Observations During GRIP from HIRAD: Images of C-Band Brightness Temperatures and Ocean Surface Wind Speed and Rain Rate

NASA Technical Reports Server (NTRS)

Miller, Timothy L.; James, M. W.; Jones, W. L.; Ruf, C. S.; Uhlhorn, E. W.; Biswas, S.; May, C.; Shah, G.; Black, P.; Buckley, C. D.

2012-01-01

HIRAD (Hurricane Imaging Radiometer) flew on the WB-57 during NASA s GRIP (Genesis and Rapid Intensification Processes) campaign in August - September of 2010. HIRAD is a new C-band radiometer using a synthetic thinned array radiometer (STAR) technology to obtain cross-track resolution of approximately 3 degrees, out to approximately 60 degrees to each side of nadir. By obtaining measurements of emissions at 4, 5, 6, and 6.6 GHz, observations of ocean surface wind speed and rain rate can be inferred. This technique has been used for many years by precursor instruments, including the Stepped Frequency Microwave Radiometer (SFMR), which has been flying on the NOAA and USAF hurricane reconnaissance aircraft for several years. The advantage of HIRAD over SFMR is that HIRAD can observe a +/- 60-degree swath, rather than a single footprint at nadir angle. Results from the flights during the GRIP campaign will be shown, including images of brightness temperatures, wind speed, and rain rate. To the extent possible, comparisons will be made with observations from other instruments on the GRIP campaign, for which HIRAD observations are either directly comparable or are complementary. Features such as storm eye and eyewall, location of vortex wind and rain maxima, and indications of dynamical features such as the merging of a weaker outer wind/rain maximum with the main vortex may be seen in the data. Potential impacts on operational ocean surface wind analyses and on numerical weather forecasts will also be discussed.

180-GHz Interferometric Imager

NASA Technical Reports Server (NTRS)

Kangaslahti, Pekka P.; Lim, Boon H.; O'Dwyer, Ian J.; Soria, Mary M.; Owen, Heather R.; Gaier, Todd C.; Lambrigtsen, Bjorn, H.; Tanner, Alan B.; Ruf, Christopher

2011-01-01

A 180-GHz interferometric imager uses compact receiver modules, combined high- and low-gain antennas, and ASIC (application specific integrated circuit) correlator technology, enabling continuous, all-weather observations of water vapor with 25-km resolution and 0.3-K noise in 15 minutes of observation for numerical weather forecasting and tropical storm prediction. The GeoSTAR-II prototype instrument is broken down into four major subsystems: the compact, low-noise receivers; sub-array modules; IF signal distribution; and the digitizer/correlator. Instead of the single row of antennas adopted in GeoSTAR, this version has four rows of antennas on a coarser grid. This dramatically improves the sensitivity in the desired field of view. The GeoSTAR-II instrument is a 48-element, synthetic, thinned aperture radiometer operating at 165-183 GHz. The instrument has compact receivers integrated into tiles of 16 elements in a 4x4 arrangement. These tiles become the building block of larger arrays. The tiles contain signal distribution for bias controls, IF signal, and local oscillator signals. The IF signals are digitized and correlated using an ASIC correlator to minimize power consumption. Previous synthetic aperture imagers have used comparatively large multichip modules, whereas this approach uses chip-scale modules mounted on circuit boards, which are in turn mounted on the distribution manifolds. This minimizes the number of connectors and reduces system mass. The use of ASIC technology in the digitizers and correlators leads to a power reduction close to an order of magnitude.

A conceptual design study for a two-dimensional, electronically scanned thinned array radiometer

NASA Technical Reports Server (NTRS)

Mutton, Philip; Chromik, Christopher C.; Dixon, Iain; Statham, Richard B.; Stillwagen, Frederic H.; Vontheumer, Alfred E.; Sasamoto, Washito A.; Garn, Paul A.; Cosgrove, Patrick A.; Ganoe, George G.

1993-01-01

A conceptual design for the Two-Dimensional, Electronically Steered Thinned Array Radiometer (ESTAR) is described. This instrument is a synthetic aperture microwave radiometer that operates in the L-band frequency range for the measurement of soil moisture and ocean salinity. Two auxiliary instruments, an 8-12 micron, scanning infrared radiometer and a 0.4-1.0 micron, charge coupled device (CCD) video camera, are included to provided data for sea surface temperature measurements and spatial registration of targets respectively. The science requirements were defined by Goddard Space Flight Center. Instrument and the spacecraft configurations are described for missions using the Pegasus and Taurus launch vehicles. The analyses and design trades described include: estimations of size, mass and power, instrument viewing coverage, mechanical design trades, structural and thermal analyses, data and communications performance assessments, and cost estimation.

Mars Array Technology Experiment Developed to Test Solar Arrays on Mars

NASA Technical Reports Server (NTRS)

Landis, Geoffrey A.

2001-01-01

Solar arrays will be the power supply for future missions to the planet Mars, including landers, rovers, and eventually human missions to explore the Martian surface. Until Mars Pathfinder landed in July 1997, no solar array had been used on the surface. The MATE package is intended to measure the solar energy reaching the surface, characterize the Martian environment to gather the baseline information required for designing power systems for long-duration missions, and to quantify the performance and degradation of advanced solar cells on the Martian surface. To measure the properties of sunlight reaching the Martian surface, MATE incorporates two radiometers and a visible/NIR spectrometer. The radiometers consist of multiple thermocouple junctions using thin-film technology. These devices generate a voltage proportional to the solar intensity. One radiometer measures the global broadband solar intensity, including both the direct and scattered sunlight, with a field of view of approximately 130. The second radiometer incorporates a slit to measure the direct (unscattered) intensity radiation. The direct radiometer can only be read once per day, with the Sun passing over the slit. The spectrometer measures the global solar spectrum with two 256-element photodiode arrays, one Si sensitive in the visible range (300 to 1100 nm), and a second InGaAs sensitive to the near infrared (900 to 1700 nm). This range covers 86 percent of the total energy from the Sun, with approximately 5-nm resolution. Each photodiode array has its own fiber-optic feed and grating. Although the purpose of the MATE is to gather data useful in designing solar arrays for Mars surface power systems, the radiometer and spectrometer measurements are expected to also provide important scientific data for characterizing the properties of suspended atmospheric dust. In addition to measuring the solar environment of Mars, MATE will measure the performance of five different individual solar cell types and two different solar cell strings, to qualify advanced solar cell types for future Mars missions. The MATE instrument, designed for the Mars-2001 Surveyor Lander mission, contains a capable suite of sensors that will provide both scientific information as well as important engineering data on the operation of solar power systems on Mars. MATE will characterize the intensity and spectrum of the solar radiation on Mars and measure the performance of solar arrays in the Mars environment. MATE flight hardware was built and tested at the NASA Glenn Research Center and is ready for flight.

Optical radiation measurements II; Proceedings of the Meeting, Orlando, FL, Mar. 27, 28, 1989

NASA Astrophysics Data System (ADS)

Palmer, James M.

1989-09-01

The present conference discusses topics in the characterization of imaging radiometers, laboratory instrumentation, field and spacecraft instrumentation, and quantum and thermal standard detectors. Attention is given to UV radiometric imaging, dual-color radiometer imagery, a novel diode-array radiometer, a novel reference spectrophotometer, radiance calibration of spherical integrators, instrumentation for measurement of spectral goniometric reflectance, and a real-time IR background discrimination radiometer. Also discussed are a multichannel radiometer for atmosphere optical property measurements, the UV spectroradiometric output of a turbojet, characterizations of the Earth Radiation Budget Experiment scanning radiometers, total-radiation thermometry, future directions in Si photodiode self-calibration, and radiometric quality Ge photodiodes.

Dual-Polarization, Multi-Frequency Antenna Array for use with Hurricane Imaging Radiometer

NASA Technical Reports Server (NTRS)

Little, John

2013-01-01

Advancements in common aperture antenna technology were employed to utilize its proprietary genetic algorithmbased modeling tools in an effort to develop, build, and test a dual-polarization array for Hurricane Imaging Radiometer (HIRAD) applications. Final program results demonstrate the ability to achieve a lightweight, thin, higher-gain aperture that covers the desired spectral band. NASA employs various passive microwave and millimeter-wave instruments, such as spectral radiometers, for a range of remote sensing applications, from measurements of the Earth's surface and atmosphere, to cosmic background emission. These instruments such as the HIRAD, SFMR (Stepped Frequency Microwave Radiometer), and LRR (Lightweight Rainfall Radiometer), provide unique data accumulation capabilities for observing sea surface wind, temperature, and rainfall, and significantly enhance the understanding and predictability of hurricane intensity. These microwave instruments require extremely efficient wideband or multiband antennas in order to conserve space on the airborne platform. In addition, the thickness and weight of the antenna arrays is of paramount importance in reducing platform drag, permitting greater time on station. Current sensors are often heavy, single- polarization, or limited in frequency coverage. The ideal wideband antenna will have reduced size, weight, and profile (a conformal construct) without sacrificing optimum performance. The technology applied to this new HIRAD array will allow NASA, NOAA, and other users to gather information related to hurricanes and other tropical storms more cost effectively without sacrificing sensor performance or the aircraft time on station. The results of the initial analysis and numerical design indicated strong potential for an antenna array that would satisfy all of the design requirements for a replacement HIRAD array. Multiple common aperture antenna methodologies were employed to achieve exceptional gain over the entire spectral frequency band while exhibiting superb VSWR (voltage standing wave ratio) values. Element size and spacing requirements were addressed for a direct replacement of the thicker, lower-performance, stack ed patch antenna array currently employed for the HIRAD application. Several variants to the multiband arrays were developed that exhibited four, equally spaced, high efficiency, "sweet spot" frequency bands, as well as the option for a high-performance wideband array. The 0.25-in. (˜6.4- mm) thickness of the antenna stack-up itself was achieved through the application of specialized antenna techniques and meta-materials to accomplish all design objectives.

Observations of C-Band Brightness Temperatures and Ocean Surface Wind Speed and Rain Rate from the Hurricane Imaging Radiometer (HIRAD) during GRIP and HS3

NASA Technical Reports Server (NTRS)

Miller, Timothy L.; James, M. W.; Roberts, J. B.; Jones, W. L.; Biswas, S.; Ruf, C. S.; Uhlhorn, E. W.; Atlas, R.; Black, P.; Albers, C.

2013-01-01

HIRAD flew on high-altitude aircraft over Earl and Karl during NASA s GRIP (Genesis and Rapid Intensification Processes) campaign in August - September of 2010, and at the time of this writing plans to fly over Atlantic tropical cyclones in September of 2012 as part of the Hurricane and Severe Storm Sentinel (HS3) mission. HIRAD is a new C-band radiometer using a synthetic thinned array radiometer (STAR) technology to obtain cross-track resolution of approximately 3 degrees, out to approximately 60 degrees to each side of nadir. By obtaining measurements of emissions at 4, 5, 6, and 6.6 GHz, observations of ocean surface wind speed and rain rate can be retrieved. This technique has been used for many years by precursor instruments, including the Stepped Frequency Microwave Radiometer (SFMR), which has been flying on the NOAA and USAF hurricane reconnaissance aircraft for several years to obtain observations within a single footprint at nadir angle. Results from the flights during the GRIP and HS3 campaigns will be shown, including images of brightness temperatures, wind speed, and rain rate. Comparisons will be made with observations from other instruments on the campaigns, for which HIRAD observations are either directly comparable or are complementary. Features such as storm eye and eye-wall, location of storm wind and rain maxima, and indications of dynamical features such as the merging of a weaker outer wind/rain maximum with the main vortex may be seen in the data. Potential impacts on operational ocean surface wind analyses and on numerical weather forecasts will also be discussed.

Sampling and position effects in the Electronically Steered Thinned Array Radiometer (ESTAR)

NASA Technical Reports Server (NTRS)

Katzberg, Stephen J.

1993-01-01

A simple engineering level model of the Electronically Steered Thinned Array Radiometer (ESTAR) is developed that allows an identification of the major effects of the sampling process involved with this technique. It is shown that the ESTAR approach is sensitive to aliasing and has a highly non-uniform sensitivity profile. It is further shown that the ESTAR approach is strongly sensitive to position displacements of the low-density sampling antenna elements.

Controller for the Electronically Scanned Thinned Array Radiometer (ESTAR) instrument

NASA Technical Reports Server (NTRS)

Zomberg, Brian G.; Chren, William A., Jr.

1994-01-01

A prototype controller for the ESTAR (electronically scanned thinned array radiometer) instrument has been designed and tested. It manages the operation of the digital data subsystem (DDS) and its communication with the Small Explorer data system (SEDS). Among the data processing tasks that it coordinates are FEM data acquisition, noise removal, phase alignment and correlation. Its control functions include instrument calibration and testing of two critical subsystems, the output data formatter and Walsh function generator. It is implemented in a Xilinx XC3064PC84-100 field programmable gate array (FPGA) and has a maximum clocking frequency of 10 MHz.

Phased array feed design technology for Large Aperture Microwave Radiometer (LAMR) Earth observations

NASA Technical Reports Server (NTRS)

Schuman, H. K.

1992-01-01

An assessment of the potential and limitations of phased array antennas in space-based geophysical precision radiometry is described. Mathematical models exhibiting the dependence of system and scene temperatures and system sensitivity on phased array antenna parameters and components such as phase shifters and low noise amplifiers (LNA) are developed. Emphasis is given to minimum noise temperature designs wherein the LNA's are located at the array level, one per element or subarray. Two types of combiners are considered: array lenses (space feeds) and corporate networks. The result of a survey of suitable components and devices is described. The data obtained from that survey are used in conjunction with the mathematical models to yield an assessment of effective array antenna noise temperature for representative geostationary and low Earth orbit systems. Practical methods of calibrating a space-based, phased array radiometer are briefly addressed as well.

Low-cost solar array project: Four absolute cavity radiometer (pyrheliometer) intercomparisons at New River, Arizona: Radiometer standards

NASA Technical Reports Server (NTRS)

Estey, R. S.; Seaman, C. H.

1981-01-01

Four detailed intercomparisons were made for a number of models of cavity-type self-calibrating radiometers (pyrheliometers). Each intercomparison consisted of simultaneous readings of pyrheliometers at 30-second intervals in runs of 10 minutes, with at least 15 runs per intercomparison. Twenty-seven instruments were in at least one intercomparison, and five were in all four. Summarized results and all raw data are provided from the intercomparisons.

Two-Dimensional Synthetic Aperture Radiometry over Land Surface During Soil Moisture Experiment in 2003 (SMEX03)

NASA Technical Reports Server (NTRS)

Ryu, Dongryeol; Jackson, Thomas J.; Bindlish, Rajat; Le Vine, David M.; Haken, Michael

2007-01-01

Microwave radiometry at low frequencies (L-band, approx. 1.4 GHz) has been known as an optimal solution for remote sensing of soil moisture. However, the antenna size required to achieve an appropriate resolution from space has limited the development of spaceborne L-band radiometers. This problem can be addressed by interferometric technology called aperture synthesis. The Soil Moisture and Ocean Salinity (SMOS) mission will apply this technique to monitor global-scale surface parameters in the near future. The first airborne experiment using an aircraft prototype of this approach, the Two-Dimensional Synthetic Aperture Radiometer (2D-STAR), was performed in the Soil Moisture Experiment in 2003 (SMEX03). The L-band brightness temperature data acquired in Alabama by the 2DSTAR was compared with ground-based measurements of soil moisture and with C-band data collected by the Polarimetric Scanning Radiometer (PSR). Our results demonstrate a good response of the 2D-STAR brightness temperature to changes in surface wetness, both in agricultural and forest lands. The behavior of the horizontally polarized brightness temperature data with increasing view-angle over the forest area was noticeably different than over bare soil. The results from the comparison of 2D-STAR and PSR indicate a better response of the 2D-STAR to the surface wetness under both wet and dry conditions. Our results have important implications for the performance of the future SMOS mission.

Microwave Radiometers from 0.6 to 22 GHz for Juno, a Polar Orbiter around Jupiter

NASA Technical Reports Server (NTRS)

P. Pingree; Janssen, M.; Oswald, J.; Brown, S.; Chen, J.; Hurst, K.; Kitiyakara, A.; Maiwald, F.; Smith, S.

2008-01-01

A compact radiometer instrument is under development at JPL for Juno, the next NASA New Frontiers mission, scheduled to launch in 2011. This instrument is called the MWR (MicroWave Radiometer), and its purpose is to measure the thermal emission from Jupiter's atmosphere at selected frequencies from 0.6 to 22 GHz. The objective is to measure the distributions and abundances of water and ammonia in Jupiter's atmosphere, with the goal of understanding the previously unobserved dynamics of the subcloud atmosphere, and to discriminate among models for planetary formation in our solar system. The MWR instrument is currently being developed to address these science questions for the Juno mission. As part of a deep space mission aboard a solar-powered spacecraft, MWR is designed to be compact, lightweight, and low power. The entire MWR instrument consists of six individual radiometer channels with approximately 4% bandwidth at 0.6, 1.25,2.6,5.2, 10,22 GHz operating in direct detection mode. Each radiometer channel has up to 80 dB of gain with a noise figure of several dB. The highest frequency channel uses a corrugated feedhorn and waveguide transmission lines, whereas all other channels use highly phase stable coaxial cables and either patch array or waveguide slot array antennas. Slot waveguide array antennas were chosen for the low loss at the next three highest frequencies and patch array antennas were implemented due to the mass constraint at the two lowest frequencies. The six radiometer channels receive their voltage supplies and control lines from an electronics unit that also provides the instrument communication interface to the Juno spacecraft. For calibration purposes each receiver has integrated noise diodes, a Dicke switch, and temperature sensors near each component that contributes to the noise figure. In addition, multiple sensors will be placed along the RF transmission lines and the antennas in order to measure temperature gradients. All antennas and RF transmission lines must withstand low temperatures and the harsh radiation environment surrounding Jupiter; the receivers and control electronics are protected by a radiation-shielding enclosure on the Juno spacecraft that also provides for a benign and stable operating temperature environment. This paper will focus on the concept of the MWR instrument and will present results of one breadboard receiver channel.

ESTAR: The Electronically Scanned Thinned Array Radiometer for remote sensing measurement of soil moisture and ocean salinity

NASA Technical Reports Server (NTRS)

Swift, C. T.

1993-01-01

The product of a working group assembled to help define the science objectives and measurement requirements of a spaceborne L-band microwave radiometer devoted to remote sensing of surface soil moisture and sea surface salinity is presented. Remote sensing in this long-wavelength portion of the microwave spectrum requires large antennas in low-Earth orbit to achieve acceptable spatial resolution. The proposed radiometer, ESTAR, is unique in that it employs aperture synthesis to reduce the antenna area requirements for a space system.

Wideband Agile Digital Microwave Radiometer

NASA Technical Reports Server (NTRS)

Gaier, Todd C.; Brown, Shannon T.; Ruf, Christopher; Gross, Steven

2012-01-01

The objectives of this work were to take the initial steps needed to develop a field programmable gate array (FPGA)- based wideband digital radiometer backend (>500 MHz bandwidth) that will enable passive microwave observations with minimal performance degradation in a radiofrequency-interference (RFI)-rich environment. As manmade RF emissions increase over time and fill more of the microwave spectrum, microwave radiometer science applications will be increasingly impacted in a negative way, and the current generation of spaceborne microwave radiometers that use broadband analog back ends will become severely compromised or unusable over an increasing fraction of time on orbit. There is a need to develop a digital radiometer back end that, for each observation period, uses digital signal processing (DSP) algorithms to identify the maximum amount of RFI-free spectrum across the radiometer band to preserve bandwidth to minimize radiometer noise (which is inversely related to the bandwidth). Ultimately, the objective is to incorporate all processing necessary in the back end to take contaminated input spectra and produce a single output value free of manmade signals to minimize data rates for spaceborne radiometer missions. But, to meet these objectives, several intermediate processing algorithms had to be developed, and their performance characterized relative to typical brightness temperature accuracy re quirements for current and future microwave radiometer missions, including those for measuring salinity, soil moisture, and snow pack.

Impact of Separation Distance on Multi-Vane Radiometer Configurations

NASA Astrophysics Data System (ADS)

Cornella, B. M.; Ketsdever, A. D.; Gimelshein, N. E.; Gimelshein, S. F.

2011-05-01

The radiometric force produced by a linear array of three radiometer vanes has been assessed numerically using an argon carrier gas and experimentally using air. The separation distance between the three vanes of the array was varied between 0 and 120 percent based on the height of an individual radiometer vane of 40 mm. Qualitative agreement between the numerical and experimental results is shown as a function of operating Knudsen number, vane separation distance, and surrounding chamber geometry. Both sets of results indicate an asymptotic trend in maximum force as the separation distance increases as well as a shift in the maximum force Knudsen number. Small chamber effects for both numerical and experimental results indicate an increase of the total force ranging from a factor of 2.5 to 4. Quantitatively, however, the numerical simulations yield forces approximately an order of magnitude higher than observed in the experiments due to differences in carrier gas and accommodation coefficient as well as the two dimensional nature of the numerical simulations versus the three dimensional experiment.

Broad-band UHF dipole array

NASA Technical Reports Server (NTRS)

Bailey, M. C.

