Modeling update for the Thirty Meter Telescope laser guide star dual-conjugate adaptive optics system

NASA Astrophysics Data System (ADS)

Gilles, Luc; Wang, Lianqi; Ellerbroek, Brent

2010-07-01

This paper describes the modeling efforts undertaken in the past couple of years to derive wavefront error (WFE) performance estimates for the Narrow Field Infrared Adaptive Optics System (NFIRAOS), which is the facility laser guide star (LGS) dual-conjugate adaptive optics (AO) system for the Thirty Meter Telescope (TMT). The estimates describe the expected performance of NFIRAOS as a function of seeing on Mauna Kea, zenith angle, and galactic latitude (GL). They have been developed through a combination of integrated AO simulations, side analyses, allocations, lab and lidar experiments.

Progress with the lick adaptive optics system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gavel, D T; Olivier, S S; Bauman, B

2000-03-01

Progress and results of observations with the Lick Observatory Laser Guide Star Adaptive Optics System are presented. This system is optimized for diffraction-limited imaging in the near infrared, 1-2 micron wavelength bands. We describe our development efforts in a number of component areas including, a redesign of the optical bench layout, the commissioning of a new infrared science camera, and improvements to the software and user interface. There is also an ongoing effort to characterize the system performance with both natural and laser guide stars and to fold this data into a refined system model. Such a model can bemore » used to help plan future observations, for example, predicting the point-spread function as a function of seeing and guide star magnitude.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

van Dam, M A; Mignant, D L; Macintosh, B A

In this paper, the adaptive optics (AO) system at the W.M. Keck Observatory is characterized. The authors calculate the error budget of the Keck AO system operating in natural guide star mode with a near infrared imaging camera. By modeling the control loops and recording residual centroids, the measurement noise and band-width errors are obtained. The error budget is consistent with the images obtained. Results of sky performance tests are presented: the AO system is shown to deliver images with average Strehl ratios of up to 0.37 at 1.58 {micro}m using a bright guide star and 0.19 for a magnitudemore » 12 star.« less

Image improvement from a sodium-layer laser guide star adaptive optics system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Max, C. E., LLNL

1997-06-01

A sodium-layer laser guide star beacon with high-order adaptive optics at Lick Observatory produced a factor of 2.4 intensity increase and a factor of 2 decrease in full width at half maximum for an astronomical point source, compared with image motion compensation alone. Image full widths at half maximum were identical for laser and natural guide stars (0.3 arc seconds). The Strehl ratio with the laser guide star was 65% of that with a natural guide star. This technique should allow ground-based telescopes to attain the diffraction limit, by correcting for atmospheric distortions.

Adaptive Optics Makes A Research Instrument Out Of A Commercial 30 cm Aperture Telescope

NASA Astrophysics Data System (ADS)

Durig, D. T.

1999-12-01

I recently upgraded my SBIG ST-8 CCD camera with the AO-7 Adaptive Optics unit. This has solved many of the problems with tracking errors and the stability of my telescope mount and allowed me to obtain useful astrometric information on asteroids, comets and supernovae. It is no longer easy to take automated remote images but as long as I am at the observatory, good quality data can be obtained. The AO-7 unit allows me to pick a guide star for the guiding CCD just slightly out of the field of view of the imaging CCD. I am able to guide at the rate of 5 corrections per second with a 13th magnitude guide star. The fastest I have been able to guide is 30 times per second, but there are not usually bright enough stars near the image field to use this rate. When I have to use a dimmer star to guide on, and my rate is as slow as once per two seconds, good results are possible as long as the winds are not too strong. With a focal length of 1775 mm (f/5.75) and 2x2 binning on the CDD I am able to reach at least 18th magnitude objects in a 30 second exposure, but the guiding has to be very good to use these images for astrometry. For objects dimmer than 17th magnitude I normally go to a 2 minute exposure. With this equipment I was the first to observe that a recently discovered object (Comet LINEAR S4) was a comet and not an asteroid as originally reported (see IAUC 7267). I have performed additional astrometric observations on Comets LINEAR S3, S4, T2 and Ferris U1. I have also performed measurements on over a dozen asteroids from the MPC Critical List.

Optomechanical design of TMT NFIRAOS Subsystems at INO

NASA Astrophysics Data System (ADS)

Lamontagne, Frédéric; Desnoyers, Nichola; Grenier, Martin; Cottin, Pierre; Leclerc, Mélanie; Martin, Olivier; Buteau-Vaillancourt, Louis; Boucher, Marc-André; Nash, Reston; Lardière, Olivier; Andersen, David; Atwood, Jenny; Hill, Alexis; Byrnes, Peter W. G.; Herriot, Glen; Fitzsimmons, Joeleff; Véran, Jean-Pierre

2017-08-01

The adaptive optics system for the Thirty Meter Telescope (TMT) is the Narrow-Field InfraRed Adaptive Optics System (NFIRAOS). Recently, INO has been involved in the optomechanical design of several subsystems of NFIRAOS, including the Instrument Selection Mirror (ISM), the NFIRAOS Beamsplitters (NBS), and the NFIRAOS Source Simulator system (NSS) comprising the Focal Plane Mask (FPM), the Laser Guide Star (LGS) sources, and the Natural Guide Star (NGS) sources. This paper presents an overview of these subsystems and the optomechanical design approaches used to meet the optical performance requirements under environmental constraints.

Hubble Space Telescope Fine Guidance Sensor and Two-Gyro Control Law Design, Implementation, and On-Orbit Performance. Part 3

NASA Technical Reports Server (NTRS)

Clapp, Brian R.

2005-01-01

For fifteen years, the science mission of the Hubble Space Telescope (HST) required using at least three rate gyros for n Controlling with alternate sensors to replace failing gyros can extend the HST science mission. A two-gyro control law has been designed and implemented using magnetometers, star trackers, and Fine Guidance Sensors (FGSs) to control vehicle rate about the missing gyro axis. The three aforementioned sensors are used in succession to reduce HST boresight jitter to less than 7 milli-arcseconds rms prior to science imaging. The Magnetometer and 2-Gyro (M2G) control law is used for large angle maneuvers and attitude control during earth. occultation of star trackers and FGSs. The Tracker and 2-Gyro (T2G) control law dampens M2G rates and controls attitude in preparation for guide star acquisition with the FGSs. The Fine Guidance Sensor and 2-Gyro (F2G) control law dampens T2G rates and controls HST attitude during science imaging. This paper describes the F2G control law. Details of F2G algorithms are presented, including computation of the FGS-measured star vector using non-linear equations, optimal estimation of HST body rate, design of the F2G control laws and gyro bias observer, SISO and MIMO linear stability analyses, and design of the F2G intramode transition and guide star acquisition logic. Results from an FGS flight spare ground test are presented that define acceptable HST jitter levels for successful guide star acquisition under two-gyro control. HST-specific disturbance and noise models are described that are based upon flight telemetry; these models are used in HSTSIM, a high-fidelity non-linear time domain simulation, to predict HST on-orbit disturbance responses and FGS interferometer Loss of Lock (LOL) characteristics under F2G control. Additional HSTSIM results are presented predicting HST quiescent boresight jitter performance, science maneuver performance, and observer configuration performance during F2G operation. Simulation results are compared to on-orbit data b m F2G flight tests performed in February 2005. Science images and point spread functions from the Advanced Camera for Surveys (ACS) High Resolution Camera (HRC) are presented that compare HST science performance under F2G versus three-gyro control. Images and flight telemetry show that HST boresight jitter with the new F2G control law is usually less than jitter using the three-gyro law, and HST boresight jitter during F2G operation is dependent upon guide star magnitude.

The numerical simulation tool for the MAORY multiconjugate adaptive optics system

NASA Astrophysics Data System (ADS)

Arcidiacono, C.; Schreiber, L.; Bregoli, G.; Diolaiti, E.; Foppiani, I.; Agapito, G.; Puglisi, A.; Xompero, M.; Oberti, S.; Cosentino, G.; Lombini, M.; Butler, R. C.; Ciliegi, P.; Cortecchia, F.; Patti, M.; Esposito, S.; Feautrier, P.

2016-07-01

The Multiconjugate Adaptive Optics RelaY (MAORY) is and Adaptive Optics module to be mounted on the ESO European-Extremely Large Telescope (E-ELT). It is an hybrid Natural and Laser Guide System that will perform the correction of the atmospheric turbulence volume above the telescope feeding the Multi-AO Imaging Camera for Deep Observations Near Infrared spectro-imager (MICADO). We developed an end-to-end Monte- Carlo adaptive optics simulation tool to investigate the performance of a the MAORY and the calibration, acquisition, operation strategies. MAORY will implement Multiconjugate Adaptive Optics combining Laser Guide Stars (LGS) and Natural Guide Stars (NGS) measurements. The simulation tool implement the various aspect of the MAORY in an end to end fashion. The code has been developed using IDL and use libraries in C++ and CUDA for efficiency improvements. Here we recall the code architecture, we describe the modeled instrument components and the control strategies implemented in the code.

ARGOS - the Laser Star Adaptive Optics for LBT

NASA Astrophysics Data System (ADS)

Rabien, S.; Barl, L.; Beckmann, U.; Blümchen, T.; Bonaglia, M.; Borelli, J. L.; Brynnel, J.; Busoni, L.; Carbonaro, L.; Conot, C.; Davies, R.; Deysenroth, M.; Durney, O.; Elberich, M.; Esposito, S.; Gasho, V.; Gässler, W.; Gemperlein, H.; Genzel, R.; Green, R.; Haug, M.; Lloyd Hart, M.; Hubbard, P.; Kanneganti, S.; Kulas, M.; Noenickx, J.; Peter, D.; Quirrenbach, A.; Rademacher, M.; Rix, H. W.; Salinari, P.; Schwab, C.; Storm, J.; Strüder, L.; Thiel, M.; Weigelt, G.; Ziegleder, J.; Orban de Xivry, G.

2011-09-01

We will present the design and status of ARGOS - the Laser Guide Star adaptive optics facility for the Large Binocular Telescope. By projecting a constellation of multiple laser guide stars above each of the 8.4m primary mirrors of the LBT, ARGOS in its ground layer mode will enable a wide field adaptive optics correction for multi object spectroscopy. ARGOS implements high power pulsed green lasers and makes use of Rayleigh scattering for the guide star creation. The geometric relations of this setup in guide star height vs. primary diameter are quite comparable to an ELT with sodium guide stars. The use of LBT's adaptive secondary mirror, gated wavefront sensors, a prime focus calibration system and the laser constellation shows several aspects that may be used as pathfinding technology for the planned ELTs. In already planned upgrade steps with a hybrid Sodium-Rayleigh combination ARGOS will enable MCAO and MOAO implementations at LBT allowing unique astronomical observations.

Hybrid Architecture Active Wavefront Sensing and Control

NASA Technical Reports Server (NTRS)

Feinberg, Lee; Dean, Bruce; Hyde, Tupper

2010-01-01

A method was developed for performing relatively high-speed wavefront sensing and control to overcome thermal instabilities in a segmented primary mirror telescope [e.g., James Webb Space Telescope (JWST) at L2], by using the onboard fine guidance sensor (FGS) to minimize expense and complexity. This FGS performs centroiding on a bright star to feed the information to the pointing and control system. The proposed concept is to beam split the image of the guide star (or use a single defocused guide star image) to perform wavefront sensing using phase retrieval techniques. Using the fine guidance sensor star image for guiding and fine phasing eliminates the need for other, more complex ways of achieving very accurate sensing and control that is needed for UV-optical applications. The phase retrieval occurs nearly constantly, so passive thermal stability over fourteen days is not required. Using the FGS as the sensor, one can feed segment update information to actuators on the primary mirror that can update the primary mirror segment fine phasing with this frequency. Because the thermal time constants of the primary mirror are very slow compared to this duration, the mirror will appear extremely stable during observations (to the level of accuracy of the sensing and control). The sensing can use the same phase retrieval techniques as the JWST by employing an additional beam splitter, and having each channel go through a weak lens (one positive and one negative). The channels can use common or separate detectors. Phase retrieval can be performed onboard. The actuation scheme would include a coarse stage able to achieve initial alignment of several millimeters of range (similar to JWST and can use a JWST heritage sensing approach in the science camera) and a fine stage capable of continual updates.

The vibration compensation system for ARGOS

NASA Astrophysics Data System (ADS)

Peter, D.; Gaessler, W.; Borelli, J.; Kulas, M.

2011-09-01

For every adaptive optics system telescope vibrations can strongly reduce the performance. This is true for the receiver part of the system i.e. the telescope and wave front sensor part as well as for the transmitter part in the case of a laser guide star system. Especially observations in deep fields observed with a laser guide star system without any tip-tilt star will be greatly spoiled by telescope vibrations. The ARGOS GLAO system actually being built for the LBT aims to implement this kind of mode where wave front correction will rely purely on signals from the laser beacons. To remove the vibrations from the uplink path a vibration compensation system will be installed. This system uses accelerometers to measure the vibrations and corrects their effect with a small fast tip-tilt mirror. The controller of the system is built based on the assumption that the vibrations take place at a few distinct frequencies. Here I present a lab set-up of this system and show first results of the performance.

Current status of the laser guide star adaptive optics system for Subaru Telescope

NASA Astrophysics Data System (ADS)

Hayano, Yutaka; Takami, Hideki; Guyon, Olivier; Oya, Shin; Hattori, Masayuki; Saito, Yoshihiko; Watanabe, Makoto; Murakami, Naoshi; Minowa, Yosuke; Ito, Meguru; Colley, Stephen; Eldred, Michael; Golota, Taras; Dinkins, Matthew; Kashikawa, Nobunari; Iye, Masanori

2008-07-01

The current status and recent results, since last SPIE conference at Orlando in 2006, for the laser guide star adaptive optics system for Subaru Telescope is presented. We had a first light using natural guide star and succeed to launch the sodium laser beam in October 2006. The achieved Strehl ratio on the 10th magnitude star was around 0.5 at K band. We confirmed that the full-width-half-maximum of the stellar point spread function is smaller than 0.1 arcsec even at the 0.9 micrometer wavelehgth. The size of the artificial guide star by the laser beam tuned at the wavelength of 589 nm was estimated to be 10 arcsec. The obtained blurred artificial guide star is caused by the wavefront error on the laser launching telescope. After the first light and first launch, we found that we need to modify and to fix the components, which are temporarily finished. Also components, which were postponed to fabricate after the first light, are required to build newly. All components used by the natural guide star adaptive optics system are finalized recently and we are ready to go on the sky. Next engineering observation is scheduled in August, 2008.

Robust remote-pumping sodium laser for advanced LIDAR and guide star applications

NASA Astrophysics Data System (ADS)

Ernstberger, Bernhard; Enderlein, Martin; Friedenauer, Axel; Schwerdt, Robin; Wei, Daoping; Karpov, Vladimir; Leisching, Patrick; Clements, Wallace R. L.; Kaenders, Wilhelm G.

2015-10-01

The performance of large ground-based optical telescopes is limited due to wavefront distortions induced by atmospheric turbulence. Adaptive optics systems using natural guide stars with sufficient brightness provide a practical way for correcting the wavefront errors by means of deformable mirrors. Unfortunately, the sky coverage of bright stars is poor and therefore the concept of laser guide stars was invented, creating an artificial star by exciting resonance fluorescence from the mesospheric sodium layer about 90 km above the earth's surface. Until now, mainly dye lasers or sumfrequency mixing of solid state lasers were used to generate laser guide stars. However, these kinds of lasers require a stationary laser clean room for operation and are extremely demanding in maintenance. Under a development contract with the European Southern Observatory (ESO) and W. M. Keck Observatory (WMKO), TOPTICA Photonics AG and its partner MPB Communications have finalized the development of a next-generation sodium guide star laser system which is available now as a commercial off-the-shelf product. The laser is based on a narrow-band diode laser, Raman fiber amplifier (RFA) technology and resonant second-harmonic generation (SHG), thus highly reliable and simple to operate and maintain. It emits > 22 W of narrow-linewidth (≈ 5 MHz) continuous-wave radiation at sodium resonance and includes a re-pumping scheme for boosting sodium return flux. Due to the SHG resonator acting as spatial mode filter and polarizer, the output is diffraction-limited with RMS wavefront error < λ/25. Apart from this unique optical design, a major effort has been dedicated to integrating all optical components into a ruggedized system, providing a maximum of convenience and reliability for telescope operators. The new remote-pumping architecture allows for a large spatial separation between the main part of the laser and the compact laser head. Together with a cooling-water flow of less than 5 l/min and an overall power consumption of < 700 W, the system offers a maximum of flexibility with minimal infrastructure demands on site. Each system is built in a modular way, based on the concept of line-replaceable units (LRU). A comprehensive system software, as well as an intuitive service GUI, allow for remote control and error tracking down to at least the LRU level. In case of a failure, any LRU can be easily replaced. With these fiber-based guide star lasers, TOPTICA for the first time offers a fully engineered, off-the-shelf guide star laser system for groundbased optical telescopes providing convenient, turn-key operation in remote and harsh locations. Reliability and flexibility will be beneficial in particular for advanced satellite and space debris tracking as well as LIDAR applications.

First significant image improvement from a sodium-layer laser guide star adaptive optics system at Lick Observatory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Olivier, S.S.; Max, C.E.; Friedman, H.W.

1997-07-14

Atmospheric turbulence severely limits the resolution of ground-based telescopes. Adaptive optics can correct for the aberrations caused by the atmosphere, but requires a bright wavefront reference source in close angular proximity to the object being imaged. Since natural reference stars of the necessary brightness are relatively rare, methods of generating artificial reference beacons have been under active investigation for more than a decade. In this paper, we report the first significant image improvement achieved using a sodium-layer laser guide star as a wavefront reference for a high- order adaptive optics system. An artificial beacon was created by resonant scattering frommore » atomic sodium in the mesosphere, at an altitude of 95 km. Using this laser guide star, an adaptive optics system on the 3 m Shane Telescope at Lick Observatory produced a factor of 2.4 increase in peak intensity and a factor of 2 decrease in full width at half maximum of a stellar image, compared with image motion compensation alone. The Strehl ratio when using the laser guide star as the reference was 65% of that obtained with a natural guide star, and the image full widths at half maximum were identical, 0.3 arc sec, using either the laser or the natural guide star. This sodium-layer laser guide star technique holds great promise for the world`s largest telescopes. 24 refs., 4 figs., 1 tab.« less

Methods for correcting tilt anisoplanatism in laser-guide-star-based multiconjugate adaptive optics.

PubMed

Ellerbroek, B L; Rigaut, F

2001-10-01

Multiconjugate adaptive optics (MCAO) is a technique for correcting turbulence-induced phase distortions in three dimensions instead of two, thereby greatly expanding the corrected field of view of an adaptive optics system. This is accomplished with use of multiple deformable mirrors conjugate to distinct ranges in the atmosphere, with actuator commands computed from wave-front sensor (WFS) measurements from multiple guide stars. Laser guide stars (LGSs) must be used (at least for the forseeable future) to achieve a useful degree of sky coverage in an astronomical MCAO system. Much as a single LGS cannot be used to measure overall wave-front tilt, a constellation of multiple LGSs at a common range cannot detect tilt anisoplanatism. This error alone will significantly degrade the performance of a MCAO system based on a single tilt-only natural guide star (NGS) and multiple tilt-removed LGSs at a common altitude. We present a heuristic, low-order model for the principal source of tilt anisoplanatism that suggests four possible approaches to eliminating this defect in LGS MCAO: (i) tip/tilt measurements from multiple NGS, (ii) a solution to the LGS tilt uncertainty problem, (iii) additional higher-order WFS measurements from a single NGS, or (iv) higher-order WFS measurements from both sodium and Rayleigh LGSs at different ranges. Sample numerical results for one particular MCAO system configuration indicate that approach (ii), if feasible, would provide the highest degree of tilt anisoplanatism compensation. Approaches (i) and (iv) also provide very useful levels of performance and do not require unrealistically low levels of WFS measurement noise. For a representative set of parameters for an 8-m telescope, the additional laser power required for approach (iv) is on the order of 2 W per Rayleigh LGS.

A large array of high-performance artificial stars using airship-supported small mirrors

NASA Astrophysics Data System (ADS)

Content, Robert; Foxwell, Mark; Murray, Graham J.

2004-10-01

We propose a practical system that can provide a large number of high performance artificial stars, of the order of a few hundred, using an array of small mirrors on an airship supported platform illuminated from the ground by a laser. Our concept offers several advantages over other guide star schemes: Airborne mirror arrays can furnish tip-tilt information; they also permit a considerable reduction in the total ground-laser power required; high intensity guide stars with very small angular image size are possible; and finally they offer very low scattered parasite laser light. More basic & simpler launch-laser & AO technologies can therefore be employed, with potentially huge cost savings, with potentially significant improvement in the quality of the AO correction. The general platform scheme and suitable lift technologies are also discussed. A novel concept for achieving precise positioning is presented whereby the platform & the lifting vehicle are linked by a tether, the platform having a degree of independent control. Our proposal would employ as the lift vehicle an autonomous high altitude airship of the type currently under widespread development in the commercial sector, for use as hubs for telecommunication networks, mobile telephone relay stations, etc.

Adaptive Optics for the Thirty Meter Telescope

NASA Astrophysics Data System (ADS)

Ellerbroek, Brent

2013-12-01

This paper provides an overview of the progress made since the last AO4ELT conference towards developing the first-light AO architecture for the Thirty Meter Telescope (TMT). The Preliminary Design of the facility AO system NFIRAOS has been concluded by the Herzberg Institute of Astrophysics. Work on the client Infrared Imaging Spectrograph (IRIS) has progressed in parallel, including a successful Conceptual Design Review and prototyping of On-Instrument WFS (OIWFS) hardware. Progress on the design for the Laser Guide Star Facility (LGSF) continues at the Institute of Optics and Electronics in Chengdu, China, including the final acceptance of the Conceptual Design and modest revisions for the updated TMT telescope structure. Design and prototyping activities continue for lasers, wavefront sensing detectors, detector readout electronics, real-time control (RTC) processors, and deformable mirrors (DMs) with their associated drive electronics. Highlights include development of a prototype sum frequency guide star laser at the Technical Institute of Physics and Chemistry (Beijing); fabrication/test of prototype natural- and laser-guide star wavefront sensor CCDs for NFIRAOS by MIT Lincoln Laboratory and W.M. Keck Observatory; a trade study of RTC control algorithms and processors, with prototyping of GPU and FPGA architectures by TMT and the Dominion Radio Astrophysical Observatory; and fabrication/test of a 6x60 actuator DM prototype by CILAS. Work with the University of British Columbia LIDAR is continuing, in collaboration with ESO, to measure the spatial/temporal variability of the sodium layer and characterize the sodium coupling efficiency of several guide star laser systems. AO performance budgets have been further detailed. Modeling topics receiving particular attention include performance vs. computational cost tradeoffs for RTC algorithms; optimizing performance of the tip/tilt, plate scale, and sodium focus tracking loops controlled by the NGS on-instrument wavefront sensors, sky coverage, PSF reconstruction for LGS MCAO, and precision astrometry for the galactic center and other observations.

Study of optimal wavefront sensing with elongated laser guide stars

NASA Astrophysics Data System (ADS)

Thomas, S. J.; Adkins, S.; Gavel, D.; Fusco, T.; Michau, V.

2008-06-01

Over the past decade, adaptive optics (AO) has become an established method for overcoming the effects of atmospheric turbulence on both astronomical imaging and spectroscopic observations. These systems are now beginning to make extensive use of laser guide star (LGS) techniques to improve performance and provide increased sky coverage. Sodium LGS AO employs one or more lasers at 589-nm wavelength to produce an artificial guide star through excitation of sodium atoms in the mesosphere (90 km altitude). Because of its dependence on the abundance and distribution of sodium atoms in the mesosphere, this approach has its own unique set of difficulties not seen with natural stars. The sodium layer exhibits time-dependent variations in density and altitude, and since it is at a finite range, the LGS images become elongated due to the thickness of the layer and the offset between the laser projection point and the subapertures of a Shack-Hartmann wavefront sensor (SHWFS). Elongation causes the LGS image to be spread out resulting in a decrease in the signal-to-noise ratio which, in turn, leads to an increase in SHWFS measurement error and therefore an increased error in wavefront phase reconstruction. To address the problem of elongation, and also to provide a higher level of readout performance and reduced readout noise, a new type of charge-coupled device (CCD) is now under development for Shack-Hartmann wavefront sensing called the polar coordinate CCD. In this device, discrete imaging arrays are provided in each SHWFS subaperture and the size, shape and orientation of each discrete imaging array are adjusted to optimally sample the LGS image. The device is referred to as the polar coordinate CCD because the location of each imager is defined by a polar coordinate system centred on the laser guide star projection point. This concept is especially suited to Extremely Large Telescopes (ELTs) where the effect of perspective elongation is a significant factor. In this paper, we evaluate the performance of centroiders based on this CCD geometry by evaluating the centroid error variance and also the linearity issues associated with LGS image sampling and truncation. We also describe how we will extend this work to address the problems presented by the time variability of the sodium layer and how this will impact SHWFS performance in LGS AO systems.

Thermal, Structural, and Optical Analysis of a Balloon-Based Imaging System

NASA Astrophysics Data System (ADS)

Borden, Michael; Lewis, Derek; Ochoa, Hared; Jones-Wilson, Laura; Susca, Sara; Porter, Michael; Massey, Richard; Clark, Paul; Netterfield, Barth

2017-03-01

The Subarcsecond Telescope And BaLloon Experiment, STABLE, is the fine stage of a guidance system for a high-altitude ballooning platform designed to demonstrate subarcsecond pointing stability over one minute using relatively dim guide stars in the visible spectrum. The STABLE system uses an attitude rate sensor and the motion of the guide star on a detector to control a Fast Steering Mirror to stabilize the image. The characteristics of the thermal-optical-mechanical elements in the system directly affect the quality of the point-spread function of the guide star on the detector, so a series of thermal, structural, and optical models were built to simulate system performance and ultimately inform the final pointing stability predictions. This paper describes the modeling techniques employed in each of these subsystems. The results from those models are discussed in detail, highlighting the development of the worst-case cold and hot cases, the optical metrics generated from the finite element model, and the expected STABLE residual wavefront error and decenter. Finally, the paper concludes with the predicted sensitivities in the STABLE system, which show that thermal deadbanding, structural pre-loading, and self-deflection under different loading conditions, and the speed of individual optical elements were particularly important to the resulting STABLE optical performance.

A near-infrared tip-tilt sensor for the Keck I laser guide star adaptive optics system

NASA Astrophysics Data System (ADS)

Wizinowich, Peter; Smith, Roger; Biasi, Roberto; Cetre, Sylvain; Dekany, Richard; Femenia-Castella, Bruno; Fucik, Jason; Hale, David; Neyman, Chris; Pescoller, Dietrich; Ragland, Sam; Stomski, Paul; Andrighettoni, Mario; Bartos, Randy; Bui, Khanh; Cooper, Andrew; Cromer, John; van Dam, Marcos; Hess, Michael; James, Ean; Lyke, Jim; Rodriguez, Hector; Stalcup, Thomas

2014-07-01

The sky coverage and performance of laser guide star (LGS) adaptive optics (AO) systems is limited by the natural guide star (NGS) used for low order correction. This limitation can be dramatically reduced by measuring the tip and tilt of the NGS in the near-infrared where the NGS is partially corrected by the LGS AO system and where stars are generally several magnitudes brighter than at visible wavelengths. We present the design of a near-infrared tip-tilt sensor that has recently been integrated with the Keck I telescope's LGS AO system along with some initial on-sky results. The implementation involved modifications to the AO bench, real-time control system, and higher level controls and operations software that will also be discussed. The tip-tilt sensor is a H2RG-based near-infrared camera with 0.05 arc second pixels. Low noise at high sample rates is achieved by only reading a small region of interest, from 2×2 to 16×16 pixels, centered on an NGS anywhere in the 100 arc second diameter field. The sensor operates at either Ks or H-band using light reflected by a choice of dichroic beamsplitters located in front of the OSIRIS integral field spectrograph.

Laser-only Adaptive Optics Achieves Significant Image Quality Gains Compared to Seeing-limited Observations over the Entire Sky

NASA Astrophysics Data System (ADS)

Howard, Ward S.; Law, Nicholas M.; Ziegler, Carl A.; Baranec, Christoph; Riddle, Reed

2018-02-01

Adaptive optics laser guide-star systems perform atmospheric correction of stellar wavefronts in two parts: stellar tip-tilt and high-spatial-order laser correction. The requirement of a sufficiently bright guide star in the field-of-view to correct tip-tilt limits sky coverage. In this paper, we show an improvement to effective seeing without the need for nearby bright stars, enabling full sky coverage by performing only laser-assisted wavefront correction. We used Robo-AO, the first robotic AO system, to comprehensively demonstrate this laser-only correction. We analyze observations from four years of efficient robotic operation covering 15000 targets and 42000 observations, each realizing different seeing conditions. Using an autoguider (or a post-processing software equivalent) and the laser to improve effective seeing independent of the brightness of a target, Robo-AO observations show a 39% ± 19% improvement to effective FWHM, without any tip-tilt correction. We also demonstrate that 50% encircled energy performance without tip-tilt correction remains comparable to diffraction-limited, standard Robo-AO performance. Faint-target science programs primarily limited by 50% encircled energy (e.g., those employing integral field spectrographs placed behind the AO system) may see significant benefits to sky coverage from employing laser-only AO.

The Performance of the Robo-AO Laser Guide Star Adaptive Optics System at the Kitt Peak 2.1 m Telescope

NASA Astrophysics Data System (ADS)

Jensen-Clem, Rebecca; Duev, Dmitry A.; Riddle, Reed; Salama, Maïssa; Baranec, Christoph; Law, Nicholas M.; Kulkarni, S. R.; Ramprakash, A. N.

2018-01-01

Robo-AO is an autonomous laser guide star adaptive optics (AO) system recently commissioned at the Kitt Peak 2.1 m telescope. With the ability to observe every clear night, Robo-AO at the 2.1 m telescope is the first dedicated AO observatory. This paper presents the imaging performance of the AO system in its first 18 months of operations. For a median seeing value of 1.″44, the average Strehl ratio is 4% in the i\\prime band. After post processing, the contrast ratio under sub-arcsecond seeing for a 2≤slant i\\prime ≤slant 16 primary star is five and seven magnitudes at radial offsets of 0.″5 and 1.″0, respectively. The data processing and archiving pipelines run automatically at the end of each night. The first stage of the processing pipeline shifts and adds the rapid frame rate data using techniques optimized for different signal-to-noise ratios. The second “high-contrast” stage of the pipeline is eponymously well suited to finding faint stellar companions. Currently, a range of scientific programs, including the synthetic tracking of near-Earth asteroids, the binarity of stars in young clusters, and weather on solar system planets are being undertaken with Robo-AO.

Four generations of sodium guide star lasers for adaptive optics in astronomy and space situational awareness

NASA Astrophysics Data System (ADS)

d'Orgeville, Céline; Fetzer, Gregory J.

2016-07-01

This paper recalls the history of sodium guide star laser systems used in astronomy and space situational awareness adaptive optics, analyzing the impact that sodium laser technology evolution has had on routine telescope operations. While it would not be practical to describe every single sodium guide star laser system developed to date, it is possible to characterize their evolution in broad technology terms. The first generation of sodium lasers used dye laser technology to create the first sodium laser guide stars in Hawaii, California, and Spain in the late 1980s and 1990s. These experimental systems were turned into the first laser guide star facilities to equip mediumto- large diameter adaptive optics telescopes, opening a new era of Laser Guide Star Adaptive Optics (LGS AO)-enabled diffraction-limited imaging from the ground. Although they produced exciting scientific results, these laser guide star facilities were large, power-hungry and messy. In the USA, a second-generation of sodium lasers was developed in the 2000s that used cleaner, yet still large and complex, solid-state laser technology. These are the systems in routine operation at the 8 to 10m-class astronomical telescopes and 4m-class satellite imaging facilities today. Meanwhile in Europe, a third generation of sodium lasers was being developed using inherently compact and efficient fiber laser technology, and resulting in the only commercially available sodium guide star laser system to date. Fiber-based sodium lasers are being or will soon be deployed at three astronomical telescopes and two space surveillance stations. These highly promising systems are still relatively large to install on telescopes and they remain significantly expensive to procure and maintain. We are thus proposing to develop a fourth generation of sodium lasers: based on semiconductor technology, these lasers could provide a definitive solution to the problem of sodium LGS AO laser sources for all astronomy and space situational awareness applications.

Atmospheric turbulence profiling with SLODAR using multiple adaptive optics wavefront sensors.

PubMed

Wang, Lianqi; Schöck, Matthias; Chanan, Gary

2008-04-10

The slope detection and ranging (SLODAR) method recovers atmospheric turbulence profiles from time averaged spatial cross correlations of wavefront slopes measured by Shack-Hartmann wavefront sensors. The Palomar multiple guide star unit (MGSU) was set up to test tomographic multiple guide star adaptive optics and provided an ideal test bed for SLODAR turbulence altitude profiling. We present the data reduction methods and SLODAR results from MGSU observations made in 2006. Wind profiling is also performed using delayed wavefront cross correlations along with SLODAR analysis. The wind profiling analysis is shown to improve the height resolution of the SLODAR method and in addition gives the wind velocities of the turbulent layers.

Space-Based Observations of Satellites From the MOST Microsatellite

DTIC Science & Technology

2006-11-01

error estimate for these observations. To perform differential photometry, reference magnitudes for the background stars are needed. The Hubble Guide ...22 6.3 External Calibration References ..................................................................... 23 6.4 Post...32 10. References

Polarization switching of sodium guide star laser for brightness enhancement

NASA Astrophysics Data System (ADS)

Fan, Tingwei; Zhou, Tianhua; Feng, Yan

2016-07-01

The efficiency of optical pumping that enhances the brightness of sodium laser guide star with circularly polarized light is reduced substantially due to the precession of sodium atoms in geomagnetic field. Switching the laser between left and right circular polarization at the Larmor frequency is proposed to improve the photon return. With ESO's cw laser guide star system at Paranal as example, numerical simulation for both square-wave and sine-wave polarization modulation is conducted. For the square-wave switching case, the return flux is increased when the angle between geomagnetic field and laser beam is larger than 60°, as much as 40% at 90°. The method can also be applied for remote measurement of magnetic field with available cw guide star laser.

Guide star targeting success for the HEAO-B observatory

NASA Technical Reports Server (NTRS)

Farrenkopf, R. L.; Hoffman, D. P.

1977-01-01

The statistics associated with the successful selection and acquisition of guide stars as attitude benchmarks for use in reorientation maneuvers of the HEAO-B observatory are considered as a function of the maneuver angle, initial attitude uncertainties, and the pertinent celestial region. Success likelihoods in excess of 0.99 are predicted assuming anticipated gyro and star tracker error sources. The maneuver technique and guide star selection constraints are described in detail. The results presented are specialized numerically to the HEAO-B observatory. However, the analytical techniques developed are considered applicable to broader classes of spacecraft requiring celestial targeting.

Guide-star-based computational adaptive optics for broadband interferometric tomography

PubMed Central

Adie, Steven G.; Shemonski, Nathan D.; Graf, Benedikt W.; Ahmad, Adeel; Scott Carney, P.; Boppart, Stephen A.

2012-01-01

We present a method for the numerical correction of optical aberrations based on indirect sensing of the scattered wavefront from point-like scatterers (“guide stars”) within a three-dimensional broadband interferometric tomogram. This method enables the correction of high-order monochromatic and chromatic aberrations utilizing guide stars that are revealed after numerical compensation of defocus and low-order aberrations of the optical system. Guide-star-based aberration correction in a silicone phantom with sparse sub-resolution-sized scatterers demonstrates improvement of resolution and signal-to-noise ratio over a large isotome. Results in highly scattering muscle tissue showed improved resolution of fine structure over an extended volume. Guide-star-based computational adaptive optics expands upon the use of image metrics for numerically optimizing the aberration correction in broadband interferometric tomography, and is analogous to phase-conjugation and time-reversal methods for focusing in turbid media. PMID:23284179

Research on the compensation of laser launch optics to improve the performance of the LGS spot.

PubMed

Liu, Jie; Wang, Jianli; Wang, Yuning; Tian, Donghe; Zheng, Quan; Lin, Xudong; Wang, Liang; Yang, Qingyun

2018-02-01

To improve the beam quality of the uplink laser, a 37 channel piezo-ceramic deformable mirror was inserted into the laser launch optics to compensate the static aberrations. An interferometer was used as the calibration light source as well as the wavefront sensor to perform closed-loop correction for the moment. About 0.38λ root mean square (rms) aberrations, including the deformable mirror's initial figure error, were compensated, and the residual error was less than 0.07λ rms. Field observations with a 2 m optical telescope demonstrated that the peak intensity value of the laser guide star (LGS) spot increased from 5650 to 7658, and the full width at half-maximum (FWHM) size reduced from 4.07 arcseconds to 3.52 arcseconds. With the compensation, an improved guide star spot can be obtained, which is crucial for the adaptive optics systems of ground-based large telescopes.

Solar tomography adaptive optics.

PubMed

Ren, Deqing; Zhu, Yongtian; Zhang, Xi; Dou, Jiangpei; Zhao, Gang

2014-03-10

Conventional solar adaptive optics uses one deformable mirror (DM) and one guide star for wave-front sensing, which seriously limits high-resolution imaging over a large field of view (FOV). Recent progress toward multiconjugate adaptive optics indicates that atmosphere turbulence induced wave-front distortion at different altitudes can be reconstructed by using multiple guide stars. To maximize the performance over a large FOV, we propose a solar tomography adaptive optics (TAO) system that uses tomographic wave-front information and uses one DM. We show that by fully taking advantage of the knowledge of three-dimensional wave-front distribution, a classical solar adaptive optics with one DM can provide an extra performance gain for high-resolution imaging over a large FOV in the near infrared. The TAO will allow existing one-deformable-mirror solar adaptive optics to deliver better performance over a large FOV for high-resolution magnetic field investigation, where solar activities occur in a two-dimensional field up to 60'', and where the near infrared is superior to the visible in terms of magnetic field sensitivity.

Real-time turbulence profiling with a pair of laser guide star Shack-Hartmann wavefront sensors for wide-field adaptive optics systems on large to extremely large telescopes.

PubMed

Gilles, L; Ellerbroek, B L

2010-11-01

Real-time turbulence profiling is necessary to tune tomographic wavefront reconstruction algorithms for wide-field adaptive optics (AO) systems on large to extremely large telescopes, and to perform a variety of image post-processing tasks involving point-spread function reconstruction. This paper describes a computationally efficient and accurate numerical technique inspired by the slope detection and ranging (SLODAR) method to perform this task in real time from properly selected Shack-Hartmann wavefront sensor measurements accumulated over a few hundred frames from a pair of laser guide stars, thus eliminating the need for an additional instrument. The algorithm is introduced, followed by a theoretical influence function analysis illustrating its impulse response to high-resolution turbulence profiles. Finally, its performance is assessed in the context of the Thirty Meter Telescope multi-conjugate adaptive optics system via end-to-end wave optics Monte Carlo simulations.

Atmospheric turbulence compensation with laser phase shifting interferometry

NASA Astrophysics Data System (ADS)

Rabien, S.; Eisenhauer, F.; Genzel, R.; Davies, R. I.; Ott, T.

2006-04-01

Laser guide stars with adaptive optics allow astronomical image correction in the absence of a natural guide star. Single guide star systems with a star created in the earth's sodium layer can be used to correct the wavefront in the near infrared spectral regime for 8-m class telescopes. For possible future telescopes of larger sizes, or for correction at shorter wavelengths, the use of a single guide star is ultimately limited by focal anisoplanatism that arises from the finite height of the guide star. To overcome this limitation we propose to overlap coherently pulsed laser beams that are expanded over the full aperture of the telescope, traveling upwards along the same path which light from the astronomical object travels downwards. Imaging the scattered light from the resultant interference pattern with a camera gated to a certain height above the telescope, and using phase shifting interferometry we have found a method to retrieve the local wavefront gradients. By sensing the backscattered light from two different heights, one can fully remove the cone effect, which can otherwise be a serious handicap to the use of laser guide stars at shorter wavelengths or on larger telescopes. Using two laser beams multiconjugate correction is possible, resulting in larger corrected fields. With a proper choice of laser, wavefront correction could be expanded to the visible regime and, due to the lack of a cone effect, the method is applicable to any size of telescope. Finally the position of the laser spot could be imaged from the side of the main telescope against a bright background star to retrieve tip-tilt information, which would greatly improve the sky coverage of the system.

True-sky demonstration of an autonomous star tracker

NASA Astrophysics Data System (ADS)

van Bezooijen, Roelof W.

1994-07-01

An autonomous star tracker (AST) is basically a `star field in, attitude out' device capable of determining its attitude without requiring any a priori attitude knowledge. In addition to this attitude acquisition capability, an AST can perform attitude updates autonomously and is able to provide its attitude `continuously' while tracking a star field. The Lockheed Palo Alto Research Laboratory is developing a reliable, low-cost, miniature AST that has a one arcsec overall accuracy, weighs less than 1.5 kg, consumes less than 7 watts of power, and is sufficiently sensitive to be used at all sky locations. The device performs attitude acquisition in a fraction of a second and outputs its attitude at a 10 Hz rate when operating in its tracking mode. Besides providing the functionality needed for future advanced attitude control and navigation systems, an AST also improves spacecraft reliability, mass, power, cost, and operating expenses. The AST comprises a-thermalized, refractive optics, a frame-transfer CCD with a sensitive area of 1024 by 1024 pixels, camera electronics implemented with application- specific integrated circuits, a compact single board computer with a radiation hard 32 bit RISC processor, and an all-sky guide star database. Star identification is performed by a memory- efficient and highly robust algorithm that finds the largest group of observed stars matching a group of guide stars. An important milestone has recently been achieved with the validation of the attitude acquisition capability through correct and rapid identification of all 704 true-sky star fields obtained at the Lick Observatory, using an uncalibrated prototype AST with a 512 by 1024 pixel frame-transfer CCD and a 50 mm f/1.2 lens that provided an effective 6.5 by 13.2 degree field of view. The overlapping fields cover 47% of the sky, including both rich and sparse areas. The paper contains a description of the AST, a summary of the functions enabled or improved by the device, an overview of the identification algorithm, results obtained with a realistic simulation program, a description of the true-sky star field identification method and a presentation of the results obtained. The AST tolerates the presence of bright objects as was demonstrated by a field that included Jupiter.

Single Fiber Star Couplers. [optical waveguides for spacecraft communication

NASA Technical Reports Server (NTRS)

Asawa, C. K.

1979-01-01

An ion exchange process was developed and used in the fabrication of state-of-the-art planar star couplers for distribution of optical radiation between optical fibers. An 8 x 8 planar transmission star coupler was packaged for evaluation purposes with sixteen fiber connectors and sixteen pigtails. Likewise a transmission star coupler and an eight-port reflection star coupler with eight-fiber ribbons rigidly attached to these couplers, and a planar coupler with silicon guides and a parallel channel guide with pigtails were also fabricated. Optical measurements of the transmission star couplers are included with a description of the manufacturing process.

Wavefront error budget development for the Thirty Meter Telescope laser guide star adaptive optics system

NASA Astrophysics Data System (ADS)

Gilles, Luc; Wang, Lianqi; Ellerbroek, Brent

2008-07-01

This paper describes the modeling effort undertaken to derive the wavefront error (WFE) budget for the Narrow Field Infrared Adaptive Optics System (NFIRAOS), which is the facility, laser guide star (LGS), dual-conjugate adaptive optics (AO) system for the Thirty Meter Telescope (TMT). The budget describes the expected performance of NFIRAOS at zenith, and has been decomposed into (i) first-order turbulence compensation terms (120 nm on-axis), (ii) opto-mechanical implementation errors (84 nm), (iii) AO component errors and higher-order effects (74 nm) and (iv) tip/tilt (TT) wavefront errors at 50% sky coverage at the galactic pole (61 nm) with natural guide star (NGS) tip/tilt/focus/astigmatism (TTFA) sensing in J band. A contingency of about 66 nm now exists to meet the observatory requirement document (ORD) total on-axis wavefront error of 187 nm, mainly on account of reduced TT errors due to updated windshake modeling and a low read-noise NGS wavefront sensor (WFS) detector. A detailed breakdown of each of these top-level terms is presented, together with a discussion on its evaluation using a mix of high-order zonal and low-order modal Monte Carlo simulations.

Generating Artificial Reference Images for Open Loop Correlation Wavefront Sensors

NASA Astrophysics Data System (ADS)

Townson, M. J.; Love, G. D.; Saunter, C. D.

2018-05-01

Shack-Hartmann wavefront sensors for both solar and laser guide star adaptive optics (with elongated spots) need to observe extended objects. Correlation techniques have been successfully employed to measure the wavefront gradient in solar adaptive optics systems and have been proposed for laser guide star systems. In this paper we describe a method for synthesising reference images for correlation Shack-Hartmann wavefront sensors with a larger field of view than individual sub-apertures. We then show how these supersized reference images can increase the performance of correlation wavefront sensors in regimes where large relative shifts are induced between sub-apertures, such as those observed in open-loop wavefront sensors. The technique we describe requires no external knowledge outside of the wavefront-sensor images, making it available as an entirely "software" upgrade to an existing adaptive optics system. For solar adaptive optics we show the supersized reference images extend the magnitude of shifts which can be accurately measured from 12% to 50% of the field of view of a sub-aperture and in laser guide star wavefront sensors the magnitude of centroids that can be accurately measured is increased from 12% to 25% of the total field of view of the sub-aperture.

Stellar occultation candidates from the guide star catalog. I - Saturn, 1991-1999

NASA Technical Reports Server (NTRS)

Bosh, A. S.; Mcdonald, S. W.

1992-01-01

A list of 203 potential occultations by Saturn and its ring of stars from the HST Guide Star Catalog (GSC) during the years 1991-1999 is presented. This list features many fainter candidates than do current occultation candidate lists for Saturn; these fainter stars can also provide a high signal-to-noise ratio if observed with a large telescope or in the IR where Saturn and its rings have absorption bands. The occultation circumstances are listed, as well as star information found in the GSC.

Hubble Space Telescope Reduced-Gyro Control Law Design, Implementation, and On-Orbit Performance

NASA Technical Reports Server (NTRS)

Clapp, Brian R.; Ramsey, Patrick R.; Wirzburger, John H.; Smith, Daniel C.; VanArsadall, John C.

2008-01-01

Following gyro failures in April 2001 and April 2003, HST Pointing Control System engineers designed reduced-gyro control laws to extend the spacecraft science mission. The Two-Gyro Science (TGS) and One-Gyro Science (OGS) control laws were designed and implemented using magnetometers, star trackers, and Fine Guidance Sensors in succession to control vehicle rate about the missing gyro axes. Both TGS and OGS have demonstrated on-orbit pointing stability of 7 milli-arcseconds or less, which depends upon the guide star magnitude used by the Fine Guidance Sensor. This paper describes the design, implementation, and on-orbit performance of the TGS and OGS control law fine-pointing modes using Fixed Head Star Trackers and Fine Guidance Sensors, after successfully achieving coarse-pointing control using magnetometers.

Transforming GSC-II Magnitudes into JWST/FGS Count Rates

NASA Astrophysics Data System (ADS)

Holfeltz, Sherie T.; Chayer, P.; Nelan, E. P.

2010-01-01

The JWST Fine Guidance Sensor (FGS) will provide the positions of guide stars to the spacecraft attitude control system to facilitate the fine pointing of the Observatory. The FGS is an infrared camera operating in an unfiltered passband from 0.6 to 5.3 microns. The ground system will select guide stars from the Guide Star Catalog II (GSC-II), which is an all-sky catalog with three optical passbands (BJ, RF, IN) derived from photographic plates, and from 2MASS. We present a method for predicting a guide star's FGS photon count rate, which is needed to operate the FGS. The method consists of first deriving equations for transforming the GSC-II optical passbands into J, H, and K for stars that are below the 2MASS faint limiting magnitude, based upon fitting the distribution of brighter stars in color-color diagrams using GSC-II and 2MASS photometry. Next, we convolve the BJ, RF, IN and predicted J, H, and K magnitudes (or 2MASS magnitudes if available) for a given star with the wavelength dependent throughput and sensitivity of the telescope and FGS. To estimate the accuracy of this method for stars that are too faint for 2MASS, we compare the predicted J, H, and K magnitudes for a large sample of stars to data from the United Kingdom Infrared Telescope (UKIRT) Deep Sky Survey (UKIDSS) Large Area Survey (LAS). Using synthetic magnitudes computed from Kurucz models for stars of different spectral types, we show that the method should provide reliable FGS count rates.

The Polychromatic Laser Guide Star: the ELP-OA demonstrator at Observatoire de Haute Provence

NASA Astrophysics Data System (ADS)

Foy, R.; Chatagnat, M.; Dubet, D.; Éric, P.; Eysseric, J.; Foy, F.-C.; Fusco, T.; Girard, J.; Laloge, A.; Le van Suu, A.; Messaoudi, B.; Perruchot, S.; Richaud, P.; Richaud, Y.; Rondeau, X.; Tallon, M.; Thiébaut, É.; Boër, M.

2007-07-01

The correction of the tilt for adaptive optics devices from the only laser guide star can be done with the polychromatic laser guide star. We report the progress of the first demonstrator of the implementation of this concept, at Observatoire de Haute-Provence. We review the last steps of the feasibility studies, the optimization of the laser parameters, and the studies of the implementation at the OHP 1.52m telescope, including the beam propagation to the lasers room to the mesosphere and the algorithms for tip-tilt measurements.

Guide star probabilities

NASA Technical Reports Server (NTRS)

Soneira, R. M.; Bahcall, J. N.

1981-01-01

Probabilities are calculated for acquiring suitable guide stars (GS) with the fine guidance system (FGS) of the space telescope. A number of the considerations and techniques described are also relevant for other space astronomy missions. The constraints of the FGS are reviewed. The available data on bright star densities are summarized and a previous error in the literature is corrected. Separate analytic and Monte Carlo calculations of the probabilities are described. A simulation of space telescope pointing is carried out using the Weistrop north galactic pole catalog of bright stars. Sufficient information is presented so that the probabilities of acquisition can be estimated as a function of position in the sky. The probability of acquiring suitable guide stars is greatly increased if the FGS can allow an appreciable difference between the (bright) primary GS limiting magnitude and the (fainter) secondary GS limiting magnitude.

Thirty Meter Telescope narrow-field infrared adaptive optics system real-time controller prototyping results

NASA Astrophysics Data System (ADS)

Smith, Malcolm; Kerley, Dan; Chapin, Edward L.; Dunn, Jennifer; Herriot, Glen; Véran, Jean-Pierre; Boyer, Corinne; Ellerbroek, Brent; Gilles, Luc; Wang, Lianqi

2016-07-01

Prototyping and benchmarking was performed for the Real-Time Controller (RTC) of the Narrow Field InfraRed Adaptive Optics System (NFIRAOS). To perform wavefront correction, NFIRAOS utilizes two deformable mirrors (DM) and one tip/tilt stage (TTS). The RTC receives wavefront information from six Laser Guide Star (LGS) Shack- Hartmann WaveFront Sensors (WFS), one high-order Natural Guide Star Pyramid WaveFront Sensor (PWFS) and multiple low-order instrument detectors. The RTC uses this information to determine the commands to send to the wavefront correctors. NFIRAOS is the first light AO system for the Thirty Meter Telescope (TMT). The prototyping was performed using dual-socket high performance Linux servers with the real-time (PREEMPT_RT) patch and demonstrated the viability of a commercial off-the-shelf (COTS) hardware approach to large scale AO reconstruction. In particular, a large custom matrix vector multiplication (MVM) was benchmarked which met the required latency requirements. In addition all major inter-machine communication was verified to be adequate using 10Gb and 40Gb Ethernet. The results of this prototyping has enabled a CPU-based NFIRAOS RTC design to proceed with confidence and that COTS hardware can be used to meet the demanding performance requirements.

On-Sky Tests of a High-Power Pulsed Laser for Sodium Laser Guide Star Adaptive Optics

NASA Astrophysics Data System (ADS)

Otarola, Angel; Hickson, Paul; Gagné, Ronald; Bo, Yong; Zuo, Junwei; Xie, Shiyong; Feng, Lu; Rochester, Simon; Budker, Dmitry; Shen, Shixia; Xue, Suijian; Min, Li; Wei, Kai; Boyer, Corinne; Ellerbroek, Brent; Hu, Jingyao; Peng, Qinjun; Xu, Zuyan

2016-03-01

We present results of on-sky tests performed in the summer of 2013 to characterize the performance of a prototype high-power pulsed laser for adaptive optics. The laser operates at a pulse repetition rate (PRR) of 600-800Hz, with a 6% duty cycle. Its coupling efficiency was found to be, in the best test case (using 18W of transmitted power), 231±14 photons s-1 sr-1 atom-1 W-1 m2 when circular polarization was employed and 167±17 photons s-1 sr-1 atom-1 W-1 m2 with linear polarization. No improvement was seen when D2b repumping was used, but this is likely due to the relatively large laser guide star (LGS) diameter, typically 10 arcsec or more, which resulted in low irradiance levels. Strong relaxation oscillations were present in the laser output, which have the effect of reducing the coupling efficiency. To better understand the results, a physical modeling was performed using the measured pulse profiles and parameters specific to these tests. The model results, for a 10 arcsec angular size LGS spot, agree well with the observations. When extrapolating the physical model for a sub-arcsecond angular size LGS (typical of what is needed for a successful astronomical guide star), the model predicts that this laser would have a coupling efficiency of 130 photons s-1 sr-1 atom-1 W-1 m2, using circular polarization and D2b repumping, for a LGS diameter of 0.6 arcsec Full Width at Half Maximum (FWHM), and free of relaxation oscillations in the 589 nm laser light.

Space-Based Astronomy: An Educator Guide with Activities for Science, Mathematics, and Technology Education

NASA Technical Reports Server (NTRS)

Vogt, Gregory L.

2001-01-01

If you go to the country, far from city lights, you can see about 3,000 stars on a clear night. If your eyes were bigger, you could see many more stars. With a pair of binoculars, an optical device that effectively enlarges the pupil of your eye by about 30 times, the number of stars you can see increases to the tens of thousands. With a medium-sized telescope with a light-collecting mirror 30 centimeters in diameter, you can see hundreds of thousands of stars. With a large observatory telescope, millions of stars become visible. 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. It is not intended to serve as a curriculum. Instead, teachers should select activities from this guide that support and extend existing study. The guide contains few of the traditional activities found in many astronomy guides such as constellation studies, lunar phases, and planetary orbits. It tells, rather, the story of why it is important to observe celestial objects from outer space and how to study the entire electromagnetic spectrum. Teachers are encouraged to adapt these activities for the particular needs of their students. When selected activities from this guide are used in conjunction with traditional astronomy curricula, students benefit from a more complete experience.

On-sky demonstration of matched filters for wavefront measurements using ELT-scale elongated laser guide stars

NASA Astrophysics Data System (ADS)

Basden, A. G.; Bardou, L.; Bonaccini Calia, D.; Buey, T.; Centrone, M.; Chemla, F.; Gach, J. L.; Gendron, E.; Gratadour, D.; Guidolin, I.; Jenkins, D. R.; Marchetti, E.; Morris, T. J.; Myers, R. M.; Osborn, J.; Reeves, A. P.; Reyes, M.; Rousset, G.; Lombardi, G.; Townson, M. J.; Vidal, F.

2017-04-01

The performance of adaptive optics systems is partially dependent on the algorithms used within the real-time control system to compute wavefront slope measurements. We demonstrate the use of a matched filter algorithm for the processing of elongated laser guide star (LGS) Shack-Hartmann images, using the CANARY adaptive optics instrument on the 4.2 m William Herschel Telescope and the European Southern Observatory Wendelstein LGS Unit placed 40 m away. This algorithm has been selected for use with the forthcoming Thirty Meter Telescope, but until now had not been demonstrated on-sky. From the results of a first observing run, we show that the use of matched filtering improves our adaptive optics system performance, with increases in on-sky H-band Strehl measured up to about a factor of 1.1 with respect to a conventional centre of gravity approach. We describe the algorithm used, and the methods that we implemented to enable on-sky demonstration.

Synthetic guide star generation

DOEpatents

Payne, Stephen A [Castro Valley, CA; Page, Ralph H [Castro Valley, CA; Ebbers, Christopher A [Livermore, CA; Beach, Raymond J [Livermore, CA

2008-06-10

A system for assisting in observing a celestial object and providing synthetic guide star generation. A lasing system provides radiation at a frequency at or near 938 nm and radiation at a frequency at or near 1583 nm. The lasing system includes a fiber laser operating between 880 nm and 960 nm and a fiber laser operating between 1524 nm and 1650 nm. A frequency-conversion system mixes the radiation and generates light at a frequency at or near 589 nm. A system directs the light at a frequency at or near 589 nm toward the celestial object and provides synthetic guide star generation.

Synthetic guide star generation

DOEpatents

Payne, Stephen A.; Page, Ralph H.; Ebbers, Christopher A.; Beach, Raymond J.

2004-03-09

A system for assisting in observing a celestial object and providing synthetic guide star generation. A lasing system provides radiation at a frequency at or near 938 nm and radiation at a frequency at or near 1583 nm. The lasing system includes a fiber laser operating between 880 nm and 960 nm and a fiber laser operating between 1524 nm and 1650 nm. A frequency-conversion system mixes the radiation and generates light at a frequency at or near 589 nm. A system directs the light at a frequency at or near 589 nm toward the celestial object and provides synthetic guide star generation.

Daylight operation of a sodium laser guide star

NASA Astrophysics Data System (ADS)

Hart, Michael; Jefferies, Stuart; Murphy, Neil

2016-07-01

We report photometric measurements of a sodium resonance guide star against the daylight sky when observed through a tuned magneto-optical filter (MOF). The MOF comprises a sodium vapor cell in a kilogauss-level magnetic field between crossed polarizers and has a very narrow transmission profile at the sodium D2 resonance of approximately 0.008 nm. Our observations were made with the 1.5 m Kuiper telescope on Mt. Bigelow, AZ, which has a separately mounted guide star laser projecting a circularly polarized single-frequency beam of approximately 6.5 W at 589.16 nm. Both the beam projector and the 1.5 m telescope were pointed close to zenith; the baseline between them is approximately 5 m. Measurements of the guide star were made on the morning of 2016 March 24 using an imaging camera focused on the beacon and looking through the full aperture of the telescope. The guide star flux was estimated at 1.20×106 photon/m2/s while at approximately 45 minutes after sunrise, the sky background through the MOF was 1100 photon/m2/s/arcsec2. We interpret our results in terms of thermal infrared observations with adaptive optics on the next generation of extremely large telescopes now being built.

Development and implementation of the guiding stars nutrition guidance program.

PubMed

Fischer, Leslie M; Sutherland, Lisa A; Kaley, Lori A; Fox, Tracy A; Hasler, Clare M; Nobel, Jeremy; Kantor, Mark A; Blumberg, Jeffrey

2011-01-01

PURPOSE . To describe the collaborative process between a grocery retailer and a panel of nutrition experts used to develop a nutrition guidance system (Guiding Stars) that evaluates the nutrient profile of all edible products in the supermarket, and to report the results of the food and beverage ratings. DESIGN . A collaboration between a private retailer and members of the scientific community that led to the development of a scoring algorithm used to evaluate the nutritional quality of foods and beverages. SETTING/SUBJECTS . Northeast supermarkets (n  =  160). MEASURES . Food and beverage nutrition ratings and distribution of stars across different grocery categories. ANALYSIS . Descriptive statistics for rating distributions were computed. T-tests were conducted to assess differences in mean nutrient values between foods with zero versus three stars or a dichotomized variable representing all foods with one to three stars. RESULTS . All edible grocery items (n  =  27,466) were evaluated, with 23.6% earning at least one star. Items receiving at least one star had lower mean levels of sodium, saturated fat, and sugars and higher amounts of fiber than products not earning stars. CONCLUSION . The Guiding Stars system rates edible products without regard to brand or manufacturer, and provides consumers with a simple tool to quickly identify more nutritious choices while shopping. The low percentage of products qualifying for stars reflects poorly on the food choices available to Americans.

Improved compensation of atmospheric turbulence effects by multiple adaptive mirror systems.

PubMed

Shamir, J; Crowe, D G; Beletic, J W

1993-08-20

Optical wave-front propagation in a layered model for the atmosphere is analyzed by the use of diffraction theory, leading to a novel approach for utilizing artificial guide stars. Considering recent observations of layering in the atmospheric turbulence, the results of this paper indicate that, even for very large telescopes, a substantial enlargement of the compensated angular field of view is possible when two adaptive mirrors and four or five artificial guide stars are employed. The required number of guide stars increases as the thickness of the turbulent layers increases, converging to the conventional results at the limit of continuously turbulent atmosphere.

Space beam combiner for long-baseline interferometry

NASA Astrophysics Data System (ADS)

Lin, Yao; Bartos, Randall D.; Korechoff, Robert P.; Shaklan, Stuart B.

1999-04-01

An experimental beam combiner (BC) is being developed to support the space interferometry program at the JPL. The beam combine forms the part of an interferometer where star light collected by the sidestats or telescopes is brought together to produce white light fringes, and to provide wavefront tilt information via guiding spots and beam walk information via shear spots. The assembly and alignment of the BC has been completed. The characterization test were performed under laboratory conditions with an artificial star and optical delay line. Part of each input beam was used to perform star tracking. The white light interference fringes were obtained over the selected wavelength range from 450 nm to 850 nm. A least-square fit process was used to analyze the fringe initial phase, fringe visibilities and shift errors of the optical path difference in the delay line using the dispersed white-light fringes at different OPD positions.

Design of an infrared camera based aircraft detection system for laser guide star installations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Friedman, H.; Macintosh, B.

1996-03-05

There have been incidents in which the irradiance resulting from laser guide stars have temporarily blinded pilots or passengers of aircraft. An aircraft detection system based on passive near infrared cameras (instead of active radar) is described in this report.

Optical System Error Analysis and Calibration Method of High-Accuracy Star Trackers

PubMed Central

Sun, Ting; Xing, Fei; You, Zheng

2013-01-01

The star tracker is a high-accuracy attitude measurement device widely used in spacecraft. Its performance depends largely on the precision of the optical system parameters. Therefore, the analysis of the optical system parameter errors and a precise calibration model are crucial to the accuracy of the star tracker. Research in this field is relatively lacking a systematic and universal analysis up to now. This paper proposes in detail an approach for the synthetic error analysis of the star tracker, without the complicated theoretical derivation. This approach can determine the error propagation relationship of the star tracker, and can build intuitively and systematically an error model. The analysis results can be used as a foundation and a guide for the optical design, calibration, and compensation of the star tracker. A calibration experiment is designed and conducted. Excellent calibration results are achieved based on the calibration model. To summarize, the error analysis approach and the calibration method are proved to be adequate and precise, and could provide an important guarantee for the design, manufacture, and measurement of high-accuracy star trackers. PMID:23567527

Laser Guidestar Satellite for Ground-based Adaptive Optics Imaging of Geosynchronous Satellites and Astronomical Targets

NASA Astrophysics Data System (ADS)

Marlow, W. A.; Cahoy, K.; Males, J.; Carlton, A.; Yoon, H.

2015-12-01

Real-time observation and monitoring of geostationary (GEO) satellites with ground-based imaging systems would be an attractive alternative to fielding high cost, long lead, space-based imagers, but ground-based observations are inherently limited by atmospheric turbulence. Adaptive optics (AO) systems are used to help ground telescopes achieve diffraction-limited seeing. AO systems have historically relied on the use of bright natural guide stars or laser guide stars projected on a layer of the upper atmosphere by ground laser systems. There are several challenges with this approach such as the sidereal motion of GEO objects relative to natural guide stars and limitations of ground-based laser guide stars; they cannot be used to correct tip-tilt, they are not point sources, and have finite angular sizes when detected at the receiver. There is a difference between the wavefront error measured using the guide star compared with the target due to cone effect, which also makes it difficult to use a distributed aperture system with a larger baseline to improve resolution. Inspired by previous concepts proposed by A.H. Greenaway, we present using a space-based laser guide starprojected from a satellite orbiting the Earth. We show that a nanosatellite-based guide star system meets the needs for imaging GEO objects using a low power laser even from 36,000 km altitude. Satellite guide star (SGS) systemswould be well above atmospheric turbulence and could provide a small angular size reference source. CubeSatsoffer inexpensive, frequent access to space at a fraction of the cost of traditional systems, and are now being deployed to geostationary orbits and on interplanetary trajectories. The fundamental CubeSat bus unit of 10 cm cubed can be combined in multiple units and offers a common form factor allowing for easy integration as secondary payloads on traditional launches and rapid testing of new technologies on-orbit. We describe a 6U CubeSat SGS measuring 10 cm x 20 cm x 30 cm with laser power on the order of milliwatts, and a commercial off the shelf based attitude determination and control system, among others. Different from standard 1U and 3U buses, the 6U form factor allows for a propulsion system for navigating around multiple targets in the GEO belt.

Star Ware: The Amateur Astronomer's Guide to Choosing, Buying, and Using Telescopes and Accessories, 3rd Edition

NASA Astrophysics Data System (ADS)

Harrington, Philip S.

2002-05-01

Praise for the Second Edition of Star Ware "Star Ware is still a tour de force that any experienced amateur will find invaluable, and which hardware-minded beginners will thoroughly enjoy." -Robert Burnham, Sky & Telescope magazine "Star Ware condenses between two covers what would normally take a telescope buyer many months to accumulate." -John Shibley, Astronomy magazine Now more than ever, the backyard astronomer has a dazzling array of choices when it comes to telescope shopping-which can make choosing just the right sky-watching equipment a formidable challenge. In this revised and updated edition of Star Ware, the essential guide to buying astronomical equipment, award-winning astronomy writer Philip Harrington does the work for you, analyzing and exploring today's astronomy market and offering point-by-point comparisons of everything you need. Whether you're an experienced amateur astronomer or just getting started, Star Ware, Third Edition will prepare you to explore the farthest reaches of space with: Extensive, expanded reviews of leading models and accessories, including dozens of new products, to help you buy smart

Status of ARGOS - The Laser Guide Star System for the LBT

NASA Astrophysics Data System (ADS)

Raab, Walfried; Rabien, Sebastian; Gaessler, Wolfgang; Esposito, Simone; Antichi, Jacopo; Lloyd-Hart, Michael; Barl, Lothar; Beckmann, Udo; Bonaglia, Marco; Borelli, Jose; Brynnel, Joar; Buschkamp, Peter; Busoni, Lorenzo; Carbonaro, Luca; Christou, Julian; Connot, Claus; Davies, Richard; Deysenroth, Matthias; Durney, Olivier; Green, Richard; Gemperlein, Hans; Gasho, Victor; Haug, Marcus; Hubbard, Pete; Ihle, Sebastian; Kulas, Martin; Loose, Christina; Lehmitz, Michael; Noenickx, Jamison; Nussbaum, Edmund; Orban De Xivry, Gilles; Quirrenbach, Andreas; Peter, Diethard; Rahmer, Gustavo; Rademacher, Matt; Storm, Jesper; Schwab, Christian; Vaitheeswaran, Vidhya; Ziegleder, Julian

2013-12-01

ARGOS is an innovative multiple laser guide star adaptive optics system for the Large Binocular Telescope (LBT), designed to perform effective GLAO correction over a very wide field of view. The system is using high powered pulsed green (532 nm) lasers to generate a set of three guide stars above each of the LBT mirrors. The laser beams are launched through a 40 cm telescope and focused at an altitude of 12 km, creating laser beacons by means of Rayleigh scattering. The returning scattered light, primarily sensitive to the turbulences close to the ground, is detected by a gated wavefront sensor system. The derived ground layer correction signals are directly driving the adaptive secondary mirror of the LBT. ARGOS is especially designed for operation with the multiple object spectrograph Luci, which will benefit from both, the improved spatial resolution, as well as the strongly enhanced flux. In addition to the GLAO Rayleigh beacon system, ARGOS was also designed for a possible future upgrade with a hybrid sodium laser - Rayleigh beacon combination, enabling diffraction limited operation. The ARGOS laser system has undergone extensive tests during Summer 2012 and is scheduled for installation at the LBT in Spring 2013. The remaining sub-systems will be installed during the course of 2013. We report on the overall status of the ARGOS system and the results of the sub-system characterizations carried out so far.

Automating individualized coaching and authentic role-play practice for brief intervention training.

PubMed

Hayes-Roth, B; Saker, R; Amano, K

2010-01-01

Brief intervention helps to reduce alcohol abuse, but there is a need for accessible, cost-effective training of clinicians. This study evaluated STAR Workshop , a web-based training system that automates efficacious techniques for individualized coaching and authentic role-play practice. We compared STAR Workshop to a web-based, self-guided e-book and a no-treatment control, for training the Engage for Change (E4C) brief intervention protocol. Subjects were medical and nursing students. Brief written skill probes tested subjects' performance of individual protocol steps, in different clinical scenarios, at three test times: pre-training, post-training, and post-delay (two weeks). Subjects also did live phone interviews with a standardized patient, post-delay. STAR subjects performed significantly better than both other groups. They showed significantly greater improvement from pre-training probes to post-training and post-delay probes. They scored significantly higher on post-delay phone interviews. STAR Workshop appears to be an accessible, cost-effective approach for training students to use the E4C protocol for brief intervention in alcohol abuse. It may also be useful for training other clinical interviewing protocols.

Book Review: Stars (Copyright 1985, Golden Press; New York)

NASA Astrophysics Data System (ADS)

Marigza, R. N., Jr.

2009-06-01

Stars is a part of the Golden Guides collection produced by Golden Press. It is a small 160 page paperback guide to the constellations, the sun, the moon, planets, and other celestial bodies. The book is convenient to carry along wherever you go, making it an easy to access reference material.

Adaptive acoustic energy delivery to near and far fields using foldable, tessellated star transducers

NASA Astrophysics Data System (ADS)

Zou, Chengzhe; Harne, Ryan L.

2017-05-01

Methods of guiding acoustic energy arbitrarily through space have long relied on digital controls to meet performance needs. Yet, more recent attention to adaptive structures with unique spatial configurations has motivated mechanical signal processing (MSP) concepts that may not be subjected to the same functional and performance limitations as digital acoustic beamforming counterparts. The periodicity of repeatable structural reconfiguration enabled by origami-inspired tessellated architectures turns attention to foldable platforms as frameworks for MSP development. This research harnesses principles of MSP to study a tessellated, star-shaped acoustic transducer constituent that provides on-demand control of acoustic energy guiding via folding-induced shape reconfiguration. An analytical framework is established to probe the roles of mechanical and acoustic geometry on the far field directivity and near field focusing of sound energy. Following validation by experiments and verification by simulations, parametric studies are undertaken to uncover relations between constituent topology and acoustic energy delivery to arbitrary points in the free field. The adaptations enabled by folding of the star-shaped transducer reveal capability for restricting sound energy to angular regions in the far field while also introducing means to modulate sound energy by three orders-of-magnitude to locations near to the transducer surface. In addition, the modeling philosophy devised here provides a valuable approach to solve general sound radiation problems for foldable, tessellated acoustic transducer constituents of arbitrary geometry.

