day. Detection rates are computed both in the classical and pixel lensing approaches in the I- and K-bands, and for a representative selection of existing observing facilities. In the more efficient pixel lensing case, two 10-h observing runs, separated in time by at least several days, should yield of the order of 10 positive detections at the 5σ level using ground-based 8 m-class telescopes in the K-band or the Hubble Space Telescope ACS camera in the I-band, and the corresponding fraction of events with timescale measurable to an accuracy better than 50% amounts to about 9% and 4% respectively for these observing alternatives.

  18. Probing the atmosphere of the bulge G5III star OGLE-2002-BUL-069 by analysis of microlensed Hα line

    NASA Astrophysics Data System (ADS)

    Cassan, A.; Beaulieu, J. P.; Brillant, S.; Coutures, C.; Dominik, M.; Donatowicz, J.; Jørgensen, U. G.; Kubas, D.; Albrow, M. D.; Caldwell, J. A. R.; Fouqué, P.; Greenhill, J.; Hill, K.; Horne, K.; Kane, S.; Martin, R.; Menzies, J.; Pollard, K. R.; Sahu, K. C.; Vinter, C.; Wambsganss, J.; Watson, R.; Williams, A.; Fendt, C.; Hauschildt, P.; Heinmueller, J.; Marquette, J. B.; Thurl, C.

    2004-05-01

    We discuss high-resolution, time-resolved spectra of the caustic exit of the binary microlensing event OGLE 2002-BLG-069 obtained with UVES on the VLT. The source star is a G5III giant in the Galactic Bulge. During such events, the source star is highly magnified, and a strong differential magnification around the caustic resolves its surface. Using an appropriate model stellar atmosphere generated by the PHOENIX v2.6 code we obtain a model light curve for the caustic exit and compare it with a dense set of photometric observations obtained by the PLANET microlensing follow up network. We further compare predicted variations in the Hα equivalent width with those measured from our spectra. While the model and observations agree in the gross features, there are discrepancies suggesting shortcomings in the model, particularly for the Hα line core, where we have detected amplified emission from the stellar chromosphere after the source star's trailing limb exited the caustic. This achievement became possible by the provision of the very efficient OGLE-III Early Warning System, a network of small telescopes capable of nearly-continuous round-the-clock photometric monitoring, on-line data reduction, daily near-real-time modelling in order to predict caustic crossing parameters, and a fast and efficient response of a 8 m class telescope to a ``Target-of-Opportunity'' observation request. Based on observations made at ESO, 69.D-0261(A), 269.D-5042(A), 169.C-0510(A).

  19. The 1995 Pilot Campaign of PLANET: Searching for Microlensing Anomalies through Precise, Rapid, Round-the-Clock Monitoring

    NASA Astrophysics Data System (ADS)

    Albrow, M.; Beaulieu, J.-P.; Birch, P.; Caldwell, J. A. R.; Kane, S.; Martin, R.; Menzies, J.; Naber, R. M.; Pel, J.-W.; Pollard, K.; Sackett, P. D.; Sahu, K. C.; Vreeswijk, P.; Williams, A.; Zwaan, M. A.; PLANET Collaboration

    1998-12-01

    PLANET (the Probing Lensing Anomalies NETwork) is a worldwide collaboration of astronomers whose primary goal is to monitor microlensing events densely and precisely in order to detect and study anomalies that contain information about Galactic lenses and sources that would otherwise be unobtainable. The results of PLANET's highly successful first year of operation are presented here. Details of the observational setup, observing procedures, and data-reduction procedures used to track the progress in real time at the three participating observing sites in 1995 are discussed. The ability to follow several events simultaneously with a median sampling interval of 1.6 hr and a photometric precision of better than 0.10 mag even at I = 19 has been clearly demonstrated. During PLANET's 1995 pilot campaign, ten microlensing events were monitored, resulting in the most precise and densely-sampled light curves to date; the binary nature of one of these, MACHO 95-BLG-12, was recognized by PLANET on the mountain. Another event, OGLE 95-BLG-04, displayed chromaticity that may betray the presence of blending with unresolved stars projected onto the same resolution element. Although lasting only about a month, the campaign may allow constraints to be placed on the number of planets with mass ratios to the parent star of 0.01 or greater.

  20. Fabrication and alignment of large sapphire microlenses for use in electrically-injected GaN-based vertical-cavity laser applications

    NASA Astrophysics Data System (ADS)

    Farrell, Robert; Feezell, Daniel; Ishida, Masahiro; Newman, Scott; Cohen, Daniel; Nakamura, Shuji

    2007-03-01

    We have fabricated large sapphire microlenses for use in electrically-injected GaN-based vertical-cavity surface-emitting laser (VCSEL) applications. Thermally reflown photoresist microlenses are used as sacrificial masks for a BCl3/Cl2-based dry etch of sapphire. Sapphire microlenses with base diameters ranging from 10-250 μm and radii of curvature (ROC) ranging from 50-2000 μm are created by varying the initial thickness and diameter of the photoresist mask. Typical rms surface roughnesses of 1.5 å over 5.0 μm x 5.0 μm scan areas are achieved by utilizing specialized post-etch cleaning techniques. By coating the sapphire microlenses with dielectric distributed Bragg reflectors (DBRs) and aligning them to current apertures on InGaN-based devices on the opposite side of the sapphire wafer, we have demonstrated a viable technique for making high-reflectivity concave micromirrors for use in electrically-injected GaN-based VCSELs.

  1. Variability of GeV gamma-ray emission in QSO B0218+357 due to microlensing on intermediate size structures

    NASA Astrophysics Data System (ADS)

    Sitarek, J.; Bednarek, W.

    2016-06-01

    Strong gravitational lensing leads to an occurrence of multiple images, with different magnifications, of a lensed source. Those magnifications can in turn be modified by microlensing on smaller mass scales within the lens. Recently, measurements of the changes in the magnification ratio of the individual images have been proposed as a powerful tool for estimation of the size and velocity of the emission region in the lensed source. The changes of the magnification ratios in blazars PKS1830-211 and QSO B0218+357, if interpreted as caused by a microlensing on individual stars, put strong constraints on those two variables. These constraints are difficult to accommodate with the current models of gamma-ray emission in blazars. In this paper we study if similar changes in the magnification ratio can be caused by microlensing on intermediate size structures in the lensing galaxy. We investigate in details three classes of possible lenses: globular clusters (GCs), open clusters (OCs) and giant molecular clouds (GMCs). We apply this scenario to the case of QSO B0218+357. Our numerical simulations show that changes in magnifications with similar time-scales can be obtained for relativistically moving emission regions with sizes up to 0.01 pc in the case of microlensing on the cores of GCs or clumps in GMCs. From the density of such structures in spiral galaxies we estimate however that lensing in GMCs would be more common.

  2. Chemical evolution of the Galactic bulge as traced by microlensed dwarf and subgiant stars. IV. Two bulge populations

    NASA Astrophysics Data System (ADS)

    Bensby, T.; Adén, D.; Meléndez, J.; Gould, A.; Feltzing, S.; Asplund, M.; Johnson, J. A.; Lucatello, S.; Yee, J. C.; Ramírez, I.; Cohen, J. G.; Thompson, I.; Bond, I. A.; Gal-Yam, A.; Han, C.; Sumi, T.; Suzuki, D.; Wada, K.; Miyake, N.; Furusawa, K.; Ohmori, K.; Saito, To.; Tristram, P.; Bennett, D.

    2011-09-01

    Based on high-resolution (R ≈ 42 000 to 48 000) and high signal-to-noise (S/N ≈ 50 to 150) spectra obtained with UVES/VLT, we present detailed elemental abundances (O, Na, Mg, Al, Si, Ca, Ti, Cr, Fe, Ni, Zn, Y, and Ba) and stellar ages for 12 new microlensed dwarf and subgiant stars in the Galactic bulge. Including previous microlensing events, the sample of homogeneously analysed bulge dwarfs has now grown to 26. The analysis is based on equivalent width measurements and standard 1-D LTE MARCS model stellar atmospheres. We also present NLTE Li abundances based on line synthesis of the 7Li line at 670.8 nm. The results from the 26 microlensed dwarf and subgiant stars show that the bulge metallicity distribution (MDF) is double-peaked; one peak at [Fe/H] ≈ -0.6 and one at [Fe/H] ≈ + 0.3, and with a dearth of stars around solar metallicity. This is in contrast to the MDF derived from red giants in Baade's window, which peaks at this exact value. A simple significance test shows that it is extremely unlikely to have such a gap in the microlensed dwarf star MDF if the dwarf stars are drawn from the giant star MDF. To resolve this issue we discuss several possibilities, but we can not settle on a conclusive solution for the observed differences. We further find that the metal-poor bulge dwarf stars arepredominantly old with ages greater than 10 Gyr, while the metal-rich bulge dwarf stars show a wide range of ages. The metal-poor bulge sample is very similar to the Galactic thick disk in terms of average metallicity, elemental abundance trends, and stellar ages. Speculatively, the metal-rich bulge population might be the manifestation of the inner thin disk. If so, the two bulge populations could support the recent findings, based on kinematics, that there are no signatures of a classical bulge and that the Milky Way is a pure-disk galaxy. Also, recent claims of a flat IMF in the bulge based on the MDF of giant stars may have to be revised based on the MDF and

  3. X-Ray and Optical Microlensing in the Lensed Quasar PG 1115+080

    NASA Astrophysics Data System (ADS)

    Morgan, Christopher W.; Kochanek, Christopher. S.; Dai, Xinyu; Morgan, Nicholas D.; Falco, Emilio E.

    2008-12-01

    We analyzed the microlensing of the X-ray and optical emission of the lensed quasar PG 1115+080. We find that the effective radius of the X-ray emission is 1.3+ 1.1-0.5 dex smaller than that of the optical emission. Viewed as a thin disk observed at inclination angle i, the optical accretion disk has a scale length, defined by the point where the disk temperature matches the rest-frame energy of the monitoring band (kT = hc/λrest with λrest = 0.3 μm), of log{(rs, opt/cm)[cos(i)/0.5]½} = 16.6 +/- 0.4. The X-ray emission region (1.4-21.8 keV in the rest frame) has an effective half-light radius of log (r1/2,X/cm) = 15.6+ 0.6-0.9. Given an estimated black hole mass of 1.2 × 109 M⊙, corresponding to a gravitational radius of log (rg/cm) = 14.3, the X-ray emission is generated near the inner edge of the disk, while the optical emission comes from scales slightly larger than those expected for an Eddington-limited thin disk. We find a weak trend supporting models with low stellar mass fractions near the lensed images, in mild contradiction to inferences from the stellar velocity dispersion and the time delays. Based on observations obtained with the Small and Moderate Aperture Research Telescope System (SMARTS) 1.3 m, which is operated by the SMARTS Consortium; the Apache Point Observatory 3.5 meter telescope, which is owned and operated by the Astrophysical Research Consortium; the WIYN Observatory, which is owned and operated by the University of Wisconsin, Indiana University, Yale University, and the National Optical Astronomy Observatory (NOAO); the 6.5 m Magellan Baade telescope, which is a collaboration between the Observatories of the Carnegie Institution of Washington (OCIW), the University of Arizona, Harvard University, the University of Michigan, and the Massachusetts Institute of Technology; and observations made with the NASA/ESA Hubble Space Telescope for program HST-GO-9744 of the Space Telescope Science Institute, which is operated by the

  4. Wide-Field Infrared Survey Telescope (WFIRST) Interim Report

    NASA Technical Reports Server (NTRS)

    Green, J.; Schechter, P.; Baltay, C.; Bean, R.; Bennett, D.; Brown, R.; Conselice, C.; Donahue, M.; Gaudi, S.; Lauer, T.; Perlmutter, S.; Rauscher, B.; Rhodes, J.; Roellig, T.; Stern, D.; Sumi, T.; Gerhels, N.; Sambruna, R.; Barry, R. K.; Content, D.; Grady, K; Jackson, C.; Kruk, J.; Melton, M.; Rioux, N.