1985-01-01

A 6X6 array of fan-dipoles was designed to operate in the 510 to 660 MHz frequency range for aircraft flight test and evaluation of a UHF radiometer system. A broad-band dipole design operating near the first resonance is detailed. Measured VSWR and radiation patterns for the dipole array demonstrate achievable bandwidths in the 35 percent to 40 percent range.

A Review of Communications Satellites and Related Spacecraft for Factors Influencing Mission Success. Volume 2

DTIC Science & Technology

1975-11-17

and control (subsystem) COMM., comm AEC Atomic Energy Commission comsat AFB Air Force Base COMSTAR ACE A-hr aerospace ground equipment ampere...array TDA Satellite Assembly Building TDAL Space and Missile Systems Organization (U.S. Air Force) TDM THIR satellite communications system TI...Satellite Control Facility (U.S. Air Force) TIROS selective chopper radiometer TLM, T/M surface composition mapping radiometer TOS TRUST

Transfer-matrices for series-type microwave antenna circuits. [L-band radiometer

NASA Technical Reports Server (NTRS)

Schmidt, R. F.

1981-01-01

Transfer matrices are developed which permit analysis and computer evaluation of certain series type microwave antenna circuits associated with an L-Band microwave radiometer (LBMR) under investigation at Goddard Space Flight Center. This radiometer is one of several diverse instrument designs to be used for the determination of soil moisture, sea state, salinity, and temperature data. Four port matrix notation is used throughout for the evaluation of LBMR circuits with mismatched couplers and lossy transmission lines. Matrix parameters in examples are predicted on an impedance analysis and an assumption of an array aperture distribution. The notation presented is easily adapted to longer and more varied chains of matrices, and to matrices of larger dimension.

Design and characterization of the Large-aperture Experiment to Detect the Dark Age (LEDA) radiometer systems

NASA Astrophysics Data System (ADS)

Price, D. C.; Greenhill, L. J.; Fialkov, A.; Bernardi, G.; Garsden, H.; Barsdell, B. R.; Kocz, J.; Anderson, M. M.; Bourke, S. A.; Craig, J.; Dexter, M. R.; Dowell, J.; Eastwood, M. W.; Eftekhari, T.; Ellingson, S. W.; Hallinan, G.; Hartman, J. M.; Kimberk, R.; Lazio, T. Joseph W.; Leiker, S.; MacMahon, D.; Monroe, R.; Schinzel, F.; Taylor, G. B.; Tong, E.; Werthimer, D.; Woody, D. P.

2018-05-01

The Large-Aperture Experiment to Detect the Dark Age (LEDA) was designed to detect the predicted O(100) mK sky-averaged absorption of the Cosmic Microwave Background by Hydrogen in the neutral pre- and intergalactic medium just after the cosmological Dark Age. The spectral signature would be associated with emergence of a diffuse Lyα background from starlight during `Cosmic Dawn'. Recently, Bowman et al. (2018) have reported detection of this predicted absorption feature, with an unexpectedly large amplitude of 530 mK, centered at 78 MHz. Verification of this result by an independent experiment, such as LEDA, is pressing. In this paper, we detail design and characterization of the LEDA radiometer systems, and a first-generation pipeline that instantiates a signal path model. Sited at the Owens Valley Radio Observatory Long Wavelength Array, LEDA systems include the station correlator, five well-separated redundant dual polarization radiometers and backend electronics. The radiometers deliver a 30-85 MHz band (16 < z < 34) and operate as part of the larger interferometric array, for purposes ultimately of in situ calibration. Here, we report on the LEDA system design, calibration approach, and progress in characterization as of January 2016. The LEDA systems are currently being modified to improve performance near 78 MHz in order to verify the purported absorption feature.

Fly's Eye GLM Simulator Preliminary Validation Analysis

NASA Astrophysics Data System (ADS)

Quick, M. G.; Christian, H. J., Jr.; Blakeslee, R. J.; Stewart, M. F.; Corredor, D.; Podgorny, S.

2017-12-01

As part of the validation effort for the Geostationary Lightning Mapper (GLM) an airborne radiometer array has been fabricated to observe lightning optical emission through the cloud top. The Fly's Eye GLM Simulator (FEGS) is a multi-spectral, photo-electric radiometer array with a nominal spatial resolution of 2 x 2 km and spatial footprint of 10 x 10 km at cloud top. A main 25 pixel array observes the 777.4 nm oxygen emission triplet using an optical passband filter with a 10 nm FWHM, a sampling rate of 100 kHz, and 16 bit resolution. From March to May of 2017 FEGS was flown on the NASA ER-2 high altitude aircraft during the GOES-R Validation Flight Campaign. Optical signatures of lightning were observed during a variety of thunderstorm scenarios while coincident measurements were obtained by GLM and ground based antennae networks. This presentation will describe the preliminary analysis of the FEGS dataset in the context of GLM validation.

Hurricane Imaging Radiometer

NASA Technical Reports Server (NTRS)

Cecil, Daniel J.; James, Mark W.; Roberts, J. Brent; Bisawas, Sayak K.; Jones, W. Linwood; Johnson, James; Farrar, Spencer; Sahawneh, Saleem; Ruf, Christopher S.; Morris, Mary;

MCM Polarimetric Radiometers for Planar Arrays

NASA Technical Reports Server (NTRS)

Kangaslahti, Pekka; Dawson, Douglas; Gaier, Todd

2007-01-01

A polarimetric radiometer that operates at a frequency of 40 GHz has been designed and built as a prototype of multiple identical units that could be arranged in a planar array for scientific measurements. Such an array is planned for use in studying the cosmic microwave background (CMB). All of the subsystems and components of this polarimetric radiometer are integrated into a single multi-chip module (MCM) of substantially planar geometry. In comparison with traditional designs of polarimetric radiometers, the MCM design is expected to greatly reduce the cost per unit in an array of many such units. The design of the unit is dictated partly by a requirement, in the planned CMB application, to measure the Stokes parameters I, Q, and U of the CMB radiation with high sensitivity. (A complete definition of the Stokes parameters would exceed the scope of this article. In necessarily oversimplified terms, I is a measure of total intensity of radiation, while Q and U are measures of the relationships between the horizontally and vertically polarized components of radiation.) Because the sensitivity of a single polarimeter cannot be increased significantly, the only way to satisfy the high-sensitivity requirement is to make a large array of polarimeters that operate in parallel. The MCM includes contact pins that can be plugged into receptacles on a standard printed-circuit board (PCB). All of the required microwave functionality is implemented within the MCM; any required supporting non-microwave ("back-end") electronic functionality, including the provision of DC bias and control signals, can be implemented by standard PCB techniques. On the way from a microwave antenna to the MCM, the incoming microwave signal passes through an orthomode transducer (OMT), which splits the radiation into an h + i(nu) beam and an h - i(nu) beam (where, using complex-number notation, h denotes the horizontal component, nu denotes the vertical component, and +/-i denotes a +/-90deg phase shift). Each of these beams enters the MCM through one of two WR-22 waveguide input terminals in the lid of the MCM. The h + i(nu0 and h - i(nu) signals are amplified, then fed to a phase-discriminator hybrid designed specifically to fit the predominantly planar character of the MCM geometry and to enable determination of Q and U. The phase-discriminator hybrid generates four outputs, which are detected and used to calculate I, Q, and U.

ultra-Stable Spectrometer for Sky-Scanning, Sun-Tracking Atmospheric Research (5STAR)

NASA Astrophysics Data System (ADS)

Dunagan, S. E.; Johnson, R. R.; Redemann, J.; Holben, B. N.; Schmid, B.; Flynn, C. J.; Fahey, L.; LeBlanc, S. E.; Liss, J.; Kacenelenbogen, M. S.; Segal-Rosenhaimer, M.; Shinozuka, Y.; Dahlgren, R. P.; Pistone, K.; Karol, Y.

2017-12-01

The Spectrometer for Sky-Scanning, Sun-Tracking Atmospheric Research (4STAR) combines airborne sun tracking and sky scanning with diffraction spectroscopy to improve knowledge of atmospheric constituents and their links to air pollution and climate. Direct beam hyperspectral measurement of optical depth improves retrievals of gas constituents and determination of aerosol properties. Sky scanning enhances retrievals of aerosol type and size distribution. Hyperspectral cloud-transmitted radiance measurements enable the retrieval of cloud properties from below clouds. These measurements tighten the closure between satellite and ground-based measurements. 4STAR incorporates a modular sun-tracking/ sky-scanning optical head with optical fiber signal transmission to rack mounted spectrometers, permitting miniaturization of the external optical tracking head, and future detector evolution. 4STAR has supported a broad range of flight experiments since it was first flown in 2010. This experience provides the basis for a series of improvements directed toward reducing measurement uncertainty and calibration complexity, and expanding future measurement capabilities, to be incorporated into a new 5STAR instrument. A 9-channel photodiode radiometer with AERONET-matched bandpass filters will be incorporated to improve calibration stability. A wide dynamic range tracking camera will provide a high precision solar position tracking signal as well as an image of sky conditions around the solar axis. An ultrasonic window cleaning system design will be tested. A UV spectrometer tailored for formaldehyde and SO2 gas retrievals will be added to the spectrometer enclosure. Finally, expansion capability for a 4 channel polarized radiometer to measure the Stokes polarization vector of sky light will be incorporated. This paper presents initial progress on this next-generation 5STAR instrument. Keywords: atmosphere; climate; pollution; radiometry; technology; hyperspectral; fiber optic, polarimetry

RFI Risk Reduction Activities Using New Goddard Digital Radiometry Capabilities

NASA Technical Reports Server (NTRS)

Bradley, Damon; Kim, Ed; Young, Peter; Miles, Lynn; Wong, Mark; Morris, Joel

2012-01-01

The Goddard Radio-Frequency Explorer (GREX) is the latest fast-sampling radiometer digital back-end processor that will be used for radiometry and radio-frequency interference (RFI) surveying at Goddard Space Flight Center. The system is compact and deployable, with a mass of about 40 kilograms. It is intended to be flown on aircraft. GREX is compatible with almost any aircraft, including P-3, twin otter, C-23, C-130, G3, and G5 types. At a minimum, the system can function as a clone of the Soil Moisture Active Passive (SMAP) ground-based development unit [1], or can be a completely independent system that is interfaced to any radiometer, provided that frequency shifting to GREX's intermediate frequency is performed prior to sampling. If the radiometer RF is less than 200MHz, then the band can be sampled and acquired directly by the system. A key feature of GREX is its ability to simultaneously sample two polarization channels simultaneously at up to 400MSPS, 14-bit resolution each. The sampled signals can be recorded continuously to a 23 TB solid-state RAID storage array. Data captures can be analyzed offline using the supercomputing facilities at Goddard Space Flight Center. In addition, various Field Programmable Gate Array (FPGA) - amenable radiometer signal processing and RFI detection algorithms can be implemented directly on the GREX system because it includes a high-capacity Xilinx Virtex-5 FPGA prototyping system that is user customizable.

Space shuttle cavity assessment test program

NASA Technical Reports Server (NTRS)

Scheps, P. B.

1976-01-01

In order to obtain basic radiation properties of the radiator/payload bay door cavity, three tests were conducted on a full-size structural simulator of the cavity. There were three tests conducted: (1) CATA used for determination of exchange factors, absorbed solar flux, and door covering influences, (2) quartz lamp array calibrated to provide IR flux distribution on CATA, and (3) retest with radiometer array for background flux measurement.

Mechanical Development of a Very Non-Standard Patch Array Antenna for Extreme Environments

NASA Technical Reports Server (NTRS)

Hughes, Richard; Chamberlain, Neil; Jakoboski, Julie; Petkov, Mihail

2012-01-01

This paper describes the mechanical development of patch antenna arrays for the Juno mission. The patch arrays are part of a six-frequency microwave radiometer instrument that will be used to measure thermal emissions from Jupiter. The very harsh environmental conditions in Jupiter orbit, as well as a demanding launch environment, resulted in a design that departs radically from conventional printed circuit patch antennas. The paper discusses the development and qualification of the Juno patch array antennas, with emphasis on the materials approach that was devised to mitigate the effects of electron charging in Jupiter orbit.

Fabrication of hexagonal star-shaped and ring-shaped patterns arrays by Mie resonance sphere-lens-lithography

NASA Astrophysics Data System (ADS)

Liu, Xianchao; Wang, Jun; Li, Ling; Gou, Jun; Zheng, Jie; Huang, Zehua; Pan, Rui

2018-05-01

Mie resonance sphere-lens-lithography has proved to be a good candidate for fabrication of large-area tunable surface nanopattern arrays. Different patterns on photoresist surface are obtained theoretically by adjusting optical coupling among neighboring spheres with different gap sizes. The effect of light reflection from the substrate on the pattern produced on the photoresist with a thin thickness is also discussed. Sub-micron hexagonal star-shaped and ring-shaped patterns arrays are achieved with close-packed spheres arrays and spheres arrays with big gaps, respectively. Changing of star-shaped vertices is induced by different polarization of illumination. Experimental results agree well with the simulation. By using smaller resonance spheres, sub-400 nm star-shaped and ring-shaped patterns can be realized. These tunable patterns are different from results of previous reports and have enriched pattern morphology fabricated by sphere-lens-lithography, which can find application in biosensor and optic devices.

BOREAS HYD-3 Subcanopy Incoming Solar Radiation Measurements

NASA Technical Reports Server (NTRS)

Hardy, Janet P.; Hall, Forrest G. (Editor); Knapp, David E. (Editor); Davis, Robert E.; Smith, David E. (Technical Monitor)

2000-01-01

The Boreal Ecosystem-Atmosphere Study (BOREAS) Hydrology (HYD)-3 team collected several data sets related to the hydrology of forested areas. This data set contains solar radiation measurements from several pyranometers (solar radiometers) placed on the snow surface in jack pine (1994) and black spruce and aspen forests (1996) in the BOREAS southern study area (SSA). An array of radiometers was used to collect data for three to four consecutive days in each forest type to study the hypothesis that energy transfer and snow water equivalent would vary spatially as a function of canopy closure. The quality of the data is good, because the days were generally clear and the radiometers were checked daily to remove anything that landed on the radiometers. The data are available in tabular ASCII files. The subcanopy incoming solar radiation measurement data are available from the Earth Observing System Data and Information System (EOSDIS) Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC). The data files are available on a CD-ROM (see document number 20010000884).

The Parkes front-end controller and noise-adding radiometer

NASA Technical Reports Server (NTRS)

Brunzie, T. J.

1990-01-01

A new front-end controller (FEC) was installed on the 64-m antenna in Parkes, Australia, to support the 1989 Voyager 2 Neptune encounter. The FEC was added to automate operation of the front-end microwave hardware as part of the Deep Space Network's Parkes-Canberra Telemetry Array. Much of the front-end hardware was refurbished and reimplemented from a front-end system installed in 1985 by the European Space Agency for the Uranus encounter; however, the FEC and its associated noise-adding radiometer (NAR) were new Jet Propulsion Laboratory (JPL) designs. Project requirements and other factors led to the development of capabilities not found in standard Deep Space Network (DSN) controllers and radiometers. The Parkes FEC/NAR performed satisfactorily throughout the Neptune encounter and was removed in October 1989.

Method and apparatus for millimeter-wave detection of thermal waves for materials evaluation

DOEpatents

Gopalsami, Nachappa; Raptis, Apostolos C.

1991-01-01

A method and apparatus for generating thermal waves in a sample and for measuring thermal inhomogeneities at subsurface levels using millimeter-wave radiometry. An intensity modulated heating source is oriented toward a narrow spot on the surface of a material sample and thermal radiation in a narrow volume of material around the spot is monitored using a millimeter-wave radiometer; the radiometer scans the sample point-by-point and a computer stores and displays in-phase and quadrature phase components of thermal radiations for each point on the scan. Alternatively, an intensity modulated heating source is oriented toward a relatively large surface area in a material sample and variations in thermal radiation within the full field of an antenna array are obtained using an aperture synthesis radiometer technique.

Aquarius Digital Processing Unit

NASA Technical Reports Server (NTRS)

Forgione, Joshua; Winkert, George; Dobson, Norman

2009-01-01

Three documents provide information on a digital processing unit (DPU) for the planned Aquarius mission, in which a radiometer aboard a spacecraft orbiting Earth is to measure radiometric temperatures from which data on sea-surface salinity are to be deduced. The DPU is the interface between the radiometer and an instrument-command-and-data system aboard the spacecraft. The DPU cycles the radiometer through a programmable sequence of states, collects and processes all radiometric data, and collects all housekeeping data pertaining to operation of the radiometer. The documents summarize the DPU design, with emphasis on innovative aspects that include mainly the following: a) In the radiometer and the DPU, conversion from analog voltages to digital data is effected by means of asynchronous voltage-to-frequency converters in combination with a frequency-measurement scheme implemented in field-programmable gate arrays (FPGAs). b) A scheme to compensate for aging and changes in the temperature of the DPU in order to provide an overall temperature-measurement accuracy within 0.01 K includes a high-precision, inexpensive DC temperature measurement scheme and a drift-compensation scheme that was used on the Cassini radar system. c) An interface among multiple FPGAs in the DPU guarantees setup and hold times.

The 11th Aerospace Mechanisms Symposium

NASA Technical Reports Server (NTRS)

1977-01-01

Various mechanisms in aerospace engineering were presented at this conference. Specifications, design, and use of spacecraft and missile components are discussed, such as tail assemblies, radiometers, magnetormeters, pins, reaction wheels, ball bearings, actuators, mirrors, nutation dampers, airfoils, solar arrays, etc.

Optical Component Performance for the Ocean Radiometer for Carbon Assessment (ORCA)

NASA Technical Reports Server (NTRS)

Quijada, Manuel A.; Wilson, Mark; Waluschka, Eugene; McClain, Charles R.

2011-01-01

The Ocean Radiometer for Carbon Assessment (ORCA) is a new design for the next generation remote sensing of ocean biology and biogeochemistry. ORCA is configured to meet all the measurement requirements of the Decadal Survey Aerosol, Cloud, and Ecology (ACE), the Ocean Ecosystem (OES) radiometer and the Pro-ACE climate data continuity mission (PACE). Under the auspices of a 2007 grant from NASA Research Opportunity in Space and Earth Science (ROSES) and the Instrument Incubator Program (IIP), a team at the Goddard Space Flight Center (GSFC) has been working on a functional prototype with flight-like fore and aft optics and scan mechanisms. As part of the development efforts to bring ORCA closer to a flight configuration and in order to reduce cost, we have conducted component-level optical testing using standard spectrophotometers and system-level characterizations using non-flight commercial off-the-shelf (COTS) focal plane array detectors. Although these arrays would not be able to handle flight data rates, they are adequate for optical alignment and performance testing. The purpose of this presentation is to describe the results of this testing performed at GSFC and the National Institute of Standards and Technology (NIST) at the component and system level. Specifically, we show results for ORCA's spectral calibration ranging from the near UV, visible, and near-infrared spectral region.

Uncertainty Evaluation of Measurements with Pyranometers and Pyrheliometers

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

Konings, Jorgen; Habte, Aron

2016-01-03

Evaluating photovoltaic (PV) cells, modules, arrays and systems performance of solar energy relies on accurate measurement of the available solar radiation resources. Solar radiation resources are measured using radiometers such as pyranometers (global horizontal irradiance) and pyrheliometers (direct normal irradiance). The accuracy of solar radiation data measured by radiometers depends not only on the specification of the instrument but also on a) the calibration procedure, b) the measurement conditions and maintenance, and c) the environmental conditions. Therefore, statements about the overall measurement uncertainty can only be made on an individual basis, taking all relevant factors into account. This paper providesmore » guidelines and recommended procedures for estimating the uncertainty in measurements by radiometers using the Guide to the Expression of Uncertainty (GUM) Method. Special attention is paid to the concept of data availability and its link to uncertainty evaluation.« less

Radiometric correction of atmospheric path length fluctuations in interferometric experiments. [in radio astronomy

NASA Technical Reports Server (NTRS)

Resch, G. M.; Hogg, D. E.; Napier, P. J.

1984-01-01

To support very long baseline interferometric experiments, a system has been developed for estimating atmospheric water vapor path delay. The system consists of dual microwave radiometers, one operating at 20.7 GHz and the other at 31.4 GHz. The measured atmospheric brightness temperatures at these two frequencies yield the estimate of the precipitable water present in both vapor and droplets. To determine the accuracy of the system, a series of observations were undertaken, comparing the outputs of two water vapor radiometers with the phase variation observed with two connected elements of the very large array (VLA). The results show that: (1) water vapor fluctuations dominate the residual VLA phase and (2) the microwave radiometers can measure and correct these effects. The rms phase error after correction is typically 15 deg at a wavelength of 6 cm, corresponding to an uncertainty in the path delay of 0.25 cm. The residual uncertainty is consistent with the stability of the microwave radiometer but is still considerably larger than the stability of the VLA. The technique is less successful under conditions of heavy cloud.

Hurricane Imaging Radiometer

NASA Technical Reports Server (NTRS)

Cecil, Daniel J.; Biswas, Sayak K.; James, Mark W.; Roberts, J. Brent; Jones, W. Linwood; Johnson, James; Farrar, Spencer; Sahawneh, Saleem; Ruf, Christopher S.; Morris, Mary;

Atmospheric boundary layer evening transitions over West Texas

USDA-ARS?s Scientific Manuscript database

A systemic analysis of the atmospheric boundary layer behavior during some evening transitions over West Texas was done using the data from an extensive array of instruments which included small and large aperture scintillometers, net radiometers, and meteorological stations. The analysis also comp...