Line of Sight Stabilization of James Webb Space Telescope

NASA Technical Reports Server (NTRS)

Meza, Luis; Tung, Frank; Anandakrishnan, Satya; Spector, Victor; Hyde, Tupper

2005-01-01

The James Webb Space Telescope (JWST) builds upon the successful flight experience of the Chandra Xray Telescope by incorporating an additional LOS pointing servo to meet the more stringent pointing requirements. The LOS pointing servo, referred to in JWST as the Fine Guidance Control System (FGCS), will utilize a Fine Guidance Sensor (FGS) as the sensor, and a Fine Steering Mirror (FSM) as the actuator. The FSM is a part of the Optical Telescope Element (OTE) and is in the optical path between the tertiary mirror and the instrument focal plane, while the FGS is part of the Integrated Science Instrument Module (ISIM). The basic Chandra spacecraft bus attitude control and determination architecture, utilizing gyros, star trackers/aspect camera, and reaction wheels, is retained for JWST. This system has achieved pointing stability of better than 0.5 arcseconds. To reach the JWST requirements of milli-arcsecond pointing stability with this ACS hardware, the local FGCS loop is added to the optical path. The FGCS bandwidth is about 2.0 Hz and will therefore attenuate much of the spacecraft ACS induced low frequency jitter. In order to attenuate the higher frequency (greatet than 2.0 Hz) disturbances associated with reaction wheel static and dynamic imbalances, as well as bearing run-out, JWST will employ a two-stage passive vibration isolation system consisting of (1) 7.0 Hz reaction wheel isolators between each reaction wheel and the spacecraft bus, and (2) a 1.0 Hz tower isolator between the spacecraft bus and the Optical Telescope Element (OTE). In order to sense and measure the LOS, the FGS behaves much like an autonomous star tracker that has a very small field of view and uses the optics of the telescope. It performs the functions of acquisition, identification and tracking of stars in its 2.5 x 2.5 arcminute field of view (FOV), and provides the centroid and magnitude of the selected star for use in LOS control. However, since only a single star is being tracked at any time within the FGS FOV there is only tip and tilt information; rotation about the FGS LOS will not be sensed. The FGCS uses the FSM to move the guide star within the FGS FOV and place the centroid of the guide star at any desired position within the FGS focal plane. Using this architecture allows the FGCS to correct the low frequency LOS jitter that is induced by the spacecraft ACS in pitch and yaw, and achieve the milli-arcsecond pointing stability required by JWST. The less stringent ISIM FOV roll performance will be provided solely by the ACS, using the spacecraft gyros and star trackers. Since the FSM is in the optical path, the pointing stabilrty of a science object in any of the instruments will be similar to that of the guide star LOS.

Consumers' Response to an On-Shelf Nutrition Labelling System in Supermarkets: Evidence to Inform Policy and Practice.

PubMed

Hobin, Erin; Bollinger, Bryan; Sacco, Jocelyn; Liebman, Eli; Vanderlee, Lana; Zuo, Fei; Rosella, Laura; L'abbe, Mary; Manson, Heather; Hammond, David

2017-09-01

Policy Points: On-shelf nutrition labelling systems in supermarkets, such as the Guiding Stars system, are intended to provide consumers with simple, standardized nutrition information to support more informed and healthier food choices. Policies that support the provision of simplified nutrition labelling systems may encourage consumers to make positive shifts in food-purchasing behaviors. The shifts in consumer food-purchasing patterns observed in our study after the introduction of the Guiding Stars system in supermarkets translated into measurable nutritional benefits, including more items purchased with slightly less trans fat and sugar and more fiber and omega-3 fatty acids. This study is one of the first to report the positive impact of an on-shelf nutrition labelling system on supermarket sales and revenues-key information that was specifically requested by the US National Academies, as such labelling interventions may be more sustainable if they lead to higher revenues. Providing a nutrition rating system on the front of food packages or on retail shelf tags has been proposed as a policy strategy for supporting healthier food choices. Guiding Stars is an on-shelf nutrition labelling system that scores foods in a supermarket based on nutritional quality; scores are then translated into ratings of 0 to 3 stars. It is consistent with evidence-informed recommendations for well-designed labels, except for not labelling 0-star products. The largest supermarket retailer in Canada rolled out the Guiding Stars system in supermarkets across Ontario, Canada. The aim of our study was to examine the extent to which consumers respond to an on-shelf nutrition labelling system in supermarkets to inform current and future nutrition labelling policies and practices. Capitalizing on a natural experiment, we conducted a quasi-experimental study across 3 supermarket banners (or "chains") in Ontario, one of which implemented the Guiding Stars system in 2012. We used aggregated supermarket transaction data to test the effect of Guiding Stars on the nutritional quality of food purchases in intervention supermarkets relative to control supermarkets. We also conducted exit surveys among 783 randomly selected shoppers from intervention and control supermarkets to assess consumer awareness, understanding, trust, and self-reported use of the labelling system. Relative to control supermarkets, shoppers in intervention supermarkets made small but significant shifts toward purchasing foods with higher nutritional ratings; however, shifts varied in direction and magnitude across food categories. These shifts translated into foods being purchased with slightly less trans fat and sugar and more fiber and omega-3 fatty acids. We also found increases in the number of products per transaction, price per product purchased, and total revenues. Results of the exit surveys indicate a modest proportion of consumers were aware of, understood, and trusted Guiding Stars in intervention supermarkets, and a small proportion of consumers reported using this system when making purchasing decisions. However, 47% of shoppers exposed to Guiding Stars were confused when asked to interpret the meaning of a 0-star product that does not display a rating on the shelf tag. This study demonstrates support for policies promoting on-shelf nutrition labels designed according to evidence-informed principles, but policymakers should move forward with caution when investing in such systems until research has confirmed optimal label design, clarified the mechanisms through which dietary intake is improved, and assessed associations with nutrition-related health outcomes. © 2017 Milbank Memorial Fund.

Man-made Star Shines in the Southern Sky

NASA Astrophysics Data System (ADS)

2006-02-01

Scientists celebrate another major milestone at Cerro Paranal in Chile, home of ESO's Very Large Telescope array. Thanks to their dedicated efforts, they were able to create the first artificial star in the Southern Hemisphere, allowing astronomers to study the Universe in the finest detail. This artificial laser guide star makes it possible to apply adaptive optics systems, that counteract the blurring effect of the atmosphere, almost anywhere in the sky. ESO PR Photo 07a/06 ESO PR Photo 07a/06 First Light of the VLT Laser Guide Star On 28 January 2006, at 23:07 local time, a laser beam of several watts was launched from Yepun, the fourth 8.2m Unit Telescope of the Very Large Telescope, producing an artificial star, 90 km up in the atmosphere. Despite this star being about 20 times fainter than the faintest star that can be seen with the unaided eye, it is bright enough for the adaptive optics to measure and correct the atmosphere's blurring effect. The event was greeted with much enthusiasm and happiness by the people in the control room of one of the most advanced astronomical facilities in the world. It was the culmination of five years of collaborative work by a team of scientists and engineers from ESO and the Max Planck Institutes for Extraterrestrial Physics in Garching and for Astronomy in Heidelberg, Germany. After more than one month of integration on site with the invaluable support of the Paranal Observatory staff, the VLT Laser Guide Star Facility saw First Light and propagated into the sky a 50cm wide, vivid, beautifully yellow beam. ESO PR Photo 07b/06 ESO PR Photo 07b/06 An Artificial Star Above Paranal "This event tonight marks the beginning of the Laser Guide Star Adaptive Optics era for ESO's present and future telescopes", said Domenico Bonaccini Calia, Head of the Laser Guide Star group at ESO and LGSF Project Manager. Normally, the achievable image sharpness of a ground-based telescope is limited by the effect of atmospheric turbulence. This drawback can be surmounted with adaptive optics, allowing the telescope to produce images that are as sharp as if taken from space. This means that finer details in astronomical objects can be studied, and also that fainter objects can be observed. In order to work, adaptive optics needs a nearby reference star that has to be relatively bright, thereby limiting the area of the sky that can be surveyed. To overcome this limitation, astronomers use a powerful laser that creates an artificial star, where and when they need it. ESO PR Photo 07c/06 ESO PR Photo 07c/06 The Laser Guide Star Laboratory The laser beam, shining at a well-defined wavelength, makes the layer of sodium atoms that is present in Earth's atmosphere at an altitude of 90 kilometres glow. The laser is hosted in a dedicated laboratory under the platform of Yepun. A custom-made fibre carries the high power laser to the launch telescope situated on top of the large Unit Telescope. An intense and exhilarating twelve days of tests followed the First Light of the Laser Guide Star (LGS), during which the LGS was used to improve the resolution of astronomical images obtained with the two adaptive optics instruments in use on Yepun: the NAOS-CONICA imager and the SINFONI spectrograph. In the early hours of 9 February, the LGS could be used together with the SINFONI instrument, while in the early morning of 10 February, it was with the NAOS-CONICA system. ESO PR Video 07/06 ESO PR Video 07/06 Learn more with the video! "To have succeeded in such a short time is an outstanding feat and is a tribute to all those who have together worked so hard over the last few years," said Richard Davies, project manager for the laser source development at the Max Planck Institute for Extraterrestrial Physics. A second phase of commissioning will take place in the spring with the aim of optimizing the operations and refining the performances before the instrument is made available to the astronomers, later this year. The experience gained with this Laser Guide Star is also a key milestone in the design of the next generation of Extremely Large Telescope in the 30 to 60 metre range that is now being studied by ESO together with the European astronomical community. High resolution images and their captions are available on this page. This press release is also accompanied by Broadcast quality material. Notes The Laser Guide Star Facility is a collaborative project between ESO, the Max Planck Institute for Extraterrestrial Physics in Garching, Germany (MPE) and the Max Planck Institut for Astronomy in Heidelberg, Germany (MPIA). The team members are D. Bonaccini Calia, W. Hackenberg, M. Cullum, M. Dimmler, I. Guidolin, C. Araujo, E. Allaert, D. Popovic, M. Comin, M. Quattri, E. Brunetto, F. Koch, A. Silber, J-L. Alvarez, M. Tapia, E. Bendek, J. Quentin, G. Fischer, M. Tarenghi, G.Monnet, and R.Gilmozzi (ESO), R. Davies, S. Rabien, T. Ott, R. Genzel, S.Kellner, S. Huber, W. Zaglauer, A. Goldbrunner, and J. Li (MPE), and S. Hippler, U. Neumann, D. Butler, R.-R. Rohloff, and B.Grimm (MPIA). Members of ESO's Adaptive Optics team also participated to First Light: M. Kasper, S. Stroebele, E. Fedrigo, R. Donaldson, S. Oberti, and C. Soenke. This press release is issued in coordination between ESO and the Max Planck Society. A German version is available at http://www.mpg.de/bilderBerichteDokumente/dokumentation/pressemitteilungen/2006/

America's Star Libraries

ERIC Educational Resources Information Center

Lyons, Ray; Lance, Keith Curry

2009-01-01

"Library Journal"'s new national rating of public libraries, the "LJ" Index of Public Library Service, identifies 256 "star" libraries. It rates 7,115 public libraries. The top libraries in each group get five, four, or three Michelin guide-like stars. All included libraries, stars or not, can use their scores to learn from their peers and improve…

Live imaging using adaptive optics with fluorescent protein guide-stars

PubMed Central

Tao, Xiaodong; Crest, Justin; Kotadia, Shaila; Azucena, Oscar; Chen, Diana C.; Sullivan, William; Kubby, Joel

2012-01-01

Spatially and temporally dependent optical aberrations induced by the inhomogeneous refractive index of live samples limit the resolution of live dynamic imaging. We introduce an adaptive optical microscope with a direct wavefront sensing method using a Shack-Hartmann wavefront sensor and fluorescent protein guide-stars for live imaging. The results of imaging Drosophila embryos demonstrate its ability to correct aberrations and achieve near diffraction limited images of medial sections of large Drosophila embryos. GFP-polo labeled centrosomes can be observed clearly after correction but cannot be observed before correction. Four dimensional time lapse images are achieved with the correction of dynamic aberrations. These studies also demonstrate that the GFP-tagged centrosome proteins, Polo and Cnn, serve as excellent biological guide-stars for adaptive optics based microscopy. PMID:22772285

Effects of laser beam propagation and saturation on the spatial shape of sodium laser guide stars.

PubMed

Marc, Fabien; Guillet de Chatellus, Hugues; Pique, Jean-Paul

2009-03-30

The possibility to produce diffraction-limited images by large telescopes through Adaptive Optics is closely linked to the precision of measurement of the position of the guide star on the wavefront sensor. In the case of laser guide stars, many parameters can lead to a strong distortion on the shape of the LGS spot. Here we study the influence of both the saturation of the sodium layer excited by different types of lasers, the spatial quality of the laser mode at the ground and the influence of the atmospheric turbulence on the upward propagation of the laser beam. Both shape and intensity of the LGS spot are found to depend strongly on these three effects with important consequences on the precision on the wavefront analysis.

Improving sodium laser guide star brightness by polarization switching

PubMed Central

Fan, Tingwei; Zhou, Tianhua; Feng, Yan

2016-01-01

Optical pumping with circularly polarized light has been used to enhance the brightness of sodium laser guide star. But the benefit is reduced substantially due to the precession of sodium atoms in geomagnetic field. Switching the laser between left and right circular polarization at the Larmor frequency is proposed to improve the return. With ESO’s laser guide star system at Paranal as example, numerical simulation shows that the return flux is increased when the angle between geomagnetic field and laser beam is larger than 60°, as much as 50% at 90°. The proposal is significant since most astronomical observation is at angle between 60° and 90° and it only requires a minor addition to the delivery optics of present laser system. PMID:26797503

Status and new developments with the Keck I near-infrared tip-tilt sensor

NASA Astrophysics Data System (ADS)

Femenía Castellá, Bruno; Wizinowich, Peter; Rampy, Rachel; Cetre, Sylvain; Lilley, Scott; Lyke, Jim; Ragland, Sam; Stomski, Paul; van Dam, Marcos

2016-07-01

The sky coverage and performance of Laser Guide Star (LGS) adaptive optics (AO) systems is limited by the Natural Guide Star (NGS) used for low order correction (tip-tilt and defocus modes). This limitation can be reduced by measuring image motion of the NGS in the near-infrared where it is partially corrected by the LGS AO system and where stars are generally several magnitudes brighter than at visible wavelengths. We have integrated a Near-InfraRed Tip-Tilt Sensor (NIRTTS) with the Keck I telescopes LGS AO system. The sensor is a H2RG-based near-infrared camera with 0.05 arcsecond pixels. Low noise at high sample rates is achieved by only reading a small region of interest, from 2x2 to 16x16 pixels, centered on an NGS anywhere in an 100 arc second diameter field. The sensor operates at either Ks or H-band using light reflected by a choice of dichroic beam-splitters located in front of the OSIRIS integral field spectrograph. The implementation of the NIRTTS involved modifications to the AO bench, real-time control system, higher-level controls and operations software. NIRTTS is nearly ready for science operation in shared-risk mode. We are also implementing a number of enhancements to the NIRTTS system which involve substantial changes to the operations software. This work presents an update of the work performed since the NIRTTS system was reported in Ref. 1 and Ref. 2.

Rocket instrument for far-UV spectrophotometry of faint astronomical objects.

PubMed

Hartig, G F; Fastie, W G; Davidsen, A F

1980-03-01

A sensitive sounding rocket instrument for moderate (~10-A) resolution far-UV (lambda1160-lambda1750-A) spectrophotometry of faint astronomical objects has been developed. The instrument employs a photon-counting microchannel plate imaging detector and a concave grating spectrograph behind a 40-cm Dall-Kirkham telescope. A unique remote-control pointing system, incorporating an SIT vidicon aspect camera, two star trackers, and a tone-encoded command telemetry link, permits the telescope to be oriented to within 5 arc sec of any target for which suitable guide stars can be found. The design, construction, calibration, and flight performance of the instrument are discussed.

Femtosecond Amplifiers and Microlasers in the Deep Ultraviolet

DTIC Science & Technology

2013-11-19

Laser guide stars have applications of growing importance to the DOD, astronomy, and environmental monitoring. However, realizing a laser that is...pump wavelength, photoassociation-pumped lasers hold considerable promise as guide star lasers . The most exciting aspect of these results, however...highlights of several experiments that were mentioned briefly in the last section. A. Dual Wavelength Sodium Laser Pumped By Na-Xe Pair Absorption

High Resolution Imaging Testbed Utilizing Sodium Laser Guide Star Adaptive Optics: The Real Time Wavefront Reconstructor Computer

DTIC Science & Technology

2008-07-31

Unlike the Lyrtech, each DSP on a Bittware board offers 3 MB of on-chip memory and 3 GFLOPs of 32-bit peak processing power. Based on the performance...Each NVIDIA 8800 Ultra features 576 GFLOPS on 128 612-MHz single-precision floating-point SIMD processors, arranged in 16 clusters of eight. Each

Laser guide star wavefront sensing for ground-layer adaptive optics on extremely large telescopes.

PubMed

Clare, Richard M; Le Louarn, Miska; Béchet, Clementine

2011-02-01

We propose ground-layer adaptive optics (GLAO) to improve the seeing on the 42 m European Extremely Large Telescope. Shack-Hartmann wavefront sensors (WFSs) with laser guide stars (LGSs) will experience significant spot elongation due to off-axis observation. This spot elongation influences the design of the laser launch location, laser power, WFS detector, and centroiding algorithm for LGS GLAO on an extremely large telescope. We show, using end-to-end numerical simulations, that with a noise-weighted matrix-vector-multiply reconstructor, the performance in terms of 50% ensquared energy (EE) of the side and central launch of the lasers is equivalent, the matched filter and weighted center of gravity centroiding algorithms are the most promising, and approximately 10×10 undersampled pixels are optimal. Significant improvement in the 50% EE can be observed with a few tens of photons/subaperture/frame, and no significant gain is seen by adding more than 200 photons/subaperture/frame. The LGS GLAO is not particularly sensitive to the sodium profile present in the mesosphere nor to a short-timescale (less than 100 s) evolution of the sodium profile. The performance of LGS GLAO is, however, sensitive to the atmospheric turbulence profile.

MagAO: status and science

NASA Astrophysics Data System (ADS)

Morzinski, Katie M.; Close, Laird M.; Males, Jared R.; Hinz, Phil M.; Esposito, Simone; Riccardi, Armando; Briguglio, Runa; Follette, Katherine B.; Pinna, Enrico; Puglisi, Alfio; Vezilj, Jennifer; Xompero, Marco; Wu, Ya-Lin

2016-07-01

"MagAO" is the adaptive optics instrument at the Magellan Clay telescope at Las Campanas Observatory, Chile. MagAO has a 585-actuator adaptive secondary mirror and 1000-Hz pyramid wavefront sensor, operating on natural guide stars from R-magnitudes of -1 to 15. MagAO has been in on-sky operation for 166 nights since installation in 2012. MagAO's unique capabilities are simultaneous imaging in the visible and infrared with VisAO and Clio, excellent performance at an excellent site, and a lean operations model. Science results from MagAO include the first ground-based CCD image of an exoplanet, demonstration of the first accreting protoplanets, discovery of a new wide-orbit exoplanet, and the first empirical bolometric luminosity of an exoplanet. We describe the status, report the AO performance, and summarize the science results. New developments reported here include color corrections on red guide stars for the wavefront sensor; a new field stop stage to facilitate VisAO imaging of extended sources; and eyepiece observing at the visible-light diffraction limit of a 6.5-m telescope. We also discuss a recent hose failure that led to a glycol coolant leak, and the recovery of the adaptive secondary mirror (ASM) after this recent (Feb. 2016) incident.

Series production of next-generation guide-star lasers at TOPTICA and MPBC

NASA Astrophysics Data System (ADS)

Enderlein, Martin; Friedenauer, Axel; Schwerdt, Robin; Rehme, Paul; Wei, Daoping; Karpov, Vladimir; Ernstberger, Bernhard; Leisching, Patrick; Clements, Wallace R. L.; Kaenders, Wilhelm G.

2014-07-01

Large telescopes equipped with adaptive optics require high power 589-nm continuous-wave sources with emission linewidths of ~5 MHz. These guide-star lasers should be highly reliable and simple to operate and maintain for many years at the top of a mountain facility. After delivery of the first 20-W systems to our lead customer ESO, TOPTICA and MPBC have begun series production of next-generation sodium guide-star lasers. The chosen approach is based on ESO's patented narrow-band Raman fiber amplifier (RFA) technology [1]. A master oscillator signal from a TOPTICA 50-mW, 1178-nm diode laser, with stabilized emission frequency and linewidth of ~ 1 MHz, is amplified in an MPBC polarization-maintaining (PM) RFA pumped by a high-power 1120-nm PM fiber laser. With efficient stimulated Brillouin scattering suppression, an unprecedented 40 W of narrow-band RFA output has been obtained. This is spatially mode-matched into a patented resonant-cavity frequency doubler providing also the repumper light [2]. With a diffraction-limited output beam and doubling efficiencies < 80%, all ESO design goals have been easily fulfilled. Together with a wall-plug efficiency of < 3%, including all system controls, and a cooling liquid flow of only 5 l/min, the modular, turn-key, maintenance-free and compact system design allows a direct integration with a launch telescope. With these fiber-based guide star lasers, TOPTICA for the first time offers a fully engineered, off-the-shelf guide star laser system for ground-based optical telescopes. Here we present a comparison of test results of the first batch of laser systems, demonstrating the reproducibility of excellent optical characteristics.

Smart tissue anastomosis robot (STAR): a vision-guided robotics system for laparoscopic suturing.

PubMed

Leonard, Simon; Wu, Kyle L; Kim, Yonjae; Krieger, Axel; Kim, Peter C W

2014-04-01

This paper introduces the smart tissue anastomosis robot (STAR). Currently, the STAR is a proof-of-concept for a vision-guided robotic system featuring an actuated laparoscopic suturing tool capable of executing running sutures from image-based commands. The STAR tool is designed around a commercially available laparoscopic suturing tool that is attached to a custom-made motor stage and the STAR supervisory control architecture that enables a surgeon to select and track incisions and the placement of stitches. The STAR supervisory-control interface provides two modes: A manual mode that enables a surgeon to specify the placement of each stitch and an automatic mode that automatically computes equally-spaced stitches based on an incision contour. Our experiments on planar phantoms demonstrate that the STAR in either mode is more accurate, up to four times more consistent and five times faster than surgeons using state-of-the-art robotic surgical system, four times faster than surgeons using manual Endo360(°)®, and nine times faster than surgeons using manual laparoscopic tools.

The Polychromatic Laser Guide Star for tilt measurement: progress report of the demonstrator at Observatoire de Haute Provence

NASA Astrophysics Data System (ADS)

Foy, Renaud; Éric, Pierre; Eysseric, Jérôme; Foy, Françoise; Fusco, Thierry; Girard, Julien; Le Van Suu, Auguste; Perruchot, Sandrine; Richaud, Pierre; Richaud, Yoann; Rondeau, Xavier; Tallon, Michel; Thiébaut, Éric; Boër, Michel

2007-09-01

The Polychromatic Laser Guide Star aims at providing for the tilt measurement from a LGS without any natural guide star. Thus it allows adaptive optics to provide us with a full sky coverage. This is critical in particular to extend adaptive optics to the visible range, where isoplanatism is so small that the probability is negligible to find a natural star to measure the tilt. We report new results obtained within the framework of the Polychromatic LGS programme ELP-OA. Natural stars have been used to mimic the PLGS, in order to check the feasibility of using the difference in the tilt at two wavelengths to derive the tilt itself. We report results from the ATTILA experiment obtained at the 1.52 m telescope at Observatoire de Haute-Provence. Tilts derived from the differential tilts are compared with direct tilt measurements. The accuracy of the measurements is currently ~ 1.5 Airy disk rms at 550 nm. These results prove the feasibility of the Polychromatic Laser Guide Star programme ELP-OA. New algorithms based on inverse problems under development within our programme would lead to smaller error bars by 1 magnitude, as soon as they will run fast enough. We describe the ELP-OA demonstrator which we are setting up at the same telescope, with a special emphasis on the optimization of the excitation process, which definitely has to rely on the two-photon excitation of sodium atoms in the mesosphere. We will describe the implementation at the telescope, including the projector device, the focal instrumentation and the NdYAG pumped dye lasers.

Interactive Astronomy.

ERIC Educational Resources Information Center

Martin, Jean K.

1997-01-01

Presents guiding principles for developing interactive lessons for the World Wide Web. Describes "Amazing Space: Education Online from the Hubble Space Telescope", a program where students study spectacular Hubble Space Telescope images of stars and star-forming regions to learn about the life cycle of stars and the creation of atoms. (JRH)

A novel double fine guide sensor design on space telescope

NASA Astrophysics Data System (ADS)

Zhang, Xu-xu; Yin, Da-yi

2018-02-01

To get high precision attitude for space telescope, a double marginal FOV (field of view) FGS (Fine Guide Sensor) is proposed. It is composed of two large area APS CMOS sensors and both share the same lens in main light of sight. More star vectors can be get by two FGS and be used for high precision attitude determination. To improve star identification speed, the vector cross product in inter-star angles for small marginal FOV different from traditional way is elaborated and parallel processing method is applied to pyramid algorithm. The star vectors from two sensors are then used to attitude fusion with traditional QUEST algorithm. The simulation results show that the system can get high accuracy three axis attitudes and the scheme is feasibility.

Stellar Ideas: Exploring Students' Understanding of Stars

ERIC Educational Resources Information Center

Agan, Lori

2004-01-01

In this study, high school and first-year undergraduate students were asked about their understanding of stars. The hypothesis guiding this research posits that high school students who have taken a semester-long astronomy course will have an understanding of stars most related to scientific knowledge, compared with high school students enrolled…

Design and construction of a multiple beam laser projector and dynamically refocused wavefront sensor

NASA Astrophysics Data System (ADS)

Stalcup, Thomas Eugene, Jr.

Adaptive optics using natural guide stars can produce images of amazing quality, but is limited to a small fraction of the sky due to the need for a relatively bright guidestar. Adaptive optics systems using a laser generated artificial reference can be used over a majority of the sky, but these systems have some attendant problems. These problems can be reduced by increasing the altitude of the laser return, and indeed a simple, single laser source focused at an altitude of 95 km on a layer of atmospheric sodium performs well for the current generation of 8--10 m telescopes. For future giant telescopes in the 20--30 m class, however, the errors due to incorrect atmospheric sampling and spot elongation will prohibit such a simple system from working. The system presented in this dissertation provides a solution to these problems. Not only does it provide the 6.5m MMT with a relatively inexpensive laser guide star system with unique capabilities, it allows research into solving many of the problems faced by laser guide star systems on future giant telescopes. The MMT laser guidestar system projects a constellation of five doubled Nd:YAG laser beams focused at a mean height of 25 km, with a dynamic refocus system that corrects for spot elongation and allows integrating the return from a 10 km long range gate. It has produced seeing limited spot sizes in ˜1 arcsecond seeing conditions, and has enabled the first on-sky results of Ground Layer Adaptive Optics (GLAO).

Attitude ground support system for the solar maximum mission spacecraft

NASA Technical Reports Server (NTRS)

Nair, G.

1980-01-01

The SMM attitude ground support system (AGSS) supports the acquisition of spacecraft roll attitude reference, performs the in-flight calibration of the attitude sensor complement, supports onboard control autonomy via onboard computer data base updates, and monitors onboard computer (OBC) performance. Initial roll attitude acquisition is accomplished by obtaining a coarse 3 axis attitude estimate from magnetometer and Sun sensor data and subsequently refining it by processing data from the fixed head star trackers. In-flight calibration of the attitude sensor complement is achieved by processing data from a series of slew maneuvers designed to maximize the observability and accuracy of the appropriate alignments and biases. To ensure autonomy of spacecraft operation, the AGSS selects guide stars and computes sensor occultation information for uplink to the OBC. The onboard attitude control performance is monitored on the ground through periodic attitude determination and processing of OBC data in downlink telemetry. In general, the control performance has met mission requirements. However, software and hardware problems have resulted in sporadic attitude reference losses.

DOE Office of Scientific and Technical Information (OSTI.GOV)

None

The Building America team NorthernSTAR investigated opportunities to use the massive customer networks of the home service industry as a means to connect homeowners to home-performance solutions. Home service companies could provide a pathway to advance building-science-guided upgrades by being in close proximity to homeowners when a decision-making moment is at hand. Established trust provides an opportunity for the company to deliver sound information and influence during a remodeling decision.

National Military Family Association

MedlinePlus

... Action Volunteer Mark Your Calendar Donate Twitter Facebook Instagram Donate Appreciating Military Families: Meet the Wilsons This ... 2017 - National Military Family Association Twitter Facebook Pinterest Instagram Charity Navigator Four Star Charity GuideStar Exchange Better ...

First photometric properties of Dome C, Antarctica

NASA Astrophysics Data System (ADS)

Chadid, M.; Vernin, J.; Jeanneaux, F.; Mekarnia, D.; Trinquet, H.

2008-07-01

Here we present the first photometric extinction measurements in the visible range performed at Dome C in Antarctica, using PAIX photometer (Photometer AntarctIca eXtinction). It is made with "off the shelf" components, Audine camera at the focus of Blazhko telescope, a Meade M16 diaphragmed down to 15 cm. For an exposure time of 60 s without filter, a 10th V-magnitude star is measured with a precision of 1/100 mag. A first statistics over 16 nights in August 2007 leads to a 0.5 magnitude per air mass extinction, may be due to high altitude cirrus. This rather simple experiment shows that continuous observations can be performed at Dome C, allowing high frequency resolution on pulsation and asteroseismology studies. Light curves of one of RR Lyrae stars: SAra were established. They show the typical trend of a RRLyrae star. A recent sophisticated photometer, PAIX II, has been installed recently at Dome C during polar summer 2008, with a ST10 XME camera, automatic guiding, auto focusing and Johnson/Bessel UBVRI filter wheels.

A search for stellar occultations by Uranus, Neptune, Pluto, and their satellites: 1990-1999

NASA Technical Reports Server (NTRS)

Mink, Douglas J.

1991-01-01

A search for occultations of stars by Uranus, Neptune, and Pluto between 1990 and 1999 was carried out by combining ephemeris information and star positions using very accurate occultation modeling software. Stars from both the Space Telescope Guide Catalog and photographic plates taken by Arnold Klemola at Lick Observatory were compared with planet positions from the JPL DE-130 ephemeris, with local modifications for Pluto and Charon. Some 666 possible occultations by the Uranian ring, 143 possible occultations by Neptune, and 40 possible occultations by Pluto and/or Charon were found among stars with visual magnitudes as faint as 16. Before the star positions could be obtained, the occultation prediction software was used to aid many observers in observing the occultation of 28 Sagitarii by Saturn in July 1989. As a test on other outer solar system objects, 17 possible occultations were found in a search of the Guide Star Catalog for occultations by 2060 Chiron, and interesting object between Saturn and Uranus which shows both cometary and asteroidal properties.

A search for stellar occultations by Uranus, Neptune, Pluto, and their satellites: 1990-1999

NASA Astrophysics Data System (ADS)

Mink, Douglas J.

1991-03-01

A search for occultations of stars by Uranus, Neptune, and Pluto between 1990 and 1999 was carried out by combining ephemeris information and star positions using very accurate occultation modeling software. Stars from both the Space Telescope Guide Catalog and photographic plates taken by Arnold Klemola at Lick Observatory were compared with planet positions from the JPL DE-130 ephemeris, with local modifications for Pluto and Charon. Some 666 possible occultations by the Uranian ring, 143 possible occultations by Neptune, and 40 possible occultations by Pluto and/or Charon were found among stars with visual magnitudes as faint as 16. Before the star positions could be obtained, the occultation prediction software was used to aid many observers in observing the occultation of 28 Sagitarii by Saturn in July 1989. As a test on other outer solar system objects, 17 possible occultations were found in a search of the Guide Star Catalog for occultations by 2060 Chiron, and interesting object between Saturn and Uranus which shows both cometary and asteroidal properties.

Laser guide stars for optical free-space communications

NASA Astrophysics Data System (ADS)

Mata-Calvo, Ramon; Bonaccini Calia, Domenico; Barrios, Ricardo; Centrone, Mauro; Giggenbach, Dirk; Lombardi, Gianluca; Becker, Peter; Zayer, Igor

2017-02-01

The German Aerospace Center (DLR) and the European Southern Observatory (ESO) performed a measurement campaign together in April and July 2016 at Teide-Observatory (Tenerife), with the support of the European Space Agency (ESA), to investigate the use of laser guide stars (LGS) in ground to space optical communications. Atmospheric turbulence causes strong signal fluctuations in the uplink, due to scintillation and beam wander. In space communications, the use of the downlink channel as reference for pointing and for pre-distortion adaptive optics is limited by the size of the isokinetic and isoplanatic angle in relation to the required point-ahead angle. Pointing and phase errors due to the decorrelation between downward and upward beam due to the point-ahead angle may have a severe impact on the required transmit power and the stability of the communications link. LGSs provide a self-tailored reference to any optical ground-to-space link, independently of turbulence conditions and required point-ahead angle. In photon-starved links, typically in deep-space scenarios, LGSs allow dedicating all downlink received signal to communications purposes, increasing the available link margin. The scope of the joint DLR-ESO measurement campaign was, first, to measure the absolute value of the beam wander (uplink-tilt) using a LGS, taking a natural star as a reference, and, second, to characterize the decrease of correlation between uplink-tilt and downlink-tilt with respect to the angular separation between both sources. This paper describes the experiments performed during the measurement campaigns, providing an overview of the measured data and the first outcomes of the data post-processing.

A tip/tilt mirror with large dynamic range for the ESO VLT Four Laser Guide Star Facility

NASA Astrophysics Data System (ADS)

Rijnveld, N.; Henselmans, R.; Nijland, B.

2011-09-01

One of the critical elements in the Four Laser Guide Star Facility (4LGSF) for the ESO Very Large Telescope (VLT) is the Optical Tube Assembly (OTA), consisting of a stable 20x laser beam expander and an active tip/tilt mirror, the Field Selector Mechanism (FSM). This paper describes the design and performance testing of the FSM. The driving requirement for the FSM is its large stroke of +/-6.1 mrad, in combination with less than 1.5 μrad RMS absolute accuracy. The FSM design consists of a Zerodur mirror, bonded to a membrane spring and strut combination to allow only tip and tilt. Two spindle drives actuate the mirror, using a stiffness based transmission to increase resolution. Absolute accuracy is achieved with two differential inductive sensor pairs. A prototype of the FSM is realized to optimize the control configuration and measure its performance. Friction in the spindle drive is overcome by creating a local velocity control loop between the spindle drives and the shaft encoders. Accuracy is achieved by using a cascaded low bandwidth control loop with feedback from the inductive sensors. The pointing jitter and settling time of the FSM are measured with an autocollimator. The system performance meets the strict requirements, and is ready to be implemented in the first OTA.

STAR (Simple Tool for Automated Reasoning): Tutorial guide and reference manual

NASA Technical Reports Server (NTRS)

Borchardt, G. C.

1985-01-01

STAR is an interactive, interpreted programming language for the development and operation of Artificial Intelligence application systems. The language is intended for use primarily in the development of software application systems which rely on a combination of symbolic processing, central to the vast majority of AI algorithms, with routines and data structures defined in compiled languages such as C, FORTRAN and PASCAL. References to routines and data structures defined in compiled languages are intermixed with symbolic structures in STAR, resulting in a hybrid operating environment in which symbolic and non-symbolic processing and organization of data may interact to a high degree within the execution of particular application systems. The STAR language was developed in the course of a project involving AI techniques in the interpretation of imaging spectrometer data and is derived in part from a previous language called CLIP. The interpreter for STAR is implemented as a program defined in the language C and has been made available for distribution in source code form through NASA's Computer Software Management and Information Center (COSMIC). Contained within this report are the STAR Tutorial Guide, which introduces the language in a step-by-step manner, and the STAR Reference Manual, which provides a detailed summary of the features of STAR.

Laser-sodium interaction for the polychromatic laser guide star project

NASA Astrophysics Data System (ADS)

Bellanger, Veronique; Petit, Alain D.

2002-02-01

We developed a code aimed at determining the laser parameters leading to the maximum return flux of photons at 0.33 micrometers for a polychromatic sodium Laser Guide Star. This software relies upon a full 48-level collisionless and magnetic-field-free density-matrix description of the hyperfine structure of Na and includes Doppler broadening and Zeeman degeneracy. Experimental validation of BEACON was conducted on the SILVA facilities and will also be discussed in this paper.

Direct wavefront sensing for high-resolution in vivo imaging in scattering tissue

PubMed Central

Wang, Kai; Sun, Wenzhi; Richie, Christopher T.; Harvey, Brandon K.; Betzig, Eric; Ji, Na

2015-01-01

Adaptive optics by direct imaging of the wavefront distortions of a laser-induced guide star has long been used in astronomy, and more recently in microscopy to compensate for aberrations in transparent specimens. Here we extend this approach to tissues that strongly scatter visible light by exploiting the reduced scattering of near-infrared guide stars. The method enables in vivo two-photon morphological and functional imaging down to 700 μm inside the mouse brain. PMID:26073070

Vanguard Preparatory School Observations of the Double Star STF 1692

NASA Astrophysics Data System (ADS)

Anderson, Serenity; Buccola, Breck; Garcia, Karen; Gosney, Matthew; Housatchenko, Jonathan; Martinez, Lilian; Myskow, Wyatt; Renteria, Noah; Schlosser, Ruth; Thompson, Leone; Estrada, Reed; Estrada, Chris

2016-01-01

Using a 22-inch Newtonian Alt/Az telescope and a Celestron Micro Guide eyepiece, students from Vanguard Preparatory observed the binary star Cor Caroli (STF 1692) and found a position angle of 228 degrees as well as an average separation of 21.10". This project was a part of the Vanguard Preparatory Double Star Workshop 2015 in Apple Valley, California.

Star Watch: The Amateur Astronomer's Guide to Finding, Observing, and Learning about Over 125 Celestial Objects

NASA Astrophysics Data System (ADS)

Harrington, Philip S.

2003-07-01

Your Passport to the Universe The night sky is alive with many wonders--distant planets, vast star clusters, glowing nebulae, and expansive galaxies, all waiting to be explored. Let respected astronomy writer Philip Harrington introduce you to the universe in Star Watch, a complete beginner's guide to locating, observing, and understanding these celestial objects. You'll start by identifying the surface features of the Moon, the banded cloud tops of Jupiter, the stunning rings of Saturn, and other members of our solar system. Then you'll venture out beyond our solar system, where you'll learn tips and tricks for finding outstanding deep-sky objects from stars to galaxies, including the entire Messier catalog--a primary goal of every serious beginner. Star Watch features a detailed physical description of each target, including size, distance, and structure, as well as concise directions for locating the objects, handy finder charts, hints on the best times to view each object, and descriptions of what you'll really see through a small telescope or binoculars and with the naked eye. Star Watch will transport you to the farthest depths of space--and return you as a well-traveled, experienced stargazer.

Design constraints of the LST fine guidance sensor

NASA Technical Reports Server (NTRS)

Wissinger, A. B.

1975-01-01

The LST Fine Guidance Sensor design is shaped by the rate of occurrence of suitable guide stars, the competition for telescope focal plane space with the Science Instruments, and the sensitivity of candidate image motion sensors. The relationship between these parameters is presented, and sensitivity to faint stars is shown to be of prime importance. An interferometric technique of image motion sensing is shown to have improved sensitivity and, therefore, a reduced focal plane area requirement in comparison with other candidate techniques (image-splitting prism and image dissector tube techniques). Another design requirement is speed in acquiring the guide star in order to maximize the time available for science observations. The design constraints are shown parametrically, and modelling results are presented.

Observations of the star Cor Caroli at the Apple Valley Workshop 2016

NASA Astrophysics Data System (ADS)

Estrada, Reed; Boyd, Sidney; Estrada, Chris; Evans, Cody; Rhoades, Hannah; Rhoades, Mark; Rhoades, Trevor

2017-06-01

Using a 22-inch Newtonian Alt/Az telescope and Celestron Micro Guide eyepiece, students participating in a workshop observed the binary star Cor Caroli (STF 1692) and found a position angle of 231.0 degrees as well as an average separation of 18.7" This observation compared favorably with the 2015 Washington Double Star published position. This project was part of Mark Brewer's Apple Valley Double Star Workshop. The results were analyzed using bias and circle error probability calculations.

Efficient reconstruction method for ground layer adaptive optics with mixed natural and laser guide stars.

PubMed

Wagner, Roland; Helin, Tapio; Obereder, Andreas; Ramlau, Ronny

2016-02-20

The imaging quality of modern ground-based telescopes such as the planned European Extremely Large Telescope is affected by atmospheric turbulence. In consequence, they heavily depend on stable and high-performance adaptive optics (AO) systems. Using measurements of incoming light from guide stars, an AO system compensates for the effects of turbulence by adjusting so-called deformable mirror(s) (DMs) in real time. In this paper, we introduce a novel reconstruction method for ground layer adaptive optics. In the literature, a common approach to this problem is to use Bayesian inference in order to model the specific noise structure appearing due to spot elongation. This approach leads to large coupled systems with high computational effort. Recently, fast solvers of linear order, i.e., with computational complexity O(n), where n is the number of DM actuators, have emerged. However, the quality of such methods typically degrades in low flux conditions. Our key contribution is to achieve the high quality of the standard Bayesian approach while at the same time maintaining the linear order speed of the recent solvers. Our method is based on performing a separate preprocessing step before applying the cumulative reconstructor (CuReD). The efficiency and performance of the new reconstructor are demonstrated using the OCTOPUS, the official end-to-end simulation environment of the ESO for extremely large telescopes. For more specific simulations we also use the MOST toolbox.

Ada Implementation Guide. Software Engineering With Ada. Volume 1

DTIC Science & Technology

1994-04-01

Staff, Department ofDefense Dictionary of Military and Associated Terms, Washington, D.C., 1989. STARS McDonal , C., and S . Redwine, *STARS Glossary: A...ADýA28 357> offj I Volume I I SI I t Ada Implementation II Guide 5 Software Engineering With AdaI I S DTIC QUALITY INSPECTED S 5 April 1994 g " 94...and Abbreviations ...................... I I N p a S I I I i I Libt of F4g u OW Tahl Figures 2-1 DON Directives and Instructions for Implementing Public

Hawaii Student / Teacher Astronomy Research program (HI STAR): 10 years of high school students exploring the universe

NASA Astrophysics Data System (ADS)

Mathews, Geoffrey; Armstrong, James; Nassir, Michael A.; Kaichi, Carolyn

2017-01-01

For the past decade, the Hawaii Student / Teacher Astronomy Research program (HI STAR) at UH Manoa’s Institute for Astronomy has trained astronomy-enthusiastic high school students in research, data analysis and science presentation skills. Every summer, a selected group of 8th-to-12th-grade students attend a week-long residential astronomy "camp" in Honolulu, Hawaii. The students experience the profession of astronomy by learning scientific skills such as imaging and spectroscopy, data-reduction, and data analysis. The week culminates with presention of a research project guided by professional astronomer mentors. During the following six months, each student continues to work with a mentor to complete a research project for submission to their local science fair. From 2012 - 2015, ~80% of students completed their long-term projects. Many have performed well; in each of 2015 and 2016, 5 alumni progressed to the International Science and Engineering Fair. Here we present the current structure of HI STAR and plans for the future.

RFA-based 589-nm guide star lasers for ESO VLT: a paradigm shift in performance, operational simplicity, reliability, and maintenance

NASA Astrophysics Data System (ADS)

Friedenauer, Axel; Karpov, Vladimir; Wei, Daoping; Hager, Manfred; Ernstberger, Bernhard; Clements, Wallace R. L.; Kaenders, Wilhelm G.

2012-07-01

Large telescopes equipped with adaptive optics require 20-25W CW 589-nm sources with emission linewidths of ~5 MHz. These Guide Star (GS) lasers should also be highly reliable and simple to operate and maintain for many years at the top of a mountain facility. Under contract from ESO, industrial partners TOPTICA and MPBC are nearing completion of the development of GS lasers for the ESO VLT, with delivery of the first of four units scheduled for December 2012. We report on the design and performance of the fully-engineered Pre-Production Unit (PPU), including system reliability/availability analysis, the successfully-concluded qualification testing, long-term component and system level tests and long-term maintenance and support planning. The chosen approach is based on ESO's patented narrow-band Raman Fiber Amplifier (EFRA) technology. A master oscillator signal from a linearly-polarized TOPTICA 20-mW, 1178-nm CW diode laser, with stabilized emission frequency and controllable linewidth up to a few MHz, is amplified in an MPBC polarization-maintaining (PM) RFA pumped by a high-power 1120-nm PM fiber laser. With efficient stimulated Brillouin scattering suppression, an unprecedented 40W of narrow-band RFA output has been obtained. This is then mode-matched into a resonant-cavity doubler with a free-spectral-range matching the sodium D2a to D2b separation, allowing simultaneous generation of an additional frequency component (D2b line) to re-pump the sodium atom electronic population. With this technique, the return flux can be increased without having to resort to electro-optical modulators and without the risk of introducing optical wave front distortions. The demonstrated output powers with doubling efficiencies >80% at 589 nm easily exceed the 20W design goal and require less than 700 W of electrical power. In summary, the fiber-based guide star lasers provide excellent beam quality and are modular, turn-key, maintenance-free, reliable, efficient, and ruggedized devices whose compactness allows installation directly onto the launch telescope structure.

Design of a CGH corrected calibration objective for the AO system at the Large Binocular Telescope

NASA Astrophysics Data System (ADS)

Schwab, Christian; Rakich, Andrew; Peter, Diethard; Aigner, Simon

2010-08-01

We describe the optical design of a calibration unit for the off-axis laser guide stars at the Large Binocular Telescope's ARGOS facility. Artificial stars with the desired wavefront are created using a computer generated hologram.

Hierarchical Structures in Biology as a Guide for New Materials Technology

DTIC Science & Technology

1994-01-01

properties--to changes in performance requirements. For example, while the spines of the sea urchin are moving, the attached ligaments are soft and...by studying how sea urchins control the material properties of their bodies as a function of the local environment. Sea stars, sea urchins , and sea ...Materials Research Society Bulletin 16(7):23-28. Trotter, J. A., and T. J. Koob. 1989. Collagen and proteoglycan in a sea urchin ligament with mutable

Characterizing the Hercules Thick Disk Cloud

DTIC Science & Technology

2009-01-01

merger. Key Words: Astronomy , Hercules Thick Disk Cloud, Galaxy, Star Count, Color, Photometric Parallax 2 Contents Chapter 1... Astronomy : Structure and Kinematics, 2nd ed., New York: W. H. Freeman and Company, 1981, pp 4. 5 Henbest, Guide, pp 10. 6 Mihalas, Galactic, pp 209...studies of astronomy later in his life, he focused on binary star systems and concluded that not all stars have the same absolute magnitude, thus

The ARGOS laser system: green light for ground layer adaptive optics at the LBT

NASA Astrophysics Data System (ADS)

Raab, Walfried; Rabien, Sebastian; Gässler, Wolfgang; Esposito, Simone; Barl, Lothar; Borelli, Jose; Daysenroth, Matthias; Gemperlein, Hans; Kulas, Martin; Ziegleder, Julian

2014-07-01

We report on the development of the laser system of ARGOS, the multiple laser guide star adaptive optics system for the Large Binocular Telescope (LBT). The system uses a total of six high powered, pulsed Nd:YAG lasers frequency-doubled to a wavelength of 532 nm to generate a set of three guide stars above each of the LBT telescopes. The position of each of the LGS constellations on sky as well as the relative position of the individual laser guide stars within this constellation is controlled by a set of steerable mirrors and a fast tip-tilt mirror within the laser system. The entire opto-mechanical system is housed in two hermetically sealed and thermally controlled enclosures on the SX and DX side of the LBT telescope. The laser beams are propagated through two refractive launch telescopes which focus the beams at an altitude of 12 km, creating a constellation of laser guide stars around a 4 arcminute diameter circle by means of Rayleigh scattering. In addition to the GLAO Rayleigh beacon system, ARGOS has also been designed for a possible future upgrade with a hybrid sodium laser - Rayleigh beacon combination, enabling diffraction limited operation. The ARGOS laser system was successfully installed at the LBT in April 2013. Extensive functional tests have been carried out and have verified the operation of the systems according to specifications. The alignment of the laser system with respect to the launch telescope was carried out during two more runs in June and October 2013, followed by the first propagation of laser light on sky in November 2013.

Calibration strategy and optics for ARGOS at the LBT

NASA Astrophysics Data System (ADS)

Schwab, Christian; Peter, Diethard; Aigner, Simon

2010-07-01

Effective calibration procedures play an important role for the efficiency and performance of astronomical instrumentation. We report on the calibration scheme for ARGOS, the Laser Guide Star (LGS) facility at the LBT. An artificial light source is used to feign the real laser beacons and perform extensive testing of the system, independent of the time of day and weather conditions, thereby greatly enhancing the time available for engineering. Fibre optics and computer generated holograms (CGHs) are used to generate the necessary wavefront. We present the optomechanical design, and discuss the expected accuracy, as well as tolerances in assembly and alignment.

Astronomy: A Self-Teaching Guide, 6th Edition

NASA Astrophysics Data System (ADS)

Moché, Dinah L.

2004-02-01

"A lively, up-to-date account of the basic principles of astronomy and exciting current field of research."-Science Digest For a quarter of a century, Astronomy: A Self-Teaching Guide has been making students and amateur stargazers alike feel at home among the stars. From stars, planets and galaxies, to black holes, the Big Bang and life in space, this title has been making it easy for beginners to quickly grasp the basic concepts of astronomy for over 25 years. Updated with the latest discoveries in astronomy and astrophysics, this newest edition of Dinah Moché's classic guide now includes many Web site addresses for spectacular images and news. And like all previous editions, it is packed with valuable tables, charts, star and moon maps and features simple activities that reinforce readers' grasp of basic concepts at their own pace, as well as objectives, reviews, and self-tests to monitor their progress. Dinah L. Moché, PhD (Rye, NY), is an award-winning author, educator, and lecturer. Her books have sold over nine million copies in seven languages.

ARGOS: the laser guide star system for the LBT

NASA Astrophysics Data System (ADS)

Rabien, S.; Ageorges, N.; Barl, L.; Beckmann, U.; Blümchen, T.; Bonaglia, M.; Borelli, J. L.; Brynnel, J.; Busoni, L.; Carbonaro, L.; Davies, R.; Deysenroth, M.; Durney, O.; Elberich, M.; Esposito, S.; Gasho, V.; Gässler, W.; Gemperlein, H.; Genzel, R.; Green, R.; Haug, M.; Hart, M. L.; Hubbard, P.; Kanneganti, S.; Masciadri, E.; Noenickx, J.; Orban de Xivry, G.; Peter, D.; Quirrenbach, A.; Rademacher, M.; Rix, H. W.; Salinari, P.; Schwab, C.; Storm, J.; Strüder, L.; Thiel, M.; Weigelt, G.; Ziegleder, J.

2010-07-01

ARGOS is the Laser Guide Star adaptive optics system for the Large Binocular Telescope. Aiming for a wide field adaptive optics correction, ARGOS will equip both sides of LBT with a multi laser beacon system and corresponding wavefront sensors, driving LBT's adaptive secondary mirrors. Utilizing high power pulsed green lasers the artificial beacons are generated via Rayleigh scattering in earth's atmosphere. ARGOS will project a set of three guide stars above each of LBT's mirrors in a wide constellation. The returning scattered light, sensitive particular to the turbulence close to ground, is detected in a gated wavefront sensor system. Measuring and correcting the ground layers of the optical distortions enables ARGOS to achieve a correction over a very wide field of view. Taking advantage of this wide field correction, the science that can be done with the multi object spectrographs LUCIFER will be boosted by higher spatial resolution and strongly enhanced flux for spectroscopy. Apart from the wide field correction ARGOS delivers in its ground layer mode, we foresee a diffraction limited operation with a hybrid Sodium laser Rayleigh beacon combination.

Free from the Atmosphere

NASA Astrophysics Data System (ADS)

2007-06-01

An artificial, laser-fed star now shines regularly over the sky of Paranal, home of ESO's Very Large Telescope, one of the world's most advanced large ground-based telescopes. This system provides assistance for the adaptive optics instruments on the VLT and so allows astronomers to obtain images free from the blurring effect of the atmosphere, regardless of the brightness and the location on the sky of the observed target. Now that it is routinely offered by the observatory, the skies seem much sharper to astronomers. In order to counteract the blurring effect of Earth's atmosphere, astronomers use the adaptive optics technique. This requires, however, a nearby reference star that has to be relatively bright, thereby limiting the area of the sky that can be surveyed. To surmount this limitation, astronomers now use at Paranal a powerful laser that creates an artificial star, where and when they need it. Two of the Adaptive Optics (AO) science instruments at the Paranal observatory, NACO and SINFONI, have been upgraded to work with the recently installed Laser Guide Star (LGS; see ESO 07/06) and have delivered their first scientific results. This achievement opens astronomers' access to a wealth of new targets to be studied under the sharp eyes of AO. "These unique results underline the advantage of using a Laser Guide Star with Adaptive Optics instruments, since they could not be obtained with Natural Guide Stars," says Norbert Hubin, head of the Adaptive Optics group at ESO. "This is also a crucial milestone towards the multi-laser systems ESO is designing for the VLT and the future E-ELT" (see e.g. ESO 19/07). ESO PR Photo 27a/07 ESO PR Photo 27a/07 An Ultra Luminous Merger (NACO-LGS/VLT) The Laser Guide Star System installed at Paranal uses the PARSEC dye laser developed by MPE-Garching and MPIA-Heidelberg, while the launch telescope and the laser laboratory was developed by ESO. "It is great to see the whole system working so well together," emphasises Richard Davies, project manager of the PARSEC laser. "To test the laser guide star adaptive optics system to its limits, and even beyond, we observed a number of galaxies, ranging from a close neighbour to one that is seen when the universe was very young," explains Markus Kasper, the NACO Instrument Scientist at ESO. The first objects that were observed are interacting galaxies. The images obtained reveal exquisite details, and have a resolution comparable to that of the Hubble Space Telescope. In one case, it was possible to derive for the first time the motion of the stars in two merging galaxies, showing that there are two counter-rotating discs of stars. "The enhanced resolution that laser guide star adaptive optics provides is certain to bring important new discoveries in this exciting area," says Davies ESO PR Photo 27c/07 ESO PR Photo 27c/07 Merging System Arp 220 (SINFONI-LGS/VLT) The astronomers then turned the laser to a galaxy called K20-ID5 which is at a redshift of 2.2 - we are seeing this galaxy when the universe was less than 1/3 of its current age. The image obtained with NACO shows that the stars are concentrated in a much more compact region than the gas. "These observations are both remarkable and exciting," declares Kasper. "They are the first time that it has been possible to trace in such detail the distributions of both the stars and the gas at an epoch where we are witnessing the formation of galaxies similar to our own Milky Way." At the opposite extreme, much nearer to home, LGS-AO observations were made of the active galaxy NGC 4945. The new LGS observations with NACO resolved the central parts into a multitude of individual stars. "It is in galaxies such as these where we can really quantify the star formation history in the vicinity of the nucleus, that we can start to piece together the puzzle of how gas is accreted onto the supermassive black hole, and understand how and when these black holes light up so brightly," says Davies. ESO PR Photo 27e/07 ESO PR Photo 27e/07 Active Galaxy NGC 4945 (NACO-LGS/VLT) Still closer to home, the LGS system can also be applied to solar system objects, such as asteroids or satellites, but also to the study of particular regions of spatially extended bodies like the polar regions of giant planets, where aurora activity is concentrated. During their science verification, the scientists turned the SINFONI instrument with the LGS to a Trans-Neptunian Object, 2003 EL 61. The high image contrast and sensitivity obtained with the use of the LGS mode permit the detection of the two faint satellites known to orbit the TNO. "From such observations one can study the chemical composition of the surface material of the TNO and its satellites (mainly crystalline water ice), estimate their surface properties and constrain their internal structure," explains Christophe Dumas, from ESO. The VLT Laser Guide System is the result of a collaborative work by a team of scientists and engineers from ESO and the Max Planck Institutes for Extraterrestrial Physics in Garching and for Astronomy in Heidelberg, Germany. NACO was built by a Consortium of French and German institutes and ESO. SINFONI was built by a Consortium of German and Dutch Institutes and ESO. More Information Normally, the achievable image sharpness of a ground-based telescope is limited by the effect of atmospheric turbulence. This drawback can be surmounted with adaptive optics, allowing the telescope to produce images that are as sharp as if taken from space. This means that finer details in astronomical objects can be studied, and also that fainter objects can be observed. In order to work, adaptive optics needs a nearby reference star that has to be relatively bright, thereby limiting the area of the sky that can be surveyed to a few percent only. To overcome this limitation, astronomers use a powerful laser that creates an artificial star, where and when they need it. The laser beam takes advantage of the layer of sodium atoms that is present in Earth's atmosphere at an altitude of 90 kilometres. Shining at a well-defined wavelength the laser makes it glow. The laser is launched from Yepun, the fourth 8.2-m Unit Telescope of the Very Large Telescope, producing an artificial star. Despite this star being about 20 times fainter than the faintest star that can be seen with the unaided eye, it is bright enough for the adaptive optics to measure and correct the atmosphere's blurring effect. Compared to a normal star, this artificial star has some differing properties that the associated Laser Guide Star (LGS) Adaptive Optics (AO) system has to be able to cope with. A press release, in English and German, is also available from the Max-Planck Institute.

Back on Track

NASA Astrophysics Data System (ADS)

2007-06-01

An artificial, laser-fed star now shines regularly over the sky of Paranal, home of ESO's Very Large Telescope, one of the world's most advanced large ground-based telescopes. This system provides assistance for the adaptive optics instruments on the VLT and so allows astronomers to obtain images free from the blurring effect of the atmosphere, regardless of the brightness and the location on the sky of the observed target. Now that it is routinely offered by the observatory, the skies seem much sharper to astronomers. In order to counteract the blurring effect of Earth's atmosphere, astronomers use the adaptive optics technique. This requires, however, a nearby reference star that has to be relatively bright, thereby limiting the area of the sky that can be surveyed. To surmount this limitation, astronomers now use at Paranal a powerful laser that creates an artificial star, where and when they need it. Two of the Adaptive Optics (AO) science instruments at the Paranal observatory, NACO and SINFONI, have been upgraded to work with the recently installed Laser Guide Star (LGS; see ESO 07/06) and have delivered their first scientific results. This achievement opens astronomers' access to a wealth of new targets to be studied under the sharp eyes of AO. "These unique results underline the advantage of using a Laser Guide Star with Adaptive Optics instruments, since they could not be obtained with Natural Guide Stars," says Norbert Hubin, head of the Adaptive Optics group at ESO. "This is also a crucial milestone towards the multi-laser systems ESO is designing for the VLT and the future E-ELT" (see e.g. ESO 19/07). ESO PR Photo 27a/07 ESO PR Photo 27a/07 An Ultra Luminous Merger (NACO-LGS/VLT) The Laser Guide Star System installed at Paranal uses the PARSEC dye laser developed by MPE-Garching and MPIA-Heidelberg, while the launch telescope and the laser laboratory was developed by ESO. "It is great to see the whole system working so well together," emphasises Richard Davies, project manager of the PARSEC laser. "To test the laser guide star adaptive optics system to its limits, and even beyond, we observed a number of galaxies, ranging from a close neighbour to one that is seen when the universe was very young," explains Markus Kasper, the NACO Instrument Scientist at ESO. The first objects that were observed are interacting galaxies. The images obtained reveal exquisite details, and have a resolution comparable to that of the Hubble Space Telescope. In one case, it was possible to derive for the first time the motion of the stars in two merging galaxies, showing that there are two counter-rotating discs of stars. "The enhanced resolution that laser guide star adaptive optics provides is certain to bring important new discoveries in this exciting area," says Davies ESO PR Photo 27c/07 ESO PR Photo 27c/07 Merging System Arp 220 (SINFONI-LGS/VLT) The astronomers then turned the laser to a galaxy called K20-ID5 which is at a redshift of 2.2 - we are seeing this galaxy when the universe was less than 1/3 of its current age. The image obtained with NACO shows that the stars are concentrated in a much more compact region than the gas. "These observations are both remarkable and exciting," declares Kasper. "They are the first time that it has been possible to trace in such detail the distributions of both the stars and the gas at an epoch where we are witnessing the formation of galaxies similar to our own Milky Way." At the opposite extreme, much nearer to home, LGS-AO observations were made of the active galaxy NGC 4945. The new LGS observations with NACO resolved the central parts into a multitude of individual stars. "It is in galaxies such as these where we can really quantify the star formation history in the vicinity of the nucleus, that we can start to piece together the puzzle of how gas is accreted onto the supermassive black hole, and understand how and when these black holes light up so brightly," says Davies. ESO PR Photo 27e/07 ESO PR Photo 27e/07 Active Galaxy NGC 4945 (NACO-LGS/VLT) Still closer to home, the LGS system can also be applied to solar system objects, such as asteroids or satellites, but also to the study of particular regions of spatially extended bodies like the polar regions of giant planets, where aurora activity is concentrated. During their science verification, the scientists turned the SINFONI instrument with the LGS to a Trans-Neptunian Object, 2003 EL 61. The high image contrast and sensitivity obtained with the use of the LGS mode permit the detection of the two faint satellites known to orbit the TNO. "From such observations one can study the chemical composition of the surface material of the TNO and its satellites (mainly crystalline water ice), estimate their surface properties and constrain their internal structure," explains Christophe Dumas, from ESO. The VLT Laser Guide System is the result of a collaborative work by a team of scientists and engineers from ESO and the Max Planck Institutes for Extraterrestrial Physics in Garching and for Astronomy in Heidelberg, Germany. NACO was built by a Consortium of French and German institutes and ESO. SINFONI was built by a Consortium of German and Dutch Institutes and ESO. More Information Normally, the achievable image sharpness of a ground-based telescope is limited by the effect of atmospheric turbulence. This drawback can be surmounted with adaptive optics, allowing the telescope to produce images that are as sharp as if taken from space. This means that finer details in astronomical objects can be studied, and also that fainter objects can be observed. In order to work, adaptive optics needs a nearby reference star that has to be relatively bright, thereby limiting the area of the sky that can be surveyed to a few percent only. To overcome this limitation, astronomers use a powerful laser that creates an artificial star, where and when they need it. The laser beam takes advantage of the layer of sodium atoms that is present in Earth's atmosphere at an altitude of 90 kilometres. Shining at a well-defined wavelength the laser makes it glow. The laser is launched from Yepun, the fourth 8.2-m Unit Telescope of the Very Large Telescope, producing an artificial star. Despite this star being about 20 times fainter than the faintest star that can be seen with the unaided eye, it is bright enough for the adaptive optics to measure and correct the atmosphere's blurring effect. Compared to a normal star, this artificial star has some differing properties that the associated Laser Guide Star (LGS) Adaptive Optics (AO) system has to be able to cope with. A press release, in English and German, is also available from the Max-Planck Institute.

Observations of the Star Cor Caroli at the Apple Valley Workshop 2016 (Abstract)

NASA Astrophysics Data System (ADS)

Estrada, R.; Boyd, S.; Estrada, C.; Evans, C.; Rhoades, H.; Rhoades, M.; Rhoades, T.

2017-12-01

(Abstract only) Using a 22-inch Newtonian Alt/Az telescope and Celestron Micro Guide eyepiece, students participating in a workshop observed the binary star Cor Caroli (STF 1692; alpha CVn) and found a position angle of 231.0 degrees as well as an average separation of 18.7" This observation compared favorably with the 2015 Washington Double Star published position. This project was part of Mark Brewer's Apple Valley Double Star Workshop. The results were analyzed using bias and circle error probability calculations.

Star Trek with Latin. Teacher's Guide. Tentative Edition.

ERIC Educational Resources Information Center

Masciantonio, Rudolph; And Others

The purpose of this guide is to assist Latin and English teachers with some background in Latin to expand the English vocabulary and reading skills of students through the study of Latin roots, prefixes, and suffixes. The introductory material in the guide provides general notes on the teaching of Latin in the Philadelphia School District,…

Configuration optimization of laser guide stars and wavefront correctors for multi-conjugation adaptive optics

NASA Astrophysics Data System (ADS)

Xuan, Li; He, Bin; Hu, Li-Fa; Li, Da-Yu; Xu, Huan-Yu; Zhang, Xing-Yun; Wang, Shao-Xin; Wang, Yu-Kun; Yang, Cheng-Liang; Cao, Zhao-Liang; Mu, Quan-Quan; Lu, Xing-Hai

2016-09-01

Multi-conjugation adaptive optics (MCAOs) have been investigated and used in the large aperture optical telescopes for high-resolution imaging with large field of view (FOV). The atmospheric tomographic phase reconstruction and projection of three-dimensional turbulence volume onto wavefront correctors, such as deformable mirrors (DMs) or liquid crystal wavefront correctors (LCWCs), is a very important step in the data processing of an MCAO’s controller. In this paper, a method according to the wavefront reconstruction performance of MCAO is presented to evaluate the optimized configuration of multi laser guide stars (LGSs) and the reasonable conjugation heights of LCWCs. Analytical formulations are derived for the different configurations and are used to generate optimized parameters for MCAO. Several examples are given to demonstrate our LGSs configuration optimization method. Compared with traditional methods, our method has minimum wavefront tomographic error, which will be helpful to get higher imaging resolution at large FOV in MCAO. Project supported by the National Natural Science Foundation of China (Grant Nos. 11174274, 11174279, 61205021, 11204299, 61475152, and 61405194) and the State Key Laboratory of Applied Optics, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences.

GeMS: Gemini Mcao System: current status and commissioning plans

NASA Astrophysics Data System (ADS)

Boccas, Maxime; Rigaut, François; Gratadour, Damien; d'Orgeville, Céline; Bec, Matthieu; Daruich, Felipe; Perez, Gabriel; Arriagada, Gustavo; Bombino, Stacy; Carter, Chris; Cavedoni, Chas; Collao, Fabian; Collins, Paul; Diaz, Pablo; Ebbers, Angelic; Galvez, Ramon; Gausachs, Gaston; Hardash, Steve; James, Eric; Karewicz, Stan; Lazo, Manuel; Maltes, Diego; Mouser, Ron; Rogers, Rolando; Rojas, Roberto; Sheehan, Michael; Trancho, Gelys; Vergara, Vicente; Vucina, Tomislav

2008-07-01

The Gemini Multi-Conjugate Adaptive Optics project was launched in April 1999 to become the Gemini South AO facility in Chile. The system includes 5 laser guide stars, 3 natural guide stars and 3 deformable mirrors optically conjugated at 0, 4.5 and 9km to achieve near-uniform atmospheric compensation over a 1 arc minute square field of view. Sub-contracted systems with vendors were started as early as October 2001 and were all delivered by July 2007, but for the 50W laser (due around September 2008). The in-house development began in January 2006, and is expected to be completed by the end of 2008 to continue with integration and testing (I&T) on the telescope. The on-sky commissioning phase is scheduled to start during the first half of 2009. In this general overview, we will first describe the status of each subsystem with their major requirements, risk areas and achieved performance. Next we will present our plan to complete the project by reviewing the remaining steps through I&T and commissioning on the telescope, both during day-time and at night-time. Finally, we will summarize some management activities like schedules, resources and conclude with some lessons learned.

Status of the ARGOS project

NASA Astrophysics Data System (ADS)

Rabien, Sebastian; Barl, Lothar; Beckmann, Udo; Bonaglia, Marco; Borelli, José Luis; Brynnel, Joar; Buschkamp, Peter; Busoni, Lorenzo; Christou, Julian; Connot, Claus; Davies, Richard; Deysenroth, Matthias; Esposito, Simone; Gässler, Wolfgang; Gemperlein, Hans; Hart, Michael; Kulas, Martin; Lefebvre, Michael; Lehmitz, Michael; Mazzoni, Tommaso; Nussbaum, Edmund; Orban de Xivry, Gilles; Peter, Diethard; Quirrenbach, Andreas; Raab, Walfried; Rahmer, Gustavo; Storm, Jesper; Ziegleder, Julian

2014-07-01

ARGOS is the Laser Guide Star and Wavefront sensing facility for the Large Binocular Telescope. With first laser light on sky in 2013, the system is currently undergoing commissioning at the telescope. We present the overall status and design, as well as first results on sky. Aiming for a wide field ground layer correction, ARGOS is designed as a multi- Rayleigh beacon adaptive optics system. A total of six powerful pulsed lasers are creating the laser guide stars in constellations above each of the LBTs primary mirrors. With a range gated detection in the wavefront sensors, and the adaptive correction by the deformable secondary's, we expect ARGOS to enhance the image quality over a large range of seeing conditions. With the two wide field imaging and spectroscopic instruments LUCI1 and LUCI2 as receivers, a wide range of scientific programs will benefit from ARGOS. With an increased resolution, higher encircled energy, both imaging and MOS spectroscopy will be boosted in signal to noise by a large amount. Apart from the wide field correction ARGOS delivers in its ground layer mode, we already foresee the implementation of a hybrid Sodium with Rayleigh beacon combination for a diffraction limited AO performance.

Motivating salespeople: what really works.

PubMed

Steenburgh, Thomas; Ahearne, Michael

2012-01-01

No sales force consists entirely of stars; sales staffs are usually made up mainly of solid perfomers, with smaller groups of laggards and rainmakers. Though most compensation plans approach these three groups as if they were the same, research shows that each is motivated by something different. By accounting for those differences in their incentive programs, companies can coax better performance from all their salespeople. As the largest cadre, core performers typically represent the greatest opportunity, but they're often ignored by incentive plans. Contests with prizes that vary in nature and value (and don't all go to stars) will inspire them to ramp up their efforts, and tiered targets will guide them up the performance curve. Laggards need quarterly bonuses to stay on track; when they have only annual bonuses, their revenues will drop 10%, studies show. This group is also motivated by social pressure-especially from new talent on the sales bench. Stars tend to get the most attention in comp plans, but companies often go astray by capping their commissions to control costs. If firms instead remove commission ceilings and pay extra for overachievement, they'll see the sales needle really jump. The key is to treat sales compensation not as an expense to rein in but as a portfolio of investments to manage. Companies that do this will be rewarded with much higher returns.

A walk through the heavens : a guide to stars and constellations and their legends

NASA Astrophysics Data System (ADS)

Heifetz, Milton D.; Tirion, Wil

What star is that? Where's the Great Bear? Who was Andromeda? A Walk through the Heavens is your guide to the pathways of the night sky, answering the commonest questions about what you can see up there. There are simplified maps of the constellations, together with instructions on how to gauge their sizes and the distances between them. With this information you can find the constellations easily, and make a journey by eye from one constellation to the next. Ancient myths surrounding the constellations are retold, enriching our understanding of how historical peoples saw the awe-inspiring spectacle of a sky sprinkled with stars. This book, magically illustrated by Wil Tirion, does not require any instrument or telescope. It is an ideal introduction to launch a young astronomer on a journey across starlit skies.

Reference Collections and Standards.

ERIC Educational Resources Information Center

Winkel, Lois

1999-01-01

Reviews six reference materials for young people: "The New York Public Library Kid's Guide to Research"; "National Audubon Society First Field Guide. Mammals"; "Star Wars: The Visual Dictionary"; "Encarta Africana"; "World Fact Book, 1998"; and "Factastic Book of 1001 Lists". Includes ordering information.(AEF)

Student Measurements of STFA 14 AC at Vanguard Preparatory School

NASA Astrophysics Data System (ADS)

Gillette, Sean; Archuleta, Alex; Diaz, Lizbeth; Gillespie, Kyle; Gosney, Timothy; Johnson, Stephen; Mohan, Nikita; Rajacich, Jacob; Roehl, Nathaniel; Sharpe, Scotty; Whitt, Kahaloha

2016-01-01

Eighth grade students at Vanguard Preparatory School measured the double star STFA 14 AC using a Bader Planetarium Micro Guide eyepiece. Navi (Gamma Cassiopeiae) was used as the ca libration star. The calculated means of multiple observations of STFA 14 AC resulted in a separation of 53.3" and a position angle of 2.0°. These measurements were compared to the most recent values in the Washington Double Star Catalog.