    2011-01-01

    The New Worlds, New Horizons (NWNH) in Astronomy and Astrophysics 2010 Decadal Survey prioritized the community consensus for ground-based and space-based observatories. Recognizing that many of the community s key questions could be answered with a wide-field infrared survey telescope in space, and that the decade would be one of budget austerity, WFIRST was top ranked in the large space mission category. In addition to the powerful new science that could be accomplished with a wide-field infrared telescope, the WFIRST mission was determined to be both technologically ready and only a small fraction of the cost of previous flagship missions, such as HST or JWST. In response to the top ranking by the community, NASA formed the WFIRST Science Definition Team (SDT) and Project Office. The SDT was charged with fleshing out the NWNH scientific requirements to a greater level of detail. NWNH evaluated the risk and cost of the JDEM-Omega mission design, as submitted by NASA, and stated that it should serve as the basis for the WFIRST mission. The SDT and Project Office were charged with developing a mission optimized for achieving the science goals laid out by the NWNH re-port. The SDT and Project Office opted to use the JDEM-Omega hardware configuration as an initial start-ing point for the hardware implementation. JDEM-Omega and WFIRST both have an infrared imager with a filter wheel, as well as counter-dispersed moderate resolution spectrometers. The primary advantage of space observations is being above the Earth's atmosphere, which absorbs, scatters, warps and emits light. Observing from above the atmosphere enables WFIRST to obtain precision infrared measurements of the shapes of galaxies for weak lensing, infrared light-curves of supernovae and exoplanet microlensing events with low systematic errors, and infrared measurements of the H hydrogen line to be cleanly detected in the 1

  5. Space-based solar power conversion and delivery systems study. Volume 3: Economic analysis of space-based solar power systems

    NASA Technical Reports Server (NTRS)

    Hazelrigg, G. A., Jr.

    1976-01-01

    A variety of economic and programmatic issues are discussed concerning the development and deployment of a fleet of space-based solar power satellites (SSPS). The costs, uncertainties and risks associated with the current photovoltaic SSPS configuration, and with issues affecting the development of an economically viable SSPS development program are analyzed. The desirability of a low earth orbit (LEO) demonstration satellite and a geosynchronous (GEO) pilot satellite is examined and critical technology areas are identified. In addition, a preliminary examination of utility interface issues is reported. The main focus of the effort reported is the development of SSPS unit production, and operation and maintenance cost models suitable for incorporation into a risk assessment (Monte Carlo) model (RAM). It is shown that the key technology area deals with the productivity of man in space, not, as might be expected, with some hardware component technology.

  6. The Platform Design of Space-based Optical Observations of Space Debris

    NASA Astrophysics Data System (ADS)

    Chen, B. R.; Xiong, J. N.

    2016-03-01

    The basic design method of the platform for the space-based optical observations of space debris is introduced. The observation schemes of GEO (geosynchronous equatorial orbit) and LEO (low Earth orbit) debris are given respectively, including orbital parameters of platforms and pointing of telescopes, etc. Debris studied here is all from foreign catalog. According to the real orbit of space debris, the observational results of different schemes are simulated. By studying single platform, the optimal observing altitude for GEO debris and the optimal telescope's deflection angles at different altitudes for LEO debris are given. According to these, multi-platforms observation networks are designed. By analyzing the advantages and disadvantages of each scheme, it can provide reference for the application of space-based optical debris observation.

  7. Comparisons between Ground-Based Photometry and Space-Based Measurements of the Total Solar Irradiance

    NASA Astrophysics Data System (ADS)

    Chapman, G.; Cookson, A.; Dobias, J.; Walton, S.

    2005-05-01

    We will review the usefulness of ground-based full-disk photometry in conjunction with space-based measurements of the Total Solar Irradiance (TSI). It is known that sunspots and faculae cause changes in the TSI. These features need to be modeled using ground-based photometry and their effects removed in order to search for possible other causes of TSI variation. Work to date has shown that approximately 94% of the variance in TSI can be explained by sunspots and faculae/network. Since ground-based photometry is carried out daily, it can help identify anomalies in space-based TSI measurements. Finally, ground-based photometry can help in tying together TSI measurements from different spacecraft that have different native irradiance scales. This work has been partially supported by grants from NASA and NSF.

  8. Space Based Observations of Coronal Cavities in Conjunction with the Total Solar Eclipse of July 2010

    NASA Technical Reports Server (NTRS)

    Kucera, T. A.; Berger, T. E.; Druckmuller, M.; Dietzel, M.; Gibson, S. E.; Habbal, S. R.; Morgan, H.; Reeves, K. K.; Schmit, D. J.; Seaton, D. B.

    2010-01-01

    In conjunction with the total solar eclipse on July 11, 2010 we coordinated a campaign between ground and space based observations. Our specific goal was to augment the ground based measurement of corona) prominence cavity temperatures made using iron lines in the IR (Habbal et al. 2010 ApJ 719 1362) with measurements performed by space based instruments. Included in the campaign were Hinode/EIS, XRT and SOT, PROBA2/SWAP, SDO/AIA, SOHO/CDS and STEREO/SECCHI/EUVI, in addition to the ground based IR measurements. We plan to use a combination of line ratio and forward modeling techniques to investigate the density and temperature structure of the cavities at that time.

  9. Enabling technologies for transition to utilization of space-based resources and operations

    NASA Technical Reports Server (NTRS)

    Sadin, S. R.; Litty, J. D.

    1985-01-01

    This article explores a potential scenario for the further development of space infrastructure resources and operations management. It is a scenario that transitions from the current ground-based system to an architecture that is predominantly space-based by exploiting key mission systems in an operational support role. If this view is accurate, an examination of the range of potential infrastructure elements and how they might interact in a maximally productive space-based operations complex is needed, innovative technologies beyond the current Shuttle and Space Station legacy need to be identified, and research programs pursued. Development of technologies within the areas of telerobotics, machine autonomy, human autonomy, in-space manufacturing and construction, propulsion and energy is discussed.

  10. Space Based Observations of Coronal Cavities in Conjunction with the Total Solar Eclipse of July 2010

    NASA Astrophysics Data System (ADS)

    Kucera, T. A.; Berger, T. E.; Boerner, P.; Dietzel, M.; Druckmuller, M.; Gibson, S. E.; Habbal, S. R.; Morgan, H.; Reeves, K. K.; Schmit, D. J.; Seaton, D. B.

    2010-12-01

    In conjunction with the total solar eclipse on July 11, 2010 we coordinated a campaign between ground and space based observations. Our specific goal was to augment the ground based measurement of coronal prominence cavity temperatures made using iron lines in the IR (Habbal et al. 2010 ApJ 719 1362) with measurements performed by space based instruments. Included in the campaign were Hinode/EIS, XRT and SOT, PROBA2/SWAP, SDO/AIA, SOHO/CDS and STEREO/SECCHI/EUVI, in addition to the ground based IR measurements. We plan to use a combination of line ratio and forward modeling techniques to investigate the density and temperature structure of the cavities at that time.

  11. Ship Detection Using High Resolution Satellite Imagery and Space-Based AIS

    NASA Astrophysics Data System (ADS)

    Hannevik, Tonje Nanette; Skauen, Andreas N.; Olsen, R. B.

    2013-03-01

    This paper presents a trial carried out in the Malangen area close to Tromsø city in the north of Norway in September 2010. High resolution Synthetic Aperture Radar (SAR) images from RADARSAT-2 were used to analyse how SAR images and cooperative reporting can be combined. Data from the Automatic Identification System, both land-based and space-based, have been used to identify detected vessels in the SAR images. The paper presents results of ship detection in high resolution RADARSAT-2 Standard Quad-Pol images, and how these results together with land-based and space-based AIS can be used. Some examples of tracking of vessels are also shown.

  12. Measurements of strain at plate boundaries using space based geodetic techniques

    NASA Technical Reports Server (NTRS)

    Robaudo, Stefano; Harrison, Christopher G. A.

    1993-01-01

    We have used the space based geodetic techniques of Satellite Laser Ranging (SLR) and VLBI to study strain along subduction and transform plate boundaries and have interpreted the results using a simple elastic dislocation model. Six stations located behind island arcs were analyzed as representative of subduction zones while 13 sites located on either side of the San Andreas fault were used for the transcurrent zones. The length deformation scale was then calculated for both tectonic margins by fitting the relative strain to an exponentially decreasing function of distance from the plate boundary. Results show that space-based data for the transcurrent boundary along the San Andreas fault help to define better the deformation length scale in the area while fitting nicely the elastic half-space earth model. For subduction type bonndaries the analysis indicates that there is no single scale length which uniquely describes the deformation. This is mainly due to the difference in subduction characteristics for the different areas.

  13. Nuclear norm-regularized k-space-based parallel imaging reconstruction

    NASA Astrophysics Data System (ADS)

    Xu, Lin; Liu, Xiaoyun

    2014-04-01

    Parallel imaging reconstruction suffers from serious noise amplification at high accelerations that can be alleviated with regularization by imposing some prior information or constraints on image. Nevertheless, point-wise interpolation of missing k-space data restricts the use of prior information in k-space-based parallel imaging reconstructions like generalized auto-calibrating partial acquisitions (GRAPPA). In this study, a regularized k-space based parallel imaging reconstruction is presented. We first formulate the reconstruction of missing data within a patch as a linear inverse problem. Instead of exploiting prior information on image or its transform domain, the proposed method exploits the rank deficiency of structured matrix consisting of vectorized patches form entire k-space, which leads to a nuclear norm-regularized problem solved by the numeric algorithms iteratively. Brain imaging studies are performed, demonstrating that the proposed method is capable of mitigating noise at high accelerations in GRAPPA reconstruction.

  14. Invited article: advanced drag-free concepts for future space-based interferometers: acceleration noise performance.

    PubMed

    Gerardi, D; Allen, G; Conklin, J W; Sun, K-X; DeBra, D; Buchman, S; Gath, P; Fichter, W; Byer, R L; Johann, U

    2014-01-01

    Future drag-free missions for space-based experiments in gravitational physics require a Gravitational Reference Sensor with extremely demanding sensing and disturbance reduction requirements. A configuration with two cubical sensors is the current baseline for the Laser Interferometer Space Antenna (LISA) and has reached a high level of maturity. Nevertheless, several promising concepts have been proposed with potential applications beyond LISA and are currently investigated at HEPL, Stanford, and EADS Astrium, Germany. The general motivation is to exploit the possibility of achieving improved disturbance reduction, and ultimately understand how low acceleration noise can be pushed with a realistic design for future mission. In this paper, we discuss disturbance reduction requirements for LISA and beyond, describe four different payload concepts, compare expected strain sensitivities in the "low-frequency" region of the frequency spectrum, dominated by acceleration noise, and ultimately discuss advantages and disadvantages of each of those concepts in achieving disturbance reduction for space-based detectors beyond LISA. PMID:24517738

  15. CIM in space: Corporate Information Management (CIM) implications for space-based information systems

    NASA Astrophysics Data System (ADS)

    Mock, Richard V.

    1993-04-01

    This paper describes the DOD corporate information management (CIM) initiative, space forces, and space-based information systems used by the DOD. It then describes implications of CIM in the space industry. CIM is defined as a philosophy which has management and technical components. The CIM management philosophy includes concepts for standardization, system engineering, and the use of commercial systems and technology. The technical component uses the information engineering discipline to improve business processes. The paper provides examples of the CIM management philosophy in operation as well as opportunities for CIM application. Information engineering is described as it applies to space-based information systems. The appendix includes an illustrative example of the integrated definition (IDEF) methodology applied to the tactical warning/attack assessment mission.