Microwave Radiometer Technology Acceleration Mission (MiRaTA): Advancing Weather Remote Sensing with Nanosatellites

NASA Astrophysics Data System (ADS)

Cahoy, K.; Blackwell, W. J.; Bishop, R. L.; Erickson, N.; Fish, C. S.; Neilsen, T. L.; Stromberg, E. M.; Bardeen, J.; Dave, P.; Marinan, A.; Marlow, W.; Kingsbury, R.; Kennedy, A.; Byrne, J. M.; Peters, E.; Allen, G.; Burianek, D.; Busse, F.; Elliott, D.; Galbraith, C.; Leslie, V. V.; Osaretin, I.; Shields, M.; Thompson, E.; Toher, D.; DiLiberto, M.

2014-12-01

The Microwave Radiometer Technology Acceleration (MiRaTA) is a 3U CubeSat mission sponsored by the NASA Earth Science Technology Office (ESTO). Microwave radiometer measurements and GPS radio occultation (GPSRO) measurements of all-weather temperature and humidity provide key contributions toward improved weather forecasting. The MiRaTA mission will validate new technologies in both passive microwave radiometry and GPS radio occultation: (1) new ultra-compact and low-power technology for multi-channel and multi-band passive microwave radiometers, and (2) new GPS receiver and patch antenna array technology for GPS radio occultation retrieval of both temperature-pressure profiles in the atmosphere and electron density profiles in the ionosphere. In addition, MiRaTA will test (3) a new approach to spaceborne microwave radiometer calibration using adjacent GPSRO measurements. The radiometer measurement quality can be substantially improved relative to present systems through the use of proximal GPSRO measurements as a calibration standard for radiometric observations, reducing and perhaps eliminating the need for costly and complex internal calibration targets. MiRaTA will execute occasional pitch-up maneuvers so that the radiometer and GPSRO observations sound overlapping volumes of atmosphere through the Earth's limb. To validate system performance, observations from both microwave radiometer (MWR) and GPSRO instruments will be compared to radiosondes, global high-resolution analysis fields, other satellite observations, and to each other using radiative transfer models. Both the radiometer and GPSRO payloads, currently at TRL5 but to be advanced to TRL7 at mission conclusion, can be accommodated in a single 3U CubeSat. The current plan is to launch from an International Space Station (ISS) orbit at ~400 km altitude and 52° inclination for low-cost validation over a ~90-day mission to fly in 2016. MiRaTA will demonstrate high fidelity, well-calibrated radiometric sensing from a nanosatellite platform, thereby enabling new architectural approaches for mission implementation at lower cost and risk with more flexible access to space.

Spectral transmissometer and radiometer - Design and initial results. [of free drifting experiment in Pacific Ocean

NASA Technical Reports Server (NTRS)

Carder, Kendall L.; Steward, Robert G.; Peacock, Thomas G.; Payne, Paul R.; Peck, Wayne

1988-01-01

A new solid-state spectral transmissometer and radiometer is described. The radiometer measures upwelling radiance, downwelling irradiance, and beam transmittance from 390 to 750 nm with channel widths of 2.35 nm. The spectrometer consists of a 256 element CCD linear array collecting light dispersed by a reflection grating in a modified Littrow configuration. The spectrometer is time and space-shared among the three signal types. The instrument has been deployed as a free-drifting buoy and in the profiling mode, with data stored internally on a magnetic bubble memory or sent up a conducting cable as desired. Power can be supplied either by a detachable external battery pack or through conducting cable. The instrument has been deployed in the oligotrophic North Pacific Central Gyre and in the eutrophic Straits of Juan de Fuca, and preliminary results for each region are discussed.

Potential of Future Hurricane Imaging Radiometer (HIRAD) Ocean Surface Wind Observations for Determining Tropical Storm Vortex Intensity and Structure

NASA Technical Reports Server (NTRS)

Atlas, Robert; Bailey, M. C.; Black, Peter; James, Mark; Johnson, James; Jones, Linwood; Miller, Timothy; Ruf, Christopher; Uhlhorn, Eric

2008-01-01

The Hurricane Imaging Radiometer (HIRAD) is an innovative technology development, which offers the potential of new and unique remotely sensed observations of both extreme oceanic wind events and strong precipitation from either UAS or satellite platforms. It is based on the airborne Stepped Frequency Microwave Radiometer (SFMR), which is a proven aircraft remote sensing technique for observing tropical cyclone ocean surface wind speeds and rain rates, including those of major hurricane intensity. The proposed HIRAD instrument advances beyond the current nadir viewing SFMR to an equivalent wide-swath SFMR imager using passive microwave synthetic thinned aperture radiometer technology. This sensor will operate over 4-7 GHz (C-band frequencies) where the required tropical cyclone remote sensing physics has been validated by both SFMR and WindSat radiometers. HIRAD incorporates a unique, technologically advanced array antenna and several other technologies successfully demonstrated by the NASA's Instrument Incubator Program. A brassboard version of the instrument is complete and has been successfully tested in an anechoic chamber, and development of the aircraft instrument is well underway. HIRAD will be a compact, lightweight, low-power instrument with no moving parts that will produce wide-swath imagery of ocean vector winds and rain during hurricane conditions when existing microwave sensors (radiometers or scatterometers) are hindered. Preliminary studies show that HIRAD will have a significant positive impact on analyses as either a new aircraft or satellite sensor.

Validation of Rain Rate Retrievals for the Airborne Hurricane Imaging Radiometer (HIRAD)

NASA Technical Reports Server (NTRS)

Jacob, Maria Marta; Salemirad, Matin; Jones, W. Linwood; Biswas, Sayak; Cecil, Daniel

2015-01-01

The NASA Hurricane and Severe Storm Sentinel (HS3) mission is an aircraft field measurements program using NASA's unmanned Global Hawk aircraft system for remote sensing and in situ observations of Atlantic and Caribbean Sea hurricanes. One of the principal microwave instruments is the Hurricane Imaging Radiometer (HIRAD), which measures surface wind speeds and rain rates. For validation of the HIRAD wind speed measurement in hurricanes, there exists a comprehensive set of comparisons with the Stepped Frequency Microwave Radiometer (SFMR) with in situ GPS dropwindsondes [1]. However, for rain rate measurements, there are only indirect correlations with rain imagery from other HS3 remote sensors (e.g., the dual-frequency Ka- & Ku-band doppler radar, HIWRAP), which is only qualitative in nature. However, this paper presents results from an unplanned rain rate measurement validation opportunity that occurred in 2013, when HIRAD flew over an intense tropical squall line that was simultaneously observed by the Tampa NEXRAD meteorological radar (Fig. 1). During this experiment, Global Hawk flying at an altitude of 18 km made 3 passes over the rapidly propagating thunderstorm, while the TAMPA NEXRAD perform volume scans on a 5-minute interval. Using the well-documented NEXRAD Z-R relationship, 2D images of rain rate (mm/hr) were obtained at two altitudes (3 km & 6 km), which serve as surface truth for the HIRAD rain rate retrievals. A preliminary comparison of HIRAD rain rate retrievals (image) for the first pass and the corresponding closest NEXRAD rain image is presented in Fig. 2 & 3. This paper describes the HIRAD instrument, which 1D synthetic-aperture thinned array radiometer (STAR) developed by NASA Marshall Space Flight Center [2]. The rain rate retrieval algorithm, developed by Amarin et al. [3], is based on the maximum likelihood estimation (MLE) technique, which compares the observed Tb's at the HIRAD operating frequencies of 4, 5, 6 and 6.6 GHz with corresponding theoretical Tb values from a forward radiative transfer model (RTM). The optimum solution is the integrated rain rate that minimizes the difference between RTM and observed values. Because the excess Tb from rain comes from the direct upwelling and the indirect reflected downwelling paths through the atmosphere, there are several assumptions made for the 2D rain distribution in the antenna incident plane (crosstrack to flight direction). The opportunity to knowing 2D rain surface truth from NEXRAD at two different altitudes will enable a comprehensive evaluation to be preformed and reported in this paper.

Simultaneous Transmit and Receive Performance of an 8-channel Digital Phased Array

DTIC Science & Technology

2017-01-16

Lincoln Laboratory Lexington, Massachusetts, USA Abstract—The Aperture- Level Simultaneous Transmit and Re- ceive (ALSTAR) architecture enables extremely...In [1], the Aperture- Level Simultaneous Transmit and Receive (ALSTAR) architecture was proposed for achieving STAR using a fully digital phased array...Aperture- Level Simultaneous Transmit and Receive (ALSTAR) architecture enables STAR functionality in a digital phased array without the use of specialized

Design, fabrication and deployment of a miniaturized spectrometer radiometer based on MMIC technology for tropospheric water vapor profiling

NASA Astrophysics Data System (ADS)

Iturbide-Sanchez, Flavio

This dissertation describes the design, fabrication and deployment of the Compact Microwave Radiometer for Humidity profiling (CMR-H). The CMR-H is a new and innovative spectrometer radiometer that is based on monolithic microwave and millimeter-wave integrated circuit (MMIC) technology and is designed for tropospheric water vapor profiling. The CMR-H simultaneously measures microwave emission at four optimally-selected frequency channels near the 22.235 GHz water vapor absorption line, constituting a new set of frequencies for the retrieval of the water vapor profile. State-of-the-art water vapor radiometers either measure at additional channels with redundant information or perform multi-frequency measurements sequentially. The fabrication of the CMR-H demonstrates the capability of MMIC technology to reduce substantially the operational power consumption and size of the RF and IF sections. Those sections comprise much of the mass and volume of current microwave receivers for remote sensing, except in the case of large antennas. The use of the compact box-horn array antenna in the CMR-H demonstrates its capability to reduce the mass and volume of microwave radiometers, while maintaining similar performance to that of commonly-used, bulky horn antennas. Due to its low mass, low volume, low power consumption, fabrication complexity and cost, the CMR-H represents a technological improvement in the design of microwave radiometers for atmospheric water vapor observations. The field test and validation of the CMR-H described in this work focuses on comparisons of measurements during two field experiments from the CMR-H and a state-of-the-art microwave radiometer, which measures only in a volume subtended by the zenith-pointing antenna's beam pattern. In contrast, the CMR-H is designed to perform volumetric scans and to function correctly as a node in a network of radiometers. Mass production of radiometers based on the CMR-H design is expected to enable the implementation of a dense network of radiometers designed to perform measurements of the 3-D water vapor field, with the potential to improve weather forecasting, particularly the location and timing of the initiation of intense convective activity responsible for potentially damaging winds, rain, hail and lightning.

Localization of Southern Resident Killer Whales Using Two Star Arrays to Support Marine Renewable Energy

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

Ren, Huiying; Deng, Zhiqun; Carlson, Thomas J.

2012-10-19

Tidal power has been identified as one of the most potential commercial-scale renewable energy sources. Puget Sound, Washington, is a potential site to deploy tidal power generating devices. The risk of injury for killer whales needs to be managed before the deployment of these types of devices can be approved by regulating authorities. A passive acoustic system consisting of two star arrays, each with four hydrophones, was designed and implemented for the detection and localization of Southern Resident killer whales. Deployment of the passive acoustic system was conducted at Sequim Bay, Washington. A total of nine test locations were chosen,more » within a radius of 250 m around the star arrays, to test our localization approach. For the localization algorithm, a least square solver was applied to obtain a bearing location from each star array. The final source location was determined by the intersection of the bearings given by each of the two star arrays. Bearing and distance errors were obtained to conduct comparison between the calculated and true (from Global Positioning System) locations. The results indicated that bearing errors were within 1.04º for eight of the test locations; one location had bearing errors slightly larger than expected due to the strong background noise at that position. For the distance errors, six of the test locations were within the range of 1.91 to 32.36 m. The other two test locations were near the intersection line between the centers of the two star arrays, which were expected to have large errors from the theoretical sensitivity analysis performed.« less

Surveying Low-Mass Star Formation with the Submillimeter Array

NASA Astrophysics Data System (ADS)

Dunham, Michael

2018-01-01

Large astronomical surveys yield important statistical information that can’t be derived from single-object and small-number surveys. In this talk I will review two recent surveys in low-mass star formation undertaken by the Submillimeter Array (SMA): a millimeter continuum survey of disks surrounding variably accreting young stars, and a complete continuum and molecular line survey of all protostars in the nearby Perseus Molecular Cloud. I will highlight several new insights into the processes by which low-mass stars gain their mass that have resulted from the statistical power of these surveys.

Assessment of Radiometer Calibration with GPS Radio Occultation for the MiRaTA CubeSat Mission.

PubMed

Marinan, Anne D; Cahoy, Kerri L; Bishop, Rebecca L; Lui, Susan S; Bardeen, James R; Mulligan, Tamitha; Blackwell, William J; Leslie, R Vincent; Osaretin, Idahosa; Shields, Michael

2016-12-01

The Microwave Radiometer Technology Acceleration (MiRaTA) is a 3U CubeSat mission sponsored by the NASA Earth Science Technology Office (ESTO). The science payload on MiRaTA consists of a tri-band microwave radiometer and Global Positioning System (GPS) radio occultation (GPSRO) sensor. The microwave radiometer takes measurements of all-weather temperature (V-band, 50-57 GHz), water vapor (G-band, 175-191 GHz), and cloud ice (G-band, 205 GHz) to provide observations used to improve weather forecasting. The Aerospace Corporation's GPSRO experiment, called the Compact TEC (Total Electron Content) and Atmospheric GPS Sensor (CTAGS), measures profiles of temperature and pressure in the upper troposphere/lower stratosphere (∼20 km) and electron density in the ionosphere (over 100 km). The MiRaTA mission will validate new technologies in both passive microwave radiometry and GPS radio occultation: (1) new ultra-compact and low-power technology for multi-channel and multi-band passive microwave radiometers, (2) the application of a commercial off the shelf (COTS) GPS receiver and custom patch antenna array technology to obtain neutral atmospheric GPSRO retrieval from a nanosatellite, and (3) a new approach to spaceborne microwave radiometer calibration using adjacent GPSRO measurements. In this paper, we focus on objective (3), developing operational models to meet a mission goal of 100 concurrent radiometer and GPSRO measurements, and estimating the temperature measurement precision for the CTAGS instrument based on thermal noise. Based on an analysis of thermal noise of the CTAGS instrument, the expected temperature retrieval precision is between 0.17 K and 1.4 K, which supports the improvement of radiometric calibration to 0.25 K.

Assessment of Radiometer Calibration with GPS Radio Occultation for the MiRaTA CubeSat Mission

PubMed Central

Marinan, Anne D.; Cahoy, Kerri L.; Bishop, Rebecca L.; Lui, Susan S.; Bardeen, James R.; Mulligan, Tamitha; Blackwell, William J.; Leslie, R. Vincent; Osaretin, Idahosa; Shields, Michael

2017-01-01

The Microwave Radiometer Technology Acceleration (MiRaTA) is a 3U CubeSat mission sponsored by the NASA Earth Science Technology Office (ESTO). The science payload on MiRaTA consists of a tri-band microwave radiometer and Global Positioning System (GPS) radio occultation (GPSRO) sensor. The microwave radiometer takes measurements of all-weather temperature (V-band, 50-57 GHz), water vapor (G-band, 175-191 GHz), and cloud ice (G-band, 205 GHz) to provide observations used to improve weather forecasting. The Aerospace Corporation's GPSRO experiment, called the Compact TEC (Total Electron Content) and Atmospheric GPS Sensor (CTAGS), measures profiles of temperature and pressure in the upper troposphere/lower stratosphere (∼20 km) and electron density in the ionosphere (over 100 km). The MiRaTA mission will validate new technologies in both passive microwave radiometry and GPS radio occultation: (1) new ultra-compact and low-power technology for multi-channel and multi-band passive microwave radiometers, (2) the application of a commercial off the shelf (COTS) GPS receiver and custom patch antenna array technology to obtain neutral atmospheric GPSRO retrieval from a nanosatellite, and (3) a new approach to spaceborne microwave radiometer calibration using adjacent GPSRO measurements. In this paper, we focus on objective (3), developing operational models to meet a mission goal of 100 concurrent radiometer and GPSRO measurements, and estimating the temperature measurement precision for the CTAGS instrument based on thermal noise. Based on an analysis of thermal noise of the CTAGS instrument, the expected temperature retrieval precision is between 0.17 K and 1.4 K, which supports the improvement of radiometric calibration to 0.25 K. PMID:28828144

ALMA observations towards G023.01-00.41 .

NASA Astrophysics Data System (ADS)

Sanna, A.; Moscadelli, L.; Cesaroni, R.; Caratti o Garatti, A.; Menten, K. M.; Kölligan, A.; Kuiper, R.

We want to understand whether or not young stars, with masses of tens of Solar masses, can form in the disk accretion scenario. This challenge requires to resolve the spatial morphology of gas and dust within a few 1000 au of a massive young stellar object, and to measure the gas kinematics with respect to the star. Also, because the gas kinematics near the young star can be a mixture of rotating, expanding, and infalling motions all together, to separate each velocity component it is necessary to map the emission of various gas tracers, as well as to image the circumstellar gas at different distances from the star. With this in mind, we made use of the Atacama Large Millimeter Array (ALMA) at wavelengths near 1 mm, with the aim to image the dense molecular gas in the vicinity of a well-known O-type young star. We previously observed this source with the Submillimeter Array (SMA), at scales of about 0.1 pc, with the Karl G. Jansky Very Large Array (VLA), at scales of the order of 1000 au, and with the Very Long Baseline Array (VLBA) and European VLBI Network (EVN), at scales of a few au.

Columnar water vapor retrievals from multifilter rotating shadowband radiometer data

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

Alexandrov, Mikhail; Schmid, Beat; Turner, David D.

2009-01-26

The Multi-Filter Rotating Shadowband Radiometer (MFRSR) measures direct and diffuse irradiances in the visible and near IR spectral range. In addition to characteristics of atmospheric aerosols, MFRSR data also allow retrieval of precipitable water vapor (PWV) column amounts, which are determined from the direct normal irradiances in the 940 nm spectral channel. The HITRAN 2004 spectral database was used in our retrievals to model the water vapor absorption. We present a detailed error analysis describing the influence of uncertainties in instrument calibration and spectral response, as well as those in available spectral databases, on the retrieval results. The results ofmore » our PWV retrievals from the Southern Great Plains (SGP) site operated by the DOE Atmospheric Radiation Measurement (ARM) Program were compared with correlative standard measurements by Microwave Radiometers (MWRs) and a Global Positioning System (GPS) water vapor sensor, as well as with retrievals from other solar radiometers (AERONET’s CIMEL, AATS-6). Some of these data are routinely available at the SGP’s Central Facility, however, we also used measurements from a wider array of instrumentation deployed at this site during the Water Vapor Intensive Observation Period (WVIOP2000) in September – October 2000. The WVIOP data show better agreement between different solar radiometers or between different microwave radiometers (both groups showing relative biases within 4%) than between these two groups of instruments, with MWRs values being consistently higher (up to 14%) than those from solar instruments. We also demonstrate the feasibility of using MFRSR network data for creation of 2D datasets comparable with the MODIS satellite water vapor product.« less

Comparison of the measured and predicted response of the Earth Radiation Budget Experiment active cavity radiometer during solar observations

NASA Technical Reports Server (NTRS)

Mahan, J. R.; Tira, N. E.; Lee, Robert B., III; Keynton, R. J.

1989-01-01

The Earth Radiation Budget Experiment consists of an array of radiometric instruments placed in earth orbit by the National Aeronautics and Space Administration to monitor the longwave and visible components of the earth's radiation budget. Presented is a dynamic electrothermal model of the active cavity radiometer used to measure the earth's total radiative exitance. Radiative exchange is modeled using the Monte Carlo method and transient conduction is treated using the finite element method. Also included is the feedback circuit which controls electrical substitution heating of the cavity. The model is shown to accurately predict the dynamic response of the instrument during solar calibration.

Improved Magnetic STAR Methods for Real-Time, Point-by-Point Localization of Unexploded Ordnance and Buried Mines

DTIC Science & Technology

2008-09-01

of magnetic UXO. The prototype STAR Sensor comprises: a) A cubic array of eight fluxgate magnetometers . b) A 24-channel data acquisition/signal...array (shaded boxes) of eight low noise Triaxial Fluxgate Magnetometers (TFM) develops 24 channels of vector B- field data. Processor hardware

Large area mapping of soil moisture using the ESTAR passive microwave radiometer

NASA Technical Reports Server (NTRS)

Jackson, T. J.; Levine, D. M.; Swift, C. T.; Schmugge, T. J.

1994-01-01

Investigations designed to study land surface hydrologic-atmospheric interactions, showing the potential of L band passive microwave radiometry for measuring surface soil moisture over large areas, are discussed. Satisfying the data needs of these investigations requires the ability to map large areas rapidly. With aircraft systems this means a need for more beam positions over a wider swath on each flightline. For satellite systems the essential problem is resolution. Both of these needs are currently being addressed through the development and verification of Electronically Scanned Thinned Array Radiometer (ESTAR) technology. The ESTAR L band radiometer was evaluated for soil moisture mapping applications in two studies. The first was conducted over the semiarid rangeland Walnut Gulch watershed located in south eastern Arizona (U.S.). The second was performed in the subhumid Little Washita watershed in south west Oklahoma (U.S.). Both tests showed that the ESTAR is capable of providing soil moisture with the same level of accuracy as existing systems.