A Traveler's Guide to the Universe

ERIC Educational Resources Information Center

Darling, Gerald

2012-01-01

Elementary school students are intensely curious about astronomy: the Moon, planets, stars, and galaxies. Summer, with its warm evenings and star-filled skies, is the perfect time for students to explore the cosmos with a pair of binoculars. Because binoculars are used for many purposes (sporting events or birding, for example), many families…

Fairbanks North Star borough rural roads upgrade inventory and cost estimation software user guide : version I.

DOT National Transportation Integrated Search

2013-04-01

The Rural Road Upgrade Inventory and Cost Estimation Software is designed by the AUTC : research team to help the Fairbanks North Star Borough (FNSB) estimate the cost of upgrading : rural roads located in the Borough's Service Areas. The Software pe...

Biology Students Building Computer Simulations Using StarLogo TNG

ERIC Educational Resources Information Center

Smith, V. Anne; Duncan, Ishbel

2011-01-01

Confidence is an important issue for biology students in handling computational concepts. This paper describes a practical in which honours-level bioscience students simulate complex animal behaviour using StarLogo TNG, a freely-available graphical programming environment. The practical consists of two sessions, the first of which guides students…

The First US Naval Observatory CCD Astrograph Catalog

NASA Astrophysics Data System (ADS)

Zacharias, N.; Urban, S. E.; Zacharias, M. I.; Hall, D. M.; Wycoff, G. L.; Rafferty, T. J.; Germain, M. E.; Holdenried, E. R.; Pohlman, J. W.; Gauss, F. S.; Monet, D. G.; Winter, L.

2000-10-01

The USNO CCD Astrograph (UCA) started an astrometric survey in 1998 February at Cerro Tololo, Chile. This first, preliminary catalog (UCAC1) includes data taken up to 1999 November with about 80% of the Southern Hemisphere covered. Observing continues, and full sky coverage is expected by mid-2003 after moving the instrument to a Northern Hemisphere site in early 2001. The survey is performed in a single bandpass (579-642 nm), a twofold overlap pattern of fields, and with a long and a short exposure on each field. Stars in the magnitude range 10-14 have positional precisions of <=20 mas. At the limiting magnitude of R~16 mag, the positional precision is 70 mas. The UCAC aims at a density (stars per square degree) larger than that of the Guide Star Catalog (GSC) with a positional accuracy similar to Tycho. The UCAC program is a major step toward a high-precision densification of the optical reference frame in the post-Hipparcos era, and the first stage, the UCAC1 contains over 27 million stars. Preliminary proper motions are included, which were derived from Tycho-2, Hipparcos, and ground-based transit circle and photographic surveys for the bright stars (V<=12.5 mag) and the USNO A2.0 for the fainter stars. The accuracy of the proper motions varies widely, from 1 to over 15 mas yr-1. The UCAC1 is available on CD-ROM from the US Naval Observatory.

ATLASGAL: Chemical evolution of star forming clumps

NASA Astrophysics Data System (ADS)

Figura, Charles C.; Urquhart, James S.; Wyrowski, Friedrich

2017-01-01

Although massive stars are few in number, they impact their host molecular clouds, clusters, and galaxies in profound ways, playing a vital role in regulating star formation in their host galaxy. Understanding the formation of these massive stars is critical to understanding this evolution, but their rapid early development causes them to reach the main sequence while still shrouded in their natal molecular cloud. Many studies have investigated these regions in a targeted manner, but a full understanding necessitates a broader view at all stages of formation across many star forming regions.We have used mid-infrared continuum surveys to guide selection of a statistically large sample of massive dust clumps from the 10,000 such clumps identified in the ATLASGAL Compact Source Catalogue (CSC), ensuring that all stages of the evolutionary process are included. A final sample of 600 fourth-quadrant sources within 1 degree of the Galactic plane were observed with the Mopra telescope with an 8 GHz bandwidth between 85.2 and 93.4 GHz.We present an overview of our results. We have identified over 30 molecular lines, seven of which with detected hyperfine structure, as well as several mm-radio recombination line transitions. Source velocities indicate that these regions trace the Crux-Scutum, Norma, and Carina Sagitarius arms. We have performed an analysis of linewidth and line intensity ratios, correlating these with star formation stages as identified by IR brightness at the 70 and 24 μm bands, and present several molecular pairs whose linewidth and intensity might serve as significant tracers of the evolutionary stage of star formation. We comment on the results of PCA analysis of the measured parameters for the overall population and the star formation stage subgroups with an eye toward characterising early stellar development through molecular line observations.

Dim star fringe stabilization demonstration using pathlength feed-forward on the SIM testbed 3 (STB3)

NASA Astrophysics Data System (ADS)

Goullioud, Renaud; Alvarez-Salazar, Oscar S.; Nemati, Bijan

2003-02-01

Future space-based optical interferometers such as the Space Interferometer Mission require fringe stabilization to the level of nanometers in order to produce astrometric data at the micro-arc-second level. Even the best attitude control system available to date will not be able to stabilize the attitude of a several thousand pound spacecraft to a few milli-arc-seconds. Active pathlength control is usually implemented to compensate for attitude drift of the spacecraft. This issue has been addressed in previous experiments while tracking bright stars. In the case of dim stars, as the sensor bandwidth falls below one hertz, feedback control will not provide sufficient rejection. However, stabilization of the fringes from a dim-star down to the nanometer level can be done open loop using information from additional interferometers looking at bright guide stars. The STB3 testbed developed at the Jet Propulsion Laboratory features three optical interferometers sharing a common baseline, dynamically representative to the SIM interferometer. An artificial star feeding the interferometers is installed on a separate optics bench. Voice coils are used to simulate the attitude motion of the spacecraft by moving the entire bench. Data measured on STB3 show that fringe motion of a dim star due to spacecraft attitude changes can be attenuated by 80 dB at 0.1Hz without feedback control, using only information from two guide stars. This paper describes the STB3 setup, the pathlength feed-forward architecture, implementation issues and data collected with the system.

The First Light of the Subaru Laser Guide Star Adaptive Optics System

NASA Astrophysics Data System (ADS)

Takami, H.; Hayano, Y.; Oya, S.; Hattori, M.; Watanabe, M.; Guyon, O.; Eldred, M.; Colley, S.; Saito, Y.; Itoh, M.; Dinkins, M.

Subaru Telescope has been operating 36 element curvature sensor AO system for the Cassegrain focus since 2000. We have developed a new AO system for the Nasmyth focus. The AO system has 188 element curvature wavefront sensor and bimorph deformable mirror. It is the largest format system for this type of sensor . The deformable mirror has also 188 element with 90 mm effective aperture and 130 mm blank size. The real time controller is 4 CPU real time Linux OS computer and the update speed is now 1.5 kHz. The AO system also has laser guide star system. The laser is sum frequency solid state laser generating 589 nm light. We have achieved 4.7 W output power with excellent beam quality of M^2=1.1 and good stability. The laser is installed in a clean room on the Nasmyth platform. The laser beam is transferred by photonic crystal optical fiber with 35 m to the 50 cm laser launching telescope mounted behind the Subaru 2ry mirror. The field of view of the low order wavefront sensor for tilt guide star in LGS mode is 2.7 arcmin in diameter. The AO system had the first light with natural guide star in October 2006. The Strehl ratio was > 0.5 at K band under the 0.8 arcsec visible seeing. We also has projected laser beam on the sky during the same engineering run. Three instruments will be used with the AO system. Infrared camera and spectrograph (IRCS), High dynamic range IR camera (HiCIAO) for exosolar planet detection, and visible 3D spectrograph.

The Monthly Sky Guide: Sixth Edition

NASA Astrophysics Data System (ADS)

Ridpath, Ian; Tirion, Wil

2003-06-01

The latest edition of Ian Ridpath and Wil Tirion's popular guide to the night sky is updated for planet positions and forthcoming eclipses up to the end of the year 2007. With one chapter for each month of the year, this is an easy-to-use handbook for anyone wanting to identify constellations, star clusters, nebulae, to plot the movement of planets, or witness solar and lunar eclipses. Most of the features discussed are visible to the naked eye and all can be seen with a small telescope or binoculars. Ian Ridpath has been a full-time writer, broadcaster and lecturer on astronomy and space for more than twenty-five years. He has written and edited more than 40 books, including A Comet Called Haley (Cambridge, 1985). Wil Tirion made his first star map in 1977. It showed stars to the magnitude of 6.5 and was issued as a set of maps by the British Astronomical Association in 1981. He has illustrated numerous books and magazines, including The Cambridge Star Atlas (Cambridge, 2001). Previous Edition Pb (1999): 0-521-66771-2

Managing the star performer.

PubMed

Hills, Laura

2013-01-01

Our culture seems to be endlessly fascinated with its stars in entertainment, athletics, politics, and business, and holds fast to the idea that extraordinary talent accounts for an individual's extraordinary performance. At first glance, managing a star performer in your medical practice may seem like it would be an easy task. However, there's much more to managing a star performer than many practice managers realize. The concern is how to keep the star performer happy and functioning at a high level without detriment to the rest of the medical practice team. This article offers tips for practice managers who manage star performers. It explores ways to keep the star performer motivated, while at the same time helping the star performer to meld into the existing medical practice team. This article suggests strategies for redefining the star performer's role, for holding the star performer accountable for his or her behavior, and for coaching the star performer. Finally, this article offers practical tips for keeping the star performer during trying times, for identifying and cultivating new star performers, and for managing medical practice prima donnas.

Feasibility of polymer gel-based measurements of radiation isocenter accuracy in magnetic fields

NASA Astrophysics Data System (ADS)

Dorsch, S.; Mann, P.; Lang, C.; Haering, P.; Runz, A.; Karger, C. P.

2018-06-01

For conventional irradiation devices, the radiation isocenter accuracy is determined by star shot measurements on films. In magnetic resonance (MR)-guided radiotherapy devices, the results of this test may be altered by the magnetic field and the need to align the radiation and imaging isocenter may require a modification of measurement procedures. Polymer dosimetry gels (PG) may offer a way to perform both, the radiation and imaging isocenter test, however, first it has to be shown that PG reveal results comparable to the conventionally applied films. Therefore, star shot measurements were performed at a linear accelerator using PG as well as radiochromic films. PG were evaluated using MR imaging and the isocircle radius and the distance between the isocircle center and the room isocenter were determined. Two different types of experiments were performed: i) a standard star-shot isocenter test and (ii) a star shot, where the detectors were placed between the pole shoes of an experimental electro magnet operated either at 0 T or 1 T. For the standard star shot, PG evaluation was independent of the time delay after irradiation (1 h, 24 h, 48 h and 216 h) and the results were comparable to those of film measurements. Within the electro magnet, the isocircle radius increased from 0.39  ±  0.01 mm to 1.37  ±  0.01 mm for the film and from 0.44  ±  0.02 mm to 0.97  ±  0.02 mm for the PG-measurements, respectively. The isocenter distance was essentially dependent on the alignment of the magnet to the isocenter and was between 0.12  ±  0.02 mm and 0.82  ±  0.02 mm. The study demonstrates that evaluation of the PG directly after irradiation is feasible, if only geometrical parameters are of interest. This allows using PG for star shot measurements to evaluate the radiation isocenter accuracy with comparable accuracy as with radiochromic films.

The Solar and Heliospheric Observatory (SOHO) Mission: An Overview of Flight Dynamics Support of the Early Mission Phase

NASA Technical Reports Server (NTRS)

Short, R.; Behuncik, J.

1996-01-01

The SOHO spacecraft was successfully launched by an Atlas 2AS from the Eastern Range on December 2, 1995. After a short time in a nearly circular parking orbit, the spacecraft was placed by the Centaur upper stage on a transfer trajectory to the L1 libration point where it was inserted into a class 1 Halo orbit. The nominal mission lifetime is two years which will be spent collecting data from the Sun using a complement of twelve instruments. An overview of the early phases of Flight Dynamics Facility support of the mission is given. Maneuvers required for the mission are discussed, and an evaluation of these maneuvers is given with the attendent effects on the resultant orbit. Thruster performance is presented as well as real time monitoring of thruster activity during maneuvers. Attitude areas presented are the star identification process and role angle determination, momentum management, operating constraints on the star tracker, and guide star switching. A brief description of the two Heads Up displays is given.

Remote Operations of Laser Guide Star Systems: Gemini Observatory.

NASA Astrophysics Data System (ADS)

Oram, Richard J.; Fesquet, Vincent; Wyman, Robert; D'Orgeville, Celine

2011-03-01

The Gemini North telescope, equipped with a 14W laser, has been providing Laser Guide Star Adaptive Optics (LGS AO) regular science queue observations for worldwide astronomers since February 2007. The new 55W laser system for MCAO was installed on the Gemini South telescope in May 2010. In this paper, we comment on how Gemini Observatory developed regular remote operation of the Laser Guide Star Facility and high-power solid-state laser as routine normal operations. Fully remote operation of the LGSF from the Hilo base facility HBF was initially trialed and then optimized and became the standard operating procedure (SOP) for LGS operation in December 2008. From an engineering perspective remote operation demands stable, well characterized and base-lined equipment sets. In the effort to produce consistent, stable and controlled laser parameters (power, wavelength and beam quality) we completed a failure mode effect analysis of the laser system and sub systems that initiated a campaign of hardware upgrades and procedural improvements to the routine maintenance operations. Finally, we provide an overview of normal operation procedures during LGS runs and present a snapshot of data accumulated over several years that describes the overall LGS AO observing efficiency at the Gemini North telescope.

Stellar Oscillations Network Group

NASA Astrophysics Data System (ADS)

Grundahl, F.; Kjeldsen, H.; Christensen-Dalsgaard, J.; Arentoft, T.; Frandsen, S.

2007-06-01

Stellar Oscillations Network Group (SONG) is an initiative aimed at designing and building a network of 1m-class telescopes dedicated to asteroseismology and planet hunting. SONG will have 8 identical telescope nodes each equipped with a high-resolution spectrograph and an iodine cell for obtaining precision radial velocities and a CCD camera for guiding and imaging purposes. The main asteroseismology targets for the network are the brightest (V < 6) stars. In order to improve performance and reduce maintenance costs the instrumentation will only have very few modes of operation. In this contribution we describe the motivations for establishing a network, the basic outline of SONG and the expected performance.

Student Measurements of STFA 10AB (Theta Tauri)

NASA Astrophysics Data System (ADS)

Gillette, Sean; Estrada, Chris; Estrada, Reed; Aguilera, Sophia; Chavez, Valerie; Givens, Jalynn; Lindorfer, Sarah; Michels, Kaylie; Mobley, Makenzie; Reder, Gabriel; Renteria, Kayla; Shattles, Jenna; Wilkin, Aiden; Woodbury, Maisy; Rhoades, Breauna; Rhoades, Mark

2017-04-01

Eighth grade students at Vanguard Preparatory School measured the double star STFA 10AB using a 22-inch Newtonian Alt/Az telescope and a Celestron Micro Guide eyepiece. Bellatrix was used as the calibration star. The calculated means of multiple observations of STFA 10AB resulted in a separation of 45.18,” a scale constant of 7.88 arcseconds per division, and position angle of 257.9°. These measurements were compared to the most recent values in the Washington Double Star Catalog.

Advances in instrumentation at the W. M. Keck Observatory

NASA Astrophysics Data System (ADS)

Adkins, Sean M.; Armandroff, Taft E.; Johnson, James; Lewis, Hilton A.; Martin, Christopher; McLean, Ian S.; Wizinowich, Peter

2012-09-01

In this paper we describe both recently completed instrumentation projects and our current development efforts in terms of their role in the strategic plan, the key science areas they address, and their performance as measured or predicted. Projects reaching completion in 2012 include MOSFIRE, a near IR multi-object spectrograph, a laser guide star adaptive optics facility on the Keck I telescope, and an upgrade to the guide camera for the HIRES instrument on Keck I. Projects in development include a new seeing limited integral field spectrograph for the visible wavelength range called the Keck Cosmic Web Imager (KCWI), an upgrade to the telescope control systems on both Keck telescopes, a near-IR tip/tilt sensor for the Keck I adaptive optics system, and a new grating for the OSIRIS integral field spectrograph.

Soaring through the Universe. Astronomy through Children's Literature.

ERIC Educational Resources Information Center

Letwinch, Joanne C.

This publication is a guide to teaching astronomy through the use of mythology and its literature in grades 3-6. The book is divided into the following seven sections: "Introduction"; Chapter 1: "Luna: the Moon"; Chapter 2: "Del Sol: the Sun"; Chapter 3: "The Planets"; Chapter 4: "Star Bright, Star Light"; Chapter 5: "Traveling through Space"; and…

Mini-Rocket User Guide

DTIC Science & Technology

2007-08-01

26 ISTC Simulation Comparisons ............................................................................... 29 STARS...Range Comparison Figure 8. ISTC Simulntioiz Comparisons 29 Mini-Rocket User Guide REAL-WORLD COMPARISON In particular, note the very high angle-of...not directly model the missile rigid body dynamics. The ISTC subsequently used Mini-Rocket as a driver to stimulate other models and as a risk

Stellar spectral classification of previously unclassified stars GSC 4461-698 and GSC 4466-870

NASA Astrophysics Data System (ADS)

Grau, Darren Moser

Stellar spectral classification is one of the first efforts undertaken to begin defining the physical characteristics of stars. However, many stars lack even this basic information, which is the foundation for later research to constrain stellar effective temperatures, masses, radial velocities, the number of stars in the system, and age. This research obtained visible-λ stellar spectra via the testing and commissioning of a Santa Barbara Instruments Group (SBIG) Self-Guiding Spectrograph (SGS) at the UND Observatory. Utilizing a 16-inch-aperture telescope on Internet Observatory #3, the SGS obtained spectra of GSC 4461-698 and GSC 4466-870 in the low-resolution mode using an 18-µm wide slit with dispersion of 4.3 Å/pixel, resolution of 8 Å, and a spectral range from 3800-7500 Å. Observational protocols include automatic bias/dark frame subtraction for each stellar spectrum obtained. This was followed by spectral averaging to obtain a combined spectrum for each star observed. Image calibration and spectral averaging was performed using the software programs, Maxim DL, Image J, Microsoft Excel, and Winmk. A wavelength calibration process was used to obtain spectra of an Hg/Ne source that allowed the conversion of spectrograph channels into wavelengths. Stellar emission and absorption lines, such as those for hydrogen (H) and helium (He), were identified, extracted, and rectified. Each average spectrum was compared to the MK stellar spectral standards to determine an initial spectral classification for each star. The hope is that successful completion of this project will allow long-term stellar spectral observations to begin at the UND Observatory.

Methods for multiple-telescope beam imaging and guiding in the near-infrared

NASA Astrophysics Data System (ADS)

Anugu, N.; Amorim, A.; Gordo, P.; Eisenhauer, F.; Pfuhl, O.; Haug, M.; Wieprecht, E.; Wiezorrek, E.; Lima, J.; Perrin, G.; Brandner, W.; Straubmeier, C.; Le Bouquin, J.-B.; Garcia, P. J. V.

2018-05-01

Atmospheric turbulence and precise measurement of the astrometric baseline vector between any two telescopes are two major challenges in implementing phase-referenced interferometric astrometry and imaging. They limit the performance of a fibre-fed interferometer by degrading the instrument sensitivity and the precision of astrometric measurements and by introducing image reconstruction errors due to inaccurate phases. A multiple-beam acquisition and guiding camera was built to meet these challenges for a recently commissioned four-beam combiner instrument, GRAVITY, at the European Southern Observatory Very Large Telescope Interferometer. For each telescope beam, it measures (a) field tip-tilts by imaging stars in the sky, (b) telescope pupil shifts by imaging pupil reference laser beacons installed on each telescope using a 2 × 2 lenslet and (c) higher-order aberrations using a 9 × 9 Shack-Hartmann. The telescope pupils are imaged to provide visual monitoring while observing. These measurements enable active field and pupil guiding by actuating a train of tip-tilt mirrors placed in the pupil and field planes, respectively. The Shack-Hartmann measured quasi-static aberrations are used to focus the auxiliary telescopes and allow the possibility of correcting the non-common path errors between the adaptive optics systems of the unit telescopes and GRAVITY. The guiding stabilizes the light injection into single-mode fibres, increasing sensitivity and reducing the astrometric and image reconstruction errors. The beam guiding enables us to achieve an astrometric error of less than 50 μas. Here, we report on the data reduction methods and laboratory tests of the multiple-beam acquisition and guiding camera and its performance on-sky.

The star identification, pointing and tracking system of UVSTAR, an attached payload instrument system for the Shuttle Hitchhiker-M platform

NASA Technical Reports Server (NTRS)

Decarlo, Francesco; Stalio, Roberto; Trampus, Paolo; Broadfoot, A. Lyle; Sandel, Bill R.; Sicuranza, Giovanni

1993-01-01

We describe an algorithm for star identification and pointing/tracking of a spaceborne electro-optical system and simulation analyses to test the algorithm. The algorithm will be implemented in the guiding system of UVSTAR, a spectrographic telescope for observations of astronomical and planetary sources operating in the 500-1250 A waveband at approximately 1 A resolution. The experiment is an attached payload and will fly as a Hitchhiker-M payload on the Shuttle. UVSTAR includes capabilities for independent target acquisition and tracking. The spectrograph package has internal gimbals that allow angular movement of plus or minus 3 deg from the central position. Rotation about the azimuth axis (parallel to the Shuttle z axis) and elevation axis (parallel to the Shuttle x axis) will actively position the field of view to center the target of interest in the fields of the spectrographs. The algorithm is based on an on-board catalog of stars. To identify star fields, the algorithm compares the positions of stars recorded by the guiding imager to positions computed from the on-board catalog. When the field has been identified, its position within the guiding imager field of view can be used to compute the pointing corrections necessary to point to a target of interest. In tracking mode, the software uses the past history to predict the quasi-periodic attitude control motions of the shuttle and sends pointing commands to cancel the motion and stabilize UVSTAR on the target. The guiding imager (guider) will have an 80-mm focal length and f/1.4 optics giving a field of view of 6 deg x 4.5 deg using a 385 x 288 pixel intensified CCD. It will be capable of providing high accuracy (better than 2 arc-sec) attitude determination from coarse (6 deg x 4.5 deg) initial knowledge of the pointing direction; and of pointing toward the target. It will also be capable of tracking at the same high accuracy with a processing time of less than a few hundredths of a second.

An analysis of the Hubble Space Telescope fine guidance sensor fine lock mode

NASA Technical Reports Server (NTRS)

Taff, L. G.

1991-01-01

There are two guiding modes of the Hubble Space Telescope (HST) used for the acquisition of astronomical data by one of its six scientific instruments. The more precise one is called Fine Lock. Command and control problems in the onboard electronics has limited Fine Lock to brighter stars, V less than 13.0 mag, instead of fulfilling its goal of V = 14.5 mag. Consequently, the less precise guiding mode of Coarse Track (approximately 40 milli-arc seconds) has to be used fairly frequently. Indeed, almost half of the scientific observations to have been made with the HST will be compromised. The only realistic or extensive simulations of the Fine Lock guidance mode are reported. The theoretical analysis underlying the Monte Carlo experiments and the numerical computations clearly show both that the control electronics are severely under-engineered and how to adjust the various control parameters to successfully extend Fine Lock guiding performance back to V = 14.0 mag and sometimes beyond.

Migration in the shearing sheet and estimates for young open cluster migration

NASA Astrophysics Data System (ADS)

Quillen, Alice C.; Nolting, Eric; Minchev, Ivan; De Silva, Gayandhi; Chiappini, Cristina

2018-04-01

Using tracer particles embedded in self-gravitating shearing sheet N-body simulations, we investigate the distance in guiding centre radius that stars or star clusters can migrate in a few orbital periods. The standard deviations of guiding centre distributions and maximum migration distances depend on the Toomre or critical wavelength and the contrast in mass surface density caused by spiral structure. Comparison between our simulations and estimated guiding radii for a few young supersolar metallicity open clusters, including NGC 6583, suggests that the contrast in mass surface density in the solar neighbourhood has standard deviation (in the surface density distribution) divided by mean of about 1/4 and larger than measured using COBE data by Drimmel and Spergel. Our estimate is consistent with a standard deviation of ˜0.07 dex in the metallicities measured from high-quality spectroscopic data for 38 young open clusters (<1 Gyr) with mean galactocentric radius 7-9 kpc.

Controlling the Laser Guide Star power density distribution at Sodium layer by combining Pre-correction and Beam-shaping

NASA Astrophysics Data System (ADS)

Huang, Jian; Wei, Kai; Jin, Kai; Li, Min; Zhang, YuDong

2018-06-01

The Sodium laser guide star (LGS) plays a key role in modern astronomical Adaptive Optics Systems (AOSs). The spot size and photon return of the Sodium LGS depend strongly on the laser power density distribution at the Sodium layer and thus affect the performance of the AOS. The power density distribution is degraded by turbulence in the uplink path, launch system aberrations, the beam quality of the laser, and so forth. Even without any aberrations, the TE00 Gaussian type is still not the optimal power density distribution to obtain the best balance between the measurement error and temporal error. To optimize and control the LGS power density distribution at the Sodium layer to an expected distribution type, a method that combines pre-correction and beam-shaping is proposed. A typical result shows that under strong turbulence (Fried parameter (r0) of 5 cm) and for a quasi-continuous wave Sodium laser (power (P) of 15 W), in the best case, our method can effectively optimize the distribution from the Gaussian type to the "top-hat" type and enhance the photon return flux of the Sodium LGS; at the same time, the total error of the AOS is decreased by 36% with our technique for a high power laser and poor seeing.

3D mapping of turbulence: a laboratory experiment

NASA Astrophysics Data System (ADS)

Le Louarn, Miska; Dainty, Christopher; Paterson, Carl; Tallon, Michel

2000-07-01

In this paper, we present the first experimental results of the 3D mapping method. 3D mapping of turbulence is a method to remove the cone effect with multiple laser guide stars and multiple deformable mirrors. A laboratory experiment was realized to verify the theoretical predictions. The setup consisted of two turbulent phase screens (made with liquid crystal devices) and a Shack-Hartmann wavefront sensor. We describe the interaction matrix involved in reconstructing Zernike commands for multiple deformable mirror from the slope measurements made from laser guide stars. It is shown that mirror commands can indeed be reconstructed with the 3D mapping method. Limiting factors of the method, brought to light by this experiment are discussed.

Astronomy: Minds-on the Universe. Supplemental Teaching Activities for Grades K-8.

ERIC Educational Resources Information Center

Marble, Stephen; Fowler, Marilyn, Ed.

This teachers guide contains activities and materials created to teach astronomy concepts to children from grades K-8. It is organized into four units: (1) Earth and Stars; (2) Spheres and Orbits; (3) Stars and Gravity; and (4) Scales and Measurement. Activities are arranged within each unit around six content topics: (1) Earth; (2) Solar System;…

Five-Star Schools: Defining Quality in Early Childhood Programs

ERIC Educational Resources Information Center

Hertzog, Nancy B.

2012-01-01

Hakeem, Emily, Jose, and Latisha are all entering preschool in the fall. Their mothers are looking for the highest quality early childhood program they can find. Is there a guide for them to find a five-star program? Are all certified or accredited programs of equal quality? How do these parents and guardians know what defines quality in early…

Seeing in a New Light: Astro-1 Teacher's Guide with Activities.

ERIC Educational Resources Information Center

Essex Corp., Huntsville, AL.

For as long as people have walked the Earth, they have looked to the stars, have been inspired by their beauty and remoteness and have found their way over sea and deserts by their guidance. Since then, enormous progress has been made in the understanding of the stars, and today the expanding and fascinating world of high-energy astronomy awaits…

Comparison between the Juno Earth flyby magnetic measurements and the magnetometer package on the IRIS solar observatory

NASA Astrophysics Data System (ADS)

Merayo, J. M.; Connerney, J. E.; Joergensen, J. L.; Dougherty, B.

2013-12-01

In October 2013 the NASA's Juno New Frontier spacecraft will perform an Earth Flyby Gravity Assist. During this flyby, Juno will reach an altitude of about 600 km and the magnetometer experiment will measure the magnetic field with very high precision. In June 2013 the NASA's IRIS solar observatory was successfully launched. IRIS uses a very fine guiding telescope in order to maintain a high pointing accuracy, assisted by a very high accuracy star tracker and a science grade vector magnetometer. IRIS was placed into a Sun-synchronous orbit at about 600 km altitude by a Pegasus rocket from the Vandenberg Air Force Base in California. This platform will also allow to performing measurements of the Earth's magnetic field with very high precision, since it carries similar instrumentation as on the Swarm satellites (star trackers and magnetometer). The data recorded by the Juno magnetic experiment and the IRIS magnetometer will bring a very exciting opportunity for comparing the two experiments as well as for determining current structures during the flyby.

Visual Outcomes After LASIK Using Topography-Guided vs Wavefront-Guided Customized Ablation Systems.

PubMed

Toda, Ikuko; Ide, Takeshi; Fukumoto, Teruki; Tsubota, Kazuo

2016-11-01

To evaluate the visual performance of two customized ablation systems (wavefront-guided ablation and topography-guided ablation) in LASIK. In this prospective, randomized clinical study, 68 eyes of 35 patients undergoing LASIK were enrolled. Patients were randomly assigned to wavefront-guided ablation using the iDesign aberrometer and STAR S4 IR Excimer Laser system (Abbott Medical Optics, Inc., Santa Ana, CA) (wavefront-guided group; 32 eyes of 16 patients; age: 29.0 ± 7.3 years) or topography-guided ablation using the OPD-Scan aberrometer and EC-5000 CXII excimer laser system (NIDEK, Tokyo, Japan) (topography-guided group; 36 eyes of 19 patients; age: 36.1 ± 9.6 years). Preoperative manifest refraction was -4.92 ± 1.95 diopters (D) in the wavefront-guided group and -4.44 ± 1.98 D in the topography-guided group. Visual function and subjective symptoms were compared between groups before and 1 and 3 months after LASIK. Of seven subjective symptoms evaluated, four were significantly milder in the wavefront-guided group at 3 months. Contrast sensitivity with glare off at low spatial frequencies (6.3° and 4°) was significantly higher in the wavefront-guided group. Uncorrected and corrected distance visual acuity, manifest refraction, and higher order aberrations measured by OPD-Scan and iDesign were not significantly different between the two groups at 1 and 3 months after LASIK. Both customized ablation systems used in LASIK achieved excellent results in predictability and visual function. The wavefront-guided ablation system may have some advantages in the quality of vision. It may be important to select the appropriate system depending on eye conditions such as the pattern of total and corneal higher order aberrations. [J Refract Surg. 2016;32(11):727-732.]. Copyright 2016, SLACK Incorporated.

Student Measurements of Double Star STF 747AB

NASA Astrophysics Data System (ADS)

Bateman, Grace; Funk, Benjamin; Gillette, Travis; Rhoades, Breauna; Rhoades, Mark; Schlosser, Ruth; Sharpe, Scott; Thompson, Leone

2017-04-01

Data gathered from a 22-Inch Newtonian Alt/Az telescope and a Celestron Micro Guide eyepiece were used to measure the double star STF 747AB. Students from Apple Valley High School determined the separation to be 39.97 arc sec and the position angle to be 227.91 degrees. The students also used data from the digitized sky survey and determined a separation of 39.99 arc sec and a position angle of 225 degrees. The research was semi-independent from the Vanguard Double Star Workshop 2016 in Apple Valley, California.

Asteroseismology and mass loss in Be stars. Study with CoRoT

NASA Astrophysics Data System (ADS)

Diago, P. D.

The general aim of this work is the study of Be stars with the CoRoT space mission. The mechanisms responsible of the production and dynamics of the circumstellar gas in Be stars are still not constrained. Observations of non-radial pulsation beating phenomena connected to outbursts point toward a relevance of pulsation, but this mechanism cannot be generalized. In this regard, the observation of classical Be stars with the high-precision CoRoT satellite is providing important keys to understand the physics of these objects and the nature of the Be phenomenon. In order to study the light variations of the selected stars we use photometric and spectroscopic observations. These observations allow us to extract frequencies, amplitudes and phases of these variations. As we will show, these light variations can be connected with pulsations on the stellar surface. For carrying out the frequency analysis we have developed a new code based on standard Fourier analysis. The point is that this code, called PASPER, allows the frequency analysis of large sets of light curves in an automatic mode. This Ph.D. thesis is arranged as follows: In the first three Chapters we describe the scientific framework of this project, giving a brief description on Asteroseismology, presenting the current status of Be stars, and describing the basics of the Fourier analysis and the rudiments of the time series analysis. At the early begin of this Ph.D. thesis, the CoRoT satellite was still on ground getting ready for the launch. In this context, we perform a search for short-period B and Be star variables in the low metallicity environment of the Magellanic Clouds. This study constitutes the Part I of this Ph.D. thesis. This Part has a double goal: i) to test the frequency analysis codes; and ii) to detect observationally beta Cephei and SPB-like B-type pulsators in low metallicity environments, actually not predicted by the pulsational theory and models. This constitutes the PartI. Part II is devoted to the study of Be stars with the CoRoT space mission. Here we depict a complete review on the CoRoT mission. We also describe the results on the analysis of three Be stars from the CoRoT exoplanet field. Finally, we present the results on the frequency analysis of the late Be star HD50209, observed in the seismology field of the \\corot satellite. The analysis of this Be star has revealed up to sixty frequencies, grouped in six different and separated sets, attributed to g-mode pulsations. Finally, we resume the main conclusions of the whole project, including prospects and future work to be done. An addendum with all the published results derived from this project has been added at the end of this Part II. Part III encloses the Appendixes, providing a brief summary of this work in Spanish, a complete description on basic equations of non-radial oscillation, the user guide of the PASPER code and the user guide of the KURTZ_BOS code.

Reducing Energy Use in Existing Homes by 30%: Learning From Home Performance with ENERGY STAR

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liaukus, C.

2014-12-01

The improvement of existing homes in the United States can have a much greater impact on overall residential energy use than the construction of highly efficient new homes. There are over 130 million existing housing units in the U.S., while annually new construction represents less than two percent of the total supply (U.S. Census Bureau, 2013). Therefore, the existing housing stock presents a clear opportunity and responsibility for Building America (BA) to guide the remodeling and retrofit market toward higher performance existing homes. There are active programs designed to improve the energy performance of existing homes. Home Performance with ENERGYmore » STAR (HPwES) is a market-rate program among them. BARA's research in this project verified that the New Jersey HPwES program is achieving savings in existing homes that meet or exceed BA's goal of 30%. Among the 17 HPwES projects with utility data included in this report, 15 have actual energy savings ranging from 24% to 46%. Further, two of the homes achieved that level of energy savings without the costly replacement of heating and cooling equipment, which indicates that less costly envelope packages could be offered to consumers unable to invest in more costly mechanical packages, potentially creating broader market impact.« less

Navigating Space by the Stars

NASA Image and Video Library

2018-06-19

A tool that has helped guide sailors across oceans for centuries is now being tested aboard the International Space Station as a potential emergency navigation tool for guiding future spacecraft across the cosmos. The Sextant Navigation investigation tests use of a hand-held sextant aboard the space station. Sextants have a telescope-like optical sight to take precise angle measurements between pairs of stars from land or sea, enabling navigation without computer assistance. NASA’s Gemini missions conducted the first sextant sightings from a spacecraft, and designers built a sextant into Apollo vehicles as a navigation backup in the event the crew lost communications from their spacecraft. Jim Lovell demonstrated on Apollo 8 that sextant navigation could return a space vehicle home. Astronauts conducted additional sextant experiments on Skylab. Read more about the Sextant experiment happening aboard the space station: https://www.nasa.gov/mission_pages/station/research/news/Sextant_ISS HD Download: https://archive.org/details/jsc2018m000418_Navigating_Space_by_the_Stars

Navigating Space by the Stars - 16x9

NASA Image and Video Library

2018-06-18

A tool that has helped guide sailors across oceans for centuries is now being tested aboard the International Space Station as a potential emergency navigation tool for guiding future spacecraft across the cosmos. The Sextant Navigation investigation tests use of a hand-held sextant aboard the space station. Sextants have a telescope-like optical sight to take precise angle measurements between pairs of stars from land or sea, enabling navigation without computer assistance. NASA’s Gemini missions conducted the first sextant sightings from a spacecraft, and designers built a sextant into Apollo vehicles as a navigation backup in the event the crew lost communications from their spacecraft. Jim Lovell demonstrated on Apollo 8 that sextant navigation could return a space vehicle home. Astronauts conducted additional sextant experiments on Skylab. Read more about the Sextant experiment happening aboard the space station: https://www.nasa.gov/mission_pages/station/research/news/Sextant_ISS HD Download: https://archive.org/details/jsc2018m000418_Navigating_Space_by_the_Stars

The Gravity Probe B Experiment

NASA Technical Reports Server (NTRS)

Kolodziejczak, Jeffrey

2008-01-01

This presentation briefly describes the Gravity Probe B (GP-B) Experiment which is designed to measure parts of Einstein's general theory of relativity by monitoring gyroscope orientation relative to a distant guide star. To measure the miniscule angles predicted by Einstein's theory, it was necessary to build near-perfect gyroscopes that were approximately 50 million times more precise than the best navigational gyroscopes. A telescope mounted along the central axis of the dewar and spacecraft provided the experiment's pointing reference to a guide star. The telescope's image divide precisely split the star's beam into x-axis and y-axis components whose brightness could be compared. GP-B's 650-gallon dewar, kept the science instrument inside the probe at a cryogenic temperature for 17.3 months and also provided the thruster propellant for precision attitude and translation control. Built around the dewar, the GP-B spacecraft was a total-integrated system, comprising both the space vehicle and payload, dedicated as a single entity to experimentally testing predictions of Einstein's theory.

New CO and HCN sources associated with IRAS carbon stars

NASA Technical Reports Server (NTRS)

NGUYEN-Q-RIEU; Epchtein, N.; TRUONG-BACH; Cohen, M.

1987-01-01

Emission of CO and HCN was detected in 22 out of a sample of 53 IRAS sources classified as unidentified carbon-rich objects. The sample was selected according to the presence of the silicon carbide feature as revealed by low-resolution spectra. The molecular line widths indicate that the CO and HCN emission arises from the circumstellar envelopes of very highly evolved stars undergoing mass loss. The visible stars tend to be deficient in CO as compared with unidentified sources. Most the detected CO and HCN IRAS stars are distinct and thick-shelled objects, but their infrared and CO luminosities are similar to those of IRC + 102156 AFGL and IRC-CO evolved stars. The 12 micron flux seems to be a good indicator of the distance, hence a guide for molecular searches.

Adaptive optics system for Cassegrain focus of SUBARU 8.2-m telescope

NASA Astrophysics Data System (ADS)

Takami, Hideki; Takato, Naruhisa; Otsubo, Masashi; Kanzawa, Tomio; Kamata, Yukiko; Nakashima, Koji; Iye, Masanori

1998-09-01

The adaptive optics system for Subaru 8.2m telescope of the National Astronomical Observatory Japan has been developed for the Cassegrain ear-IR instruments, CIAO and IRCS. The system consists of a wavefront curvature sensor with 36 subaperture photon-counting avalanche photodiode modules and a bimorph deformable mirror with 36 electrodes. The expected Strehl ratio at K band exceeds 0.4 for objects that are located close enough to a bright guide star as faint as R equals 16 mag at the median seeing of 0.45 arcsec at Mauna Kea. The system will be in operation in 1999 as a natural guide star system, and will eventually be upgraded to a laser guide star system in cooperating an IR wavefront tilt sensor to provide nearly full sky. The construction of this common use system to Subaru telescope is now underway in our laboratory in Tokyo. Prior to starting the fabrication of this common use system, a full size prototype system was constructed and tested with the 1.6 m IR telescope at our observatory in Tokyo. This system has the identical optical design, deformable mirror, loop control computer to those for the Subaru system, while the wavefront sensing detectors were less-sensitive analog APDs. We succeeded in getting closed loop images of stars in K band with diffraction limited core. The Strehl ratio was around 0.5 and the factor of improvement was about 20 at K-band under the average seeing of 2 arcsec during the observation. The loop sped of the system was 2 K corrections per second.

NAOMI: a low-order adaptive optics system for the VLT interferometer

NASA Astrophysics Data System (ADS)

Gonté, Frédéric Yves J.; Alonso, Jaime; Aller-Carpentier, Emmanuel; Andolfato, Luigi; Berger, Jean-Philippe; Cortes, Angela; Delplancke-Strobele, Françoise; Donaldson, Rob; Dorn, Reinhold J.; Dupuy, Christophe; Egner, Sebastian E.; Huber, Stefan; Hubin, Norbert; Kirchbauer, Jean-Paul; Le Louarn, Miska; Lilley, Paul; Jolley, Paul; Martis, Alessandro; Paufique, Jérôme; Pasquini, Luca; Quentin, Jutta; Ridings, Robert; Reyes, Javier; Shchkaturov, Pavel; Suarez, Marcos; Phan Duc, Thanh; Valdes, Guillermo; Woillez, Julien; Le Bouquin, Jean-Baptiste; Beuzit, Jean-Luc; Rochat, Sylvain; Vérinaud, Christophe; Moulin, Thibaut; Delboulbé, Alain; Michaud, Laurence; Correia, Jean-Jacques; Roux, Alain; Maurel, Didier; Stadler, Eric; Magnard, Yves

2016-08-01

The New Adaptive Optics Module for Interferometry (NAOMI) will be developed for and installed at the 1.8-metre Auxiliary Telescopes (ATs) at ESO Paranal. The goal of the project is to equip all four ATs with a low-order Shack- Hartmann adaptive optics system operating in the visible. By improving the wavefront quality delivered by the ATs for guide stars brighter than R = 13 mag, NAOMI will make the existing interferometer performance less dependent on the seeing conditions. Fed with higher and more stable Strehl, the fringe tracker(s) will achieve the fringe stability necessary to reach the full performance of the second-generation instruments GRAVITY and MATISSE.

Distributed Kalman filtering compared to Fourier domain preconditioned conjugate gradient for laser guide star tomography on extremely large telescopes.

PubMed

Gilles, Luc; Massioni, Paolo; Kulcsár, Caroline; Raynaud, Henri-François; Ellerbroek, Brent

2013-05-01

This paper discusses the performance and cost of two computationally efficient Fourier-based tomographic wavefront reconstruction algorithms for wide-field laser guide star (LGS) adaptive optics (AO). The first algorithm is the iterative Fourier domain preconditioned conjugate gradient (FDPCG) algorithm developed by Yang et al. [Appl. Opt.45, 5281 (2006)], combined with pseudo-open-loop control (POLC). FDPCG's computational cost is proportional to N log(N), where N denotes the dimensionality of the tomography problem. The second algorithm is the distributed Kalman filter (DKF) developed by Massioni et al. [J. Opt. Soc. Am. A28, 2298 (2011)], which is a noniterative spatially invariant controller. When implemented in the Fourier domain, DKF's cost is also proportional to N log(N). Both algorithms are capable of estimating spatial frequency components of the residual phase beyond the wavefront sensor (WFS) cutoff frequency thanks to regularization, thereby reducing WFS spatial aliasing at the expense of more computations. We present performance and cost analyses for the LGS multiconjugate AO system under design for the Thirty Meter Telescope, as well as DKF's sensitivity to uncertainties in wind profile prior information. We found that, provided the wind profile is known to better than 10% wind speed accuracy and 20 deg wind direction accuracy, DKF, despite its spatial invariance assumptions, delivers a significantly reduced wavefront error compared to the static FDPCG minimum variance estimator combined with POLC. Due to its nonsequential nature and high degree of parallelism, DKF is particularly well suited for real-time implementation on inexpensive off-the-shelf graphics processing units.

Radiative Feedback from Massive Stars as Traced by Multiband Imaging and Spectroscopic Mosaics

NASA Astrophysics Data System (ADS)

Berne, Olivier; Habart, Emilie; Peeters, Els; Abergel, A.; Bergin, E.; Bernard-Salas, J.; Bron, E.; Cami, J.; Cazaux, S.; Dartois, E.; Fuente, A.; Goicoechea, J.; Gordon, K.; Onaka, T.; Robberto, M.; Roellig, M.; Tielens, A.; Vincente, S.; Wolfire, M.; Okada, Y.

2017-11-01

Massive stars disrupt their natal molecular cloud material by dissociating molecules, ionizing atoms and molecules, and heating the gas and dust. These processes drive the evolution of interstellar matter in our Galaxy and throughout the Universe from the era of vigorous star formation at redshifts of 1-3, to the present day. Much of this interaction occurs in Photo-Dissociation Regions (PDRs) where far-ultraviolet photons of these stars create a largely neutral, but warm region of gas and dust. PDR emission dominates the IR spectra of star-forming galaxies and also provides a unique tool to study in detail the physical and chemical processes that are relevant for most of the mass in inter- and circumstellar media including diffuse clouds, protoplanetary disk- and molecular cloud surfaces, globules, planetary nebulae, and starburst galaxies. We propose to provide template datasets designed to identify key PDR characteristics in JWST spectra in order to guide the preparation of Cycle 2 proposals on star-forming regions in our Galaxy and beyond. We plan to obtain the first spatially resolved, high spectral resolution IR observations of a PDR using NIRCam, NIRSpec, and MIRI. These data will test widely used theoretical models and extend them into the JWST era. We have engaged the broader community as exemplified by the supporting large international team of 138 scientists. We will assist the community interested in JWST observations of PDRs through science-enabling products that will guide observational planning and allow fast data analysis. We will train the community through telecons and dedicated workshops.

Thematic Journeys. I'll Never Draw a Perfect Star

ERIC Educational Resources Information Center

Zingher, Gary

2004-01-01

Children take enormous pride in their drawing abilities. They like bringing to life a specific object whether it is a star or a cat or a tree, and they will likely be frustrated until they can get it just right. Drawing is a way of thinking in motion, the brain guiding the hand, and it demonstrates strongly another type of intelligence. As a…

First laboratory results with the LINC-NIRVANA high layer wavefront sensor.

PubMed

Zhang, Xianyu; Gaessler, Wolfgang; Conrad, Albert R; Bertram, Thomas; Arcidiacono, Carmelo; Herbst, Thomas M; Kuerster, Martin; Bizenberger, Peter; Meschke, Daniel; Rix, Hans-Walter; Rao, Changhui; Mohr, Lars; Briegel, Florian; Kittmann, Frank; Berwein, Juergen; Trowitzsch, Jan; Schreiber, Laura; Ragazzoni, Roberto; Diolaiti, Emiliano

2011-08-15

In the field of adaptive optics, multi-conjugate adaptive optics (MCAO) can greatly increase the size of the corrected field of view (FoV) and also extend sky coverage. By applying layer oriented MCAO (LO-MCAO) [4], together with multiple guide stars (up to 20) and pyramid wavefront sensors [7], LINC-NIRVANA (L-N for short) [1] will provide two AO-corrected beams to a Fizeau interferometer to achieve 10 milliarcsecond angular resolution on the Large Binocular Telescope. This paper presents first laboratory results of the AO performance achieved with the high layer wavefront sensor (HWS). This sensor, together with its associated deformable mirror (a Xinetics-349), is being operated in one of the L-N laboratories. AO reference stars, spread across a 2 arc-minute FoV and with aberrations resulting from turbulence introduced at specific layers in the atmosphere, are simulated in this lab environment. This is achieved with the Multi-Atmosphere Phase screen and Stars (MAPS) [2] unit. From the wavefront data, the approximate residual wavefront error after correction has been calculated for different turbulent layer altitudes and wind speeds. Using a somewhat undersampled CCD, the FWHM of stars in the nearly 2 arc-minute FoV has also been measured. These test results demonstrate that the high layer wavefront sensor of LINC-NIRVANA will be able to achieve uniform AO correction across a large FoV. © 2011 Optical Society of America

Look to the Sky. An All-Purpose Interdisciplinary Guide to Astronomy. Grades 4-12.

ERIC Educational Resources Information Center

DeBruin, Jerry; Murad, Don

This guide features materials and activities about stars for integration into other academic disciplines. Part one describes how to begin to look to the sky, including usage of the camera, binoculars, and telescope. Part two, "Keep Up to Date," introduces information on resource materials, such as astronomy books, magazines, newsletters,…

They Snooze, You Lose: The Educator's Guide to Successful Presentations

ERIC Educational Resources Information Center

Burmark, Lynell

2011-01-01

In today's increasingly visual world, the art of giving presentations is a much-needed talent. "They Snooze, You Lose", provides a comprehensive guide made especially for teachers and administrators who want to become presentation "stars" in their classrooms, at board meetings, or any time they are in front of an audience. This book describes how…

The Gemini-South MCAO operational model: insights on a new era of telescope operation

NASA Astrophysics Data System (ADS)

Trancho, Gelys; Bec, Matthieu; Artigau, Etienne; d'Orgeville, Celine; Gratadour, Damien; Rigaut, Francois J.; Walls, Brian

2008-07-01

The Gemini Observatory is implementing a Multi-Conjugate Adaptive Optics (MCAO) system as a facility instrument for the Gemini South telescope (GeMS). The system will include 5 Laser Guide Stars, 3 Natural Guide Stars, and 3 deformable mirrors, optically conjugated at different altitudes, to achieve near-uniform atmospheric compensation over a one arc minute square field of view. This setup implies some level of operational complexity. In this paper we describe how GeMS will be integrated into the flow of Gemini operations, from the observing procedures necessary to execute the programs in the queue (telescope control software, observing tools, sequence executor) to the safety implementation needed such as spotters/ASCAM, space command and laser traffic control software.

Nano-JASMINE: Simulation of Data Outputs

NASA Astrophysics Data System (ADS)

Kobayashi, Y.; Yano, T.; Hatsutori, Y.; Gouda, N.; Murooka, J.; Niwa, Y.; Yamada, Y.

We simulated the data outputs of the first Japanese astrometry satellite Nano-JASMINE, which is scheduled to be launched by the Cyclone-4 rocket in August 2011. The simulations were carried out using existing stellar catalogues such as the Hipparcos catalogue, the Tycho catalogue, and the Guide Star catalogue version 2.3. Several statics are shown such as the number of stars those will be measured distances using annual aberration observations. The method for determining the initial direction of the satellite's spin axis has also been discussed. In this case, the frequency of bright stars observed by the satellite is an important factor.

Design of pre-optics for laser guide star wavefront sensor for the ELT

NASA Astrophysics Data System (ADS)

Muslimov, Eduard; Dohlen, Kjetil; Neichel, Benoit; Hugot, Emmanuel

2017-12-01

In the present paper, we consider the optical design of a zoom system for the active refocusing in laser guide star wavefront sensors. The system is designed according to the specifications coming from the Extremely Large Telescope (ELT)-HARMONI instrument, the first-light, integral field spectrograph for the European (E)-ELT. The system must provide a refocusing of the laser guide as a function of telescope pointing and large decentring of the incoming beam. The system considers four moving lens groups, each of them being a doublet with one aspherical surface. The advantages and shortcomings of such a solution in terms of the component displacements and complexity of the surfaces are described in detail. It is shown that the system can provide the median value of the residual wavefront error of 13.8-94.3 nm and the maximum value <206 nm, while the exit pupil distortion is 0.26-0.36% for each of the telescope pointing directions.

The Universal Book of Astronomy: From the Andromeda Galaxy to the Zone of Avoidance

NASA Astrophysics Data System (ADS)

Darling, David

2003-10-01

The ultimate guide to the final frontier This alphabetical tour of the universe provides all the history, science, and up-to-the-minute facts needed to explore the skies with authority. Packed with more than 3,000 entries that cover everything from major observatories and space telescopes to biographies of astronomers throughout the ages, it showcases an extraordinary array of newfound wonders, including microquasars, brown dwarfs, and dark energy, as well as a host of individual comets, asteroids, moons, planets, stars, nebulas, and galaxies. Featuring nearly 200 illustrations and eight pages of color photographs, this comprehensive guide provides easy lookup of topics and offers more in-depth information than can be found in existing star guides or astronomy dictionaries. It's an ideal resource for the amateur astronomer or anyone with an interest in the mysteries of the cosmos. David Darling, PhD (Brainerd, MN), is the author of The Complete Book of Spaceflight (0-471-05649-9) and Equations of Eternity, a New York Times Notable Book.

The impact of interpretive and reductive front-of-pack labels on food choice and willingness to pay.

PubMed

Talati, Zenobia; Norman, Richard; Pettigrew, Simone; Neal, Bruce; Kelly, Bridget; Dixon, Helen; Ball, Kylie; Miller, Caroline; Shilton, Trevor

2017-12-19

This study examined how front-of-pack labels and product healthfulness affect choice and willingness to pay across a range of foods. It was hypothesized that: (i) product choice and (ii) willingness to pay would be more aligned with product healthfulness when healthfulness was expressed through the Health Star Rating, followed by the Multiple Traffic Light, then the Daily Intake Guide, and (iii) the Nutrition Facts Panel would be viewed infrequently. Adults and children aged 10+ years (n = 2069) completed an online discrete choice task involving mock food packages. A 4 food type (cookies, corn flakes, pizza, yoghurt) × 2 front-of-pack label presence (present, absent) × 3 front-of-pack label type (Daily Intake Guide, Multiple Traffic Light, Health Star Rating) × 3 price (cheap, moderate, expensive) × 3 healthfulness (less healthy, moderately healthy, healthier) design was used. A 30 s time limit was imposed for each choice. Of the three front-of-pack labels tested, the Health Star Rating produced the largest differences in choices, with 40% (95% CIs: 38%-42%) of respondents selecting the healthier variant, 33% selecting the moderately healthy variant (95% CIs: 31%-35%), and 23% (95% CIs: 21%-24%) selecting the less healthy variant of the four products included in the study. The Multiple Traffic Light led to significant differences in choices between healthier (35%, 95% CIs: 33%-37%) and less healthy products (29%, 95% CIs: 27%-31%), but not moderately healthy products (32%, 95% CIs: 30%-34%). No significant differences in choices were observed by product healthfulness when the Daily Intake Guide was present. Only the Health Star Rating resulted in a significantly greater willingness to pay for healthier versus less healthy products. The Nutrition Facts Panel was viewed for only 7% of all mock packages. Front-of-pack labels that are more interpretive, such as the Health Star Rating, can be more effective at directing consumers towards healthier choices than reductive front-of-pack labels such as the Daily Intake Guide. The study results provide policy makers with clear guidance on the types of front-of-pack labels that are most likely to achieve positive health outcomes at a population level.

A Cluster Of Activities On Coma From The Hubble Space Telescope, StarDate, And McDonald Observatory

NASA Astrophysics Data System (ADS)

Hemenway, Mary Kay; Jogee, S.; Fricke, K.; Preston, S.

2011-01-01

With a goal of providing a vast audience of students, teachers, the general public, and Spanish-speakers with activities to learn about research on the Coma cluster of galaxies based on the HST ACS Treasury survey of Coma, McDonald Observatory used a many-faceted approach. Since this research offered an unprecedented legacy dataset, part of the challenge was to convey the importance of this project to a diverse audience. The methodology was to create different products for different (overlapping) audiences. Five radio programs were produced in English and Spanish for distribution on over 500 radio stations in the US and Mexico with a listening audience of over 2 million; in addition to the radio listeners, there were over 13,000 downloads of the English scripts and almost 6000 of the Spanish. Images were prepared for use in the StarDate Online Astronomy Picture of the Week, for ViewSpace (used in museums), and for the StarDate/Universo Teacher Guide. A high-school level activity on the Coma Cluster was prepared and distributed both on-line and in an upgraded printed version of the StarDate/Universo Teacher Guide. This guide has been distributed to over 1700 teachers nationally. A YouTube video about careers and research in astronomy using the Coma cluster as an example was produced. Just as the activities were varied, so were the evaluation methods. This material is based upon work supported by the National Aeronautics and Space Administration under Grant/Contract/Agreement No. HST-EO-10861.35-A issued through the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.

Optics: Light, Color, and Their Uses. An Educator's Guide with Activities in Science and Mathematics.

ERIC Educational Resources Information Center

National Aeronautics and Space Administration, Huntsville, AL. George C. Marshall Space Flight Center.

This educator's guide from discusses optics, light, color and their uses. Activities include: (1) "Reflection of Light with a Plane (Flat) Mirror--Trace a Star"; (2) "Reflection of Light with Two Plane Mirrors--Double Mirrors Placed at a 90-Degree Angle"; (3) "Reflection of Light with Two Plane Mirrors--Double Mirrors Placed at a Number of…

Resource Handbook--Space Beyond the Earth. A Supplement to Basic Curriculum Guide--Science, Grades K-6.

ERIC Educational Resources Information Center

Starr, John W., 3rd., Ed.

GRADES OR AGES: Grades K-6. SUBJECT MATTER: Science; space. ORGANIZATION AND PHYSICAL APPEARANCE: The guide is divided into four units: 1) the sun, earth, and moon; 2) stars and planets; 3) exploring space; 4) man's existence in space. Each unit includes initiatory and developmental activities. There are also sections on evaluation, vocabulary,…

Aerodynamic performance of a fan stage utilizing variable inlet guide vanes (VIGV's) for thrust modulation. [subsonic V/STOL aircraft

NASA Technical Reports Server (NTRS)

Woollett, R. R.

1983-01-01

An experimental research program was conducted in the Lewis Research Center's 9 x 15-foot (2.74 x 4.57 m) low speed wind tunnel to evaluate the aerodynamic performance of an inlet and fan system with variable inlet guide vanes (VIGVs) for use on a subsonic V/STOL aircraft. At high VIGV blade angles (lower weight flow and thrust levels), the fan stage was stalled over a major portion of its radius. In spite of the stall, fan blade stresses only exceeded the limits at the most extreme flow conditions. It was found that inlet flow separation does not necessarily lead to poor inlet performance or adverse fan operating conditions. Generally speaking, separated inlet flow did not adversely affect the fan blade stress levels. There were some cases, however, at high VIGV angles and high inlet angles-of-attack where excessive blade stress levels were encountered. An evaluation term made up of the product of the distortion parameter, K alpha, the weight flow and the fan pressure ratio minus one, was found to correlate quite well with the observed blade stress results. Previously announced in STAR as N83-27957

Radiative Feedback from Massive Stars as Traced by Multiband Imaging and Spectroscopic Mosaics

NASA Astrophysics Data System (ADS)

Tielens, Alexander; "PDRs4ever" team

2018-06-01

Massive stars disrupt their natal molecular cloud material by dissociating molecules, ionizing atoms and molecules, and heating the gas and dust. These processes drive the evolution of interstellar matter in our Galaxy and throughout the Universe from the era of vigorous star formation at redshifts of 1-3, to the present day. Much of this interaction occurs in Photo-Dissociation Regions (PDRs) where far-ultraviolet photons of these stars create a largely neutral, but warm region of gas and dust. PDR emission dominates the IR spectra of star-forming galaxies and also provides a unique tool to study in detail the physical and chemical processes that are relevant for inter- and circumstellar media including diffuse clouds, molecular cloud and protoplanetary disk surfaces, globules, planetary nebulae, and starburst galaxies.We propose to provide template datasets designed to identify key PDR characteristics in the full 1-28 μm JWST spectra in order to guide the preparation of Cycle 2 proposals on star-forming regions in our Galaxy and beyond. We plan to obtain the first spatially resolved, high spectral resolution IR observations of a PDR using NIRCam, NIRSpec and MIRI. We will observe a nearby PDR with well-defined UV illumination in a typical massive star-forming region. JWST observations will, for the first time, spatially resolve and perform a tomography of the PDR, revealing the individual IR spectral signatures from the key zones and sub-regions within the ionized gas, the PDR and the molecular cloud. These data will test widely used theoretical models and extend them into the JWST era. We will assist the community interested in JWST observations of PDRs through several science-enabling products (maps of spectral features, template spectra, calibration of narrow/broad band filters in gas lines and PAH bands, data-interpretation tools e.g. to infer gas physical conditions or PAH and dust characteristics). This project is supported by a large international team of one hundred scientists collaborators.

GALACSI system design and analysis

NASA Astrophysics Data System (ADS)

Ströbele, S.; La Penna, P.; Arsenault, R.; Conzelmann, R. D.; Delabre, B.; Duchateau, M.; Dorn, R.; Fedrigo, E.; Hubin, N.; Quentin, J.; Jolley, P.; Kiekebusch, M.; Kirchbauer, J. P.; Klein, B.; Kolb, J.; Kuntschner, H.; Le Louarn, M.; Lizon, J. L.; Madec, P.-Y.; Pettazzi, L.; Soenke, C.; Tordo, S.; Vernet, J.; Muradore, R.

2012-07-01

GALACSI is one of the Adaptive Optics (AO) systems part of the ESO Adaptive Optics Facility (AOF). It will use the VLT 4-Laser Guide Stars system, high speed and low noise WaveFront Sensor cameras (<1e-, 1000Hz) the Deformable Secondary Mirror (DSM) and the SPARTA Real Time Computer to sharpen images and enhance faint object detectability of the MUSE Instrument. MUSE is an Integral Field Spectrograph working at wavelengths from 465nm to 930nm. GALACSI implements 2 different AO modes; in Wide Field Mode (WFM) it will perform Ground Layer AO correction and enhance the collected energy in a 0.2" by 0.2" pixel by a factor 2 at 750nm over a Field of View (FoV) of 1' by 1'. The 4 LGSs and one tip tilt reference star (R-mag <17.5) are located outside the MUSE FoV. Key requirements are to provide this performance and a very good image stability for a 1hour long integration time. In Narrow Field Mode (NFM) Laser Tomography AO will be used to reconstruct and correct the turbulence for the center field using the 4 LGSs at 15" off axis and the Near Infra Red (NIR) light of one reference star on axis for tip tilt and focus sensing. In NFM GALACSI will provide a moderate Strehl Ratio of 5% (goal 10%) at 650nm. The NFM hosts several challenges and many subsystems will be pushed to their limits. The opto mechanical design and error budgets of GALACSI is described here.

A new approach of the Star Excursion Balance Test to assess dynamic postural control in people complaining from chronic ankle instability.

PubMed

Pionnier, Raphaël; Découfour, Nicolas; Barbier, Franck; Popineau, Christophe; Simoneau-Buessinger, Emilie

2016-03-01

The purpose of this study was to quantitatively and qualitatively assess dynamic balance with accuracy in individuals with chronic ankle instability (CAI). To this aim, a motion capture system was used while participants performed the Star Excursion Balance Test (SEBT). Reached distances for the 8 points of the star were automatically computed, thereby excluding any dependence to the experimenter. In addition, new relevant variables were also computed, such as absolute time needed to reach each distance, lower limb ranges of motion during unipodal stance, as well as absolute error of pointing. Velocity of the center of pressure and range of variation of ground reaction forces have also been assessed during the unipodal phase of the SEBT thanks to force plates. CAI group exhibited smaller reached distances and greater absolute error of pointing than the control group (p<0.05). Moreover, the ranges of motion of lower limbs joints, the velocity of the center of pressure and the range of variation of the ground reaction forces were all significantly smaller in the CAI group (p<0.05). These reduced quantitative and qualitative performances highlighted a lower dynamic postural control. The limited body movements and accelerations during the unipodal stance in the CAI group could highlight a protective strategy. The present findings could help clinicians to better understand the motor strategies used by CAI patients during dynamic balance and may guide the rehabilitation process. Copyright © 2016 Elsevier B.V. All rights reserved.

Research of centroiding algorithms for extended and elongated spot of sodium laser guide star

NASA Astrophysics Data System (ADS)

Shao, Yayun; Zhang, Yudong; Wei, Kai

2016-10-01

Laser guide stars (LGSs) increase the sky coverage of astronomical adaptive optics systems. But spot array obtained by Shack-Hartmann wave front sensors (WFSs) turns extended and elongated, due to the thickness and size limitation of sodium LGS, which affects the accuracy of the wave front reconstruction algorithm. In this paper, we compared three different centroiding algorithms , the Center-of-Gravity (CoG), weighted CoG (WCoG) and Intensity Weighted Centroid (IWC), as well as those accuracies for various extended and elongated spots. In addition, we compared the reconstructed image data from those three algorithms with theoretical results, and proved that WCoG and IWC are the best wave front reconstruction algorithms for extended and elongated spot among all the algorithms.

Status of the GTC adaptive optics: integration in laboratory

NASA Astrophysics Data System (ADS)

Reyes García-Talavera, M.; Béjar, V. J. S.; López, J. C.; López, R. L.; Martín, C.; Martín, Y.; Montilla, I.; Núñez, M.; Puga, M.; Rodríguez, L. F.; Tenegi, F.; Tubío, O.; Bello, D.; Cavaller, L.; Prieto, G.; Rosado, M.

2016-07-01

Since the beginning of the development of the Gran Telescopio Canarias (GTC), an Adaptive Optics (AO) system was considered necessary to exploit the full diffraction-limited potential of the telescope. The GTC AO system designed during the last years is based on a single deformable mirror conjugated to the telescope pupil, and a Shack-Hartmann wavefront sensor with 20 x 20 subapertures, using an OCAM2 camera. The GTCAO system will provide a corrected beam with a Strehl Ratio (SR) of 0.65 in K-band with bright natural guide stars. Most of the subsystems have been manufactured and delivered. The upgrade for the operation with a Laser Guide Star (LGS) system has been recently approved. The present status of the GTCAO system, currently in its laboratory integration phase, is summarized in this paper.

Concept for polychromatic laser guide stars: one-photon excitation of the 4P3/2 level of a sodium atom.

PubMed

Pique, Jean-Paul; Moldovan, Ioana Cristina; Fesquet, Vincent

2006-11-01

One challenge for polychromatic laser guide stars is to create a sufficiently intense source in the UV. The flux required for the measurement of differential tip-tilt is the main issue that we address. We describe a model that has been validated using on-sky data. We present a method that excites the 4P3/2 sodium level using a one-photon excitation at 330 nm. It is more efficient than the two-photon excitation previously suggested since its power slope flux is 3 x 10(4) photons/s/m2/W instead of 1.3 x 10(3) photons/s/m2/W. This method is very promising both in terms of flux and system simplicity.

The Laser Guide Star System for Adaptive Optics at Subaru Telescope

NASA Astrophysics Data System (ADS)

Hayano, Y.; Saito, Y.; Ito, M.; Saito, N.; Akagawa, K.; Takazawa, A.; Ito, M.; Wada, S.; Takami, H.; Iye, M.

We report on the current status of developing the new laser guide star (LGS) system for the Subaru adaptive optics (AO) system. We have three major subsystems: the laser unit, the relay optical fiber and the laser launching telescope. A 4W-class all-solid-state 589nm laser has been developed as a light source for sodium laser guide star. We use two mode-locked Nd:YAG lasers operated at the wavelength of 1064nm and 1319nm to generate sum-frequency conversion into 589nm. The side-LD pumped configuration is used for the mode-locked Nd:YAG lasers. We have carefully considered the thermal lens effect in the cavity to achieve a high beam quality with TEM00; M2 = 1.06. The mode-locked frequency is selected at 143 MHz. We obtained the output powers of 16.5 W and 5.0 W at 1064nm and 1319 nm. Sum frequency generated by mixing two synchronized Nd:YAG mode-locked pulsed beams is precisely tuned to the sodium D2 line by thermal control of the etalon in the 1064nm Nd:YAG laser by observing the maximum fluorescence intensity of heated sodium vapor cell. The maximum output power at 589.159 nm reaches to 4.6 W using a PPMgOSLT crystal as a nonlinear optical crystal. And the output power can be maintained within a stability of +/- 1.2% for more than 3 days without optical damage. We developed a single-mode photonic crystal fiber (PCF) to relay the laser beam from laser clean room, in which the laser unit is located on the Nasmyth platform, to the laser launching telescope mounted behind the secondary mirror of Subaru Telescope. The photonic crystal fiber has solid pure silica core with the mode field diameter of 14 micron, which is relatively larger than that of the conventional step-index type single mode fiber. The length of the PCF is 35m and transmission loss due to the pure silica is 10dB/km at 589nm, which means PCF transmits 92% of the laser beam. We have preliminary achieved 75% throughput in total. Small mode-locked pulse width in time allows us to transmit the high-power laser beam with no suffer from the non-linear scatter effect, i.e. stimulated Brillouin scatter, in the PCF. The laser launching telescope (LLT) has an output clear aperture as 50 cm. It is classical Cassegrain type optical configuration with tertiary mirror to insert the laser beam from the side. The wavefront error is designed to be 60 to 70nm. The LLT is a copy product what European Southern Observatory has been designed for the laser guide star system at Very Large Telescope. We succeeded to launch the laser beam to the sky on October 12, 2006. After several tests on the sky, we succeeded to get an image of the laser guide star with the size of more than 10 arc second. The larger size of the laser guide star is caused by the large optical aberration on the primary mirror of LLT due to the heat stress generated at the trigonal support points. We are making a plan to repair this problem during June and the second laser launching test will start around this summer.

Astrometry of the omega Centauri Hubble Space Telescope Calibration Field

NASA Technical Reports Server (NTRS)

Mighell, Kenneth J.

2000-01-01

Astrometry, on the International Celestial Reference Frame (epoch J2000.0), is presented for the Walker (1994, PASP, 106, 828) stars in the omega Centauri (=NGC 5139=C 1323-1472) Hubble Space Telescope Wide Field/Planetary Camera (WF/PC) calibration field of Harris et al. (1993, AJ, 105, 1196). Harris et al. stars were first identified on a WFPC2 observation of the omega Cen HST calibration field. Relative astrometry of the Walker stars in this field was then obtained using Walker's CCD positions and astrometry derived using the STSDAS METRIC task on the positions of the Harris et al. stars on the WFPC2 observation. Finally, the relative astrometry, which was based on the HST Guide Star Catalog, is placed on the International Celestial Reference Frame with astrometry from the USNO-A2.0 catalog. An ASCII text version of the astrometric data of the Walker stars in the omega Cen HST calibration field is available electronically in the online version of the article.

Chico High School Students' Astrometric Observations of the Visual Double Star STF 1657

NASA Astrophysics Data System (ADS)

Ahiligwo, Jonelle; Bergamini, Clara; Berglund, Kallan; Bhardwaj, Mohit; Chelson, Spud; Costa, Amanda; Epis, Ashley; Grant, Azure; Osteen, Courtney; Reiner, Skyla; Rose, Adam; Schmidt, Emily; Sears, Forest; Sullivan-Hames, Maddie; Johnson, Jolyon

2012-01-01

In the spring of 2011, Chico Senior High School students participated in an astronomy seminar at the Gateway Science Museum, University of California, Chico. The observers used a Celestron NexStar 6 SE telescope and a Celestron MicroGuide eyepiece to determine the separation and position angle of the visual double star STF 1657. Observations were made in approximately one hour on the evening of May 1, 2011. The observers determined that the separation of STF 1657 was 22.1" and the position angle was 273.4&°. Seminar members then used the spectral type, parallax, and proper motion vectors of the two stars to determine if they are a line-of-sight optical pair or physically bound by gravity. Due to large errors in the parallax and the proper motion vector for the secondary star, the results were inconclusive. Through this experience, the students learned the skills needed to observe, analyze, and report on double stars.

Understanding and acceptability by Hispanic consumers of four front-of-pack food labels.