  16. Space-Based Gravitational-Wave Observations as Tools for Testing General Relativity

    NASA Technical Reports Server (NTRS)

    Will, Clifford M.

    2004-01-01

    We continued a project, to analyse the ways in which detection and study of gravitational waves could provide quantitative tests of general relativity, with particular emphasis on waves that would be detectable by space-based observatories, such as LISA. This work had three foci: 1) Tests of scalar-tensor theories of gravity that, could be done by analyzing gravitational waves from neutron stars inspiralling into massive black holes, as detectable by LISA; 2) Study of alternative theories of gravity in which the graviton could be massive, and of how gravitational-wave observations by space-based detectors, solar-system tests, and cosmological observations could constrain such theories; and 3) Study of gravitational-radiation back reaction of particles orbiting black holes in general relativity, with emphasis on the effects of spin.

  17. Space-based application of the CAN laser to LIDAR and orbital debris remediation

    NASA Astrophysics Data System (ADS)

    Quinn, M. N.; Jukna, V.; Ebisuzaki, T.; Dicaire, I.; Soulard, R.; Summerer, L.; Couairon, A.; Mourou, G.

    2015-10-01

    Development of pulsed lasers for space-based science missions entail many additional challenges compared to terrestrial experiments. For systems requiring short pulses ≪1 ns with energies >100 mJ and fast repetition rates >10 kHz there are currently few if no laser architectures capable of operating with high electrical efficiency >20% and have good system stability. The emergence of a mulit-channel fiber-based Coherent-Amplifying-Network or CAN laser potentially enables such capability for space based missions. Here in this article we present an analysis of two such missions scaling up in pulse energy from ≈100 mJ for a supercontinuum LIDAR application utilising atmospheric filamentation to the higher energy demands needed for space debris remediation requiring ≈10 J pulses. This scalability of the CAN laser provides pathways for development of the core science and technology where many new novel space applications can be made possible.

  18. Supplemental information on a conceptual design of a space-based multimegawatt MHD power system

    SciTech Connect

    Pierce, B.L.; Holman, R.R.; Lance, J.R.

    1988-02-01

    The objective of this project is to perform a feasibility assessment of space-based multimegawatt (MMW) magnetohydrodynamic (MHD) power systems for Strategic Defense Initiative Organization (SDIO) mission applications and to resolve technical uncertainties that may impact their future implementation. The ultimate goal of the SDIO is to provide security for the United States and Its allies. The near term objective of the SDIO is to conduct research on those technologies for defensive systems that might be capable of intercepting ballistic missiles after launch and preventing them from hitting their targets. System concepts currently being considered for space-based weapons applications will, if implemented, require specially tailored power systems. These power systems may possess characteristics and specifications lying considerably outside the design range of conventional devices. Their development may require major advances in existing technology and the accelerated development of entirely new approaches.

  19. The space exploration initiative. Operational efficiency panel space-basing technology requirements

    NASA Technical Reports Server (NTRS)

    Pena, Luis R.

    1991-01-01

    The topics covered include the following: (1) space basing technology requirements sources; (2) orbit transfer vehicle (OTV) processing heritage; (3) ground processing progression to space processing; (4) technology requirements for space based OTV servicing and maintenance; (5) design and development schedule for OTV's and OTV accommodations/ support hardware; (6) cryogenic technology test program development; (7) cryogenic propellant transfer, storage, and reliquefaction management summary; (8) propellant transfer technology analysis and ground testing; (8) OTV propellant storage depot development critical scaling relationships; (9) flight experiment options; (10) OTV maintenance; (11) automated fault detection/ isolation and system checkout summary; (12) engine replacement; (13) alternative docking operation; (14) OTV/payload integration; and (15) technology criticality and capability assessment. This document is presented in viewgraph form.

  20. Issues, concerns, and initial implementation results for space based telerobotic control

    NASA Technical Reports Server (NTRS)

    Lawrence, D. A.; Chapel, J. D.; Depkovich, T. M.

    1987-01-01

    Telerobotic control for space based assembly and servicing tasks presents many problems in system design. Traditional force reflection teleoperation schemes are not well suited to this application, and the approaches to compliance control via computer algorithms have yet to see significant testing and comparison. These observations are discussed in detail, as well as the concerns they raise for imminent design and testing of space robotic systems. As an example of the detailed technical work yet to be done before such systems can be specified, a particular approach to providing manipulator compliance is examined experimentally and through modeling and analysis. This yields some initial insight into the limitations and design trade-offs for this class of manipulator control schemes. Implications of this investigation for space based telerobots are discussed in detail.

  1. Space-based laser active imaging simulation system based on HLA

    NASA Astrophysics Data System (ADS)

    Han, Yi; Sun, Huayan; Li, Yingchun

    2013-09-01

    This paper adopts the High Level Architecture to develop the space-based laser active imaging distribution simulation software system, and designs the system framework which contains three-step workflow including modeling, experimental and analysis. The paper puts forward the general needs of the simulation system first, then builds the simulation system architecture based on HLA and constructs 7 simulation federal members. The simulation system has the primary functions of space target scattering characteristic analysis, imaging simulation, image processing and target recognition, and system performance analysis and so on, and can support the whole simulation process. The results show that the distribution simulation system can meet the technical requirements of the space-based laser imaging simulation.

  2. Recent Ground-Based Photometry Compared with Space-Based TSI

    NASA Astrophysics Data System (ADS)

    Chapman, G. A.; Cookson, A.; Preminger, D.

    2010-12-01

    Solar activity continues at low levels with occasional modest increases. We will compare indices from ground-based photometry with variations in Total Solar Irradiance (TSI) from SORCE/TIM as well as other space-based instruments. During the solar minimum of 2008-2009 regressions of solar indices with SORCE/TIM gave a quiet sun TSI of 1360.62 +/- 0.04 W/m^2. This work has been partly supported by NSF grant ATM-0848518.

  3. Unmanned, space-based, reusable orbital transfer vehicle, DARVES. Volume 1: Trade analysis and design

    NASA Technical Reports Server (NTRS)

    1988-01-01

    The design of an unmanned, space-based, reusable Orbital Transfer Vehicle (OTV) is presented. This OTV will be utilized for the delivery and retrieval of satellites from geosynchronous Earth orbit (GEO) in conjunction with a space station assumed to be in existence in low Earth orbit (LEO). The trade analysis used to determine the vehicle design is presented, and from this study a vehicle definition is given.

  4. Space-to-Space Based Relative Motion Estimation Using Direct Relative Orbit Parameters

    NASA Astrophysics Data System (ADS)

    Bennett, T.; Schaub, H.

    There has been an increasing interest in space-based space situational awareness around satellite assets and the tracking of orbital debris. Of particular interest is the space-based tracking of objects near critical circular orbit regimes, for example near the Geostationary belt or the International Space Station. Relative orbit descriptions such as the Clohessy-Wiltshire equations describe the motion using time-varying Cartesian or curvilinear coordinates. Orbit element differences describe the unperturbed motion using constant variations of inertial orbit elements. With perturbations these only vary slowly, but can be challenging to estimate. Linearized Relative Orbit Elements (LROEs) employ invariants of the linearized relative motion, are thus constant for the unperturbed linear case, and share the benefit of the CW equations in that they directly related to space-based relative motion measurements. The variational LROE equations enable the relative orbit to be directly propagated including perturbation forces. Utilization of the invariant-inspired relative motion parameters exhibits exciting applications in relative motion sensing and control. Many methods of relative motion estimation involve the direct estimation of time-evolving position and velocity variables. Developed is an angles-only relative orbit Extended Kalman filter (EKF) navigation approach that directly estimates these nominally constant LROEs. The proposed variational equations and filtering scheme enables direct estimation of geometric parameters with clear geometric insight. Preliminary numerical simulation results demonstrate the relative orbit insight gained and speed of convergence. EKF implementations often exhibit significant sensitivity to initial conditions, however, initial results show that the LROE filter converges within fractions of an orbit with initialization errors that exceed 100 percent. The manuscript presents the invariants of motion, develops the variational equations for

  5. Characterization of exoplanet atmospheres using future space-based infrared telescopes: challenges in detecting biomarkers

    NASA Astrophysics Data System (ADS)

    Enya, Keigo

    2014-01-01

    Characterization of exoplanet atmospheres with space-based infrared telescopes is important to detect biomarkers. A promising method is temporary differential observation. For this method, designs of a wideband infrared spectral disperser are presented. A design using a CdTe prism simultaneously covers λ=1-30 μm. Designing binary pupil masks for segmented pupils to be used in spatially resolved observations are also shown for another observational method.

  6. Resolved rate and torque control schemes for large scale space based kinematically redundant manipulators

    NASA Technical Reports Server (NTRS)

    Bailey, Robert W.; Quiocho, Leslie J.

    1991-01-01

    Resolved rate control of kinematically redundant ground based manipulators is a challenging problem. The structural, actuator, and control loop frequency characteristics of industrial grade robots generally allow operation with resolved rate control; a rate command is achievable with good accuracy. However, space based manipulators are different, typically have less structural stiffness, more motor and joint friction, and lower control loop cycle frequencies. These undesirable characteristics present a considerable Point of Resolution (POR) control problem for space based, kinematically redundant manipulators for the following reason: a kinematically redundant manipulator requires an arbitrary constraint to solve for the joint rate commands. A space manipulator will not respond to joint rate commands because of these characteristics. A space based manipulator simulation, including free end rigid body dynamics, motor dynamics, motor striction/friction, gearbox backlash, joint striction/friction, and Space Station Remote Manipulator System type configuration parameters, is used to evaluate the performance of a documented resolved rate control law. Alternate schemes which include torque control are also evaluated.

  7. Cyber Security Threats to Safety-Critical, Space-Based Infrastructures

    NASA Astrophysics Data System (ADS)

    Johnson, C. W.; Atencia Yepez, A.

    2012-01-01

    Space-based systems play an important role within national critical infrastructures. They are being integrated into advanced air-traffic management applications, rail signalling systems, energy distribution software etc. Unfortunately, the end users of communications, location sensing and timing applications often fail to understand that these infrastructures are vulnerable to a wide range of security threats. The following pages focus on concerns associated with potential cyber-attacks. These are important because future attacks may invalidate many of the safety assumptions that support the provision of critical space-based services. These safety assumptions are based on standard forms of hazard analysis that ignore cyber-security considerations This is a significant limitation when, for instance, security attacks can simultaneously exploit multiple vulnerabilities in a manner that would never occur without a deliberate enemy seeking to damage space based systems and ground infrastructures. We address this concern through the development of a combined safety and security risk assessment methodology. The aim is to identify attack scenarios that justify the allocation of additional design resources so that safety barriers can be strengthened to increase our resilience against security threats.

  8. Performance optimization for space-based sensors: simulation and modelling at Fraunhofer IOSB

    NASA Astrophysics Data System (ADS)

    Schweitzer, Caroline; Stein, Karin

    2014-10-01

    The prediction of the effectiveness of a space-based sensor for its designated application in space (e.g. special earth surface observations or missile detection) can help to reduce the expenses, especially during the phases of mission planning and instrumentation. In order to optimize the performance of such systems we simulate and analyse the entire operational scenario, including: - optional waveband - various orbit heights and viewing angles - system design characteristics, e. g. pixel size and filter transmission - atmospheric effects, e. g. different cloud types, climate zones and seasons In the following, an evaluation of the appropriate infrared (IR) waveband for the designated sensor application is given. The simulation environment is also capable of simulating moving objects like aircraft or missiles. Therefore, the spectral signature of the object/missile as well as its track along a flight path is implemented. The resulting video sequence is then analysed by a tracking algorithm and an estimation of the effectiveness of the sensor system can be simulated. This paper summarizes the work carried out at Fraunhofer IOSB in the field of simulation and modelling for the performance optimization of space based sensors. The paper is structured as follows: First, an overview of the applied simulation and modelling software is given. Then, the capability of those tools is illustrated by means of a hypothetical threat scenario for space-based early warning (launch of a long-range ballistic missile (BM)).