Observations of C-Band Brightness Temperature and Ocean Surface Wind Speed and Rain Rate in Hurricanes Earl And Karl (2010)

NASA Technical Reports Server (NTRS)

Miller, Timothy; James, Mark; Roberts, Brent J.; Biswax, Sayak; Uhlhorn, Eric; Black, Peter; Linwood Jones, W.; Johnson, Jimmy; Farrar, Spencer; Sahawneh, Saleem

2012-01-01

Ocean surface emission is affected by: a) Sea surface temperature. b) Wind speed (foam fraction). c) Salinity After production of calibrated Tb fields, geophysical fields wind speed and rain rate (or column) are retrieved. HIRAD utilizes NASA Instrument Incubator Technology: a) Provides unique observations of sea surface wind, temp and rain b) Advances understanding & prediction of hurricane intensity c) Expands Stepped Frequency Microwave Radiometer capabilities d) Uses synthetic thinned array and RFI mitigation technology of Lightweight Rain Radiometer (NASA Instrument Incubator) Passive Microwave C-Band Radiometer with Freq: 4, 5, 6 & 6.6 GHz: a) Version 1: H-pol for ocean wind speed, b) Version 2: dual ]pol for ocean wind vectors. Performance Characteristics: a) Earth Incidence angle: 0deg - 60deg, b) Spatial Resolution: 2-5 km, c) Swath: approx.70 km for 20 km altitude. Observational Goals: WS 10 - >85 m/s RR 5 - > 100 mm/hr.

Chemistry and Star Formation: A Love-Hate Relationship

NASA Astrophysics Data System (ADS)

Jiménez-Serra, Izaskun; Zhang, Qizhou; Patel, Nimesh; Lu, Xing; Wang, Ke; Testi, Leonardo; Caselli, Paola; Martin-Pintado, Jesus

2014-06-01

The development of the broad bandwidth receivers at the Submillimeter Array (SMA) a decade ago opened up the possibility to observe tens of molecular lines at high angular resolution simultaneously. The unprecedented wealth of molecular line data provided by the SMA allowed for the first time detailed studies of the chemistry in star-forming regions. These studies have revealed that chemistry is a useful tool to pin down the internal physical structure and the physical processes involved in the process of low-mass and high-mass star formation. In this talk, I will review the most important advances in our understanding of the star-formation process through chemistry thanks to the SMA, and I will present the challenges that will be faced in the next decade in this field of research thanks to the advent of new instrumentation such as the Atacama Large Millimeter/Submillimeter Array and the Square Kilometer Array.

Star Formation as Seen by the Infrared Array Camera on Spitzer

NASA Technical Reports Server (NTRS)

Smith, Howard A.; Allen, L.; Megeath, T.; Barmby, P.; Calvet, N.; Fazio, G.; Hartmann, L.; Myers, P.; Marengo, M.; Gutermuth, R.

2004-01-01

The Infrared Array Camera (IRAC) onboard Spitzer has imaged regions of star formation (SF) in its four IR bands with spatial resolutions of approximately 2"/pixel. IRAC is sensitive enough to detect very faint, embedded young stars at levels of tens of Jy, and IRAC photometry can categorize their stages of development: from young protostars with infalling envelopes (Class 0/1) to stars whose infrared excesses derive from accreting circumstellar disks (Class 11) to evolved stars dominated by photospheric emission. The IRAC images also clearly reveal and help diagnose associated regions of shocked and/or PDR emission in the clouds; we find existing models provide a good start at explaining the continuum of the SF regions IRAC observes.

First Surface-resolved Results with the Infrared Optical Telescope Array Imaging Interferometer: Detection of Asymmetries in Asymptotic Giant Branch Stars

NASA Astrophysics Data System (ADS)

Ragland, S.; Traub, W. A.; Berger, J.-P.; Danchi, W. C.; Monnier, J. D.; Willson, L. A.; Carleton, N. P.; Lacasse, M. G.; Millan-Gabet, R.; Pedretti, E.; Schloerb, F. P.; Cotton, W. D.; Townes, C. H.; Brewer, M.; Haguenauer, P.; Kern, P.; Labeye, P.; Malbet, F.; Malin, D.; Pearlman, M.; Perraut, K.; Souccar, K.; Wallace, G.

2006-11-01

We have measured nonzero closure phases for about 29% of our sample of 56 nearby asymptotic giant branch (AGB) stars, using the three-telescope Infrared Optical Telescope Array (IOTA) interferometer at near-infrared wavelengths (H band) and with angular resolutions in the range 5-10 mas. These nonzero closure phases can only be generated by asymmetric brightness distributions of the target stars or their surroundings. We discuss how these results were obtained and how they might be interpreted in terms of structures on or near the target stars. We also report measured angular sizes and hypothesize that most Mira stars would show detectable asymmetry if observed with adequate angular resolution.

Constraining Cosmic Dawn and Cosmological Reionization via the global redshifted 21-cm signal

NASA Astrophysics Data System (ADS)

Singh, Saurabh

2018-01-01

The formation of first stars and consequent thermal evolution in baryons during Cosmic Dawn and the Epoch of Reionization (EoR) is poorly constrained. The 21-cm line transition of neutral hydrogen is one of the richest probes of the astrophysics during this era. The signal has the potential to reveal the nature and timing of the emergence of first stars, first light, and the consequent evolution in thermal and ionization state of the baryons.The detection of the global redshifted 21-cm signal, which represents the mean thermal history of the gas, is challenging since it is extremely faint and seen through orders of magnitude stronger contributions from Galactic and extragalactic foregrounds. Man-made terrestrial Radio Frequency Interference (RFI) and the exacting tolerances required on instrument systematics make the detection even more daunting.The design considerations for a precision spectral radiometer are first listed, and a comparison is made of different radiometer configurations, including short and zero baseline interferometers along with methods to enhance the response. We discuss the relative merits of different methods.We then describe SARAS 2, a spectral radiometer custom-designed for precision measurement of the global 21-cm signal. SARAS 2 has been designed to have a system transfer function and internal systematics – both multiplicative and additive – to be spectrally smooth so as to allow a separation of foregrounds and systematics from plausible and predicted global cosmological 21-cm signals. The algorithms for calibration and RFI mitigation are carefully developed so that they do not introduce spectral features that may confuse the detection of the 21-cm signal.We present the outcomes for cosmology from analysis of 60 hr observing with the radiometer deployed at the Timbaktu Collective in Southern India. The detailed analysis of the data reveals an RMS noise level of 11 mK, without being limited by systematic structures. The likelihood ratios are computed from the data for plausible 21-cm signals predicted by theoretical models. First light with SARAS 2 disfavors the scenario of rapid reionization and also the models in which the first X-ray sources have poor heating efficiency.

Imaging Stellar Surface with The CHARA Array

NASA Astrophysics Data System (ADS)

Schaefer, Gail

2018-04-01

I will provide an overview of results on imaging stellar surfaces with the CHARA Array. These include imaging gravity darkening on rapid rotators, starspots on magnetically active stars, convective cells on red supergiants, and stellar winds from massive stars. In binary systems, the CHARA Array has been used to observe tidal distortions from Roche lobe filling in interactive binaries, transiting companions as they move through eclipse, and the angular expansion of novae explosions. I will discuss the impact of these results in an astrophysical context.

Star sensing for an earth imaging sensor

NASA Technical Reports Server (NTRS)

Ellis, Kenneth K. (Inventor); Griffith, Paul C. (Inventor)

2012-01-01

A star sensor includes (a) a scan mirror for scanning at least one star; (b) a detector array, coupled to the scan mirror, for detecting the one star; and (c) a processor, coupled to the detector array. The processor includes a first filter configured to reduce noise spikes in the detected one star, and provide a detection mask of filtered data. Also included is a second filter configured to reduce non-contiguous samples in the detection mask. A centroid calculator is included to determine a location of the one star, after the first and second filtering. The first filter includes a median filter, followed by an averaging filter, both configured to filter the one star in an along-scan direction of the scan mirror. The first filter includes another median filter, which is configured to filter the detected one star in the cross-scan direction of the scan mirror. An adder is included to subtract (a) output data from the other median filter from (b) output data from the averaging filter and provide filtered star data to the second filter.

Cryogenic radiometers and intensity-stabilized lasers for Eos radiometric calibrations

NASA Technical Reports Server (NTRS)

Foukal, P.; Hoyt, C.; Jauniskis, L.

1991-01-01

Liquid helium-cooled electrical substitution radiometers (ESRs) provide irradiance standards with demonstrated absolute accuracy at the 0.01 percent level, spectrally flat response between the UV and IR, and sensitivity down to 0.1 nW/sq cm. We describe an automated system developed for NASA - Goddard Space Flight Center, consisting of a cryogenic ESR illuminated by servocontrolled laser beams. This system is designed to provide calibration of single-element and array detectors over the spectral range between 257nm in the UV to 10.6 microns in the IR. We also describe a cryogenic ESR optimized for black body calibrations that has been installed at NIST, and another that is under construction for calibrations of the CERES scanners planned for Eos.

640 x 480 MWIR and LWIR camera system developments

NASA Astrophysics Data System (ADS)

Tower, John R.; Villani, Thomas S.; Esposito, Benjamin J.; Gilmartin, Harvey R.; Levine, Peter A.; Coyle, Peter J.; Davis, Timothy J.; Shallcross, Frank V.; Sauer, Donald J.; Meyerhofer, Dietrich

1993-01-01

The performance of a 640 x 480 PtSi, 3,5 microns (MWIR), Stirling cooled camera system with a minimum resolvable temperature of 0.03 is considered. A preliminary specification of a full-TV resolution PtSi radiometer was developed using the measured performance characteristics of the Stirling cooled camera. The radiometer is capable of imaging rapid thermal transients from 25 to 250 C with better than 1 percent temperature resolution. This performance is achieved using the electronic exposure control capability of the MOS focal plane array (FPA). A liquid nitrogen cooled camera with an eight-position filter wheel has been developed using the 640 x 480 PtSi FPA. Low thermal mass packaging for the FPA was developed for Joule-Thomson applications.

640 x 480 MWIR and LWIR camera system developments

NASA Astrophysics Data System (ADS)

Tower, J. R.; Villani, T. S.; Esposito, B. J.; Gilmartin, H. R.; Levine, P. A.; Coyle, P. J.; Davis, T. J.; Shallcross, F. V.; Sauer, D. J.; Meyerhofer, D.

The performance of a 640 x 480 PtSi, 3,5 microns (MWIR), Stirling cooled camera system with a minimum resolvable temperature of 0.03 is considered. A preliminary specification of a full-TV resolution PtSi radiometer was developed using the measured performance characteristics of the Stirling cooled camera. The radiometer is capable of imaging rapid thermal transients from 25 to 250 C with better than 1 percent temperature resolution. This performance is achieved using the electronic exposure control capability of the MOS focal plane array (FPA). A liquid nitrogen cooled camera with an eight-position filter wheel has been developed using the 640 x 480 PtSi FPA. Low thermal mass packaging for the FPA was developed for Joule-Thomson applications.

A high resolution soil moisture radiometer

NASA Technical Reports Server (NTRS)

Dod, L. R.

1980-01-01

The design of an L-band high resolution soil moisture radiometer is described. The selected system is a planar slotted waveguide array at L-band frequencies. The square aperture is 74.75 m by 74.75 m subdivided into 8 tilted subarrays. The system has a 290 km circular orbit and provides a spatial resolution of 1 km. The aperture forms 230 simultaneous beams in a cross-track pattern which covers a swath 420 km wide. A revisit time of 6 days is provided for an orbit inclination of 50 deg. The 1 km resolution cell allows an integration time of 1/7 second and sharing this time period sequentially between two orthogonal polarization modes can provide a temperature resolution of 0.7 K.

Feasibility Study of Utilizing Existing Infrared Array Cameras for Daylight Star Tracking on NASA's Ultra Long Duration Balloon (ULDB) Missions

NASA Technical Reports Server (NTRS)

Tueller, Jack (Technical Monitor); Fazio, Giovanni G.; Tolls, Volker

2004-01-01

The purpose of this study was to investigate the feasibility of developing a daytime star tracker for ULDB flights using a commercially available off-the-shelf infrared array camera. This report describes the system used for ground-based tests, the observations, the test results, and gives recommendations for continued development.

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.

Nuclear Spectroscopic Telescope Array (NuSTAR) Mission

NASA Technical Reports Server (NTRS)

Kim, Yunjin; Willis, Jason; Dodd, Suzanne; Harrison, Fiona; Forster, Karl; Craig, William; Bester, Manfred; Oberg, David

2013-01-01

The Nuclear Spectroscopic Telescope Array (NuSTAR) is a National Aeronautics and Space Administration (NASA) Small Explorer mission that carried the first focusing hard X-ray (6-79 keV) telescope into orbit. It was launched on a Pegasus rocket into a low-inclination Earth orbit on June 13, 2012, from Reagan Test Site, Kwajalein Atoll. NuSTAR will carry out a two-year primary science mission. The NuSTAR observatory is composed of the X-ray instrument and the spacecraft. The NuSTAR spacecraft is three-axis stabilized with a single articulating solar array based on Orbital Sciences Corporation's LEOStar-2 design. The NuSTAR science instrument consists of two co-aligned grazing incidence optics focusing on to two shielded solid state CdZnTe pixel detectors. The instrument was launched in a compact, stowed configuration, and after launch, a 10-meter mast was deployed to achieve a focal length of 10.15 m. The NuSTAR instrument provides sub-arcminute imaging with excellent spectral resolution over a 12-arcminute field of view. The NuSTAR observatory will be operated out of the Mission Operations Center (MOC) at UC Berkeley. Most science targets will be viewed for a week or more. The science data will be transferred from the UC Berkeley MOC to a Science Operations Center (SOC) located at the California Institute of Technology (Caltech). In this paper, we will describe the mission architecture, the technical challenges during the development phase, and the post-launch activities.

GeoSTAR - A Synthetic Aperture Microwave Sounder for Geostationary Missions

NASA Technical Reports Server (NTRS)

Lambrigtsen, Bjorn; Wilson, William; Tanner, Alan; Kangaslahti, Pekka

2004-01-01

The Geostationary Synthetic Thinned Aperture Radiometer (GeoSTAR) is a new microwave atmospheric sounder under development. It will bring capabilities similar to those now available on low-earth orbiting environmental satellites to geostationary orbit - where such capabilities have not been available. GeoSTAR will synthesize the multimeter aperture needed to achieve the required spatial resolution, which will overcome the obstacle that has prevented a GEO microwave sounder from being implemented until now. The synthetic aperture approach has until recently not been feasible, due to the high power needed to operate the on-board high-speed massively parallel processing system required for 2D-synthesis, as well as a number of system and calibration obstacles. The development effort under way at JPL, with important contributions from the Goddard Space Flight Center and the University of Michigan, is intended to demonstrate the measurement concept and retire much of the technology risk.

Imaging of Stellar Surfacess Using Radio Facilities Including ALMA

NASA Astrophysics Data System (ADS)

O'Gorman, Eamon

2018-04-01

Until very recently, studies focusing on imaging stars at continuum radio wavelengths (here defined as submillimeter, millimeter, and centimeter wavelengths) has been scarce. These studies have mainly been carried out with the Very Large Array on a handful of evolved stars (i.e., Asymptotic Giant Branch and Red Supergiant stars) whereby their stellar disks have just about been spatially resolved. Some of these results however, have challenged our historical views on the nature of evolved star atmospheres. Now, the very long baselines of the Atacama Large Millimeter/submillimeter Array and the newly upgraded Karl G. Jansky Very Large Array provide a new opportunity to image these atmospheres at unprecedented spatial resolution and sensitivity across a much wider portion of the radio spectrum. In this talk I will first provide a history of stellar radio imaging and then discuss some recent exciting ALMA results. Finally I will present some brand new multi-wavelength ALMA and VLA results for the famous red supergiant Antares.

Sizzling Remains of a Dead Star

NASA Image and Video Library

2013-01-07

This new view of the historical supernova remnant Cassiopeia A, located 11,000 light-years away, was taken by NASA Nuclear Spectroscopic Telescope Array, or NuSTAR. While the star is long dead, its remains are still bursting with action.

Uses of infrared thermography in the low-cost solar array program

NASA Technical Reports Server (NTRS)

Glazer, S. D.

1982-01-01

The Jet Propulsion Laboratory has used infrared thermography extensively in the Low-Cost Solar Array (LSA) photovoltaics program. A two-dimensional scanning infrared radiometer has been used to make field inspections of large free-standing photovoltaic arrays and smaller demonstration sites consisting of integrally mounted rooftop systems. These field inspections have proven especially valuable in the research and early development phases of the program, since certain types of module design flaws and environmental degradation manifest themselves in unique thermal patterns. The infrared camera was also used extensively in a series of laboratory tests on photovoltaic cells to obtain peak cell temperatures and thermal patterns during off-design operating conditions. The infrared field inspections and the laboratory experiments are discussed, and sample results are presented.

Low-cost 20-22 GHz MIC active receiver/radiometer

NASA Technical Reports Server (NTRS)

Mollenkopf, Steven; Katehi, Linda P. B.; Rebeiz, Gabriel M.

1995-01-01

A microwave integrated circuit active receiver is built and tested at 19-25 GHz. The receiver consists of a planar CPW-fed double folded-slot antenna coupled to a six-stage MESFET (metal semiconductor field effect transistors) amplifier and followed by a planar Schottky-diode detector. The folded-slot antenna on a GaAs half-space results in a wide frequency bandwidth suitable for MMIC amplifiers. The measured system performance show a video responsivity close to 1 GV/W at 20 GHz with a 3-dB bandwidth of 1500 MHz. A novel method which uses the planar video detector after the amplifier stages as an RF (radio frequency) mixer is used to measure the noise-figure of the direct detection radiometer. The system noise figure is 4.8 dB at 22 GHz. The radiometer sensitivity to a hot/cold load is 3.8 mu V/K. The measured antenna patterns show a 90% Gaussicity at 20-22 GHz. The active MIC receiver can be integrated monolithically for low-cost applications and is well suited for millimeter-wave linear imaging arrays.

Electron lithography STAR design guidelines. Part 2: The design of a STAR for space applications

NASA Technical Reports Server (NTRS)

Trotter, J. D.; Newman, W.

1982-01-01

The STAR design system developed by NASA enables any user with a logic diagram to design a semicustom digital MOS integrated circuit. The system is comprised of a library of standard logic cells and computr programs to place, route, and display designs implemented with cells from the library. Also described is the development of a radiation-hard array designed for the STAR system. The design is based on the CMOS silicon gate technology developed by SANDIA National Laboratories. The design rules used are given as well as the model parameters developed for the basic array element. Library cells of the CMOS metal gate and CMOS silicon gate technologies were simulated using SPICE, and the results are shown and compared.

Earth Observatory Satellite system definition study. Report 5: System design and specifications. Volume 4: Mission peculiar spacecraft segment and module specifications

NASA Technical Reports Server (NTRS)

1974-01-01

The specifications for the Earth Observatory Satellite (EOS) peculiar spacecraft segment and associated subsystems and modules are presented. The specifications considered include the following: (1) wideband communications subsystem module, (2) mission peculiar software, (3) hydrazine propulsion subsystem module, (4) solar array assembly, and (5) the scanning spectral radiometer.

CIRiS: Compact Infrared Radiometer in Space

NASA Astrophysics Data System (ADS)

Osterman, D. P.; Collins, S.; Ferguson, J.; Good, W.; Kampe, T.; Rohrschneider, R.; Warden, R.

2016-09-01

The Compact Infrared Radiometer in Space (CIRiS) is a thermal infrared radiometric imaging instrument under development by Ball Aerospace for a Low Earth Orbit mission on a CubeSat spacecraft. Funded by the NASA Earth Science Technology Office's In-Space Validation of Earth Science Technology (InVEST) program, the mission objective is technology demonstration for improved on-orbit radiometric calibration. The CIRiS calibration approach uses a scene select mirror to direct three calibration views to the focal plane array and to transfer the resulting calibrated response to earth images. The views to deep space and two blackbody sources, including one at a selectable temperature, provide multiple options for calibration optimization. Two new technologies, carbon nanotube blackbody sources and microbolometer focal plane arrays with reduced pixel sizes, enable improved radiometric performance within the constrained 6U CubeSat volume. The CIRiS instrument's modular design facilitates subsystem modifications as required by future mission requirements. CubeSat constellations of CIRiS and derivative instruments offer an affordable approach to achieving revisit times as short as one day for diverse applications including water resource and drought management, cloud, aerosol, and dust studies, and land use and vegetation monitoring. Launch is planned for 2018.