PubMed

De la Cruz-Góngora, Vanessa; Torres, Pilar; Contreras-Manzano, Alejandra; Jáuregui de la Mota, Alejandra; Mundo-Rosas, Verónica; Villalpando, Salvador; Rodríguez-Oliveros, Guadalupe

2017-03-07

Front-of-pack food labels (FOPL) can help consumers make healthy and informed food choices. FOPL are used in the food market but evaluations of their understanding and acceptability are scanty. This study aimed to explore the subjective understanding and acceptability of four FOPL among Hispanic consumers. A qualitative study was conducted in six States of Mexico, in 18 urban elementary schools. A purposive sample of 135 parents of fifth-grade children was selected. Four FOPL were assessed: Logos, Rating Stars, Guideline Daily Allowances (GDA's), and Multiple Traffic Lights (MTL). Trained interviewers performed 18 focus groups with the participants, using an interview guide. Participants were asked about their subjective understanding and acceptability of the FOPL, displaying 16 generic breakfast cereal boxes designed for this study (four for each FOPL), varying in their nutritional value. Afterwards, participants were asked to choose among the four cereal boxes the one to best communicate the product healthiness and their reasons for choice, proposals for improving the FOPL, and desirable characteristics for new FOPL. Finally, a socio-demographic questionnaire was applied. Thematic analysis of the transcriptions of the focus groups was performed, using Altlas.tiV5 software. Logos were perceived as easy to understand, highly acceptable, and useful for decision-making; institutional endorsement of Logos was related to greater confidence in the label. The GDA's were hard to understand considering the nutritional knowledge and time needed for interpretation. The Rating Stars were related to the quality in businesses rather than foods. The MTL were viewed as indicating the high/low content of specific nutrients, but the meaning of the amber color was not fully understood. Participants highlighted the need for a simple FOPL that allows easily identification of healthy products while considering food purchasing time limitations and interpretation of food portions. Logos with an institutional endorsement was the best understood and accepted FOPL, and the GDA's and Rating Stars were the least. Our findings provide valuable insights about Hispanic consumers´ perceptions regarding FOPL and to guide public health policy. Further studies are needed in populations with chronic diseases and diverse social contexts.

Atypical Mg-poor Milky Way Field Stars with Globular Cluster Second-generation-like Chemical Patterns

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fernández-Trincado, J. G.; Geisler, D.; Tang, B.

We report the peculiar chemical abundance patterns of 11 atypical Milky Way (MW) field red giant stars observed by the Apache Point Observatory Galactic Evolution Experiment (APOGEE). These atypical giants exhibit strong Al and N enhancements accompanied by C and Mg depletions, strikingly similar to those observed in the so-called second-generation (SG) stars of globular clusters (GCs). Remarkably, we find low Mg abundances ([Mg/Fe] < 0.0) together with strong Al and N overabundances in the majority (5/7) of the metal-rich ([Fe/H] ≳ −1.0) sample stars, which is at odds with actual observations of SG stars in Galactic GCs of similarmore » metallicities. This chemical pattern is unique and unprecedented among MW stars, posing urgent questions about its origin. These atypical stars could be former SG stars of dissolved GCs formed with intrinsically lower abundances of Mg and enriched Al (subsequently self-polluted by massive AGB stars) or the result of exotic binary systems. We speculate that the stars Mg-deficiency as well as the orbital properties suggest that they could have an extragalactic origin. This discovery should guide future dedicated spectroscopic searches of atypical stellar chemical patterns in our Galaxy, a fundamental step forward to understanding the Galactic formation and evolution.« less

Atypical Mg-poor Milky Way Field Stars with Globular Cluster Second-generation-like Chemical Patterns

NASA Astrophysics Data System (ADS)

Fernández-Trincado, J. G.; Zamora, O.; García-Hernández, D. A.; Souto, Diogo; Dell'Agli, F.; Schiavon, R. P.; Geisler, D.; Tang, B.; Villanova, S.; Hasselquist, Sten; Mennickent, R. E.; Cunha, Katia; Shetrone, M.; Allende Prieto, Carlos; Vieira, K.; Zasowski, G.; Sobeck, J.; Hayes, C. R.; Majewski, S. R.; Placco, V. M.; Beers, T. C.; Schleicher, D. R. G.; Robin, A. C.; Mészáros, Sz.; Masseron, T.; García Pérez, Ana E.; Anders, F.; Meza, A.; Alves-Brito, A.; Carrera, R.; Minniti, D.; Lane, R. R.; Fernández-Alvar, E.; Moreno, E.; Pichardo, B.; Pérez-Villegas, A.; Schultheis, M.; Roman-Lopes, A.; Fuentes, C. E.; Nitschelm, C.; Harding, P.; Bizyaev, D.; Pan, K.; Oravetz, D.; Simmons, A.; Ivans, Inese I.; Blanco-Cuaresma, S.; Hernández, J.; Alonso-García, J.; Valenzuela, O.; Chanamé, J.

2017-09-01

We report the peculiar chemical abundance patterns of 11 atypical Milky Way (MW) field red giant stars observed by the Apache Point Observatory Galactic Evolution Experiment (APOGEE). These atypical giants exhibit strong Al and N enhancements accompanied by C and Mg depletions, strikingly similar to those observed in the so-called second-generation (SG) stars of globular clusters (GCs). Remarkably, we find low Mg abundances ([Mg/Fe] < 0.0) together with strong Al and N overabundances in the majority (5/7) of the metal-rich ([Fe/H] ≳ -1.0) sample stars, which is at odds with actual observations of SG stars in Galactic GCs of similar metallicities. This chemical pattern is unique and unprecedented among MW stars, posing urgent questions about its origin. These atypical stars could be former SG stars of dissolved GCs formed with intrinsically lower abundances of Mg and enriched Al (subsequently self-polluted by massive AGB stars) or the result of exotic binary systems. We speculate that the stars Mg-deficiency as well as the orbital properties suggest that they could have an extragalactic origin. This discovery should guide future dedicated spectroscopic searches of atypical stellar chemical patterns in our Galaxy, a fundamental step forward to understanding the Galactic formation and evolution.

Assessment of visiting activities for young children using the UNAWE Evaluation Guide

NASA Astrophysics Data System (ADS)

Tomita, Akihiko

2015-08-01

When the target is young children and the activity type is play, the assessment of the activity is not easy. The table of domains of active learning shown in the EU Universe Awareness Programme Evaluation Guide is useful for the assessment; the Guide shows the four domains; motivation, scientific skills, universe knowledge, and intercultural attitudes, and many items of objectives in each domains. The Guide can be a basic format and the items can be modified so as to fit each activity. Taking my activity as an example, I will present an assessment using the Guide. The activity I will present is "Uchu no O-hanashi," a visiting activity which includeds slide show, story telling, and enjoying pictures on large sheets for children at nursery, kindergarten, preschool and other sites. In order to obtain the data, I have recorded the voice of children. The analysis method is a kind of qualitative one. I picked up "motivation" and "scientific skills" words from the record when they muttered about and asked each other what they felt, what they found, and what they got excited about. Among the items in the "scientific skills domain," looking at carefully, asking, exchanging opinions, interpreting or trying to interpret, and trying were frequently appeared. Other skills such as devising and confirming were not frequently appeared but they would sometimes appear later at home or at school after the activity. I also picked up the words of children obtaining scientific way of view and attitude through the activity. One example is "It seems that stars float in the sky and do not move. Do they really set like the Sun, our nearest star? I never saw stars set!" A boy was trying to make a new framework for his understanding. This kind of thinking will enrich his or her future "universe knowledge" and "intercultural attitudes."

The Large Binocular Telescope's ARGOS ground-layer AO system

NASA Astrophysics Data System (ADS)

Hart, M.; Rabien, S.; Busoni, L.; Barl, L.; Bechmann, U.; Bonaglia, M.; Boose, Y.; Borelli, J.; Bluemchen, T.; Carbonaro, L.; Connot, C.; Deysenroth, M.; Davies, R.; Durney, O.; Elberich, M.; Ertl, T.; Esposito, S.; Gaessler, W.; Gasho, V.; Gemperlein, H.; Hubbard, P.; Kanneganti, S.; Kulas, M.; Newman, K.; Noenickx, J.; Orban de Xivry, G.; Qirrenback, A.; Rademacher, M.; Schwab, C.; Storm, J.; Vaitheeswaran, V.; Weigelt, G.; Ziegleder, J.

2011-09-01

ARGOS, the laser-guided adaptive optics system for the Large Binocular Telescope (LBT), is now under construction at the telescope. By correcting atmospheric turbulence close to the telescope, the system is designed to deliver high resolution near infrared images over a field of 4 arc minute diameter. ARGOS is motivated by a successful prototype multi-laser guide star system on the 6.5 m MMT telescope, results from which are presented in this paper. At the LBT, each side of the twin 8.4 m aperture is being equipped with three Rayleigh laser guide stars derived from six 18 W pulsed green lasers and projected into two triangular constellations matching the size of the corrected field. The returning light is to be detected by wavefront sensors that are range gated within the seeinglimited depth of focus of the telescope. Wavefront correction will be introduced by the telescope’s deformable secondary mirrors driven on the basis of the average wavefront errors computed from the respective guide star constellation. Measured atmospheric turbulence profiles from the site lead us to expect that by compensating the ground-layer turbulence, ARGOS will deliver median image quality of about 0.2 arc sec in the near infrared bands. This will be exploited by a pair of multi-object near-IR spectrographs, LUCI1 and LUCI2, each with 4 arc minute field already operating on the telescope. In future, ARGOS will also feed two interferometric imaging instruments, the LBT Interferometer operating in the thermal infrared, and LINC-NIRVANA, operating at visible and near infrared wavelengths. Together, these instruments will offer very broad spectral coverage at the diffraction limit of the LBT’s combined aperture, 23 m in size.

KSC-2009-1652

NASA Image and Video Library

2009-02-16

CAPE CANAVERAL, Fla. – At the Hazardous Processing Facility at Astrotech in Titusville, Fla., workers guide the suspended Kepler spacecraft onto a Delta II third stage. Kepler is designed to survey more than 100,000 stars in our galaxy to determine the number of sun-like stars that have Earth-size and larger planets, including those that lie in a star's "habitable zone," a region where liquid water, and perhaps life, could exist. If these Earth-size worlds do exist around stars like our sun, Kepler is expected to be the first to find them and the first to measure how common they are. The liftoff of Kepler aboard a Delta II rocket is currently targeted for 10:48 p.m. EST March 5 from Space Launch Complex 17 on Cape Canaveral Air Force Station. Photo credit: NASA/Troy Cryder

Native Skywatchers and the Makoc&dotbelow;e Wic&dotbelow;aŋḣpi Wowapi—D(L)akota Star Map—Building Community Around Native Star Knowledge

NASA Astrophysics Data System (ADS)

Lee, A. S.; Rock, J.

2014-07-01

In D(L)akota the Big Dipper is known as To/ToŋWiŋ—Blue/Birth Woman. She lives at the center of the scoop in the Big Dipper and is the door keeper between the star world and the Earth. The same group of seven bright stars is also known as Wịakiyuhapi, the Stretcher, and Waṡihdapi/Waṡiglapi, the Mourners. This is the beginning of the journey back into the spirit world for those leaving the Earth. Embedded in the native constellations are teachings that help guide and inspire native peoples. This workshop will present the D(L)akota Star Map and constellations of the current night sky. The Native Skywatchers research and programming seeks out elders, culture teachers, and community members to discuss the Ojibwe and D(L)akota star knowledge. Together we have created Makoc&dotbelow;e Wic&dotbelow;aŋḣpi Wowapi—D(L)akota Star Map. This map and related curriculum was published and disseminated to regional educators at our Native Skywatchers Middle School Teacher workshops in June 2012 and 2013. We are building community around the native star knowledge.

ASTRO-2 Spacelab Instrument Pointing System mission performance

NASA Technical Reports Server (NTRS)

Wessling, Francis C., III; Singh, S. P.

1995-01-01

This paper reports the performance of the Instrument Pointing System (IPS) that flew on the National Aeronautics and Space Administration (NASA) ASTRO-2 Spacelab mission aboard the Space Shuttle Endeavour in March 1995. The IPS provides a stabilizing platform for the ASTRO-2 instrument payload complement that consists of three main experiments (telescopes). The telescopes observe stellar targets in the universe within the ultraviolet portion of the electromagnetic spectrum that must be observed from beyond the earth's atmospheric filtering effects. The three main experiments for observation are the Hopkins Ultraviolet Telescope (HUT), the Ultraviolet Imaging Telescope (UIT), and the Wisconsin Ultraviolet Photo-Polarimetry Experiment (WUPPE). The HUT uses spectroscopy to obtain the structure and chemical makeup of ultraviolet targets. UIT is responsible for wide field photographing to capture the hidden view of the ultraviolet universe. The WUPPE gathers data on the polarization of the ultraviolet electromagnetic energy coming from the astronomical targets. The capability of IPS enables the experiments to 'see' faint celestial objects. A brief explanation of the IPS is given followed by a review of engineering efforts to improve IPS performance over the ASTRO-1 mission. The main focus of improvements was on enhancing the star acquisition capability through improved guide star selection, lab simulations, computer upgrades, data display systems improvements, and software modifications. A star simulator was developed in the lab to enable IPS to be simulated on the ground pre-mission with flight hardware and software in the loop. The paper concludes with results from the ASTRO-2 mission. The number of targets acquired and the IPS pointing accuracy/stability is reported along with recommendations for the future use of the Instrument Pointing System.

A search for ejecta nebulae around Wolf-Rayet stars using the SHS Hα survey

NASA Astrophysics Data System (ADS)

Stock, D. J.; Barlow, M. J.

2010-12-01

Recent large-scale Galactic plane Hα surveys allow a re-examination of the environs of Wolf-Rayet (WR) stars for the presence of a circumstellar nebula. Using the morphologies of WR nebulae known to be composed of stellar ejecta as a guide, we constructed ejecta nebula criteria similar to those of Chu and searched for likely WR ejecta nebulae in the Southern Hα Survey (SHS). A new WR ejecta nebula around WR 8 is found and its morphology is discussed. The fraction of WR stars with ejecta-type nebulae is roughly consistent between the Milky Way (MW) and Large Magellanic Cloud (LMC) at around 5-6 per cent, with the MW sample dominated by nitrogen-rich WR central stars (WN type) and the LMC stars having a higher proportion of carbon-rich WR central stars (WC type). We compare our results with those of previous surveys, including those of Marston and Miller & Chu, and find broad consistency. We investigate several trends in the sample: most of the clear examples of ejecta nebulae have WNh central stars, and very few ejecta nebulae have binary central stars. Finally, the possibly unique evolutionary status of the nebula around the binary star WR 71 is explored.

Comparison Study II: Double Star Measurements Made Using an Equatorial Mounted Refractor and an Alt-Az Mounted Reflector

NASA Astrophysics Data System (ADS)

Frey, Thomas G.; Coombs, Lee C.

2012-07-01

Eight double stars with separations between 13 and 48 arc seconds were studied. Their separations and position angles were measured using an equatorial mounted refractor and and alt-az mounted reflector. A 2x Barlow lens was used along with a Celestron Micro Guide eyepiece to magnify the separation. Comparison of the possible effect of magnitude difference on the separation and position angle measurements was investigated.

User's guide for vectorized code EQUIL for calculating equilibrium chemistry on Control Data STAR-100 computer

NASA Technical Reports Server (NTRS)

Kumar, A.; Graves, R. A., Jr.; Weilmuenster, K. J.

1980-01-01

A vectorized code, EQUIL, was developed for calculating the equilibrium chemistry of a reacting gas mixture on the Control Data STAR-100 computer. The code provides species mole fractions, mass fractions, and thermodynamic and transport properties of the mixture for given temperature, pressure, and elemental mass fractions. The code is set up for the electrons H, He, C, O, N system of elements. In all, 24 chemical species are included.

Accretion-induced spin-wandering effects on the neutron star in Scorpius X-1: Implications for continuous gravitational wave searches

NASA Astrophysics Data System (ADS)

Mukherjee, Arunava; Messenger, Chris; Riles, Keith

2018-02-01

The LIGO's discovery of binary black hole mergers has opened up a new era of transient gravitational wave astronomy. The potential detection of gravitational radiation from another class of astronomical objects, rapidly spinning nonaxisymmetric neutron stars, would constitute a new area of gravitational wave astronomy. Scorpius X-1 (Sco X-1) is one of the most promising sources of continuous gravitational radiation to be detected with present-generation ground-based gravitational wave detectors, such as Advanced LIGO and Advanced Virgo. As the sensitivity of these detectors improve in the coming years, so will power of the search algorithms being used to find gravitational wave signals. Those searches will still require integration over nearly year long observational spans to detect the incredibly weak signals from rotating neutron stars. For low mass X-ray binaries such as Sco X-1 this difficult task is compounded by neutron star "spin wandering" caused by stochastic accretion fluctuations. In this paper, we analyze X-ray data from the R X T E satellite to infer the fluctuating torque on the neutron star in Sco X-1. We then perform a large-scale simulation to quantify the statistical properties of spin-wandering effects on the gravitational wave signal frequency and phase evolution. We find that there are a broad range of expected maximum levels of frequency wandering corresponding to maximum drifts of between 0.3 - 50 μ Hz /sec over a year at 99% confidence. These results can be cast in terms of the maximum allowed length of a coherent signal model neglecting spin-wandering effects as ranging between 5-80 days. This study is designed to guide the development and evaluation of Sco X-1 search algorithms.

Conceptual design for a user-friendly adaptive optics system at Lick Observatory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bissinger, H.D.; Olivier, S.; Max, C.

1996-03-08

In this paper, we present a conceptual design for a general-purpose adaptive optics system, usable with all Cassegrain facility instruments on the 3 meter Shane telescope at the University of California`s Lick Observatory located on Mt. Hamilton near San Jose, California. The overall design goal for this system is to take the sodium-layer laser guide star adaptive optics technology out of the demonstration stage and to build a user-friendly astronomical tool. The emphasis will be on ease of calibration, improved stability and operational simplicity in order to allow the system to be run routinely by observatory staff. A prototype adaptivemore » optics system and a 20 watt sodium-layer laser guide star system have already been built at Lawrence Livermore National Laboratory for use at Lick Observatory. The design presented in this paper is for a next- generation adaptive optics system that extends the capabilities of the prototype system into the visible with more degrees of freedom. When coupled with a laser guide star system that is upgraded to a power matching the new adaptive optics system, the combined system will produce diffraction-limited images for near-IR cameras. Atmospheric correction at wavelengths of 0.6-1 mm will significantly increase the throughput of the most heavily used facility instrument at Lick, the Kast Spectrograph, and will allow it to operate with smaller slit widths and deeper limiting magnitudes. 8 refs., 2 figs.« less

Mesospheric sodium structure variability on horizontal scales relevant to laser guide star asterisms

NASA Astrophysics Data System (ADS)

Pfrommer, Thomas; Hickson, Paul

2012-07-01

Adaptive optics (AO) systems of modern telescopes use laser guide stars, produced by resonant excitation of sodium atoms in the mesosphere at around 92 km. Wavefront sensor subapertures, if sufficiently far away from the primary mirror center, resolve the internal structure of the sodium layer. The variability of this structure is caused by the influence of gravity waves and wind shear turbulence. The relevance of such dynamics to AO has been investigated over the past four years. A high-resolution lidar system, employed at the 6-m liquid mirror telescope, which is located near Vancouver, Canada, has been used to study mesospheric dynamics, such as the temporal behavior of the mean altitude. The main results from this study have been published elsewhere and will be summarized here. Along with the temporal variability, the mean altitude on horizontal scales of order IOs of meters has been studied by introducing a tip/tilt stage in the experimental setup. This enables us to swap the laser pulse within a 1 arcmin field of view. The horizontal mean altitude structure function has been measured on 10 observing nights between July and August 2011. Results reveal severe structural differences and a strong horizontal anisotropy. Individual laser beacons in a laser guide star asterism will therefore have at the same time significantly different focus heights. By propagating this 2d structure function to the entrance pupil of a 39 m telescope, we derive a differential focus wavefront error map.

A fast and efficient python library for interfacing with the Biological Magnetic Resonance Data Bank.

PubMed

Smelter, Andrey; Astra, Morgan; Moseley, Hunter N B

2017-03-17

The Biological Magnetic Resonance Data Bank (BMRB) is a public repository of Nuclear Magnetic Resonance (NMR) spectroscopic data of biological macromolecules. It is an important resource for many researchers using NMR to study structural, biophysical, and biochemical properties of biological macromolecules. It is primarily maintained and accessed in a flat file ASCII format known as NMR-STAR. While the format is human readable, the size of most BMRB entries makes computer readability and explicit representation a practical requirement for almost any rigorous systematic analysis. To aid in the use of this public resource, we have developed a package called nmrstarlib in the popular open-source programming language Python. The nmrstarlib's implementation is very efficient, both in design and execution. The library has facilities for reading and writing both NMR-STAR version 2.1 and 3.1 formatted files, parsing them into usable Python dictionary- and list-based data structures, making access and manipulation of the experimental data very natural within Python programs (i.e. "saveframe" and "loop" records represented as individual Python dictionary data structures). Another major advantage of this design is that data stored in original NMR-STAR can be easily converted into its equivalent JavaScript Object Notation (JSON) format, a lightweight data interchange format, facilitating data access and manipulation using Python and any other programming language that implements a JSON parser/generator (i.e., all popular programming languages). We have also developed tools to visualize assigned chemical shift values and to convert between NMR-STAR and JSONized NMR-STAR formatted files. Full API Reference Documentation, User Guide and Tutorial with code examples are also available. We have tested this new library on all current BMRB entries: 100% of all entries are parsed without any errors for both NMR-STAR version 2.1 and version 3.1 formatted files. We also compared our software to three currently available Python libraries for parsing NMR-STAR formatted files: PyStarLib, NMRPyStar, and PyNMRSTAR. The nmrstarlib package is a simple, fast, and efficient library for accessing data from the BMRB. The library provides an intuitive dictionary-based interface with which Python programs can read, edit, and write NMR-STAR formatted files and their equivalent JSONized NMR-STAR files. The nmrstarlib package can be used as a library for accessing and manipulating data stored in NMR-STAR files and as a command-line tool to convert from NMR-STAR file format into its equivalent JSON file format and vice versa, and to visualize chemical shift values. Furthermore, the nmrstarlib implementation provides a guide for effectively JSONizing other older scientific formats, improving the FAIRness of data in these formats.

The search for extra-solar planetary systems.

PubMed

Paresce, F

1992-01-01

I review the observational evidence for planetary systems around nearby stars and, using our own solar system as a guide, assess the stringent requirements that new searches need to meet in order to unambiguously establish the presence of another planetary system. Basically, these requirements are: 1 milliarcsecond or better positional accuracy for astrometric techniques, 9 orders of magnitude or better star to planet luminosity ratio discrimination at 0.5 to 1" separation in the optical for direct imaging techniques, 10 meters sec-1 or better radial velocity accuracy for reflex motion techniques and +/-1% or better brightness fluctuation accuracy for planet/star occultation measurements. The astrometric accuracy is in reach of HST, direct imaging will require much larger telescopes and/or a 50 times smoother mirror than HST while the reflex motion and occultation techniques best performed on the ground are just becoming viable and promise exciting new discoveries. On the other band, new indirect evidence on the existence of other planetary systems also comes from the observation of large dusty disks around nearby main sequence stars not too dissimilar from our sun. In one particular case, that of Beta Pictoris, a flattened disk seen nearly edge-on has been imaged in the optical and near IR down to almost 70 AU of the star. It probably represents a young planetary system in its clearing out phase as planetesimals collide, erode and are swept out of the inner system by radiation pressure. The hypothesized Kuiper belt around our solar system may be the analogous structure in a later evolutionary stage. Features of this type have been detected in the far IR and sub-millimeter wavelength regions around 50-100 nearby main sequence and pre-main sequence stars. I discuss a battery of new accurate observations planned in the near future of these objects some of which may actually harbour planets or planetesimals that will certainly dramatically improve our knowledge of planetary system formation processes and our peculiar position in this scheme.

The Stellar Cusp in the Galactic Center: Three-Dimensional Orbits of Stars

NASA Astrophysics Data System (ADS)

Chappell, Samantha; Ghez, Andrea M.; Boehle, Anna; Yelda, Sylvana; Sitarski, Breann; Witzel, Gunther; Do, Tuan; Lu, Jessica R.; Morris, Mark; Becklin, Eric E.

2015-01-01

We present new findings from our long term study of the nuclear star cluster around the Galaxy's central supermassive blackhole (SMBH). Measurements where made using speckle and laser guided adaptive optics imaging and integral field spectroscopy on the Keck telescopes. We report 13 new measurable accelerating sources around the SMBH, down to ~17 mag in K band, only 4 of which are known to be young stars, the rest are either known to be old stars or have yet to be spectral typed. Thus we more than double the number of measured accelerations for the known old stars and unknown spectral type population (increasing the number from 6 to 15). Previous observations suggest a flat density profile of late-type stars, contrary to the theorized Bahcall-Wolf cusp (Bahcall & Wolf 1976, 1977; Buchholz et al. 2009; Do et al. 2009; Bartko et al. 2010). With three-dimensional orbits of significantly accelerating sources, we will be able to better characterize the stellar cusp in the Galactic center, including the slope of the stellar density profile.

High Resolution Active Optics Observations from the Kepler Follow-up Observation Program

NASA Astrophysics Data System (ADS)

Gautier, Thomas N.; Ciardi, D. R.; Marcy, G. W.; Hirsch, L.

2014-01-01

The ground based follow-up observation program for candidate exoplanets discovered with the Kepler observatory has supported a major effort for high resolution imaging of candidate host stars using adaptive optics wave-front correction (AO), speckle imaging and lucky imaging. These images allow examination of the sky as close as a few tenths of an arcsecond from the host stars to detect background objects that might be the source of the Kepler transit signal instead of the host star. This poster reports on the imaging done with AO cameras on the Keck, Palomar 5m and Shane 3m (Lick Observatory) which have been used to obtain high resolution images of over 500 Kepler Object of Interest (KOI) exoplanet candidate host stars. All observations were made at near infrared wavelengths in the J, H and K bands, mostly using the host target star as the AO guide star. Details of the sensitivity to background objects actually attained by these observations and the number of background objects discovered are presented. Implications to the false positive rate of the Kepler candidates are discussed.

Fixed-head star tracker attitude updates on the Hubble Space Telescope

NASA Technical Reports Server (NTRS)

Nadelman, Matthew S.; Karl, Jeffrey B.; Hallock, Lou

1994-01-01

The Hubble Space Telescope (HST) was launched in April 1990 to begin observing celestial space to the edge of the universe. National Aeronautics and Space Administration (NASA) standard fixed-head star trackers (FHST's) are used operationally onboard the HST to regularly adjust ('update') the spacecraft attitude before the acquisition of guide stars for science observations. During the first 3 months of the mission, the FHST's updated the spacecraft attitude successfully only 85 percent of the time. During the other periods, the trackers were unable to find the selected stars -- either they failed to find any star, or worse, they selected incorrect stars and produced erroneous attitude updates. In July 1990, the HST project office at Goddard Space Flight Center (GSFC) requested that Computer Sciences Corporation (CSC) form an investigative 'tiger' team to examine these FHST update failures. This paper discusses the work of the FHST tiger team, describes the investigations that led the team to identify the sources of the errors, and defines the solutions that were subsequently developed, which ultimately increased the success rate of FHST updates to approximately 98 percent.

Terrestrial Planet Finder Coronagraph 2005: Overview of Technology Development and System Design Studies

NASA Technical Reports Server (NTRS)

Ford, Virginia G.

2005-01-01

Technology research, design trades, and modeling and analysis guide the definition of a Terrestrial Planet Finder Coronagraph Mission that will search for and characterize earth-like planets around near-by stars. Operating in visible wavebands, this mission will use coronagraphy techniques to suppress starlight to enable capturing and imaging the reflected light from a planet orbiting in the habitable zone of its parent star. The light will be spectrally characterized to determine the presence of life-indicating chemistry in the planet atmosphere.

The Black Hole Masses and Star Formation Rates of z>1 Dust Obscured Galaxies: Results from Keck OSIRIS Integral Field Spectroscopy

NASA Astrophysics Data System (ADS)

Melbourne, J.; Peng, Chien Y.; Soifer, B. T.; Urrutia, Tanya; Desai, Vandana; Armus, L.; Bussmann, R. S.; Dey, Arjun; Matthews, K.

2011-04-01

We have obtained high spatial resolution Keck OSIRIS integral field spectroscopy of four z ~ 1.5 ultra-luminous infrared galaxies that exhibit broad Hα emission lines indicative of strong active galactic nucleus (AGN) activity. The observations were made with the Keck laser guide star adaptive optics system giving a spatial resolution of 0farcs1 or <1 kpc at these redshifts. These high spatial resolution observations help to spatially separate the extended narrow-line regions—possibly powered by star formation—from the nuclear regions, which may be powered by both star formation and AGN activity. There is no evidence for extended, rotating gas disks in these four galaxies. Assuming dust correction factors as high as A(Hα) = 4.8 mag, the observations suggest lower limits on the black hole masses of (1-9) × 108 M sun and star formation rates <100 M sun yr-1. The black hole masses and star formation rates of the sample galaxies appear low in comparison to other high-z galaxies with similar host luminosities. We explore possible explanations for these observations, including host galaxy fading, black hole growth, and the shut down of star formation.

Study the performance of star sensor influenced by space radiation damage of image sensor

NASA Astrophysics Data System (ADS)

Feng, Jie; Li, Yudong; Wen, Lin; Guo, Qi; Zhang, Xingyao

2018-03-01

Star sensor is an essential component of spacecraft attitude control system. Spatial radiation can cause star sensor performance degradation, abnormal work, attitude measurement accuracy and reliability reduction. Many studies have already been dedicated to the radiation effect on Charge-Coupled Device(CCD) image sensor, but fewer studies focus on the radiation effect of star sensor. The innovation of this paper is to study the radiation effects from the device level to the system level. The influence of the degradation of CCD image sensor radiation sensitive parameters on the performance parameters of star sensor is studied in this paper. The correlation among the radiation effect of proton, the non-uniformity noise of CCD image sensor and the performance parameter of star sensor is analyzed. This paper establishes a foundation for the study of error prediction and correction technology of star sensor on-orbit attitude measurement, and provides some theoretical basis for the design of high performance star sensor.

Fine pointing control for a Next-Generation Space Telescope

NASA Astrophysics Data System (ADS)

Mosier, Gary E.; Femiano, Michael; Ha, Kong; Bely, Pierre Y.; Burg, Richard; Redding, David C.; Kissil, Andrew; Rakoczy, John; Craig, Larry

1998-08-01

The Next Generation Space Telescope will provide at least ten times the collecting area of the Hubble Space Telescope in a package that fits into the shroud of an expendable launch vehicle. The resulting large, flexible structure provides a challenge to the design of a pointing control system for which the requirements are at the milli-arcsecond level. This paper describes a design concept in which pointing stability is achieved by means of a nested-loop design involving an inertial attitude control system (ACS) and a fast steering mirror (FSM). A key to the integrated control design is that the ACS controllers has a bandwidth well below known structural modes and the FSM uses a rotationally balanced mechanism which should not interact with the flexible modes that are within its control bandwidth. The ACS controller provides stable pointing of the spacecraft bus with star trackers and gyros. This low bandwidth loop uses nearly co-located sensors and actuators to slew and acquire faint guide stars in the NIR camera. This controller provides a payload reference stable to the arcsecond level. Low-frequency pointing errors due to sensor noise and dynamic disturbances are suppressed by a 2-axis gimbaled FSM locate din the instrument module. The FSM servo bandwidth of 6 Hz is intended to keep the guide star position stable in the NIR focal plane to the required milli-arcsecond level. The mirror is kept centered in its range of travel by a low-bandwidth loop closed around the ACS. This paper presents the result of parametric trade studies designed to assess the performance of this control design in the presence of modeled reaction wheel disturbances, assumed to be the principle source of vibration for the NGST, and variations in structural dynamics. Additionally, requirements for reaction wheel disturbance levels and potential vibration isolation subsystems were developed.

MAPPING THE CLUMPY STRUCTURES WITHIN SUBMILLIMETER GALAXIES USING LASER-GUIDE STAR ADAPTIVE OPTICS SPECTROSCOPY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Menendez-Delmestre, Karin; Goncalves, Thiago S.; Blain, Andrew W.

2013-04-20

We present the first integral-field spectroscopic observations of high-redshift submillimeter-selected galaxies (SMGs) using Laser-Guide Star Adaptive Optics. We target H{alpha} emission of three SMGs at redshifts z {approx} 1.4-2.4 with the OH-Suppressing Infrared Imaging Spectrograph on Keck. The spatially resolved spectroscopy of these galaxies reveals unresolved broad-H{alpha} line regions (FWHM >1000 km s{sup -1}) likely associated with an active galactic nucleus (AGN) and regions of diffuse star formation traced by narrow-line H{alpha} emission (FWHM {approx}< 500 km s{sup -1}) dominated by multiple H{alpha}-bright stellar clumps, each contributing 1%-30% of the total clump-integrated H{alpha} emission. We find that these SMGs hostmore » high star formation rate surface densities, similar to local extreme sources, such as circumnuclear starbursts and luminous infrared galaxies. However, in contrast to these local environments, SMGs appear to be undergoing such intense activity on significantly larger spatial scales as revealed by extended H{alpha} emission over 4-16 kpc. H{alpha} kinematics show no evidence of ordered global motion as would be found in a disk, but rather large velocity offsets ({approx}few Multiplication-Sign 100 km s{sup -1}) between the distinct stellar clumps. Together with the asymmetric distribution of the stellar clumps around the AGN in these objects, it is unlikely that we are unveiling a clumpy disk structure as has been suggested in other high-redshift populations of star-forming galaxies. The SMG clumps in this sample may correspond to remnants of originally independent gas-rich systems that are in the process of merging, hence triggering the ultraluminous SMG phase.« less

From Cool to Hot F-stars: The Influence of Two Ionization Regions in the Acoustic Oscillations

NASA Astrophysics Data System (ADS)

Brito, Ana; Lopes, Ilídio

2018-02-01

The high-precision data available from the Kepler satellite allows us to study the complex outer convective envelopes of solar-type stars. We use a seismic diagnostic, specialized for investigating the outer layers of solar-type stars, to infer the impact of the ionization processes on the oscillation spectrum, for a sample of Kepler stars. These stars, of spectral type F, cover all of the observational seismic domain of the acoustic oscillation spectrum in solar-type stars. They also cover the range between a cool F-dwarf (∼6000 K) and a hotter F-star (∼6400 K). Our study reveals the existence of two relevant ionization regions. One of these regions, which is located closer to the surface of the star, is commonly associated with the second ionization of helium, although other chemical species also contribute to ionization. The second region, located deeper in the envelope, is linked with the ionization of heavy elements. Specifically, in this study, we analyze the elements carbon, nitrogen, oxygen, neon, and iron. Both regions can be related to the K electronic shell. We show that, while for cooler stars like the Sun, the influence of this second region on the oscillation frequencies is small; in hotter stars, its influence becomes comparable to the influence of the region of the second ionization of helium. This can guide us in the study of the outer layers of F-stars, specifically with the understanding of phenomena related to rotation and magnetic activity in these stars.

KAPAO first light: the design, construction and operation of a low-cost natural guide star adaptive optics system

NASA Astrophysics Data System (ADS)

Severson, Scott A.; Choi, Philip I.; Badham, Katherine E.; Bolger, Dalton; Contreras, Daniel S.; Gilbreth, Blaine N.; Guerrero, Christian; Littleton, Erik; Long, Joseph; McGonigle, Lorcan P.; Morrison, William A.; Ortega, Fernando; Rudy, Alex R.; Wong, Jonathan R.; Spjut, Erik; Baranec, Christoph; Riddle, Reed

2014-07-01

We present the instrument design and first light observations of KAPAO, a natural guide star adaptive optics (AO) system for the Pomona College Table Mountain Observatory (TMO) 1-meter telescope. The KAPAO system has dual science channels with visible and near-infrared cameras, a Shack-Hartmann wavefront sensor, and a commercially available 140-actuator MEMS deformable mirror. The pupil relays are two pairs of custom off-axis parabolas and the control system is based on a version of the Robo-AO control software. The AO system and telescope are remotely operable, and KAPAO is designed to share the Cassegrain focus with the existing TMO polarimeter. We discuss the extensive integration of undergraduate students in the program including the multiple senior theses/capstones and summer assistantships amongst our partner institutions. This material is based upon work supported by the National Science Foundation under Grant No. 0960343.

An adaptive optics package designed for astronomical use with a laser guide star tuned to an absorption line of atomic sodium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Salmon, J.T.; Avicola, K.; Brase, J.M.

1994-04-11

We present the design and implementation of a very compact adaptive optic system that senses the return light from a sodium guide-star and controls a deformable mirror and a pointing mirror to compensate atmospheric perturbations in the wavefront. The deformable mirror has 19 electrostrictive actuators and triangular subapertures. The wavefront sensor is a Hartmann sensor with lenslets on triangular centers. The high-bandwidth steering mirror assembly incorporates an analog controller that samples the tilt with an avalanche photodiode quad cell. An {line_integral}/25 imaging leg focuses the light into a science camera that can either obtain long-exposure images or speckle data. Inmore » laboratory tests overall Strehl ratios were improved by a factor of 3 when a mylar sheet was used as an aberrator. The crossover frequency at unity gain is 30 Hz.« less

A conceptual scheme for cophasing across gaps in segmented pupils with a laser guide star Fizeau interferometer

NASA Astrophysics Data System (ADS)

Tuthill, Peter

2016-08-01

Finding and maintaining an accurate cophasing solution for the large primary mirrors which comprise the coming generation of Extremely Large Telescopes has required a significant technological development effort that is still ongoing. Mirrors based on an assembly of a few large segments, such as the Giant Magellan Telescope (GMT - under construction) and the Large Binocular Telescope (LBT - operational) face a particular challenge: elements must be cophased across a gaps ranging from tens of centimeters to meters. Although it is widely believed that laser guide stars are not useful for this specific application, this paper advances a new concept that challenges this orthodoxy. By projecting a Fizeau interference pattern into the sky, and analyzing the form of the backscattered image, it is shown that at least in principle it is possible to cophase across arbitrary gaps.

Minimizing eddy currents induced in the ground plane of a large phased-array ultrasound applicator for echo-planar imaging-based MR thermometry.

PubMed

Lechner-Greite, Silke M; Hehn, Nicolas; Werner, Beat; Zadicario, Eyal; Tarasek, Matthew; Yeo, Desmond

2016-01-01

The study aims to investigate different ground plane segmentation designs of an ultrasound transducer to reduce gradient field induced eddy currents and the associated geometric distortion and temperature map errors in echo-planar imaging (EPI)-based MR thermometry in transcranial magnetic resonance (MR)-guided focused ultrasound (tcMRgFUS). Six different ground plane segmentations were considered and the efficacy of each in suppressing eddy currents was investigated in silico and in operando. For the latter case, the segmented ground planes were implemented in a transducer mockup model for validation. Robust spoiled gradient (SPGR) echo sequences and multi-shot EPI sequences were acquired. For each sequence and pattern, geometric distortions were quantified in the magnitude images and expressed in millimeters. Phase images were used for extracting the temperature maps on the basis of the temperature-dependent proton resonance frequency shift phenomenon. The means, standard deviations, and signal-to-noise ratios (SNRs) were extracted and contrasted with the geometric distortions of all patterns. The geometric distortion analysis and temperature map evaluations showed that more than one pattern could be considered the best-performing transducer. In the sagittal plane, the star (d) (3.46 ± 2.33 mm) and star-ring patterns (f) (2.72 ± 2.8 mm) showed smaller geometric distortions than the currently available seven-segment sheet (c) (5.54 ± 4.21 mm) and were both comparable to the reference scenario (a) (2.77 ± 2.24 mm). Contrasting these results with the temperature maps revealed that (d) performs as well as (a) in SPGR and EPI. We demonstrated that segmenting the transducer ground plane into a star pattern reduces eddy currents to a level wherein multi-plane EPI for accurate MR thermometry in tcMRgFUS is feasible.

Near-Infrared Surveys and the Potential of an Upgraded WFCAM on UKIRT

NASA Astrophysics Data System (ADS)

Green, Richard F.; Kerr, Tom; Varricatt, Watson; Bold, Matthew; Kendrick, Rick; Hodapp, Klaus

2015-08-01

Near-infrared surveys provide the samples of faint objects essential for characterizing the assembly and evolution of galaxies, both at earliest cosmic times and near the peak of star formation and black hole activity. Near-IR broad and medium-band filter measurements are critical for accurate photometric redshifts and spectral energy distributions. The same areal coverage combined with time domain sampling reveals the variability properties of pre-main sequence stars in regions of active star formation, particularly in the presence of appreciable reddening. The possibility of deep, very wide-area K-band coverage creates the opportunity to trace the outer regions of the Galaxy and the Local Group. Targeting for James Webb Space Telescope will depend on accurate contemporaneous Near-IR astrometry. NASA's mission objectives for protecting working spacecraft from orbital debris are facilitated by near-IR characterization of debris, particularly for objects dark in the visible like solar panels.As one realization of advanced survey capability, we describe a proposed upgrade to the Wide-Field camera on the UKIRT 3.8-m. The powerful performance of an array of Teledyne Hawaii-4RG detectors combined with a new corrector and filters promise a Northern Hemisphere capability matched to the next generation of science requirements. Anticipated improvements include (nearly) contiguous detectors (alleviating the need for a large-step dither pattern), higher DQE, and no restriction on field because of guide stars. We would be assured of better wide-area astrometry and sensitivity compared to the generation of devices used for UKIDSS and HEMISPHERE.

The TMT Adaptive Optics Program

NASA Astrophysics Data System (ADS)

Ellerbroek, Brent

2011-09-01

We provide an overview of the Thirty Meter Telescope (TMT) AO program, with an emphasis upon the progress made since the first AO4ELT conference held in 2009. The first light facility AO system for TMT is the Narrow Field Infra-Red AO System (NFIRAOS), which will provide diffraction-limited performance in the J, H, and K bands over 18-30 arc sec diameter fields with 50% sky coverage at the galactic pole. This is accomplished with order 60x60 wavefront sensing and correction, two deformable mirrors conjugate to ranges of 0 and 11.2 km, 6 sodium laser guide stars in an asterism with a diameter of 70 arc sec, and three low order (tip/tilt or tip/tilt focus), infra-red natural guide star (NGS) wavefront sensors deployable within a 2 arc minute diameter patrol field. The first light LGS asterism is generated by the Laser Guide Star Facility (LGSF), which initially incorporates 6 20-25W class laser systems mounted to the telescope elevation journal, a mirror-based beam transfer optics system, and a 0.4m diameter laser launch telescope located behind the TMT secondary mirror. Future plans for additional AO capabilities include a mid infra-red AO (MIRAO) system to support science instruments in the 4-20 micron range, a ground-layer AO (GLAO) system for wide-field spectroscopy, a multi-object AO (MOAO) system for multi-object integral field unit spectroscopy, and extreme AO (ExAO) for high contrast imaging. Significant progress has been made in developing the first-light AO architecture since 2009. This includes the adoption of a new NFIRAOS opto-mechanical design consisting of two off-axis parabola (OAP) relays in series, which eliminates field distortion and also significantly simplifies the designs of the LGS wavefront sensors, optical source simulators, and turbulence generator subsystem. The design of the LGSF has also been interated, and has been simplfied by the relocation of the (smaller, gravity invarient) laser systems to the telescope elevation journal. Protoyping activities continue for laser systems, wavefront sensing detectors, and deformable mirrors; work on the associated detector and deformable mirror electronics has also been initiated. AO Performance estimates and error budgets have been further detailed. Some of the modeling topics which have received particular attention include turbulence (Cn2) profile estimation from LGS WFS measurements, sodium layer range tracking, PSF reconstruction for multi-conjugate AO, LGS fratricide, astrometry at the galactic center, and further optimizing sky coverage and the peformance of the tip/tilt and low-order NGS mode control loops. Finally, experiments and field tests continue at the University of British Columbia LIDAR facility to measure the spatial and temporal variability of the sodium layer, and to characterize the sodium coupling efficiency of candidate laser systems for TMT.

Simple Activities for Powerful Impact

NASA Astrophysics Data System (ADS)

LaConte, K.; Shupla, C. B.; Dusenbery, P.; Harold, J. B.; Holland, A.

2016-12-01

STEM education is having a transformational impact on libraries across the country. The STAR Library Education Network (STAR_Net) provides free Science-Technology Activities & Resources that are helping libraries to engage their communities in STEM learning experiences. Hear the results of a national 2015 survey of library and STEM professionals and learn what STEM programming is currently in place in public libraries and how libraries approach and implement STEM programs. Experience hands-on space science activities that are being used in library programs with multiple age groups. Through these hands-on activities, learners explore the nature of science and employ science and engineering practices, including developing and using models, planning and carrying out investigations, and engaging in argument from evidence (NGSS Lead States, 2013). Learn how STAR_Net can help you print (free!) mini-exhibits and educator guides. Join STAR_Net's online community and access STEM resources and webinars to work with libraries in your local community.

KSC-2009-1691

NASA Image and Video Library

2009-02-18

CAPE CANAVERAL, Fla. – At the Astrotech payload processing facility in Titusville, Fla., workers help guide the canister segment for NASA's Kepler spacecraft as it is lifted toward workers above. The segment will be added to the stack around Kepler. The "canning" provides protection during the spacecraft's transport to the pad. The liftoff of Kepler aboard a Delta II rocket is currently targeted for 10:48 p.m. EST March 5 from Pad 17-B. Kepler is designed to survey more than 100,000 stars in our galaxy to determine the number of sun-like stars that have Earth-size and larger planets, including those that lie in a star's "habitable zone," a region where liquid water, and perhaps life, could exist. If these Earth-size worlds do exist around stars like our sun, Kepler is expected to be the first to find them and the first to measure how common they are. Photo credit: NASA/Troy Cryder

Design and application of star map simulation system for star sensors

NASA Astrophysics Data System (ADS)

Wu, Feng; Shen, Weimin; Zhu, Xifang; Chen, Yuheng; Xu, Qinquan

2013-12-01

Modern star sensors are powerful to measure attitude automatically which assure a perfect performance of spacecrafts. They achieve very accurate attitudes by applying algorithms to process star maps obtained by the star camera mounted on them. Therefore, star maps play an important role in designing star cameras and developing procession algorithms. Furthermore, star maps supply significant supports to exam the performance of star sensors completely before their launch. However, it is not always convenient to supply abundant star maps by taking pictures of the sky. Thus, star map simulation with the aid of computer attracts a lot of interests by virtue of its low price and good convenience. A method to simulate star maps by programming and extending the function of the optical design program ZEMAX is proposed. The star map simulation system is established. Firstly, based on analyzing the working procedures of star sensors to measure attitudes and the basic method to design optical system by ZEMAX, the principle of simulating star sensor imaging is given out in detail. The theory about adding false stars and noises, and outputting maps is discussed and the corresponding approaches are proposed. Then, by external programming, the star map simulation program is designed and produced. Its user interference and operation are introduced. Applications of star map simulation method in evaluating optical system, star image extraction algorithm and star identification algorithm, and calibrating system errors are presented completely. It was proved that the proposed simulation method provides magnificent supports to the study on star sensors, and improves the performance of star sensors efficiently.

Bringing the Visible Universe into Focus with Robo-AO

PubMed Central

Baranec, Christoph; Riddle, Reed; Law, Nicholas M.; Ramaprakash, A.N.; Tendulkar, Shriharsh P.; Bui, Khanh; Burse, Mahesh P.; Chordia, Pravin; Das, Hillol K.; Davis, Jack T.C.; Dekany, Richard G.; Kasliwal, Mansi M.; Kulkarni, Shrinivas R.; Morton, Timothy D.; Ofek, Eran O.; Punnadi, Sujit

2013-01-01

The angular resolution of ground-based optical telescopes is limited by the degrading effects of the turbulent atmosphere. In the absence of an atmosphere, the angular resolution of a typical telescope is limited only by diffraction, i.e., the wavelength of interest, λ, divided by the size of its primary mirror's aperture, D. For example, the Hubble Space Telescope (HST), with a 2.4-m primary mirror, has an angular resolution at visible wavelengths of ~0.04 arc seconds. The atmosphere is composed of air at slightly different temperatures, and therefore different indices of refraction, constantly mixing. Light waves are bent as they pass through the inhomogeneous atmosphere. When a telescope on the ground focuses these light waves, instantaneous images appear fragmented, changing as a function of time. As a result, long-exposure images acquired using ground-based telescopes - even telescopes with four times the diameter of HST - appear blurry and have an angular resolution of roughly 0.5 to 1.5 arc seconds at best. Astronomical adaptive-optics systems compensate for the effects of atmospheric turbulence. First, the shape of the incoming non-planar wave is determined using measurements of a nearby bright star by a wavefront sensor. Next, an element in the optical system, such as a deformable mirror, is commanded to correct the shape of the incoming light wave. Additional corrections are made at a rate sufficient to keep up with the dynamically changing atmosphere through which the telescope looks, ultimately producing diffraction-limited images. The fidelity of the wavefront sensor measurement is based upon how well the incoming light is spatially and temporally sampled1. Finer sampling requires brighter reference objects. While the brightest stars can serve as reference objects for imaging targets from several to tens of arc seconds away in the best conditions, most interesting astronomical targets do not have sufficiently bright stars nearby. One solution is to focus a high-power laser beam in the direction of the astronomical target to create an artificial reference of known shape, also known as a 'laser guide star'. The Robo-AO laser adaptive optics system2,3 employs a 10-W ultraviolet laser focused at a distance of 10 km to generate a laser guide star. Wavefront sensor measurements of the laser guide star drive the adaptive optics correction resulting in diffraction-limited images that have an angular resolution of ~0.1 arc seconds on a 1.5-m telescope. PMID:23426078

Bringing the visible universe into focus with Robo-AO.

PubMed

Baranec, Christoph; Riddle, Reed; Law, Nicholas M; Ramaprakash, A N; Tendulkar, Shriharsh P; Bui, Khanh; Burse, Mahesh P; Chordia, Pravin; Das, Hillol K; Davis, Jack T C; Dekany, Richard G; Kasliwal, Mansi M; Kulkarni, Shrinivas R; Morton, Timothy D; Ofek, Eran O; Punnadi, Sujit

2013-02-12

The angular resolution of ground-based optical telescopes is limited by the degrading effects of the turbulent atmosphere. In the absence of an atmosphere, the angular resolution of a typical telescope is limited only by diffraction, i.e., the wavelength of interest, λ, divided by the size of its primary mirror's aperture, D. For example, the Hubble Space Telescope (HST), with a 2.4-m primary mirror, has an angular resolution at visible wavelengths of ~0.04 arc seconds. The atmosphere is composed of air at slightly different temperatures, and therefore different indices of refraction, constantly mixing. Light waves are bent as they pass through the inhomogeneous atmosphere. When a telescope on the ground focuses these light waves, instantaneous images appear fragmented, changing as a function of time. As a result, long-exposure images acquired using ground-based telescopes--even telescopes with four times the diameter of HST--appear blurry and have an angular resolution of roughly 0.5 to 1.5 arc seconds at best. Astronomical adaptive-optics systems compensate for the effects of atmospheric turbulence. First, the shape of the incoming non-planar wave is determined using measurements of a nearby bright star by a wavefront sensor. Next, an element in the optical system, such as a deformable mirror, is commanded to correct the shape of the incoming light wave. Additional corrections are made at a rate sufficient to keep up with the dynamically changing atmosphere through which the telescope looks, ultimately producing diffraction-limited images. The fidelity of the wavefront sensor measurement is based upon how well the incoming light is spatially and temporally sampled. Finer sampling requires brighter reference objects. While the brightest stars can serve as reference objects for imaging targets from several to tens of arc seconds away in the best conditions, most interesting astronomical targets do not have sufficiently bright stars nearby. One solution is to focus a high-power laser beam in the direction of the astronomical target to create an artificial reference of known shape, also known as a 'laser guide star'. The Robo-AO laser adaptive optics system, employs a 10-W ultraviolet laser focused at a distance of 10 km to generate a laser guide star. Wavefront sensor measurements of the laser guide star drive the adaptive optics correction resulting in diffraction-limited images that have an angular resolution of ~0.1 arc seconds on a 1.5-m telescope.

EChO fine guidance sensor design and architecture

NASA Astrophysics Data System (ADS)

Ottensamer, Roland; Rataj, Miroslaw; Schrader, Jan-Rutger; Ferstl, Roman; Güdel, Manuel; Kerschbaum, Franz; Luntzer, Armin

2014-08-01

EChO, the Exoplanet Characterization Observatory, is an M-class candidate in the ESA Comic Vision programme. It will provide high resolution, multi-wavelength spectroscopic observations of exoplanets, measure their atmospheric composition, temperature and albedo. The scientific payload is a spectrometer covering the 0.4-11 micron waveband. High photometric stability over a time scale of about 10 hours is one of the most stringent requirements of the EChO mission. As a result, fine pointing stability relative to the host star is mandatory. This will be achieved through a Fine Guidance Sensor (FGS), a separate photometric channel that uses a fraction of the target star signal from the optical channel. The main task of the FGS is to ensure the centering, focusing and guiding of the satellite, but it will also provide supplemental high-precision astrometry and photometry of the target to ground for de-trending the spectra and complementary science. In this paper we give an overview of the current architectural design of the FGS subsystem and discuss related requirements as well as the expected performance.

Attitude Control System Design for the Solar Dynamics Observatory

NASA Technical Reports Server (NTRS)

Starin, Scott R.; Bourkland, Kristin L.; Kuo-Chia, Liu; Mason, Paul A. C.; Vess, Melissa F.; Andrews, Stephen F.; Morgenstern, Wendy M.

2005-01-01

The Solar Dynamics Observatory mission, part of the Living With a Star program, will place a geosynchronous satellite in orbit to observe the Sun and relay data to a dedicated ground station at all times. SDO remains Sun- pointing throughout most of its mission for the instruments to take measurements of the Sun. The SDO attitude control system is a single-fault tolerant design. Its fully redundant attitude sensor complement includes 16 coarse Sun sensors, a digital Sun sensor, 3 two-axis inertial reference units, 2 star trackers, and 4 guide telescopes. Attitude actuation is performed using 4 reaction wheels and 8 thrusters, and a single main engine nominally provides velocity-change thrust. The attitude control software has five nominal control modes-3 wheel-based modes and 2 thruster-based modes. A wheel-based Safehold running in the attitude control electronics box improves the robustness of the system as a whole. All six modes are designed on the same basic proportional-integral-derivative attitude error structure, with more robust modes setting their integral gains to zero. The paper details the mode designs and their uses.

Vibration control for the ARGOS laser launch path

NASA Astrophysics Data System (ADS)

Peter, Diethard; Gässler, Wolfgang; Borelli, Jose; Barl, Lothar; Rabien, S.

2012-07-01

Present and future adaptive optics systems aim for the correction of the atmospheric turbulence over a large field of view combined with large sky coverage. To achieve this goal the telescope is equipped with multiple laser beacons. Still, to measure tip-tilt aberrations a natural guide star is used. For some fields such a tilt-star is not available and a correction on the laser beacons alone is applied. For this method to work well the laser beacons must not be affected by telescope vibrations on their up-link path. For the ARGOS system the jitter of the beacons is specified to be below 0.05. To achieve this goal a vibration compensation system is necessary to mitigate the mechanical disturbances. The ARGOS vibration compensation system is an accelerometer based feed forward system. The accelerometer measurements are fed into a real time controller. To achieve high performance the controller of the system is model based. The output is applied to a fast steering mirror. This paper presents the concept of the ARGOS vibration compensation, the hardware, and laboratory results.

ANSI-ASQ National Accreditation Board /ACLASS

DTIC Science & Technology

2011-03-28

unclassified c. THIS PAGE unclassified Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std Z39-18  Laboratories – ISO / IEC 17025  Inspection...Bodies – ISO / IEC 17020  RMPs – ISO Guide 34 (Reference Materials)  PT Providers – ISO 17043  Product Certifiers – ISO Guide 65  Government...Programs: DoD ELAP, EPA Energy Star, CPSC Toy Safety, NRC, NIST IPV6, NLLAP, NEFAP  TRAINING Programs  Certification Bodies – ISO / IEC 17021

Soldier Quality of Life (Operational) and Readiness at Contingency Base Camps: Insights From Qualitative Interviews

DTIC Science & Technology

2017-03-13

camps and Soldier/small unit readiness to guide the development of a quantitative readiness survey . • During structured interviews, 31 Soldiers...camps and Soldier/small unit readiness to guide the development of a quantitative readiness survey . 11UNCLASSIFIED Click to hear quote Methods...We were rock stars.” 60UNCLASSIFIED • These data are driving the selection of attributes for a future quantitative survey of the link between QoL

GMTIFS: the adaptive optics beam steering mirror for the GMT integral-field spectrograph

NASA Astrophysics Data System (ADS)

Davies, J.; Bloxham, G.; Boz, R.; Bundy, D.; Espeland, B.; Fordham, B.; Hart, J.; Herrald, N.; Nielsen, J.; Sharp, R.; Vaccarella, A.; Vest, C.; Young, P. J.

2016-07-01

To achieve the high adaptive optics sky coverage necessary to allow the GMT Integral-Field Spectrograph (GMTIFS) to access key scientific targets, the on-instrument adaptive-optics wavefront-sensing (OIWFS) system must patrol the full 180 arcsecond diameter guide field passed to the instrument. The OIWFS uses a diffraction limited guide star as the fundamental pointing reference for the instrument. During an observation the offset between the science target and the guide star will change due to sources such as flexure, differential refraction and non-sidereal tracking rates. GMTIFS uses a beam steering mirror to set the initial offset between science target and guide star and also to correct for changes in offset. In order to reduce image motion from beam steering errors to those comparable to the AO system in the most stringent case, the beam steering mirror is set a requirement of less than 1 milliarcsecond RMS. This corresponds to a dynamic range for both actuators and sensors of better than 1/180,000. The GMTIFS beam steering mirror uses piezo-walk actuators and a combination of eddy current sensors and interferometric sensors to achieve this dynamic range and control. While the sensors are rated for cryogenic operation, the actuators are not. We report on the results of prototype testing of single actuators, with the sensors, on the bench and in a cryogenic environment. Specific failures of the system are explained and suspected reasons for them. A modified test jig is used to investigate the option of heating the actuator and we report the improved results. In addition to individual component testing, we built and tested a complete beam steering mirror assembly. Testing was conducted with a point source microscope, however controlling environmental conditions to less than 1 micron was challenging. The assembly testing investigated acquisition accuracy and if there was any un-sensed hysteresis in the system. Finally we present the revised beam steering mirror design based on the outcomes and lessons learnt from this prototyping.

Simple wavefront correction framework for two-photon microscopy of in-vivo brain

PubMed Central

Galwaduge, P. T.; Kim, S. H.; Grosberg, L. E.; Hillman, E. M. C.

2015-01-01

We present an easily implemented wavefront correction scheme that has been specifically designed for in-vivo brain imaging. The system can be implemented with a single liquid crystal spatial light modulator (LCSLM), which makes it compatible with existing patterned illumination setups, and provides measurable signal improvements even after a few seconds of optimization. The optimization scheme is signal-based and does not require exogenous guide-stars, repeated image acquisition or beam constraint. The unconstrained beam approach allows the use of Zernike functions for aberration correction and Hadamard functions for scattering correction. Low order corrections performed in mouse brain were found to be valid up to hundreds of microns away from the correction location. PMID:26309763

Chemical Evolution and History of Star Formation in the Large Magellanic Cloud

NASA Astrophysics Data System (ADS)

Gustafsson, Bengt

1995-07-01

Large scale processes controlling star formation and nucleosynthesis are fundamental but poorly understood. This is especially true for external galaxies. A detailed study of individual main sequence stars in the LMC Bar is proposed. The LMC is close enough to allow this, has considerable spread in stellar ages and a structure permitting identification of stellar populations and their structural features. The Bar presumably plays a dominant role in the chemical and dynamical evolution of the galaxy. Our knowledge is, at best, based on educated guesses. Still, the major population of the Bar is quite old, and many member stars are relatively evolved. The Bar seems to contain stars similar to those of Intermediate to Extreme Pop II in the Galaxy. We want to study the history of star formation, chemical evolution and initial mass function of the population dominating the Bar. We will use field stars close to the turn off point in the HR diagram. From earlier studies, we know that 250-500 such stars are available for uvby photometry in the PC field. We aim at an accuracy of 0.1 -0.2 dex in Me/H and 25% or better in relative ages. This requires an accuracy of about 0.02 mag in the uvby indices, which can be reached, taking into account errors in calibration, flat fielding, guiding and problems due to crowding. For a study of the luminosity function fainter stars will be included as well. Calibration fields are available in Omega Cen and M 67.

The EB factory project. I. A fast, neural-net-based, general purpose light curve classifier optimized for eclipsing binaries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Paegert, Martin; Stassun, Keivan G.; Burger, Dan M.

2014-08-01

We describe a new neural-net-based light curve classifier and provide it with documentation as a ready-to-use tool for the community. While optimized for identification and classification of eclipsing binary stars, the classifier is general purpose, and has been developed for speed in the context of upcoming massive surveys such as the Large Synoptic Survey Telescope. A challenge for classifiers in the context of neural-net training and massive data sets is to minimize the number of parameters required to describe each light curve. We show that a simple and fast geometric representation that encodes the overall light curve shape, together withmore » a chi-square parameter to capture higher-order morphology information results in efficient yet robust light curve classification, especially for eclipsing binaries. Testing the classifier on the ASAS light curve database, we achieve a retrieval rate of 98% and a false-positive rate of 2% for eclipsing binaries. We achieve similarly high retrieval rates for most other periodic variable-star classes, including RR Lyrae, Mira, and delta Scuti. However, the classifier currently has difficulty discriminating between different sub-classes of eclipsing binaries, and suffers a relatively low (∼60%) retrieval rate for multi-mode delta Cepheid stars. We find that it is imperative to train the classifier's neural network with exemplars that include the full range of light curve quality to which the classifier will be expected to perform; the classifier performs well on noisy light curves only when trained with noisy exemplars. The classifier source code, ancillary programs, a trained neural net, and a guide for use, are provided.« less

15x optical zoom and extreme optical image stabilisation: diffraction limited integral field spectroscopy with the Oxford SWIFT spectrograph

NASA Astrophysics Data System (ADS)

Tecza, Matthias; Thatte, Niranjan; Clarke, Fraser; Lynn, James; Freeman, David; Roberts, Jennifer; Dekany, Richard

2012-09-01

When commissioned in November 2008 at the Palomar 200 inch Hale Telescope, the Oxford SWIFT I and z band integral field spectrograph, fed by the adaptive optics system PALAO, provided a wide (3×) range of spatial resolutions: three plate scales of 235 mas, 160 mas, and 80 mas per spaxel over a contiguous field-of-view of 89×44 pixels. Depending on observing conditions and guide star brightness we can choose a seeing limited scale of 235 mas per spaxel, or 160 mas and 80 mas per spaxel for very bright guide star AO with substantial increase of enclosed energy. Over the last two years PALAO was upgraded to PALM-3000: an extreme, high-order adaptive optics system with two deformable mirrors with more than 3000 actuators, promising diffraction limited performance in SWIFT's wavelength range. In order to take advantage of this increased spatial resolution we upgraded SWIFT with new pre-optics allowing us to spatially Nyquist sample the diffraction limited PALM-3000 point spread function with 16 mas resolution, reducing the spaxel scale by another factor of 5×. We designed, manufactured, integrated and tested the new pre-optics in the first half of 2011 and commissioned it in December 2011. Here we present the opto-mechanical design and assembly of the new scale changing optics, as well as laboratory and on-sky commissioning results. In optimal observing conditions we achieve substantial Strehl ratios, delivering the near diffraction limited spatial resolution in the I and z bands.

Star tracking method based on multiexposure imaging for intensified star trackers.

PubMed

Yu, Wenbo; Jiang, Jie; Zhang, Guangjun

2017-07-20

The requirements for the dynamic performance of star trackers are rapidly increasing with the development of space exploration technologies. However, insufficient knowledge of the angular acceleration has largely decreased the performance of the existing star tracking methods, and star trackers may even fail to track under highly dynamic conditions. This study proposes a star tracking method based on multiexposure imaging for intensified star trackers. The accurate estimation model of the complete motion parameters, including the angular velocity and angular acceleration, is established according to the working characteristic of multiexposure imaging. The estimation of the complete motion parameters is utilized to generate the predictive star image accurately. Therefore, the correct matching and tracking between stars in the real and predictive star images can be reliably accomplished under highly dynamic conditions. Simulations with specific dynamic conditions are conducted to verify the feasibility and effectiveness of the proposed method. Experiments with real starry night sky observation are also conducted for further verification. Simulations and experiments demonstrate that the proposed method is effective and shows excellent performance under highly dynamic conditions.

Performance Evaluation of a Firm Real-Time DataBase System

DTIC Science & Technology

1995-01-01

after its deadline has passed. StarBase differs from previous real-time database work in that a) it relies on a real - time operating system which...StarBase, running on a real - time operating system kernel, RT-Mach. We discuss how performance was evaluated in StarBase using the StarBase workload

A software package for evaluating the performance of a star sensor operation

NASA Astrophysics Data System (ADS)

Sarpotdar, Mayuresh; Mathew, Joice; Sreejith, A. G.; Nirmal, K.; Ambily, S.; Prakash, Ajin; Safonova, Margarita; Murthy, Jayant

2017-02-01

We have developed a low-cost off-the-shelf component star sensor ( StarSense) for use in minisatellites and CubeSats to determine the attitude of a satellite in orbit. StarSense is an imaging camera with a limiting magnitude of 6.5, which extracts information from star patterns it records in the images. The star sensor implements a centroiding algorithm to find centroids of the stars in the image, a Geometric Voting algorithm for star pattern identification, and a QUEST algorithm for attitude quaternion calculation. Here, we describe the software package to evaluate the performance of these algorithms as a star sensor single operating system. We simulate the ideal case where sky background and instrument errors are omitted, and a more realistic case where noise and camera parameters are added to the simulated images. We evaluate such performance parameters of the algorithms as attitude accuracy, calculation time, required memory, star catalog size, sky coverage, etc., and estimate the errors introduced by each algorithm. This software package is written for use in MATLAB. The testing is parametrized for different hardware parameters, such as the focal length of the imaging setup, the field of view (FOV) of the camera, angle measurement accuracy, distortion effects, etc., and therefore, can be applied to evaluate the performance of such algorithms in any star sensor. For its hardware implementation on our StarSense, we are currently porting the codes in form of functions written in C. This is done keeping in view its easy implementation on any star sensor electronics hardware.

Stellar Populations in the Central 0.5 pc of the Galaxy. I. A New Method for Constructing Luminosity Functions and Surface-density Profiles

NASA Astrophysics Data System (ADS)

Do, T.; Lu, J. R.; Ghez, A. M.; Morris, M. R.; Yelda, S.; Martinez, G. D.; Wright, S. A.; Matthews, K.

2013-02-01

We present new high angular resolution near-infrared spectroscopic observations of the nuclear star cluster surrounding the Milky Way's central supermassive black hole. Using the integral-field spectrograph OSIRIS on Keck II behind the laser-guide-star adaptive optics system, this spectroscopic survey enables us to separate early-type (young, 4-6 Myr) and late-type (old, >1 Gyr) stars with a completeness of 50% down to K' = 15.5 mag, which corresponds to ~10 M ⊙ for the early-type stars. This work increases the radial extent of reported OSIRIS/Keck measurements by more than a factor of three from 4'' to 14'' (0.16 to 0.56 pc), along the projected disk of young stars. For our analysis, we implement a new method of completeness correction using a combination of star-planting simulations and Bayesian inference. We assign probabilities for the spectral type of every source detected in deep imaging down to K' = 15.5 mag using information from spectra, simulations, number counts, and the distribution of stars. The inferred radial surface-density profiles, Σ(R)vpropR -Γ, for the young stars and late-type giants are consistent with earlier results (Γearly = 0.93 ± 0.09, Γlate = 0.16 ± 0.07). The late-type surface-density profile is approximately flat out to the edge of the survey. While the late-type stellar luminosity function is consistent with the Galactic bulge, the completeness-corrected luminosity function of the early-type stars has significantly more young stars at faint magnitudes compared with previous surveys with similar depth. This luminosity function indicates that the corresponding mass function of the young stars is likely less top-heavy than that inferred from previous surveys.

In search of Nemesis

NASA Technical Reports Server (NTRS)

Carlson, S.; Culler, T.; Muller, R. A.; Tetreault, M.; Perlmutter, S.

1994-01-01

The parallax of all stars of visual magnitude greater than about 6.5 has already been measured. If Nemesis is a main-sequence star 1 parsec away, this requires Nemesis's mass to be less than about 0.4 solar masses. If it were less than about 0.05 solar masses its gravity would be too weak to trigger a comet storm. If Nemesis is on the main sequence, this mass range requires it to be a red dwarf. A red dwarf companion would probably have been missed by standard astronomical surveys. Nearby stars are usually found because they are bright or have high proper motion. However, Nemesis's proper motion would now be 0.01 arcsec/yr, and if it is a red dwarf its magnitude is about 10 - too dim to attract attention. Unfortunately, standard four-color photometry does not distinguish between red dwarfs and giants. So although surveys such as the Dearborn Red Star Catalog list stars by magnitude and spectral type, they do not identify the dwarfs. Every star of the correct spectral type and magnitude must be scrutinized. Our candidate list is a hybrid; candidate red stars are identified in the astrometrically poor Dearborn Red Star Catalog and their positions are corrected using the Hubble Guide Star Catalog. When errors in the Dearborn catalog make it impossible to identify the corresponding Hubble star, the fields are split so that we have one centering on each possible candidate. We are currently scrutinizing 3098 fields, which we believe contain all possible red dwarf candidates in the northern hemisphere. Since our last report the analysis and database software has been completely rebuilt to take advantage of updated hardware, to make the data more accessible, and to implement improved methods of data analysis. The software is now completed and we are eliminating stars every clear night.

VizieR Online Data Catalog: A Finding List of Faint UV-Bright Stars (Lanning+, 1998)

NASA Astrophysics Data System (ADS)

Lanning, H. H.

1997-02-01

The Sandage two-color photographic survey was originally made in support of the UHURU x-ray satellite in order to identify those optical counterparts of the detected x-ray sources found in the galactic plane. During inspection of the plates, however, many UV-bright objects fainter than 10th magnitude were seen in the general field. A larger image in the U filter suggested the possibility of a bluer object as in the case of low-luminosity stars, white dwarfs, novae, CVs, normal early B stars, etc. As these are interesting in themselves, it was decided to publish a catalog for the use of other observers. This multi-color photographic technique has been described, for example, by Haro and Herbig (1955). The survey was concentrated on objects with m(B)~10 or fainter. It employed the Palomar 48-in (Oschin) Schmidt telescope and was centered on the galactic plane with overlapping regions covering the galactic latitudes +- 9 degrees, and extending throughout most of the northern plane (l = 0 deg - 227 deg). Plates were taken by J. Kristian, A.R. Sandage, R.J. Brucato, and Lanning, primarily. The data presented here were found following a careful examination of the plates but it should not be assumed these data represent a complete survey of the fields examined. The categories were roughly calibrated against photoelectric (U-B) measures, but a full scale calibration program, including magnitude effects, etc. was not done. The numerical (U-B) limits of the tables should not therefore be taken precisely. The blue magnitude of the sources in the finding list has been estimated using these photoelectric values as a guide but should be considered accurate to only +- 0.5 mag. due to the difficulty of adjusting to the various plate characteristics. Positions were measured from images retrieved from the Space Telescope Science Institute collection of Guide Star digital plate scans. The accuracy of positions from the Guide Star Catalog images has been estimated to be on the order of 0.2-0.8 arcsec (Russell et al. 1990) Information provided by Bidelman (private communication) resulted in the discovery that 15 positions for objects listed in Paper II were in error. Investigation indicated that an incorrect header was associated with the scan of the Guide Star plate originally archived onto optical disk. The incorrect astrometric solution, based on the use of an incorrect origin point, was subsequently applied in the positional determination when centroiding the object. The average offset for positions in right ascension is 14.17 seconds of time, with no detectable trend in the numbers. The offsets in declination range from +6.56 arcseconds through zero to -6.85 arcseconds as one progresses from west to east across the plate. This is consistent with a rotation being introduced into the bad plate solution. Objects with incorrect positions included Lanning 96, 97, 98, 99, 100, 102, 104, 108, 111, 113, 114, 115, 116, 119, and 122. uv.dat contains the corrected coordinates. (2 data files).