  9. A preliminary structural analysis of space-base living quarters modules to verify a weight-estimating technique

    NASA Technical Reports Server (NTRS)

    Grissom, D. S.; Schneider, W. C.

    1971-01-01

    The determination of a base line (minimum weight) design for the primary structure of the living quarters modules in an earth-orbiting space base was investigated. Although the design is preliminary in nature, the supporting analysis is sufficiently thorough to provide a reasonably accurate weight estimate of the major components that are considered to comprise the structural weight of the space base.

  10. 76 FR 22924 - Re-Establishment of the National Space-Based Positioning, Navigation, and Timing (PNT) Advisory...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-04-25

    ... SPACE ADMINISTRATION Re-Establishment of the National Space-Based Positioning, Navigation, and Timing (PNT) Advisory Board AGENCY: National Aeronautics and Space Administration (NASA). ACTION: Notice of...'s 2004 U.S. Space-Based PNT Policy established on December 8, 2004, and continuing and...

  11. EXTREME MAGNIFICATION MICROLENSING EVENT OGLE-2008-BLG-279: STRONG LIMITS ON PLANETARY COMPANIONS TO THE LENS STAR

    SciTech Connect

    Yee, J. C.; Dong, Subo; Kozlowski, S. E-mail: jyee@astronomy.ohio-state.ed

    2009-10-01

    We analyze the extreme high-magnification microlensing event OGLE-2008-BLG-279, which peaked at a maximum magnification of A approx 1600 on 2008 May 30. The peak of this event exhibits both finite-source effects and terrestrial parallax, from which we determine the mass of the lens, M{sub l} = 0.64 +- 0.10 M {sub sun}, and its distance, D{sub l} = 4.0 +- 0.6 kpc. We rule out Jupiter-mass planetary companions to the lens star for projected separations in the range 0.5-20 AU. More generally, we find that this event was sensitive to planets with masses as small as 0.2 M{sub +}{approx_equal}2 M{sub Mars} with projected separations near the Einstein ring (approx3 AU).

  12. An X-Ray Microlensing Test of the Au-Scale Central Structure of the Quadruple Quasar 2237+0305

    NASA Astrophysics Data System (ADS)

    Mineshige, Shin

    2011-09-01

    We propose Chandra observations of the gravitationally lensed quasar Q2237+0305 during a microlensing event to reveal its AU scale central structure. The quasar being monitored from the ground regularly to ascertain the onset of the event. As it occurs, we will measure X-ray spectral variations with Chandra and compare with those taken before and after the event. Since a small region of the quasar accretion disk is strongly magnified during the event, we will be able to limit the mass contained on scales of several AUs and to probe the physical properties of X-ray emitting gas in the vicinity of the black hole. Together with ground-based telescope, we can resolve the quasar emission regions at multiple wavelength. This provides a critical test of quasar accretion disk theories.

  13. An X-Ray Microlensing Test of the Au-Scale Central Structure of the Quadruple Quasar 2237+0305

    NASA Astrophysics Data System (ADS)

    Mineshige, Shin

    2008-09-01

    We propose Chandra observations of the gravitationally lensed quasar Q2237+0305 during a microlensing event to reveal its AU scale central structure. The quasar is being monitored from the ground regularly to ascertain the onset of the event. As it occurs, we will measure X-ray spectral variations with Chandra and compare with those taken before and after the event. Since a small region of the quasar accretion disk is strongly magnified during the event, we will be able to limit the mass contained on scales of several AUs and to probe the physical properties of X-ray emitting gas in the vicinity of the black hole. Together with ground-based telescopes, we can resolve the quasar emission regions at multiple wavelengths. This provide a critical test of quasar accretion disk theories.

  14. The Spitzer Microlensing Program as a Probe for Globular Cluster Planets: Analysis of OGLE-2015-BLG-0448

    NASA Astrophysics Data System (ADS)

    Poleski, Radosław; Zhu, Wei; Christie, Grant W.; Udalski, Andrzej; Gould, Andrew; Bachelet, Etienne; Skottfelt, Jesper; Calchi Novati, Sebastiano; Szymański, M. K.; Soszyński, I.; Pietrzyński, G.; Wyrzykowski, Ł.; Ulaczyk, K.; Pietrukowicz, P.; Kozłowski, Szymon; Skowron, J.; Mróz, P.; Pawlak, M.; OGLE group; Beichman, C.; Bryden, G.; Carey, S.; Fausnaugh, M.; Gaudi, B. S.; Henderson, C. B.; Pogge, R. W.; Shvartzvald, Y.; Wibking, B.; Yee, J. C.; Spitzer team; Beatty, T. G.; Eastman, J. D.; Drummond, J.; Friedmann, M.; Henderson, M.; Johnson, J. A.; Kaspi, S.; Maoz, D.; McCormick, J.; McCrady, N.; Natusch, T.; Ngan, H.; Porritt, I.; Relles, H. M.; Sliski, D. H.; Tan, T.-G.; Wittenmyer, R. A.; Wright, J. T.; μFUN group; Street, R. A.; Tsapras, Y.; Bramich, D. M.; Horne, K.; Snodgrass, C.; Steele, I. A.; Menzies, J.; Figuera Jaimes, R.; Wambsganss, J.; Schmidt, R.; Cassan, A.; Ranc, C.; Mao, S.; project, RoboNet; Bozza, V.; Dominik, M.; Hundertmark, M. P. G.; Jørgensen, U. G.; Andersen, M. I.; Burgdorf, M. J.; Ciceri, S.; D’Ago, G.; Evans, D. F.; Gu, S.-H.; Hinse, T. C.; Kains, N.; Kerins, E.; Korhonen, H.; Kuffmeier, M.; Mancini, L.; Popovas, A.; Rabus, M.; Rahvar, S.; Rasmussen, R. T.; Scarpetta, G.; Southworth, J.; Surdej, J.; Unda-Sanzana, E.; Verma, P.; von Essen, C.; Wang, Y.-B.; Wertz, O.; MiNDSTEp group

    2016-05-01

    The microlensing event OGLE-2015-BLG-0448 was observed by Spitzer and lay within the tidal radius of the globular cluster NGC 6558. The event had moderate magnification and was intensively observed, hence it had the potential to probe the distribution of planets in globular clusters. We measure the proper motion of NGC 6558 ({{\\boldsymbol{μ }}}{cl}(N,E)=(+0.36+/- 0.10,+1.42+/- 0.10) {{mas}} {{{yr}}}-1) as well as the source and show that the lens is not a cluster member. Even though this particular event does not probe the distribution of planets in globular clusters, other potential cluster lens events can be verified using our methodology. Additionally, we find that microlens parallax measured using Optical Gravitational Lens Experiment (OGLE) photometry is consistent with the value found based on the light curve displacement between the Earth and Spitzer.

  15. Microlensing events by Proxima Centauri in 2014 and 2016: Opportunities for mass determination and possible planet detection

    SciTech Connect

    Sahu, Kailash C.; Bond, Howard E.; Anderson, Jay; Dominik, Martin E-mail: jayander@stsci.edu E-mail: md35@st-andrews.ac.uk

    2014-02-20

    We have found that Proxima Centauri, the star closest to our Sun, will pass close to a pair of faint background stars in the next few years. Using Hubble Space Telescope (HST) images obtained in 2012 October, we determine that the passage close to a mag 20 star will occur in 2014 October (impact parameter 1.''6), and to a mag 19.5 star in 2016 February (impact parameter 0.''5). As Proxima passes in front of these stars, the relativistic deflection of light will cause shifts in the positions of the background stars of ∼0.5 and 1.5 mas, respectively, readily detectable by HST imaging, and possibly by Gaia and ground-based facilities such as the Very Large Telescope. Measurement of these astrometric shifts offers a unique and direct method to measure the mass of Proxima. Moreover, if Proxima has a planetary system, the planets may be detectable through their additional microlensing signals, although the probability of such detections is small. With astrometric accuracies of 0.03 mas (achievable with HST spatial scanning), centroid shifts caused by Jovian planets are detectable at separations of up to 2.''0 (corresponding to 2.6 AU at the distance of Proxima), and centroid shifts by Earth-mass planets are detectable within a small band of 8 mas (corresponding to 0.01 AU) around the source trajectories. Jovian planets within a band of about 28 mas (corresponding to 0.036 AU) around the source trajectories would produce a brightening of the source by >0.01 mag and could hence be detectable. Estimated timescales of the astrometric and photometric microlensing events due to a planet range from a few hours to a few days, and both methods would provide direct measurements of the planetary mass.

  16. Possible Solution of the Long-standing Discrepancy in the Microlensing Optical Depth toward the Galactic Bulge by Correcting the Stellar Number Count

    NASA Astrophysics Data System (ADS)

    Sumi, T.; Penny, M. T.

    2016-08-01

    We find that significant incompleteness in stellar number counts results in a significant overestimate of the microlensing optical depth τ and event rate per star per year Γ toward the Galactic bulge from the first two years of the MOA-II survey. We find that the completeness in red clump giant (RCG) counts {f}{{RC}} decreases proportional to the galactic latitude b, as {f}{{RC}}=(0.63+/- 0.11)-(0.052+/- 0.028)× b, ranging between 1 and 0.7 at b=-6^\\circ ˜ -1\\buildrel{\\circ}\\over{.} 5. The previous measurements using all sources by difference image analysis (DIA) by MACHO and MOA-I suffer the same bias. On the other hand, the measurements using an RCG sample by OGLE-II, MACHO, and EROS were free from this bias because they selected only the events associated with the resolved stars. Thus, the incompleteness both in the number of events and stellar number count cancel out. We estimate τ and Γ by correcting this incompleteness. In the central fields with | l| \\lt 5^\\circ , we find {{Γ }}=[18.74+/- 0.91]× {10}-6\\exp [(0.53+/- 0.05)(3-| b| )] star‑1 yr‑1 and {τ }200=[1.84+/- 0.14]× {10}-6\\exp [(0.44+/- 0.07)(3-| b| )] for the 427 events with {t}{{E}}≤slant 200 days using all sources brighter than {I}s≤slant 20 mag. Our revised all-source τ measurements are about 2σ smaller than the other all-source measurements and are consistent with the RCG measurements within 1σ. We conclude that the long-standing problem on discrepancy between the high τ with all-source samples by DIA and low τ with RCG samples can probably be explained by the incompleteness of the stellar number count. A model fit to these measurements predicts {{Γ }}=4.60+/- 0.25× {10}-5 star‑1 yr‑1 at | b| ˜ -1\\buildrel{\\circ}\\over{.} 4 and -2\\buildrel{\\circ}\\over{.} 25\\lt l\\lt 3\\buildrel{\\circ}\\over{.} 75 for sources with I\\lt 20, where the future space mission, Wide Field Infrared Space Telescope, will observe.

  17. Possible Solution of the Long-standing Discrepancy in the Microlensing Optical Depth toward the Galactic Bulge by Correcting the Stellar Number Count

    NASA Astrophysics Data System (ADS)

    Sumi, T.; Penny, M. T.