Improving ROLO lunar albedo model using PLEIADES-HR satellites extra-terrestrial observations

NASA Astrophysics Data System (ADS)

Meygret, Aimé; Blanchet, Gwendoline; Colzy, Stéphane; Gross-Colzy, Lydwine

2017-09-01

The accurate on orbit radiometric calibration of optical sensors has become a challenge for space agencies which have developed different technics involving on-board calibration systems, ground targets or extra-terrestrial targets. The combination of different approaches and targets is recommended whenever possible and necessary to reach or demonstrate a high accuracy. Among these calibration targets, the moon is widely used through the well-known ROLO (RObotic Lunar Observatory) model developed by USGS. A great and worldwide recognized work was done to characterize the moon albedo which is very stable. However the more and more demanding needs for calibration accuracy have reached the limitations of the model. This paper deals with two mains limitations: the residual error when modelling the phase angle dependency and the absolute accuracy of the model which is no more acceptable for the on orbit calibration of radiometers. Thanks to PLEIADES high resolution satellites agility, a significant data base of moon and stars images was acquired, allowing to show the limitations of ROLO model and to characterize the errors. The phase angle residual dependency is modelled using PLEIADES 1B images acquired for different quasi-complete moon cycles with a phase angle varying by less than 1°. The absolute albedo residual error is modelled using PLEIADES 1A images taken over stars and the moon. The accurate knowledge of the stars spectral irradiance is transferred to the moon spectral albedo using the satellite as a transfer radiometer. This paper describes the data set used, the ROLO model residual errors and their modelling, the quality of the proposed correction and show some calibration results using this improved model.

Taking the Measure of Massive Stars and their Environments with the CHARA Array Long-baseline Interferometer

NASA Astrophysics Data System (ADS)

Gies, Douglas R.

2017-11-01

Most massive stars are so distant that their angular diameters are too small for direct resolution. However, the observational situation is now much more favorable, thanks to new opportunities available with optical/IR long-baseline interferometry. The Georgia State University Center for High Angular Resolution Astronomy Array at Mount Wilson Observatory is a six-telescope instrument with a maximum baseline of 330 meters, which is capable of resolving stellar disks with diameters as small as 0.2 milliarcsec. The distant stars are no longer out of range, and many kinds of investigations are possible. Here we summarize a number of studies involving angular diameter measurements and effective temperature estimates for OB stars, binary and multiple stars (including the σ Orionis system), and outflows in Luminous Blue Variables. An enlarged visitors program will begin in 2017 that will open many opportunities for new programs in high angular resolution astronomy.

Design of an 8-40 GHz Antenna for the Wideband Instrument for Snow Measurements (WISM)

NASA Technical Reports Server (NTRS)

Durham, Timothy E.; Vanhille, Kenneth J.; Trent, Christopher; Lambert, Kevin M.; Miranda, Felix A.

2015-01-01

Measurement of land surface snow remains a significant challenge in the remote sensing arena. Developing the tools needed to remotely measure Snow Water Equivalent (SWE) is an important priority. The Wideband Instrument for Snow Measurements (WISM) is being developed to address this need. WISM is an airborne instrument comprised of a dual-frequency (X- and Ku-bands) Synthetic Aperture Radar (SAR) and dual-frequency (K- and Ka-bands) radiometer. A unique feature of this instrument is that all measurement bands share a common antenna aperture consisting of an array feed reflector that covers the entire bandwidth. This paper covers the design and fabrication of the wideband array feed which is based on tightly coupled dipole arrays. Implementation using a relatively new multi-layer microfabrication process results in a small, 6x6 element, dual-linear polarized array with beamformer that operates from 8 to 40 gigahertz.

A survey of current solid state star tracker technology

NASA Astrophysics Data System (ADS)

Armstrong, R. W.; Staley, D. A.

1985-12-01

This paper is a survey of the current state of the art in design of star trackers for spacecraft attitude determination systems. Specific areas discussed are sensor technology, including the current state-of-the-art solid state sensors and techniques of mounting and cooling the sensor, analog image preprocessing electronics performance, and digital processing hardware and software. Three examples of area array solid state star tracker development are presented - ASTROS, developed by the Jet Propulsion Laboratory, the Retroreflector Field Tracker (RFT) by Ball Aerospace, and TRW's MADAN. Finally, a discussion of solid state line arrays explores the possibilities for one-dimensional imagers which offer simplified scan control electronics.

Electron lithography STAR design guidelines. Part 3: The mosaic transistor array applied to custom microprocessors. Part 4: Stores logic arrays, SLAs implemented with clocked CMOS

NASA Technical Reports Server (NTRS)

Trotter, J. D.

1982-01-01

The Mosaic Transistor Array is an extension of the STAR system developed by NASA which has dedicated field cells designed to be specifically used in semicustom microprocessor applications. The Sandia radiation hard bulk CMOS process is utilized in order to satisfy the requirements of space flights. A design philosophy is developed which utilizes the strengths and recognizes the weaknesses of the Sandia process. A style of circuitry is developed which incorporates the low power and high drive capability of CMOS. In addition the density achieved is better than that for classic CMOS, although not as good as for NMOS. The basic logic functions for a data path are designed with compatible interface to the STAR grid system. In this manner either random logic or PLA type structures can be utilized for the control logic.

Surface Wind Vector and Rain Rate Observation Capability of Future Hurricane Imaging Radiometer (HIRAD)

NASA Technical Reports Server (NTRS)

Miller, Timothy; Atlas, Robert; Bailey, M. C.; Black, Peter; El-Nimri, Salem; Hood, Robbie; James, Mark; Johnson, James; Jones, Linwood; Ruf, Christopher;

GIGAS: A set of microwave sensor arrays to detect molecular bremsstrahlung radiation from extensive air shower

NASA Astrophysics Data System (ADS)

Gaïor, R.; Al Samarai, I.; Berat, C.; Blanco Otano, M.; David, J.; Deligny, O.; Lebbolo, H.; Lecoz, S.; Letessier-Selvon, A.; Lhenry-Yvon, I.; Mariş, I. C.; Montanet, F.; Repain, P.; Salamida, F.; Settimo, M.; Stassi, P.; Stutz, A.

2018-04-01

We present the GIGAS (Gigahertz Identification of Giant Air Shower) microwave radio sensor arrays of the EASIER project (Extensive Air Shower Identification with Electron Radiometers), deployed at the site of the Pierre Auger cosmic ray observatory. The aim of these novel arrays is to probe the intensity of the molecular bremsstrahlung radiation expected from the development of the extensive air showers produced by the interaction of ultra high energy cosmic rays in the atmosphere. In the designed setup, the sensors are embedded within the surface detector array of the Pierre Auger observatory allowing us to use the particle signals at ground level to trigger the radio system. A series of seven, then 61 sensors have been deployed in the C-band, followed by a new series of 14 higher sensitivity ones in the C-band and the L-band. The design, the operation, the calibration and the sensitivity to extensive air showers of these arrays are described in this paper.

Near-Far Field Corrections in the Measurement of an Interferometric Two-Dimensional Radiometer in Anechoic Chambers

NASA Astrophysics Data System (ADS)

Selva Valero, Daniel

In 2006 the two-dimensional interferometric radiometer MIRAS will be launched in a satellite by ESA. MIRAS is a Y-shaped array of 64 antennas that provides a radiometric resolution of 1K and a spatial resolution of 10-20Km, a perfect performance for Earth Observation. For the first time it will be taking global direct measures of soil moisture and ocean salinity for three years. Since these parameters are of main importance in weather prediction, they are very useful in studies of Climatic change. Aperture synthesis radiometers reach the same performance than total power ones, but with a major advantage: a much lower mass. This kind of passive radar provides measures of the cross-correlations between each pair of antennas in the array, being each correlation a sample of the visibility function. The brightness temperature distribution can be obtained by Inverse Fourier transform of the visibility function. The image of the brightness temperature will be processed in order to obtain the soil moisture and the ocean salinity. Before the launching a hard work on design and testing the instrument has to be done. Software simulators are necessary to design and predict the behavior of the instrument, but once the instrument is developed, a prototype must be built and all the features have to be tested in anechoic chambers and natural scenarios. When the instrument will be in orbit it will be in far-field from the earth, but this doesn't apply in the chamber. Although it is true that the target is in far-field from every element of the antenna, it is not far enough from the array to consider far-field from the set of antennas. Hence, some corrections must be done in order to transform the results obtained in near-field to the ones that would be obtained in far field. The main contribution of this paper is the expression of the corrections that we must apply to make the measures in anechoic chambers.

Note: cryogenic microstripline-on-Kapton microwave interconnects.

PubMed

Harris, A I; Sieth, M; Lau, J M; Church, S E; Samoska, L A; Cleary, K

2012-08-01

Simple broadband microwave interconnects are needed for increasing the size of focal plane heterodyne radiometer arrays. We have measured loss and crosstalk for arrays of microstrip transmission lines in flex circuit technology at 297 and 77 K, finding good performance to at least 20 GHz. The dielectric constant of Kapton substrates changes very little from 297 to 77 K, and the electrical loss drops. The small cross-sectional area of metal in a printed circuit structure yields overall thermal conductivities similar to stainless steel coaxial cable. Operationally, the main performance tradeoffs are between crosstalk and thermal conductivity. We tested a patterned ground plane to reduce heat flux.

Magic star puzzle for educational mathematics

NASA Astrophysics Data System (ADS)

Gan, Yee Siang; Fong, Wan Heng; Sarmin, Nor Haniza

2013-04-01

One of the interesting fields in recreational mathematics is the magic number arrangement. There are different kinds of arrays in the arrangement for a group of numbers. In particular, one of the arrays in magic number arrangement is called magic star. In fact, magic star involves combinatorics that contributes to geometrical analysis and number theory. Hence, magic star is suitable to be introduced as educational mathematics to cultivate interest in different area of mathematics. To obtain the solutions of normal magic stars of order six, the possible sets of numbers for every line in a magic star have been considered. Previously, the calculation for obtaining the solutions has been done manually which is time-consuming. Therefore, a programming code to generate all the fundamental solutions for normal magic star of order six without including the properties of rotation and reflection has been done. In this puzzle, a magic star puzzle is created by using Matlab software, which enables a user to verify the entries for the cells of magic star of order six. Moreover, it is also user-friendly as it provides interactive commands on the inputs given by the user, which enables the user to detect the incorrect inputs. In addition, user can also choose to view all the fundamental solutions as generated by the programming code.

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.

Performance Assessment of Multi-Array Processing with Ground Truth for Infrasonic, Seismic and Seismo-Acoustic Events

DTIC Science & Technology

2012-07-03

of white noise vectors with square sumable coefficients and components with finite fourth order moments (Shumway et al., 1999). Here, the infrasonic...center in a star -like configuration for reducing the background noise from wind activity along the boundary layer. Sensor data is recorded by 24-bit...the PMCC Algorithm In Figure 19, under the assumption that the source (red star ) is far from the arrays, PMCC starts coherence processing using

Low Average Sidelobe Slot Array Antennas for Radiometer Applications

NASA Technical Reports Server (NTRS)

Rengarajan, Sembiam; Zawardzki, Mark S.; Hodges, Richard E.

2012-01-01

In radiometer applications, it is required to design antennas that meet low average sidelobe levels and low average return loss over a specified frequency bandwidth. It is a challenge to meet such specifications over a frequency range when one uses resonant elements such as waveguide feed slots. In addition to their inherent narrow frequency band performance, the problem is exacerbated due to modeling errors and manufacturing tolerances. There was a need to develop a design methodology to solve the problem. An iterative design procedure was developed by starting with an array architecture, lattice spacing, aperture distribution, waveguide dimensions, etc. The array was designed using Elliott s technique with appropriate values of the total slot conductance in each radiating waveguide, and the total resistance in each feed waveguide. Subsequently, the array performance was analyzed by the full wave method of moments solution to the pertinent integral equations. Monte Carlo simulations were also carried out to account for amplitude and phase errors introduced for the aperture distribution due to modeling errors as well as manufacturing tolerances. If the design margins for the average sidelobe level and the average return loss were not adequate, array architecture, lattice spacing, aperture distribution, and waveguide dimensions were varied in subsequent iterations. Once the design margins were found to be adequate, the iteration was stopped and a good design was achieved. A symmetric array architecture was found to meet the design specification with adequate margin. The specifications were near 40 dB for angular regions beyond 30 degrees from broadside. Separable Taylor distribution with nbar=4 and 35 dB sidelobe specification was chosen for each principal plane. A non-separable distribution obtained by the genetic algorithm was found to have similar characteristics. The element spacing was obtained to provide the required beamwidth and close to a null in the E-plane end-fire direction. Because of the alternating slot offsets, grating lobes called butterfly lobes are produced in non-principal planes close to the H-plane. An attempt to reduce the influence of such grating lobes resulted in a symmetric design.

A study of the thermal and optical characteristics of radiometric channels for Earth radiation budget applications

NASA Technical Reports Server (NTRS)

Mahan, J. R.; Tira, Nour E.

1991-01-01

An improved dynamic electrothermal model for the Earth Radiation Budget Experiment (ERBE) total, nonscanning channels is formulated. This model is then used to accurately simulate two types of dynamic solar observation: the solar calibration and the so-called pitchover maneuver. Using a second model, the nonscanner active cavity radiometer (ACR) thermal noise is studied. This study reveals that radiative emission and scattering by the surrounding parts of the nonscanner cavity are acceptably small. The dynamic electrothermal model is also used to compute ACR instrument transfer function. Accurate in-flight measurement of this transfer function is shown to depend on the energy distribution over the frequency spectrum of the radiation input function. A new array-type field of view limiter, whose geometry controls the input function, is proposed for in-flight calibration of an ACR and other types of radiometers. The point spread function (PSF) of the ERBE and the Clouds and Earth's Radiant Energy System (CERES) scanning radiometers is computed. The PSF is useful in characterizing the channel optics. It also has potential for recovering the distribution of the radiative flux from Earth by deconvolution.

Knudsen pump inspired by Crookes radiometer with a specular wall

NASA Astrophysics Data System (ADS)

Baier, Tobias; Hardt, Steffen; Shahabi, Vahid; Roohi, Ehsan

2017-03-01

A rarefied gas is considered in a channel consisting of two infinite parallel plates between which an evenly spaced array of smaller plates is arranged normal to the channel direction. Each of these smaller plates is assumed to possess one ideally specularly reflective and one ideally diffusively reflective side. When the temperature of the small plates differs from the temperature of the sidewalls of the channel, these boundary conditions result in a temperature profile around the edges of each small plate that breaks the reflection symmetry along the channel direction. This in turn results in a force on each plate and a net gas flow along the channel. The situation is analyzed numerically using the direct simulation Monte Carlo method and compared with analytical results where available. The influence of the ideally specularly reflective wall is assessed by comparing with simulations using a finite accommodation coefficient at the corresponding wall. The configuration bears some similarity to a Crookes radiometer, where a nonsymmetric temperature profile at the radiometer vanes is generated by different temperatures on each side of the vane, resulting in a motion of the rotor. The described principle may find applications in pumping gas on small scales driven by temperature gradients.

Final Steps in Mating NuSTAR to its Rocket

NASA Image and Video Library

2012-02-23

Inside an environmental enclosure at Vandenberg Air Force Base processing facility in California, technicians complete the final steps in mating NASA Nuclear Spectroscopic Telescope Array NuSTAR and its Orbital Sciences Pegasus XL rocket.

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.

New Shortwave Array Spectroradiometer-Hemispheric (SAS-He): Hyperspectral Design and Initial Applications

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

Kassianov, Evgueni I.; Flynn, Connor J M.; Barnard, James C.

2016-10-31

Aerosol optical depth (AOD) derived from hyperspectral measurements can serve as an invaluable input for simultaneous retrievals of particle size distributions and major trace gases. The required hyperspectral measurements are provided by a new ground-based radiometer, the so-called Shortwave Array Spectroradiometer-Hemispheric (SAS-He), recently developed with support from the Department of Energy (DOE) Office Atmospheric Radiation Measurement (ARM) Program. The SAS-He has wide spectral coverage (350-1700nm) and high spectral resolution: about 2.4 nm and 6 nm within 350-1000 nm and 970-1700 nm spectral ranges, respectively. To illustrate an initial performance of the SAS-He, we take advantage of integrated dataset collected duringmore » the ARM-supported Two-Column Aerosol Project (TCAP) over the US coastal region (Cape Cod, Massachusetts). This dataset includes AODs derived using data from Aerosol Robotic Network (AERONET) sunphotometer and Multi-Filter Rotating Shadowband Radiometer (MFRSR). We demonstrate that, on average, the SAS-He AODs closely match the MFRSR and AERONET AODs in the ultraviolet and visible spectral ranges for this area with highly variable AOD. Also, we discuss corrections of SAS-He total optical depth for gas absorption in the near-infrared spectral range and their operational implementation.« less

The hyperion particle-γ detector array

DOE PAGES

Hughes, R. O.; Burke, J. T.; Casperson, R. J.; ...

2017-03-08

Hyperion is a new high-efficiency charged-particle γ-ray detector array which consists of a segmented silicon telescope for charged-particle detection and up to fourteen high-purity germanium clover detectors for the detection of coincident γ rays. The array will be used in nuclear physics measurements and Stockpile Stewardship studies and replaces the STARLiTeR array. In conclusion, this article discusses the features of the array and presents data collected with the array in the commissioning experiment.

Uniting of NuSTAR Spacecraft and Rocket

NASA Image and Video Library

2012-02-23

Inside an environmental enclosure at Vandenberg Air Force Base processing facility in California, solar panels line the sides of NASA Nuclear Spectroscopic Telescope Array NuSTAR, which was just joined to the Orbital Sciences Pegasus XL rocket.

The Deep Space Network: Noise temperature concepts, measurements, and performance

NASA Technical Reports Server (NTRS)

Stelzried, C. T.

1982-01-01

The use of higher operational frequencies is being investigated for improved performance of the Deep Space Network. Noise temperature and noise figure concepts are used to describe the noise performance of these receiving systems. The ultimate sensitivity of a linear receiving system is limited by the thermal noise of the source and the quantum noise of the receiver amplifier. The atmosphere, antenna and receiver amplifier of an Earth station receiving system are analyzed separately and as a system. Performance evaluation and error analysis techniques are investigated. System noise temperature and antenna gain parameters are combined to give an overall system figure of merit G/T. Radiometers are used to perform radio ""star'' antenna and system sensitivity calibrations. These are analyzed and the performance of several types compared to an idealized total power radiometer. The theory of radiative transfer is applicable to the analysis of transmission medium loss. A power series solution in terms of the transmission medium loss is given for the solution of the noise temperature contribution.

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

Hughes, R. O.; Burke, J. T.; Casperson, R. J.

Hyperion is a new high-efficiency charged-particle γ-ray detector array which consists of a segmented silicon telescope for charged-particle detection and up to fourteen high-purity germanium clover detectors for the detection of coincident γ rays. The array will be used in nuclear physics measurements and Stockpile Stewardship studies and replaces the STARLiTeR array. In conclusion, this article discusses the features of the array and presents data collected with the array in the commissioning experiment.

Joint stars phased array radar antenna

NASA Astrophysics Data System (ADS)

Shnitkin, Harold

1994-10-01

The Joint STARS phased array radar system is capable of performing long range airborne surveillance and was used during the Persian Gulf war on two E8-A aircraft to fly many around-the-clock missions to monitor the Kuwait and Iraq battlefield from a safe distance behind the front lines. This paper is a follow-on to previous publications on the subject of the Joint STARS antenna and deals mainly with mission performance and technical aspects not previously covered. Radar data of troop movements and armament installations will be presented, a brief review of the antenna design is given, followed by technical discussions concerning the three-port interferometry, gain and sidelobe design approach, cost control, range test implementation and future improvements.

NuSTAR Inches Toward its Rocket

NASA Image and Video Library

2012-02-23

At Vandenberg Air Force Base processing facility in California, the separation ring on the aft end of NASA Nuclear Spectroscopic Telescope Array NuSTAR, at right, inches its way toward the third stage of an Orbital Sciences Pegasus XL rocket.

KSC-2012-3027

NASA Image and Video Library

2012-05-22

VANDENBERG AFB, Calif. – Technicians install the second half of the payload fairing over the NuSTAR spacecraft as they continue to process the spacecraft and its Pegasus rocket for launch. NuSTAR stands for Nuclear Spectroscopic Telescope Array. Photo credit: NASA/Randy Beaudoin

KSC-2012-3028

NASA Image and Video Library

2012-05-22

VANDENBERG AFB, Calif. – Technicians install the second half of the payload fairing over the NuSTAR spacecraft as they continue to process the spacecraft and its Pegasus rocket for launch. NuSTAR stands for Nuclear Spectroscopic Telescope Array. Photo credit: NASA/Randy Beaudoin

KSC-2012-3023

NASA Image and Video Library

2012-05-22

VANDENBERG AFB, Calif. – Technicians install one half of the payload fairing over the NuSTAR spacecraft as they continue to process the spacecraft and its Pegasus rocket for launch. NuSTAR stands for Nuclear Spectroscopic Telescope Array. Photo credit: NASA/Randy Beaudoin

KSC-2012-3026

NASA Image and Video Library

2012-05-22

VANDENBERG AFB, Calif. – Technicians install the second half of the payload fairing over the NuSTAR spacecraft as they continue to process the spacecraft and its Pegasus rocket for launch. NuSTAR stands for Nuclear Spectroscopic Telescope Array. Photo credit: NASA/Randy Beaudoin

KSC-2012-3022

NASA Image and Video Library

2012-05-22

VANDENBERG AFB, Calif. – Technicians install one half of the payload fairing over the NuSTAR spacecraft as they continue to process the spacecraft and its Pegasus rocket for launch. NuSTAR stands for Nuclear Spectroscopic Telescope Array. Photo credit: NASA/Randy Beaudoin

KSC-2012-3029

NASA Image and Video Library

2012-05-22

VANDENBERG AFB, Calif. – Technicians install the second half of the payload fairing over the NuSTAR spacecraft as they continue to process the spacecraft and its Pegasus rocket for launch. NuSTAR stands for Nuclear Spectroscopic Telescope Array. Photo credit: NASA/Randy Beaudoin

KSC-2012-3021

NASA Image and Video Library

2012-05-22

VANDENBERG AFB, Calif. – Technicians install one half of the payload fairing over the NuSTAR spacecraft as they continue to process the spacecraft and its Pegasus rocket for launch. NuSTAR stands for Nuclear Spectroscopic Telescope Array. Photo credit: NASA/Randy Beaudoin

KSC-2012-3024

NASA Image and Video Library

2012-05-22

VANDENBERG AFB, Calif. – Technicians install one half of the payload fairing over the NuSTAR spacecraft as they continue to process the spacecraft and its Pegasus rocket for launch. NuSTAR stands for Nuclear Spectroscopic Telescope Array. Photo credit: NASA/Randy Beaudoin

KSC-2012-3030

NASA Image and Video Library

2012-05-22

VANDENBERG AFB, Calif. – A technicians checks the installation of the payload fairing over the NuSTAR spacecraft as processing continues for the spacecraft and its Pegasus rocket for launch. NuSTAR stands for Nuclear Spectroscopic Telescope Array. Photo credit: NASA/Randy Beaudoin

Application of a silicon photodiode array for solar edge tracking in the Halogen Occultation Experiment

NASA Technical Reports Server (NTRS)

Mauldin, L. E., III; Moore, A. S.; Stump, C. S.; Mayo, L. S.