Community pharmacy owners' views of star ratings and performance measurement: In-depth interviews.

PubMed

Teeter, Benjamin S; Fox, Brent I; Garza, Kimberly B; Harris, Stanley G; Nau, David P; Owensby, Justin K; Westrick, Salisa C

2016-01-01

The star rating system implemented by Medicare has the potential to positively affect patient health and may have financial implications for community pharmacies. Learning from owners of community pharmacies with high performance on these quality measures may help us to identify and further understand factors contributing to their success. This study described high-performing community pharmacy owners' current awareness and knowledge of star ratings, attitudes toward star ratings and performance measurement, and initiatives being offered in pharmacies that aim to improve the quality of care. Qualitative interviews with owners of independent community pharmacies were conducted in Spring 2015. Fifteen community pharmacies with high performance on the star rating measures were invited to participate. Recruitment did not end until the saturation point had been reached. All interviews were transcribed verbatim. Interview data were analyzed with the use of ATLAS.ti by 2 coders trained in thematic analysis. Krippendorf's alpha was calculated to assess intercoder reliability. Ten high-performing pharmacy owners participated. Analysis identified 8 themes, which were organized into the following categories: 1) current awareness and knowledge (i.e., superficial or advanced knowledge); 2) attitudes toward star ratings (positive perceptions, skeptical of performance rewards, and lack a feeling of control); and 3) pharmacy initiatives (personal patient relationships, collaborative employee relationships, and use of technology). Intercoder reliability was good overall. Interviews with high-performing pharmacies suggested that awareness of the star rating measures, overall positive attitudes toward the star ratings, the relationships that pharmacy owners have with their patients and their employees, and the use of technology as a tool to enhance patient care may contribute to high performance on the star rating measures. Future research is needed to determine if and how these constructs are associated with pharmacy performance in a larger population. Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

The Kepler Data Processing Handbook: A Field Guide to Prospecting for Habitable Worlds

NASA Technical Reports Server (NTRS)

Jenkins, Jon M.

2017-01-01

The Kepler telescope hurtled into orbit in March 2009, initiating NASA's first mission to discover Earth-size planets orbiting Sun-like stars. Kepler simultaneously collected data for approximately 165,000 target stars at a time over its four-year mission, identifying over 4700 planet candidates, over 2300 confirmed or validated planets, and over 2100 eclipsing binaries. While Kepler was designed to discover exoplanets, the long-term, ultrahigh photometric precision measurements it achieved made it a premier observational facility for stellar astrophysics, especially in the field of asteroseismology, and for variable stars, such as RR Lyrae. The Kepler Science Operations Center (SOC) was developed at NASA Ames Research Center to process the data acquired by Kepler from pixel-level calibrations all the way to identifying transiting planet signatures and subjecting them to a suite of diagnostic tests to establish or break confidence in their planetary nature. Detecting small, rocky planets transiting Sun-like stars presents a variety of daunting challenges, including achieving an unprecedented photometric precision of 20 ppm on 6.5-hour timescales, and supporting the science operations, management, processing, and repeated reprocessing of the accumulating data stream. A newly revised and expanded version of the Kepler Data Processing Handbook (KDPH) has been released to support the legacy archival products. The KDPH details the theory, design and performance of the algorithms supporting each data processing step. This paper presents an overview of the KDPH and features illustrations of several key algorithms in the Kepler Science Data Processing Pipeline. Kepler was selected as the 10th mission of the Discovery Program. Funding for this mission is provided by NASA, Science Mission Directorate.

Astrophotography Basics: Meteors, Comets, Eclipses, Aurorae, Star Trails. Revised.

ERIC Educational Resources Information Center

Eastman Kodak Co., Rochester, NY.

This pamphlet gives an introduction to the principles of astronomical picture-taking. Chapters included are: (1) "Getting Started" (describing stationary cameras, sky charts and mapping, guided cameras, telescopes, brightness of astronomical subjects, estimating exposure, film selection, camera filters, film processing, and exposure for…

StarGuides Plus

NASA Astrophysics Data System (ADS)

Heck, A.

StarGuides Plus represents the most comprehensive and accurately validated collection of practical data on organizations involved in astronomy, related space sciences and other related fields. This invaluable reference source (and its companion volume, StarBriefs Plus) should be on the reference shelf of every library, organization or individual with any interest in these areas. The coverage includes relevant universities, scientific committees, institutions, associations, societies, agencies, companies, bibliographic services, data centers, museums, dealers, distributors, funding organizations, journals, manufacturers, meteorological services, national norms & standard institutes, parent associations & societies, publishers, software producers & distributors, and so on. Besides astronomy and associated space sciences, related fields such as aeronautics, aeronomy, astronautics, atmospheric sciences, chemistry, communications, computer sciences, data processing, education, electronics, engineering, energetics, environment, geodesy, geophysics, information handling, management, mathematics, meteorology, optics, physics, remote sensing, and so on, are also covered where appropriate. After some thirty years in continuous compilation, verification and updating, StarGuides Plus currently gathers together some 6,000 entries from 100 countries. The information is presented in a clear, uncluttered manner for direct and easy use. For each entry, all practical data are listed: city, postal and electronic-mail addresses, telephone and fax numbers, URLs for WWW access, foundation years, numbers of members and/or numbers of staff, main activities, publications titles (with frequencies, ISS-Numbers and circulations), names and geographical coordinates of observing sites, names of planetariums, awards (prizes and/or distinctions) granted, etc. The entries are listed alphabetically in each country. An exhaustive index gives a breakdown not only by different designations and acronyms, but also by location and major terms in names. Thematic sub-indices are also provided as well as a list of telephone and telefax national codes. In short, almost anyone involved in any way in the fields of astronomy and related space sciences will find invaluable contact and background information in this volume. All entries have been compiled from data supplied by the listed organizations and all data have been independently verified - making this compilation the most accurate and relevant source available. Link: http://www.wkap.nl/prod/b/1-4020-1926-2

Fluorescent supramolecular micelles for imaging-guided cancer therapy

NASA Astrophysics Data System (ADS)

Sun, Mengmeng; Yin, Wenyan; Dong, Xinghua; Yang, Wantai; Zhao, Yuliang; Yin, Meizhen

2016-02-01

A novel smart fluorescent drug delivery system composed of a perylene diimide (PDI) core and block copolymer poly(d,l-lactide)-b-poly(ethyl ethylene phosphate) is developed and named as PDI-star-(PLA-b-PEEP)8. The biodegradable PDI-star-(PLA-b-PEEP)8 is a unimolecular micelle and can self-assemble into supramolecular micelles, called as fluorescent supramolecular micelles (FSMs), in aqueous media. An insoluble drug camptothecin (CPT) can be effectively loaded into the FSMs and exhibits pH-responsive release. Moreover, the FSMs with good biocompatibility can also be employed as a remarkable fluorescent probe for cell labelling because the maximum emission of PDI is beneficial for bio-imaging. The flow cytometry and confocal laser scanning microscopy analysis demonstrate that the micelles are easily endocytosed by cancer cells. In vitro and in vivo tumor growth-inhibitory studies reveal a better therapeutic effect of FSMs after CPT encapsulation when compared with the free CPT drug. The multifunctional FSM nanomedicine platform as a nanovehicle has great potential for fluorescence imaging-guided cancer therapy.A novel smart fluorescent drug delivery system composed of a perylene diimide (PDI) core and block copolymer poly(d,l-lactide)-b-poly(ethyl ethylene phosphate) is developed and named as PDI-star-(PLA-b-PEEP)8. The biodegradable PDI-star-(PLA-b-PEEP)8 is a unimolecular micelle and can self-assemble into supramolecular micelles, called as fluorescent supramolecular micelles (FSMs), in aqueous media. An insoluble drug camptothecin (CPT) can be effectively loaded into the FSMs and exhibits pH-responsive release. Moreover, the FSMs with good biocompatibility can also be employed as a remarkable fluorescent probe for cell labelling because the maximum emission of PDI is beneficial for bio-imaging. The flow cytometry and confocal laser scanning microscopy analysis demonstrate that the micelles are easily endocytosed by cancer cells. In vitro and in vivo tumor growth-inhibitory studies reveal a better therapeutic effect of FSMs after CPT encapsulation when compared with the free CPT drug. The multifunctional FSM nanomedicine platform as a nanovehicle has great potential for fluorescence imaging-guided cancer therapy. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr00450d

Updated Starshade Technology Gap List

NASA Astrophysics Data System (ADS)

Crill, Brendan P.; Siegler, Nicholas

2017-01-01

NASA's Exoplanet Exploration Program (ExEP) guides the development of technology that enables the direct imaging and characterization of exo-Earths in the habitable zone of their stars, for future space observatories. Here we present the Starshade portion of the 2017 ExEP Enabling Technology Gap List, an annual update to ExEP's list of of technology to be advanced in the next 1-5 years. A Starshade is an external occulter on an independent spacecraft, allowing a space telescope to achieve exo-Earth imaging contrast requirements by blocking starlight before it enters the telescope. Building and operating a Starshade requires new technology: the occulter is a structure tens of meters in diameter that must be positioned precisely at a distance of tens of thousands of kilometers from the telescope. We review the current state-of-the-art performance and the performance level that must be achieved for a Starshade.

Technologies Required to Image Earth 2.0 with a Space Coronagraph

NASA Astrophysics Data System (ADS)

Siegler, Nicholas

2017-01-01

NASA's Exoplanet Exploration Program (ExEP) guides the development of technology that enables the direct imaging and characterization of exo-Earths in the habitable zone of their stars for future space observatories. Here we present the coronagraph portion of the 2017 ExEP Technology Gap List, an annual update to ExEP's list of of technologies, to be advanced in the next 1-5 years. A coronagraph is an internal occulter that allows a space telescope to achieve exo-Earth imaging contrast requirements (more than 10 billion) by blocking on-axis starlight while allowing the reflected light of off-axis exoplanets be detected. Building and operating a space coronagraph capable of imaging an exo-Earth will require new technologies beyond those of WFIRST, the first high-contrast conronagraph in space. We review the current state-of-the-art performance of space coronagraphs and the performance level that must be achieved for a coronagraph..

Possible Observational Criteria for Distinguishing Brown Dwarfs From Planets

NASA Technical Reports Server (NTRS)

Black, David C.

1997-01-01

The difference in formation process between binary stars and planetary systems is reflected in their composition, as well as orbital architecture, particularly in their orbital eccentricity as a function of orbital period. It is suggested here that this difference can be used as an observational criterion to distinguish between brown dwarfs and planets. Application of the orbital criterion suggests that, with three possible exceptions, all of the recently discovered substellar companions may be brown dwarfs and not planets. These criterion may be used as a guide for interpretation of the nature of substellar-mass companions to stars in the future.

A Study Guide for the Analysis of Gaia Astrometic Data

NASA Astrophysics Data System (ADS)

van Altena, W. F.

2018-01-01

The purpose of this paper is to enthusiastically support the use of Gaia's data and to suggest an approach for improving our backgrounds so that its data is used in the best possible manner. The principal goals of the Gaia mission are to investigate the origin and subsequent evolution of the Milky Way by mapping the Galaxy to the 20th magnitude and the determination of positions, parallaxes and proper motions of 109 stars. In addition, Gaia is to determine spectroscopic data including the metallicity, distance, extinction and radial velocities for 150× 106 stars brighter than 15th magnitude.

Predicting the locations of possible long-lived low-mass first stars: importance of satellite dwarf galaxies

NASA Astrophysics Data System (ADS)

Magg, Mattis; Hartwig, Tilman; Agarwal, Bhaskar; Frebel, Anna; Glover, Simon C. O.; Griffen, Brendan F.; Klessen, Ralf S.

2018-02-01

The search for metal-free stars has so far been unsuccessful, proving that if there are surviving stars from the first generation, they are rare, they have been polluted or we have been looking in the wrong place. To predict the likely location of Population III (Pop III) survivors, we semi-analytically model early star formation in progenitors of Milky Way-like galaxies and their environments. We base our model on merger trees from the high-resolution dark matter only simulation suite Caterpillar. Radiative and chemical feedback are taken into account self-consistently, based on the spatial distribution of the haloes. Our results are consistent with the non-detection of Pop III survivors in the Milky Way today. We find that possible surviving Pop III stars are more common in Milky Way satellites than in the main Galaxy. In particular, low-mass Milky Way satellites contain a much larger fraction of Pop III stars than the Milky Way. Such nearby, low-mass Milky Way satellites are promising targets for future attempts to find Pop III survivors, especially for high-resolution, high signal-to-noise spectroscopic observations. We provide the probabilities of finding a Pop III survivor in the red giant branch phase for all known Milky Way satellites to guide future observations.

Young Stellar Populations in MYStIX Star-forming Regions: Candidate Protostars

NASA Astrophysics Data System (ADS)

Romine, Gregory; Feigelson, Eric D.; Getman, Konstantin V.; Kuhn, Michael A.; Povich, Matthew S.

2016-12-01

The Massive Young Star-Forming Complex in Infrared and X-ray (MYStIX) project provides a new census on stellar members of massive star-forming regions within 4 kpc. Here the MYStIX Infrared Excess catalog and Chandra-based X-ray photometric catalogs are mined to obtain high-quality samples of Class I protostars using criteria designed to reduce extragalactic and Galactic field star contamination. A total of 1109 MYStIX Candidate Protostars (MCPs) are found in 14 star-forming regions. Most are selected from protoplanetary disk infrared excess emission, but 20% are found from their ultrahard X-ray spectra from heavily absorbed magnetospheric flare emission. Two-thirds of the MCP sample is newly reported here. The resulting samples are strongly spatially associated with molecular cores and filaments on Herschel far-infrared maps. This spatial agreement and other evidence indicate that the MCP sample has high reliability with relatively few “false positives” from contaminating populations. But the limited sensitivity and sparse overlap among the infrared and X-ray subsamples indicate that the sample is very incomplete with many “false negatives.” Maps, tables, and source descriptions are provided to guide further study of star formation in these regions. In particular, the nature of ultrahard X-ray protostellar candidates without known infrared counterparts needs to be elucidated.

Novel approach to improve the attitude update rate of a star tracker.

PubMed

Zhang, Shuo; Xing, Fei; Sun, Ting; You, Zheng; Wei, Minsong

2018-03-05

The star tracker is widely used in attitude control systems of spacecraft for attitude measurement. The attitude update rate of a star tracker is important to guarantee the attitude control performance. In this paper, we propose a novel approach to improve the attitude update rate of a star tracker. The electronic Rolling Shutter (RS) imaging mode of the complementary metal-oxide semiconductor (CMOS) image sensor in the star tracker is applied to acquire star images in which the star spots are exposed with row-to-row time offsets, thereby reflecting the rotation of star tracker at different times. The attitude estimation method with a single star spot is developed to realize the multiple attitude updates by a star image, so as to reach a high update rate. The simulation and experiment are performed to verify the proposed approaches. The test results demonstrate that the proposed approach is effective and the attitude update rate of a star tracker is increased significantly.

Measuring the stellar luminosity function and spatial density profile of the inner 0.5 pc of the Milky Way nuclear star cluster

NASA Astrophysics Data System (ADS)

Do, Tuan; Ghez, Andrea; Lu, Jessica R.; Morris, Mark R.; Yelda, Sylvana; Martinez, Gregory D.; Peter, Annika H. G.; Wright, Shelley; Bullock, James; Kaplinghat, Manoj; Matthews, K.

2012-07-01

We report on measurements of the luminosity function of early (young) and late-type (old) stars in the central 0.5 pc of the Milky Way nuclear star cluster as well as the density profiles of both components. The young (~ 6 Myr) and old stars (> 1 Gyr) in this region provide different physical probes of the environment around a supermassive black hole; the luminosity function of the young stars offers us a way to measure the initial mass function from star formation in an extreme environment, while the density profile of the old stars offers us a probe of the dynamical interaction of a star cluster with a massive black hole. The two stellar populations are separated through a near-infrared spectroscopic survey using the integral-field spectrograph OSIRIS on Keck II behind the laser guide star adaptive optics system. This spectroscopic survey is able to separate early-type (young) and late-type (old) stars with a completeness of 50% at K' = 15.5. We describe our method of completeness correction using a combination of star planting simulations and Bayesian inference. The completeness corrected luminosity function of the early-type stars contains significantly more young stars at faint magnitudes compared to previous surveys with similar depth. In addition, by using proper motion and radial velocity measurements along with anisotropic spherical Jeans modeling of the cluster, it is possible to measure the spatial density profile of the old stars, which has been difficult to constrain with number counts alone. The most probable model shows that the spatial density profile, n(r) propto r-γ, to be shallow with γ = 0.4 ± 0.2, which is much flatter than the dynamically relaxed case of γ = 3/2 to 7/4, but does rule out a 'hole' in the distribution of old stars. We show, for the first time, that the spatial density profile, the black hole mass, and velocity anisotropy can be fit simultaneously to obtain a black hole mass that is consistent with that derived from individual orbits of stars at distances < 1000 AU from the Galactic center.

Detecting non-uniform period spacings in the Kepler photometry of γ Doradus stars: methodology and case studies

NASA Astrophysics Data System (ADS)

Van Reeth, T.; Tkachenko, A.; Aerts, C.; Pápics, P. I.; Degroote, P.; Debosscher, J.; Zwintz, K.; Bloemen, S.; De Smedt, K.; Hrudkova, M.; Raskin, G.; Van Winckel, H.

2015-02-01

Context. The analysis of stellar oscillations is one of the most reliable ways to probe stellar interiors. Recent space missions such as Kepler have provided us with an opportunity to study these oscillations with unprecedented detail. For many multi-periodic pulsators such as γ Doradus stars, this led to the detection of dozens to hundreds of oscillation frequencies that could not be found from ground-based observations. Aims: We aim to detect non-uniform period spacings in the Fourier spectra of a sample of γ Doradus stars observed by Kepler. Such detection is complicated by both the large number of significant frequencies in the space photometry and by overlapping non-equidistant rotationally split multiplets. Methods: Guided by theoretical properties of gravity-mode oscillation of γ Doradus stars, we developed a period-spacing detection method and applied it to Kepler observations of a few stars, after having tested the performance from simulations. Results: The application of the technique resulted in the clear detection of non-uniform period spacing series for three out of the five treated Kepler targets. Disadvantages of the technique are also discussed, and include the disability to distinguish between different values of the spherical degree and azimuthal order of the oscillation modes without additional theoretical modelling. Conclusions: Despite the shortcomings, the method is shown to allow solid detections of period spacings for γ Doradus stars, which will allow future asteroseismic analyses of these stars. Based on data gathered with the NASA Discovery mission Kepler and the HERMES spectrograph, which is installed at the Mercator Telescope, operated on the island of La Palma by the Flemish Community at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias, and supported by the Fund for Scientific Research of Flanders (FWO), Belgium, the Research Council of KU Leuven, Belgium, the Fonds National de la Recherche Scientifique (F.R.S.-FNRS), Belgium, the Royal Observatory of Belgium, the Observatoire de Genève, Switzerland, and the Thüringer Landessternwarte Tautenburg, Germany.Table A.1 is only available in electronic form at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/574/A17

Spacecraft angular velocity estimation algorithm for star tracker based on optical flow techniques

NASA Astrophysics Data System (ADS)

Tang, Yujie; Li, Jian; Wang, Gangyi

2018-02-01

An integrated navigation system often uses the traditional gyro and star tracker for high precision navigation with the shortcomings of large volume, heavy weight and high-cost. With the development of autonomous navigation for deep space and small spacecraft, star tracker has been gradually used for attitude calculation and angular velocity measurement directly. At the same time, with the dynamic imaging requirements of remote sensing satellites and other imaging satellites, how to measure the angular velocity in the dynamic situation to improve the accuracy of the star tracker is the hotspot of future research. We propose the approach to measure angular rate with a nongyro and improve the dynamic performance of the star tracker. First, the star extraction algorithm based on morphology is used to extract the star region, and the stars in the two images are matched according to the method of angular distance voting. The calculation of the displacement of the star image is measured by the improved optical flow method. Finally, the triaxial angular velocity of the star tracker is calculated by the star vector using the least squares method. The method has the advantages of fast matching speed, strong antinoise ability, and good dynamic performance. The triaxial angular velocity of star tracker can be obtained accurately with these methods. So, the star tracker can achieve better tracking performance and dynamic attitude positioning accuracy to lay a good foundation for the wide application of various satellites and complex space missions.

Guaranteeing Pointing Performance of the SDO Sun-Pointing Controllers in Light of Nonlinear Effects

NASA Technical Reports Server (NTRS)

Starin, Scott R.; Bourkland, Kristin L.

2007-01-01

The Solar Dynamics Observatory (SDO) mission is the first Space Weather Research Network mission, part of NASA s Living With a Star program.1 This program seeks to understand the changing Sun and its effects on the Solar System, life, and society. To this end, the SDO spacecraft will carry three Sun-observing instruments to geosynchronous orbit: Helioseismic and Magnetic Imager (HMI), led by Stanford University; Atmospheric Imaging Assembly (AIA), led by Lockheed Martin Space and Astrophysics Laboratory; and Extreme Ultraviolet Variability Experiment (EVE), led by the University of Colorado. Links describing the instruments in detail may be found through the SDO web site.2 The basic mission goals are to observe the Sun for a very high percentage of the 5-year mission (10-year goal) with long stretches of uninterrupted observations and with constant, high-data-rate transmission to a dedicated ground station. These goals guided the design of the spacecraft bus that will carry and service the three-instrument payload. At the time of this publication, the SDO spacecraft bus is well into the integration and testing phase at the NASA Goddard Space Flight Center (GSFC). A three-axis stabilized attitude control system (ACS) is needed both to point at the Sun accurately and to keep the roll about the Sun vector correctly positioned. The ACS has four reaction wheel modes and 2 thruster actuated modes. More details about the ACS in general and the control modes in particular can be found in Refs. [3-6]. All four of SDO s wheel-actuated control modes involve Sun-pointing controllers, as might be expected from such a mission. Science mode, during which most science data is collected, uses specialized guide telescopes to point accurately at the Sun. Inertial mode has two sub-modes, one tracks a Sun-referenced target orientation, and another maintains an absolute (star-referenced) target orientation, that both employ a Kalman filter to process data from a digital Sun sensor and two star trackers. However, this paper is concerned only with the other two modes: Safe Hold (SH) and Sun Acquisition (SA).

Stargazing

NASA Astrophysics Data System (ADS)

Moore, Patrick

2000-10-01

On a clear night, the vastness and beauty of the star-filled sky is awe inspiring. In Stargazing: Astronomy without a Telescope Patrick Moore, Britain's best known astronomer, tells you all you need to know about the universe visible to the naked eye. With the aid of charts and illustrations, he explains how to "read" the stars, to know which constellations lie overhead, their trajectory throughout the seasons, and the legends ascribed to them. In a month-by-month guide he describes using detailed star maps of the night skies of both the northern and southern hemispheres. He also takes a look at the planets, the Sun and the Moon and their eclipses, comets, meteors, as well as aurorae and other celestial phenomena--all in accessible scientific detail. This captivating book shows how, even with just the naked eye, astronomy can be a fascinating and rewarding hobby--for life.

How star women build portable skills.

PubMed

Groysberg, Boris

2008-02-01

In May 2004, with the war for talent in high gear, Groysberg and colleagues from Harvard Business School wrote in these pages about the risks of hiring star performers away from competitors. After studying the fortunes of more than 1,000 star stock analysts, they found that when a star switched companies, not only did his performance plunge, so did the effectiveness of the group he joined and the market value of his new company. But further analysis of the data reveals that it's not that simple. In fact, one group of analysts reliably maintained star rankings even after changing employers: women. Unlike their male counterparts, female stars who switched firms performed just as well, in the aggregate, as those who stayed put. The 189 star women in the sample (18% of the star analysts studied) achieved a higher rank after switching firms than the men did. Why the discrepancy? First, says the author, the best female analysts appear to have built their franchises on portable, external relationships with clients and the companies they covered, rather than on relationships rooted within their firms. By contrast, male analysts built up greater firm- and team-specific human capital by investing more in the internal networks and unique capabilities and resources of their own companies. Second, women took greater care when assessing a prospective new employer. In this article, Groysberg explores the reasons behind the star women's portable performance.

User's guide to the Octopus computer network (the SHOC manual)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schneider, C.; Thompson, D.; Whitten, G.

1977-07-18

This guide explains how to enter, run, and debug programs on the Octopus network. It briefly describes the network's operation, and directs the reader to other documents for further information. It stresses those service programs that will be most useful in the long run; ''quick'' methods that have little flexibility are not discussed. The Octopus timesharing network gives the user access to four CDC 7600 computers, two CDC STAR computers, and a broad array of peripheral equipment, from any of 800 or so remote terminals. 16 figures, 7 tables.

User's guide to the Octopus computer network (the SHOC manual)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schneider, C.; Thompson, D.; Whitten, G.

1976-10-07

This guide explains how to enter, run, and debug programs on the Octopus network. It briefly describes the network's operation, and directs the reader to other documents for further information. It stresses those service programs that will be most useful in the long run; ''quick'' methods that have little flexibility are not discussed. The Octopus timesharing network gives the user access to four CDC 7600 computers, two CDC STAR computers, and a broad array of peripheral equipment, from any of 800 or so remote terminals. 8 figures, 4 tables.

User's guide to the Octopus computer network (the SHOC manual)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schneider, C.; Thompson, D.; Whitten, G.

1975-06-02

This guide explains how to enter, run, and debug programs on the Octopus network. It briefly describes the network's operation, and directs the reader to other documents for further information. It stresses those service programs that will be most useful in the long run; ''quick'' methods that have little flexibility are not discussed. The Octopus timesharing network gives the user access to four CDC 7600 computers and a broad array of peripheral equipment, from any of 800 remote terminals. Octopus will soon include the Laboratory's STAR-100 computers. 9 figures, 5 tables. (auth)

Deep coupling of star tracker and MEMS-gyro data under highly dynamic and long exposure conditions

NASA Astrophysics Data System (ADS)

Sun, Ting; Xing, Fei; You, Zheng; Wang, Xiaochu; Li, Bin

2014-08-01

Star trackers and gyroscopes are the two most widely used attitude measurement devices in spacecrafts. The star tracker is supposed to have the highest accuracy in stable conditions among different types of attitude measurement devices. In general, to detect faint stars and reduce the size of the star tracker, a method with long exposure time method is usually used. Thus, under dynamic conditions, smearing of the star image may appear and result in decreased accuracy or even failed extraction of the star spot. This may cause inaccuracies in attitude measurement. Gyros have relatively good dynamic performance and are usually used in combination with star trackers. However, current combination methods focus mainly on the data fusion of the output attitude data levels, which are inadequate for utilizing and processing internal blurred star image information. A method for tracking deep coupling stars and MEMS-gyro data is proposed in this work. The method achieves deep fusion at the star image level. First, dynamic star image processing is performed based on the angular velocity information of the MEMS-gyro. Signal-to-noise ratio (SNR) of the star spot could be improved, and extraction is achieved more effectively. Then, a prediction model for optimal estimation of the star spot position is obtained through the MEMS-gyro, and an extended Kalman filter is introduced. Meanwhile, the MEMS-gyro drift can be estimated and compensated though the proposed method. These enable the star tracker to achieve high star centroid determination accuracy under dynamic conditions. The MEMS-gyro drift can be corrected even when attitude data of the star tracker are unable to be solved and only one navigation star is captured in the field of view. Laboratory experiments were performed to verify the effectiveness of the proposed method and the whole system.

The dangers of being trigger-happy

NASA Astrophysics Data System (ADS)

Dale, J. E.; Haworth, T. J.; Bressert, E.

2015-06-01

We examine the evidence offered for triggered star formation against the backdrop provided by recent numerical simulations of feedback from massive stars at or below giant molecular cloud sizescales. We compile a catalogue of 67 observational papers, mostly published over the last decade, and examine the signposts most commonly used to infer the presence of triggered star formation. We then determine how well these signposts perform in a recent suite of hydrodynamic simulations of star formation including feedback from O-type stars performed by Dale et al. We find that none of the observational markers improve the chances of correctly identifying a given star as triggered by more than factors of 2 at most. This limits the fidelity of these techniques in interpreting star formation histories. We therefore urge caution in interpreting observations of star formation near feedback-driven structures in terms of triggering.

Modeling the early evolution of massive OB stars with an experimental wind routine. The first bi-stability jump and the angular momentum loss problem

NASA Astrophysics Data System (ADS)

Keszthelyi, Z.; Puls, J.; Wade, G. A.

2017-02-01

Context. Stellar evolution models of massive stars are very sensitive to the adopted mass-loss scheme. The magnitude and evolution of mass-loss rates significantly affect the main sequence evolution, and the properties of post-main sequence objects, including their rotational velocities. Aims: Driven by potential discrepancies between theoretically predicted and observationally derived mass-loss rates in the OB star range, we aim in particular to investigate the response to mass-loss rates that are lower than currently adopted, in parallel with the mass-loss behavior at the "first" bi-stability jump. Methods: We performed 1D hydrodynamical model calculations of single 20-60 M⊙ Galactic (Z = 0.014) stars where the effects of stellar winds are already significant in the main sequence phase. We have developed an experimental wind routine to examine the behavior and response of the models under the influence of different mass-loss rates. This observationally guided, simple and flexible wind routine is not a new mass-loss description but a useful tool based on the wind-momentum luminosity relation and other scaling relations, and provides a meaningful base for various tests and comparisons. Results: The main result of this study indicates a dichotomy between solutions of currently debated problems regarding mass-loss rates of hot massive stars. In a fully diffusive approach, and for commonly adopted initial rotational velocities, lower mass-loss rates than theoretically predicted require to invoke an additional source of angular momentum loss (either due to bi-stability braking, or yet unidentified) to brake down surface rotational velocities. On the other hand, a large jump in the mass-loss rates due to the bi-stability mechanism (a factor of 5-7 predicted by Vink et al. (2000, A&A, 362, 295), but a factor of 10-20 in modern models of massive stars) is challenged by observational results, and might be avoided if the early mass-loss rates agreed with the theoretically predicted values. Conclusions: We conclude that simultaneously adopting lower mass-loss rates and a significantly smaller jump in the mass-loss rates over the bi-stability region (both compared to presently used prescriptions) would require an additional mechanism for angular momentum loss to be present in massive stars. Otherwise, the observed rotational velocities of a large population of B supergiants, that are thought to be the evolutionary descendants of O stars, would remain unexplained.

A Question and Answer Guide to Astronomy

NASA Astrophysics Data System (ADS)

Christian, Carol; Roy, Jean-René

2017-03-01

Preface; 1. The sky viewed from Earth; 2. The Earth and Moon system; 3. The Solar System; 4. Stars and stellar systems; 5. Galaxies and the Universe; 6. Life in the Universe; 7. Amateur astronomy; 8. Telescopes and instruments; Unit conversion and basic physical and astronomical measurements; References; Bibliography; Index.

In the Wake of Our Ancestors.

ERIC Educational Resources Information Center

Low, Sam

2003-01-01

To understand and revive the ancient Hawaiian culture, the crew of a traditional Polynesian double-hulled voyaging canoe sails among the Pacific Islands without charts or instruments. Trained by Western science, elders, and experience, the navigator guides the craft by the stars and dead reckoning. Each voyage is linked to Hawaiian classroom…

Hawaii: Navigating a Different Way of Knowing.

ERIC Educational Resources Information Center

Thuermer, Kitty

1999-01-01

Seafarer Nainoa Thompson proved Western scientists wrong when they claimed his Pacific Island ancestors lacked the navigational skills to make their 2,500 mile trans-Pacific voyages, guided only by the stars and the sea. In the same way, schools must model different, more affiliative ways of gaining and imparting knowledge. (MLH)

Transformation reborn: A new generation expert system for planning HST operations

NASA Technical Reports Server (NTRS)

Gerb, Andrew

1991-01-01

The Transformation expert system (TRANS) converts proposals for astronomical observations with the Hubble Space Telescope (HST) into detailed observing plans. It encodes expert knowledge to solve problems faced in planning and commanding HST observations to enable their processing by the Science Operations Ground System (SOGS). Among these problems are determining an acceptable order of executing observations, grouping of observations to enhance efficiency and schedulability, inserting extra observations when necessary, and providing parameters for commanding HST instruments. TRANS is currently an operational system and plays a critical role in the HST ground system. It was originally designed using forward-chaining provided by the OPS5 expert system language, but has been reimplemented using a procedural knowledge base. This reimplementation was forced by the explosion in the amount of OPS5 code required to specify the increasingly complicated situations requiring expert-level intervention by the TRANS knowledge base. This problem was compounded by the difficulty of avoiding unintended interaction between rules. To support the TRANS knowledge base, XCL, a small but powerful extension to Commom Lisp was implemented. XCL allows a compact syntax for specifying assignments and references to object attributes. XCL also allows the capability to iterate over objects and perform keyed lookup. The reimplementation of TRANS has greatly diminished the effort needed to maintain and enhance it. As a result of this, its functions have been expanded to include warnings about observations that are difficult or impossible to schedule or command, providing data to aid SPIKE, an intelligent planning system used for HST long-term scheduling, and providing information to the Guide Star Selection System (GSSS) to aid in determination of the long range availability of guide stars.

Practical experience with test-driven development during commissioning of the multi-star AO system ARGOS

NASA Astrophysics Data System (ADS)

Kulas, M.; Borelli, Jose Luis; Gässler, Wolfgang; Peter, Diethard; Rabien, Sebastian; Orban de Xivry, Gilles; Busoni, Lorenzo; Bonaglia, Marco; Mazzoni, Tommaso; Rahmer, Gustavo

2014-07-01

Commissioning time for an instrument at an observatory is precious, especially the night time. Whenever astronomers come up with a software feature request or point out a software defect, the software engineers have the task to find a solution and implement it as fast as possible. In this project phase, the software engineers work under time pressure and stress to deliver a functional instrument control software (ICS). The shortness of development time during commissioning is a constraint for software engineering teams and applies to the ARGOS project as well. The goal of the ARGOS (Advanced Rayleigh guided Ground layer adaptive Optics System) project is the upgrade of the Large Binocular Telescope (LBT) with an adaptive optics (AO) system consisting of six Rayleigh laser guide stars and wavefront sensors. For developing the ICS, we used the technique Test- Driven Development (TDD) whose main rule demands that the programmer writes test code before production code. Thereby, TDD can yield a software system, that grows without defects and eases maintenance. Having applied TDD in a calm and relaxed environment like office and laboratory, the ARGOS team has profited from the benefits of TDD. Before the commissioning, we were worried that the time pressure in that tough project phase would force us to drop TDD because we would spend more time writing test code than it would be worth. Despite this concern at the beginning, we could keep TDD most of the time also in this project phase This report describes the practical application and performance of TDD including its benefits, limitations and problems during the ARGOS commissioning. Furthermore, it covers our experience with pair programming and continuous integration at the telescope.

The first US Naval Observatory CCD Astrograph Catalog

NASA Astrophysics Data System (ADS)

Germain, M. E.; Zacharias, N.; Urban, S. E.; Rafferty, T. J.; Holdenried, E. R.; Zacharias, M. I.; Hall, D. M.; Wycoff, G. L.; Monet, D. G.

2000-05-01

The USNO CCD Astrograph Catalog (UCAC) project is a high precision, astrometric survey of stars having R magnitudes between 7th and 16th. The positional accuracy is 20 mas for stars between 9th and 14th, and 70 mas for fainter stars. This gives a density (stars per square degree) higher than that of the Guide Star Catalog (GSC), with an improvement in positional accuracy of about a factor of ten. Observations began in January 1998 at Cerro Tololo Inter--American Observatory (CTIO) using a five-element 0.2 meter astrograph equipped with a 4k by 4k CCD. The instrument will be moved north in early 2001, and full sky coverage is expected by early 2003. A preliminary catalog (UCAC1) of positions and proper motions of 27 million stars has been constructed which is available on CD-ROM from USNO. Observations between 13 Feb 1998 and 07 Nov 1999 are included with a total of over 79,000 CCD frames covering 80% of the Southern Hemisphere. The catalog is on the International Celestial Reference System (ICRS), which is consistent with J2000. Proper motions of bright stars (V <= 12.5) were derived using a combination of ground-based astrometric catalogs, Hipparcos, and Tycho-2 positions, giving a typical error of 3 mas/yr. For the fainter stars the USNO A2.0 (Monet, 1998) was used as first epoch, with typical proper motion errors of 10 to 15 mas/yr. External comparisons with Tycho-2 and the Yale Southern Proper Motion (SPM) 2.0 data reveal systematic errors to be only on the 10 mas level.

Lucky imaging multiplicity studies of exoplanet host stars

NASA Astrophysics Data System (ADS)

Ginski, C.; Mugrauer, M.; Neuhäuser, R.

2014-03-01

The multiplicity of stars is an important parameter in order to understand star and planet formation. In the past decades extrasolar planets have been discovered around more than 600 stars with the radial velocity and transit techniques. Many of these systems present extreme cases of massive planetary objects at very close separations to their primary stars. To explain the configurations of such systems is hence a continued challenge in the development of formation theories. It will be very interesting to determine if there are significant differences between planets in single and multiple star systems. In our ongoing study we use high resolution imaging techniques to clarify the multiplicity status of nearby (within 250 pc) planet host stars. For targets on the northern hemisphere we employ the lucky imaging instrument Astralux at the 2.2 m telescope of the Calar Alto Observatory. The lucky imaging approach consists of taking several thousand short images with integration times shorter than the speckle coherence time, to sample the speckle variations during the observation window. We then only choose the so called "lucky shots" with a very high Strehl ratio in one of the speckles, to shift and add, resulting in a final image with the highest possible Strehl ratio and therefore highest possible angular resolution. We will present recent results of our study at the Calar Alto Observatory, as well as observations undertaken with the RTK camera at the 20 cm guiding telescope in our own observatory in Großschwabhausen.

A Three-dimensional Simulation of a Magnetized Accretion Disk: Fast Funnel Accretion onto a Weakly Magnetized Star

NASA Astrophysics Data System (ADS)

Takasao, Shinsuke; Tomida, Kengo; Iwasaki, Kazunari; Suzuki, Takeru K.

2018-04-01

We present the results of a global, three-dimensional magnetohydrodynamics simulation of an accretion disk with a rotating, weakly magnetized central star. The disk is threaded by a weak, large-scale poloidal magnetic field, and the central star has no strong stellar magnetosphere initially. Our simulation investigates the structure of the accretion flows from a turbulent accretion disk onto the star. The simulation reveals that fast accretion onto the star at high latitudes occurs even without a stellar magnetosphere. We find that the failed disk wind becomes the fast, high-latitude accretion as a result of angular momentum exchange mediated by magnetic fields well above the disk, where the Lorentz force that decelerates the rotational motion of gas can be comparable to the centrifugal force. Unlike the classical magnetospheric accretion scenario, fast accretion streams are not guided by magnetic fields of the stellar magnetosphere. Nevertheless, the accretion velocity reaches the free-fall velocity at the stellar surface due to the efficient angular momentum loss at a distant place from the star. This study provides a possible explanation why Herbig Ae/Be stars whose magnetic fields are generally not strong enough to form magnetospheres also show indications of fast accretion. A magnetically driven jet is not formed from the disk in our model. The differential rotation cannot generate sufficiently strong magnetic fields for the jet acceleration because the Parker instability interrupts the field amplification.

How Bell Labs creates star performers.

PubMed

Kelley, R; Caplan, J

1993-01-01

How can managers increase the productivity of professionals when most of their work goes on inside their heads? Robert Kelley and Janet Caplan believe that defining the difference between star performers and average workers is the answer. Many managers assume that top performers are just smarter. But the authors' research at the Bell Laboratories Switching Systems Business Unit (SSBU) has revealed that the real difference between stars and average workers is not IQ but the ways top performers do their jobs. Their study has led to a training program based on the strategies of star performers. The SSBU training program, known as the Productivity Enhancement Group (PEG), uses an expert model to demystify productivity. The star engineers selected to develop the expert model identified and ranked nine work strategies, such as taking initiative, networking, and self-management. Middle performers were also asked what makes for top-quality work, but their definitions and ranking of the strategies differed significantly from those of the top performers. Taking initiative, for example, meant something very different to an average worker than it did to a star. And for the middle performers, the ability to give good presentations was a core strategy, while it was peripheral for the top engineers. Once PEG got underway, respected engineers ran the training sessions, which included case studies, work-related exercises, and frank discussion. The benefits of the program were striking: participants and managers reported substantial productivity increases in both star and average performers. The PEG program may not be a blueprint for other companies, but its message is clear: managers must focus on people, not on technology, to increase productivity in the knowledge economy.

The performance of the MROI fast tip-tilt correction system

NASA Astrophysics Data System (ADS)

Young, John; Buscher, David; Fisher, Martin; Haniff, Christopher; Rea, Alexander; Seneta, Eugene; Sun, Xiaowei; Wilson, Donald; Farris, Allen; Olivares, Andres

2014-07-01

The fast tip-tilt (FTT) correction system for the Magdalena Ridge Observatory Interferometer (MROI) is being developed by the University of Cambridge. The design incorporates an EMCCD camera protected by a thermal enclosure, optical mounts with passive thermal compensation, and control software running under Xenomai real-time Linux. The complete FTT system is now undergoing laboratory testing prior to being installed on the first MROI unit telescope in the fall of 2014. We are following a twin-track approach to testing the closed-loop performance: tracking tip-tilt perturbations introduced by an actuated flat mirror in the laboratory, and undertaking end-to-end simulations that incorporate realistic higher-order atmospheric perturbations. We report test results that demonstrate (a) the high stability of the entire opto-mechanical system, realized with a completely passive design; and (b) the fast tip-tilt correction performance and limiting sensitivity. Our preliminary results in both areas are close to those needed to realise the ambitious stability and sensitivity goals of the MROI which aims to match the performance of current natural guide star adaptive optics systems.

Uprated fine guidance sensor study

NASA Technical Reports Server (NTRS)

1984-01-01

Future orbital observatories will require star trackers of extremely high precision. These sensors must maintain high pointing accuracy and pointing stability simultaneously with a low light level signal from a guide star. To establish the fine guidance sensing requirements and to evaluate candidate fine guidance sensing concepts, the Space Telescope Optical Telescope Assembly was used as the reference optical system. The requirements review was separated into three areas: Optical Telescope Assembly (OTA), Fine Guidance Sensing and astrometry. The results show that the detectors should be installed directly onto the focal surface presented by the optics. This would maximize throughput and minimize point stability error by not incoporating any additional optical elements.

Effective star tracking method based on optical flow analysis for star trackers.

PubMed

Sun, Ting; Xing, Fei; Wang, Xiaochu; Li, Jin; Wei, Minsong; You, Zheng

2016-12-20

Benefiting from rapid development of imaging sensor technology, modern optical technology, and a high-speed computing chip, the star tracker's accuracy, dynamic performance, and update rate have been greatly improved with low power consumption and miniature size. The star tracker is currently one of the most competitive attitude measurement sensors. However, due to restrictions of the optical imaging system, difficulties still exist in moving star spot detection and star tracking when in special motion conditions. An effective star tracking method based on optical flow analysis for star trackers is proposed in this paper. Spot-based optical flow, based on a gray gradient between two adjacent star images, is analyzed to distinguish the star spot region and obtain an accurate star spot position so that the star tracking can keep continuous under high dynamic conditions. The obtained star vectors and extended Kalman filter (EKF) are then combined to conduct an angular velocity estimation to ensure region prediction of the star spot; this can be combined with the optical flow analysis result. Experiment results show that the method proposed in this paper has advantages in conditions of large angular velocity and large angular acceleration, despite the presence of noise. Higher functional density and better performance can be achieved; thus, the star tracker can be more widely applied in small satellites, remote sensing, and other complex space missions.

Imaging Transitional Disks with TMT: Lessons Learned from the SEEDS Survey

NASA Technical Reports Server (NTRS)

Grady, Carol A.; Fukagawa, M.; Muto, T.; Hashimoto, J.

2014-01-01

TMT studies of the early phases of giant planet formation will build on studies carried out in this decade using 8-meter class telescopes. One such study is the Strategic Exploration of Exoplanets and Disks with Subaru transitional disk survey. We have found a wealth of indirect signatures of giant planet presence, including spiral arms, pericenter offsets of the outer disk from the star, and changes in disk color at the inner edge of the outer disk in intermediate-mass PMS star disks. T Tauri star transitional disks are less flamboyant, but are also dynamically colder: any spiral arms in these diskswill be more tightly wound. Imaging such features at the distance of the nearest star-forming regions requires higher angular resolution than achieved with HiCIAO+ AO188. Imaging such disks with extreme AO systems requires use of laser guide stars, and are infeasible with the extreme AO systems currently commissioning on 8-meter class telescopes. Similarly, the JWST and AFTAWFIRST coronagraphs being considered have inner working angles 0.2, and will occult the inner 28 atomic units of systems at d140pc, a region where both high-contrast imagery and ALMA data indicate that giant planets are located in transitional disks. However, studies of transitional disks associated with solar-mass stars and their planet complement are feasible with TMT using NFIRAOS.

YOUNG STELLAR POPULATIONS IN MYStIX STAR-FORMING REGIONS: CANDIDATE PROTOSTARS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Romine, Gregory; Feigelson, Eric D.; Getman, Konstantin V.

The Massive Young Star-Forming Complex in Infrared and X-ray (MYStIX) project provides a new census on stellar members of massive star-forming regions within 4 kpc. Here the MYStIX Infrared Excess catalog and Chandra -based X-ray photometric catalogs are mined to obtain high-quality samples of Class I protostars using criteria designed to reduce extragalactic and Galactic field star contamination. A total of 1109 MYStIX Candidate Protostars (MCPs) are found in 14 star-forming regions. Most are selected from protoplanetary disk infrared excess emission, but 20% are found from their ultrahard X-ray spectra from heavily absorbed magnetospheric flare emission. Two-thirds of the MCP sample ismore » newly reported here. The resulting samples are strongly spatially associated with molecular cores and filaments on Herschel far-infrared maps. This spatial agreement and other evidence indicate that the MCP sample has high reliability with relatively few “false positives” from contaminating populations. But the limited sensitivity and sparse overlap among the infrared and X-ray subsamples indicate that the sample is very incomplete with many “false negatives.” Maps, tables, and source descriptions are provided to guide further study of star formation in these regions. In particular, the nature of ultrahard X-ray protostellar candidates without known infrared counterparts needs to be elucidated.« less

A Daytime Aspect Camera for Balloon Altitudes

NASA Technical Reports Server (NTRS)

Dietz, Kurt L.; Ramsey, Brian D.; Alexander, Cheryl D.; Apple, Jeff A.; Ghosh, Kajal K.; Swift, Wesley R.; Six, N. Frank (Technical Monitor)

2001-01-01

We have designed, built, and flight-tested a new star camera for daytime guiding of pointed balloon-borne experiments at altitudes around 40km. The camera and lens are commercially available, off-the-shelf components, but require a custom-built baffle to reduce stray light, especially near the sunlit limb of the balloon. This new camera, which operates in the 600-1000 nm region of the spectrum, successfully provided daytime aspect information of approximately 10 arcsecond resolution for two distinct star fields near the galactic plane. The detected scattered-light backgrounds show good agreement with the Air Force MODTRAN models, but the daytime stellar magnitude limit was lower than expected due to dispersion of red light by the lens. Replacing the commercial lens with a custom-built lens should allow the system to track stars in any arbitrary area of the sky during the daytime.

Daytime Aspect Camera for Balloon Altitudes

NASA Technical Reports Server (NTRS)

Dietz, Kurt L.; Ramsey, Brian D.; Alexander, Cheryl D.; Apple, Jeff A.; Ghosh, Kajal K.; Swift, Wesley R.

2002-01-01

We have designed, built, and flight-tested a new star camera for daytime guiding of pointed balloon-borne experiments at altitudes around 40 km. The camera and lens are commercially available, off-the-shelf components, but require a custom-built baffle to reduce stray light, especially near the sunlit limb of the balloon. This new camera, which operates in the 600- to 1000-nm region of the spectrum, successfully provides daytime aspect information of approx. 10 arcsec resolution for two distinct star fields near the galactic plane. The detected scattered-light backgrounds show good agreement with the Air Force MODTRAN models used to design the camera, but the daytime stellar magnitude limit was lower than expected due to longitudinal chromatic aberration in the lens. Replacing the commercial lens with a custom-built lens should allow the system to track stars in any arbitrary area of the sky during the daytime.

An Extended Kalman Filter-Based Attitude Tracking Algorithm for Star Sensors

PubMed Central

Li, Jian; Wei, Xinguo; Zhang, Guangjun

2017-01-01

Efficiency and reliability are key issues when a star sensor operates in tracking mode. In the case of high attitude dynamics, the performance of existing attitude tracking algorithms degenerates rapidly. In this paper an extended Kalman filtering-based attitude tracking algorithm is presented. The star sensor is modeled as a nonlinear stochastic system with the state estimate providing the three degree-of-freedom attitude quaternion and angular velocity. The star positions in the star image are predicted and measured to estimate the optimal attitude. Furthermore, all the cataloged stars observed in the sensor field-of-view according the predicted image motion are accessed using a catalog partition table to speed up the tracking, called star mapping. Software simulation and night-sky experiment are performed to validate the efficiency and reliability of the proposed method. PMID:28825684

An Extended Kalman Filter-Based Attitude Tracking Algorithm for Star Sensors.

PubMed

Li, Jian; Wei, Xinguo; Zhang, Guangjun

2017-08-21

Efficiency and reliability are key issues when a star sensor operates in tracking mode. In the case of high attitude dynamics, the performance of existing attitude tracking algorithms degenerates rapidly. In this paper an extended Kalman filtering-based attitude tracking algorithm is presented. The star sensor is modeled as a nonlinear stochastic system with the state estimate providing the three degree-of-freedom attitude quaternion and angular velocity. The star positions in the star image are predicted and measured to estimate the optimal attitude. Furthermore, all the cataloged stars observed in the sensor field-of-view according the predicted image motion are accessed using a catalog partition table to speed up the tracking, called star mapping. Software simulation and night-sky experiment are performed to validate the efficiency and reliability of the proposed method.

Stargazing Basics

NASA Astrophysics Data System (ADS)

Kinzer, Paul E.

2015-07-01

Preface; Introduction: why another stargazing guide?; Part I. Stargazing Techniques and Equipment: 1. With the naked eye alone; 2. Binoculars: the next step; 3. 'But I want a telescope!'; Part II. What's up There?: 4. The Solar System; 5. The deep sky; Part III. A Stargazing Glossary: Appendix 1. The Greek alphabet; Appendix 2. The constellations; Some simple star charts; Index.

ASTRONOMY.

ERIC Educational Resources Information Center

Louisiana Arts and Science Center, Baton Rouge.

THIS TEACHER'S GUIDE FOR A UNIT ON ASTRONOMY ESTABLISHES (1) UNDERSTANDINGS AND ATTITUDES, (2) SKILLS, AND (3) CONCEPTS TO BE GAINED IN THE STUDY. THE OVERVIEW EXPLAINS THE ORGANIZATION AND OBJECTIVES OF THE UNIT. TOPICAL DIVISIONS ARE (1) THE EARTH, (2) THE MOON, (3) THE SUN, (4) THE SOLAR SYSTEM, (5) THE STARS, (6) THE UNIVERSE, AND (7) SPACE…

A Ground-based Sensor to Detect GEOs Without the Use of a Laser Guide-star

DTIC Science & Technology

2013-09-01

atmospheric turbulence generator to create atmospheric turbulence. The different Zernikes used in the experiment are focus, astigmatism , and coma...radian of astigmatism in the pupil plane are shown in figure 5. The top row shows actual data obtained with the telescope and the bottom row shows

Theater Battle Management Core System Systems Engineering Case Study

DTIC Science & Technology

2005-02-17

TOC Army Unit TOCs USMC TACC DASC Data Link Data Link AWACS J-STARS Data Link Data Link Data Link RIVET JOINT COMPASS CALL Theater RECCE/SURV Data...Developer’s Guide ( SDG ), Version 2, 30 August 2001. 11. Air Force Electronic Systems Center, ESC/ACF Program Office, ICWG Charter, November 2003. 12

Spatial interferometry in optical astronomy

NASA Technical Reports Server (NTRS)

Gezari, Daniel Y.; Roddier, Francois; Roddier, Claude

1990-01-01

A bibliographic guide is presented to publications of spatial interferometry techniques applied to optical astronomy. Listings appear in alphabetical order, by first author, as well as in specific subject categories listed in chronological order, including imaging theory and speckle interferometry, experimental techniques, and observational results of astronomical studies of stars, the Sun, and the solar system.

A Comparison of Value-Added, Ordinary Least Squares Regression, and the California STAR Accountability Indicators

ERIC Educational Resources Information Center

Black, Aime

2012-01-01

Student achievement to reward or sanction schools. These unadjusted accountability indicators do not account for differences in student or school characteristics that contribute to variations in assessment results. Since the "Coleman Report" (1966), a guiding principle in accountability design has been that educational outcomes data…

Prototype of a laser guide star wavefront sensor for the Extremely Large Telescope

NASA Astrophysics Data System (ADS)

Patti, M.; Lombini, M.; Schreiber, L.; Bregoli, G.; Arcidiacono, C.; Cosentino, G.; Diolaiti, E.; Foppiani, I.

2018-06-01

The new class of large telescopes, like the future Extremely Large Telescope (ELT), are designed to work with a laser guide star (LGS) tuned to a resonance of atmospheric sodium atoms. This wavefront sensing technique presents complex issues when applied to big telescopes for many reasons, mainly linked to the finite distance of the LGS, the launching angle, tip-tilt indetermination and focus anisoplanatism. The implementation of a laboratory prototype for the LGS wavefront sensor (WFS) at the beginning of the phase study of MAORY (Multi-conjugate Adaptive Optics Relay) for ELT first light has been indispensable in investigating specific mitigation strategies for the LGS WFS issues. This paper presents the test results of the LGS WFS prototype under different working conditions. The accuracy within which the LGS images are generated on the Shack-Hartmann WFS has been cross-checked with the MAORY simulation code. The experiments show the effect of noise on centroiding precision, the impact of LGS image truncation on wavefront sensing accuracy as well as the temporal evolution of the sodium density profile and LGS image under-sampling.

STS-88 Mission Insignia

NASA Technical Reports Server (NTRS)

1998-01-01

Designed by the STS-88 crew members, this patch commemorates the first assembly flight to carry United States-built hardware for constructing the International Space Station (ISS). This flight's primary task was to assemble the cornerstone of the Space Station: the Node with the Functional Cargo Block (FGB). The rising sun symbolizes the dawning of a new era of international cooperation in space and the beginning of a new program: the International Space Station. The Earth scene outlines the countries of the Station Partners: the United States, Russia, those of the European Space Agency (ESA), Japan, and Canada. Along with the Pressurized Mating Adapters (PMA) and the Functional Cargo Block, the Node is shown in the final mated configuration while berthed to the Space Shuttle during the STS-88/2A mission. The Big Dipper Constellation points the way to the North Star, a guiding light for pioneers and explorers for generations. In the words of the crew, These stars symbolize the efforts of everyone, including all the countries involved in the design and construction of the International Space Station, guiding us into the future.

International Space Station (ISS)

NASA Image and Video Library

1998-11-08

Designed by the STS-88 crew members, this patch commemorates the first assembly flight to carry United States-built hardware for constructing the International Space Station (ISS). This flight's primary task was to assemble the cornerstone of the Space Station: the Node with the Functional Cargo Block (FGB). The rising sun symbolizes the dawning of a new era of international cooperation in space and the beginning of a new program: the International Space Station. The Earth scene outlines the countries of the Station Partners: the United States, Russia, those of the European Space Agency (ESA), Japan, and Canada. Along with the Pressurized Mating Adapters (PMA) and the Functional Cargo Block, the Node is shown in the final mated configuration while berthed to the Space Shuttle during the STS-88/2A mission. The Big Dipper Constellation points the way to the North Star, a guiding light for pioneers and explorers for generations. In the words of the crew, These stars symbolize the efforts of everyone, including all the countries involved in the design and construction of the International Space Station, guiding us into the future.

KAPAO-Alpha: An On-The-Sky Testbed for Adaptive Optics on Small Aperture Telescopes

NASA Astrophysics Data System (ADS)

Morrison, Will; Choi, P. I.; Severson, S. A.; Spjut, E.; Contreras, D. S.; Gilbreth, B. N.; McGonigle, L. P.; Rudy, A. R.; Xue, A.; Baranec, C.; Riddle, R.

2012-05-01

We present initial in-lab and on-sky results of a natural guide star adaptive optics instrument, KAPAO-Alpha, being deployed on Pomona College’s 1-meter telescope at Table Mountain Observatory. The instrument is an engineering prototype designed to help us identify and solve design and integration issues before building KAPAO, a low-cost, dual-band, natural guide star AO system currently in active development and scheduled for first light in 2013. The Alpha system operates at visible wavelengths, employs Shack-Hartmann wavefront sensing, and is assembled entirely from commercially available components that include: off-the-shelf optics, a 140-actuator BMC deformable mirror, a high speed SciMeasure Lil’ Joe camera, and an EMCCD for science image acquisition. Wavefront reconstruction operating at 1-kHz speeds is handled with a consumer-grade computer running custom software adopted from the Robo-AO project. The assembly and integration of the Alpha instrument has been undertaken as a Pomona College undergraduate thesis. As part of the larger KAPAO project, it is supported by the National Science Foundation under Grant No. 0960343.

Design of an holographic off-axis calibration light source for ARGOS at the LBT

NASA Astrophysics Data System (ADS)

Schwab, Christian; Gassler, Wolfgang; Peter, Diethard; Blumchen, Thomas; Aigner, Simon; Quirrenbach, Andreas

We report on the design of an artificial light source for ARGOS, the multiple Rayleigh laser guide star (LGS) facility at the Large Binocular Telescope (LBT). Our light source mimics the expected night-time illumination of the adaptive secondary mirror (ASM) by the laser beacons very accurately and provides a way to check the achieved performance, allowing thorough testing of the system during day time. The optical design makes use of computer generated holograms (CGH) and strong aspheres to achieve a very small residual wavefront error. Additional structures on the CGH facilitate quick and precise alignment of the optics in the prime focus. We demonstrate that the scheme can be applied to the current European Extremely Large Telescope (E-ELT) design in a similar way.

Star centroiding error compensation for intensified star sensors.

PubMed

Jiang, Jie; Xiong, Kun; Yu, Wenbo; Yan, Jinyun; Zhang, Guangjun

2016-12-26

A star sensor provides high-precision attitude information by capturing a stellar image; however, the traditional star sensor has poor dynamic performance, which is attributed to its low sensitivity. Regarding the intensified star sensor, the image intensifier is utilized to improve the sensitivity, thereby further improving the dynamic performance of the star sensor. However, the introduction of image intensifier results in star centroiding accuracy decrease, further influencing the attitude measurement precision of the star sensor. A star centroiding error compensation method for intensified star sensors is proposed in this paper to reduce the influences. First, the imaging model of the intensified detector, which includes the deformation parameter of the optical fiber panel, is established based on the orthographic projection through the analysis of errors introduced by the image intensifier. Thereafter, the position errors at the target points based on the model are obtained by using the Levenberg-Marquardt (LM) optimization method. Last, the nearest trigonometric interpolation method is presented to compensate for the arbitrary centroiding error of the image plane. Laboratory calibration result and night sky experiment result show that the compensation method effectively eliminates the error introduced by the image intensifier, thus remarkably improving the precision of the intensified star sensors.

Effect of Iris registration on visual outcome in wavefront-guided LASEK for myopic astigmatism.

PubMed

Lee, Jong Joo; Kim, Mee Kum; Wee, Won Ryang

2018-04-01

This study aimed to investigate the effect of iris registration (IR) on visual outcomes in wavefront-guided LASEK for myopic astigmatism. The retrospective chart review was performed for wavefront-guided LASEK using VISX Star S4 in patients with myopic astigmatism (cylinder ≥ 1.00 diopter[D]). Eyes were divided into IR group (LASEK with IR at the time of surgery) and Non-IR group (LASEK without IR system + failed-IR engagement during LASEK). Visual acuity (VA), astigmatism, higher-order aberration (HOA), and contrast sensitivity were assessed preoperatively and 3 months postoperatively. The IR and Non-IR groups were subcategorized depending on the spherical equivalent (lower myopia ≤-5.00 D vs. higher myopia >-5.00 D) for the comparison of HOA changes. Postoperative uncorrected VAs showed no differences between IR (n = 30) and Non-IR (n = 46). In astigmatic vector analyses, no differences were noted in the mean magnitude of error and the mean angle of error between two groups. There were no differences in postoperative total HOA, spherical aberration (SA), coma, and trefoil between the groups, either. The total HOA and SA increased in both groups, while coma increased only in Non-IR. In higher myopia, ΔRMS of coma was smaller in IR. Preoperative and postoperative total HOA were linearly correlated in Non-IR, but not for IR. Contrast sensitivity of 12 cycles per degree improved in both groups. IR had similar outcomes to conventional trackers in wavefront-guided LASEK, with less tendency of inducing coma, especially in higher myopia.

A near-infrared interferometric survey of debris-disc stars. VI. Extending the exozodiacal light survey with CHARA/JouFLU

NASA Astrophysics Data System (ADS)

Nuñez, P. D.; Scott, N. J.; Mennesson, B.; Absil, O.; Augereau, J.-C.; Bryden, G.; ten Brummelaar, T.; Ertel, S.; Coudé du Foresto, V.; Ridgway, S. T.; Sturmann, J.; Sturmann, L.; Turner, N. J.; Turner, N. H.

2017-12-01

We report the results of high-angular-resolution observations that search for exozodiacal light in a sample of main sequence stars and sub-giants. Using the "jouvence" of the fiber linked unit for optical recombination (JouFLU) at the center for high angular resolution astronomy (CHARA) telescope array, we have observed a total of 44 stars. Out of the 44 stars, 33 are new stars added to the initial, previously published survey of 42 stars performed at CHARA with the fiber linked unit for optical recombination (FLUOR). Since the start of the survey extension, we have detected a K-band circumstellar excess for six new stars at the 1% level or higher, four of which are known or candidate binaries, and two for which the excess could be attributed to exozodiacal dust. We have also performed follow-up observations of 11 of the stars observed in the previously published survey and found generally consistent results. We do however detect a significantly larger excess on three of these follow-up targets: Altair, υ And and κ CrB. Interestingly, the last two are known exoplanet host stars. We perform a statistical analysis of the JouFLU and FLUOR samples combined, which yields an overall exozodi detection rate of . We also find that the K-band excess in FGK-type stars correlates with the existence of an outer reservoir of cold (≲100 K) dust at the 99% confidence level, while the same cannot be said for A-type stars.

Building corporate character. Interview by Nan Stone.

PubMed

Hiatt, A

1992-01-01

Stride Rite is a good company by any definition: Keds, Sperry Top-Siders, and Stride Rite children's shoes are consumer favorites for their fit, quality, and comfort. Wall Street analysts praise the company's outstanding financial performance. Innovative programs such as the first corporate child-care center and public service scholarships support Stride Rite's reputation as one of the most responsible employers and corporate citizens in the United States. Behind Stride Rite's good performance are the building blocks of corporate character: a legacy of quality and service and a leader committed to keeping that legacy lively. When Stride Rite shipped its first children's shoes in 1919, they came with the company's commitment "to produce an honest quality product in an honest way and deliver it as promised." For Arnold Hiatt, that commitment has been the driving force behind the company's evolution from manufacturing into marketing and product development as well as the guiding principle in its relations with consumers, dealers, suppliers, and employees. But Stride Rite's corporate character is also a reflection of Hiatt himself. In his early 20s, Hiatt fled a management training program "designed to make carnivores" out of its new employees and bought Blue Star Shoes, a small manufacturing company that had gone into Chapter 11. Through experience and "stumbling around," he built Blue Star's sales to $5 million-and got a practical education in management, markets, and human nature that has proved equally useful in running Stride Rite.

Predictive modeling of treatment resistant depression using data from STAR*D and an independent clinical study.

PubMed

Nie, Zhi; Vairavan, Srinivasan; Narayan, Vaibhav A; Ye, Jieping; Li, Qingqin S

2018-01-01

Identification of risk factors of treatment resistance may be useful to guide treatment selection, avoid inefficient trial-and-error, and improve major depressive disorder (MDD) care. We extended the work in predictive modeling of treatment resistant depression (TRD) via partition of the data from the Sequenced Treatment Alternatives to Relieve Depression (STAR*D) cohort into a training and a testing dataset. We also included data from a small yet completely independent cohort RIS-INT-93 as an external test dataset. We used features from enrollment and level 1 treatment (up to week 2 response only) of STAR*D to explore the feature space comprehensively and applied machine learning methods to model TRD outcome at level 2. For TRD defined using QIDS-C16 remission criteria, multiple machine learning models were internally cross-validated in the STAR*D training dataset and externally validated in both the STAR*D testing dataset and RIS-INT-93 independent dataset with an area under the receiver operating characteristic curve (AUC) of 0.70-0.78 and 0.72-0.77, respectively. The upper bound for the AUC achievable with the full set of features could be as high as 0.78 in the STAR*D testing dataset. Model developed using top 30 features identified using feature selection technique (k-means clustering followed by χ2 test) achieved an AUC of 0.77 in the STAR*D testing dataset. In addition, the model developed using overlapping features between STAR*D and RIS-INT-93, achieved an AUC of > 0.70 in both the STAR*D testing and RIS-INT-93 datasets. Among all the features explored in STAR*D and RIS-INT-93 datasets, the most important feature was early or initial treatment response or symptom severity at week 2. These results indicate that prediction of TRD prior to undergoing a second round of antidepressant treatment could be feasible even in the absence of biomarker data.

New numerical determination of habitability in the Galaxy: the SETI connection

NASA Astrophysics Data System (ADS)

Ramirez, Rodrigo; Gómez-Muñoz, Marco A.; Vázquez, Roberto; Núñez, Patricia G.

2018-01-01

In this paper, we determine the habitability of Sun-like stars in the Galaxy using Monte Carlo simulations, which are guided by the factors of the Drake Equation for the considerations on the astrophysical and biological parameters needed to generate and maintain life on a planet's surface. We used a simple star distribution, initial mass function and star formation history to reproduce the properties and distribution of stars within the Galaxy. Using updated exoplanet data from the Kepler mission, we assign planets to some of the stars, and then follow the evolution of life on the planets that met the habitability criteria using two different civilization hypotheses. We predict that around 51% of Earth-like planets in the habitable zone (HZ) are inhabited by primitive life and 4% by technological life. We apply the results to the Kepler field of view, and predicted that there should be at least six Earth-like planets in the HZ, three of them inhabited by primitive life. According to our model, non-technological life is very common if there are the right conditions, but communicative civilizations are less likely to exist and detect. Nonetheless, we predict a considerable number of detectable civilizations within our Galaxy, making it worthwhile to keep searching.

The “UV-route” to Search for Blue Straggler Stars in Globular Clusters: First Results from the HST UV Legacy Survey

DOE Office of Scientific and Technical Information (OSTI.GOV)

Raso, S.; Ferraro, F. R.; Lanzoni, B.

We used data from the Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters to select the Blue Straggler Star (BSS) population in four intermediate/high density systems (namely NGC 2808, NGC 6388, NGC 6541, and NGC 7078) through a “UV-guided search.” This procedure consists of using the F275W images in each cluster to construct the master list of detected sources, and then force it to the images acquired in the other filters. Such an approach optimizes the detection of relatively hot stars and allows the detection of a complete sample of BSSs even in the central region of high-densitymore » clusters, because the light from the bright cool giants, which dominates the optical emission in old stellar systems, is sensibly reduced at UV wavelengths. Our UV-guided selections of BSSs have been compared to the samples obtained in previous, optical-driven surveys, clearly demonstrating the efficiency of the UV approach. In each cluster we also measured the parameter A {sup +}, defined as the area enclosed between the cumulative radial distribution of BSSs and that of a reference population, which traces the level of BSS central segregation and the level of dynamical evolution suffered by the system. The values measured for the four clusters studied in this paper nicely fall along the dynamical sequence recently presented for a sample of 25 clusters.« less

Four new Delta Scuti stars

NASA Technical Reports Server (NTRS)

Schutt, R. L.

1991-01-01

Four new Delta Scuti stars are reported. Power, modified into amplitude, spectra, and light curves are used to determine periodicities. A complete frequency analysis is not performed due to the lack of a sufficient time base in the data. These new variables help verify the many predictions that Delta Scuti stars probably exist in prolific numbers as small amplitude variables. Two of these stars, HR 4344 and HD 107513, are possibly Am stars. If so, they are among the minority of variable stars which are also Am stars.

CosmoQuest: Virtual Star Parties as a Conduit to Citizen Science Research

NASA Astrophysics Data System (ADS)

Lewis, Scott; Gugliucci, N. E.; Gay, P. L.; Amateur Astronomer Team; Commentator Team

2013-01-01

CosmoQuest has created an environment that actively engages the public through online star parties while building a growing virtual research center that allows individuals anywhere in the world to participate in and contribute to scientific research. Utilizing the infrastructure of Google+ and YouTube, CosmoQuest has brought optical observational astronomy into homes across the world. Every week astronomers - amateur and professional - meet to share live sky images and to discuss the science behind their beauty during Virtual Star parties. A wide array of optics and digital detectors from varied locations collaborate in a fashion not possible in the standard public star party. Every viewer is able to virtually look through the imaging telescope simultaneously while the equipment owner doesn’t need to worry about accidental mishandling by the public. Digital cameras and CCDs also allow longer exposures of deep-sky objects, something not typical in a standard star party event. Our diversity of equipment - ranging from hand-guided Dobsonian telescopes to 16” Schmidt-Cassegrain telescopes on Paramounts - give viewers the opportunity to experience the sky through different systems. Additional Star Parties focus on special astronomical events, such as eclipses and transits. The annular eclipse of 20 May, 2012 brought together astronomers, space enthusiasts and a curious public into a Google+ Hangout On Air to celebrate the event while advocating safe observing methods and explaining the science behind the phenomenon. Public photos of the eclipse were shared live in the broadcast while video of the event was streamed for thousands of viewers to enjoy. Other special event star parties have focused on the Super Moon, Eros Opposition, and the Venus Transit. In this poster we review the technology behind star parties and the reach of these events.

Education And Public Outreach For NASA's EPOXI Mission

NASA Astrophysics Data System (ADS)

McFadden, Lucy-Ann A.; Warner, E. M.; Crow, C. A.; Ristvey, J. D.; Counley, J.