    2016-08-01

    We find that significant incompleteness in stellar number counts results in a significant overestimate of the microlensing optical depth τ and event rate per star per year Γ toward the Galactic bulge from the first two years of the MOA-II survey. We find that the completeness in red clump giant (RCG) counts {f}{{RC}} decreases proportional to the galactic latitude b, as {f}{{RC}}=(0.63+/- 0.11)-(0.052+/- 0.028)× b, ranging between 1 and 0.7 at b=-6^\\circ ∼ -1\\buildrel{\\circ}\\over{.} 5. The previous measurements using all sources by difference image analysis (DIA) by MACHO and MOA-I suffer the same bias. On the other hand, the measurements using an RCG sample by OGLE-II, MACHO, and EROS were free from this bias because they selected only the events associated with the resolved stars. Thus, the incompleteness both in the number of events and stellar number count cancel out. We estimate τ and Γ by correcting this incompleteness. In the central fields with | l| \\lt 5^\\circ , we find {{Γ }}=[18.74+/- 0.91]× {10}-6\\exp [(0.53+/- 0.05)(3-| b| )] star‑1 yr‑1 and {τ }200=[1.84+/- 0.14]× {10}-6\\exp [(0.44+/- 0.07)(3-| b| )] for the 427 events with {t}{{E}}≤slant 200 days using all sources brighter than {I}s≤slant 20 mag. Our revised all-source τ measurements are about 2σ smaller than the other all-source measurements and are consistent with the RCG measurements within 1σ. We conclude that the long-standing problem on discrepancy between the high τ with all-source samples by DIA and low τ with RCG samples can probably be explained by the incompleteness of the stellar number count. A model fit to these measurements predicts {{Γ }}=4.60+/- 0.25× {10}-5 star‑1 yr‑1 at | b| ∼ -1\\buildrel{\\circ}\\over{.} 4 and -2\\buildrel{\\circ}\\over{.} 25\\lt l\\lt 3\\buildrel{\\circ}\\over{.} 75 for sources with I\\lt 20, where the future space mission, Wide Field Infrared Space Telescope, will observe.

  18. OGLE-IV Classification of Gaia16aua as a Microlensing Event

    NASA Astrophysics Data System (ADS)

    Mroz, P.; Udalski, A.; Wyrzykowski, L.

    2016-07-01

    The transient candidate Gaia16aua is located in the OGLE-IV field, GD1242, that has been regularly observed since 2013 in the course of the sub-survey: Galaxy Variability Survey (GVS) of the OGLE-IV Project.

  19. Interdependent Multi-Layer Networks: Modeling and Survivability Analysis with Applications to Space-Based Networks

    PubMed Central

    Castet, Jean-Francois; Saleh, Joseph H.

    2013-01-01

    This article develops a novel approach and algorithmic tools for the modeling and survivability analysis of networks with heterogeneous nodes, and examines their application to space-based networks. Space-based networks (SBNs) allow the sharing of spacecraft on-orbit resources, such as data storage, processing, and downlink. Each spacecraft in the network can have different subsystem composition and functionality, thus resulting in node heterogeneity. Most traditional survivability analyses of networks assume node homogeneity and as a result, are not suited for the analysis of SBNs. This work proposes that heterogeneous networks can be modeled as interdependent multi-layer networks, which enables their survivability analysis. The multi-layer aspect captures the breakdown of the network according to common functionalities across the different nodes, and it allows the emergence of homogeneous sub-networks, while the interdependency aspect constrains the network to capture the physical characteristics of each node. Definitions of primitives of failure propagation are devised. Formal characterization of interdependent multi-layer networks, as well as algorithmic tools for the analysis of failure propagation across the network are developed and illustrated with space applications. The SBN applications considered consist of several networked spacecraft that can tap into each other's Command and Data Handling subsystem, in case of failure of its own, including the Telemetry, Tracking and Command, the Control Processor, and the Data Handling sub-subsystems. Various design insights are derived and discussed, and the capability to perform trade-space analysis with the proposed approach for various network characteristics is indicated. The select results here shown quantify the incremental survivability gains (with respect to a particular class of threats) of the SBN over the traditional monolith spacecraft. Failure of the connectivity between nodes is also examined, and the

  20. Space-based Scintillation Nowcasting with the Communications/Navigation Outage Forecast System

    NASA Astrophysics Data System (ADS)

    Groves, K.; Starks, M.; Beach, T.; Basu, S.

    2008-12-01

    The Air Force Research Laboratory's Communication/Navigation Outage Forecast System (C/NOFS) fuses ground- and space-based data in a near real-time physics-based model aimed at forecasting and nowcasting equatorial scintillations and their impacts on satellite communications and navigation. A key component of the system is the C/NOFS satellite that was launched into a low-inclination (13°) elliptical orbit (400 km x 850 km) in April 2008. The satellite contains six sensors to measure space environment parameters including electron density and temperature, ion density and drift, electric and magnetic fields and neutral wind, as well as a tri-band radio beacon transmitting at 150 MHz, 400 MHz and 1067 MHz. Scintillation nowcasts are derived from measuring the one-dimensional in situ electron density fluctuations and subsequently modeling the propagation environment for satellite-to-ground radio links. The modeling process requires a number of simplifying assumptions regarding the three-dimensional structure of the ionosphere and the results are readily validated by comparisons with ground-based measurements of the satellite's tri-band beacon signals. In mid-September 2008 a campaign to perform detailed analyses of space-based scintillation nowcasts with numerous ground observations was conducted in the vicinity of Kwajalein Atoll, Marshall Islands. To maximize the collection of ground-truth data, the ALTAIR radar was employed to obtain detailed information on the spatial structure of the ionosphere during the campaign and to aid the improvement of space-based nowcasting algorithms. A comparison of these results will be presented; it appears that detailed information on the electron density structure is a limiting factor in modeling the scintillation environment from in situ observations.

  1. Ground- and Space-Based Temperature and Humidity Retrievals: Statistical Evaluation.

    NASA Astrophysics Data System (ADS)

    Boba Stankov, B.

    1996-03-01

    A near-real-time integrated temperature and water vapor sounding system has been designed and in operation since June 1993. It combines hourly data from the ground-based radio acoustic sounding system (RASS), a two-channel microwave radiometer, standard surface meteorological instruments, a lidar ceilometer, and the Aerodynamic Research Incorporated Communication, Addressing and Reporting System aboard commercial airlines with space-based data from the TIROS-N Operational Vertical Sounder (TOVS). The physical retrieval algorithm provided by the International TOVS Processing Package is used for combining the ground- and space-based temperature and humidity profiles. The first-guess profiles of temperature and humidity required by the physical retrieval algorithm arc obtained by using a statistical inversion technique and the ground-based remote sensors measurements.Statistical error estimates are presented for the hourly. near-real-time, ground-, and space-based retrieved temperature and humidity profiles based on 119 soundings collected during a two-month-long experiment conducted at Platteville, Colorado, during February and March 1994. Radiosonde data collected by the Environmental Technology Laboratory and the Winter Icing and Storms Program in Platteville and the National Weather Service in Denver, Colorado, are used for comparison. The comparison showed excellent agreement between retrieved and radiosonde soundings. Retrieved temperature profiles show better performance than the retrieved humidity profiles because of the high vertical resolution of the RASS measurements. It is suggested that adding more information from the new individual remote sensors as they develop, through the technique used here, would lead to further profiling improvements.

  2. System and technology considerations for space-based air traffic surveillance

    NASA Technical Reports Server (NTRS)

    Vaisnys, A.

    1986-01-01

    This paper describes the system trade-offs examined in a recent study of space-based air traffic surveillance. Three system options, each satisfying a set of different constraints, were considered. The main difference in the technology needed to implement the three systems was determined to be the size of the spacecraft antenna aperture. It was found that essentially equivalent position location accuracy could be achieved with apertures from 50 meters down to less than a meter in diameter, depending on the choice of signal structure and on the desired user update rate.

  3. The SAMEX Vector Magnetograph: A Design Study for a Space-Based Solar Vector Magnetograph

    NASA Technical Reports Server (NTRS)

    Hagyard, M. J.; Gary, G. A.; West, E. A.

    1988-01-01

    This report presents the results of a pre-phase A study performed by the Marshall Space Flight Center (MSFC) for the Air Force Geophysics Laboratory (AFGL) to develop a design concept for a space-based solar vector magnetograph and hydrogen-alpha telescope. These are two of the core instruments for a proposed Air Force mission, the Solar Activities Measurement Experiments (SAMEX). This mission is designed to study the processes which give rise to activity in the solar atmosphere and to develop techniques for predicting solar activity and its effects on the terrestrial environment.

  4. Testing Gravitational Physics with Space-based Gravitational-wave Observations

    NASA Technical Reports Server (NTRS)

    Baker, John G.

    2011-01-01

    Gravitational wave observations provide exceptional and unique opportunities for precision tests of gravitational physics, as predicted by general relativity (GR). Space-based gravitational wave measurements, with high signal-to-noise ratios and large numbers of observed events may provide the best-suited gravitational-wave observations for testing GR with unprecedented precision. These observations will be especially useful in testing the properties of gravitational waves and strong-field aspects of the theory which are less relevant in other observations. We review the proposed GR test based on observations of massive black hole mergers, extreme mass ratio inspirals, and galactic binary systems.

  5. Progress and Prospects toward a Space-based Gravitational-Wave Observatory

    NASA Technical Reports Server (NTRS)

    Baker, John

    2012-01-01

    Over the last few years there has been much activity in the effort to produce a space-based gravitational-wave observatory. These efforts have enriched the understanding of the scientific capabilities of such an observatory leading to broad recognition of its value as an astronomical instrument. At the same time, rapidly developing events in the US and Europe have lead to a more complicated outlook than the baseline Laser Interferometer Space Antenna (LISA) project plan of a few years ago. I will discuss recent progress and developments resulting from the European eLISA study and the SGO study in the US and prospects looking forward.

  6. Solid-State, High Energy 2-Micron Laser Development for Space-Based Remote Sensing

    NASA Technical Reports Server (NTRS)

    Singh, Upendra N.

    2010-01-01

    Lidar (light detection and ranging) remote sensing enjoys the advantages of excellent vertical and horizontal resolution; pointing capability; a signal source independent from natural light; and control and knowledge of transmitted wavelength, pulse shape, and polarization and received polarization. Lidar in space is an emerging technology now being developing to fit applications where passive sensors cannot meet current measurement requirements. Technical requirements for space lidar are more demanding than for ground-based or airborne systems. Perhaps the most distinguishing characteristics of space lidars are the environmental requirements. Space lidar systems must be specially designed to survive the mechanical vibration loads of launch and operate in the vacuum of space where exposure to ionizing radiation limits the electronic components available. Finally, space lidars must be designed to be highly reliable because they must operate without the need for repair or adjustment. Lifetime requirements tend to be important drivers of the overall system design. The maturity of the required technologies is a key to the development of any space lidar system. NASA entered a new era in the 1990 s with the approval of several space-based remote sensing missions employing laser radar (lidar) techniques. Following the steps of passive remote sensing and then active radar remote sensing, lidar sensors were a logical next step, providing independence from natural light sources, and better spatial resolution and smaller sensor size than radar sensors. The shorter electromagnetic wavelengths of laser light also allowed signal reflectance from air molecules and aerosol particles. The smaller receiver apertures allowed the concept of scanning the sensor field of view. However, technical problems with several space-based lidar missions during that decade led to concern at NASA about the risk of lidar missions. An external panel was convened to make recommendations to NASA. Their

  7. Cancellation of Laser Noise in Space-Based Interferometer Detectors of Gravitational Radiation

    NASA Technical Reports Server (NTRS)

    Tinto, Massimo

    1999-01-01

    We presented a time-domain procedure for accurately cancelling laser noise fluctuations in an unequal-arm Michelson interferometer. The method involves separately measuring the phase of the returning light relative to the phase of the transmitted light in each arm. By suitable offsetting and differencing of these two time series, the common laser noise is cancelled exactly. The technique presented in this paper is general, in such that it can be implemented with any (Earth as well as space-based) unequal-arms Michelson interferometers,

  8. Primary propulsion of electrothermal, ion, and chemical systems for space-based radar orbit transfer

    NASA Technical Reports Server (NTRS)

    Wang, S.-Y.; Staiger, P. J.