1985-01-01

The optical and electronic design of the Halogen Occultation Experiment (HALOE) elevation sunsensor is described. This system uses a Galilean telescope to form a solar image on a linear silicon photodiode array. The array is a self-scanned, monolithic charge coupled device. The addresses of both solar edges imaged on the array are used by the control/pointing system to scan the HALOE science instantaneous-field-of-view (IFOV) across the vertical solar diameter during instrument calibration, and then maintain the science IFOV four arcmin below the top edge during the science data occultation event. Vertical resolution of 16 arcsec and a radiometric dynamic range of 100 are achieved at the 0.7 micrometer operating wavelength. The design provides for loss of individual photodiode elements without loss of angular tracking capability. The HALOE instrument is a gas correlation radiometer that is now being developed by NASA Langley Research Center for the Upper Atmospheric Research Satellite.

A synthetic aperture microwave radiometer to measure soil moisture and ocean salinity from space

NASA Technical Reports Server (NTRS)

Le Vine, D. M.; Hilliard, L. M.; Swift, C. T.; Ruf, C. S.; Garrett, L. B.

1991-01-01

A concept is presented for a microwave radiometer in space to measure soil moisture and ocean salinity as part of an 'Earth Probe' mission. The measurements could be made using an array of stick antennas. The L-band channel (1.4 GHz) would be the primary channel for determining soil moisture, with the S-band (2.65-GHz) and C-band (5.0-GHz) channels providing ancillary information to help correct for the effects of the vegetation canopy and possibly to estimate a moisture profile. A preliminary study indicates that an orbit at 450 km would provide coverage of better than 95 percent of the earth every 3 days. A 10-km resolution cell (at nadir) requires stick antennas about 9.5-m long at L-band. The S-band and C-band sticks would be substantially shorter (5 m and 2.7 m, respectively).

Advanced microwave radiometer antenna system study

NASA Technical Reports Server (NTRS)

Kummer, W. H.; Villeneuve, A. T.; Seaton, A. F.

1976-01-01

The practicability of a multi-frequency antenna for spaceborne microwave radiometers was considered in detail. The program consisted of a comparative study of various antenna systems, both mechanically and electronically scanned, in relation to specified design goals and desired system performance. The study involved several distinct tasks: definition of candidate antennas that are lightweight and that, at the specified frequencies of 5, 10, 18, 22, and 36 GHz, can provide conical scanning, dual linear polarization, and simultaneous multiple frequency operation; examination of various feed systems and phase-shifting techniques; detailed analysis of several key performance parameters such as beam efficiency, sidelobe level, and antenna beam footprint size; and conception of an antenna/feed system that could meet the design goals. Candidate antennas examined include phased arrays, lenses, and optical reflector systems. Mechanical, electrical, and performance characteristics of the various systems were tabulated for ease of comparison.

Combined Infrared Stereo and Laser Ranging Cloud Measurements from Shuttle Mission STS-85

NASA Technical Reports Server (NTRS)

Lancaster, R. S.; Spinhirne, J. D.; Manizade, K. F.

2004-01-01

Multiangle remote sensing provides a wealth of information for earth and climate monitoring, such as the ability to measure the height of cloud tops through stereoscopic imaging. As technology advances so do the options for developing spacecraft instrumentation versatile enough to meet the demands associated with multiangle measurements. One such instrument is the infrared spectral imaging radiometer, which flew as part of mission STS-85 of the space shuttle in 1997 and was the first earth- observing radiometer to incorporate an uncooled microbolometer array detector as its image sensor. Specifically, a method for computing cloud-top height with a precision of +/- 620 m from the multispectral stereo measurements acquired during this flight has been developed, and the results are compared with coincident direct laser ranging measurements from the shuttle laser altimeter. Mission STS-85 was the first space flight to combine laser ranging and thermal IR camera systems for cloud remote sensing.

Argus: A W-band 16-pixel focal plane array for the Green Bank Telescope

NASA Astrophysics Data System (ADS)

Devaraj, Kiruthika; Church, Sarah; Cleary, Kieran; Frayer, David; Gawande, Rohit; Goldsmith, Paul; Gundersen, Joshua; Harris, Andrew; Kangaslahti, Pekka; Readhead, Tony; Reeves, Rodrigo; Samoska, Lorene; Sieth, Matt; Voll, Patricia

2015-05-01

We are building Argus, a 16-pixel square-packed focal plane array that will cover the 75-115.3 GHz frequency range on the Robert C. Byrd Green Bank Telescope (GBT). The primary research area for Argus is the study of star formation within our Galaxy and nearby galaxies. Argus will map key molecules that trace star formation, including carbon monoxide (CO) and hydrogen cyanide (HCN). An additional key science area is astrochemistry, which will be addressed by observing complex molecules in the interstellar medium, and the study of formation of solar systems, which will be addressed by identifying dense pre-stellar cores and by observing comets in our solar system. Argus has a highly scalable architecture and will be a technology path finder for larger arrays. The array is modular in construction, which will allow easy replacement of malfunctioning and poorly performing components.

The CHARA Array resolves the long-period Wolf-Rayet binaries WR 137 and WR 138

NASA Astrophysics Data System (ADS)

Richardson, Noel D.; Shenar, Tomer; Roy-Loubier, Olivier; Schaefer, Gail; Moffat, Anthony F. J.; St-Louis, Nicole; Gies, Douglas R.; Farrington, Chris; Hill, Grant M.; Williams, Peredur M.; Gordon, Kathryn; Pablo, Herbert; Ramiaramanantsoa, Tahina

2016-10-01

We report on interferometric observations with the CHARA Array of two classical Wolf-Rayet (WR) stars in suspected binary systems, namely WR 137 and WR 138. In both cases, we resolve the component stars to be separated by a few milliarcseconds. The data were collected in the H band, and provide a measure of the fractional flux for both stars in each system. We find that the WR star is the dominant H-band light source in both systems (fWR,137 = 0.59 ± 0.04; fWR,138 = 0.67 ± 0.01), which is confirmed through both comparisons with estimated fundamental parameters for WR stars and O dwarfs, as well as through spectral modelling of each system. Our spectral modelling also provides fundamental parameters for the stars and winds in these systems. The results on WR 138 provide evidence that it is a binary system which may have gone through a previous mass-transfer episode to create the WR star. The separation and position of the stars in the WR 137 system together with previous results from the IOTA interferometer provides evidence that the binary is seen nearly edge-on. The possible edge-on orbit of WR 137 aligns well with the dust production site imaged by the Hubble Space Telescope during a previous periastron passage, showing that the dust production may be concentrated in the orbital plane.

X-ray technology behind NASA's black-hole hunter (NuSTAR)

ScienceCinema

Craig, Bill

2018-05-18

Livermore Lab astrophysicist Bill Craig describes his team's role in developing X-ray imaging technology for the NASA Nuclear Spectroscopic Telescope Array (NuSTAR) mission. The black-hole-hunting spacecraft bagged its first 10 supermassive black holes this week.

X-ray technology behind NASA's black-hole hunter (NuSTAR)

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

Craig, Bill

2013-09-10

Livermore Lab astrophysicist Bill Craig describes his team's role in developing X-ray imaging technology for the NASA Nuclear Spectroscopic Telescope Array (NuSTAR) mission. The black-hole-hunting spacecraft bagged its first 10 supermassive black holes this week.

SETI Observations of Exoplanets with the Allen Telescope Array

NASA Astrophysics Data System (ADS)

Harp, G. R.; Richards, Jon; Tarter, Jill C.; Dreher, John; Jordan, Jane; Shostak, Seth; Smolek, Ken; Kilsdonk, Tom; Wilcox, Bethany R.; Wimberly, M. K. R.; Ross, John; Barott, W. C.; Ackermann, R. F.; Blair, Samantha

2016-12-01

We report radio SETI observations on a large number of known exoplanets and other nearby star systems using the Allen Telescope Array (ATA). Observations were made over about 19000 hr from 2009 May to 2015 December. This search focused on narrowband radio signals from a set totaling 9293 stars, including 2015 exoplanet stars and Kepler objects of interest and an additional 65 whose planets may be close to their habitable zones. The ATA observations were made using multiple synthesized beams and an anticoincidence filter to help identify terrestrial radio interference. Stars were observed over frequencies from 1 to 9 GHz in multiple bands that avoid strong terrestrial communication frequencies. Data were processed in near-real time for narrowband (0.7-100 Hz) continuous and pulsed signals with transmitter/receiver relative accelerations from -0.3 to 0.3 m s-2. A total of 1.9 × 108 unique signals requiring immediate follow-up were detected in observations covering more than 8 × 106 star-MHz. We detected no persistent signals from extraterrestrial technology exceeding our frequency-dependent sensitivity threshold of 180-310 × 10-26 W m-2.

Stellar Snowflake Cluster

NASA Technical Reports Server (NTRS)

2005-01-01

[figure removed for brevity, see original site] Figure 1 Stellar Snowflake Cluster Combined Image [figure removed for brevity, see original site] Figure 2 Infrared Array CameraFigure 3 Multiband Imaging Photometer

Newborn stars, hidden behind thick dust, are revealed in this image of a section of the Christmas Tree cluster from NASA's Spitzer Space Telescope, created in joint effort between Spitzer's infrared array camera and multiband imaging photometer instruments.

The newly revealed infant stars appear as pink and red specks toward the center of the combined image (fig. 1). The stars appear to have formed in regularly spaced intervals along linear structures in a configuration that resembles the spokes of a wheel or the pattern of a snowflake. Hence, astronomers have nicknamed this the 'Snowflake' cluster.

Star-forming clouds like this one are dynamic and evolving structures. Since the stars trace the straight line pattern of spokes of a wheel, scientists believe that these are newborn stars, or 'protostars.' At a mere 100,000 years old, these infant structures have yet to 'crawl' away from their location of birth. Over time, the natural drifting motions of each star will break this order, and the snowflake design will be no more.

While most of the visible-light stars that give the Christmas Tree cluster its name and triangular shape do not shine brightly in Spitzer's infrared eyes, all of the stars forming from this dusty cloud are considered part of the cluster.

Like a dusty cosmic finger pointing up to the newborn clusters, Spitzer also illuminates the optically dark and dense Cone nebula, the tip of which can be seen towards the bottom left corner of each image.

This combined image shows the presence of organic molecules mixed with dust as wisps of green, which have been illuminated by nearby star formation. The larger yellowish dots neighboring the baby red stars in the Snowflake Cluster are massive stellar infants forming from the same cloud. The blue dots sprinkled across the image represent older Milky Way stars at various distances along this line of sight. This image is a five-channel, false-color composite, showing emission from wavelengths of 3.6 and 4.5 microns (blue), 5.8 microns (cyan), 8 microns (green), and 24 microns (red).

The top right (fig. 2) image from the infrared array camera show that the nebula is still actively forming stars. The wisps of red (represented as green in the combined image) are organic molecules mixed with dust, which has been illuminated by nearby star formation. The infrared array camera picture is a four-channel, false-color composite, showing emission from wavelengths of 3.6 microns (blue), 4.5 microns (green), 5.8 microns (orange) and 8.0 microns (red).

The bottom right image (fig. 3) from the multiband imaging photometer shows the colder dust of the nebula and unwraps the youngest stellar babies from their dusty covering. This is a false-color image showing emission at 24 microns (red).

Digital solar edge tracker for the Halogen Occultation Experiment

NASA Technical Reports Server (NTRS)

Mauldin, L. E., III; Moore, A. S.; Stump, C. W.; Mayo, L. S.

1987-01-01

The optical and electronic design of the Halogen Occultation Experiment (Haloe) elevation sun sensor is described. The Haloe instrument is a gas-correlation radiometer now being developed at NASA Langley for the Upper Atmosphere Research Satellite. The system uses a Galilean telescope to form a solar image on a linear silicon photodiode array. The array is a self-scanned monolithic CCD. The addresses of both solar edges imaged on the array are used by the control/pointing system to scan the Haloe science instantaneous field of view (IFOV) across the vertical solar diameter during instrument calibration and then to maintain the science IFOV 4 arcmin below the top edge during the science data occultation event. Vertical resolution of 16 arcsec and a radiometric dynamic range of 100 are achieved at the 700-nm operating wavelength. The design provides for loss of individual photodiode elements without loss of angular tracking capability.

First detection of thermal radio emission from solar-type stars with the Karl G. Jansky very large array

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

Villadsen, Jackie; Hallinan, Gregg; Bourke, Stephen

2014-06-20

We present the first detections of thermal radio emission from the atmospheres of solar-type stars τ Cet, η Cas A, and 40 Eri A. These stars all resemble the Sun in age and level of magnetic activity, as indicated by X-ray luminosity and chromospheric emission in Ca II H and K lines. We observed these stars with the Karl G. Jansky Very Large Array with sensitivities of a few μJy at combinations of 10.0, 15.0, and 34.5 GHz. τ Cet, η Cas A, and 40 Eri A are all detected at 34.5 GHz with signal-to-noise ratios of 6.5, 5.2, andmore » 4.5, respectively. 15.0 GHz upper limits imply a rising spectral index greater than 1.0 for τ Cet and 1.6 for η Cas A, at the 95% confidence level. The measured 34.5 GHz flux densities correspond to stellar disk-averaged brightness temperatures of roughly 10,000 K, similar to the solar brightness temperature at the same frequency. We explain this emission as optically thick thermal free-free emission from the chromosphere, with possible contributions from coronal gyroresonance emission above active regions and coronal free-free emission. These and similar quality data on other nearby solar-type stars, when combined with Atacama Large Millimeter/Submillimeter Array observations, will enable the construction of temperature profiles of their chromospheres and lower transition regions.« less

Advanced Passive Microwave Radiometer Technology for GPM Mission

NASA Technical Reports Server (NTRS)

Smith, Eric A.; Im, Eastwood; Kummerow, Christian; Principe, Caleb; Ruf, Christoper; Wilheit, Thomas; Starr, David (Technical Monitor)

2002-01-01

An interferometer-type passive microwave radiometer based on MMIC receiver technology and a thinned array antenna design is being developed under the Instrument Incubator Program (TIP) on a project entitled the Lightweight Rainfall Radiometer (LRR). The prototype single channel aircraft instrument will be ready for first testing in 2nd quarter 2003, for deployment on the NASA DC-8 aircraft and in a ground configuration manner; this version measures at 10.7 GHz in a crosstrack imaging mode. The design for a two (2) frequency preliminary space flight model at 19 and 35 GHz (also in crosstrack imaging mode) has also been completed, in which the design features would enable it to fly in a bore-sighted configuration with a new dual-frequency space radar (DPR) under development at the Communications Research Laboratory (CRL) in Tokyo, Japan. The DPR will be flown as one of two primary instruments on the Global Precipitation Measurement (GPM) mission's core satellite in the 2007 time frame. The dual frequency space flight design of the ERR matches the APR frequencies and will be proposed as an ancillary instrument on the GPM core satellite to advance space-based precipitation measurement by enabling better microphysical characterization and coincident volume data gathering for exercising combined algorithm techniques which make use of both radar backscatter and radiometer attenuation information to constrain rainrate solutions within a physical algorithm context. This talk will discuss the design features, performance capabilities, applications plans, and conical/polarametric imaging possibilities for the LRR, as well as a brief summary of the project status and schedule.

System for star catalog equalization to enhance attitude determination

NASA Technical Reports Server (NTRS)

Liu, Yong (Inventor); Wu, Yeong-Wei Andy (Inventor); Li, Rongsheng (Inventor)

2001-01-01

An apparatus for star catalog equalization to enhance attitude determination includes a star tracker, a star catalog and a controller. The star tracker is used to sense the positions of stars and generate signals corresponding to the positions of the stars as seen in its field of view. The star catalog contains star location data that is stored using a primary and multiple secondary arrays sorted by both declination (DEC) and right ascension (RA), respectively. The star location data stored in the star catalog is predetermined by calculating a plurality of desired star locations, associating one of a plurality of stars with each of the plurality of desired star locations based upon a neighborhood association angle to generate an associated plurality of star locations: If an artificial star gap occurs during association, then the neighborhood association angle for reassociation is increased. The controller uses the star catalog to determine which stars to select to provide star measurement residuals for correcting gyroscope bias and spacecraft attitude.

Detecting signatures of cosmological recombination and reionization in the cosmic radio background

NASA Astrophysics Data System (ADS)

Subrahmanyan, Ravi; Shankar Narayana Rao, Udaya; Sathyanarayana Rao, Mayuri; Singh, Saurabh

2015-08-01

Evolution of the baryons during the Epochs of cosmological Recombination and Reionization has left traces in the cosmic radio background in the form of spectral distortions (Sunyaev & Chluba 2008 Astron. Nachrichten, 330, 657; Pritchard & Loeb 2012 Rep Prog Phys 75(8):086901). The spectral signature depends on the evolution in the ionization state in hydrogen and helium and on the spin temperature of hydrogen. These probe the physics of energy release beyond the last scattering surface at redshifts exceeding 1090 and the nature of the first sources and gas evolution down to redshift about 6. The spectral distortions are sensitive to the nature of the first stars, ultra-dwarf galaxies, accreting compact objects, and the evolving ambient radiation field: X-rays and UV from the first sources. Detection of the all-sky or global spectral distortions in the radio background is hence a probe of cosmological recombination and reionization.We present new spectral radiometers that we have purpose designed for precision measurements of spectral distortions at radio wavelengths. New antenna elements include frequency independent and electrically small fat-dipole (Raghunathan et al. 2013 IEEE TAP, 61, 3411) and monopole designs. Receiver configurations have been devised that are self-calibratable (Patra et al. 2013 Expt Astron, 36, 319) so that switching of signal paths and of calibration noise sources provide real time calibration for systematics and receiver noise. Observing strategies (Patra et al. arXiv:1412.7762) and analysis methods (Satyanarayana Rao et al. arXiv:1501.07191) have been evolved that are capable of discriminating between the cosmological signals and the substantially brighter foregrounds. We have also demonstrated the value of system designs that exploit advantages of interferometer detection (Mahesh et al. arXiv:1406.2585) of global spectral distortions.Finally we discuss how the Square Kilometer Array stations may be outfitted with precision spectral radiometer outriggers (Subrahmanyan et al. arXiv:1501.04340) to provide the zero-spacing measurement sets, complement the interferometer visibilities and give the SKA a capability for measurements of cosmic radio background spectral distortions.

SPICA, Stellar Parameters and Images with a Cophased Array: a 6T visible combiner for the CHARA array.

PubMed

Mourard, Denis; Bério, Philippe; Perraut, Karine; Clausse, Jean-Michel; Creevey, Orlagh; Martinod, Marc-Antoine; Meilland, Anthony; Millour, Florentin; Nardetto, Nicolas

2017-05-01

High angular resolution studies of stars in the optical domain have highly progressed in recent years. After the results obtained with the visible instrument Visible spEctroGraph and polArimeter (VEGA) on the Center for High Angular Resolution Astronomy (CHARA) array and the recent developments on adaptive optics and fibered interferometry, we have started the design and study of a new six-telescope visible combiner with single-mode fibers. It is designed as a low spectral resolution instrument for the measurement of the angular diameter of stars to make a major step forward in terms of magnitude and precision with respect to the present situation. For a large sample of bright stars, a medium spectral resolution mode will allow unprecedented spectral imaging of stellar surfaces and environments for higher accuracy on stellar/planetary parameters. To reach the ultimate performance of the instrument in terms of limiting magnitude (Rmag≃8 for diameter measurements and Rmag≃4 to 5 for imaging), Stellar Parameters and Images with a Cophased Array (SPICA) includes the development of a dedicated fringe tracking system in the H band to reach "long" (200 ms to 30 s) exposures of the fringe signal in the visible.

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.