2008-09-01

NASA's EPOXI mission has two scientific objectives in using the Deep Impact flyby spacecraft for further studies of comets and adding studies of extra-solar planets around other stars. During the Extrasolar Planetary Observations and Characterization (EPOCh) phase of the mission, observations of extrasolar planets transiting their parent stars are observed to further knowledge and understanding of planetary systems. Observations of Earth allow for comparison with Earth-like planets around other stars. A movie of Earth during a day when the Moon passed between Earth and the spacecraft is an educational highlight with scientific significance. The Deep Impact Extended Investigation (DIXI) continues the Deep Impact theme of investigating comets with a flyby of comet Hartley 2 in November 2010 to further explore the properties of comets and their formation. The EPOXI Education and Public Outreach (E/PO) program builds upon existing materials related to exploring comets and the Deep Impact mission, updating and modifying activities based on results from Deep Impact. An educational activity called Comparing Comets is under development that will guide students in conducting analyses similar to those that DIXI scientists will perform after observing comet Hartley 2. Existing educational materials related to planet finding from other NASA programs are linked from EPOXI's web page. Journey Through the Universe at the National Air and Space Museum encourages education in family and community groups and reaches out to underrepresented minorities. EPOXI's E/PO program additionally offers a newsletter to keep the public, teachers, and space enthusiasts apprised of mission activities. For more information visit: http://epoxi.umd.edu.

Autonomous star tracker based on active pixel sensors (APS)

NASA Astrophysics Data System (ADS)

Schmidt, U.

2017-11-01

Star trackers are opto-electronic sensors used onboard of satellites for the autonomous inertial attitude determination. During the last years, star trackers became more and more important in the field of the attitude and orbit control system (AOCS) sensors. High performance star trackers are based up today on charge coupled device (CCD) optical camera heads. The Jena-Optronik GmbH is active in the field of opto-electronic sensors like star trackers since the early 80-ties. Today, with the product family ASTRO5, ASTRO10 and ASTRO15, all marked segments like earth observation, scientific applications and geo-telecom are supplied to European and Overseas customers. A new generation of star trackers can be designed based on the APS detector technical features. The measurement performance of the current CCD based star trackers can be maintained, the star tracker functionality, reliability and robustness can be increased while the unit costs are saved.

Impact of star performance ratings in English acute hospital trusts.

PubMed

Mannion, Russell; Davies, Huw; Marshall, Martin

2005-01-01

To explore some of the impacts of star performance ratings in acute hospital trusts in England. A multiple case study design was used which incorporated purposeful sampling of 'low' and 'high' performing trusts using the star rating system. In each case study site, data collection comprised semi-structured interviews and documentary analysis. Between eight and 12 senior managers and senior clinicians were interviewed in each organisation. There was a general view that the star ratings as presently constituted did not represent a rounded or balanced scorecard of their own organisation's performance and a widespread belief that the information used to calculate the ratings was often incomplete and inaccurate. The star ratings were viewed by some managers as useful, in that they gave added weight to their trust's modernisation agenda. In addition to driving beneficial change, the ratings were also sometimes reported to have inadvertently induced a range of unintended and dysfunctional consequences, including tunnel vision and a distortion of clinical priorities, bullying and intimidation, erosion of public trust and reduced staff morale, and ghettoisation. Set in the context of an international body of research, this study highlights some important gaps in knowledge and failings in current policy and practice. In particular, the many dysfunctional consequences of publishing star ratings indicate a need for a re-examination of performance management policies.

Dynamic imaging model and parameter optimization for a star tracker.

PubMed

Yan, Jinyun; Jiang, Jie; Zhang, Guangjun

2016-03-21

Under dynamic conditions, star spots move across the image plane of a star tracker and form a smeared star image. This smearing effect increases errors in star position estimation and degrades attitude accuracy. First, an analytical energy distribution model of a smeared star spot is established based on a line segment spread function because the dynamic imaging process of a star tracker is equivalent to the static imaging process of linear light sources. The proposed model, which has a clear physical meaning, explicitly reflects the key parameters of the imaging process, including incident flux, exposure time, velocity of a star spot in an image plane, and Gaussian radius. Furthermore, an analytical expression of the centroiding error of the smeared star spot is derived using the proposed model. An accurate and comprehensive evaluation of centroiding accuracy is obtained based on the expression. Moreover, analytical solutions of the optimal parameters are derived to achieve the best performance in centroid estimation. Finally, we perform numerical simulations and a night sky experiment to validate the correctness of the dynamic imaging model, the centroiding error expression, and the optimal parameters.

Star sightings by satellite for image navigation

NASA Technical Reports Server (NTRS)

Kamel, Ahmed A. (Inventor); Ekman, Donald E. (Inventor); Savides, John (Inventor); Zwirn, Gerald J. (Inventor)

1988-01-01

Stars are sensed by one or more instruments (1, 2) on board a three-axis stabilized satellite, for purposes of assisting in image navigation. A star acquistion computer (64), which may be located on the earth, commands the instrument mirror (33, 32) to slew just outside the limb of the earth or other celestial body around which the satellite is orbiting, to look for stars that have been cataloged in a star map stored within the computer (64). The instrument (1, 2) is commanded to dwell for a period of time equal to a star search window time, plus the maximum time the instrument (1, 2) takes to complete a current scan, plus the maximum time it takes for the mirror (33, 32) to slew to the star. When the satellite is first placed in orbit, and following first stationkeeping and eclipse, a special operation is performed in which the star-seeking instrument (1, 2) FOV is broadened. The elevation dimension can be broadened by performing repetitive star seeks; the azimuth dimension can be broadened by lengthening the commanded dwell times.

Smearing model and restoration of star image under conditions of variable angular velocity and long exposure time.

PubMed

Sun, Ting; Xing, Fei; You, Zheng; Wang, Xiaochu; Li, Bin

2014-03-10

The star tracker is one of the most promising attitude measurement devices widely used in spacecraft for its high accuracy. High dynamic performance is becoming its major restriction, and requires immediate focus and promotion. A star image restoration approach based on the motion degradation model of variable angular velocity is proposed in this paper. This method can overcome the problem of energy dispersion and signal to noise ratio (SNR) decrease resulting from the smearing of the star spot, thus preventing failed extraction and decreased star centroid accuracy. Simulations and laboratory experiments are conducted to verify the proposed methods. The restoration results demonstrate that the described method can recover the star spot from a long motion trail to the shape of Gaussian distribution under the conditions of variable angular velocity and long exposure time. The energy of the star spot can be concentrated to ensure high SNR and high position accuracy. These features are crucial to the subsequent star extraction and the whole performance of the star tracker.

Photometric detection of a candidate low-mass giant binary system at the Milky Way Galactic Center

NASA Astrophysics Data System (ADS)

Krishna Gautam, Abhimat; Do, Tuan; Ghez, Andrea; Sakai, Shoko; Morris, Mark; Lu, Jessica; Witzel, Gunther; Jia, Siyao; Becklin, Eric Eric; Matthews, Keith

2018-01-01

We present the discovery of a new periodic variable star at the Milky Way Galactic Center (GC). This study uses laser guide-star adaptive optics data collected with the W. M. Keck 10 m telescope in the K‧-band (2.2 µm) over 35 nights spanning an 11 year time baseline, and 5 nights of additional H-band (1.6 µm) data. We implemented an iterative photometric calibration and local correction technique, resulting in a photometric uncertainty of Δm_K‧ ∼ 0.03 to a magnitude of m_K‧ ∼ 16.The periodically variable star has a 39.42 day period. We find that the star is not consistent with known periodically variable star classes in this period range with its observed color and luminosity, nor with an eclipsing binary system. The star's color and luminosity are however consistent with an ellipsoidal binary system at the GC, consisting of a K-giant and a dwarf component with an orbital period of 78.84 days. If a binary system, it represents the first detection of a low-mass giant binary system in the central half parsec of the GC. Such long-period binary systems can easily evaporate in the dense environment of the GC due to interactions with other stars. The existence and properties of a low-mass, long-period binary system can thus place valuable constraints on dynamical models of the GC environment and probe the density of the hypothesized dark cusp of stellar remnants at the GC.

The risky business of hiring stars.

PubMed

Groysberg, Boris; Nanda, Ashish; Nohria, Nitin

2004-05-01

With the battle for the best and brightest people heating up again, you're most likely out there looking for first-rate talent in the ranks of your competitors. Chances are, you're sold on the idea of recruiting from outside your organization, since developing people within the firm takes time and money. But the authors, who have tracked the careers of high-flying CEOs, researchers, software developers, and leading professionals, argue that top performers quickly fade after leaving one company for another. To study this phenomenon in greater detail, the authors analyzed the ups and downs of more than 1,000 star stock analysts, a well-defined group for which there are abundant data. The results were striking. After a star moves, not only does her performance plunge, but so does the effectiveness of the group she joins--and the market value of her new company. Moreover, transplanted stars don't stay with their new organizations for long, despite the astronomical salaries firms pay to lure them from rivals. Most companies that hire stars overlook the fact that an executive's performance is not entirely transferable because his personal competencies inevitably include company-specific skills. When the star leaves the old company for the new, he cannot take with him many of the resources that contributed to his achievements. As a result, he is unable to repeat his performance in another company--at least not until he learns to work the new system, which could take years. The authors conclude that companies cannot gain a competitive advantage or successfully grow by hiring stars from outside. Instead, they should focus on cultivating talent from within and do everything possible to retain the stars they create. Firms shouldn't fight the star wars, because winning could be the worst thing that happens to them.

KSC-2011-1910

NASA Image and Video Library

2011-02-28

CAPE CANAVERAL, Fla. -- The left spent booster used during space shuttle Discovery's final launch is guided into a hoisting slip at the Solid Rocket Booster Disassembly Facility at Hangar AF on Cape Canaveral Air Force Station in Florida. The shuttle's two solid rocket booster casings and associated flight hardware are recovered in the Atlantic Ocean after every launch by Freedom Star and Liberty Star. The boosters impact the Atlantic about seven minutes after liftoff and the retrieval ships are stationed about 10 miles from the impact area at the time of splashdown. After the spent segments are processed, they will be transported to Utah, where they will be refurbished and stored, if needed. Photo credit: NASA/Jim Grossmann

KSC-2011-1912

NASA Image and Video Library

2011-02-28

CAPE CANAVERAL, Fla. -- The left spent booster used during space shuttle Discovery's final launch is guided into a hoisting slip at the Solid Rocket Booster Disassembly Facility at Hangar AF on Cape Canaveral Air Force Station in Florida. The shuttle's two solid rocket booster casings and associated flight hardware are recovered in the Atlantic Ocean after every launch by Freedom Star and Liberty Star. The boosters impact the Atlantic about seven minutes after liftoff and the retrieval ships are stationed about 10 miles from the impact area at the time of splashdown. After the spent segments are processed, they will be transported to Utah, where they will be refurbished and stored, if needed. Photo credit: NASA/Jim Grossmann

KSC-2011-1913

NASA Image and Video Library

2011-02-28

CAPE CANAVERAL, Fla. -- Workers in a small raft, guide the left spent booster used during space shuttle Discovery's final launch into position in a hoisting slip at the Solid Rocket Booster Disassembly Facility at Hangar AF on Cape Canaveral Air Force Station in Florida. The shuttle's two solid rocket booster casings and associated flight hardware are recovered in the Atlantic Ocean after every launch by Freedom Star and Liberty Star. The boosters impact the Atlantic about seven minutes after liftoff and the retrieval ships are stationed about 10 miles from the impact area at the time of splashdown. After the spent segments are processed, they will be transported to Utah, where they will be refurbished and stored, if needed. Photo credit: NASA/Jim Grossmann

Photon collider: a four-channel autoguider solution

NASA Astrophysics Data System (ADS)

Hygelund, John C.; Haynes, Rachel; Burleson, Ben; Fulton, Benjamin J.

2010-07-01

The "Photon Collider" uses a compact array of four off axis autoguider cameras positioned with independent filtering and focus. The photon collider is two way symmetric and robustly mounted with the off axis light crossing the science field which allows the compact single frame construction to have extremely small relative deflections between guide and science CCDs. The photon collider provides four independent guiding signals with a total of 15 square arc minutes of sky coverage. These signals allow for simultaneous altitude, azimuth, field rotation and focus guiding. Guide cameras read out without exposure overhead increasing the tracking cadence. The independent focus allows the photon collider to maintain in focus guide stars when the main science camera is taking defocused exposures as well as track for telescope focus changes. Independent filters allow auto guiding in the science camera wavelength bandpass. The four cameras are controlled with a custom web services interface from a single Linux based industrial PC, and the autoguider mechanism and telemetry is built around a uCLinux based Analog Devices BlackFin embedded microprocessor. Off axis light is corrected with a custom meniscus correcting lens. Guide CCDs are cooled with ethylene glycol with an advanced leak detection system. The photon collider was built for use on Las Cumbres Observatory's 2 meter Faulks telescopes and currently used to guide the alt-az mount.

Guided by a Red Star: The Cuban Literacy Campaign and the Challenge of History

ERIC Educational Resources Information Center

McLaren, Peter

2009-01-01

This article features the book "Rebel Literacy: Cuba's National Literacy Campaign and Critical Global Citizenship," by Mark Abendroth, a step-child of the Critical Pedagogy Program at the University of Saint Thomas. As a scholar-activist, Abendroth has produced a courageous and prescient volume that will impact the field of critical…

Ancient Earth, Alien Earths Event

NASA Image and Video Library

2014-08-20

Panelists pose for a group photo at the “Ancient Earth, Alien Earths” Event at NASA Headquarters in Washington, DC Wednesday, August 20, 2014. The event was sponsored by NASA, the National Science Foundation (NSF), and the Smithsonian Institution and highlighted how research on early Earth could help guide our search for habitable planets orbiting other stars. Photo Credit: (NASA/Aubrey Gemignani)

ENERGY STAR® Retail Products Platform (RPP): Conditions and Considerations in Evaluating Market Transformation Programs and Evaluation Guidance for RPP

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Michael; Banwell, Peter

2018-01-09

The purpose of this guide is to provide a resource for state utility regulators, utilities, the evaluation community and regulatory stakeholders on methods to measure energy savings from the ENERGY STAR Retail Products Platform (link is external). The guidelines outlined in this document were developed by evaluation experts.

At Saturn: Tripping the Flight Fantastic

NASA Astrophysics Data System (ADS)

Porco, Carolyn C.

2008-05-01

Boulder planetary scientist Carolyn Porco, leader of the imaging team for NASA's Cassini mission to Saturn and science advisor for the forthcoming movie "Star Trek," guides you on a magical mystery tour around the ringed planet. Come and witness the wonders, discoveries, and the awesome natural beauty of this amazing planet and its family of rings and moons.

The Office of Diversity and Inclusion at a Large Texas University: A Cultural Evolution

ERIC Educational Resources Information Center

Curette, Alvin R.

2016-01-01

This single, holistic, instrumental case study investigated the organizational history of the Office of Diversity and Inclusion (ODI) at Lone Star University. The study included an examination of changes to ODI's cultural identity. This study was guided by two principal research questions: a) Why was the office created and how has its cultural…

Some first experiments on the photometric calibration of Schmidt plates against the Tycho catalogue

NASA Technical Reports Server (NTRS)

Morrison, J. E.; Lasker, B.; McLean, B.; Bucciarelli, B.; Spagna, A.; Zacchei, A.

1997-01-01

Preliminary work carried out with the aim of reducing the Guide Star Catalog (GSC2) measurements of the Palomar 2 plates with the Tycho catalog for a 625 sq deg test field centered on the North Galactic Pole, is reported on and the results are presented. The emphasis was on the photometric calibrations.

The Young Astrophysicist: A Very Inexpensive Activity to Discuss Spectroscopy

ERIC Educational Resources Information Center

Brockington, Guilherme; Testoni, Leonardo André; Pietrocola, Maurício

2015-01-01

The continuing fascination of young people with celestial bodies leads them to pose challenging questions to their science teachers, such as how was the universe born? How were the stars formed? In this paper we present an extremely inexpensive but highly engaging activity to teach the basics of spectroscopy. Guided by the question "how do…

Performance Evaluation of the Gravity Probe B Design

NASA Technical Reports Server (NTRS)

Francis, Ronnie; Wells, Eugene M.

1996-01-01

This report documents the simulation of the Lockheed Martin designed Gravity Probe B (GPB) spacecraft developed tool by bd Systems Inc using the TREETOPS simulation. This study quantifies the effects of flexibility and liquid helium slosh on GPB spacecraft control performance. The TREETOPS simulation tool permits the simulation of flexible structures given that a flexible body model of the structure is available. For purposes of this study, a flexible model of the GPB spacecraft was obtained from Lockheed Martin. To model the liquid helium slosh effects, computational fluid dynamics (CFD) results' were obtained, and used to develop a dynamic model of the slosh effects. The flexible body and slosh effects were incorporated separately into the TREETOPS simulation, which places the vehicle in a 650 km circular polar orbit and subjects the spacecraft to realistic environmental disturbances and sensor error quantities. In all of the analysis conducted in this study the spacecraft is pointed at an inertially fixed guide star (GS) and is rotating at a constant rate about this line of sight.

First faint dual-field off-axis observations in optical long baseline interferometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Woillez, J.; Wizinowich, P.; Ragland, S.

2014-03-10

Ground-based long baseline interferometers have long been limited in sensitivity in part by the short integration periods imposed by atmospheric turbulence. The first observation fainter than this limit was performed on 2011 January 22 when the Keck Interferometer observed a K = 11.5 target, about 1 mag fainter than its K = 10.3 atmospherically imposed limit; the currently demonstrated limit is K = 12.5. These observations were made possible by the Dual-Field Phase-Referencing (DFPR) instrument, part of the NSF-funded ASTrometry and phase-Referenced Astronomy project; integration times longer than the turbulence time scale are made possible by its ability to simultaneouslymore » measure the real-time effects of the atmosphere on a nearby bright guide star and correct for it on the faint target. We present the implementation of DFPR on the Keck Interferometer. Then, we detail its on-sky performance focusing on the accuracy of the turbulence correction and the resulting fringe contrast stability.« less

Robust polygon recognition method with similarity invariants applied to star identification

NASA Astrophysics Data System (ADS)

Hernández, E. Antonio; Alonso, Miguel A.; Chávez, Edgar; Covarrubias, David H.; Conte, Roberto

2017-02-01

In the star identification process the goal is to recognize a star by using the celestial bodies in its vicinity as context. An additional requirement is to avoid having to perform an exhaustive scan of the star database. In this paper we present a novel approach to star identification using similarity invariants. More specifically, the proposed algorithm defines a polygon for each star, using the neighboring celestial bodies in the field of view as vertices. The mapping is insensitive to similarity transformation; that is, the image of the polygon under the transformation is not affected by rotation, scaling or translations. Each polygon is associated with an essentially unique complex number. We perform an exhaustive experimental validation of the proposed algorithm using synthetic data generated from the star catalog with uniformly-distributed positional noise introduced to each star. The star identification method that we present is proven to be robust, achieving a recognition rate of 99.68% when noise levels of up to ± 424 μ radians are introduced to the location of the stars. In our tests the proposed algorithm proves that if a polygon match is found, it always corresponds to the star under analysis; no mismatches are found. In its present form our method cannot identify polygons in cases where there exist missing or false stars in the analyzed images, in those situations it only indicates that no match was found.

Simulating the performance of adaptive optics techniques on FSO communications through the atmosphere

NASA Astrophysics Data System (ADS)

Martínez, Noelia; Rodríguez Ramos, Luis Fernando; Sodnik, Zoran

2017-08-01

The Optical Ground Station (OGS), installed in the Teide Observatory since 1995, was built as part of ESA efforts in the research field of satellite optical communications to test laser telecommunication terminals on board of satellites in Low Earth Orbit and Geostationary Orbit. As far as one side of the link is settled on the Earth, the laser beam (either on the uplink or on the downlink) has to bear with the atmospheric turbulence. Within the framework of designing an Adaptive Optics system to improve the performance of the Free-Space Optical Communications at the OGS, turbulence conditions regarding uplink and downlink have been simulated within the OOMAO (Object-Oriented Matlab Adaptive Optics) Toolbox as well as the possible utilization of a Laser Guide Star to measure the wavefront in this context. Simulations have been carried out by reducing available atmospheric profiles regarding both night-time and day-time measurements and by having into account possible seasonal changes. An AO proposal to reduce atmospheric aberrations and, therefore, ameliorate FSO links performance is presented and analysed in this paper

Psychometric Properties of the Japanese Version of the STarT Back Tool in Patients with Low Back Pain.

PubMed

Matsudaira, Ko; Oka, Hiroyuki; Kikuchi, Norimasa; Haga, Yuri; Sawada, Takayuki; Tanaka, Sakae

2016-01-01

The STarT Back Tool uses prognostic indicators to classify patients with low back pain into three risk groups to guide early secondary prevention in primary care. The present study aimed to evaluate the psychometric properties of the Japanese version of the tool (STarT-J). An online survey was conducted among Japanese patients with low back pain aged 20-64 years. Reliability was assessed by examining the internal consistency of the overall and psychosocial subscales using Cronbach's alpha coefficients. Spearman's correlation coefficients were used to evaluate the concurrent validity between the STarT-J total score/psychosocial subscore and standard reference questionnaires. Discriminant validity was evaluated by calculating the area under the curves (AUCs) for the total and psychosocial subscale scores against standard reference cases. Known-groups validity was assessed by examining the relationship between low back pain-related disability and STarT-J scores. The analysis included data for 2000 Japanese patients with low back pain; the mean (standard deviation [SD]) age was 47.7 (9.3) years, and 54.1% were male. The mean (SD) STarT-J score was 2.2 (2.1). The Cronbach's alpha coefficient was 0.75 for the overall scale and 0.66 for the psychosocial subscale. Spearman's correlation coefficients ranged from 0.30 to 0.59, demonstrating moderate to strong concurrent validity. The AUCs for the total score ranged from 0.65 to 0.83, mostly demonstrating acceptable discriminative ability. For known-groups validity, participants with more somatic symptoms had higher total scores. Those in higher STarT-J risk groups had experienced more low back pain-related absences. The overall STarT-J scale was internally consistent and had acceptable concurrent, discriminant, and known-groups validity. The STarT-J can be used with Japanese patients with low back pain.

Optimized star sensors laboratory calibration method using a regularization neural network.

PubMed

Zhang, Chengfen; Niu, Yanxiong; Zhang, Hao; Lu, Jiazhen

2018-02-10

High-precision ground calibration is essential to ensure the performance of star sensors. However, the complex distortion and multi-error coupling have brought great difficulties to traditional calibration methods, especially for large field of view (FOV) star sensors. Although increasing the complexity of models is an effective way to improve the calibration accuracy, it significantly increases the demand for calibration data. In order to achieve high-precision calibration of star sensors with large FOV, a novel laboratory calibration method based on a regularization neural network is proposed. A multi-layer structure neural network is designed to represent the mapping of the star vector and the corresponding star point coordinate directly. To ensure the generalization performance of the network, regularization strategies are incorporated into the net structure and the training algorithm. Simulation and experiment results demonstrate that the proposed method can achieve high precision with less calibration data and without any other priori information. Compared with traditional methods, the calibration error of the star sensor decreased by about 30%. The proposed method can satisfy the precision requirement for large FOV star sensors.

Precision Attitude Determination System (PADS) design and analysis. Two-axis gimbal star tracker

NASA Technical Reports Server (NTRS)

1973-01-01

Development of the Precision Attitude Determination System (PADS) focused chiefly on the two-axis gimballed star tracker and electronics design improved from that of Precision Pointing Control System (PPCS), and application of the improved tracker for PADS at geosynchronous altitude. System design, system analysis, software design, and hardware design activities are reported. The system design encompasses the PADS configuration, system performance characteristics, component design summaries, and interface considerations. The PADS design and performance analysis includes error analysis, performance analysis via attitude determination simulation, and star tracker servo design analysis. The design of the star tracker and electronics are discussed. Sensor electronics schematics are included. A detailed characterization of the application software algorithms and computer requirements is provided.

A novel star extraction method based on modified water flow model

NASA Astrophysics Data System (ADS)

Zhang, Hao; Niu, Yanxiong; Lu, Jiazhen; Ouyang, Zibiao; Yang, Yanqiang

2017-11-01

Star extraction is the essential procedure for attitude measurement of star sensor. The great challenge for star extraction is to segment star area exactly from various noise and background. In this paper, a novel star extraction method based on Modified Water Flow Model(MWFM) is proposed. The star image is regarded as a 3D terrain. The morphology is adopted for noise elimination and Tentative Star Area(TSA) selection. Star area can be extracted through adaptive water flowing within TSAs. This method can achieve accurate star extraction with improved efficiency under complex conditions such as loud noise and uneven backgrounds. Several groups of different types of star images are processed using proposed method. Comparisons with existing methods are conducted. Experimental results show that MWFM performs excellently under different imaging conditions. The star extraction rate is better than 95%. The star centroid accuracy is better than 0.075 pixels. The time-consumption is also significantly reduced.

Photodetectors on Coronagraph Mask for Pointing Control

NASA Technical Reports Server (NTRS)

Balasubramanian, Kunjithapatham

2007-01-01

It has been proposed to install a symmetrical array of photodetectors about the center of the mask of a coronagraph of the type used to search for planets orbiting remote stars. The purpose of this installation is to utilize the light from a star under observation as a guide in pointing the telescope. Simple arithmetic processing of the outputs of the photodetectors would provide indications of the lateral position of the center of the mask relative to the center of the image of the star. These indications could serve as pointing-control feedback signals for adjusting the telescope aim to center the image of the star on the mask. The widths of central mask areas available for placement of photodetectors differ among coronagraph designs, typically ranging upward from about 100 m. Arrays of photodetectors can readily be placed within areas in this size range. The number of detectors in an array could be as small as 4 or as large as 64. The upper limit on the number of detectors would be determined according to the extent of the occulting pattern and the number of functionalities, in addition to pointing control, to be served by the array.

The structure and energy balance of cool star atmospheres

NASA Technical Reports Server (NTRS)

Linsky, J. L.

1982-01-01

The atmospheric structure and energy balance phenomena associated with magnetic fields in the Sun are reviewed and it is shown that similar phenomena occur in cool stars. The evidence for the weakening or disappearance of transition regions and coronae is discussed together with the appearance of extended cool chromospheres with large mass loss, near V-R = 0.80 in the H-R diagram. Like the solar atmosphere, these atmospheres are not homogeneous and there is considerable evidence for plage regions with bright TR emission lines that overlie dark (presumably magnetic) star spots. The IUE observations are providing important information on the energy balance in these atmospheres that should guide theoretical calculations of the nonradiative heating rate. Recent high dispersion spectra are providing unique information concerning which components of close binary systems are the dominant contributors to the observed emission. A recent unanticipated discovery is that the transition lines are redshifted (an antiwind) in DRa (G2 Ib) and perhaps other stars. Finally, the G and K giants and supergiants are classified into three groups depending on whether their atmospheres are dominated by closed magnetic flux tubes, open field geometries, or a predominately open geometry with a few closed flux tubes embedded.

Structure–function studies of STAR family Quaking proteins bound to their in vivo RNA target sites

PubMed Central

Teplova, Marianna; Hafner, Markus; Teplov, Dmitri; Essig, Katharina; Tuschl, Thomas; Patel, Dinshaw J.

2013-01-01

Mammalian Quaking (QKI) and its Caenorhabditis elegans homolog, GLD-1 (defective in germ line development), are evolutionarily conserved RNA-binding proteins, which post-transcriptionally regulate target genes essential for developmental processes and myelination. We present X-ray structures of the STAR (signal transduction and activation of RNA) domain, composed of Qua1, K homology (KH), and Qua2 motifs of QKI and GLD-1 bound to high-affinity in vivo RNA targets containing YUAAY RNA recognition elements (RREs). The KH and Qua2 motifs of the STAR domain synergize to specifically interact with bases and sugar-phosphate backbones of the bound RRE. Qua1-mediated homodimerization generates a scaffold that enables concurrent recognition of two RREs, thereby plausibly targeting tandem RREs present in many QKI-targeted transcripts. Structure-guided mutations reduced QKI RNA-binding affinity in vitro and in vivo, and expression of QKI mutants in human embryonic kidney cells (HEK293) significantly decreased the abundance of QKI target mRNAs. Overall, our studies define principles underlying RNA target selection by STAR homodimers and provide insights into the post-transcriptional regulatory function of mammalian QKI proteins. PMID:23630077

Laser guide star pointing camera for ESO LGS Facilities

NASA Astrophysics Data System (ADS)

Bonaccini Calia, D.; Centrone, M.; Pedichini, F.; Ricciardi, A.; Cerruto, A.; Ambrosino, F.

2014-08-01

Every observatory using LGS-AO routinely has the experience of the long time needed to bring and acquire the laser guide star in the wavefront sensor field of view. This is mostly due to the difficulty of creating LGS pointing models, because of the opto-mechanical flexures and hysteresis in the launch and receiver telescope structures. The launch telescopes are normally sitting on the mechanical structure of the larger receiver telescope. The LGS acquisition time is even longer in case of multiple LGS systems. In this framework the optimization of the LGS systems absolute pointing accuracy is relevant to boost the time efficiency of both science and technical observations. In this paper we show the rationale, the design and the feasibility tests of a LGS Pointing Camera (LPC), which has been conceived for the VLT Adaptive Optics Facility 4LGSF project. The LPC would assist in pointing the four LGS, while the VLT is doing the initial active optics cycles to adjust its own optics on a natural star target, after a preset. The LPC allows minimizing the needed accuracy for LGS pointing model calibrations, while allowing to reach sub-arcsec LGS absolute pointing accuracy. This considerably reduces the LGS acquisition time and observations operation overheads. The LPC is a smart CCD camera, fed by a 150mm diameter aperture of a Maksutov telescope, mounted on the top ring of the VLT UT4, running Linux and acting as server for the client 4LGSF. The smart camera is able to recognize within few seconds the sky field using astrometric software, determining the stars and the LGS absolute positions. Upon request it returns the offsets to give to the LGS, to position them at the required sky coordinates. As byproduct goal, once calibrated the LPC can calculate upon request for each LGS, its return flux, its fwhm and the uplink beam scattering levels.

Star tracker operation in a high density proton field

NASA Technical Reports Server (NTRS)

Miklus, Kenneth J.; Kissh, Frank; Flynn, David J.

1993-01-01

Algorithms that reject transient signals due to proton effects on charge coupled device (CCD) sensors have been implemented in the HDOS ASTRA-l Star Trackers to be flown on the TOPEX mission scheduled for launch in July 1992. A unique technique for simulating a proton-rich environment to test trackers is described, as well as the test results obtained. Solar flares or an orbit that passes through the South Atlantic Anomaly can subject the vehicle to very high proton flux levels. There are three ways in which spurious proton generated signals can impact tracker performance: the many false signals can prevent or extend the time to acquire a star; a proton-generated signal can compromise the accuracy of the star's reported magnitude and position; and the tracked star can be lost, requiring reacquisition. Tests simulating a proton-rich environment were performed on two ASTRA-1 Star Trackers utilizing these new algorithms. There were no false acquisitions, no lost stars, and a significant reduction in reported position errors due to these improvements.

Status report on the Large Binocular Telescope's ARGOS ground-layer AO system

NASA Astrophysics Data System (ADS)

Hart, M.; Rabien, S.; Busoni, L.; Barl, L.; Beckmann, U.; Bonaglia, M.; Boose, Y.; Borelli, J. L.; Bluemchen, T.; Carbonaro, L.; Connot, C.; Deysenroth, M.; Davies, R.; Durney, O.; Elberich, M.; Ertl, T.; Esposito, S.; Gaessler, W.; Gasho, V.; Gemperlein, H.; Hubbard, P.; Kanneganti, S.; Kulas, M.; Newman, K.; Noenickx, J.; Orban de Xivry, G.; Peter, D.; Quirrenbach, A.; Rademacher, M.; Schwab, C.; Storm, J.; Vaitheeswaran, V.; Weigelt, G.; Ziegleder, J.

2011-10-01

ARGOS, the laser-guided adaptive optics system for the Large Binocular Telescope (LBT), is now under construction at the telescope. By correcting atmospheric turbulence close to the telescope, the system is designed to deliver high resolution near infrared images over a field of 4 arc minute diameter. Each side of the LBT is being equipped with three Rayleigh laser guide stars derived from six 18 W pulsed green lasers and projected into two triangular constellations matching the size of the corrected field. The returning light is to be detected by wavefront sensors that are range gated within the seeing-limited depth of focus of the telescope. Wavefront correction will be introduced by the telescope's deformable secondary mirrors driven on the basis of the average wavefront errors computed from the respective guide star constellation. Measured atmospheric turbulence profiles from the site lead us to expect that by compensating the ground-layer turbulence, ARGOS will deliver median image quality of about 0.2 arc sec across the JHK bands. This will be exploited by a pair of multi-object near-IR spectrographs, LUCIFER1 and LUCIFER2, with 4 arc minute field already operating on the telescope. In future, ARGOS will also feed two interferometric imaging instruments, the LBT Interferometer operating in the thermal infrared, and LINC-NIRVANA, operating at visible and near infrared wavelengths. Together, these instruments will offer very broad spectral coverage at the diffraction limit of the LBT's combined aperture, 23 m in size.

Layer-oriented simulation tool.

PubMed

Arcidiacono, Carmelo; Diolaiti, Emiliano; Tordi, Massimiliano; Ragazzoni, Roberto; Farinato, Jacopo; Vernet, Elise; Marchetti, Enrico

2004-08-01

The Layer-Oriented Simulation Tool (LOST) is a numerical simulation code developed for analysis of the performance of multiconjugate adaptive optics modules following a layer-oriented approach. The LOST code computes the atmospheric layers in terms of phase screens and then propagates the phase delays introduced in the natural guide stars' wave fronts by using geometrical optics approximations. These wave fronts are combined in an optical or numerical way, including the effects of wave-front sensors on measurements in terms of phase noise. The LOST code is described, and two applications to layer-oriented modules are briefly presented. We have focus on the Multiconjugate adaptive optics demonstrator to be mounted upon the Very Large Telescope and on the Near-IR-Visible Adaptive Interferometer for Astronomy (NIRVANA) interferometric system to be installed on the combined focus of the Large Binocular Telescope.

Brillouin micro-spectroscopy through aberrations via sensorless adaptive optics

NASA Astrophysics Data System (ADS)

Edrei, Eitan; Scarcelli, Giuliano

2018-04-01

Brillouin spectroscopy is a powerful optical technique for non-contact viscoelastic characterizations which has recently found applications in three-dimensional mapping of biological samples. Brillouin spectroscopy performances are rapidly degraded by optical aberrations and have therefore been limited to homogenous transparent samples. In this work, we developed an adaptive optics (AO) configuration designed for Brillouin scattering spectroscopy to engineer the incident wavefront and correct for aberrations. Our configuration does not require direct wavefront sensing and the injection of a "guide-star"; hence, it can be implemented without the need for sample pre-treatment. We used our AO-Brillouin spectrometer in aberrated phantoms and biological samples and obtained improved precision and resolution of Brillouin spectral analysis; we demonstrated 2.5-fold enhancement in Brillouin signal strength and 1.4-fold improvement in axial resolution because of the correction of optical aberrations.

The 2005 HST Calibration Workshop Hubble After the Transition to Two-Gyro Mode

NASA Technical Reports Server (NTRS)

Koekemoer, Anton M. (Editor); Goodfrooij, Paul (Editor); Dressel, Linda L. (Editor)

2006-01-01

The 2005 HST Calibration Workshop was held at the Space Telescope Science Institute during October 26, 2005 to bring together members of the observing community, the instrument development teams, and the STScI instrument support teams to share information and techniques. Presentations included the two-gyro performance of HST and FGS, advances in the calibration of a number of instruments, the results of other instruments after their return from space, and the status of still others which are scheduled for installation during the next servicing mission. Cross-calibration between HST and JWST was discussed, as well as the new Guide Star Catalog and advances in data analysis software. This book contains the published record of the workshop, while all the talks and posters are available electronically on the workshop Web site.

Keck adaptive optics: control subsystem

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brase, J.M.; An, J.; Avicola, K.

1996-03-08

Adaptive optics on the Keck 10 meter telescope will provide an unprecedented level of capability in high resolution ground based astronomical imaging. The system is designed to provide near diffraction limited imaging performance with Strehl {gt} 0.3 n median Keck seeing of r0 = 25 cm, T =10 msec at 500 nm wavelength. The system will be equipped with a 20 watt sodium laser guide star to provide nearly full sky coverage. The wavefront control subsystem is responsible for wavefront sensing and the control of the tip-tilt and deformable mirrors which actively correct atmospheric turbulence. The spatial sampling interval formore » the wavefront sensor and deformable mirror is de=0.56 m which gives us 349 actuators and 244 subapertures. This paper summarizes the wavefront control system and discusses particular issues in designing a wavefront controller for the Keck telescope.« less

Performance of a day time star sensor for a stabilized balloon platform

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rossi, E.; DiCocco, G.; Donati, A.

1989-02-01

A modified version of a CCD star tracker originally designed for use on the ROSAT X ray astronomy satellite, has been built for use on a three axis stabilized balloon platform. The first flight of this star sensor was planned for may 1988 from the NASA Balloon base at Palestine, Texas. The expected performance of this instrument is described along with the preflight results.

Galileo Attitude Determination: Experiences with a Rotating Star Scanner

NASA Technical Reports Server (NTRS)

Merken, L.; Singh, G.

1991-01-01

The Galileo experience with a rotating star scanner is discussed in terms of problems encountered in flight, solutions implemented, and lessons learned. An overview of the Galileo project and the attitude and articulation control subsystem is given and the star scanner hardware and relevant software algorithms are detailed. The star scanner is the sole source of inertial attitude reference for this spacecraft. Problem symptoms observed in flight are discussed in terms of effects on spacecraft performance and safety. Sources of thse problems include contributions from flight software idiosyncrasies and inadequate validation of the ground procedures used to identify target stars for use by the autonomous on-board star identification algorithm. Problem fixes (some already implemented and some only proposed) are discussed. A general conclusion is drawn regarding the inherent difficulty of performing simulation tests to validate algorithms which are highly sensitive to external inputs of statistically 'rare' events.

The ultraviolet spectrum of noncoronal late-type stars - The Gamma Crucis (M3.4 III) reference spectrum

NASA Technical Reports Server (NTRS)

Carpenter, Kenneth G.; Pesce, Joseph E.; Stencel, Robert E.; Brown, Alexander; Johansson, Sveneric

1988-01-01

A guide is presented to the UV spectrum of M-type giants and supergiants whose outer atmospheres contain warm chromospheres but not coronae. The M3 giant Gamma Crucis is taken as the archetype of the cooler, oxygen-rich, noncoronal stars. Line identifications and integrated line flux measurements of the chromospheric emission features seen in the 1200-3200 A range of IUE high-resolution spectra are presented. The major fluorescence processes operating in the outer atmosphere of Gamma Crucis, including eight previously unknown pumping processes and 21 new fluorescent line products, are summarized, and the enhancements of selected line strengths by 'line leakage' is discussed. A set of absorption features toward the longer wavelength end of this range is identified which can be used to characterize the radial velocity of the stellar photospheres. The applicability of the results to the spectra of noncoronal stars with different effective temperatures and gravities is discussed.

StarTrax --- The Next Generation User Interface

NASA Astrophysics Data System (ADS)

Richmond, Alan; White, Nick

StarTrax is a software package to be distributed to end users for installation on their local computing infrastructure. It will provide access to many services of the HEASARC, i.e. bulletins, catalogs, proposal and analysis tools, initially for the ROSAT MIPS (Mission Information and Planning System), later for the Next Generation Browse. A user activating the GUI will reach all HEASARC capabilities through a uniform view of the system, independent of the local computing environment and of the networking method of accessing StarTrax. Use it if you prefer the point-and-click metaphor of modern GUI technology, to the classical command-line interfaces (CLI). Notable strengths include: easy to use; excellent portability; very robust server support; feedback button on every dialog; painstakingly crafted User Guide. It is designed to support a large number of input devices including terminals, workstations and personal computers. XVT's Portability Toolkit is used to build the GUI in C/C++ to run on: OSF/Motif (UNIX or VMS), OPEN LOOK (UNIX), or Macintosh, or MS-Windows (DOS), or character systems.

NGST fine guidance sensor

NASA Astrophysics Data System (ADS)

Rowlands, Neil; Hutchings, John; Murowinski, Richard G.; Alexander, Russ

2003-03-01

Instrumentation for the Next Generation Space Telescope (NGST) is currently in the Phase A definition stage. We have developed a concept for the NGST Fine Guidance Sensor or FGS. The FGS is a detector array based imager which resides in the NGST focal plane. We report here on tradeoff studies aimed at defining an overall configuration of the FGS which will meet the performance and interface requirements. A key performance requirement is a noise equivalent angle of 3 milli-arcseconds to be achieved with 95% probability for any pointing of the observatory in the celestial sphere. A key interface requirement is compatibility with the architecture of the Integrated Science Instrument Module (ISIM). The concept developed consists of two independent and redundant FGS modules, each with a 4' x 2' field of view covered by two 2048 x 2048 infrared detector arrays, providing 60 milli-arcsecond sampling. Performance modeling supporting the choice of this architecture and the trade space considered is presented. Each module has a set of readout electronics which perform star detection, pixel-by-pixel correction, and in fine guiding mode, centroid calculation. These readout electronics communicate with the ISIM Command &Data Handling Units where the FGS control software is based. Rationale for this choice of architecture is also presented.

Bioinspired Star-Shaped Poly(l-lysine) Polypeptides: Efficient Polymeric Nanocarriers for the Delivery of DNA to Mesenchymal Stem Cells.

PubMed

Walsh, David P; Murphy, Robert D; Panarella, Angela; Raftery, Rosanne M; Cavanagh, Brenton; Simpson, Jeremy C; O'Brien, Fergal J; Heise, Andreas; Cryan, Sally-Ann

2018-05-07

The field of tissue engineering is increasingly recognizing that gene therapy can be employed for modulating in vivo cellular response thereby guiding tissue regeneration. However, the field lacks a versatile and biocompatible gene delivery platform capable of efficiently delivering transgenes to mesenchymal stem cells (MSCs), a cell type often refractory to transfection. Herein, we describe the extensive and systematic exploration of three architectural variations of star-shaped poly(l-lysine) polypeptide (star-PLL) with varying number and length of poly(l-lysine) arms as potential nonviral gene delivery vectors for MSCs. We demonstrate that star-PLL vectors are capable of self-assembling with pDNA to form stable, cationic nanomedicines. Utilizing high content screening, live cell imaging, and mechanistic uptake studies we confirm the intracellular delivery of pDNA by star-PLLs to MSCs is a rapid process, which likely proceeds via a clathrin-independent mechanism. We identify a star-PLL composition with 64 poly(l-lysine) arms and five l-lysine subunits per arm as a particularly efficient vector that is capable of delivering both reporter genes and the therapeutic transgenes bone morphogenetic protein-2 and vascular endothelial growth factor to MSCs. This composition facilitated a 1000-fold increase in transgene expression in MSCs compared to its linear analogue, linear poly(l-lysine). Furthermore, it demonstrated comparable transgene expression to the widely used vector polyethylenimine using a lower pDNA dose with significantly less cytotoxicity. Overall, this study illustrates the ability of the star-PLL vectors to facilitate efficient, nontoxic nucleic acid delivery to MSCs thereby functioning as an innovative nanomedicine platform for tissue engineering applications.

Analysis of Dragon's Breath and Scattered Light Detector Anomalies on WFC3/UVIS

NASA Astrophysics Data System (ADS)

Fowler, Julia; Markwardt, Larissa; Bourque, Matthew; Anderson, Jay

2017-02-01

We summarize the examination of the light anomalies known as Dragon's Breath and Scattered Light for the UVIS channel of Wide Field Camera 3 (WFC3) of the Hubble Space Telescope (HST). We present three methods for WFC3 users to help avoid these effects during observation planning. We analyzed all of the full-frame wide and long pass filters with exposure times ≥ 300 seconds, comprising ∼13% of WFC3/UVIS on-orbit data (∼20% of all full-frame data, and ∼35% of all full-frame ≥300 second exposures.) We find that stars producing Dragon's Breath peak at specific orientations to the detector and V-band magnitudes. The bulk of these stars fall along the vertical and horizontal edges, within ∼490 pixels of the image frame. The corners of the detector show significantly fewer instances of Dragon's Breath and Scattered Light, though still a few occurrences. Furthermore, matching stars outside the field of the image to V-band magnitude data from the Hubble Guide Star Catalog II (GSC-II) shows that stars causing the anomaly consistently peak around a V-band magnitude of 11.9 or 14.6, whereas the general trend of objects lying outside the field instead peaks around a magnitude of 16.5 within our exposure time and filter selection.

Exploring Game Performance in the National Basketball Association Using Player Tracking Data

PubMed Central

Calleja-González, Julio; Jiménez Sáiz, Sergio; Schelling i del Alcázar, Xavi; Balciunas, Mindaugas

2015-01-01

Recent player tracking technology provides new information about basketball game performance. The aim of this study was to (i) compare the game performances of all-star and non all-star basketball players from the National Basketball Association (NBA), and (ii) describe the different basketball game performance profiles based on the different game roles. Archival data were obtained from all 2013-2014 regular season games (n = 1230). The variables analyzed included the points per game, minutes played and the game actions recorded by the player tracking system. To accomplish the first aim, the performance per minute of play was analyzed using a descriptive discriminant analysis to identify which variables best predict the all-star and non all-star playing categories. The all-star players showed slower velocities in defense and performed better in elbow touches, defensive rebounds, close touches, close points and pull-up points, possibly due to optimized attention processes that are key for perceiving the required appropriate environmental information. The second aim was addressed using a k-means cluster analysis, with the aim of creating maximal different performance profile groupings. Afterwards, a descriptive discriminant analysis identified which variables best predict the different playing clusters. The results identified different playing profile of performers, particularly related to the game roles of scoring, passing, defensive and all-round game behavior. Coaching staffs may apply this information to different players, while accounting for individual differences and functional variability, to optimize practice planning and, consequently, the game performances of individuals and teams. PMID:26171606

Exploring Game Performance in the National Basketball Association Using Player Tracking Data.

PubMed

Sampaio, Jaime; McGarry, Tim; Calleja-González, Julio; Jiménez Sáiz, Sergio; Schelling I Del Alcázar, Xavi; Balciunas, Mindaugas

2015-01-01

Recent player tracking technology provides new information about basketball game performance. The aim of this study was to (i) compare the game performances of all-star and non all-star basketball players from the National Basketball Association (NBA), and (ii) describe the different basketball game performance profiles based on the different game roles. Archival data were obtained from all 2013-2014 regular season games (n = 1230). The variables analyzed included the points per game, minutes played and the game actions recorded by the player tracking system. To accomplish the first aim, the performance per minute of play was analyzed using a descriptive discriminant analysis to identify which variables best predict the all-star and non all-star playing categories. The all-star players showed slower velocities in defense and performed better in elbow touches, defensive rebounds, close touches, close points and pull-up points, possibly due to optimized attention processes that are key for perceiving the required appropriate environmental information. The second aim was addressed using a k-means cluster analysis, with the aim of creating maximal different performance profile groupings. Afterwards, a descriptive discriminant analysis identified which variables best predict the different playing clusters. The results identified different playing profile of performers, particularly related to the game roles of scoring, passing, defensive and all-round game behavior. Coaching staffs may apply this information to different players, while accounting for individual differences and functional variability, to optimize practice planning and, consequently, the game performances of individuals and teams.

Random generation of the turbulence slopes of a Shack-Hartmann wavefront sensor.

PubMed

Conan, Rodolphe

2014-03-15

A method to generate the turbulence measurements of a Shack-Hartmann wavefront sensor is presented. Numerical simulations demonstrate that the spatial and temporal statistic properties of the slopes are respected, allowing us to generate the turbulence wavefront gradient corresponding to both natural and laser guide stars, as well as time series in accordance with the frozen flow model.

PDSS/IMC CIS user's guide

NASA Technical Reports Server (NTRS)

1984-01-01

The Spacelab Payload Development Support System PDSS Image Motion Compensator (IMC) computer interface simulation (CIS) user's manual is given. The software provides a real time interface simulation for the following IMC subsystems: the Dry Rotor Reference Unit, the Advanced Star/Target Reference Optical sensor, the Ultra Violet imaging telescope, the Wisconson Ultraviolet Photopolarimetry Experiment, the Cruciform Power distributor, and the Spacelab Experiment Computer Operating System.

Claire Danes's Star-Body, Teen Female Viewers and the Pluralisation of Authorship in Baz Luhrmann's "William Shakespeare's Romeo + Juliet"

ERIC Educational Resources Information Center

Keam, Angela

2008-01-01

Teaching William Shakespeare's canonical tragedy "Romeo and Juliet" to teenagers in the context of the English classroom in Australia is not a particularly new pedagogical practice. In the year 2008, when many teachers (particularly those with a feminist bent such as I) are intent on guiding their students to decipher the ideological…

On the origin of high-velocity runaway stars

NASA Astrophysics Data System (ADS)

Gvaramadze, Vasilii V.; Gualandris, Alessia; Portegies Zwart, Simon

2009-06-01

We explore the hypothesis that some high-velocity runaway stars attain their peculiar velocities in the course of exchange encounters between hard massive binaries and a very massive star (either an ordinary 50-100Msolar star or a more massive one, formed through runaway mergers of ordinary stars in the core of a young massive star cluster). In this process, one of the binary components becomes gravitationally bound to the very massive star, while the second one is ejected, sometimes with a high speed. We performed three-body scattering experiments and found that early B-type stars (the progenitors of the majority of neutron stars) can be ejected with velocities of >~200-400kms-1 (typical of pulsars), while 3-4Msolar stars can attain velocities of >~300-400kms-1 (typical of the bound population of halo late B-type stars). We also found that the ejected stars can occasionally attain velocities exceeding the Milky Ways's escape velocity.

Four Star School Awards: Key Factors that Predict High Performance among Indiana School Corporations

ERIC Educational Resources Information Center

Veracco, Lawrence H.

2009-01-01

The purpose of this study was to analyze the Four Star status of Indiana school corporations in order to determine if certain variables currently existing among school corporations could be predictive of Four Star status. Differences in Four Star status were examined with respect to school corporation size, school corporation average teacher…

Guide star catalogue data retrieval software 2

NASA Technical Reports Server (NTRS)

Smirnov, O. M.; Malkov, O. YU.

1992-01-01

The Guide Star Catalog (GSC), being the largest astronomical catalog to date, is widely used by the astronomical community for all sorts of applications, such as statistical studies of certain sky regions, searches for counterparts to observational phenomena, and generation of finder charts. It's format (2 CD-ROM's) requires minimum hardware and is ideally suited for all sorts of conditions, especially observations. Unfortunately, the actual GSC data is not easily accessible. It takes the form of FITS tables, and the coordinates of the objects are given in one coordinate system (equinox 2000). The included reading software is rudimentary at best. Thus, even generation of a simple finder chart is not a trivial undertaking. To solve this problem, at least for PC users, GUIDARES was created. GUIDARES is a user-friendly program that lets you look directly at the data in the GSC, either as a graphical sky map or as a text table. GUIDARES can read a sampling of GSC data from a given sky region, store this sampling in a text file, and display a graphical map of the sampled region in projected celestial coordinates (perfect for finder charts). GUIDARES supports rectangular and circular regions defined by coordinates in the equatorial, ecliptic (any equinox) or galactic systems.

False star detection and isolation during star tracking based on improved chi-square tests.

PubMed

Zhang, Hao; Niu, Yanxiong; Lu, Jiazhen; Yang, Yanqiang; Su, Guohua

2017-08-01

The star sensor is a precise attitude measurement device for a spacecraft. Star tracking is the main and key working mode for a star sensor. However, during star tracking, false stars become an inevitable interference for star sensor applications, which may result in declined measurement accuracy. A false star detection and isolation algorithm in star tracking based on improved chi-square tests is proposed in this paper. Two estimations are established based on a Kalman filter and a priori information, respectively. The false star detection is operated through adopting the global state chi-square test in a Kalman filter. The false star isolation is achieved using a local state chi-square test. Semi-physical experiments under different trajectories with various false stars are designed for verification. Experiment results show that various false stars can be detected and isolated from navigation stars during star tracking, and the attitude measurement accuracy is hardly influenced by false stars. The proposed algorithm is proved to have an excellent performance in terms of speed, stability, and robustness.

Precision Attitude Determination System (PADS) system design and analysis: Single-axis gimbal star tracker

NASA Technical Reports Server (NTRS)

1974-01-01

The feasibility is evaluated of an evolutionary development for use of a single-axis gimbal star tracker from prior two-axis gimbal star tracker based system applications. Detailed evaluation of the star tracker gimbal encoder is considered. A brief system description is given including the aspects of tracker evolution and encoder evaluation. System analysis includes evaluation of star availability and mounting constraints for the geosynchronous orbit application, and a covariance simulation analysis to evaluate performance potential. Star availability and covariance analysis digital computer programs are included.

STAR Performance with SPEAR (Signal Processing Electronic Attack RFIC)

DTIC Science & Technology

2017-03-01

STAR operation in the presence of 1 kW EIRP power , independently of the choice of transmitter in use. The paper reports on the status of the SPEAR...prototype will be presented. To the authors’ knowledge , the measured results from the prototype already demonstrate state-of-the-art STAR performance...self-generated high power interferers. SPEAR is an innovative approach to the full duplex challenge that meets the high demands of military systems

Scaling relations and the fundamental line of the local group dwarf galaxies

NASA Astrophysics Data System (ADS)

Woo, Joanna; Courteau, Stéphane; Dekel, Avishai

2008-11-01

We study the scaling relations between global properties of dwarf galaxies in the local group. In addition to quantifying the correlations between pairs of variables, we explore the `shape' of the distribution of galaxies in log parameter space using standardized principal component analysis, the analysis is performed first in the 3D structural parameter space of stellar mass M*, internal velocity V and characteristic radius R* (or surface brightness μ*). It is then extended to a 4D space that includes a stellar population parameter such as metallicity Z or star formation rate . We find that the local group dwarfs basically define a one-parameter `fundamental line' (FL), primarily driven by stellar mass, M*. A more detailed inspection reveals differences between the star formation properties of dwarf irregulars (dI's) and dwarf ellipticals (dE's), beyond the tendency of the latter to be more massive. In particular, the metallicities of dI's are typically lower by a factor of 3 at a given M* and they grow faster with increasing M*, showing a tighter FL in the 4D space for the dE's. The structural scaling relations of dI's resemble those of the more massive spirals, but the dI's have lower star formation rates for a given M* which also grow faster with increasing M*. On the other hand, the FL of the dE's departs from the fundamental plane of bigger ellipticals. While the one-parameter nature of the FL and the associated slopes of the scaling relations are consistent with the general predictions of supernova feedback from Dekel & Woo, the differences between the FL's of the dE's and the dI's remain a challenge and should serve as a guide for the secondary physical processes responsible for these two types.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cantrell, Justin R.; Henry, Todd J.; White, Russel J., E-mail: cantrell@chara.gsu.edu, E-mail: thenry@chara.gsu.edu, E-mail: white@chara.gsu.edu

We use the sample of known stars and brown dwarfs within 5 pc of the Sun, supplemented with AFGK stars within 10 pc, to determine which stellar spectral types provide the most habitable real estate—defined as locations where liquid water could be present on Earth-like planets. Stellar temperatures and radii are determined by fitting model spectra to spatially resolved broadband photometric energy distributions for stars in the sample. Using these values, the locations of the habitable zones are calculated using an empirical formula for planetary surface temperature and assuming the condition of liquid water, called here the empirical habitable zonemore » (EHZ). Systems that have dynamically disruptive companions are considered not habitable. We consider companions to be disruptive if the separation ratio of the companion to the habitable zone is less than 5:1. We use the results of these calculations to derive a simple formula for predicting the location of the EHZ for main sequence stars based on V – K color. We consider EHZ widths as more useful measures of the habitable real estate around stars than areas because multiple planets are not expected to orbit stars at identical stellar distances. This EHZ provides a qualitative guide on where to expect the largest population of planets in the habitable zones of main sequence stars. Because of their large numbers and lower frequency of short-period companions, M stars provide more EHZ real estate than other spectral types, possessing 36.5% of the habitable real estate en masse. K stars are second with 21.5%, while A, F, and G stars offer 18.5%, 6.9%, and 16.6%, respectively. Our calculations show that three M dwarfs within 10 pc harbor planets in their EHZs—GJ 581 may have two planets (d with msin i = 6.1 M {sub ⊕}; g with msin i = 3.1 M {sub ⊕}), GJ 667 C has one (c with msin i = 4.5 M {sub ⊕}), and GJ 876 has two (b with msin i = 1.89 M {sub Jup} and c with msin i = 0.56 M {sub Jup}). If Earth-like planets are as common around low-mass stars as recent Kepler results suggest, M stars will harbor more Earth-like planets in habitable zones than any other stellar spectral type.« less

"Journey to the Stars": Presenting What Stars Are to Global Planetarium Audiences by Blending Astrophysical Visualizations Into a Single Immersive Production at the American Museum of Natural History

NASA Astrophysics Data System (ADS)

Emmart, Carter; Mac Low, M.; Oppenheimer, B. R.; Kinzler, R.; Paglione, T. A. D.; Abbott, B. P.

2010-01-01

"Journey to the Stars" is the latest and fourth space show based on storytelling from data visualization at the Rose Center for Earth and Space at the American Museum of Natural History. This twenty five minute, full dome movie production presents to planetarium audiences what the stars are, where they come from, how they vary in type and over time, and why they are important to life of Earth. Over forty scientists from around the world contributed their research to what is visualized into roughly fifteen major scenes. How this production is directed into a consolidated immersive informal science experience with learning goals is an integrative process with many inputs and concerns for scientific accuracy. The goal is a seamless merger of visualizations at varying spatial and temporal scales with acuity toward depth perception, revealing unseen phenomena, and the layering of concepts together to build an understanding of stars; to blend our common experience of them in the sky with the uncommon meaning we have come to know through science. Scripted by Louise Gikow who has worked for Children's Television Workshop, narrated by Whoopie Goldberg, and musically scored by Robert Miller, this production strives to guide audiences through challenging scientific concepts by complimenting the natural beauty the subject matter presents with understandable prose and musical grandeur. "Journey to the Stars" was produced in cooperation with NASA's Science Mission Directorate, Heliophysics Division and is in release at major planetariums, worldwide.

StarNet: An application of deep learning in the analysis of stellar spectra

NASA Astrophysics Data System (ADS)

Kielty, Collin; Bialek, Spencer; Fabbro, Sebastien; Venn, Kim; O'Briain, Teaghan; Jahandar, Farbod; Monty, Stephanie

2018-06-01

In an era when spectroscopic surveys are capable of collecting spectra for hundreds of thousands of stars, fast and efficient analysis methods are required to maximize scientific impact. These surveys provide a homogeneous database of stellar spectra that are ideal for machine learning applications. In this poster, we present StarNet: a convolutional neural network model applied to the analysis of both SDSS-III APOGEE DR13 and synthetic stellar spectra. When trained on synthetic spectra alone, the calculated stellar parameters (temperature, surface gravity, and metallicity) are of excellent precision and accuracy for both APOGEE data and synthetic data, over a wide range of signal-to-noise ratios. While StarNet was developed using the APOGEE observed spectra and corresponding ASSeT synthetic grid, we suggest that this technique is applicable to other spectral resolutions, spectral surveys, and wavelength regimes. As a demonstration of this, we present a StarNet model trained on lower resolution, R=6000, IR synthetic spectra, describing the spectra delivered by Gemini/NIFS and the forthcoming Gemini/GIRMOS instrument (PI Sivanandam, UToronto). Preliminary results suggest that the stellar parameters determined from this low resolution StarNet model are comparable in precision to the high-resolution APOGEE results. The success of StarNet at lower resolution can be attributed to (1) a large training set of synthetic spectra (N ~200,000) with a priori stellar labels, and (2) the use of the entire spectrum in the solution rather than a few weighted windows, which are common methods in other spectral analysis tools (e.g. FERRE or The Cannon). Remaining challenges in our StarNet applications include rectification, continuum normalization, and wavelength coverage. Solutions to these problems could be used to guide decisions made in the development of future spectrographs, spectroscopic surveys, and data reduction pipelines, such as for the future MSE.

Highly accurate quantitative spectroscopy of massive stars in the Galaxy

NASA Astrophysics Data System (ADS)

Nieva, María-Fernanda; Przybilla, Norbert

2017-11-01

Achieving high accuracy and precision in stellar parameter and chemical composition determinations is challenging in massive star spectroscopy. On one hand, the target selection for an unbiased sample build-up is complicated by several types of peculiarities that can occur in individual objects. On the other hand, composite spectra are often not recognized as such even at medium-high spectral resolution and typical signal-to-noise ratios, despite multiplicity among massive stars is widespread. In particular, surveys that produce large amounts of automatically reduced data are prone to oversight of details that turn hazardous for the analysis with techniques that have been developed for a set of standard assumptions applicable to a spectrum of a single star. Much larger systematic errors than anticipated may therefore result because of the unrecognized true nature of the investigated objects, or much smaller sample sizes of objects for the analysis than initially planned, if recognized. More factors to be taken care of are the multiple steps from the choice of instrument over the details of the data reduction chain to the choice of modelling code, input data, analysis technique and the selection of the spectral lines to be analyzed. Only when avoiding all the possible pitfalls, a precise and accurate characterization of the stars in terms of fundamental parameters and chemical fingerprints can be achieved that form the basis for further investigations regarding e.g. stellar structure and evolution or the chemical evolution of the Galaxy. The scope of the present work is to provide the massive star and also other astrophysical communities with criteria to evaluate the quality of spectroscopic investigations of massive stars before interpreting them in a broader context. The discussion is guided by our experiences made in the course of over a decade of studies of massive star spectroscopy ranging from the simplest single objects to multiple systems.

Dual-conjugate adaptive optics for wide-field high-resolution retinal imaging.

PubMed

Thaung, Jörgen; Knutsson, Per; Popovic, Zoran; Owner-Petersen, Mette

2009-03-16

We present analysis and preliminary laboratory testing of a real-time dual-conjugate adaptive optics (DCAO) instrument for ophthalmology that will enable wide-field high resolution imaging of the retina in vivo. The setup comprises five retinal guide stars (GS) and two deformable mirrors (DM), one conjugate to the pupil and one conjugate to a plane close to the retina. The DCAO instrument has a closed-loop wavefront sensing wavelength of 834 nm and an imaging wavelength of 575 nm. It incorporates an array of collimator lenses to spatially filter the light from all guide stars using one adjustable iris, and images the Hartmann patterns of multiple reference sources on a single detector. Zemax simulations were performed at 834 nm and 575 nm with the Navarro 99 and the Liou- Brennan eye models. Two correction alternatives were evaluated; conventional single conjugate AO (SCAO, using one GS and a pupil DM) and DCAO (using multiple GS and two DM). Zemax simulations at 575 nm based on the Navarro 99 eye model show that the diameter of the corrected field of view for diffraction-limited imaging (Strehl >or= 0.8) increases from 1.5 deg with SCAO to 6.5 deg using DCAO. The increase for the less stringent condition of a wavefront error of 1 rad or less (Strehl >or= 0.37) is from 3 deg with SCAO to approximately 7.4 deg using DCAO. Corresponding results for the Liou-Brennan eye model are 3.1 deg (SCAO) and 8.2 deg (DCAO) for Strehl >or= 0.8, and 4.8 deg (SCAO) and 9.6 deg (DCAO) for Strehl >or= 0.37. Potential gain in corrected field of view with DCAO is confirmed both by laboratory experiments on a model eye and by preliminary in vivo imaging of a human eye. (c) 2009 Optical Society of America

Space Shuttle Star Tracker Challenges

NASA Technical Reports Server (NTRS)

Herrera, Linda M.

2010-01-01

The space shuttle fleet of avionics was originally designed in the 1970's. Many of the subsystems have been upgraded and replaced, however some original hardware continues to fly. Not only fly, but has proven to be the best design available to perform its designated task. The shuttle star tracker system is currently flying as a mixture of old and new designs, each with a unique purpose to fill for the mission. Orbiter missions have tackled many varied missions in space over the years. As the orbiters began flying to the International Space Station (ISS), new challenges were discovered and overcome as new trusses and modules were added. For the star tracker subsystem, the growing ISS posed an unusual problem, bright light. With two star trackers on board, the 1970's vintage image dissector tube (IDT) star trackers track the ISS, while the new solid state design is used for dim star tracking. This presentation focuses on the challenges and solutions used to ensure star trackers can complete the shuttle missions successfully. Topics include KSC team and industry partner methods used to correct pressurized case failures and track system performance.

Speckle interferometry at the OAN-SPM México: astrometry of double stars measured in 2011

NASA Astrophysics Data System (ADS)

Guerrero, C. A.; Orlov, V. G.; Borges Fernandes, M.; Ángeles, F.

2018-04-01

We present speckle interferometric measurements of binary stars performed during 2011 February and April with the 1.5-m telescope and during 2011 July and November with the 2.1-m telescope of the Observatorio Astronómico Nacional, San Pedro Mártir, México, focusing on objects from the Washington Double Star Catalog with separations less than 1 arcsec. Among these objects, we have been interested in performing a follow-up observation of new double stars discovered by Hipparcos. For these observations, we developed a new detector, which is a combination of CCD Watec 120N with a third generation image intensifier. This image intensifier allows us to perform near-infrared speckle interferometric observations for the first time. In this paper, we report 761 astrometric measurements of 478 pairs, with angular separations ranging from 0.09 to 2.61 arcsec. We found that 722 of our measured separations are smaller than 1 arcsec. We estimated a mean error in separation of 16 mas and 1.29° in position angle. In order to overcome the usual 180° ambiguity inherent to speckle measurements, we created a shift-and-add reconstructed image of each source, to establish the true quadrant of the secondary star. We confirmed 40 double stars discovered by Hipparcos and found 4 field stars resolved as interferometric pairs for the first time, with separations smaller than 0.60 arcsec.

(abstract) Realization of a Faster, Cheaper, Better Mission and Its New Paradigm Star Tracker, the Advanced Stellar Compass

NASA Technical Reports Server (NTRS)

Eisenman, Allan Read; Liebe, Carl Christian; Joergensen, John Lief; Jensen, Gunnar Bent

1997-01-01

The first Danish satellite, rsted, will be launched in August of 1997. The scientific objective of sted is to perform a precision mapping of the Earth's magnetic field. Attitude data for the payload and the satellite are provided by the Advanced Stellar Compass (ASC) star tracker. The ASC consists of a CCD star camera and a capable microprocessor which operates by comparing the star image frames taken by the camera to its internal star catalogs.

PROVIDING STRINGENT STAR FORMATION RATE LIMITS OF z ∼ 2 QSO HOST GALAXIES AT HIGH ANGULAR RESOLUTION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vayner, Andrey; Wright, Shelley A.; Do, Tuan

2016-04-10

We present integral field spectrograph (IFS) with laser guide star adaptive optics (LGS-AO) observations of z ∼ 2 quasi-stellar objects (QSOs) designed to resolve extended nebular line emission from the host galaxy. Our data was obtained with W. M. Keck and Gemini North Observatories, using OSIRIS and NIFS coupled with the LGS-AO systems, respectively. We have conducted a pilot survey of five QSOs, three observed with NIFS+AO and two observed with OSIRIS+AO at an average redshift of z = 2.2. We demonstrate that the combination of AO and IFSs provides the necessary spatial and spectral resolutions required to separate QSO emission from its host.more » We present our technique for generating a point-spread function (PSF) from the broad-line region of the QSO and performing PSF subtraction of the QSO emission to detect the host galaxy emission at a separation of ∼0.″2 (∼1.4 kpc). We detect Hα narrow-line emission for two sources, SDSS J1029+6510 (z{sub Hα} = 2.182) and SDSS J0925+0655 (z{sub Hα} = 2.197), that have evidence for both star formation and extended narrow-line emission. Assuming that the majority of narrow-line Hα emission is from star formation, we infer a star formation rate (SFR) for SDSS J1029+6510 of 78.4 M{sub ⊙} yr{sup −1} originating from a compact region that is kinematically offset by 290–350 km s{sup −1}. For SDSS J0925+0655 we infer a SFR of 29 M{sub ⊙} yr{sup −1} distributed over three clumps that are spatially offset by ∼7 kpc. The null detections on three of the QSOs are used to infer surface brightness limits and we find that at 1.4 kpc from the QSO the un-reddened star formation limit is ≲0.3 M{sub ⊙} yr{sup −1} kpc{sup −2}. If we assume typical extinction values for z = 2 type-1 QSOs, the dereddened SFR for our null detections would be ≲0.6 M{sub ⊙} yr{sup −1} kpc{sup −2}. These IFS observations indicate that while the central black hole is accreting mass at 10%–40% of the Eddington rate, if star formation is present in the host (1.4–20 kpc) it would have to occur diffusely with significant extinction and not in compact, clumpy regions.« less

Ancient Earth, Alien Earths Event

NASA Image and Video Library

2014-08-20

Dr. David H. Grinspoon, Senior Scientist, Planetary Science Institute, moderates a panel at the “Ancient Earth, Alien Earths” Event at NASA Headquarters in Washington, DC Wednesday, August 20, 2014. The event was sponsored by NASA, the National Science Foundation (NSF), and the Smithsonian Institution and highlighted how research on early Earth could help guide our search for habitable planets orbiting other stars. Photo Credit: (NASA/Aubrey Gemignani)

Wavefront control system for the Keck telescope

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brase, J. M., LLNL

1998-03-01

The laser guide star adaptive optics system currently being developed for the Keck 2 telescope consists of several major subsystems: the optical bench, wavefront control, user interface and supervisory control, and the laser system. The paper describes the design and implementation of the wavefront control subsystem that controls a 349 actuator deformable mirror for high order correction and tip-tilt mirrors for stabilizing the image and laser positions.

Standard Transistor Array (Star): SIMLOG/TESTGN programmer's guide, volume 2, addendum 2

NASA Technical Reports Server (NTRS)

Carroll, B. D.

1979-01-01

A brief introduction to the SIMLOG/TESTGN system of programs is given. SIMLOG is a logic simulation program, whereas TESTGN is a program for generating test sequences from output produced by SIMLOG. The structures of the two programs are described. Data base, main program, and subprogram details are also given. Guidelines for program modifications are discussed. Commented program listings are included.

Stargazing: an integrative conceptual review, theoretical reconciliation, and extension for star employee research.

PubMed

Call, Matthew L; Nyberg, Anthony J; Thatcher, Sherry M B

2015-05-01

Stars--employees with disproportionately high and prolonged (a) performance, (b) visibility, and (c) relevant social capital--have garnered attention in economics, sociology, and management. However, star research is often isolated within these research disciplines. Thus, 3 distinct star research streams are evolving, each disconnected from the others and each bringing siloed theoretical perspectives, terms, and assumptions. A conceptual review of these perspectives reveals a focus on the expost effects that stars exert in organizations with little explanation of who a star is and how one becomes a star. To synthesize the stars literature across these 3 disciplines, we apply psychological theories, specifically motivation theories, to create an integrative framework for stars research. Thus, we present a unified stars definition and extend theory on the making, managing, and mobility of stars. We extend research about how and why employees may be motivated to become stars, how best to manage stars and their relationships with colleagues, and how to motivate star retention. We then outline directions for future research. (c) 2015 APA, all rights reserved.

Novel views of the lithospheric magnetic field for hazard mitigation, tectonics, and geology

NASA Astrophysics Data System (ADS)

Purucker, M. E.; Blakely, R. J.; Nelson, J. B.; Bracken, R.; White, T.