    1985-01-01

    An orbit transfer mission concept has been studied for a Space-Based Radar (SBR) where 40 kW required for radar operation is assumed available for orbit transfer propulsion. Arcjet, pulsed electrothermal (PET), ion, and storable chemical systems are considered for the primary propulsion. Transferring two SBR per shuttle flight to 1112 km/60 deg using eiectrical propulsion systems offers an increased payload at the expense of increased trip time, up to 2000 kg each, which may be critical for survivability. Trade offs between payload mass, transfer time, launch site, inclination, and height of parking orbits are presented.

  9. Primary propulsion of electrothermal, ion and chemical systems for space-based radar orbit transfer

    NASA Technical Reports Server (NTRS)

    Wang, S. Y.; Staiger, P. J.

    1985-01-01

    An orbit transfer mission concept has been studied for a Space-Based Radar (SBR) where 40 kW required for radar operation is assumed available for orbit transfer propulsion. Arcjet, pulsed electrothermal (PET), ion, and storable chemical systems are considered for the primary propulsion. Transferring two SBR per shuttle flight to 1112 km/60 deg using electrical propulsion systems offers an increased payload at the expense of increased trip time, up to 2000 kg each, which may be critical for survivability. Trade offs between payload mass, transfer time, launch site, inclination, and height of parking orbits are presented.

  10. Orbits and Pointing Strategies for Space-Based Telescopes into a European Space Surveillance System

    NASA Astrophysics Data System (ADS)

    Olmedo, Estrella; Sanchez-Ortiz, Noelia; Ramos-Lerate, Mercedes

    2009-03-01

    This paper describes the inclusion of optical images acquired from orbiting telescopes into an autonomous European space surveillance system via the Advance Space Surveillance System Simulator (AS4). Special interest on space-based observation of GEO objects exists since it avoids the weather dependence and longitudinal restrictions of ground-based observations of those objects. Furthermore, space-based observations allow the detection of small objects that are not detected from ground-based sensors.In order to analyze the impact of space-based telescopes images, several aspects have to be studied. The first consideration is the selection of the appropriate orbits to locate the telescopes. A description of the most suitable orbits and strategies for the observation of space debris population will be provided.Once an appropriated orbit has been selected, the next important consideration is the analysis of an optimized pointing strategy and its associated requirements for feasibility. Several pointing strategies will be exposed by analyzing, among other factors, the impact of luminosity conditions in the most populated regions to be observed. Numerical results are presented in the form of statistics, which reflect the compromise between the density of detected objects, and other important parameters for orbit determination and cataloguing purposes as re-acquisition times or measurement track duration.Finally, overall analyses of possible space-based constellations are presented. Such constellations are aimed to solve the main drawbacks in considering only one satellite at the selected orbit. This is for example the case of revisit times when considering a sub GEO orbiting telescope which can be solve by re-distributing several sensors in the orbit. It will also allow carrying on more complex pointing strategies by the definition of several sensors located at same orbit pointed at two different regions.The AS4 was developed by DEIMOS Space ([1], [2] and also [5]). The

  11. Clutter-Doppler spectral analysis for a space-based radar

    NASA Astrophysics Data System (ADS)

    Mokole, Eric L.

    1991-05-01

    The impact of worst-case, ionospheric scintillation on the clutter-Doppler spectrum is analyzed for a space-based radar that operates between 100 and 1300 MHz. Analytical expressions for the spectrum are derived for a narrow, Gaussian antenna beam. For normal system parameters, the analytical expressions, combined with data from the Defense Nuclear Agency's Wideband satellite experiment, are used to compare the relative significance of the components of the clutter-Doppler spread for a range cell and to obtain the clutter-Doppler spread over the antenna's mainlobe. In addition, lower bounds are determined on the achievable reduction in the clutter-Doppler spread of a system.

  12. Ground and space based optical analysis of materials degradation in low-Earth-orbit

    NASA Technical Reports Server (NTRS)

    Woollam, John A.; Synowicki, Ron; Hale, Jeffrey S.; Peterkin, Jane; Machlab, Hassanayn; De, Bhola N.; Johs, Blaine

    1991-01-01

    There is strong interest in being able to accurately and sensitively monitor materials degradation in both ground-based and space-based environments. Two optical techniques for sensitive degradation monitoring are reviewed: spectroscopic ellipsometry and photothermal spectroscopy. These techniques complement each other in that ellipsometry is sensitive to atomically thin surface and subsurface changes, and photothermal spectroscopy is sensitive to local defects, pin-holes, subsurface defects, and delamination. Progress in applying these spectroscopies (both ex situ and in situ) to atomic oxygen degradation of space materials is reviewed.

  13. Innovative Approaches to Space-Based Manufacturing and Rapid Prototyping of Composite Materials

    NASA Technical Reports Server (NTRS)

    Hill, Charles S.

    2012-01-01

    The ability to deploy large habitable structures, construct, and service exploration vehicles in low earth orbit will be an enabling capability for continued human exploration of the solar system. It is evident that advanced manufacturing methods to fabricate replacement parts and re-utilize launch vehicle structural mass by converting it to different uses will be necessary to minimize costs and allow flexibility to remote crews engaged in space travel. Recent conceptual developments and the combination of inter-related approaches to low-cost manufacturing of composite materials and structures are described in context leading to the possibility of on-orbit and space-based manufacturing.

  14. Comparisons of Space-based GPS Occultation Ionospheric Scintillation Measurements with Ground-based VHF Measurements

    NASA Astrophysics Data System (ADS)

    Ruggiero, F. H.; Groves, K. M.; Starks, M. J.; Beach, T. L.

    2008-12-01

    Ionospheric irregularities are known to cause scintillation of transionospheric radio signals and can affect space-based UHF/VHF communications, causing outages, and degrade GPS accuracy and precision. Current capability for characterizing and predicting ionospheric scintillation utilizes a network of ground- based receivers to detect scintillation and then extrapolate for short-term forecasts. Practical limits on deploying the ground receivers limits the accuracy and spatial coverage one can achieve with this approach. A more global approach is to use a set of space-based satellites equipped with GPS receivers, such as the COSMIC satellite constellation, to measure scintillations observed during so-called occultations with GPS satellites. The term occultation refers to the geometry where the clear line-of-sight path between the space- based GPS receiver and the GPS satellite is ultimately blocked, or occulted, by the earth's surface. Before or after occultation the ray-path passes through the lower atmosphere and ionosphere providing information on the total electron content (TEC) and irregularities between the transmitter and the receiver. In this paper the signal-to-noise values of GPS L1 signals received on the COSMIC (and possibly C/NOFS if available) satellites are examined to help identify areas of ionospheric scintillation. The S4 scintillation index values from these occultations are compared with ground-based VHF S4 scintillation measurements from several equatorial stations. Preliminary results show that while there are cases where both the occultation and ground measurements indicate enhanced scintillation, there are also a number of cases where the occultation GPS S4 is significantly larger than the ground-based VHF S4, somewhat contrary to expectations given that scintillation effects generally increase with decreasing frequency. Reasons for high GPS S4 in the presence of relatively low VHF S4 include geometry differences between space- and ground

  15. Space-Based Gravitational-Wave Observatory (SGO) Mission Concept Study

    NASA Technical Reports Server (NTRS)

    Livas, Jeffrey; McNamara, Paul; Jennrich, Oliver

    2012-01-01

    The LISA Mission Concept has been under study for over two decades as a space-based gravitational-wave detector capable of observing astrophysical sources in the 0.0001 to 1 Hz band. The concept has consistently received strong recommendations from various review panels based on the expected science, most recently from the US Astr02010 Decadal Review. Budget constraints have led both the US and European Space agencies to search for lower cost options. We report results from the US effort to explore the tradeoffs between mission cost and science return.

  16. Manned space flight nuclear system safety. Volume 6: Space base nuclear system safety plan

    NASA Technical Reports Server (NTRS)

    1972-01-01

    A qualitative identification of the steps required to assure the incorporation of radiological system safety principles and objectives into all phases of a manned space base program are presented. Specific areas of emphasis include: (1) radiological program management, (2) nuclear system safety plan implementation, (3) impact on program, and (4) summary of the key operation and design guidelines and requirements. The plan clearly indicates the necessity of considering and implementing radiological system safety recommendations as early as possible in the development cycle to assure maximum safety and minimize the impact on design and mission plans.

  17. A space-based public service platform for terrestrial rescue operations

    NASA Technical Reports Server (NTRS)

    Fleisig, R.; Bernstein, J.; Cramblit, D. C.

    1977-01-01

    The space-based Public Service Platform (PSP) is a multibeam, high-gain communications relay satellite that can provide a variety of functions for a large number of people on earth equipped with extremely small, very low cost transceivers. This paper describes the PSP concept, the rationale used to derive the concept, the criteria for selecting specific communication functions to be performed, and the advantages of performing such functions via satellite. The discussion focuses on the benefits of using a PSP for natural disaster warning; control of attendant rescue/assistance operations; and rescue of people in downed aircraft, aboard sinking ships, lost or injured on land.

  18. Attitude and vibration control of a large flexible space-based antenna

    NASA Technical Reports Server (NTRS)

    Joshi, S. M.

    1982-01-01

    Control systems synthesis is considered for controlling the rigid body attitude and elastic motion of a large deployable space-based antenna. Two methods for control systems synthesis are considered. The first method utilizes the stability and robustness properties of the controller consisting of torque actuators and collocated attitude and rate sensors. The second method is based on the linear-quadratic-Gaussian control theory. A combination of the two methods, which results in a two level hierarchical control system, is also briefly discussed. The performance of the controllers is analyzed by computing the variances of pointing errors, feed misalignment errors and surface contour errors in the presence of sensor and actuator noise.

  19. Pointing and figure control system for a space-based far-IR segmented telescope

    NASA Technical Reports Server (NTRS)

    Lau, Kenneth

    1993-01-01

    A pointing and figure control system for two space-based far-IR telescopes, the 10-20 m Large Deployable Reflector and the 3.6 m Submillimeter Intermediate Mission, is described. The figure maintenance control system is designed to counter the optical elements translational and rotational changes induced by long-term thermal drifts that the support structure may experience. The pointing system applies optical truss to telescope pointing; a laser metrology system is used to transfer pointing informaton from an external fine guidance sensor to the telescope optical boresight, defined by the primary mirror, secondary mirror, and focal plane assembly.

  20. Ionospheric effects on a wide-bandwidth, polarimetric, space-based, synthetic-aperture radar

    NASA Astrophysics Data System (ADS)

    Brock, B. C.

    1993-01-01

    The earth's ionosphere consists of an ionized plasma which will interact with any electromagnetic wave propagating through it. The interaction is particularly strong at vhf and uhf frequencies but decreases for higher microwave frequencies. These interaction effects and their relationship to the operation of a wide-bandwidth, synthetic-aperture, space-based radar are examined. Emphasis is placed on the dispersion effects and the polarimetric effects. Results show that high-resolution (wide-bandwidth) and high-quality coherent polarimetrics will be very difficult to achieve below 1 GHz.

  1. Optical asymmetric cryptography using a three-dimensional space-based model

    NASA Astrophysics Data System (ADS)

    Chen, Wen; Chen, Xudong

    2011-07-01

    In this paper, we present optical asymmetric cryptography combined with a three-dimensional (3D) space-based model. An optical multiple-random-phase-mask encoding system is developed in the Fresnel domain, and one random phase-only mask and the plaintext are combined as a series of particles. Subsequently, the series of particles is translated along an axial direction, and is distributed in a 3D space. During image decryption, the robustness and security of the proposed method are further analyzed. Numerical simulation results are presented to show the feasibility and effectiveness of the proposed optical image encryption method.