Signatures of Young Star Formation Activity within Two Parsecs of Sgr A*

NASA Astrophysics Data System (ADS)

Yusef-Zadeh, F.; Wardle, M.; Sewilo, M.; Roberts, D. A.; Smith, I.; Arendt, R.; Cotton, W.; Lacy, J.; Martin, S.; Pound, M. W.; Rickert, M.; Royster, M.

2015-07-01

We present radio and infrared observations indicating ongoing star formation activity inside the ˜2-5 pc circumnuclear ring at the Galactic center. Collectively these measurements suggest a continued disk-based mode of ongoing star formation has taken place near Sgr A* over the last few million years. First, Very Large Array observations with spatial resolution 2.″17 × 0.″81 reveal 13 water masers, several of which have multiple velocity components. The presence of interstellar water masers suggests gas densities that are sufficient for self-gravity to overcome the tidal shear of the 4× {10}6 {M}⊙ black hole. Second, spectral energy distribution modeling of stellar sources indicates massive young stellar object (YSO) candidates interior to the molecular ring, supporting in situ star formation near Sgr A* and appear to show a distribution similar to that of the counter-rotating disks of ˜100 OB stars orbiting Sgr A*. Some YSO candidates (e.g., IRS 5) have bow shock structures, suggesting that they have gaseous disks that are phototoevaporated and photoionized by the strong radiation field. Third, we detect clumps of SiO (2-1) and (5-4) line emission in the ring based on Combined Array for Research in Millimeter-wave Astronomy and Sub-Millimeter Array observations. The FWHM and luminosity of the SiO emission is consistent with shocked protostellar outflows. Fourth, two linear ionized features with an extent of ˜0.8 pc show blue and redshifted velocities between +50 and -40 km s-1, suggesting protostellar jet driven outflows with mass-loss rates of ˜ 5× {10}-5 {M}⊙ yr-1. Finally, we present the imprint of radio dark clouds at 44 GHz, representing a reservoir of molecular gas that feeds star formation activity close to Sgr A*.

High Precision Sunphotometer using Wide Dynamic Range (WDR) Camera Tracking

NASA Astrophysics Data System (ADS)

Liss, J.; Dunagan, S. E.; Johnson, R. R.; Chang, C. S.; LeBlanc, S. E.; Shinozuka, Y.; Redemann, J.; Flynn, C. J.; Segal-Rosenhaimer, M.; Pistone, K.; Kacenelenbogen, M. S.; Fahey, L.

2016-12-01

High Precision Sunphotometer using Wide Dynamic Range (WDR) Camera TrackingThe NASA Ames Sun-photometer-Satellite Group, DOE, PNNL Atmospheric Sciences and Global Change Division, and NASA Goddard's AERONET (AErosol RObotic NETwork) team recently collaborated on the development of a new airborne sunphotometry instrument that provides information on gases and aerosols extending far beyond what can be derived from discrete-channel direct-beam measurements, while preserving or enhancing many of the desirable AATS features (e.g., compactness, versatility, automation, reliability). The enhanced instrument combines the sun-tracking ability of the current 14-Channel NASA Ames AATS-14 with the sky-scanning ability of the ground-based AERONET Sun/sky photometers, while extending both AATS-14 and AERONET capabilities by providing full spectral information from the UV (350 nm) to the SWIR (1,700 nm). Strengths of this measurement approach include many more wavelengths (isolated from gas absorption features) that may be used to characterize aerosols and detailed (oversampled) measurements of the absorption features of specific gas constituents. The Sky Scanning Sun Tracking Airborne Radiometer (3STAR) replicates the radiometer functionality of the AATS-14 instrument but incorporates modern COTS technologies for all instruments subsystems. A 19-channel radiometer bundle design is borrowed from a commercial water column radiance instrument manufactured by Biospherical Instruments of San Diego California (ref, Morrow and Hooker)) and developed using NASA funds under the Small Business Innovative Research (SBIR) program. The 3STAR design also incorporates the latest in robotic motor technology embodied in Rotary actuators from Oriental motor Corp. having better than 15 arc seconds of positioning accuracy. Control system was designed, tested and simulated using a Hybrid-Dynamical modeling methodology. The design also replaces the classic quadrant detector tracking sensor with a wide dynamic range camera that provides a high precision solar position tracking signal as well as an image of the sky in the 45° field of view around the solar axis, which can be of great assistance in flagging data for cloud effects or other factors that might impact data quality.

Automatic Telescope Search for Extrasolar Planets

NASA Technical Reports Server (NTRS)

Henry, Gregory W.

1998-01-01

We are using automatic photoelectric telescopes at the Tennessee State University Center for Automated Space Science to search for planets around nearby stars in our galaxy. Over the past several years, wc have developed the capability to make extremely precise measurements of brightness changes in Sun-like stars with automatic telescopes. Extensive quality control and calibration measurements result in a precision of 0.l% for a single nightly observation and 0.0270 for yearly means, far better than previously thought possible with ground-based observations. We are able, for the first time, to trace brightness changes in Sun-like stars that are of similar amplitude to brightness changes in the Sun, whose changes can be observed only with space-based radiometers. Recently exciting discoveries of the first extrasolar planets have been announced, based on the detection of very small radial-velocity variations that imply the existence of planets in orbit around several Sun-like stars. Our precise brightness measurements have been crucial for the confirmation of these discoveries by helping to eliminate alternative explanations for the radial-velocity variations. With our automatic telescopes, we are also searching for transits of these planets across the disks of their stars in order to conclusively verify their existence. The detection of transits would provide the first direct measurements of the sizes, masses, and densities of these planets and, hence, information on their compositions and origins.

Microwave radiometry for non-invasive detection of vesicoureteral reflux (VUR) following bladder warming

NASA Astrophysics Data System (ADS)

Stauffer, Paul R.; Maccarini, Paolo F.; Arunachalam, Kavitha; De Luca, Valeria; Salahi, Sara; Boico, Alina; Klemetsen, Oystein; Birkelund, Yngve; Jacobsen, Svein K.; Bardati, Fernando; Tognolotti, Piero; Snow, Brent

2011-03-01

Background: Vesicoureteral reflux (VUR) is a serious health problem leading to renal scarring in children. Current VUR detection involves traumatic x-ray imaging of kidneys following injection of contrast agent into bladder via invasive Foley catheter. We present an alternative non-invasive approach for detecting VUR by radiometric monitoring of kidney temperature while gently warming the bladder. Methods: We report the design and testing of: i) 915MHz square slot antenna array for heating bladder, ii) EMI-shielded log spiral microstrip receive antenna, iii) high-sensitivity 1.375GHz total power radiometer, iv) power modulation approach to increase urine temperature relative to overlying perfused tissues, and v) invivo porcine experiments characterizing bladder heating and radiometric temperature of aaline filled 30mL balloon "kidney" implanted 3-4cm deep in thorax and varied 2-6°C from core temperature. Results: SAR distributions are presented for two novel antennas designed to heat bladder and monitor deep kidney temperatures radiometrically. We demonstrate the ability to heat 180mL saline in in vivo porcine bladder to 40-44°C while maintaining overlying tissues <38°C using time-modulated square slot antennas coupled to the abdomen with room temperature water pad. Pathologic evaluations confirmed lack of acute thermal damage in pelvic tissues for up to three 20min bladder heat exposures. The radiometer clearly recorded 2-6°C changes of 30mL "kidney" targets at depth in 34°C invivo pig thorax. Conclusion: A 915MHz antenna array can gently warm in vivo pig bladder without toxicity while a 1.375GHz radiometer with log spiral receive antenna detects >=2°C rise in 30mL "urine" located 3-4cm deep in thorax, demonstrating more than sufficient sensitivity to detect Grade 4-5 reflux of warmed urine for non-invasive detection of VUR.

Microwave Radiometry for Non-Invasive Detection of Vesicoureteral Reflux (VUR) Following Bladder Warming.

PubMed

Stauffer, Paul R; Maccarini, Paolo F; Arunachalam, Kavitha; De Luca, Valeria; Salahi, Sara; Boico, Alina; Klemetsen, Oystein; Birkelund, Yngve; Jacobsen, Svein K; Bardati, Fernando; Tognolatti, Piero; Snow, Brent

2011-01-01

BACKGROUND: Vesicoureteral reflux (VUR) is a serious health problem leading to renal scarring in children. Current VUR detection involves traumatic x-ray imaging of kidneys following injection of contrast agent into bladder via invasive Foley catheter. We present an alternative non-invasive approach for detecting VUR by radiometric monitoring of kidney temperature while gently warming the bladder. METHODS: We report the design and testing of: i) 915MHz square slot antenna array for heating bladder, ii) EMI-shielded log spiral microstrip receive antenna, iii) high-sensitivity 1.375GHz total power radiometer, iv) power modulation approach to increase urine temperature relative to overlying perfused tissues, and v) invivo porcine experiments characterizing bladder heating and radiometric temperature of aaline filled 30mL balloon "kidney" implanted 3-4cm deep in thorax and varied 2-6°C from core temperature. RESULTS: SAR distributions are presented for two novel antennas designed to heat bladder and monitor deep kidney temperatures radiometrically. We demonstrate the ability to heat 180mL saline in in vivo porcine bladder to 40-44°C while maintaining overlying tissues <38°C using time-modulated square slot antennas coupled to the abdomen with room temperature water pad. Pathologic evaluations confirmed lack of acute thermal damage in pelvic tissues for up to three 20min bladder heat exposures. The radiometer clearly recorded 2-6°C changes of 30mL "kidney" targets at depth in 34°C invivo pig thorax. CONCLUSION: A 915MHz antenna array can gently warm in vivo pig bladder without toxicity while a 1.375GHz radiometer with log spiral receive antenna detects ≥2°C rise in 30mL "urine" located 3-4cm deep in thorax, demonstrating more than sufficient sensitivity to detect Grade 4-5 reflux of warmed urine for non-invasive detection of VUR.

Polar microwave brightness temperatures from Nimbus-7 SMMR: Time series of daily and monthly maps from 1978 to 1987

NASA Technical Reports Server (NTRS)

Comiso, Josefino C.; Zwally, H. Jay

1989-01-01

A time series of daily brightness temperature gridded maps (October 25, 1978 through August 15, 1987) were generated from all ten channels of the Nimbus-7 Scanning Multichannel Microwave Radiometer orbital data. This unique data set can be utilized in a wide range of applications including heat flux, ocean circulation, ice edge productivity, and climate studies. Two sets of data in polar stereographic format are created for the Arctic region: one with a grid size of about 30 km on a 293 by 293 array similar to that previously utilized for the Nimbus-5 Electrically Scanning Microwave Radiometer, while the other has a grid size of about 25 km on a 448 by 304 array identical to what is now being used for the DMSP Scanning Multichannel Microwave Imager. Data generated for the Antaractic region are mapped using the 293 by 293 grid only. The general technique for mapping, and a quality assessment of the data set are presented. Monthly and yearly averages are also generated from the daily data and sample geophysical ice images and products derived from the data are given. Contour plots of monthly ice concentrations derived from the data for October 1978 through August 1987 are presented to demonstrate spatial and temporal detail which this data set can offer, and to show potential research applications.

Progress in the Phase 0 Model Development of a STAR Concept for Dynamics and Control Testing

NASA Technical Reports Server (NTRS)

Woods-Vedeler, Jessica A.; Armand, Sasan C.

2003-01-01

The paper describes progress in the development of a lightweight, deployable passive Synthetic Thinned Aperture Radiometer (STAR). The spacecraft concept presented will enable the realization of 10 km resolution global soil moisture and ocean salinity measurements at 1.41 GHz. The focus of this work was on definition of an approximately 1/3-scaled, 5-meter Phase 0 test article for concept demonstration and dynamics and control testing. Design requirements, parameters and a multi-parameter, hybrid scaling approach for the dynamically scaled test model were established. The El Scaling Approach that was established allows designers freedom to define the cross section of scaled, lightweight structural components that is most convenient for manufacturing when the mass of the component is small compared to the overall system mass. Static and dynamic response analysis was conducted on analytical models to evaluate system level performance and to optimize panel geometry for optimal tension load distribution.

All-optical LAN architectures based on arrayed waveguide grating multiplexers

NASA Astrophysics Data System (ADS)

Woesner, Hagen

1998-10-01

The paper presents optical LAN topologies which are made possible using an Arrayed Waveguide Grating Multiplexer (AWGM) instead of a passive star coupler to interconnect stations in an all-optical LAN. Due to the collision-free nature of an AWGM it offers the n-fold bandwidth compared to the star coupler. Virtual ring topologies appear (one ring on each wavelength) if the number of stations attached to the AWGM is a prime number. A method to construct larger networks using Cayley graphs is shown. An access protocol to avoid collisions on the proposed network is outlined.

The signature of the first stars in atomic hydrogen at redshift 20.

PubMed

Visbal, Eli; Barkana, Rennan; Fialkov, Anastasia; Tseliakhovich, Dmitriy; Hirata, Christopher M

2012-07-05

Dark and baryonic matter moved at different velocities in the early Universe, which strongly suppressed star formation in some regions. This was estimated to imprint a large-scale fluctuation signal of about two millikelvin in the 21-centimetre spectral line of atomic hydrogen associated with stars at a redshift of 20, although this estimate ignored the critical contribution of gas heating due to X-rays and major enhancements of the suppression. A large velocity difference reduces the abundance of haloes and requires the first stars to form in haloes of about a million solar masses, substantially greater than previously expected. Here we report a simulation of the distribution of the first stars at redshift 20 (cosmic age of around 180 million years), incorporating all these ingredients within a 400-megaparsec box. We find that the 21-centimetre hydrogen signature of these stars is an enhanced (ten millikelvin) fluctuation signal on the hundred-megaparsec scale, characterized by a flat power spectrum with prominent baryon acoustic oscillations. The required sensitivity to see this signal is achievable with an integration time of a thousand hours with an instrument like the Murchison Wide-field Array or the Low Frequency Array but designed to operate in the range of 50-100 megahertz.

Embedded binaries and their dense cores

NASA Astrophysics Data System (ADS)

Sadavoy, Sarah I.; Stahler, Steven W.

2017-08-01

We explore the relationship between young, embedded binaries and their parent cores, using observations within the Perseus Molecular Cloud. We combine recently published Very Large Array observations of young stars with core properties obtained from Submillimetre Common-User Bolometer Array 2 observations at 850 μm. Most embedded binary systems are found towards the centres of their parent cores, although several systems have components closer to the core edge. Wide binaries, defined as those systems with physical separations greater than 500 au, show a tendency to be aligned with the long axes of their parent cores, whereas tight binaries show no preferred orientation. We test a number of simple, evolutionary models to account for the observed populations of Class 0 and I sources, both single and binary. In the model that best explains the observations, all stars form initially as wide binaries. These binaries either break up into separate stars or else shrink into tighter orbits. Under the assumption that both stars remain embedded following binary break-up, we find a total star formation rate of 168 Myr-1. Alternatively, one star may be ejected from the dense core due to binary break-up. This latter assumption results in a star formation rate of 247 Myr-1. Both production rates are in satisfactory agreement with current estimates from other studies of Perseus. Future observations should be able to distinguish between these two possibilities. If our model continues to provide a good fit to other star-forming regions, then the mass fraction of dense cores that becomes stars is double what is currently believed.

The Gould's Belt Very Large Array Survey. IV. The Taurus-Auriga Complex

NASA Astrophysics Data System (ADS)

Dzib, Sergio A.; Loinard, Laurent; Rodríguez, Luis F.; Mioduszewski, Amy J.; Ortiz-León, Gisela N.; Kounkel, Marina A.; Pech, Gerardo; Rivera, Juana L.; Torres, Rosa M.; Boden, Andrew F.; Hartmann, Lee; Evans, Neal J., II; Briceño, Cesar; Tobin, John

2015-03-01

We present a multi-epoch radio study of the Taurus-Auriga star-forming complex made with the Karl G. Jansky Very Large Array at frequencies of 4.5 GHz and 7.5 GHz. We detect a total of 610 sources, 59 of which are related to young stellar objects (YSOs) and 18 to field stars. The properties of 56% of the young stars are compatible with non-thermal radio emission. We also show that the radio emission of more evolved YSOs tends to be more non-thermal in origin and, in general, that their radio properties are compatible with those found in other star-forming regions. By comparing our results with previously reported X-ray observations, we notice that YSOs in Taurus-Auriga follow a Güdel-Benz relation with κ = 0.03, as we previously suggested for other regions of star formation. In general, YSOs in Taurus-Auriga and in all the previous studied regions seem to follow this relation with a dispersion of ~1 dex. Finally, we propose that most of the remaining sources are related with extragalactic objects but provide a list of 46 unidentified radio sources whose radio properties are compatible with a YSO nature.

KSC-2012-3025

NASA Image and Video Library

2012-05-22

VANDENBERG AFB, Calif. – Technicians install one half of the payload fairing over the NuSTAR spacecraft as they continue to process the spacecraft and its Pegasus rocket for launch. The second half of the fairing stands ready for installation. NuSTAR stands for Nuclear Spectroscopic Telescope Array. Photo credit: NASA/Randy Beaudoin

NuSTAR Seeks Hidden Black Holes

NASA Image and Video Library

2015-07-06

Top: An illustration of NASA's Nuclear Spectroscopic Telescope Array, or NuSTAR, in orbit. The unique school bus-long mast allows NuSTAR to focus high energy X-rays. Lower-left: A color image from NASA's Hubble Space Telescope of one of the nine galaxies targeted by NuSTAR in search of hidden black holes. Bottom-right: An artist's illustration of a supermassive black hole, actively feasting on its surroundings. The central black hole is hidden from direct view by a thick layer of encircling gas and dust. http://photojournal.jpl.nasa.gov/catalog/PIA19348

Calibration and Use of Clutter Data for Simulation.

DTIC Science & Technology

1985-01-01

radiance surrounded by borders of un- known, nonuniform radiance (Fig. 11). Since the telescopes lie above and below the radiometer’s centerline, the...illuminated solely by the nonuniform borders of the images (Fig. 11). (In Fig. l Ithe detectors are num- bered as they have been since Montauk Point. Prior to...L C LiL F-) 0- W /4- F- 00. L- IL x / -- C:.) < > Ca- < Il / 00 LOi Cl) -00 -. Cl) 41 MONTAUK MIDWAVE DETECTOR-ARRAY NONUNIFORM BOTTOM BORDER 161

Thermal Modeling and Performance Measurements of Radiometric Arrays for Near Space Propulsion

DTIC Science & Technology

2012-07-16

radiometer vane dimensions for maximum force production. Square vanes with an edge thickness of 1.57 mm and thickness of 0.5 mm were modeled as aerogel ...materials evaluated include aerogel , Teflon, silicon dioxide, type 304 stainless steel, aluminum, and pure copper (thermal conductivity = 0.017, 0.25...front face 0.5 1 0.1 Absorptivity of aerogel 0.1 0.5 0.1 Convection coefficient across vanes (W/m^2*K) 5 40 5 Vane thickness (mm) 0.5 2 0.25

Wideband Instrument for Snow Measurements (WISM)

NASA Technical Reports Server (NTRS)

Miranda, Felix A.

2015-01-01

This presentation provides a brief summary of the utility of a wideband active and passive (radar and radiometer, respectively) instrument (8-40 GHz) to support the snow science community. The effort seeks to improve snow measurements through advanced calibration and expanded frequency of active and passive sensors and to demonstrate their science utility through airborne retrievals of snow water equivalent (SWE). In addition the effort seeks to advance the technology readiness of broadband current sheet array (CSA) antenna technology for spaceflight applications.

The SiO Masers of TX Camelopardalis

NASA Astrophysics Data System (ADS)

Marvel, Kevin B.; Diamond, P.; Kemball, A.

2001-06-01

Observations of evolved stars with the Very Long Baseline Array have shown that silicon monoxide masers are found just above the photospheres of these interesting objects. By observing many times over a few pulsation periods, researchers are now discovering complex motions in the extended photospheres of these bloated, old stars. We will present several dramatic "movies" of these sources and speculate on wat such observations can tell us about the physical conditions near the star.

The Navy Precision Optical Interferometer: an update

NASA Astrophysics Data System (ADS)

Armstrong, J. T.; Baines, Ellyn K.; Schmitt, Henrique R.; Restaino, Sergio R.; Clark, James H.; Benson, James A.; Hutter, Donald J.; Zavala, Robert T.; van Belle, Gerard T.

2016-08-01

We describe the current status of the Navy Precision Optical Interferometer (NPOI), including developments since the last SPIE meeting. The NPOI group has added stations as far as 250m from the array center and added numerous infrastructure improvements. Science programs include stellar diameters and limb darkening, binary orbits, Be star disks, exoplanet host stars, and progress toward high-resolution stellar surface imaging. Technical and infrastructure projects include on-sky demonstrations of baseline bootstrapping with six array elements and of the VISION beam combiner, control system updates, integration of the long delay lines, and updated firmware for the Classic beam combiner. Our plans to add up to four 1.8 m telescopes are no longer viable, but we have recently acquired separate funding for adding three 1 m AO-equipped telescopes and an infrared beam combiner to the array.