2016-12-01

The altitude of magnetic field observations is critical for high-resolution mapping. We advocate two views of the lithospheric magnetic field, at altitudes of 20 and 90 km. Magnetic surveys are most sensitive to sources with wavelengths comparable to the altitude of the survey. Thus, low-altitude satellite surveys emphasize wavelengths greater than 300 km, such as subduction zones and the continent-ocean contrast. Magnetic sources elongated along satellite tracks are subdued, however, and lithospheric features are obscured in the auroral ovals around the magnetic poles. Near-surface surveys (0.1 to 5 km altitudes) are sensitive to tectonic and upper-crustal geologic sources. There are many under-explored regions, even in this near-surface realm, notably the Antarctic and the southern oceans. Few magnetic surveys are available between airborne ( 5 km) and orbital altitudes ( 300 km), and this lack of information reduces knowledge of geologic and tectonic features in this spectral band; e.g., sources associated with the lower crust or that encompass the whole crust are strongly suppressed because the average thickness of continental crust is 30 km. Technologies are being developed to acquire magnetic field information at suborbital altitudes with UAVs at altitudes of 20 km, and with a laser guide star technique for remote sensing at an altitude averaging 90 km. Use of the laser guide star technique on a polar-orbiting satellite with in-situ magnetometers would greatly facilitate separating ionospheric from lithospheric fields. Laser guide stars can be produced in Na-rich layers where micro-meteorite breakup occurs in a planetary or satellite system, and they are ubiquitous in the Solar System. The ideal observation platform at 20 km has small and well-characterized EM fields, can execute maneuvers that permit flying of tie lines, and can fly for long periods so as to survey large areas. A main limitation of surveying remote areas concerns the need for a local base station for resolving temporal-spatial aliasing. The traditional approach of siting temporary base stations in the survey area is often not feasible, and we discuss possible alternatives.

SEARCHING FOR YOUNG M DWARFS WITH GALEX

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shkolnik, Evgenya L.; Weinberger, Alycia J.; Liu, Michael C.

2011-01-20

The census of young moving groups in the solar neighborhood is significantly incomplete in the low-mass regime. We have developed a new selection process to find these missing members based on the Galaxy Evolution Explorer (GALEX) All-Sky Imaging Survey (AIS). For stars with spectral types {approx}>K5 (R - J {approx}> 1.5) and younger than {approx}300 Myr, we show that near-UV (NUV) and far-UV (FUV) emission is greatly enhanced above the quiescent photosphere, analogous to the enhanced X-ray emission of young low-mass stars seen by ROSAT but detectable to much larger distances with GALEX. By combining GALEX data with optical (HSTmore » Guide Star Catalog) and near-IR (2MASS) photometry, we identified an initial sample of 34 young M dwarf candidates in a 1000 deg{sup 2} region around the {approx}10 Myr TW Hydra Association (TWA). Low-resolution spectroscopy of 30 of these found 16 which had H{alpha} in emission, which were then followed up at high resolution to search for spectroscopic evidence of youth and to measure their radial velocities. Four objects have low surface gravities, photometric distances and space motions consistent with TWA, but the non-detection of Li indicates that they may be too old to belong to this moving group. One object (M3.5, 93 {+-} 19 pc) appears to be the first known accreting low-mass member of the {approx}15 Myr Lower Centaurus Crux OB association. Two objects exhibit all the characteristics of the known TWA members, and thus we designate them as TWA 31 (M4.2, 110 {+-} 11 pc) and TWA 32 (M6.3, 53 {+-} 5 pc). TWA 31 shows extremely broad (447 km s{sup -1}) H{alpha} emission, making it the sixth member of TWA found to have ongoing accretion. TWA 32 is resolved into a 0.''6 binary in Keck laser guide star adaptive optics imaging. Our search should be sensitive down to spectral types of at least M4-M5 in TWA and thus the small numbers of new member is puzzling. This might indicate TWA has an atypical mass function or that the presence of lithium absorption may be too restrictive a criteria for selecting young low-mass stars.« less

Capabilities of a Laser Guide Star for a Large Segmented Space Telescope

NASA Astrophysics Data System (ADS)

Clark, James R.; Carlton, Ashley; Douglas, Ewan S.; Males, Jared R.; Lumbres, Jennifer; Feinberg, Lee; Guyon, Olivier; Marlow, Weston; Cahoy, Kerri L.

2018-01-01

Large segmented mirror telescopes are planned for future space telescope missions such as LUVOIR (Large UV Optical Infrared Surveyor) to enable the improvement in resolution and contrast necessary to directly image Earth-like exoplanets, in addition to making contributions to general astrophysics. The precision surface control of these complex, large optical systems, which may have over a hundred meter-sized segments, is a challenge. Our initial simulations show that imaging a star of 2nd magnitude or brighter with a Zernike wavefront sensor should relax the segment stability requirements by factors between 10 and 50 depending on the wavefront control strategy. Fewer than fifty stars brighter than magnitude 2 can be found in the sky. A laser guide star (LGS) on a companion spacecraft will allow the telescope to target a dimmer science star and achieve wavefront control to the required stability without requiring slew or repointing maneuvers.We present initial results for one possible mission architecture, with a LGS flying at 100,000 km range from the large telescope in an L2 halo orbit, using a laser transmit power of <10 W. We also discuss orbital dynamics and propulsion options for a LGS. Our initial analysis in MATLAB simulations finds that the telescope-LGS vector can be held anywhere on the sky for extended durations (>8 days) for an expenditure of <10 m/s of delta-V per day, or an average thrust <1 mN for a satellite of mass <47 kg. If the LGS uses a low-thrust electric propulsion system, it can be accommodated in a 6U CubeSat bus, but may require an extended period of time to transition between targets and match velocities with the telescope (e.g. 6 days to transit 10 degrees). If the LGS uses monopropellant propulsion, it must use at least a 27U bus to achieve the the same delta-V capability, but can transition between targets much more rapidly (<1 day to transit 10 degrees).Architecture trades on formation flying distance, laser wavelength and power are ongoing. The models of the segments and their disturbances and of the formation flight are being refined. A low-cost prototype mission (e.g. between a small satellite in LEO and an LGS in GEO) to validate the feasibility is in development.

Effects of star-shape poly(alkyl methacrylate) arm uniformity on lubricant properties

DOE PAGES

Robinson, Joshua W.; Qu, Jun; Erck, Robert; ...

2016-03-29

Star-shaped poly(alkyl methacrylate)s (PAMAs) were prepared and blended into an additive-free engine oil to assess the structure property relationship between macromolecular structure and lubricant performance. These additives were designed with a comparable number of repeating units per arm and the number of arms was varied between 3 and 6. Well-defined star-shaped PAMAs were synthesized by atom transfer radical polymerization (ATRP) via a core-first strategy from multi-functional headgroups. Observations of the polymer-oil blends suggest that stars with less than four arms are favorable as a viscosity index improver (VII), and molecular weight dominates viscosity-related effects over other structural features. Star-shaped PAMAs,more » as oil additives, effectively reduce the friction coefficient in both mixed and boundary lubrication regime. Several analogs outperformed commercial VIIs in both viscosity and friction performance. Furthermore, increased wear rates were observed for these star-shaped PAMAs in the boundary lubrication regime suggesting pressure-sensitive conformations may exist.« less

Colloquium: Measuring the neutron star equation of state using x-ray timing

DOE PAGES

Watts, Anna L.; Andersson, Nils; Chakrabarty, Deepto; ...

2016-04-13

One of the primary science goals of the next generation of hard x-ray timing instruments is to determine the equation of state of matter at supranuclear densities inside neutron stars by measuring the radius of neutron stars with different masses to accuracies of a few percent. Three main techniques can be used to achieve this goal. The first involves waveform modeling. The flux observed from a hotspot on the neutron star surface offset from the rotational pole will be modulated by the star s rotation, and this periodic modulation at the spin frequency is called a pulsation. As the photonsmore » propagate through the curved spacetime of the star, information about mass and radius is encoded into the shape of the waveform (pulse profile) via special and general-relativistic effects. Using pulsations from known sources (which have hotspots that develop either during thermo- nuclear bursts or due to channeled accretion) it is possible to obtain tight constraints on mass and radius. The second technique involves characterizing the spin distribution of accreting neutron stars. A large collecting area enables highly sensitive searches for weak or intermittent pulsations (which yield spin) from the many accreting neutron stars whose spin rates are not yet known. The most rapidly rotating stars provide a clean constraint, since the limiting spin rate where the equatorial surface velocity is comparable to the local orbital velocity, at which mass shedding occurs, is a function of mass and radius. However, the overall spin distribution also provides a guide to the torque mechanisms in operation and the moment of inertia, both of which can depend sensitively on dense matter physics. The third technique is to search for quasiperiodic oscillations in x-ray flux associated with global seismic vibrations of magnetars (the most highly magnetized neutron stars), triggered by magnetic explosions. The vibrational frequencies depend on stellar parameters including the dense matter equation of state, and large-area x-ray timing instruments would provide much improved detection capability. In addition, an illustration is given of how these complementary x-ray timing techniques can be used to constrain the dense matter equation of state and the results that might be expected from a 10 m 2 instrument are discussed. Also discussed are how the results from such a facility would compare to other astronomical investigations of neutron star properties.« less

Colloquium: Measuring the neutron star equation of state using x-ray timing

NASA Astrophysics Data System (ADS)

Watts, Anna L.; Andersson, Nils; Chakrabarty, Deepto; Feroci, Marco; Hebeler, Kai; Israel, Gianluca; Lamb, Frederick K.; Miller, M. Coleman; Morsink, Sharon; Özel, Feryal; Patruno, Alessandro; Poutanen, Juri; Psaltis, Dimitrios; Schwenk, Achim; Steiner, Andrew W.; Stella, Luigi; Tolos, Laura; van der Klis, Michiel

2016-04-01

One of the primary science goals of the next generation of hard x-ray timing instruments is to determine the equation of state of matter at supranuclear densities inside neutron stars by measuring the radius of neutron stars with different masses to accuracies of a few percent. Three main techniques can be used to achieve this goal. The first involves waveform modeling. The flux observed from a hotspot on the neutron star surface offset from the rotational pole will be modulated by the star's rotation, and this periodic modulation at the spin frequency is called a pulsation. As the photons propagate through the curved spacetime of the star, information about mass and radius is encoded into the shape of the waveform (pulse profile) via special and general-relativistic effects. Using pulsations from known sources (which have hotspots that develop either during thermonuclear bursts or due to channeled accretion) it is possible to obtain tight constraints on mass and radius. The second technique involves characterizing the spin distribution of accreting neutron stars. A large collecting area enables highly sensitive searches for weak or intermittent pulsations (which yield spin) from the many accreting neutron stars whose spin rates are not yet known. The most rapidly rotating stars provide a clean constraint, since the limiting spin rate where the equatorial surface velocity is comparable to the local orbital velocity, at which mass shedding occurs, is a function of mass and radius. However, the overall spin distribution also provides a guide to the torque mechanisms in operation and the moment of inertia, both of which can depend sensitively on dense matter physics. The third technique is to search for quasiperiodic oscillations in x-ray flux associated with global seismic vibrations of magnetars (the most highly magnetized neutron stars), triggered by magnetic explosions. The vibrational frequencies depend on stellar parameters including the dense matter equation of state, and large-area x-ray timing instruments would provide much improved detection capability. An illustration is given of how these complementary x-ray timing techniques can be used to constrain the dense matter equation of state and the results that might be expected from a 10 m2 instrument are discussed. Also discussed are how the results from such a facility would compare to other astronomical investigations of neutron star properties.

Brownian Motion in a Speckle Light Field: Tunable Anomalous Diffusion and Selective Optical Manipulation

PubMed Central

Volpe, Giorgio; Volpe, Giovanni; Gigan, Sylvain

2014-01-01

The motion of particles in random potentials occurs in several natural phenomena ranging from the mobility of organelles within a biological cell to the diffusion of stars within a galaxy. A Brownian particle moving in the random optical potential associated to a speckle pattern, i.e., a complex interference pattern generated by the scattering of coherent light by a random medium, provides an ideal model system to study such phenomena. Here, we derive a theory for the motion of a Brownian particle in a speckle field and, in particular, we identify its universal characteristic timescale. Based on this theoretical insight, we show how speckle light fields can be used to control the anomalous diffusion of a Brownian particle and to perform some basic optical manipulation tasks such as guiding and sorting. Our results might broaden the perspectives of optical manipulation for real-life applications. PMID:24496461

Timing characterization and analysis of the Linux-based, closed loop control computer for the Subaru Telescope laser guide star adaptive optics system

NASA Astrophysics Data System (ADS)

Dinkins, Matthew; Colley, Stephen

2008-07-01

Hardware and software specialized for real time control reduce the timing jitter of executables when compared to off-the-shelf hardware and software. However, these specialized environments are costly in both money and development time. While conventional systems have a cost advantage, the jitter in these systems is much larger and potentially problematic. This study analyzes the timing characterstics of a standard Dell server running a fully featured Linux operating system to determine if such a system would be capable of meeting the timing requirements for closed loop operations. Investigations are preformed on the effectiveness of tools designed to make off-the-shelf system performance closer to specialized real time systems. The Gnu Compiler Collection (gcc) is compared to the Intel C Compiler (icc), compiler optimizations are investigated, and real-time extensions to Linux are evaluated.

Modernizing Pickles - A Tool for Planning and Scheduling HST Astrometry

NASA Astrophysics Data System (ADS)

Juarez, Aaron; McArthur, B.; Benedict, G. F.

2007-12-01

Pickles is a Macintosh program written in C that was developed as a tool for determining pointings and rolls of the Hubble Space Telescope (HST) to place targets and astrometric reference stars in the Fine Guidance Sensor (FGS) field of regard ("pickles"). The program was developed in the late 1980s and runs under the "Classic” System. Ongoing HST astrometry projects require that this code be ported to the Intel-Mac OSX, because the Classic System is now unsupported. Pickles is a vital part of HST astrometry research. It graphically aids the investigator to determine where, when, and how the HST/FGS combination can observe an object and associated astrometric reference stars. Presently, Pickles can extract and display star positions from Guide Star Catalogs, such as the ACRS, SAO, and AGK3 catalogs via CD-ROMs. Future improvements will provide access to these catalogs and others through the internet. As an example of the past utility of Pickles, we highlight the recent determination of parallaxes for ten galactic Cepheids to determine an improved solar-metallicity Period-Luminosity relation. Support for this work was provided by NASA through grants GO-10989, -11210, and -11211 from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.

Research on Spectroscopy, Opacity, and Atmospheres

NASA Technical Reports Server (NTRS)

Oliversen, Ronald (Technical Monitor); Kurucz, Robert L.

2004-01-01

I propose to continue providing observers with basic data for interpreting spectra from stars, novas, supernovas, clusters, and galaxies. These data will include allowed forbidden line lists both laboratory and computed, for the first five to ten ions of all atoms and for all relevant diatomic molecules. I will eventually expend to all ions of the first thirty elements to treat far UV end X-ray spectra, and for envelope opacities. I also include triatomic molecules providing by other researchers. I have made CDs with Partridge and Schwanke's water data for work on M stars.The luna data also serve as input to my model atmosphere and synthesis programs that generated energy distributions, photometry, limb darkening, and spectra that can be used for planning observations and for fitting observed spectra. The spectrum synthesis programs produce detailed plots with the line identified. Grids of stellar spectra can be used for radial velocity-, rotation-, or abundance templates and for population synthesis. I am fitting spectra of bright stars to test the data and to produce atlases to guide observer. For each star the whole spectrum is computed from the UV to the far IR. The line data, opacities, models, spectra, and programs are freely distributed on CDs and on my web site and represent a unique resource for many NASA programs.

Comparison between Euro NCAP test results and real-world crash data.

PubMed

Kullgren, Anders; Lie, Anders; Tingvall, Claes

2010-12-01

The objective of this study was 2-fold: first, to compare Euro NCAP safety ratings of cars with those published by the Folksam real-world injury ratings; and second, to compare injury risk measures between Euro NCAP 2 and 5 Star cars with real-world injury and disability outcomes using police and insurance injury data. Car models were grouped according to the Euro NCAP star rating scores. Folksam risk of injury ratings come from statistical analysis of real-world crashes using police and insurance databases. The paired comparison method using 2-car crashes was used to control for crash speed and the mass differences between cars of different weights were normalized. For all comparisons, 5-star rated Euro NCAP cars were found to have a lower risk of injury compared to 2-star rated cars (5-star cars were 10% ± 2.5% lower risk than 2-star cars). For fatal and serious injuries, the difference was 23 ± 8 percent, and for fatal injuries alone the difference was 68 ± 32 percent. By comparison, the Folksam 5-star rated cars had a relative risk of 0.020 ± 0.0024, whereas 2-star rated car risk was 0.028 ± 0.0016, corresponding to a 27 percent difference in risk between 5- and 2-star cars. Good correlation was found between Euro NCAP test results and real-world injury outcomes. The largest difference in injury risk between 2- and 5-star rated cars in Euro NCAP was found for risk of fatality, confirming that car manufacturers have focused their safety performance on serious crash outcomes. In addition, Euro NCAP crash tests were shown to be highly correlated with serious crash performance, confirming their relevance for evaluating real-world crash performance. Good concordance was found between Euro NCAP and Folksam real-world crash and injury ratings.

Interpretive front-of-pack nutrition labels. Comparing competing recommendations.

PubMed

Maubach, Ninya; Hoek, Janet; Mather, Damien

2014-11-01

Many stakeholders support introducing an interpretive front-of-pack (FOP) nutrition label, but disagree over the form it should take. In late 2012, an expert working group established by the New Zealand government recommended the adoption of an untested summary rating system: a Star label. This study used a best-worst scaling choice experiment to estimate how labels featuring the new Star rating, the Multiple Traffic Light (MTL), Daily Intake Guide (DIG), and a no-FOP control affected consumers' choice behaviours and product perceptions. Nutrient-content and health claims were included in the design. We also assessed whether respondents who used more or less information during the choice tasks differed in their selection patterns. Overall, while respondents made broadly similar choices with respect to the MTL and Star labels, the MTL format had a significantly greater impact on depressing preference as a food's nutritional profile became less healthy. Health claims increased rankings of less nutritious options, though this effect was less pronounced when the products featured an MTL. Further, respondents were best able to differentiate products' healthiness with MTL labels. The proposed summary Stars system had less effect on choice patterns than an MTL label and our findings highlight the need for policy makers to ensure that decisions to introduce FOP labels are underpinned by robust research evidence. These results suggest that the proposed summary Stars system will have less effect on shifting food choice patterns than interpretive FOP nutrition label featuring traffic light ratings. Copyright © 2014 Elsevier Ltd. All rights reserved.

Here Be Dragons: Characterization of ACS/WFC Scattered Light Anomalies

NASA Astrophysics Data System (ADS)

Porterfield, B.; Coe, D.; Gonzaga, S.; Anderson, J.; Grogin, N.

2016-11-01

We present a study characterizing scattered light anomalies that occur near the edges of Advanced Camera for Surveys (ACS) Wide Field Channel (WFC) images. We inspected all 8,573 full-frame ACS/WFC raw images with exposure times longer than 350 seconds obtained in the F606W and F814W filters from 2002 to October 2013. We visually identified two particular scattered light artifacts known as "dragon's breath" and edge glow. Using the 2MASS point source catalog and Hubble Guide Star Catalog (GSC II), we identified the stars that caused these artifacts. The stars are all located in narrow bands ( 3" across) just outside the ACS/WFC field of view (2" - 16" away). We provide a map of these risky areas around the ACS/WFC detectors - users should avoid positioning bright stars in these regions when designing ACS/WFC imaging observations. We also provide interactive webpages which display all the image artifacts we identified, allowing users to see examples of the severity of artifacts they might expect for a given stellar magnitude at a given position relative to the ACS/WFC field of view. On average, 10th (18th) magnitude stars produce artifacts about 1,000 (100) pixels long. But the severity of these artifacts can vary strongly with small positional shifts (∼ 1"). The results are similar for both filters (F606W and F814W) when expressed in total fluence, or flux multiplied by exposure time.

Doubly differential star-16-QAM for fast wavelength switching coherent optical packet transceiver.

PubMed

Liu, Fan; Lin, Yi; Walsh, Anthony J; Yu, Yonglin; Barry, Liam P

2018-04-02

A coherent optical packet transceiver based on doubly differential star 16-ary quadrature amplitude modulation (DD-star-16-QAM) is presented for spectrally and energy efficient reconfigurable networks. The coding and decoding processes for this new modulation format are presented, simulations and experiments are then performed to investigate the performance of the DD-star-16-QAM in static and dynamic scenarios. The static results show that the influence of frequency offset (FO) can be cancelled out by doubly differential (DD) coding and the correction range is only limited by the electronic bandwidth of the receivers. In the dynamic scenario with a time-varying FO and linewidth, the DD-star-16-QAM can overcome the time-varying FO, and the switching time of around 70 ns is determined by the time it takes the dynamic linewidth to reach the requisite level. This format can thus achieve a shorter waiting time after switching tunable lasers than the commonly used square-16-QAM, in which the transmission performance is limited by the frequency transients after the wavelength switch.

General relativistic viscous hydrodynamics of differentially rotating neutron stars

NASA Astrophysics Data System (ADS)

Shibata, Masaru; Kiuchi, Kenta; Sekiguchi, Yu-ichiro

2017-04-01

Employing a simplified version of the Israel-Stewart formalism for general-relativistic shear-viscous hydrodynamics, we perform axisymmetric general-relativistic simulations for a rotating neutron star surrounded by a massive torus, which can be formed from differentially rotating stars. We show that with our choice of a shear-viscous hydrodynamics formalism, the simulations can be stably performed for a long time scale. We also demonstrate that with a possibly high shear-viscous coefficient, not only viscous angular momentum transport works but also an outflow could be driven from a hot envelope around the neutron star for a time scale ≳100 ms with the ejecta mass ≳10-2 M⊙ , which is comparable to the typical mass for dynamical ejecta of binary neutron-star mergers. This suggests that massive neutron stars surrounded by a massive torus, which are typical outcomes formed after the merger of binary neutron stars, could be the dominant source for providing neutron-rich ejecta, if the effective shear viscosity is sufficiently high, i.e., if the viscous α parameter is ≳10-2. The present numerical result indicates the importance of a future high-resolution magnetohydrodynamics simulation that is the unique approach to clarify the viscous effect in the merger remnants of binary neutron stars by the first-principle manner.

Fundamental limits on isoplanatic correction with multiconjugate adaptive optics

NASA Astrophysics Data System (ADS)

Lloyd-Hart, Michael; Milton, N. Mark

2003-10-01

We investigate the performance of a general multiconjugate adaptive optics (MCAO) system in which signals from multiple reference beacons are used to drive several deformable mirrors in the optical beam train. Taking an analytic approach that yields a detailed view of the effects of low-order aberration modes defined over the metapupil, we show that in the geometrical optics approximation, N deformable mirrors conjugated to different ranges can be driven to correct these modes through order N with unlimited isoplanatic angle, regardless of the distribution of turbulence along the line of sight. We find, however, that the optimal deformable mirror shapes are functions of target range, so the best compensation for starlight is in general not the correction that minimizes the wave-front aberration in a laser guide beacon. This introduces focal anisoplanatism in the wave-front measurements that can be overcome only through the use of beacons at several ranges. We derive expressions for the number of beacons required to sense the aberration to arbitrary order and establish necessary and sufficient conditions on their geometry for both natural and laser guide stars. Finally, we derive an expression for the residual uncompensated error by mode as a function of field angle, target range, and MCAO system geometry.

A Toolbox for Exoplanet Exploration

NASA Astrophysics Data System (ADS)

Jensen-Clem, Rebecca Marie

2017-05-01

In this thesis, I develop a new suite of tools to address two questions in exoplanet science: how common are Earth-mass planets in the habitable zones of Solar-type stars, and can we detect signs of life on other worlds? Answering the first question requires a method for detecting Earth-Sun analogs. Currently, the radial velocity (RV) method of exoplanet detection is one of the most successful tools for probing inner planetary systems. However, degeneracy between a spectrometer's wavelength calibration and the astrophysical RV shift has limited the sensitivity of today's instruments. In my thesis, I address a method for breaking this degeneracy: by combining a traditional spectrometer design with a dynamic interferometer, a fringe pattern is generated at the image plane that is highly sensitive to changes in the radial velocity of the target star. I augmented previous theoretical studies of the method, creating an end-to-end simulation to 1) introduce and recover wavelength calibration errors, and 2) investigate the effects of interferometer position errors on the RV precision. My simulation showed that using this kind of interferometric system, a 5-m class telescope could detect an Earth-Sun analog. Addressing the occurrence rate of Earth twins also requires an understanding of planet formation in multiple star systems, which encompass half of all Solar-type stars. Gravitational interactions between binary components separated by 10-100 astronomical units are predicted to truncate the outer edges of their respective disks, possibly reducing the disks' lifetimes. Consequently, the pool of material and the amount of time available for planet formation may be smaller than in single star systems. The stars' rotational periods provide a fossil record of these events: star-disk magnetic interactions initially prevent a contracting pre-main sequence star from spinning up, and hence a star with a shorter-lived disk is expected to be spinning more quickly when it reaches the zero age main sequence. In order to conduct a large-scale multiplicity survey to investigate the relationship between stellar rotation and binary system properties (e.g. their separations and mass ratios), I contributed to the commissioning of Robo-AO, a robotic laser guide star adaptive optics system, at the Kitt Peak 2.1-m. After the instrument's installation, I wrote a data pipeline to optimize the system's sensitivity to close stellar companions via reference star differential imaging. I then characterized Robo-AO's performance during its first year of operations. Finally, I used Robo-AO to search for binaries among the 759 stars in the Pleiades with rotational periods measured using the photometric data of the re-purposed Kepler telescope, K2. Detecting signs of life on other worlds will require detailed characterization of rocky exoplanet atmospheres. Polarimetry has long been proposed as a means of probing these atmospheres, but current instruments lack the sensitivity to detect the starlight reflected and polarized by such small, close-in planets. However, the latest generation of high contrast imaging instruments (e.g. GPI and SPHERE) may be able to detect the polarization of thermal emission by young gas giants due to scattering by aerosols in their atmospheres. Observational constraints on the details of clouds physics imposed by polarized emission will improve our understanding of the planets' compositions, and hence their formation histories. For the case of the brown dwarf HD19467 B orbiting a nearby Sun-like star, I demonstrated that the Gemini Planet Imager can detect linear polarizations on the order predicted for these cloudy exoplanets. My current pilot programs can produce the first detections of polarized exoplanet emission, while also building expertise for reflected starlight polarimetry with future observatories.

Cost-Effectiveness of a Clinical Childhood Obesity Intervention.

PubMed

Sharifi, Mona; Franz, Calvin; Horan, Christine M; Giles, Catherine M; Long, Michael W; Ward, Zachary J; Resch, Stephen C; Marshall, Richard; Gortmaker, Steven L; Taveras, Elsie M

2017-11-01

To estimate the cost-effectiveness and population impact of the national implementation of the Study of Technology to Accelerate Research (STAR) intervention for childhood obesity. In the STAR cluster-randomized trial, 6- to 12-year-old children with obesity seen at pediatric practices with electronic health record (EHR)-based decision support for primary care providers and self-guided behavior-change support for parents had significantly smaller increases in BMI than children who received usual care. We used a microsimulation model of a national implementation of STAR from 2015 to 2025 among all pediatric primary care providers in the United States with fully functional EHRs to estimate cost, impact on obesity prevalence, and cost-effectiveness. The expected population reach of a 10-year national implementation is ∼2 million children, with intervention costs of $119 per child and $237 per BMI unit reduced. At 10 years, assuming maintenance of effect, the intervention is expected to avert 43 000 cases and 226 000 life-years with obesity at a net cost of $4085 per case and $774 per life-year with obesity averted. Limiting implementation to large practices and using higher estimates of EHR adoption improved both cost-effectiveness and reach, whereas decreasing the maintenance of the intervention's effect worsened the former. A childhood obesity intervention with electronic decision support for clinicians and self-guided behavior-change support for parents may be more cost-effective than previous clinical interventions. Effective and efficient interventions that target children with obesity are necessary and could work in synergy with population-level prevention strategies to accelerate progress in reducing obesity prevalence. Copyright © 2017 by the American Academy of Pediatrics.

Developing internet-based eHealth promotion programs: the Spiral Technology Action Research (STAR) model.

PubMed

Skinner, Harvey A; Maley, Oonagh; Norman, Cameron D

2006-10-01

Health education and health promotion have a tradition of using information and communication technology (ICT). In recent years, the rapid growth of the Internet has created innovative opportunities for Web-based health education and behavior change applications-termed eHealth promotion. However, many eHealth promotion applications are developed without an explicit model to guide the design, evaluation, and ongoing improvement of the program. The spiral technology action research (STAR) model was developed to address this need. The model comprises five cycles (listen, plan, do, study, act) that weave together technological development, community involvement, and continuous improvement. The model is illustrated by a case study describing the development of the Smoking Zine (www.SmokingZine.org), a youth smoking prevention and cessation Web site.

NASA's Astro-Venture Engages Exceptional Students in Earth System Science Using Inquiry

NASA Astrophysics Data System (ADS)

Oguinn, C.

2003-12-01

Astro-Venture is an educational, interactive, multimedia Web environment highlighting NASA careers and astrobiology research in the areas of Astronomy, Geology, Biology and Atmospheric Sciences. Students in grades 5-8 role-play NASA careers, as they search for and design a planet with the necessary characteristics for human habitation. Astro-Venture uses online multimedia activities and off-line inquiry explorations to engage students in guided inquiry aligned with the 5 E inquiry model. This model has proven to be effective with exceptional students. Students are presented with the intellectual confrontation of how to design a planet and star system that would be able to meet their biological survival needs. This provides a purpose for the online and off-line explorations used throughout the site. Students first explore "what" conditions are necessary to support human habitability by engaging in multimedia training modules, which allow them to change astronomical, atmospheric, geological and biological aspects of the Earth and our star system and to view the effects of these changes on Earth. By focusing on Earth, students draw on their prior knowledge, which helps them to connect their new knowledge to their existing schema. Cause and effect relationships of Earth provide a concrete model from which students can observe patterns and generalize abstract results to an imagined planet. From these observations, students draw conclusions about what aspects allowed Earth to remain habitable. Once students have generalized needed conditions of "what" we need for a habitable planet, they conduct further research in off-line, standards-based classroom activities that also follow the inquiry model and help students to understand "why" we need these conditions. These lessons focus on standards-based concepts such as states of matter and the structure and movement of the Earth's interior. These lessons follow the inquiry structure commonly referred to as the five E's as follows: Engage: Draws on students' prior knowledge, builds on previous lesson concepts, introduces the purpose of the lesson and the scientific question which is the problem or intellectual confrontation they will explore. Explore: Students form hypotheses and conduct an exploration that will help them to collect data and evidence to answer the scientific question. Explain: Students reflect on the explore activity by recording their results and conclusions. They participate in guided discussions or activities that help to guide their understanding of the concepts. Extend/Apply: Students demonstrate their understanding of the concept and/or apply it to another situation. Evaluate: Students are evaluated on their understanding of the concept often using rubrics. After students have mastered the "whats" and "whys," they engage in multimedia mission modules that simulate "how" scientists might search for a planet and star system that meets these requirements using the inquiry process. Students are first asked to hypothesize the likelihood of finding a star system that meets these requirements. They then simulate the methods scientists might use to collect data on various stars and planets to deduce whether the star system meets the requirements for habitability or not. After collecting and analyzing this data, students are asked to draw conclusions in comparing their results to their initial hypothesis. Students apply all that they've learned to design a planet that meets the requirements for human habitability in all areas. Through this process, they learn that Earth works as a system in meeting our needs.

Nebraska STARS: Achieving Results

ERIC Educational Resources Information Center

Roschewski, Pat; Isernhagen, Jody; Dappen, Leon

2006-01-01

In 2000, the state of Nebraska passed legislation requiring the assessment of student performance on content standards, but its requirements were very different from those of any other state. Nebraska created what has come to be known as STARS (School-based Teacher-led Assessment and Reporting System). Under STARS, each of Nebraska's nearly 500…

Autonomous star sensor ASTRO APS: flight experience on Alphasat

NASA Astrophysics Data System (ADS)

Schmidt, U.; Fiksel, T.; Kwiatkowski, A.; Steinbach, I.; Pradarutti, B.; Michel, K.; Benzi, E.

2015-06-01

Jena-Optronik GmbH, located in Jena/Germany, has profound experience in designing and manufacturing star trackers since the early 80s. Today the company has a worldwide leading position in supplying geo-stationary and Earth observation satellites with robust and reliable star tracker systems. In the first decade of the new century Jena-Optronik received a development contract (17317/2003/F/WE) from the European Space Agency to establish the technologically challenging elements for which advanced star tracker technologies as CMOS Active Pixel Sensors were being introduced or were considered strategic. This activity was performed in the frame of the Alphabus large platform pre-development lead by ESA and the industrial Joint Project Team consisting of Astrium (now Airbus Defence and Space), Thales Alenia Space and CNES (Centre national d'études spatiales). The new autonomous star tracker, ASTRO APS (Active Pixel Sensor), extends the Jena-Optronik A stro-series CCD-based star tracker products taken the full benefit of the CMOS APS technology. ASTRO APS is a fully autonomous compact star tracker carrying either the space-qualified radiation hard STAR1000 or the HAS2 APS detectors. The star tracker is one of four Technology Demonstration Payloads (TDP6) carried by Alphasat as hosted payload in the frame of a successful Private Public Partnership between ESA and Inmarsat who owns and operates the satellite as part of its geo-stationary communication satellites fleet. TDP6 supports also directly TDP1, a Laser Communication Terminal, for fine pointing tasks. Alphasat was flawlessly brought in orbit at the end of July 2013 by a European Ariane 5 launcher. Only a few hours after launch the star tracker received its switch ON command and acquired nominally within 6 s the inertial 3-axes attitude. In the following days of the early in-orbit operations of Alphasat the TDP6 unit tracked reliably all the spacecraft maneuvers including the 0.1 and 0.2°/s spin stabilization for Sun pointing, all of the apogee engine thrusts, Moon field of view transits and recovered to stable tracking after several Earth and Sun blindings before the spacecraft entered a preliminary Earth pointing in a nominal geo-stationary attitude. The Jena-Optronik TDP6 operation center received daily the star tracker status and attitude data. The huge amount of acquired raw data has been evaluated to characterize the ASTRO APS (STAR1000) star tracker in-orbit performance. The paper will present in detail these data processing activities and will show the extraordinary good results. Due to the diverse transfer orbit satellite operations the key performance star tracker data like attitude random noise, single star noise, star brightness measurement, baffle Sun exclusion angle, temperature control, etc., could be derived and have been compared to the ground based laboratory and field measurements. The ultimate performance parameters achieved and verified as well as the lessons learned from the comparison to the ground test data are summarized in the conclusion of the paper.

Nano-JASMINE: cosmic radiation degradation of CCD performance and centroid detection

NASA Astrophysics Data System (ADS)

Kobayashi, Yukiyasu; Shimura, Yuki; Niwa, Yoshito; Yano, Taihei; Gouda, Naoteru; Yamada, Yoshiyuki

2012-09-01

Nano-JASMINE (NJ) is a very small astrometry satellite project led by the National Astronomical Observatory of Japan. The satellite is ready for launch, and the launch is currently scheduled for late 2013 or early 2014. The satellite is equipped with a fully depleted CCD and is expected to perform astrometry observations for stars brighter than 9 mag in the zw-band (0.6 µm-1.0 µm). Distances of stars located within 100 pc of the Sun can be determined by using annual parallax measurements. The targeted accuracy for the position determination of stars brighter than 7.5 mag is 3 mas, which is equivalent to measuring the positions of stars with an accuracy of less than one five-hundredth of the CCD pixel size. The position measurements of stars are performed by centroiding the stellar images taken by the CCD that operates in the time and delay integration mode. The degradation of charge transfer performance due to cosmic radiation damage in orbit is proved experimentally. A method is then required to compensate for the effects of performance degradation. One of the most effective ways of achieving this is to simulate observed stellar outputs, including the effect of CCD degradation, and then formulate our centroiding algorithm and evaluate the accuracies of the measurements. We report here the planned procedure to simulate the outputs of the NJ observations. We also developed a CCD performance-measuring system and present preliminary results obtained using the system.

Mini-STAR as bail-out strategy for percutaneous coronary intervention of chronic total occlusion.

PubMed

Galassi, Alfredo Ruggero; Tomasello, Salvatore Davide; Costanzo, Luca; Campisano, Maria Barbara; Barrano, Giombattista; Ueno, Masafumi; Tello-Montoliu, Antonio; Tamburino, Corrado

2012-01-01

Although the advancement of the equipment and the presence of innovative techniques, percutaneous coronary intervention (PCI) for chronic total occlusion (CTO) continues to be affected by lower procedural success in comparison with non occluded vessel PCI. We describe a new technique for the treatment of coronary CTO which utilizes a new generation of polymeric wires. From March 2009 to June 2010 different strategies were adopted as "bail out" after an initial attempt failed in 117 consecutive CTO lesions. Among these, conventional strategies (CS) such as parallel wire, sub-intimal tracking and re-entry (STAR), microchannel technique, intracoronary ultrasound guided revascularization and anchor balloon, were used in 75 cases (64.1%), while in the remaining a new technique, the "mini-STAR," was used (39.9%). Although no substantial differences were observed regarding the distribution of clinical features and angiographic lesions characteristics between the populations, mini-STAR was able to achieve a higher rate of procedural success in comparison with other CS (97.6% vs. 52%, P < 0.001) with lower contrast agent use (442 ± 259 cm(3) vs. 561 ± 243 cm(3), P = 0.01) and shorter procedural and fluoroscopy times (122 ± 61 vs. 157 ± 74 min, P = 0.009 and 60 ± 31 min vs. 75 ± 38 min, P = 0.03, respectively). No differences were observed in term of peri-procedural complications such as procedural myocardial infarction, coronary perforations, and contrast-induced nephropathy between mini-STAR and CS. The mini-STAR technique is a promising strategy for the treatment of CTO lesions, achieving a high procedural success rate and low occurrence of procedural adverse events. Copyright © 2011 Wiley Periodicals, Inc.

IRAS variables as galactic structure tracers - Classification of the bright variables

NASA Technical Reports Server (NTRS)

Allen, L. E.; Kleinmann, S. G.; Weinberg, M. D.

1993-01-01

The characteristics of the 'bright infrared variables' (BIRVs), a sample consisting of the 300 brightest stars in the IRAS Point Source Catalog with IRAS variability index VAR of 98 or greater, are investigated with the purpose of establishing which of IRAS variables are AGB stars (e.g., oxygen-rich Miras and carbon stars, as was assumed by Weinberg (1992)). Results of the analysis of optical, infrared, and microwave spectroscopy of these stars indicate that, out of 88 stars in the BIRV sample identified with cataloged variables, 86 can be classified as Miras. Results of a similar analysis performed for a color-selected sample of stars, using the color limits employed by Habing (1988) to select AGB stars, showed that, out of 52 percent of classified stars, 38 percent are non-AGB stars, including H II regions, planetary nebulae, supergiants, and young stellar objects, indicating that studies using color-selected samples are subject to misinterpretation.

Composite measures for profiling hospitals on bariatric surgery performance

PubMed Central

Dimick, Justin B.; Birkmeyer, Nancy J.; Finks, Jonathan F.; Share, David A.; English, Wayne J.; Carlin, Arthur M.; Birkmeyer, John D.

2014-01-01

Objective We sought to develop a novel composite measure for profiling hospital performance with bariatric surgery. Design, Setting, and Patients Using clinical registry data from the Michigan Bariatric Surgery Collaborative (MBSC), we studied all patients undergoing bariatric surgery from 2008 to 2010. For gastric bypass surgery, we used empirical Bayes techniques to create a composite measure by combining several measures, including serious complications, reoperations, and readmissions; hospital and surgeon volume; and outcomes with other, related procedures. Hospitals were ranked based on 2008-09 and placed in one of 3 groups: 3-star (top third), 2-star (middle third), and 1-star (bottom third). We assessed how well these ratings predicted outcomes in the next year (2010), compared to other widely used measures. Main Outcome Measures Risk-adjusted serious complications. Results Composite measures explained a larger proportion of hospital-level variation in serious complication rates with gastric bypass than other measures. For example, the composite measure explained 89% of the variation compared to only 28% for risk-adjusted complication rates alone. Composite measures also appeared better at predicting future performance compared to individual measures. When ranked on the composite measure, 1-star hospitals (bottom 20%), had 2-fold higher serious complication rates (4.6% vs. 2.4%; OR 2.0; 95% CI, 1.1 to 3.5) compared to 3-star (top 20%) hospitals. Differences in serious complications rates between 1-star and 3-star hospitals were much smaller when hospitals were ranked using serious complications (4.0% vs. 2.7%; OR 1.6; 95% CI, 0.8-2.9) and hospital volume (3.3% vs. 3.2%; OR 0.85; 95% CI, 0.4 to 1.7) Conclusions Composite measures are much better at explaining hospital-level variation in serious complications and predicting future performance than other approaches. In this preliminary study, it appears that such composite measures may be better than existing alternatives for profiling hospital performance with bariatric surgery. PMID:24132708

New developments in instrumentation at the W. M. Keck Observatory

NASA Astrophysics Data System (ADS)

Adkins, Sean M.; Armandroff, Taft E.; Fitzgerald, Michael P.; Johnson, James; Larkin, James E.; Lewis, Hilton A.; Martin, Christopher; Matthews, Keith Y.; Prochaska, J. X.; Wizinowich, Peter

2014-07-01

The W. M. Keck Observatory continues to develop new capabilities in support of our science driven strategic plan which emphasizes leadership in key areas of observational astronomy. This leadership is a key component of the scientific productivity of our observing community and depends on our ability to develop new instrumentation, upgrades to existing instrumentation, and upgrades to supporting infrastructure at the observatory. In this paper we describe the as measured performance of projects completed in 2014 and the expected performance of projects currently in the development or construction phases. Projects reaching completion in 2014 include a near-IR tip/tilt sensor for the Keck I adaptive optics system, a new center launch system for the Keck II laser guide star facility, and NIRES, a near-IR Echelle spectrograph for the Keck II telescope. Projects in development include a new seeing limited integral field spectrograph for the visible wavelength range called the Keck Cosmic Web Imager, a deployable tertiary mirror for the Keck I telescope, upgrades to the spectrograph detector and the imager of the OSIRIS instrument, and an upgrade to the telescope control systems on both Keck telescopes.

Performance assessment of MEMS adaptive optics in tactical airborne systems

NASA Astrophysics Data System (ADS)

Tyson, Robert K.

1999-09-01

Tactical airborne electro-optical systems are severely constrained by weight, volume, power, and cost. Micro- electrical-mechanical adaptive optics provide a solution that addresses the engineering realities without compromising spatial and temporal compensation requirements. Through modeling and analysis, we determined that substantial benefits could be gained for laser designators, ladar, countermeasures, and missile seekers. The developments potential exists for improving seeker imagery resolution 20 percent, extending countermeasures keep-out range by a factor of 5, doubling the range for ladar detection and identification, and compensating for supersonic and hypersonic aircraft boundary layers. Innovative concepts are required for atmospheric pat hand boundary layer compensation. We have developed design that perform these tasks using high speed scene-based wavefront sensing, IR aerosol laser guide stars, and extended-object wavefront beacons. We have developed a number of adaptive optics system configurations that met the spatial resolution requirements and we have determined that sensing and signal processing requirements can be met. With the help of micromachined deformable mirrors and sensor, we will be able to integrate the systems into existing airborne pods and missiles as well as next generation electro-optical systems.

Gravitational lensing of a star by a rotating black hole

NASA Astrophysics Data System (ADS)

Dokuchaev, V. I.; Nazarova, N. O.

2017-11-01

The gravitational lensing of a finite star moving around a rotating Kerr black hole has been numerically simulated. Calculations for the direct image of the star and for the first and second light echoes have been performed for the star moving with an orbital period of 3.22 h around the supermassive black hole SgrA* at the center of the Galaxy. The time dependences for the observed position of the star on the celestial sphere, radiation flux from the star, frequency of detected radiation, and major and minor semiaxes of the lensed image of the star have been calculated and plotted. The detailed observation of such lensing requires a space interferometer such as the Russian Millimetron project.

Development of the implant surgical technique and assessment rating system

PubMed Central

Park, Jung-Chul; Hwang, Ji-Wan; Lee, Jung-Seok; Jung, Ui-Won; Choi, Seong-Ho; Cho, Kyoo-Sung; Chai, Jung-Kiu

2012-01-01

Purpose There has been no attempt to establish an objective implant surgical evaluation protocol to assess residents' surgical competence and improve their surgical outcomes. The present study presents a newly developed assessment and rating system and simulation model that can assist the teaching staffs to evaluate the surgical events and surgical skills of residents objectively. Methods Articles published in peer-reviewed English journals were selected using several scientific databases and subsequently reviewed regarding surgical competence and assessment tools. Particularly, medical journals reporting rating and evaluation protocols for various types of medical surgeries were thoroughly analyzed. Based on these studies, an implant surgical technique assessment and rating system (iSTAR) has been developed. Also, a specialized dental typodont was developed for the valid and reliable assessment of surgery. Results The iSTAR consists of two parts including surgical information and task-specific checklists. Specialized simulation model was subsequently produced and can be used in combination with iSTAR. Conclusions The assessment and rating system provided may serve as a reference guide for teaching staffs to evaluate the residents' implant surgical techniques. PMID:22413071

Stars Above, Earth Below: Astronomy in the National Parks

NASA Astrophysics Data System (ADS)

Nordgren, Tyler E.

2011-01-01

The U.S. national parks that protect our enjoyment of the landscape around us by day, also protect our enjoyment of the sky above at night. With the growth of light pollution, the view of the stars and Milky Way overhead has become as rare as the views of glaciers, geysers, and grizzlies that bring millions of visitors to the parks every year. Through the pristine view of a starry sky at night park visitors are primed to learn about our planet, its place in the solar system, and the larger Universe in which we live. The national parks are therefore the largest informal educational setting for reaching millions of people from all over the world who might not otherwise encounter astronomical outreach. The material in this presentation has been field tested in national parks, campgrounds, lodges, and visitor centers over the last four years and is elaborated on in the just released book: "Stars Above, Earth Below: A Guide to Astronomy in the National Parks.” Funding for this project was provided by The Planetary Society.

Sun, the Earth, and Near-Earth Space: A Guide to the Sun-Earth System

NASA Technical Reports Server (NTRS)

Eddy, John A.

2010-01-01

In a world of warmth and light and living things we soon forget that we are surrounded by a vast universe that is cold and dark and deadly dangerous, just beyond our door. On a starry night, when we look out into the darkness that lies around us, the view can be misleading in yet another way: for the brightness and sheer number of stars, and their chance groupings into familiar constellations, make them seem much nearer to each other, and to us, that in truth they are. And every one of them--each twinkling, like a diamond in the sky--is a white-hot sun, much like our own. The nearest stars in our own galaxy--the Milky Way-- are more than a million times further away from us than our star, the Sun. We could make a telephone call to the Moon and expect to wait but a few seconds between pieces of a conversation, or but a few hours in calling any planet in our solar system.

The Chajnantor Sub/Millimeter Survey Telescope

NASA Astrophysics Data System (ADS)

Golwala, Sunil

2018-01-01

We are developing the Chajnantor Sub/millimeter Survey Telescope, a project to build a 30-m telescope operating at wavelengths as short as 850 µm with 1 degree field of view for imaging and multi-object spectroscopic surveys. This project will provide massive new data sets for studying star formation at high redshift and in the local universe, feedback mechanisms in galaxy evolution, the structure of galaxy clusters, and the cosmological peculiar velocity field. We will highlight CSST's capabilities for studying galaxy evolution, where it will: trace the evolution of dusty, star-forming galaxies from high redshift to the z ≍ 1-3 epoch when they dominate the cosmic star formation rate; connect this population to the high-redshift rest-frame UV/optical galaxy population; use these dusty galaxies, the most biased overdensities, to guide ultra-deep followup at z > 3.5 and possibly z > 7; measure the brightness of important submm/FIR spectral lines like [CII]; search for molecular and atomic outflows; and do calorimetry of the CGM via the thermal SZ effect. We will describe the expected surveys addressing these science goals, the novel telescope design, and the planned survey instrumentation.

Culinary culture and globalization: an analysis of British and German Michelin-starred restaurants.

PubMed

Lane, Christel

2011-12-01

The high-end restaurant segment in Britain and Germany has long been shaped by the cultural hegemony of French haute cuisine, perpetuated by multiple processes, including the influence of the Michelin or Red Guide. Traditionally, this hegemony has been expressed in the prevalence of French expatriate chefs, culinary techniques and style and even restaurant culture. This paper investigates whether processes of globalization have weakened or even undermined this French cultural dominance in fine-dining restaurants and their culinary culture. To this end, the study identifies the various forms taken by globalization processes in this industry segment and then assesses their impact on the dominance of the French paradigm of culinary culture. The investigation focuses on British and German Michelin-starred restaurants, underlining both commonalities and divergences in the process of interaction between French, global and local influences. The study employs a qualitative method, using a number of case studies to discern cross-industry patterns. All chefs with two or three stars in the two countries, i.e. 45 chefs, were selected for the analysis of their cuisine. © London School of Economics and Political Science 2011.

A learning performance study between the conventional approach and augmented reality textbook among secondary school students

NASA Astrophysics Data System (ADS)

Gopalan, Valarmathie; Zulkifli, Abdul Nasir; Bakar, Juliana Aida Abu

2016-08-01

Malaysia is moving towards becoming a developed nation by 2020. As such, the need for adequate human resources in science-related fields is one of the requirements to achieve a developed nation status. Unfortunately, there is a downward trend in the number of students pursuing the science stream at the secondary school level. This paper introduces an enhanced science textbook using Augmented Reality (eSTAR) that is intended to motivate students to be interested in science. The eSTAR was implemented to provide a supplement to the conventional science teaching and learning methods in the secondary schools. A learning performance study with a control group was conducted to investigate the effectiveness of the eSTAR for science learning among a sample of 140 Form Two secondary school students. The results indicate that the learning performance of the students in both groups had a significant difference in mean scores between the pre-test and post-test. Students using the eSTAR have a better score in the post-test and eventually resulted in a better learning performance compared to those who were exposed to the conventional science learning. Overall, the results show that the students benefited from the use of the conventional and eSTAR learning approaches.

Predicting the required number of training samples. [for remotely sensed image data based on covariance matrix estimate quality criterion of normal distribution

NASA Technical Reports Server (NTRS)

Kalayeh, H. M.; Landgrebe, D. A.

1983-01-01

A criterion which measures the quality of the estimate of the covariance matrix of a multivariate normal distribution is developed. Based on this criterion, the necessary number of training samples is predicted. Experimental results which are used as a guide for determining the number of training samples are included. Previously announced in STAR as N82-28109

Teaching High School Physical Education According to National Standards: The 6 Verbs of Success--Demonstrate, Understand, Participate, Achieve, Exhibit and Value

ERIC Educational Resources Information Center

Bert, Greg

2010-01-01

The six national content standards from NASPE define what a student should know and be able to do as a result of a high quality physical education program. The "NASPE SIX" serve as a North Star to guide teachers as they prepare and implement programs. Simply stated, the NASPE Standards for Physical Education are all about six simple…

Ancient Earth, Alien Earths Event

NASA Image and Video Library

2014-08-20

Panelists discuss how research on early Earth could help guide our search for habitable planets orbiting other stars at the “Ancient Earth, Alien Earths” Event at NASA Headquarters in Washington, DC Wednesday, August 20, 2014. The event was sponsored by NASA, the National Science Foundation (NSF), and the Smithsonian Institution and was moderated by Dr. David H. Grinspoon, Senior Scientist at the Planetary Science Institute. Photo Credit: (NASA/Aubrey Gemignani)

Instrument control software development process for the multi-star AO system ARGOS

NASA Astrophysics Data System (ADS)

Kulas, M.; Barl, L.; Borelli, J. L.; Gässler, W.; Rabien, S.

2012-09-01

The ARGOS project (Advanced Rayleigh guided Ground layer adaptive Optics System) will upgrade the Large Binocular Telescope (LBT) with an AO System consisting of six Rayleigh laser guide stars. This adaptive optics system integrates several control loops and many different components like lasers, calibration swing arms and slope computers that are dispersed throughout the telescope. The purpose of the instrument control software (ICS) is running this AO system and providing convenient client interfaces to the instruments and the control loops. The challenges for the ARGOS ICS are the development of a distributed and safety-critical software system with no defects in a short time, the creation of huge and complex software programs with a maintainable code base, the delivery of software components with the desired functionality and the support of geographically distributed project partners. To tackle these difficult tasks, the ARGOS software engineers reuse existing software like the novel middleware from LINC-NIRVANA, an instrument for the LBT, provide many tests at different functional levels like unit tests and regression tests, agree about code and architecture style and deliver software incrementally while closely collaborating with the project partners. Many ARGOS ICS components are already successfully in use in the laboratories for testing ARGOS control loops.

KAPAO: a MEMS-based natural guide star adaptive optics system

NASA Astrophysics Data System (ADS)

Severson, Scott A.; Choi, Philip I.; Contreras, Daniel S.; Gilbreth, Blaine N.; Littleton, Erik; McGonigle, Lorcan P.; Morrison, William A.; Rudy, Alex R.; Wong, Jonathan R.; Xue, Andrew; Spjut, Erik; Baranec, Christoph; Riddle, Reed

2013-03-01

We describe KAPAO, our project to develop and deploy a low-cost, remote-access, natural guide star adaptive optics (AO) system for the Pomona College Table Mountain Observatory (TMO) 1-meter telescope. We use a commercially available 140-actuator BMC MEMS deformable mirror and a version of the Robo-AO control software developed by Caltech and IUCAA. We have structured our development around the rapid building and testing of a prototype system, KAPAO-Alpha, while simultaneously designing our more capable final system, KAPAO-Prime. The main differences between these systems are the prototype's reliance on off-the-shelf optics and a single visible-light science camera versus the final design's improved throughput and capabilities due to the use of custom optics and dual-band, visible and near-infrared imaging. In this paper, we present the instrument design and on-sky closed-loop testing of KAPAO-Alpha as well as our plans for KAPAO-Prime. The primarily undergraduate-education nature of our partner institutions, both public (Sonoma State University) and private (Pomona and Harvey Mudd Colleges), has enabled us to engage physics, astronomy, and engineering undergraduates in all phases of this project. This material is based upon work supported by the National Science Foundation under Grant No. 0960343.

Recent developments in aircraft protection systems for laser guide star operations

NASA Astrophysics Data System (ADS)

Stomski, Paul J.; Murphy, Thomas W.; Campbell, Randy

2012-07-01

The astronomical community's use of high power laser guide star adaptive optics (LGS-AO) systems presents a potential hazard to aviation. Historically, the most common and trusted means of protecting aircraft and their occupants has been the use of safety observers (aka spotters) armed with shut-off switches. These safety observers watch for aircraft at risk and terminate laser propagation before the aircraft can be adversely affected by the laser. Efforts to develop safer and more cost-effective automated aircraft protection systems for use by the astronomical community have been inhibited by both technological and regulatory challenges. This paper discusses recent developments in these two areas. Specifically, with regard to regulation and guidance we discuss the 2011 release of AS-6029 by the SAE as well as the potential impact of RTCA DO-278A. With regard to the recent developments in the technology used to protect aircraft from laser illumination, we discuss the novel Transponder Based Aircraft Detection (TBAD) system being installed at W. M. Keck Observatory (WMKO). Finally, we discuss our strategy for evaluating TBAD compliance with the regulations and for seeking appropriate approvals for LGS operations at WMKO using a fully automated, flexibly configured, multi-tier aircraft protection system incorporating this new technology.

The use of think-aloud protocols to identify a decision-making process of community pharmacists aimed at improving CMS Star Ratings scores.

PubMed

George, David L; Smith, Michael J; Draugalis, JoLaine R; Tolma, Eleni L; Keast, Shellie L; Wilson, Justin B

2018-03-01

The Center for Medicare and Medicaid Services (CMS) created the Star Rating system based on multiple measures that indicate the overall quality of health plans. Community pharmacists can impact certain Star Ratings measure scores through medication adherence and patient safety interventions. To explore methods, needs, and workflow issues of community pharmacists to improve CMS Star Ratings measures. Think-aloud protocols (TAPs) were conducted with active community retail pharmacists in Oklahoma. Each TAP was audio recorded and transcribed to documents for analysis. Analysts agreed on common themes, illuminated differences in findings, and saturation of the data gathered. Methods, needs, and workflow themes of community pharmacists associated with improving Star Ratings measures were compiled and organized to exhibit a decision-making process. Five TAPs were performed among three independent pharmacy owners, one multi-store owner, and one chain-store administrator. A thematically common 4-step process to monitor and improve CMS Star Ratings scores among participants was identified. To improve Star Ratings measures, pharmacists: 1) used technology to access scores, 2) analyzed data to strategically set goals, 3) assessed individual patient information for comprehensive assessment, and 4) decided on interventions to best impact Star Ratings scores. Participants also shared common needs, workflow issues, and benefits associated with methods used in improving Star Ratings. TAPs were useful in exploring processes of pharmacists who improve CMS Star Ratings scores. Pharmacists demonstrated and verbalized their methods, workflow issues, needs, and benefits related to performing the task. The themes and decision-making process identified to improving CMS Star Ratings scores will assist in the development of training and education programs for pharmacists in the community setting. Published by Elsevier Inc.

Non-radial pulsations in Be stars. Preparation of the COROT space mission.

NASA Astrophysics Data System (ADS)

Gutierrez-Soto, J.

2006-12-01

The space mission COROT scheduled to be launched in December 2006, will provide ultra high precision, relative stellar photometry for very long continuous observing runs. Up to ten stars will be observed in the seismology fields with a photometric accuracy of 1 ppm, and several thousands in the exoplanet fields with an accuracy of a few 10-4 and colour information. The observations of Be stars with COROT will provide photometric time series with unprecedented quality. Their analysis will allow us to qualitatively improve our knowledge and understanding of the pulsational characteristics of Be stars. In consequence, we have started a research project aimed at observing Be stars both in the seismology and exoplanet fields of COROT. In this thesis we present the first step of this project, which is the preparation and study of the sample of Be stars that will be observed by COROT. We have performed photometric analysis of all Be stars located in the seismology fields. Special emphasis has been given to two Be stars (NW Ser and V1446 Aql) in which we have detected multiperiodic variability and which we have modelled in terms of stellar pulsations. We have also performed an in-depth spectroscopic study of NW Ser and modelled the non-radial pulsations taking into account the rotational effects. A technique to search for faint Be stars based on CCD photometry has also been developed. We present here a list of faint Be stars located in the exoplanet fields of COROT detected with this technique and which we propose as targets for COROT. In addition, we have proven that our period-analysis techniques are suitable to detect multiperiodicity in large temporal baseline data. In particular, we have detected non-radial pulsations in some Be stars in the low-metallicity galaxy SMC.

A low-cost, CCD solid state star tracker

NASA Technical Reports Server (NTRS)

Chmielowski, M.; Wynne, D.

1992-01-01

Applied Research Corporation (ARC) has developed an engineering model of a multi-star CCD-based tracker for space applications requiring radiation hardness, high reliability and low power consumption. The engineering unit compared favorably in functional performance tests to the standard NASA single-star tracker. Characteristics of the ARC star tracker are: field of view = 10 deg x 7.5 deg, sensitivity range of -1 to +5 star magnitude, NEA = 3 in x 3 in, linearity = 5 in x 5 in, and power consumption of 1-3 W (operating mode dependent). The software is upgradable through a remote link. The hardware-limited acquisition rate is 1-5 Hz for stars of +2 to +5 magnitude and 10-30 Hz for -1 to +2 magnitude stars. Mechanical and electrical interfaces are identical to the standard NASA star tracker.

A star-and-sky chopping polarimeter - Design and performance

NASA Astrophysics Data System (ADS)

Jain, S. K.; Srinivasulu, G.

1991-09-01

A star-and-sky chopping polarimeter is developed for accurate measurements of linear polarization of starlight in the standard astronomical photometric U, B, V, R, and I bands. The instrumental polarization, as determined by observing the standard unpolarized stars, is 0.04 percent. It is possible to use the instrument for the measurements of circular polarization as well. A Unicorn microcomputer controls the various operations of the instrument, acquires the data, and does the on-line data reduction. This paper describes the design and performance of the polarimeter.

Study of the true performance limits of the Astrometric Multiplexing Area Scanner (AMAS)

NASA Technical Reports Server (NTRS)

Frederick, L. W.; Mcalister, H. A.

1975-01-01

The Astrometric Multiplexing Area Scanner (AMAS) is an instrument designed to perform photoelectric long focus astrometry of small fields. Modulation of a telescope focal plane with a rotating Ronchi ruling produces a frequency modulated signal from which relative positions and magnitudes can be extracted. Evaluation instrumental precision, accuracy and resolution characteristics with respect to a variety of instrumental and cosmical parameters indicates 1.5 micron precision and accuracy for single stars under specific conditions. This value decreases for increased number of field stars, particularly for fainter stars.

Neutron Star Interior Composition Explorer (NICE)

NASA Technical Reports Server (NTRS)

Gendreau, Keith C.; Arzoumanian, Zaven

2008-01-01

This viewgraph presentation contains an overview of the mission of the Neutron Star Interior Composition Explorer (NICE), a proposed International Space Station (ISS) payload dedicated ot the study of neutron stars. There are also reviews of the Science Objectives of the payload,the science measurements, the design and the expected performance for the instruments for NICE,

CHEMICAL ABUNDANCES OF MEMBER STARS IN THE OPEN CLUSTER NGC 2632 (PRAESEPE)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, X. L.; Chen, Y. Q.; Zhao, G.

2015-11-15

Based on high-resolution, high signal-to-noise ratio spectra, we present abundances of 17 elements (Fe, O, Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Co, Ni, Y, Zr, Ba, La) for six stars (one Am star, one F dwarf star, and four GK giant stars) and radial velocities for 18 proper-motion selected member stars in the open cluster NGC 2632. In the Am star, s-process elements Y and Ba are clearly overabundant, which may be considered as an indicator of a peculiar Am star. The average [Fe/H] is 0.16 ± 0.06 from four GK giant member stars, which is similarmore » to that of solar-type stars in the literature. As compared with dwarf stars, significant overabundances are found for Na, Mg, and Ba elements in our giant stars, which can be explained by the evolutionary effect. We also detect a star-to-star scatter of [Na/Fe] ratios among four giants which locate approximately at the same position in the CMD. Finally, we perform an analysis on the possible connection between the abundance and spatial structure of NGC 2632, but we find no inhomogeneous abundance among different clumps of stars in this cluster based on our limited sample.« less

Design/cost tradeoff studies. Appendix A. Supporting analyses and tradeoffs, book 2. Earth Observatory Satellite system definition study (EOS)

NASA Technical Reports Server (NTRS)

1974-01-01

Attitude reference systems for use with the Earth Observatory Satellite (EOS) are described. The systems considered are fixed and gimbaled star trackers, star mappers, and digital sun sensors. Covariance analyses were performed to determine performance for the most promising candidate in low altitude and synchronous orbits. The performance of attitude estimators that employ gyroscopes which are periodically updated by a star sensor is established by a single axis covariance analysis. The other systems considered are: (1) the propulsion system design, (2) electric power and electrical integration, (3) thermal control, (4) ground data processing, and (5) the test plan and cost reduction aspects of observatory integration and test.

STARS: a software application for the EBEX autonomous daytime star cameras

NASA Astrophysics Data System (ADS)

Chapman, Daniel; Didier, Joy; Hanany, Shaul; Hillbrand, Seth; Limon, Michele; Miller, Amber; Reichborn-Kjennerud, Britt; Tucker, Greg; Vinokurov, Yury

2014-07-01

The E and B Experiment (EBEX) is a balloon-borne telescope designed to probe polarization signals in the CMB resulting from primordial gravitational waves, gravitational lensing, and Galactic dust emission. EBEX completed an 11 day flight over Antarctica in January 2013 and data analysis is underway. EBEX employs two star cameras to achieve its real-time and post-flight pointing requirements. We wrote a software application called STARS to operate, command, and collect data from each of the star cameras, and to interface them with the main flight computer. We paid special attention to make the software robust against potential in-flight failures. We report on the implementation, testing, and successful in flight performance of STARS.

Mass ejection by strange star mergers and observational implications.

PubMed

Bauswein, A; Janka, H-T; Oechslin, R; Pagliara, G; Sagert, I; Schaffner-Bielich, J; Hohle, M M; Neuhäuser, R

2009-07-03

We determine the Galactic production rate of strangelets as a canonical input to calculations of the measurable cosmic ray flux of strangelets by performing simulations of strange star mergers and combining the results with recent estimates of stellar binary populations. We find that the flux depends sensitively on the bag constant of the MIT bag model of QCD and disappears for high values of the bag constant and thus more compact strange stars. In the latter case, strange stars could coexist with ordinary neutron stars as they are not converted by the capture of cosmic ray strangelets. An unambiguous detection of an ordinary neutron star would then not rule out the strange matter hypothesis.

Mi-STAR: Designing Integrated Science Curriculum to Address the Next Generation Science Standards and Their Foundations

NASA Astrophysics Data System (ADS)

Gochis, E. E.; Huntoon, J. E.

2015-12-01

Mi-STAR (Michigan Science Teaching and Assessment Reform, http://mi-star.mtu.edu/) was funded by the Herbert H. and Grace A. Dow Foundation to reform K-12 science education to present science as an integrated body of knowledge that is applied to address societal issues. To achieve this goal, Mi-STAR is developing an integrated science curriculum for the middle grades that will be aligned with the Next Generation Science Standards (NGSS). Similar to the geosciences, the curriculum requires the integration of science, engineering and math content to explore 21st-century issues and demonstrates how these concepts can be used in service of society. The curriculum is based on the Mi-STAR Unit Specification Chart which pairs interdisciplinary themes with bundled NGSS Performance Expectations. Each unit is developed by a collaborative team of K-12 teachers, university STEM content experts and science education experts. Prior to developing a unit, each member on the team attends the on-line Mi-STAR Academy, completing 18+ hours of professional development (PD). This on-line PD program familiarizes teachers and experts with necessary pedagogical and content background knowledge, including NGSS and three-dimensional learning. With this background, teams use a staged, backwards design process to craft a multi-week unit based on a series of performance based tasks, or 'challenges' that engage students in actively doing science and engineering. Each unit includes Disciplinary Core Ideas from multiple disciplines, which focus on local and familiar examples that demonstrate the relevance of science in student's lives. Performance-based assessments are interwoven throughout the unit. Mi-STAR units will go through extensive pilot testing in several school districts across the state of Michigan. Additionally, the Mi-STAR program will develop teacher professional development programs to support implementation of the curriculum and design a pre-service teacher program in integrated science. We will share preliminary results on the collaborative Mi-STAR process of designing integrated science curriculum to address NGSS.

Precision Pointing Control System (PPCS) star tracker test

NASA Technical Reports Server (NTRS)

1972-01-01

Tests performed on the TRW precision star tracker are described. The unit tested was a two-axis gimballed star tracker designed to provide star LOS data to an accuracy of 1 to 2 sec. The tracker features a unique bearing system and utilizes thermal and mechanical symmetry techniques to achieve high precision which can be demonstrated in a one g environment. The test program included a laboratory evaluation of tracker functional operation, sensitivity, repeatibility, and thermal stability.

The Chemical Composition of the Active Stars

NASA Astrophysics Data System (ADS)

Glazunova, L. V.

The comparison of the results of the studies of the active stars' chemical composition obtained by different authors has been performed. It was concluded that the difference between the abundances of some elements in active and inactive stars becomes significant (> 3σ) only for the active stars with high chromospheric activity (lgR'HK > -4). This is the case primarily for the light elements, namely Li, Na and Al, as well as heavy elements with Z > 30.

Passive load follow analysis of the STAR-LM and STAR-H2 systems

NASA Astrophysics Data System (ADS)

Moisseytsev, Anton

A steady-state model for the calculation of temperature and pressure distributions, and heat and work balance for the STAR-LM and the STAR-H2 systems was developed. The STAR-LM system is designed for electricity production and consists of the lead cooled reactor on natural circulation and the supercritical carbon dioxide Brayton cycle. The STAR-H2 system uses the same reactor which is coupled to the hydrogen production plant, the Brayton cycle, and the water desalination plant. The Brayton cycle produces electricity for the on-site needs. Realistic modules for each system component were developed. The model also performs design calculations for the turbine and compressors for the CO2 Brayton cycle. The model was used to optimize the performance of the entire system as well as every system component. The size of each component was calculated. For the 400 MWt reactor power the STAR-LM produces 174.4 MWe (44% efficiency) and the STAR-H2 system produces 7450 kg H2/hr. The steady state model was used to conduct quasi-static passive load follow analysis. The control strategy was developed for each system; no control action on the reactor is required. As a main safety criterion, the peak cladding temperature is used. It was demonstrated that this temperature remains below the safety limit during both normal operation and load follow.

Singapore Tele-technology Aided Rehabilitation in Stroke (STARS) trial: protocol of a randomized clinical trial on tele-rehabilitation for stroke patients.

PubMed

Koh, Gerald Choon-Huat; Yen, Shih Cheng; Tay, Arthur; Cheong, Angela; Ng, Yee Sien; De Silva, Deidre Anne; Png, Carolina; Caves, Kevin; Koh, Karen; Kumar, Yogaprakash; Phan, Shi Wen; Tai, Bee Choo; Chen, Cynthia; Chew, Effie; Chao, Zhaojin; Chua, Chun En; Koh, Yen Sin; Hoenig, Helen

2015-09-05

Most acute stroke patients with disabilities do not receive recommended rehabilitation following discharge to the community. Functional and social barriers are common reasons for non-adherence to post-discharge rehabilitation. Home rehabilitation is an alternative to centre-based rehabilitation but is costlier. Tele-rehabilitation is a possible solution, allowing for remote supervision of rehabilitation and eliminating access barriers. The objective of the Singapore Tele-technology Aided Rehabilitation in Stroke (STARS) trial is to determine if a novel tele-rehabilitation intervention for the first three months after stroke admission improves functional recovery compared to usual care. This is a single blind (evaluator blinded), parallel, two-arm randomised controlled trial study design involving 100 recent stroke patients. The inclusion criteria are age ≥40 years, having caregiver support and recent stroke defined as stroke diagnosis within 4 weeks. Consenting participants will be randomized with varying block size of 4 or 6 assuming a 1:1 treatment allocation with the participating centre as the stratification factor. The baseline assessment will be done within 4 weeks of stroke onset, followed by follow-up assessments at 3 and 6 months. The tele-rehabilitation intervention lasts for 3 months and includes exercise 5-days-a-week using an iPad-based system that allows recording of daily exercise with video and sensor data and weekly video-conferencing with tele-therapists after data review. Those allocated to the control group will receive usual care. The primary outcome measure is improvement in life task's social activity participation at three months as measured by the disability component of the Jette Late Life Functional and Disability Instrument (LLFDI). Secondary outcome variables consist of gait speed (Timed 5-Meter Walk Test) and endurance (Two-Minute Walk test), performance of basic activities of daily living (Shah-modified Barthel Index), balance confidence (Activities-Specific Balance Confidence Scale), patient self-reported health-related quality-of-life [Euro-QOL (EQ-5D)], health service utilization (Singapore Stroke Study Health Service Utilization Form) and caregiver reported stress (Zarit Caregiver Burden Inventory). The goal of this trial is to provide evidence on the potential benefit and cost-effectiveness of this novel tele-rehabilitation programme which will guide health care decision-making and potentially improve performance of post-stroke community-based rehabilitation. This trial protocol was registered under ClinicalTrials.gov on 18 July 2013 as study title "The Singapore Tele-technology Aided Rehabilitation in Stroke (STARS) Study" (ID: The STARS Study, ClinicalTrials.gov Identifier: NCT01905917 ).