  2. An improved space-based algorithm for recognizing vehicle models from the side view

    NASA Astrophysics Data System (ADS)

    Wang, Qian; Ding, Youdong; Zhang, Li; Li, Rong; Zhu, Jiang; Xie, Zhifeng

    2015-12-01

    Vehicle model matching problem from the side view is a problem meets the practical needs of actual users, but less focus by researchers. We propose a improved feature space-based algorithm for this problem. The algorithm combines the various advantages of some classic algorithms, and effectively combining global and local feature, eliminate data redundancy and improve data divisibility. And finally complete the classification by quick and efficient KNN. The real scene test results show that the proposed method is robust, accurate, insensitive to external factors, adaptable to large angle deviations, and can be applied to a formal application.

  3. Working fluid selection for space-based two-phase heat transport systems

    NASA Technical Reports Server (NTRS)

    Mclinden, Mark O.

    1988-01-01

    The working fluid for externally-mounted, space-based two-phase heat transport systems is considered. A sequence of screening criteria involving freezing and critical point temperatures and latent heat of vaporization and vapor density are applied to a data base of 860 fluids. The thermal performance of the 52 fluids which pass this preliminary screening are then ranked according to their impact on the weight of a reference system. Upon considering other nonthermal criteria (flammability, toxicity, and chemical stability) a final set of 10 preferred fluids is obtained. The effects of variations in system parameters is investigated for these 10 fluids by means of a factorial design.

  4. Nuclear reactor power as applied to a space-based radar mission

    NASA Technical Reports Server (NTRS)

    Jaffe, L.; Fujita, T.; Beatty, R.; Bhandari, P.; Chow, E.; Deininger, W.; Ewell, R.; Grossman, M.; Kia, T.; Nesmith, B.

    1988-01-01

    The SP-100 Project was established to develop and demonstrate feasibility of a space reactor power system (SRPS) at power levels of 10's of kilowatts to a megawatt. To help determine systems requirements for the SRPS, a mission and spacecraft were examined which utilize this power system for a space-based radar to observe moving objects. Aspects of the mission and spacecraft bearing on the power system were the primary objectives of this study; performance of the radar itself was not within the scope. The study was carried out by the Systems Design Audit Team of the SP-100 Project.

  5. Taking the Politics Out of Satellite and Space-Based Communications Protocols

    NASA Technical Reports Server (NTRS)

    Ivancic, William D.

    2006-01-01

    After many years of studies, experimentation, and deployment, large amounts of misinformation and misconceptions remain regarding applicability of various communications protocols for use in satellite and space-based networks. This paper attempts to remove much of the politics, misconceptions, and misinformation that have plagued spacebased communications protocol development and deployment. This paper provides a common vocabulary for communications; a general discussion of the requirements for various communication environments; an evaluation of tradeoffs between circuit and packet-switching technologies, and the pros and cons of various link, network, transport, application, and security protocols. Included is the applicability of protocol enhancing proxies to NASA, Department of Defense (DOD), and commercial space communication systems.

  6. Space-Based Remote Sensing of the Earth: A Report to the Congress

    NASA Technical Reports Server (NTRS)

    1987-01-01

    The commercialization of the LANDSAT Satellites, remote sensing research and development as applied to the Earth and its atmosphere as studied by NASA and NOAA is presented. Major gaps in the knowledge of the Earth and its atmosphere are identified and a series of space based measurement objectives are derived. The near-term space observations programs of the United States and other countries are detailed. The start is presented of the planning process to develop an integrated national program for research and development in Earth remote sensing for the remainder of this century and the many existing and proposed satellite and sensor systems that the program may include are described.

  7. Technology Reference and Proof-of-Concept for a Space -Based Automatic Identification System for Maritime Security

    NASA Astrophysics Data System (ADS)

    Helleren, Ø.; Olsen, Ø.; Bernsten, P. C.; Strauch, K.; Alagha, N.

    2008-08-01

    There is a growing need to develop a global maritime surveillance capability for safety and security. Space based reception of the automatic identification system (AIS) can improve ship traffic monitoring in the open seas. This paper gives a summary of the findings from a study by the European Space Agency called "Technology Reference and Proof-of Concept for a Space-Based AIS System for Maritime Security". The study was performed by the Norwegian Defence Research Establishment (FFI), together with Kongsberg Seatex AS, Norspace AS and SSTL. The study focused on receiver technologies and antenna concepts, running advanced detection probability simulations to evaluate the best concepts for space-based AIS systems.

  8. FURTHER EVIDENCE THAT QUASAR X-RAY EMITTING REGIONS ARE COMPACT: X-RAY AND OPTICAL MICROLENSING IN THE LENSED QUASAR Q J0158-4325

    SciTech Connect

    Morgan, Christopher W.; Hainline, Laura J.; Chen Bin; Dai Xinyu; Tewes, Malte; Courbin, F.; Meylan, G.; Kochanek, Christopher S.; Kozlowski, Szymon; Blackburne, Jeffrey A.; Mosquera, Ana M.; Chartas, G.

    2012-09-01

    We present four new seasons of optical monitoring data and six epochs of X-ray photometry for the doubly imaged lensed quasar Q J0158-4325. The high-amplitude, short-period microlensing variability for which this system is known has historically precluded a time delay measurement by conventional methods. We attempt to circumvent this limitation by the application of a Monte Carlo microlensing analysis technique, but we are only able to prove that the delay must have the expected sign (image A leads image B). Despite our failure to robustly measure the time delay, we successfully model the microlensing at optical and X-ray wavelengths to find a half-light radius for soft X-ray emission log (r{sub 1/2,X,soft}/cm) = 14.3{sup +0.4}{sub -0.5}, an upper limit on the half-light radius for hard X-ray emission log (r{sub 1/2,X,hard}/cm) {<=} 14.6, and a refined estimate of the inclination-corrected scale radius of the optical R-band (rest frame 3100 A) continuum emission region of log (r{sub s} /cm) = 15.6 {+-} 0.3.

  9. Multicomponent composites and their application in replica mirrors for lightweight space-based optics

    NASA Astrophysics Data System (ADS)

    Vining, Stephen D.; Hood, Patrick J.

    2004-02-01

    Research and development in multi-component composites demonstrated new material and fabrication concepts for mirrors for space-based optics. Cornerstone Research Group, Inc., effort, conducted under contract to the Air Force Research Laboratory, developed new organic and inorganic composite materials and investigated their potential for application as light-weight, low-cost alternatives mitigating the drawbacks of conventional materials (glass and metals) and fabrication processes for space-based mirrors. This development demonstrated the feasibility of multi-component organic composites integrating cyanate ester resin with several reinforcements, especially carbon fabric and nanofibers. It demonstrated feasibility of high-quality cyanate ester-based syntactic composite (structural foam composed of microspheres embedded in resin). The development also demonstrated initial feasibility of multi-component inorganic composites integrating a proprietary inorganic resin with particulate and nanofiber reinforcements. These new materials (both organic and inorganic composites) show strong potential for achieving major reduction in mirror areal density (compared with current operational mirrors) while achieving strength, stiffness, and thermal properties required for space applications. Finally, this project demonstrated feasibility of a replication approach to mirror fabrication. With this fabrication technology, a composite mirror is cast directly to net figure and finish. This dramatically simplifies the mirror fabrication process, thereby enabling less expensive tooling than conventional practice for glass or metal mirrors. In production lots of identical mirrors (e.g., spacecraft constellations), the replication approach will provide radical reduction in mirror costs by eliminating the lengthy, expensive grinding and polishing processes for individual units.

  10. Optical laser cross-link in space-based systems used for satellite communications

    NASA Astrophysics Data System (ADS)

    Panahi, Allen; Kazemi, Alex A.

    2010-04-01

    Building high speed communications network using optical links in space has proven to be an extremely complicated task and many such schemes were tried without success in the past. However in the last few years, there has been impressive progress made to bring the concept to fruition in civilian and government non-classified projects. Space-based optical communications using satellites in low earth orbit (LEO) and Geo-synchronous orbits (GEO) hold great promise for the proposed Internet in the Sky network of the future. Laser Communications offer a viable alternative to established RF communications for inter-satellite links and other applications where high performance links are a necessity. This paper will focus on the requirements of the space-based lasers and optics used for beam forming, as well as receiver antenna gain and detectors used in free space communications. High data rate, small antenna size, narrow beam divergence, and a narrow field of view are characteristics of laser communications that offer a number of potential advantages for system design. Also discussed are the critical parameters in the transmitter, channel, receiver, and link budget that are employed in successful inter-satellite communications system.

  11. CEOS Contributions to Informing Energy Management and Policy Decision Making Using Space-Based Earth Observations

    NASA Technical Reports Server (NTRS)

    Eckman, Richard S.

    2009-01-01

    Earth observations are playing an increasingly significant role in informing decision making in the energy sector. In renewable energy applications, space-based observations now routinely augment sparse ground-based observations used as input for renewable energy resource assessment applications. As one of the nine Group on Earth Observations (GEO) societal benefit areas, the enhancement of management and policy decision making in the energy sector is receiving attention in activities conducted by the Committee on Earth Observation Satellites (CEOS). CEOS has become the "space arm" for the implementation of the Global Earth Observation System of Systems (GEOSS) vision. It is directly supporting the space-based, near-term tasks articulated in the GEO three-year work plan. This paper describes a coordinated program of demonstration projects conducted by CEOS member agencies and partners to utilize Earth observations to enhance energy management end-user decision support systems. I discuss the importance of engagement with stakeholders and understanding their decision support needs in successfully increasing the uptake of Earth observation products for societal benefit. Several case studies are presented, demonstrating the importance of providing data sets in formats and units familiar and immediately usable by decision makers. These projects show the utility of Earth observations to enhance renewable energy resource assessment in the developing world, forecast space-weather impacts on the power grid, and improve energy efficiency in the built environment.

  12. Atom optical experiments in the drop tower: a pathfinder for space based precision measurements

    NASA Astrophysics Data System (ADS)

    Herrmann, Sven; Resch, Andreas; Müntinga, Hauke; Laemmerzahl, Claus

    Recent years have seen much technological progress towards the application of ultra-cold atoms and degenerate quantum gases in future space based precision measurements. A first milestone was achieved by the QUANTUS collaboration with the successful creation of a Bose-Einstein condensate in a freely falling compact drop tower experiment. A next step will now be to demonstrate the feasibility of matter wave interferometry with increased precision due to the extended free evolution time available in zero gravity. This is a particular focus of the PRIMUS project, which also explores concepts to apply a fiber based optical frequency comb in such microgravity experiments. Here we report on the current status of this activity, including the first operation of an optical frequency comb in a microgravity environment. We also discuss the perspectives for space based fundamental physics experiments that might be enabled by such earth-bound pathfinder experiments in the long run. PRIMUS is a collaboration of ZARM at the Universitüt Bremen and of the Leibniz Universitüt Hannover. It is supported by the a a German Space Agency DLR with funds provided by the Federal Ministry of Economics and Technology (BMWi) under grant number DLR 50 WM 0842.