Design Considerations For Imaging Charge-Coupled Device (ICCD) Star Sensors

NASA Astrophysics Data System (ADS)

McAloon, K. J.

1981-04-01

A development program is currently underway to produce a precision star sensor using imaging charge coupled device (ICCD) technology. The effort is the critical component development phase for the Air Force Multi-Mission Attitude Determination and Autonomous Navigation System (MADAN). A number of unique considerations have evolved in designing an arcsecond accuracy sensor around an ICCD detector. Three tiers of performance criteria are involved: at the spacecraft attitude determination system level, at the star sensor level, and at the detector level. Optimum attitude determination system performance involves a tradeoff between Kalman filter iteration time and sensor ICCD integration time. The ICCD star sensor lends itself to the use of a new approach in the functional interface between the attitude determination system and the sensor. At the sensor level image data processing tradeoffs are important for optimum sensor performance. These tradeoffs involve the sensor optic configuration, the optical point spread function (PSF) size and shape, the PSF position locator, and the microprocessor locator algorithm. Performance modelling of the sensor mandates the use of computer simulation programs. Five key performance parameters at the ICCD detector level are defined. ICCD error characteristics have also been isolated to five key parameters.

A robust star identification algorithm with star shortlisting

NASA Astrophysics Data System (ADS)

Mehta, Deval Samirbhai; Chen, Shoushun; Low, Kay Soon

2018-05-01

A star tracker provides the most accurate attitude solution in terms of arc seconds compared to the other existing attitude sensors. When no prior attitude information is available, it operates in "Lost-In-Space (LIS)" mode. Star pattern recognition, also known as star identification algorithm, forms the most crucial part of a star tracker in the LIS mode. Recognition reliability and speed are the two most important parameters of a star pattern recognition technique. In this paper, a novel star identification algorithm with star ID shortlisting is proposed. Firstly, the star IDs are shortlisted based on worst-case patch mismatch, and later stars are identified in the image by an initial match confirmed with a running sequential angular match technique. The proposed idea is tested on 16,200 simulated star images having magnitude uncertainty, noise stars, positional deviation, and varying size of the field of view. The proposed idea is also benchmarked with the state-of-the-art star pattern recognition techniques. Finally, the real-time performance of the proposed technique is tested on the 3104 real star images captured by a star tracker SST-20S currently mounted on a satellite. The proposed technique can achieve an identification accuracy of 98% and takes only 8.2 ms for identification on real images. Simulation and real-time results depict that the proposed technique is highly robust and achieves a high speed of identification suitable for actual space applications.

Implications from GW170817 and I-Love-Q relations for relativistic hybrid stars

NASA Astrophysics Data System (ADS)

Paschalidis, Vasileios; Yagi, Kent; Alvarez-Castillo, David; Blaschke, David B.; Sedrakian, Armen

2018-04-01

Gravitational wave observations of GW170817 placed bounds on the tidal deformabilities of compact stars, allowing one to probe equations of state for matter at supranuclear densities. Here we design new parametrizations for hybrid hadron-quark equations of state, which give rise to low-mass twin stars, and test them against GW170817. We find that GW170817 is consistent with the coalescence of a binary hybrid star-neutron star. We also test and find that the I-Love-Q relations for hybrid stars in the third family agree with those for purely hadronic and quark stars within ˜3 % for both slowly and rapidly rotating configurations, implying that these relations can be used to perform equation-of-state independent tests of general relativity and to break degeneracies in gravitational waveforms for hybrid stars in the third family as well.

Boeing's STAR-FODB test results

NASA Astrophysics Data System (ADS)

Fritz, Martin E.; de la Chapelle, Michael; Van Ausdal, Arthur W.

1995-05-01

Boeing has successfully concluded a 2 1/2 year, two phase developmental contract for the STAR-Fiber Optic Data Bus (FODB) that is intended for future space-based applications. The first phase included system analysis, trade studies, behavior modeling, and architecture and protocal selection. During this phase we selected AS4074 Linear Token Passing Bus (LTPB) protocol operating at 200 Mbps, along with the passive, star-coupled fiber media. The second phase involved design, build, integration, and performance and environmental test of brassboard hardware. The resulting brassboard hardware successfully passed performance testing, providing 200 Mbps operation with a 32 X 32 star-coupled medium. This hardware is suitable for a spaceflight experiment to validate ground testing and analysis and to demonstrate performace in the intended environment. The fiber bus interface unit (FBIU) is a multichip module containing transceiver, protocol, and data formatting chips, buffer memory, and a station management controller. The FBIU has been designed for low power, high reliability, and radiation tolerance. Nine FBIUs were built and integrated with the fiber optic physical layer consisting of the fiber cable plant (FCP) and star coupler assembly (SCA). Performance and environmental testing, including radiation exposure, was performed on selected FBIUs and the physical layer. The integrated system was demonstrated with a full motion color video image transfer across the bus while simultaneously performing utility functions with a fiber bus control module (FBCM) over a telemetry and control (T&C) bus, in this case AS1773.

Geo-STAR: A Geostationary Microwave Sounder for the Future

NASA Technical Reports Server (NTRS)

Lambrigtsen, Bjorn H.; Brown, S. T.; Dinardo, S. J.; Gaier, T. C.; Kangaslahti, P. P.; Tanner, A. B.

2007-01-01

The Geostationary Synthetic Thinned Aperture Radiometer (GeoSTAR) is a new Earth remote sensing instrument concept that has been under development at the Jet Propulsion Laboratory. First conceived in 1998 as a NASA New Millennium Program mission and subsequently developed in 2003-2006 as a proof-of-concept prototype under the NASA Instrument Incubator Program, it is intended to fill a serious gap in our Earth remote sensing capabilities - namely the lack of a microwave atmospheric sounder in geostationary orbit. The importance of such observations have been recognized by the National Academy of Sciences National Research Council, which recently released its report on a 'Decadal Survey' of NASA Earth Science activities1. One of the recommended missions for the next decade is a geostationary microwave sounder. GeoSTAR is well positioned to meet the requirements of such a mission, and because of the substantial investment NASA has already made in GeoSTAR technology development, this concept is fast approaching the necessary maturity for implementation in the next decade. NOAA is also keenly interested in GeoSTAR as a potential payload on its next series of geostationary weather satellites, the GOES-R series. GeoSTAR, with its ability to map out the three-dimensional structure of temperature, water vapor, clouds, precipitation and convective parameters on a continual basis, will significantly enhance our ability to observe hurricanes and other severe storms. In addition, with performance matching that of current and next generation of low-earth-orbiting microwave sounders, GeoSTAR will also provide observations important to the study of the hydrologic cycle, atmospheric processes and climate variability and trends. In particular, with GeoSTAR it will be possible to fully resolve the diurnal cycle. We discuss the GeoSTAR concept and basic design, the performance of the prototype, and a number of science applications that will be possible with GeoSTAR. The work reported on here was performed at the Jet Propulsion Laboratory, California Institute of Technology under a contract with the National Aeronautics and Space Administration.

Exposure Time Optimization for Highly Dynamic Star Trackers

PubMed Central

Wei, Xinguo; Tan, Wei; Li, Jian; Zhang, Guangjun

2014-01-01

Under highly dynamic conditions, the star-spots on the image sensor of a star tracker move across many pixels during the exposure time, which will reduce star detection sensitivity and increase star location errors. However, this kind of effect can be compensated well by setting an appropriate exposure time. This paper focuses on how exposure time affects the star tracker under highly dynamic conditions and how to determine the most appropriate exposure time for this case. Firstly, the effect of exposure time on star detection sensitivity is analyzed by establishing the dynamic star-spot imaging model. Then the star location error is deduced based on the error analysis of the sub-pixel centroiding algorithm. Combining these analyses, the effect of exposure time on attitude accuracy is finally determined. Some simulations are carried out to validate these effects, and the results show that there are different optimal exposure times for different angular velocities of a star tracker with a given configuration. In addition, the results of night sky experiments using a real star tracker agree with the simulation results. The summarized regularities in this paper should prove helpful in the system design and dynamic performance evaluation of the highly dynamic star trackers. PMID:24618776

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sperauskas, J.; Začs, L.; Deveikis, V.

Yamashita has described a group of early carbon stars with enhanced lines of barium that resemble the CH stars but have low radial velocities. It is not clear whether they represent a class of stars separate from early R stars. Radial-velocity measurements and abundance analyses are applied in order to clarify the evolutionary status of CH-like stars. Radial-velocity monitoring was performed over a time interval of about 10 years. Abundance analysis was carried out using high-resolution spectra and the method of atmospheric models for three CH-like candidate stars. The radial-velocity monitoring confirmed regular variations for all of the classified CH-likemore » stars, except for two, in support of their binary nature. The calculated orbital parameters are similar to those observed for barium stars in the disk of the Galaxy and their counterparts in the halo, that is, the CH stars. The relatively low luminosity of CH-like stars and the overabundance of s -process elements in the atmospheres are in agreement with a mass-transfer scenario from the secondary—an AGB star in the past. The kinematic data and metallicities support the idea that CH-like stars are thin/thick-disk population objects.« less

Running STAR-CCM+ Software on the Peregrine System | High-Performance

Science.gov Websites

/bin/lmutil lmstat -c 1999@wind-lms.nrel.gov -a module load star-ccm export TMPDIR="/scratch/$USER + -power -rsh "ssh -oStrictHostKeyChecking=no" -machinefile nodelist -np $(($nodes*$cores , type the commands from the SLURM script and make sure the job runs: module load star-ccm export TMPDIR

Imbalanced Learning for RR Lyrae Stars Based on SDSS and GALEX Databases

NASA Astrophysics Data System (ADS)

Zhang, Jingyi; Zhang, Yanxia; Zhao, Yongheng

2018-03-01

We apply machine learning and Convex-Hull algorithms to separate RR Lyrae stars from other stars like main-sequence stars, white dwarf stars, carbon stars, CVs, and carbon-lines stars, based on the Sloan Digital Sky Survey and Galaxy Evolution Explorer (GALEX). In low-dimensional spaces, the Convex-Hull algorithm is applied to select RR Lyrae stars. Given different input patterns of (u ‑ g, g ‑ r), (g ‑ r, r ‑ i), (r ‑ i, i ‑ z), (u ‑ g, g ‑ r, r ‑ i), (g ‑ r, r ‑ i, i ‑ z), (u ‑ g, g ‑ r, i ‑ z), and (u ‑ g, r ‑ i, i ‑ z), different convex hulls can be built for RR Lyrae stars. Comparing the performance of different input patterns, u ‑ g, g ‑ r, i ‑ z is the best input pattern. For this input pattern, the efficiency (the fraction of true RR Lyrae stars in the predicted RR Lyrae sample) is 4.2% with a completeness (the fraction of recovered RR Lyrae stars in the whole RR Lyrae sample) of 100%, increases to 9.9% with 97% completeness and to 16.1% with 53% completeness by removing some outliers. In high-dimensional spaces, machine learning algorithms are used with input patterns (u ‑ g, g ‑ r, r ‑ i, i ‑ z), (u ‑ g, g ‑ r, r ‑ i, i ‑ z, r), (NUV ‑ u, u ‑ g, g ‑ r, r ‑ i, i ‑ z), and (NUV ‑ u, u ‑ g, g ‑ r, r ‑ i, i ‑ z, r). RR Lyrae stars, which belong to the class of interest in our paper, are rare compared to other stars. For the highly imbalanced data, cost-sensitive Support Vector Machine, cost-sensitive Random Forest, and Fast Boxes is used. The results show that information from GALEX is helpful for identifying RR Lyrae stars, and Fast Boxes is the best performer on the skewed data in our case.

Results of magnetic field measurements performed with the 6-m telescope. IV. Observations in 2010

NASA Astrophysics Data System (ADS)

Romanyuk, I. I.; Semenko, E. A.; Kudryavtsev, D. O.; Moiseeva, A. V.; Yakunin, I. A.

2017-10-01

We present the results of measurements of magnetic fields, radial velocities and rotation velocities for 92 objects, mainly main-sequence chemically peculiar stars. Observations were performed at the 6-m BTA telescope using Main Stellar Spectrograph with a Zeeman analyzer. In 2010, twelve new magnetic stars were discovered: HD 17330, HD 29762, HD 49884, HD 54824, HD 89069, HD 96003, HD 113894, HD 118054, HD 135679, HD 138633, HD 138777, BD +53.1183. The presence of a field is suspected in HD 16705, HD 35379 and HD 35881. Observations of standard stars without a magnetic field confirm the absence of systematic errors which can introduce distortions into the measurements of longitudinal field. The paper gives comments on the results of investigation of each star.

The impact of SLMTA in improving laboratory quality systems in the Caribbean Region.

PubMed

Guevara, Giselle; Gordon, Floris; Irving, Yvette; Whyms, Ismae; Parris, Keith; Beckles, Songee; Maruta, Talkmore; Ndlovu, Nqobile; Albalak, Rachel; Alemnji, George

Past efforts to improve laboratory quality systems and to achieve accreditation for better patient care in the Caribbean Region have been slow. To describe the impact of the Strengthening of Laboratory Management Toward Accreditation (SLMTA) training programme and mentorship amongst five clinical laboratories in the Caribbean after 18 months. Five national reference laboratories from four countries participated in the SLMTA programme that incorporated classroom teaching and implementation of improvement projects. Mentors were assigned to the laboratories to guide trainees on their improvement projects and to assist in the development of Quality Management Systems (QMS). Audits were conducted at baseline, six months, exit (at 12 months) and post-SLMTA (at 18 months) using the Stepwise Laboratory Quality Improvement Process Towards Accreditation (SLIPTA) checklist to measure changes in implementation of the QMS during the period. At the end of each audit, a comprehensive implementation plan was developed in order to address gaps. Baseline audit scores ranged from 19% to 52%, corresponding to 0 stars on the SLIPTA five-star scale. After 18 months, one laboratory reached four stars, two reached three stars and two reached two stars. There was a corresponding decrease in nonconformities and development of over 100 management and technical standard operating procedures in each of the five laboratories. The tremendous improvement in these five Caribbean laboratories shows that SLMTA coupled with mentorship is an effective, user-friendly, flexible and customisable approach to the implementation of laboratory QMS. It is recommended that other laboratories in the region consider using the SLMTA training programme as they engage in quality systems improvement and preparation for accreditation.

Gravitational decoupled anisotropies in compact stars

NASA Astrophysics Data System (ADS)

Gabbanelli, Luciano; Rincón, Ángel; Rubio, Carlos

2018-05-01

Simple generic extensions of isotropic Durgapal-Fuloria stars to the anisotropic domain are presented. These anisotropic solutions are obtained by guided minimal deformations over the isotropic system. When the anisotropic sector interacts in a purely gravitational manner, the conditions to decouple both sectors by means of the minimal geometric deformation approach are satisfied. Hence the anisotropic field equations are isolated resulting a more treatable set. The simplicity of the equations allows one to manipulate the anisotropies that can be implemented in a systematic way to obtain different realistic models for anisotropic configurations. Later on, observational effects of such anisotropies when measuring the surface redshift are discussed. To conclude, the consistency of the application of the method over the obtained anisotropic configurations is shown. In this manner, different anisotropic sectors can be isolated of each other and modeled in a simple and systematic way.

A vectorized code for calculating laminar and turbulent hypersonic flows about blunt axisymmetric bodies at zero and small angles of attack

NASA Technical Reports Server (NTRS)

Kumar, A.; Graves, R. A., Jr.

1980-01-01

A user's guide is provided for a computer code which calculates the laminar and turbulent hypersonic flows about blunt axisymmetric bodies, such as spherically blunted cones, hyperboloids, etc., at zero and small angles of attack. The code is written in STAR FORTRAN language for the CDC-STAR-100 computer. Time-dependent, viscous-shock-layer-type equations are used to describe the flow field. These equations are solved by an explicit, two-step, time asymptotic, finite-difference method. For the turbulent flow, a two-layer, eddy-viscosity model is used. The code provides complete flow-field properties including shock location, surface pressure distribution, surface heating rates, and skin-friction coefficients. This report contains descriptions of the input and output, the listing of the program, and a sample flow-field solution.

Gamma Ray Bursts as Cosmological Probes with EXIST

NASA Astrophysics Data System (ADS)

Hartmann, Dieter; EXIST Team

2006-12-01

The EXIST mission, studied as a Black Hole Finder Probe within NASA's Beyond Einstein Program, would, in its current design, trigger on 1000 Gamma Ray Bursts (GRBs) per year (Grindlay et al, this meeting). The redshift distribution of these GRBs, using results from Swift as a guide, would probe the z > 7 epoch at an event rate of > 50 per year. These bursts trace early cosmic star formation history, point to a first generation of stellar objects that reionize the universe, and provide bright beacons for absorption line studies with groundand space-based observatories. We discuss how EXIST, in conjunction with other space missions and future large survey programs such as LSST, can be utilized to advance our understanding of cosmic chemical evolution, the structure and evolution of the baryonic cosmic web, and the formation of stars in low metallicity environments.

Predicting the nature of supernova progenitors

NASA Astrophysics Data System (ADS)

Groh, Jose H.

2017-09-01

Stars more massive than about 8 solar masses end their lives as a supernova (SN), an event of fundamental importance Universe-wide. The physical properties of massive stars before the SN event are very uncertain, both from theoretical and observational perspectives. In this article, I briefly review recent efforts to predict the nature of stars before death, in particular, by performing coupled stellar evolution and atmosphere modelling of single stars in the pre-SN stage. These models are able to predict the high-resolution spectrum and broadband photometry, which can then be directly compared with the observations of core-collapse SN progenitors. The predictions for the spectral types of massive stars before death can be surprising. Depending on the initial mass and rotation, single star models indicate that massive stars die as red supergiants, yellow hypergiants, luminous blue variables and Wolf-Rayet stars of the WN and WO subtypes. I finish by assessing the detectability of SN Ibc progenitors. This article is part of the themed issue 'Bridging the gap: from massive stars to supernovae'.

NuSTAR on-ground calibration: II. Effective area

NASA Astrophysics Data System (ADS)

Brejnholt, Nicolai F.; Christensen, Finn E.; Westergaard, Niels J.; Hailey, Charles J.; Koglin, Jason E.; Craig, William W.

2012-09-01

The Nuclear Spectroscopic Telescope ARray (NuSTAR) was launched in June 2012 carrying the first focusing hard X-ray (5-80keV) optics to orbit. The multilayer coating was carried out at the Technical University of Denmark (DTU Space). In this article we introduce the NuSTAR multilayer reference database and its implementation in the NuSTAR optic response model. The database and its implementation is validated using on-ground effective area calibration data and used to estimate in-orbit performance.

Report Of The HST Strategy Panel: A Strategy For Recovery

DTIC Science & Technology

1991-01-01

orbit change out: the Wide Field/Planetary Camera II (WFPC II), the Near-Infrared Camera and Multi- Object Spectrometer (NICMOS) and the Space ...are the Space Telescope Imaging Spectrograph (STB), the Near-Infrared Camera and Multi- Object Spectrom- eter (NICMOS), and the second Wide Field and...expected to fail to lock due to duplicity was 20%; on- orbit data indicates that 10% may be a better estimate, but the guide stars were preselected

Fiber-linked telescope array: description and laboratory tests of a two-channel prototype

NASA Astrophysics Data System (ADS)

Alleman, J. J.; Reynaud, F.; Connes, P.

1995-05-01

We present a complete two-telescope version of a fiber-linked coherent array that is meant to be used for mounting on the dish of a radio telescope. This was built with 20-cm amateur telescopes and includes three different servo subsystems for guiding, nulling of the air path difference, and fiber length control. Laboratory tests of the fully integrated system in front of a star simulator are described.

Cosmic Feast of the Elements

NASA Astrophysics Data System (ADS)

Morisset, C.; Delgado-Inglada, G.; García-Rojas, J.

2017-11-01

In the past few decades most of our understanding of the history and chemical evolution of galaxies has been guided by the study of their stars and gaseous nebulae. Nebulae, thanks to their bright emission lines, are especially useful tracers of chemical elements from the very center to the outskirts of galaxies. In order to pin down the chemical abundances in nebulae, we must rely on careful analysis of emission lines combined with detailed models of the microscopic physical processes inside nebulae and state-of-the-art atomic data. Another important piece of the puzzle is the interplay between galaxy evolution and the activity of their central engines either as optical AGNs or radio jets. Last but not least, let us not forget the huge population of lineless, retired galaxies ionized by hot low-mass evolved stars: after nuclear and star formation activity quiets down, retired galaxies are the natural consequence of galaxy evolution. Grażyna Stasińska has made important contributions to each and every one of those aspects. This conference is to honor her work. We invite you to take part and share the latest news on this cosmic feast that transmutes chemical species, the onward journey of elements inside and outside galaxies either as lonely atoms or gregarious molecules and crystals, and their recycling in stars, which starts the cosmic feast all over again.

Distinct regulation of alternative polyadenylation and gene expression by nuclear poly(A) polymerases

PubMed Central

Li, Wencheng; Laishram, Rakesh S.; Hoque, Mainul; Ji, Zhe

2017-01-01

Abstract Polyadenylation of nascent RNA by poly(A) polymerase (PAP) is important for 3′ end maturation of almost all eukaryotic mRNAs. Most mammalian genes harbor multiple polyadenylation sites (PASs), leading to expression of alternative polyadenylation (APA) isoforms with distinct functions. How poly(A) polymerases may regulate PAS usage and hence gene expression is poorly understood. Here, we show that the nuclear canonical (PAPα and PAPγ) and non-canonical (Star-PAP) PAPs play diverse roles in PAS selection and gene expression. Deficiencies in the PAPs resulted in perturbations of gene expression, with Star-PAP impacting lowly expressed mRNAs and long-noncoding RNAs to the greatest extent. Importantly, different PASs of a gene are distinctly regulated by different PAPs, leading to widespread relative expression changes of APA isoforms. The location and surrounding sequence motifs of a PAS appear to differentiate its regulation by the PAPs. We show Star-PAP-specific PAS usage regulates the expression of the eukaryotic translation initiation factor EIF4A1, the tumor suppressor gene PTEN and the long non-coding RNA NEAT1. The Star-PAP-mediated APA of PTEN is essential for DNA damage-induced increase of PTEN protein levels. Together, our results reveal a PAS-guided and PAP-mediated paradigm for gene expression in response to cellular signaling cues. PMID:28911096

Perceived workplace mistreatment: Case of Latina hotel housekeepers.

PubMed

Hsieh, Yu-Chin Jerrie; Sönmez, Sevil; Apostolopoulos, Yorghos; Lemke, Michael Kenneth

2017-01-01

Latina hotel housekeepers' social class, gender, race/ethnicity, nationality, and United States immigration status render them particularly vulnerable to workplace mistreatment. We sought to reveal the array of policy- and interpersonal-related mistreatment experienced by Latina hotel housekeepers in the southeastern United States employed at 75 local hotels which included 4-star, 3-star, 2-star, and 1-star properties. This ethnographic study involved 27 in-depth interviews with Latina hotel housekeepers. Using semi-structured in-depth interview guides, participants were interviewed until collected data reached saturation. Data were coded to explore themes and relationships for the housekeepers' work environments, and thick descriptions of these environments were developed. Participants ranged in work experience from 1 to 15 years, with all but one unable to reach full-time status, and were paid between $7.25 and $8.00 per hour. Policy-related phenomena, such as low pay, lack of paid sick leave or overtime, and absence of appropriate cleaning tools or protective equipment were all perceived as forms of mistreatment by Latina hotel housekeepers. Interpersonal mistreatment in the form of supervisor favoritism, unfair work assignments, biased allocation of cleaning supplies, disrespect, and verbal abuse due to ethnicity was also perceived. Latina hotel housekeepers endure mistreatment that impacts their psychosocial and physical occupational health. We provide recommendations to minimize workplace mistreatment and improve well-being of Latina hotel housekeepers.

Modelling Kepler red giants in eclipsing binaries: calibrating the mixing-length parameter with asteroseismology

NASA Astrophysics Data System (ADS)

Li, Tanda; Bedding, Timothy R.; Huber, Daniel; Ball, Warrick H.; Stello, Dennis; Murphy, Simon J.; Bland-Hawthorn, Joss

2018-03-01

Stellar models rely on a number of free parameters. High-quality observations of eclipsing binary stars observed by Kepler offer a great opportunity to calibrate model parameters for evolved stars. Our study focuses on six Kepler red giants with the goal of calibrating the mixing-length parameter of convection as well as the asteroseismic surface term in models. We introduce a new method to improve the identification of oscillation modes that exploits theoretical frequencies to guide the mode identification (`peak-bagging') stage of the data analysis. Our results indicate that the convective mixing-length parameter (α) is ≈14 per cent larger for red giants than for the Sun, in agreement with recent results from modelling the APOGEE stars. We found that the asteroseismic surface term (i.e. the frequency offset between the observed and predicted modes) correlates with stellar parameters (Teff, log g) and the mixing-length parameter. This frequency offset generally decreases as giants evolve. The two coefficients a-1 and a3 for the inverse and cubic terms that have been used to describe the surface term correction are found to correlate linearly. The effect of the surface term is also seen in the p-g mixed modes; however, established methods for correcting the effect are not able to properly correct the g-dominated modes in late evolved stars.

Submillimeter Imaging of Dust Around Main Sequence Stars

NASA Technical Reports Server (NTRS)

Jewitt, David

1998-01-01

This grant was to image circumstellar dust disks surrounding main-sequence stars. The delivery of the SCUBA detector we had planned to use for this work was delayed repeatedly, leading us to undertake a majority of the observations with the UKT14 submillimeter detector at the JCMT (James Clerk Maxwell Telescope) and optical imagers and a coronagraph at the University of Hawaii 2.2-m telescope. Major findings under this grant include: (1) We discovered 5 asymmetries in the beta Pictoris regenerated dust disk. The discovery of these asymmetries was a surprise, since smearing due to Keplerian shear should eliminate most such features on timescales of a few thousand years. One exception is the "wing tilt" asymmetry, which we interpret as due to the scattering phase function of dust disk particles. From the wing tilt and a model of the phase function, we find a disk plane inclination to the line of sight of < 5 degrees. Other asymmetries (e.g. the butterfly asymmetry) suggest a disk that has been recently disturbed. We searched for possible nearby perturbers but found no clear candidates. Low mass stars (M dwarfs) and brown dwarfs would have fallen beneath the sensitivity threshhold of our survey, however. (2) We calculated a set of disk models to assess the detectability of dust disks around stars as a function of (a) distance, (b) disk, inclination (c) dust optical depth/mass, and (d) imaging resolution. These models guided our observational strategy on Mauna Kea. (3) We performed a coronagraphic survey of approx. 100 main-sequence stars in search of additional examples of circumstellar disks. The best new candidate disk, around the 5 M(sun) star BD+31deg.643, is distinguished by its large extent (few x 10( exp 3) AU). This disk, if real, cannot be rotationally supported. We suggest that the dust particles are ejected from a smaller, unseen disk (Kuiper Belt?) by strong radiation pressure forces due to the high luminosity central star. (4) SCUBA images of circumstellar dust disks were obtained at 850 gm in 1997/8. These images show extended, asymmetric emission, but have a signal-to-noise ratio too low to permit disk mapping to large projected distances. Our images of beta Pic, in particular, are in agreement with those obtained by Holland et al., and appear to confirm the blob-structure reported first by these authors. We have not yet been able to confirm that the structure is intrinsic to the disk, since beta Pic is at -50 degree declination, and suitable observing opportunities from northern latitudes are comparatively rare (even at the +20 degree latitude of JCMT). It is possible, for instance, that the main 850 micro-m blob is merely a galaxy or other high-z source projected onto the beta Pic mid-plane.

Innovative strategies for a successful SLMTA country programme: The Rwanda story

PubMed Central

Sebasirimu, Sabin; Gatabazi, John B.; Ruzindana, Emmanuel; Kayobotsi, Claver; Linde, Mary K.; Mazarati, Jean B.; Ntagwabira, Edouard; Serumondo, Janvier; Dahourou, Georges A.; Gatei, Wangeci; Muvunyi, Claude M.

2014-01-01

Background In 2009, to improve the performance of laboratories and strengthen healthcare systems, the World Health Organization Regional Office for Africa (WHO AFRO) and partners launched two initiatives: a laboratory quality improvement programme called Strengthening Laboratory Management Toward Accreditation (SLMTA), and what is now called the Stepwise Laboratory Quality Improvement Process Towards Accreditation (SLIPTA). Objectives This study describes the achievements of Rwandan laboratories four years after the introduction of SLMTA in the country, using the SLIPTA scoring system to measure laboratory progress. Methods Three cohorts of five laboratories each were enrolled in the SLMTA programme in 2010, 2011 and 2013. The cohorts used SLMTA workshops, improvement projects, mentorship and quarterly performance-based financing incentives to accelerate laboratory quality improvement. Baseline, exit and follow-up audits were conducted over a two-year period from the time of enrolment. Audit scores were used to categorise laboratory quality on a scale of zero (< 55%) to five (95% – 100%) stars. Results At baseline, 14 of the 15 laboratories received zero stars with the remaining laboratory receiving a two-star rating. At exit, five laboratories received one star, six received two stars and four received three stars. At the follow-up audit conducted in the first two cohorts approximately one year after exit, one laboratory scored two stars, five laboratories earned three stars and four laboratories, including the National Reference Laboratory, achieved four stars. Conclusion Rwandan laboratories enrolled in SLMTA showed improvement in quality management systems. Sustaining the gains and further expansion of the SLMTA programme to meet country targets will require continued programme strengthening. PMID:29043189

Design and DSP implementation of star image acquisition and star point fast acquiring and tracking

NASA Astrophysics Data System (ADS)

Zhou, Guohui; Wang, Xiaodong; Hao, Zhihang

2006-02-01

Star sensor is a special high accuracy photoelectric sensor. Attitude acquisition time is an important function index of star sensor. In this paper, the design target is to acquire 10 samples per second dynamic performance. On the basis of analyzing CCD signals timing and star image processing, a new design and a special parallel architecture for improving star image processing are presented in this paper. In the design, the operation moving the data in expanded windows including the star to the on-chip memory of DSP is arranged in the invalid period of CCD frame signal. During the CCD saving the star image to memory, DSP processes the data in the on-chip memory. This parallelism greatly improves the efficiency of processing. The scheme proposed here results in enormous savings of memory normally required. In the scheme, DSP HOLD mode and CPLD technology are used to make a shared memory between CCD and DSP. The efficiency of processing is discussed in numerical tests. Only in 3.5ms is acquired the five lightest stars in the star acquisition stage. In 43us, the data in five expanded windows including stars are moved into the internal memory of DSP, and in 1.6ms, five star coordinates are achieved in the star tracking stage.

Constraints on pre-main-sequence evolution from stellar pulsations

NASA Astrophysics Data System (ADS)

Casey, M. P.; Zwintz, K.; Guenther, D. B.

2014-02-01

Pulsating pre-main-sequence (PMS) stars afford the earliest opportunity in the lifetime of a star to which the concepts of asteroseismology can be applied. PMS stars should be structurally simpler than their evolved counterparts, thus (hopefully!) making any asteroseismic analysis relatively easier. Unfortunately, this isn't necessarily the case. The majority of these stars (around 80) are δ Scuti pulsators, with a couple of γ Doradus, γ Doradus - δ Scuti hybrids, and slowly pulsating B stars thrown into the mix. The majority of these stars have only been discovered within the last ten years, with the community still uncovering the richness of phenomena associated with these stars, many of which defy traditional asteroseismic analysis. A systematic asteroseismic analysis of all of the δ Scuti PMS stars was performed in order to get a better handle on the properties of these stars as a group. Some strange results have been found, including one star pulsating up to the theoretical acoustic cut-off frequency of the star, and a number of stars in which the most basic asteroseismic analysis suggests problems with the stars' positions in the Hertzsprung-Russell diagram. From this we get an idea of the\\break constraints - or lack thereof - that these results can put on PMS stellar evolution.

The BRITE spectropolarimetric survey

NASA Astrophysics Data System (ADS)

Neiner, C.; Lèbre, A.

2014-12-01

The BRITE constellation of nanosatellites observes very bright stars to perform seismology. We have set up a spectropolarimetric survey of all BRITE targets, i.e. all ˜600 stars brighter than V=4, with Narval at TBL, ESPaDOnS at CFHT and HarpsPol at ESO. We plan to reach a magnetic detection threshold of B_{pol} = 50 G for stars hotter than F5 and B_{pol} = 5 G for cooler stars. This program will allow us to combine magnetic information with the BRITE seismic information and obtain a better interpretation and modelling of the internal structure of the stars. It will also lead to new discoveries of very bright magnetic stars, which are unique targets for follow-up and multi-technique studies.

Method for star identification using neural networks

NASA Astrophysics Data System (ADS)

Lindsey, Clark S.; Lindblad, Thomas; Eide, Age J.

1997-04-01

Identification of star constellations with an onboard star tracker provides the highest precision of all attitude determination techniques for spacecraft. A method for identification of star constellations inspired by neural network (NNW) techniques is presented. It compares feature vectors derived from histograms of distances to multiple stars around the unknown star. The NNW method appears most robust with respect to position noise and would require a smaller database than conventional methods, especially for small fields of view. The neural network method is quite slow when performed on a sequential (serial) processor, but would provide very high speed if implemented in special hardware. Such hardware solutions could also yield lower low weight and low power consumption, both important features for small satellites.

Star Identification Without Attitude Knowledge: Testing with X-Ray Timing Experiment Data

NASA Technical Reports Server (NTRS)

Ketchum, Eleanor

1997-01-01

As the budget for the scientific exploration of space shrinks, the need for more autonomous spacecraft increases. For a spacecraft with a star tracker, the ability to determinate attitude from a lost in space state autonomously requires the capability to identify the stars in the field of view of the tracker. Although there have been efforts to produce autonomous star trackers which perform this function internally, many programs cannot afford these sensors. The author previously presented a method for identifying stars without a priori attitude knowledge specifically targeted for onboard computers as it minimizes the necessary computer storage. The method has previously been tested with simulated data. This paper provides results of star identification without a priori attitude knowledge using flight data from two 8 by 8 degree charge coupled device star trackers onboard the X-Ray Timing Experiment.

Astrometric Detection of Extrasolar Planets: Results of a Feasibility Study with the Palomar 5 Meter Telescope

NASA Technical Reports Server (NTRS)

Pravdo, Steven H.; Shaklan, Stuart B.

1996-01-01

The detection of extrasolar planets around stars like the Sun remains an important goal of astronomy. We present results from Palomar 5 m observations of the open cluster NGC 2420 in which we measure some of the sources of noise that will be present in an astrometric search for extrasolar planets. This is the first time that such a large aperture has been used for high-precision astrometry. We find that the atmospheric noise is 150 micro-arcsec hr(exp 1/2) across a 90 sec field of view and that differential chromatic refraction (DCR) can be calibrated to 128 micro-arcsec for observations within 1 hr of the meridian and 45 deg of zenith. These results confirm that a model for astrometric measurements can be extrapolated to large apertures. We demonstrate, based upon these results, that a large telescope achieves the sensitivity required to perform a statistically significant search for extra solar planets. We describe an astrometric technique to detect planets, the astrometric signals expected, the role of reference stars, and the sources of measurement noise: photometric noise, atmospheric motion between stars, sky background, instrumental noise, and DCR. For the latter, we discuss a method to reduce the noise further to 66 micro-arcsecond for observations within 1 hr of the meridian and 45 deg of zenith. We discuss optimal lists of target stars taken from the latest Gliese & Jahreiss catalog of nearby stars with the largest potential astrometric signals, declination limits for both telescope accessibility and reduced DCR, and galactic latitude limits for a sufficiant number of reference stars. Two samples are described from which one can perform statistically significant searches for gas giant planets around nearby stars. One sample contains 100 "solar class" stars with an average stellar mass of 0.82 solar mass; the other maximizes the number of stars, 574, by searching mainly low-mass M stars. We perform Monte Carlo simulations of the statistical significance of the expected results by using measured and estimated noise quantities. We show the semimajor axis parameter spaces that are searched for each star and how an increase in the length of the observing program expands these spaces. The search over semimajor axis parameter space relates to the theory of gas giant planet formation.

Searching for Young M Dwarfs with GALEX

NASA Astrophysics Data System (ADS)

Shkolnik, Evgenya L.; Liu, Michael C.; Reid, I. Neill; Dupuy, Trent; Weinberger, Alycia J.

2011-01-01

The census of young moving groups in the solar neighborhood is significantly incomplete in the low-mass regime. We have developed a new selection process to find these missing members based on the Galaxy Evolution Explorer (GALEX) All-Sky Imaging Survey (AIS). For stars with spectral types gsimK5 (R - J >~ 1.5) and younger than ≈300 Myr, we show that near-UV (NUV) and far-UV (FUV) emission is greatly enhanced above the quiescent photosphere, analogous to the enhanced X-ray emission of young low-mass stars seen by ROSAT but detectable to much larger distances with GALEX. By combining GALEX data with optical (HST Guide Star Catalog) and near-IR (2MASS) photometry, we identified an initial sample of 34 young M dwarf candidates in a 1000 deg2 region around the ≈10 Myr TW Hydra Association (TWA). Low-resolution spectroscopy of 30 of these found 16 which had Hα in emission, which were then followed up at high resolution to search for spectroscopic evidence of youth and to measure their radial velocities. Four objects have low surface gravities, photometric distances and space motions consistent with TWA, but the non-detection of Li indicates that they may be too old to belong to this moving group. One object (M3.5, 93 ± 19 pc) appears to be the first known accreting low-mass member of the ≈15 Myr Lower Centaurus Crux OB association. Two objects exhibit all the characteristics of the known TWA members, and thus we designate them as TWA 31 (M4.2, 110 ± 11 pc) and TWA 32 (M6.3, 53 ± 5 pc). TWA 31 shows extremely broad (447 km s-1) Hα emission, making it the sixth member of TWA found to have ongoing accretion. TWA 32 is resolved into a 0farcs6 binary in Keck laser guide star adaptive optics imaging. Our search should be sensitive down to spectral types of at least M4-M5 in TWA and thus the small numbers of new member is puzzling. This might indicate TWA has an atypical mass function or that the presence of lithium absorption may be too restrictive a criteria for selecting young low-mass stars. This paper is based on data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile, the Keck II telescope, and the GALEX, 2MASS, and HST/GSC v2.3 photometric catalogs. GALEX is operated for NASA by the California Institute of Technology under NASA contract NAS5-98034.

Advanced Metrics for Assessing Holistic Care: The "Epidaurus 2" Project.

PubMed

Foote, Frederick O; Benson, Herbert; Berger, Ann; Berman, Brian; DeLeo, James; Deuster, Patricia A; Lary, David J; Silverman, Marni N; Sternberg, Esther M

2018-01-01

In response to the challenge of military traumatic brain injury and posttraumatic stress disorder, the US military developed a wide range of holistic care modalities at the new Walter Reed National Military Medical Center, Bethesda, MD, from 2001 to 2017, guided by civilian expert consultation via the Epidaurus Project. These projects spanned a range from healing buildings to wellness initiatives and healing through nature, spirituality, and the arts. The next challenge was to develop whole-body metrics to guide the use of these therapies in clinical care. Under the "Epidaurus 2" Project, a national search produced 5 advanced metrics for measuring whole-body therapeutic effects: genomics, integrated stress biomarkers, language analysis, machine learning, and "Star Glyphs." This article describes the metrics, their current use in guiding holistic care at Walter Reed, and their potential for operationalizing personalized care, patient self-management, and the improvement of public health. Development of these metrics allows the scientific integration of holistic therapies with organ-system-based care, expanding the powers of medicine.

Adaptive Neural Star Tracker Calibration for Precision Spacecraft Pointing and Tracking

NASA Technical Reports Server (NTRS)

Bayard, David S.

1996-01-01

The Star Tracker is an essential sensor for precision pointing and tracking in most 3-axis stabilized spacecraft. In the interest (of) improving pointing performance by taking advantage of dramatic increases in flight computer power and memory anticipated over the next decade, this paper investigates the use of a neural net for adaptive in-flight calibration of the Star Tracker.

Boeing Satellite Television Airplane Receiving System (STARS) performance

NASA Technical Reports Server (NTRS)

Vertatschitsch, Edward J.; Fitzsimmons, George W.

1995-01-01

Boeing Defense and Space Group is developing a Satellite Television Airplane Receiving System (STARS) capable of delivering Direct Broadcast Satellite (DBS) television to an aircraft in-flight. This enables a new service for commercial airplanes that will make use of existing and future DBS systems. The home entertainment satellites, along with STARS, provide a new mobile satellite communication application. This paper will provide a brief background of the antenna issues associated with STARS for commercial airplanes and then describe the innovative Boeing phased-array solution to these problems. The paper then provides a link budget of the STARS using the Hughes DBS as an example, but the system will work with all of the proposed DBS satellites in the 12.2-12.7 GHz band. It concludes with operational performance calculations of the STARS system, supported by measured test data of an operational 16-element subarray. Although this system is being developed for commercial airplanes, it is well suited for a wide variety of mobile military and other commercial communications systems in air, on land and at sea. The applications include sending high quality video for the digital battlefield and large volumes of data on the information superhighway at rates in excess of 350 Mbps.

Inside NuSTAR Nose Cone

NASA Image and Video Library

2012-03-02

A spacecraft technician is performing closeout work inside the fairing that will be installed around NASA Nuclear Spectroscopic Telescope Array NuSTAR spacecraft in a processing facility at Vandenberg Air Force Base in California.

Mission hazard assessment for STARS Mission 1 (M1) in the Marshall Islands area

DOE Office of Scientific and Technical Information (OSTI.GOV)

Outka, D.E.; LaFarge, R.A.

1993-07-01

A mission hazard assessment has been performed for the Strategic Target System Mission 1 (known as STARS M1) for hazards due to potential debris impact in the Marshall Islands area. The work was performed at Sandia National Laboratories as a result of discussion with Kwajalein Missile Range (KMR) safety officers. The STARS M1 rocket will be launched from the Kauai Test Facility (KTF), Hawaii, and deliver two payloads to within the viewing range of sensors located on the Kwajalein Atoll. The purpose of this work has been to estimate upper bounds for expected casualty rates and impact probability or themore » Marshall Islands areas which adjoin the STARS M1 instantaneous impact point (IIP) trace. This report documents the methodology and results of the analysis.« less

The Development of a Data Archive and Analysis Tools for WIRE

NASA Technical Reports Server (NTRS)

Buzasi, Derek L.

2002-01-01

Although a number of missions to perform asteroseismology from orbit are planned, such as the French COROT (currently scheduled for launch in 2004), the Canadian MOST (2002), and the Danish MONS (2003), none has yet been successfully flown. However, from May 1999 through September 2000, the PI of this proposal initiated a program using the star camera on board the WIRE spacecraft to perform high-precision photometry of solar-like and giant stars. This program relied on the on-board star camera, which consists of a 50mm f/1.75 telescope feeding a 512(sup 2) SITe CCD, which can be read out at rates as high as 10 Hz. The high cadence of observations available with this star camera is made possible by software that locates the 5 brightest stars in the field and reads only an 8x8 pixel box around one selected image. An additional mode of operation, available since November 1999, makes count rate data available on all five stellar images, with a consequent loss of read rate (to 2 Hz for 5 stars). Stellar images are defocused (to allow for more accurate image centroiding), but the entire stellar image lies within the 64-pixel box. we note that in many ways, this instrument is similar to the French instrument EVRIS, which was intended to perform asteroseismology with a 90 mm telescope, but which unfortunately flew as part of the failed Russian MARS 96 spacecraft.

Comparison of the T2-star Values of Placentas Obtained from Pre-eclamptic Patients with Those of a Control Group: an Ex-vivo Magnetic Resonance Imaging Study.

PubMed

Yurttutan, Nursel; Bakacak, Murat; Kızıldağ, Betül

2017-09-29

Endotel dysfunction, vasoconstriction, and oxidative stress are described in the pathophysiology of pre-eclampsia, but its aetiology has not been revealed clearly. To examine whether there is a difference between the placentas of pre-eclamptic pregnant women and those of a control group in terms of their T2 star values. Case-control study. Twenty patients diagnosed with pre-eclampsia and 22 healthy controls were included in this study. The placentas obtained after births performed via Caesarean section were taken into the magnetic resonance imaging area in plastic bags within the first postnatal hour, and imaging was performed via modified DIXON-Quant sequence. Average values were obtained by performing T2 star measurements from four localisations on the placentas. T2 star values measured in the placentas of the control group were found to be significantly lower than those in the pre-eclampsia group (p<0.01). While the mean T2 star value in the pre-eclamptic group was found to be 37.48 ms (standard deviation ± 11.3), this value was 28.74 (standard deviation ± 8.08) in the control group. The cut-off value for the T2 star value, maximising the accuracy of diagnosis, was 28.59 ms (area under curve: 0.741; 95% confidence interval: 0.592-0.890); sensitivity and specificity were 70% and 63.6%, respectively. This study, the T2 star value, which is an indicator of iron amount, was found to be significantly lower in the control group than in the pre-eclampsia group. This may be related to the reduction in blood flow to the placenta due to endothelial dysfunction and vasoconstriction, which are important in pre-eclampsia pathophysiology.

Star cluster formation in a turbulent molecular cloud self-regulated by photoionization feedback

NASA Astrophysics Data System (ADS)

Gavagnin, Elena; Bleuler, Andreas; Rosdahl, Joakim; Teyssier, Romain

2017-12-01

Most stars in the Galaxy are believed to be formed within star clusters from collapsing molecular clouds. However, the complete process of star formation, from the parent cloud to a gas-free star cluster, is still poorly understood. We perform radiation-hydrodynamical simulations of the collapse of a turbulent molecular cloud using the RAMSES-RT code. Stars are modelled using sink particles, from which we self-consistently follow the propagation of the ionizing radiation. We study how different feedback models affect the gas expulsion from the cloud and how they shape the final properties of the emerging star cluster. We find that the star formation efficiency is lower for stronger feedback models. Feedback also changes the high-mass end of the stellar mass function. Stronger feedback also allows the establishment of a lower density star cluster, which can maintain a virial or sub-virial state. In the absence of feedback, the star formation efficiency is very high, as well as the final stellar density. As a result, high-energy close encounters make the cluster evaporate quickly. Other indicators, such as mass segregation, statistics of multiple systems and escaping stars confirm this picture. Observations of young star clusters are in best agreement with our strong feedback simulation.

Development of a Robust star identification technique for use in attitude determination of the ACE spacecraft

NASA Technical Reports Server (NTRS)

Woodard, Mark; Rohrbaugh, Dave

1995-01-01

The Advanced Composition Explorer (ACE) spacecraft is designed to fly in a spin-stabilized attitude. The spacecraft will carry two attitude sensors - a digital fine Sun sensor and a charge coupled device (CCD) star tracker - to allow ground-based determination of the spacecraft attitude and spin rate. Part of the processing that must be performed on the CCD star tracker data is the star identification. Star data received from the spacecraft must be matched with star information in the SKYMAP catalog to determine exactly which stars the sensor is tracking. This information, along with the Sun vector measured by the Sun sensor, is used to determine the spacecraft attitude. Several existing star identification (star ID) systems were examined to determine whether they could be modified for use on the ACE mission. Star ID systems which exist for three-axis stabilized spacecraft tend to be complex in nature and many require fairly good knowledge of the spacecraft attitude, making their use for ACE excessive. Star ID systems used for spinners carrying traditional slit star sensors would have to be modified to model the CCD star tracker. The ACE star ID algorithm must also be robust, in that it will be able to correctly identify stars even though the attitude is not known to a high degree of accuracy, and must be very efficient to allow real-time star identification. The paper presents the star ID algorithm that was developed for ACE. Results from prototype testing are also presented to demonstrate the efficiency, accuracy, and robustness of the algorithm.

Overview of NASA's Space Solar Power Technology Advanced Research and Development Program

NASA Technical Reports Server (NTRS)

Howell, Joe; Mankins, John C.; Davis, N. Jan (Technical Monitor)

2001-01-01

Large solar power satellite (SPS) systems that might provide base load power into terrestrial markets were examined extensively in the 1970s by the US Department of Energy (DOE) and the National Aeronautics and Space Administration (NASA). Following a hiatus of about 15 years, the subject of space solar power (SSP) was reexamined by NASA from 1995-1997 in the 'fresh look' study, and during 1998 in an SSP 'concept definition study', and during 1999-2000 in the SSP Exploratory Research and Technology (SERT) program. As a result of these efforts, during 2001, NASA has initiated the SSP Technology Advanced Research and Development (STAR-Dev) program based on informed decisions. The goal of the STAR-Dev program is to conduct preliminary strategic technology research and development to enable large, multi-megawatt to gigawatt-class space solar power (SSP) systems and wireless power transmission (WPT) for government missions and commercial markets (in-space and terrestrial). Specific objectives include: (1) Release a NASA Research Announcement (NRA) for SSP Projects; (2) Conduct systems studies; (3) Develop Component Technologies; (4) Develop Ground and Flight demonstration systems; and (5) Assess and/or Initiate Partnerships. Accomplishing these objectives will allow informed future decisions regarding further SSP and related research and development investments by both NASA management and prospective external partners. In particular, accomplishing these objectives will also guide further definition of SSP and related technology roadmaps including performance objectives, resources and schedules; including 'multi-purpose' applications (commercial, science, and other government).

Condensation of refractory metals in asymptotic giant branch and other stellar environments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schwander, D.; Berg, T.; Schönhense, G.

2014-09-20

The condensation of material from a gas of solar composition has been extensively studied, but less so condensation in the environment of evolved stars, which has been mainly restricted to major compounds and some specific element groups such as the Rare Earth elements. Also of interest, however, are refractory metals like Mo, Ru, Os, W, Ir, and Pt, which may condense to form refractory metal nuggets (RMNs) like the ones that have been found in association with presolar graphite. We have performed calculations describing the condensation of these elements in the outflows of s-process enriched AGB stars as well asmore » from gas enriched in r-process products. While in carbon-rich environments (C > O), the formation of carbides is expected to consume W, Mo, and V (Lodders and Fegley), the condensation sequence for the other refractory metals under these conditions does not significantly differ from the case of a cooling gas of solar composition. The composition in detail, however, is significantly different due to the completely different source composition. Condensation from an r-process enriched source differs less from the solar case. Elemental abundance ratios of the refractory metals can serve as a guide for finding candidate presolar grains among the RMNs in primitive meteorites—most of which have a solar system origin—for confirmation by isotopic analysis. We apply our calculations to the case of the four RMNs found by Croat et al., which may very well be presolar.« less

The neural representation of social status in the extended face-processing network.

PubMed

Koski, Jessica E; Collins, Jessica A; Olson, Ingrid R

2017-12-01

Social status is a salient cue that shapes our perceptions of other people and ultimately guides our social interactions. Despite the pervasive influence of status on social behavior, how information about the status of others is represented in the brain remains unclear. Here, we tested the hypothesis that social status information is embedded in our neural representations of other individuals. Participants learned to associate faces with names, job titles that varied in associated status, and explicit markers of reputational status (star ratings). Trained stimuli were presented in an functional magnetic resonance imaging experiment where participants performed a target detection task orthogonal to the variable of interest. A network of face-selective brain regions extending from the occipital lobe to the orbitofrontal cortex was localized and served as regions of interest. Using multivoxel pattern analysis, we found that face-selective voxels in the lateral orbitofrontal cortex - a region involved in social and nonsocial valuation, could decode faces based on their status. Similar effects were observed with two different status manipulations - one based on stored semantic knowledge (e.g., different careers) and one based on learned reputation (e.g., star ranking). These data suggest that a face-selective region of the lateral orbitofrontal cortex may contribute to the perception of social status, potentially underlying the preferential attention and favorable biases humans display toward high-status individuals. © 2017 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

The detection of planetary systems from Space Station - A star observation strategy

NASA Technical Reports Server (NTRS)

Mascy, Alfred C.; Nishioka, Ken; Jorgensen, Helen; Swenson, Byron L.

1987-01-01

A 10-20-yr star-observation program for the Space Station Astrometric Telescope Facility (ATF) is proposed and evaluated by means of computer simulations. The primary aim of the program is to detect stars with planetary systems by precise determination of their motion relative to reference stars. The designs proposed for the ATF are described and illustrated; the basic parameters of the 127 stars selected for the program are listed in a table; spacecraft and science constraints, telescope slewing rates, and the possibility of limiting the program sample to stars near the Galactic equator are discussed; and the effects of these constraints are investigated by simulating 1 yr of ATF operation. Viewing all sky regions, the ATF would have 81-percent active viewing time, observing each star about 200 times (56 h) per yr; only small decrements in this performance would result from limiting the viewing field.

Cygnus OB2: Star Formation Ugly Duckling Causes a Flap

NASA Astrophysics Data System (ADS)

Drake, Jeremy J.; Wright, Nicholas; Guarcello, Mario

2015-08-01

Cygnus OB2 is one of the largest known OB associations in our Galaxy, with a total stellar mass of 30,000 Msun and boasting an estimated 65 O-type stars and hundreds of OB stars. At a distance of only 1.4kpc, it is also the closest truly massive star forming region and provides a valuable testbed for star and planet formation theory. We have performed a deep stellar census using observations from X-ray to infrared, which has enabled studies of sub-structuring, mass segregation and dynamics, while infrared data reveal a story of protoplanetary disk attrition in an extremely harsh radiation environment. I will discuss how Cygnus OB2 challenges the idea that stars must form in dense, compact clusters, and demonstrates that stars as massive as 100 Msun can form in relatively low-density environments. Convincing evidence of disk photoevaporation poses a potential problem for planet formation and growth in starburst environments.

Multipurpose active pixel sensor (APS)-based microtracker

NASA Astrophysics Data System (ADS)

Eisenman, Allan R.; Liebe, Carl C.; Zhu, David Q.

1998-12-01

A new, photon-sensitive, imaging array, the active pixel sensor (APS) has emerged as a competitor to the CCD imager for use in star and target trackers. The Jet Propulsion Laboratory (JPL) has undertaken a program to develop a new generation, highly integrated, APS-based, multipurpose tracker: the Programmable Intelligent Microtracker (PIM). The supporting hardware used in the PIM has been carefully selected to enhance the inherent advantages of the APS. Adequate computation power is included to perform star identification, star tracking, attitude determination, space docking, feature tracking, descent imaging for landing control, and target tracking capabilities. Its first version uses a JPL developed 256 X 256-pixel APS and an advanced 32-bit RISC microcontroller. By taking advantage of the unique features of the APS/microcontroller combination, the microtracker will achieve about an order-of-magnitude reduction in mass and power consumption compared to present state-of-the-art star trackers. It will also add the advantage of programmability to enable it to perform a variety of star, other celestial body, and target tracking tasks. The PIM is already proving the usefulness of its design concept for space applications. It is demonstrating the effectiveness of taking such an integrated approach in building a new generation of high performance, general purpose, tracking instruments to be applied to a large variety of future space missions.

Comparison of the Shack-Hartmann and plenoptic sensor in closed-loop adaptive optics system

NASA Astrophysics Data System (ADS)

Jiang, Pengzhi; Xu, Jieping; Liang, Yonghui; Mao, Hongjun

2016-03-01

The wavefront sensor is used in adaptive optics (AO) to detect the atmospheric distortion, which feeds back to the deformable mirror to compensate for this distortion. While the Shack-Hartmann sensor has been widely used, the plenoptic sensor was proposed in recent years. The two different wavefront sensing methods have different interpretations and numerical consequences, though they are both slope-based. The plenoptic sensor is compared with the Shack-Hartmann sensor in a closed-loop AO system. Simulations are performed to investigate their performances under closed-loop conditions. The plenoptic sensors both without and with modulation are discussed. The results show that the closed-loop performance of the plenoptic sensor without modulation is worse than that of the Shack-Hartmann sensor when the star for observation is brighter than magnitude 7, but better when the star is fainter. The closed-loop performance of the plenoptic sensor could be improved by modulation, except for the faint star. In summary, the limiting magnitude of the astronomical AO system may be improved by using the plenoptic sensor instead of the Shack-Hartmann sensor, and the modulation of the plenoptic sensor is more suitable for the bright star.

Data Characterization Using Artificial-Star Tests: Performance Evaluation

NASA Astrophysics Data System (ADS)

Hu, Yi; Deng, Licai; de Grijs, Richard; Liu, Qiang

2011-01-01

Traditional artificial-star tests are widely applied to photometry in crowded stellar fields. However, to obtain reliable binary fractions (and their uncertainties) of remote, dense, and rich star clusters, one needs to recover huge numbers of artificial stars. Hence, this will consume much computation time for data reduction of the images to which the artificial stars must be added. In this article, we present a new method applicable to data sets characterized by stable, well-defined, point-spread functions, in which we add artificial stars to the retrieved-data catalog instead of to the raw images. Taking the young Large Magellanic Cloud cluster NGC 1818 as an example, we compare results from both methods and show that they are equivalent, while our new method saves significant computational time.

SED16 autonomous star tracker night sky testing

NASA Astrophysics Data System (ADS)

Foisneau, Thierry; Piriou, Véronique; Perrimon, Nicolas; Jacob, Philippe; Blarre, Ludovic; Vilaire, Didier

2017-11-01

The SED16 is an autonomous multi-missions star tracker which delivers three axis satellite attitude in an inertial reference frame and the satellite angular velocity with no prior information. The qualification process of this star sensor includes five validation steps using optical star simulator, digitized image simulator and a night sky tests setup. The night sky testing was the final step of the qualification process during which all the functions of the star tracker were used in almost nominal conditions : Autonomous Acquisition of the attitude, Autonomous Tracking of ten stars. These tests were performed in Calern in the premises of the OCA (Observatoire de la Cote d'Azur). The test set-up and the test results are described after a brief review of the sensor main characteristics and qualification process.

KSC-02pd1537

NASA Image and Video Library

2002-10-15

KENNEDY SPACE CENTER, FLA. -- Workers on the deck of the Liberty Star, one of NASA's solid rocket booster retrieval ships, help guide sonar mapping equipment toward the side of the ship. The equipment will be attached to the ship's hull for an eight-day expedition surveying deep-water coral reefs on the Oculina Banks off eastern Florida. NASA joins the National Oceanic and Atmospheric Administration (NOAA) and other ocean scientists for the sophisticated mapping system that will provide the first high-resolution, three-dimensional map of the Oculina Banks. The survey results are expected to guide another expedition in Spring 2003, using NASA's ship, when the reef fish spawn. Also used will be NASA's underwater robot and an acoustic hydrophone system for listening to fish and vessel noise. Dive sites will be chosen based on the new charts.

Ancient Earth, Alien Earths Event

NASA Image and Video Library

2014-08-20

An audience member asks the panelists a question at the “Ancient Earth, Alien Earths” Event at NASA Headquarters in Washington, DC Wednesday, August 20, 2014. The event was sponsored by NASA, the National Science Foundation (NSF), and the Smithsonian Institution and was moderated by Dr. David H. Grinspoon, Senior Scientist at the Planetary Science Institute. Six scientists discussed how research on early Earth could help guide our search for habitable planets orbiting other stars. Photo Credit: (NASA/Aubrey Gemignani)

Point spread function reconstruction validated using on-sky CANARY data in multiobject adaptive optics mode

NASA Astrophysics Data System (ADS)

Martin, Olivier A.; Correia, Carlos M.; Gendron, Eric; Rousset, Gerard; Gratadour, Damien; Vidal, Fabrice; Morris, Tim J.; Basden, Alastair G.; Myers, Richard M.; Neichel, Benoit; Fusco, Thierry

2016-10-01

In preparation of future multiobject spectrographs (MOS) whose one of the major role is to provide an extensive statistical studies of high redshifted galaxies surveyed, the demonstrator CANARY has been designed to tackle technical challenges related to open-loop adaptive optics (AO) control with jointed Natural Guide Star and Laser Guide Star tomography. We have developed a point spread function (PSF) reconstruction algorithm dedicated to multiobject adaptive optics systems using system telemetry to estimate the PSF potentially anywhere in the observed field, a prerequisite to postprocess AO-corrected observations in integral field spectroscopy. We show how to handle off-axis data to estimate the PSF using atmospheric tomography and compare it to a classical approach that uses on-axis residual phase from a truth sensor observing a natural bright source. We have reconstructed over 450 on-sky CANARY PSFs and we get bias/1-σ standard-deviation (std) of 1.3/4.8 on the H-band Strehl ratio (SR) with 92.3% of correlation between reconstructed and sky SR. On the full-width at half-maximum, we get, respectively, 2.94 mas, 19.9 mas, and 88.3% for the bias, std, and correlation. The reference method achieves 0.4/3.5/95% on the SR and 2.71 mas/14.9 mas/92.5% on the FWHM for the bias/std/correlation.

Short-course Astronomical Research Seminars for High School and College Students

NASA Astrophysics Data System (ADS)

Johnson, Jolyon

2011-05-01

Since 2008, I have helped lead several short-course astronomical research seminars with Russell M. Genet. These seminars have ranged from semester-long courses at Cuesta College in San Luis Obispo, California to long weekends at the University of Oregon's Pine Mountain Observatory. Each seminar is led by an experienced observer or group of observers who guide high school and college students through the scientific process from observations to publication. The students (anywhere from half a dozen to twenty in number) participate in and contribute to every step. Being a coauthor on one or more research papers offers students an advantage on college and scholarship applications. Similarly, graduate schools often prefer students with research experience. Many topics of research are appropriate for these short-courses including variable star, exoplanet, and asteroid photometry. However, the most successful topic has been visual double stars because the observations required are straitforward and the equipment is relatively inexpensive. The Journal of Double Star Observations is also welcoming of student research and provides swift publication. A detailed description of the short-course seminars can be found in the recent Collins Foundation Press volume titled Small Telescopes and Astronomical Research.

A 1,574-Day Periodicity of Transits Orbiting KIC 8462852

NASA Astrophysics Data System (ADS)

Sacco, G.; Ngo, L. D.; Modolo, J.

2018-06-01

Observations of the main sequence F3V star KIC 8462852 (also known as Boyajianís star) revealed extreme aperiodic dips in flux up to 20% during the four years of the Kepler mission. Smaller dips (< 3%) were also observed with ground-based telescopes between May 2017 and May 2018. We investigated possible correlation between recent dips and the major dips in the last 100 days of the Kepler mission. We compared Kepler light curve data, 2017 data from two observatories (TFN, OGG) which are part of the Las Cumbres Observatory (LCO) network, as well as archival data from the Harvard College Observatory (HCO), Sonneberg Observatory, and Sternberg Observatory, and determined that observations appear consistent with a 1,574-day (4.31-year) periodicity of a transit (or group of transits) orbiting Boyajianís star within the habitable zone. Comparison with future observations is required to validate this hypothesis. Furthermore, it is unknown if transits that have produced other major dips as observed during the Kepler mission (e.g. D792) share the same orbital period. Nevertheless, the proposed periodicity is a step forward in guiding future observation efforts.

10 CFR Appendix U to Subpart B of... - Uniform Test Method for Measuring the Energy Consumption of Ceiling Fans

Code of Federal Regulations, 2013 CFR

2013-01-01

... Test Procedure,” and Chapter 6, “Definitions and Acronyms,” of the EPA's “ENERGY STAR Testing Facility Guidance Manual: Building a Testing Facility and Performing the Solid State Test Method for ENERGY STAR... specified in Chapter 4, “Equipment Setup and Test Procedure,” of the EPA's “ENERGY STAR Testing Facility...

10 CFR Appendix U to Subpart B of... - Uniform Test Method for Measuring the Energy Consumption of Ceiling Fans

Code of Federal Regulations, 2012 CFR

2012-01-01

... Test Procedure,” and Chapter 6, “Definitions and Acronyms,” of the EPA's “ENERGY STAR Testing Facility Guidance Manual: Building a Testing Facility and Performing the Solid State Test Method for ENERGY STAR... specified in Chapter 4, “Equipment Setup and Test Procedure,” of the EPA's “ENERGY STAR Testing Facility...

10 CFR Appendix U to Subpart B of... - Uniform Test Method for Measuring the Energy Consumption of Ceiling Fans

Code of Federal Regulations, 2014 CFR

2014-01-01

... Test Procedure,” and Chapter 6, “Definitions and Acronyms,” of the EPA's “ENERGY STAR Testing Facility Guidance Manual: Building a Testing Facility and Performing the Solid State Test Method for ENERGY STAR... specified in Chapter 4, “Equipment Setup and Test Procedure,” of the EPA's “ENERGY STAR Testing Facility...

10 CFR Appendix U to Subpart B of... - Uniform Test Method for Measuring the Energy Consumption of Ceiling Fans

Code of Federal Regulations, 2011 CFR

2011-01-01

... Test Procedure,” and Chapter 6, “Definitions and Acronyms,” of the EPA's “ENERGY STAR Testing Facility Guidance Manual: Building a Testing Facility and Performing the Solid State Test Method for ENERGY STAR... specified in Chapter 4, “Equipment Setup and Test Procedure,” of the EPA's “ENERGY STAR Testing Facility...

Ground Testing Strategies for Verifying the Slew Rate Tolerance of Star Trackers

PubMed Central

Dzamba, Tom; Enright, John

2014-01-01

The performance of a star tracker is largely based on the availability of its attitude solution. Several methods exist to assess star tracker availability under both static and dynamic imaging conditions. However, these methods typically make various idealizations that can limit the accuracy of these results. This study aims to increase the fidelity of star tracker availability modeling by accounting for the effects of detection logic and pixel saturation on star detection. We achieve this by developing an analytical model for the focal plane intensity distribution of a star in the presence of sensor slew. Using the developed model, we examine the effects of slew rate on star detection using simulations and lab tests. The developed approach allows us to determine the maximum slew rate for which a star of a given stellar magnitude can still be detected. This information can then be used to describe the availability of a star tracker attitude solution as a function of slew rate, both spatially, across the entire celestial sphere, or locally, along a specified orientation track. PMID:24577522

Predicting the nature of supernova progenitors.

PubMed

Groh, Jose H

2017-10-28

Stars more massive than about 8 solar masses end their lives as a supernova (SN), an event of fundamental importance Universe-wide. The physical properties of massive stars before the SN event are very uncertain, both from theoretical and observational perspectives. In this article, I briefly review recent efforts to predict the nature of stars before death, in particular, by performing coupled stellar evolution and atmosphere modelling of single stars in the pre-SN stage. These models are able to predict the high-resolution spectrum and broadband photometry, which can then be directly compared with the observations of core-collapse SN progenitors. The predictions for the spectral types of massive stars before death can be surprising. Depending on the initial mass and rotation, single star models indicate that massive stars die as red supergiants, yellow hypergiants, luminous blue variables and Wolf-Rayet stars of the WN and WO subtypes. I finish by assessing the detectability of SN Ibc progenitors.This article is part of the themed issue 'Bridging the gap: from massive stars to supernovae'. © 2017 The Author(s).

Impact of gaps in the asteroseismic characterization of pulsating stars. I. The efficiency of pre-whitening

NASA Astrophysics Data System (ADS)

Pascual-Granado, J.; Suárez, J. C.; Garrido, R.; Moya, A.; Hernández, A. García; Rodón, J. R.; Lares-Martiz, M.

2018-06-01

Context. It is known that the observed distribution of frequencies in CoRoT and Kepler δ Scuti stars has no parallelism with any theoretical model. Pre-whitening is a widespread technique in the analysis of time series with gaps from pulsating stars located in the classical instability strip, such as δ Scuti stars. However, some studies have pointed out that this technique might introduce biases in the results of the frequency analysis. Aims: This work aims at studying the biases that can result from pre-whitening in asteroseismology. The results will depend on the intrinsic range and distribution of frequencies of the stars. The periodic nature of the gaps in CoRoT observations, only in the range of the pulsational frequency content of the δ Scuti stars, is shown to be crucial to determining their oscillation frequencies, the first step in performing asteroseismology of these objects. Hence, here we focus on the impact of pre-whitening on the asteroseismic characterization of δ Scuti stars. Methods: We select a sample of 15 δ Scuti stars observed by the CoRoT satellite, for which ultra-high-quality photometric data have been obtained by its seismic channel. In order to study the impact on the asteroseismic characterization of δ Scuti stars we perform the pre-whitening procedure on three datasets: gapped data, linearly interpolated data, and data with gaps interpolated using Autoregressive and Moving Average models (ARMA). Results: The different results obtained show that at least in some cases pre-whitening is not an efficient procedure for the deconvolution of the spectral window. Therefore, in order to reduce the effect of the spectral window to a minimum, in addition to performing a pre-whitening of the data, it is necessary to interpolate with an algorithm that is aimed to preserve the original frequency content. Tables 5-49 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/614/A40

Community pharmacists' beliefs regarding improvement of Star Ratings scores using the Theory of Planned Behavior.

PubMed

George, David L; Smith, Michael J; Draugalis, JoLaine R; Tolma, Eleni L; Keast, Shellie L; Wilson, Justin B

The Centers for Medicare and Medicaid Services (CMS) is moving toward a value-based model, which includes the Five-Star Quality Rating System (Star Ratings). Prescription Drug Plans include multiple pharmacy measures associated with adherence and patient safety that contribute to CMS Star Ratings scores. This study, using the Theory of Planned Behavior (TPB), explored factors associated with community pharmacists' beliefs to improve Star Ratings scores. Exploratory, qualitative, use of focus groups, and the TPB. Focus groups were performed in conference rooms at the College of Pharmacy main and satellite campuses. Participants were community retail pharmacists with an active Oklahoma license and 1 year of work experience. Each focus group was audio recorded and the recording transcribed to documents and analyzed with the use of a hybrid deductive and inductive qualitative approach rooted in a constant comparative framework. Coding of the data back to the TPB constitutes a deductive approach. The generation of themes and subthemes from other coded nodes constitutes an inductive approach. Analysts agreed on common themes, differences in findings, and saturation of the data gathered. Four focus groups were conducted with 26 participants in 2 categories: pharmacists with and without experience improving Star Ratings. Pharmacists shared and contrasted in salient, normative, and control beliefs about patient outcomes, data, financial implications, staff, technology, and other stakeholders associated with performance of improving Star Ratings. Themes regarding medication adherence, patient safety, and intention were also found. The TPB was used to explore beliefs of community pharmacists about improving Star Ratings scores. Themes that were identified will assist in future research for measuring intention to improve CMS Star Ratings scores and the development of training and education programs. Published by Elsevier Inc.

New determination of the solar apex

NASA Astrophysics Data System (ADS)

Fehrenbach, Ch.; Duflot, M.; Burnage, R.

2001-04-01

Many studies recently have been performed to determine the velocity vector of the Sun, mainly using the latest data on proper motions and parallaxes given by the Hipparcos satellite. We wished to carry out a similar study using totally independent data: the numerous radial velocities (RV) obtained with the Fehrenbach Objective Prisms (PO). This method allows the determination of the RVs of all the stars contained in the same field. These RVs are relative to each other but are linked to the IAU standard system by means of at least two calibration stars of known RV belonging to that field. These data are very homogeneous. We discuss the precision of the results, and deduce that this material is relevant for the computation of the movement of the Sun towards its Apex. We have performed several studies: 1) With 6965 stars of magnitudes ranging from 7 to 10, measured with the small PO of 15 cm diameter (PPO), with the whole sample and with the same sample split into blue and red stars. 2) With 11 978 stars of magnitudes ranging from 7 to 11, by adding to the previous sample the stars measured with the 60 cm diameter PO associated with the Schmidt telescope of Observatoire de Haute Provence (SPO). The results of both studies are consistent. 3) We have estimated the distance D of all stars studied and determined U, V, W and S for four groups of stars selected according to their distances: D<100, ~ 100500 parsecs. We have determined the variation of U, V, W and S with respect to the distance of the stars. The variation of U, V and S is linear up to 500 parsecs. We can consider that W is constant.