  13. Sub-Femto-g Free Fall for Space-Based Gravitational Wave Observatories: LISA Pathfinder Results

    NASA Astrophysics Data System (ADS)

    Armano, M.; Audley, H.; Auger, G.; Baird, J. T.; Bassan, M.; Binetruy, P.; Born, M.; Bortoluzzi, D.; Brandt, N.; Caleno, M.; Carbone, L.; Cavalleri, A.; Cesarini, A.; Ciani, G.; Congedo, G.; Cruise, A. M.; Danzmann, K.; de Deus Silva, M.; De Rosa, R.; Diaz-Aguiló, M.; Di Fiore, L.; Diepholz, I.; Dixon, G.; Dolesi, R.; Dunbar, N.; Ferraioli, L.; Ferroni, V.; Fichter, W.; Fitzsimons, E. D.; Flatscher, R.; Freschi, M.; García Marín, A. F.; García Marirrodriga, C.; Gerndt, R.; Gesa, L.; Gibert, F.; Giardini, D.; Giusteri, R.; Guzmán, F.; Grado, A.; Grimani, C.; Grynagier, A.; Grzymisch, J.; Harrison, I.; Heinzel, G.; Hewitson, M.; Hollington, D.; Hoyland, D.; Hueller, M.; Inchauspé, H.; Jennrich, O.; Jetzer, P.; Johann, U.; Johlander, B.; Karnesis, N.; Kaune, B.; Korsakova, N.; Killow, C. J.; Lobo, J. A.; Lloro, I.; Liu, L.; López-Zaragoza, J. P.; Maarschalkerweerd, R.; Mance, D.; Martín, V.; Martin-Polo, L.; Martino, J.; Martin-Porqueras, F.; Madden, S.; Mateos, I.; McNamara, P. W.; Mendes, J.; Mendes, L.; Monsky, A.; Nicolodi, D.; Nofrarias, M.; Paczkowski, S.; Perreur-Lloyd, M.; Petiteau, A.; Pivato, P.; Plagnol, E.; Prat, P.; Ragnit, U.; Raïs, B.; Ramos-Castro, J.; Reiche, J.; Robertson, D. I.; Rozemeijer, H.; Rivas, F.; Russano, G.; Sanjuán, J.; Sarra, P.; Schleicher, A.; Shaul, D.; Slutsky, J.; Sopuerta, C. F.; Stanga, R.; Steier, F.; Sumner, T.; Texier, D.; Thorpe, J. I.; Trenkel, C.; Tröbs, M.; Tu, H. B.; Vetrugno, D.; Vitale, S.; Wand, V.; Wanner, G.; Ward, H.; Warren, C.; Wass, P. J.; Wealthy, D.; Weber, W. J.; Wissel, L.; Wittchen, A.; Zambotti, A.; Zanoni, C.; Ziegler, T.; Zweifel, P.

    2016-06-01

    We report the first results of the LISA Pathfinder in-flight experiment. The results demonstrate that two free-falling reference test masses, such as those needed for a space-based gravitational wave observatory like LISA, can be put in free fall with a relative acceleration noise with a square root of the power spectral density of 5.2 ±0.1 fm s-2/√{Hz } , or (0.54 ±0.01 ) ×10-15 g/√{Hz } , with g the standard gravity, for frequencies between 0.7 and 20 mHz. This value is lower than the LISA Pathfinder requirement by more than a factor 5 and within a factor 1.25 of the requirement for the LISA mission, and is compatible with Brownian noise from viscous damping due to the residual gas surrounding the test masses. Above 60 mHz the acceleration noise is dominated by interferometer displacement readout noise at a level of (34.8 ±0.3 ) fm /√{Hz } , about 2 orders of magnitude better than requirements. At f ≤0.5 mHz we observe a low-frequency tail that stays below 12 fm s-2/√{Hz } down to 0.1 mHz. This performance would allow for a space-based gravitational wave observatory with a sensitivity close to what was originally foreseen for LISA.

  14. FalconSAT-7: Towards Rapidly Deployable Space-Based Surveillance

    NASA Astrophysics Data System (ADS)

    Andersen, G.; McHarg, M.; Asmolova, O.; Dearborn, M.

    2013-09-01

    The USAF Academy Department of Physics is building FalconSAT-7, a membrane solar telescope to be deployed from a 3U CubeSat in LEO. The primary optic is a 0.2m photon sieve - a diffractive element consisting of billions of tiny holes in an otherwise opaque polymer sheet. The membrane, its support structure, secondary optics, two imaging cameras and associated control/recording electronics are all packaged within half the CubeSat volume. Once in space the supporting pantograph structure is deployed to pulling the membrane flat under tension. The telescope will then be steered towards the Sun to gather images at H-alpha for transmission to the ground. Due for launch in 2015, FalconSAT-7 will serve as a pathfinder for future mission in lightweight, high-resolution space-based surveillance. We are currently investigating two possible options optimized for Earth observing and SSA. Our preliminary designs have a 0.3m aperture deployed from a 6-12U satellite. Such a telescope would be capable of providing sub-meter resolution of ground or space-based objects depending on the orbital characteristics.

  15. Constraint-based integration of planning and scheduling for space-based observatory management

    NASA Technical Reports Server (NTRS)

    Muscettola, Nicola; Smith, Steven F.

    1994-01-01

    Progress toward the development of effective, practical solutions to space-based observatory scheduling problems within the HSTS scheduling framework is reported. HSTS was developed and originally applied in the context of the Hubble Space Telescope (HST) short-term observation scheduling problem. The work was motivated by the limitations of the current solution and, more generally, by the insufficiency of classical planning and scheduling approaches in this problem context. HSTS has subsequently been used to develop improved heuristic solution techniques in related scheduling domains and is currently being applied to develop a scheduling tool for the upcoming Submillimeter Wave Astronomy Satellite (SWAS) mission. The salient architectural characteristics of HSTS and their relationship to previous scheduling and AI planning research are summarized. Then, some key problem decomposition techniques underlying the integrated planning and scheduling approach to the HST problem are described; research results indicate that these techniques provide leverage in solving space-based observatory scheduling problems. Finally, more recently developed constraint-posting scheduling procedures and the current SWAS application focus are summarized.

  16. The PLATO Simulator: modelling of high-precision high-cadence space-based imaging

    NASA Astrophysics Data System (ADS)

    Marcos-Arenal, P.; Zima, W.; De Ridder, J.; Aerts, C.; Huygen, R.; Samadi, R.; Green, J.; Piotto, G.; Salmon, S.; Catala, C.; Rauer, H.

    2014-06-01

    Context. Many aspects of the design trade-off of a space-based instrument and its performance can best be tackled through simulations of the expected observations. The complex interplay of various noise sources in the course of the observations make such simulations an indispensable part of the assessment and design study of any space-based mission. Aims: We present a formalism to model and simulate photometric time series of CCD images by including models of the CCD and its electronics, the telescope optics, the stellar field, the jitter movements of the spacecraft, and all of the important natural noise sources. Methods: This formalism has been implemented in a versatile end-to-end simulation software tool, specifically designed for the PLATO (Planetary Transists and Oscillations of Stars) space mission to be operated from L2, but easily adaptable to similar types of missions. We call this tool Plato Simulator. Results: We provide a detailed description of several noise sources and discuss their properties in connection with the optical design, the allowable level of jitter, the quantum efficiency of the detectors, etc. The expected overall noise budget of generated light curves is computed, as a function of the stellar magnitude, for different sets of input parameters describing the instrument properties. The simulator is offered to the scientific community for future use. Software package available at the Plato Simulator web site (http://https://fys.kuleuven.be/ster/Software/PlatoSimulator/).

  17. Solid-state coherent LIDAR technology for space-based wind measurement

    NASA Astrophysics Data System (ADS)

    Phillips, Mark W.; Hannon, Stephen M.; Henderson, Sammy W.; Gatt, Philip; Huffaker, Robert M.

    1997-01-01

    Pulsed coherent solid-state 2 micron laser radar systems have been developed at Coherent Technologies, Inc. for ground- and airborne-based applications. Ground-based measurements of wind profiles and aerosol backscatter have been performed for several years. Examples of wind and aerosol backscatter coefficient measurements will be presented which cover a variety of weather conditions. Airborne measurements of wind profiles below the aircraft have been performed by Wright Laboratories, operating in a VAD measurement mode and will be reviewed. An engineered flight-worthy coherent lidar system is under development at CTI for flight on the SR-71 aircraft, in support of the High Speed Civil Transport program. Flights will be conducted by NASA-Dryden Flight Research Center at altitudes above 60,000 feet for the measurement of atmospheric turbulence ahead of the aircraft. Efforts are also underway at CTI for the development of high power coherent laser radar systems. Extensive detailed physical optics models of diode-pumped solid-state laser performance have been developed to characterize transient thermo-optic aberrations and the overall efficiency of lasers intended for space-based applications. We are currently developing a 2 micron 0.5 J/pulse transmitter with a 10 Hz PRF and a pulse duration of 400 - 500 ns. The status and expected space-based wind measuring performance for this system will be presented.

  18. Vulnerability assessment of a space based weapon platform electronic system exposed to a thermonuclear weapon detonation

    SciTech Connect

    Perez, C.L.; Johnson, J.O.

    1994-03-01

    Rapidly changing world events, the increased number of nations with inter-continental ballistic missile capability, and the proliferation of nuclear weapon technology will increase the number of nuclear threats facing the world today. Monitoring these nation`s activities and providing an early warning and/or intercept system via reconnaissance and surveillance satellites and space based weapon platforms is a viable deterrent against a surprise nuclear attack. However, the deployment of satellite and weapon platform assets in space will subject the sensitive electronic equipment to a variety of natural and man-made radiation environments. These include Van Allen Belt protons and electrons; galactic and solar flare protons; and, neutrons, gamma rays, and X-rays from intentionally detonated fission and fusion weapons. In this paper, the MASH vl.0 code system is used to estimate the dose to the critical electronics components of an idealized space based weapon platform from neutron and gamma-ray radiation emitted from a thermonuclear weapon detonation in space. Fluence and dose assessments were performed for the platform fully loaded, and in several stages representing limited engagement scenarios. The results indicate vulnerabilities to the Command, Control, and Communication (C) bay instruments from radiation damage for a nuclear weapon detonation for certain source/platform orientations. The distance at which damage occurs will depend on the weapon yield (n,{gamma}/kiloton) and size (kilotons).

  19. Mission planning for space based satellite surveillance experiments with the MSX

    NASA Technical Reports Server (NTRS)

    Sridharan, R.; Fishman, T.; Robinson, E.; Viggh, H.; Wiseman, A.

    1994-01-01

    The Midcourse Space Experiment is a BMDO-sponsored scientific satellite set for launch within the year. The satellite will collect phenomenology data on missile targets, plumes, earth limb backgrounds and deep space backgrounds in the LWIR, visible and ultra-violet spectral bands. It will also conduct functional demonstrations for space-based space surveillance. The Space-Based Visible sensor, built by Lincoln Laboratory, Massachusetts Institute of Technology, is the primary sensor on board the MSX for demonstration of space surveillance. The SBV Processing, Operations and Control Center (SPOCC) is the mission planning and commanding center for all space surveillance experiments using the SBV and other MSX instruments. The guiding principle in the SPOCC Mission Planning System was that all routine functions be automated. Manual analyst input should be minimal. Major concepts are: (I) A high level language, called SLED, for user interface to the system; (2) A group of independent software processes which would generally be run in a pipe-line mode for experiment commanding but can be run independently for analyst assessment; (3) An integrated experiment cost computation function that permits assessment of the feasibility of the experiment. This paper will report on the design, implementation and testing of the Mission Planning System.

  20. Effect of Clouds on Apertures of Space-based Air Fluorescence Detectors

    NASA Technical Reports Server (NTRS)

    Sokolsky, P.; Krizmanic, J.

    2003-01-01

    Space-based ultra-high-energy cosmic ray detectors observe fluorescence light from extensive air showers produced by these particles in the troposphere. Clouds can scatter and absorb this light and produce systematic errors in energy determination and spectrum normalization. We study the possibility of using IR remote sensing data from MODIS and GOES satellites to delimit clear areas of the atmosphere. The efficiency for detecting ultra-high-energy cosmic rays whose showers do not intersect clouds is determined for real, night-time cloud scenes. We use the MODIS SST cloud mask product to define clear pixels for cloud scenes along the equator and use the OWL Monte Carlo to generate showers in the cloud scenes. We find the efficiency for cloud-free showers with closest approach of three pixels to a cloudy pixel is 6.5% exclusive of other factors. We conclude that defining a totally cloud-free aperture reduces the sensitivity of space-based fluorescence detectors to unacceptably small levels.