4STAR Sky-Scanning Retrievals of Aerosol Intensive Optical Properties from Multiple Field Campaigns with Detailed Comparisons of SSA Reported During SEAC4RS

NASA Technical Reports Server (NTRS)

Flynn, Connor; Dahlgren, R. P.; Dunagan, S.; Johnson, R.; Kacenelenbogen, M.; LeBlanc, S.; Livingston, J.; Redemann, J.; Schmid, B.; Segal Rozenhaimer, M.;

Ultra-Stable Spectrometer for Sky-Scanning, Sun-Tracking Atmospheric Research (5STAR)

NASA Technical Reports Server (NTRS)

Dunagan, Stephen E.; Johnson, Roy R.; Redemann, Jens; Holben, Brent N.; Schmidt, Beat; Flynn, Connor Joseph; Fahey, Lauren; LeBlanc, Samuel; Liss, Jordan; Kacenelenbogen, Meloe S.;

A survey of ATL-compatible radiometer antennas

NASA Technical Reports Server (NTRS)

Love, A. W.

1975-01-01

A survey was made of antennas suitable for remote sensing of the earth's surface, in particular the world ocean, by means of microwave radiometers operating in the 1 to 26 GHz frequency region and carried on board the shuttle-launched advanced technology laboratory. Array antennas are found to be unattractive and unsuited to the task. Reflectors, including Cassegrain and offset types, as well as horn-reflectors are possible candidates but all have shortcomings which impair the accuracy of measurement. Horns of the corrugated type have excellent electrical characteristics. Although they are physically very large and will require development of suitable deployment mechanisms, they appear to be valid candidates for the task. The evolution of the periscope antenna is outlined, and it is shown to possess nearly ideal electrical characteristics for the intended application. Its only shortcoming is that the feed horn creates aperture blocking; there is no blocking due to struts or any other source. The periscope antenna is recommended for ATL radiometry.

Real-time millimeter-wave imaging radiometer for avionic synthetic vision

NASA Astrophysics Data System (ADS)

Lovberg, John A.; Chou, Ri-Chee; Martin, Christopher A.

1994-07-01

ThermoTrex Corporation (TTC) has developed an imaging radiometer, the passive microwave camera (PMC), that uses an array of frequency-scanned antennas coupled to a multi-channel acousto-optic (Bragg cell) spectrum analyzer to form visible images of a scene through acquisition of thermal blackbody radiation in the millimeter-wave spectrum. The output of the Bragg cell is imaged by a standard video camera and passed to a computer for normalization and display at real-time frame rates. One application of this system could be its incorporation into an enhanced vision system to provide pilots with a clear view of the runway during fog and other adverse weather conditions. The unique PMC system architecture will allow compact large-aperture implementations because of its flat antenna sensor. Other potential applications include air traffic control, all-weather area surveillance, fire detection, and security. This paper describes the architecture of the TTC PMC and shows examples of images acquired with the system.

Combined Infrared Stereo and Laser Ranging Cloud Measurements from Shuttle Mission STS-85

NASA Technical Reports Server (NTRS)

Lancaster, Redgie S.; Spinhirne, James D.; OCStarr, David (Technical Monitor)

2001-01-01

Multi-angle remote sensing provides a wealth of information for earth and climate monitoring. And, as technology advances so do the options for developing instrumentation versatile enough to meet the demands associated with these types of measurements. In the current work, the multiangle measurement capability of the Infrared Spectral Imaging Radiometer is demonstrated. This instrument flew as part of mission STS-85 of the space shuttle Columbia in 1997 and was the first earth-observing radiometer to incorporate an uncooled microbolometer array detector as its image sensor. Specifically, a method for computing cloud-top height from the multi-spectral stereo measurements acquired during this flight has been developed and the results demonstrate that a vertical precision of 10.6 km was achieved. Further, the accuracy of these measurements is confirmed by comparison with coincident direct laser ranging measurements from the Shuttle Laser Altimeter. Mission STS-85 was the first space flight to combine laser ranging and thermal IR camera systems for cloud remote sensing.

Radio detection of extensive air showers at the Pierre Auger Observatory

NASA Astrophysics Data System (ADS)

Berat, C.

2013-08-01

The Pierre Auger Observatory explores the potential of radio-detection techniques to measure extensive air showers (EAS) induced by ultra-high energy cosmic rays. To study in detail the mechanisms responsible for radio emission in the MHz range, the Auger Engineering Radio Array has been installed at the Observatory. Presently consisting of 24 radio-detection stations, this number will grow to 150 units covering an area of almost 20 km2. Novel detection techniques based on the GHz emission from the EAS are currently being studied. AMBER (Air-shower Microwave Bremsstrahlung Experimental Radiometer) and MIDAS (Microwave Detection of Air Showers) are prototypes for a large imaging dish antenna. In EASIER (Extensive Air Shower Identification using Electron Radiometer), the microwave emission is detected by antenna horns located on each surface detector. MIDAS is a self-triggering system while AMBER and EASIER use the trigger from the Auger detectors to record the emission. The status of these radio-detection R&D efforts at the Pierre Auger Observatory will be reported.

Remote Sensing of Smoke, Land and Clouds from the NASA ER-2 during SAFARI 2000

NASA Technical Reports Server (NTRS)

King, Michael D.; Platnick, Steven; Moeller, Christopher C.; Revercomb, Henry E.; Chu, D. Allen

2002-01-01

The NASA ER-2 aircraft was deployed to southern Africa between August 17 and September 25, 2000 as part of the Southern Africa Regional Science Initiative (SAFARI) 2000. This aircraft carried a sophisticated array of multispectral scanners, multiangle spectroradiometers, a monostatic lidar, a gas correlation radiometer, upward and downward spectral flux radiometers, and two metric mapping cameras. These observations were obtained over a 3200 x 2800 km region of savanna, woody savanna, open shrubland, and grassland ecosystems throughout southern Africa, and were quite often coordinated with overflights by NASA's Terra and Landsat 7 satellites. The primary purpose of this sophisticated high altitude observing platform was to obtain independent observations of smoke, clouds, and land surfaces that could be used to check the validity of various remote sensing measurements derived by Earth-orbiting satellites. These include such things as the accuracy of the Moderate Resolution Imaging Spectro-radiometer (MODIS) cloud mask for distinguishing clouds and heavy aerosol from land and ocean surfaces, and Terra analyses of cloud optical and micro-physical properties, aerosol properties, leaf area index, vegetation index, fire occurrence, carbon monoxide, and surface radiation budget. In addition to coordination with Terra and Landsat 7 satellites, numerous flights were conducted over surface AERONET sites, flux towers in South Africa, Botswana, and Zambia, and in situ aircraft from the University of Washington, South Africa, and the United Kingdom.

Earth survey applications division: Research leading to the effective use of space technology in applications relating to the Earth's surface and interior

NASA Technical Reports Server (NTRS)

Carpenter, L. (Editor)

1980-01-01

Accomplishments and future plans are described for the following areas: (1) geology - geobotanical indicators and geopotential data; (2) modeling magnetic fields; (3) modeling the structure, composition, and evolution of the Earth's crust; (4) global and regional motions of the Earth's crust and earthquake occurrence; (5) modeling geopotential from satellite tracking data; (6) modeling the Earth's gravity field; (7) global Earth dynamics; (8) sea surface topography, ocean dynamics; and geophysical interpretation; (9) land cover and land use; (10) physical and remote sensing attributes important in detecting, measuring, and monitoring agricultural crops; (11) prelaunch studies using LANDSAT D; (12) the multispectral linear array; (13) the aircraft linear array pushbroom radiometer; and (14) the spaceborne laser ranging system.

The Intricate Role of Cold Gas and Dust in Galaxy Evolution at Early Cosmic Epochs

NASA Astrophysics Data System (ADS)

Riechers, Dominik A.; Capak, Peter L.; Carilli, Christopher L.

Cold molecular and atomic gas plays a central role in our understanding of early galaxy formation and evolution. It represents the component of the interstellar medium (ISM) that stars form out of, and its mass, distribution, excitation, and dynamics provide crucial insight into the physical processes that support the ongoing star formation and stellar mass buildup. We here present results that demonstrate the capability of the Atacama Large (sub-)Millimeter Array (ALMA) to detect the cold ISM and dust in ``normal'' galaxies at redshifts z=5-6. We also show detailed studies of the ISM in massive, dust-obscured starburst galaxies out to z>6 with ALMA, the Combined Array for Research in Millimeter-wave Astronomy (CARMA), the Plateau de Bure Interferometer (PdBI), and the Karl G. Jansky Very Large Array (VLA). These observations place some of the most direct constraints on the dust-obscured fraction of the star formation history of the universe at z>5 to date, showing that ``typical'' galaxies at these epochs have low dust content, but also that highly-enriched, dusty starbursts already exist within the first billion years after the Big Bang.

Lenslet Array to Further Suppress Star Light for Direct Exoplanet Detection

NASA Technical Reports Server (NTRS)

Gong, Qian; McElwain, Michael; Shiri, Ron

2016-01-01

Direct imaging plays a key role in the detection and characterization of exoplanets orbiting within its host star's habitable zone. Many innovative ideas for starlight suppression and wavefront control have been proposed and developed over the past decade. However, several technological challenges still lie ahead to achieve the required contrast, including controlling the observatory pointing performance, fabricating occulting masks with tight optical tolerances, developing wavefront control algorithms, controlling stray light, advancing single photon detecting detectors, and integrated system-level issues. This paper explores how a lenslet array and pinhole mask may be implemented to further suppress uncorrected starlight that leaks through the occulting mask. An external occulter, or star shade, is simulated to demonstrate this concept, although this approach can be implemented for internal coronagraphs as well. We describe how to use simple relay optics to control the scene near the inner working angle and the level of the suppression expected. Furthermore, if the lenslet array is the input to an integral field spectrograph, as planned for the WFIRST mission, the spectral content of the exoplanet atmospheres can be obtained to determine if the observed planet is habitable and ultimately, if it is inhabited.

CMZoom: The Submillimeter Array Survey of our Galaxy’s Central Molecular Zone

NASA Astrophysics Data System (ADS)

Battersby, Cara; CMZoom Team

2018-01-01

The inner few hundred parsecs of the Milky Way, the Central Molecular Zone (CMZ), is our closest laboratory for understanding star formation in the extreme environments (hot, dense, turbulent gas) that once dominated the universe. We present an update on the first large-area survey to expose the sites of star formation across the CMZ at high-resolution in submillimeter wavelengths: the CMZoom survey with the Submillimeter Array (SMA). We identify the locations of dense cores and search for signatures of embedded star formation. CMZoom is a three-year survey, completed this year, and has mapped out the highest column density regions of the CMZ in dust continuum and a variety of spectral lines around 1.3 mm. CMZoom combines SMA compact and subcompact configurations with single-dish data from BGPS and the APEX telescope, achieving an angular resolution of about 4” (0.2 pc) and good image fidelity up to large spatial scales.

Autonomous formation flying sensor for the Star Light Mission

NASA Technical Reports Server (NTRS)

Aung, M.; Purcell, G.; Tien, J.; Young, L.; Srinivasan, J.; Ciminera, M. A.; Chong, Y. J.; Amaro, L. R.; Young, L. E.

2002-01-01

The StarLight Mission, an element of NASA's Origins Program, was designed for first-time demonstration of two technologies: formation flying optical interferometry between spacecraft and autonomous precise formation flying of an array of spacecraft to support optical interferometry. The design overview and results of the technology effort are presented in this paper.

MESAS: Measuring the Emission of Stellar Atmospheres at Submillimeter/millimeter Wavelengths

NASA Astrophysics Data System (ADS)

White, Jacob Aaron; Aufdenberg, Jason; Boley, A. C.; Hauschildt, Peter; Hughes, Meredith; Matthews, Brenda; Wilner, David

2018-06-01

In the early stages of planet formation, small dust grains grow to become millimeter-sized particles in debris disks around stars. These disks can in principle be characterized by their emission at submillimeter and millimeter wavelengths. Determining both the occurrence and abundance of debris in unresolved circumstellar disks of A-type main-sequence stars requires that the stellar photospheric emission be accurately modeled. To better constrain the photospheric emission for such systems, we present observations of Sirius A, an A-type star with no known debris, from the James Clerk Maxwell Telescope, Submillimeter Array, and Jansky Very Large Array at 0.45, 0.85, 0.88, 1.3, 6.7, and 9.0 mm. We use these observations to inform a PHOENIX model of Sirius A’s atmosphere. We find the model provides a good match to these data and can be used as a template for the submillimeter/millimeter emission of other early A-type stars where unresolved debris may be present. The observations are part of an ongoing observational campaign entitled Measuring the Emission of Stellar Atmospheres at Submillimeter/millimeter wavelengths.

The Gould's Belt Very Large Array Survey. I. The Ophiuchus Complex

NASA Astrophysics Data System (ADS)

Dzib, Sergio A.; Loinard, Laurent; Mioduszewski, Amy J.; Rodríguez, Luis F.; Ortiz-León, Gisela N.; Pech, Gerardo; Rivera, Juana L.; Torres, Rosa M.; Boden, Andrew F.; Hartmann, Lee; Evans, Neal J., II; Briceño, Cesar; Tobin, John

2013-09-01

We present large-scale (~2000 arcmin2), deep (~20 μJy), high-resolution (~1'') radio observations of the Ophiuchus star-forming complex obtained with the Karl G. Jansky Very Large Array at λ = 4 and 6 cm. In total, 189 sources were detected, 56 of them associated with known young stellar sources, and 4 with known extragalactic objects; the other 129 remain unclassified, but most of them are most probably background quasars. The vast majority of the young stars detected at radio wavelengths have spectral types K or M, although we also detect four objects of A/F/B types and two brown dwarf candidates. At least half of these young stars are non-thermal (gyrosynchrotron) sources, with active coronas characterized by high levels of variability, negative spectral indices, and (in some cases) significant circular polarization. As expected, there is a clear tendency for the fraction of non-thermal sources to increase from the younger (Class 0/I or flat spectrum) to the more evolved (Class III or weak line T Tauri) stars. The young stars detected both in X-rays and at radio wavelengths broadly follow a Güdel-Benz relation, but with a different normalization than the most radioactive types of stars. Finally, we detect a ~70 mJy compact extragalactic source near the center of the Ophiuchus core, which should be used as gain calibrator for any future radio observations of this region.

Near infrared observations of S155. evidence of induced star formation?

NASA Astrophysics Data System (ADS)

Hunt, L. K.; Lisi, F.; Felli, M.; Tofani, G.

At the interface of the giant molecular cloud Cepheus OB3, S155 represents one of the most interesting examples of bright rim produced by the ionization of a nearby O-star. The interaction between the ionized HII region S155 and the hot molecular core Cepheus B may constitute the ideal site for new stars, according to the sequential star-formation theory. Past observations of molecular lines have shown the evidence of a hot spot in the cloud core, probably a compact region associated to a young stellar object. New J,H,K images recently obtained with the ARNICA array at the TIRGO telescope give evidence of stars with strong near-infrared excess, which must represent the newest generation of young stars.

Radiometric infrared focal plane array imaging system for thermographic applications

NASA Technical Reports Server (NTRS)

Esposito, B. J.; Mccafferty, N.; Brown, R.; Tower, J. R.; Kosonocky, W. F.

1992-01-01

This document describes research performed under the Radiometric Infrared Focal Plane Array Imaging System for Thermographic Applications contract. This research investigated the feasibility of using platinum silicide (PtSi) Schottky-barrier infrared focal plane arrays (IR FPAs) for NASA Langley's specific radiometric thermal imaging requirements. The initial goal of this design was to develop a high spatial resolution radiometer with an NETD of 1 percent of the temperature reading over the range of 0 to 250 C. The proposed camera design developed during this study and described in this report provides: (1) high spatial resolution (full-TV resolution); (2) high thermal dynamic range (0 to 250 C); (3) the ability to image rapid, large thermal transients utilizing electronic exposure control (commandable dynamic range of 2,500,000:1 with exposure control latency of 33 ms); (4) high uniformity (0.5 percent nonuniformity after correction); and (5) high thermal resolution (0.1 C at 25 C background and 0.5 C at 250 C background).

Radiometric infrared focal plane array imaging system for thermographic applications

NASA Astrophysics Data System (ADS)

Esposito, B. J.; McCafferty, N.; Brown, R.; Tower, J. R.; Kosonocky, W. F.

1992-11-01

This document describes research performed under the Radiometric Infrared Focal Plane Array Imaging System for Thermographic Applications contract. This research investigated the feasibility of using platinum silicide (PtSi) Schottky-barrier infrared focal plane arrays (IR FPAs) for NASA Langley's specific radiometric thermal imaging requirements. The initial goal of this design was to develop a high spatial resolution radiometer with an NETD of 1 percent of the temperature reading over the range of 0 to 250 C. The proposed camera design developed during this study and described in this report provides: (1) high spatial resolution (full-TV resolution); (2) high thermal dynamic range (0 to 250 C); (3) the ability to image rapid, large thermal transients utilizing electronic exposure control (commandable dynamic range of 2,500,000:1 with exposure control latency of 33 ms); (4) high uniformity (0.5 percent nonuniformity after correction); and (5) high thermal resolution (0.1 C at 25 C background and 0.5 C at 250 C background).

DEATH-STAR: Silicon and photovoltaic fission fragment detector arrays for light-ion induced fission correlation studies

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

Koglin, J. D.; Burke, J. T.; Fisher, S. E.

Here, the Direct Excitation Angular Tracking pHotovoltaic-Silicon Telescope ARray (DEATH-STAR) combines a series of 12 silicon detectors in a ΔE–E configuration for charged particle identification with a large-area array of 56 photovoltaic (solar) cells for detection of fission fragments. The combination of many scattering angles and fission fragment detectors allows for an angular-resolved tool to study reaction cross sections using the surrogate method, anisotropic fission distributions, and angular momentum transfers through stripping, transfer, inelastic scattering, and other direct nuclear reactions. The unique photovoltaic detectors efficiently detect fission fragments while being insensitive to light ions and have a timing resolution ofmore » 15.63±0.37 ns. Alpha particles are detected with a resolution of 35.5 keV 1σ at 7.9 MeV. Measured fission fragment angular distributions are also presented.« less

DEATH-STAR: Silicon and Photovoltaic Fission Fragment Detector Arrays for Light-Ion Induced Fission Correlation Studies

NASA Astrophysics Data System (ADS)

Koglin, J. D.; Burke, J. T.; Fisher, S. E.; Jovanovic, I.

2017-05-01

The Direct Excitation Angular Tracking pHotovoltaic-Silicon Telescope ARray (DEATH-STAR) combines a series of 12 silicon detectors in a ΔE - E configuration for charged particle identification with a large-area array of 56 photovoltaic (solar) cells for detection of fission fragments. The combination of many scattering angles and fission fragment detectors allows for an angular-resolved tool to study reaction cross sections using the surrogate method, anisotropic fission distributions, and angular momentum transfers through stripping, transfer, inelastic scattering, and other direct nuclear reactions. The unique photovoltaic detectors efficiently detect fission fragments while being insensitive to light ions and have a timing resolution of 15.63±0.37 ns. Alpha particles are detected with a resolution of 35.5 keV 1σ at 7.9 MeV. Measured fission fragment angular distributions are also presented.

DEATH-STAR: Silicon and photovoltaic fission fragment detector arrays for light-ion induced fission correlation studies

DOE PAGES

Koglin, J. D.; Burke, J. T.; Fisher, S. E.; ...

2017-02-20

Here, the Direct Excitation Angular Tracking pHotovoltaic-Silicon Telescope ARray (DEATH-STAR) combines a series of 12 silicon detectors in a ΔE–E configuration for charged particle identification with a large-area array of 56 photovoltaic (solar) cells for detection of fission fragments. The combination of many scattering angles and fission fragment detectors allows for an angular-resolved tool to study reaction cross sections using the surrogate method, anisotropic fission distributions, and angular momentum transfers through stripping, transfer, inelastic scattering, and other direct nuclear reactions. The unique photovoltaic detectors efficiently detect fission fragments while being insensitive to light ions and have a timing resolution ofmore » 15.63±0.37 ns. Alpha particles are detected with a resolution of 35.5 keV 1σ at 7.9 MeV. Measured fission fragment angular distributions are also presented.« less

Wavelet analysis of stellar differential rotation. III. The Sun in white light

NASA Astrophysics Data System (ADS)

Hempelmann, A.

2003-02-01

Future space projects like KEPLER will deliver a vast quantity of high precision light curves of stars. This paper describes a test concerning the observability of rotation and even differential rotation of slowly rotating stars from such data. Two published light curves of solar total irradiance measures are investigated: the Nimbus-7 Earth Radiation Budget (ERB) observations between 1978 and 1993 and the Active Cavity Radiometer Irradiance Monitor I (ACRIM I) measurements between 1980 and 1989. Light curve analysis show that oscillations on time-scales comparable to solar rotation but of a complex pattern are visible. Neither Fourier analysis nor time-frequency Wavelet analysis yield the true rotation period during the more active phases of the solar cycle. The true rotation period dominates only for a short time during solar minimum. In the light of this study even space-born broad band photometry may turn out an inappropriate instrument to study stellar butterfly diagrams of stars rotating as slow as the Sun. However, it was shown in Papers I and II of this series that chromospheric tracers like Lyman alpha , Mg II h+k and CaII H+K are appropriate instruments to perform this task.

Calibration and Performance Of The Juno Microwave Radiometer In Jupiter Orbit

NASA Astrophysics Data System (ADS)

Brown, Shannon; Janssen, Mike; Misra, Sid

2017-04-01

The NASA Juno mission was launched from Kennedy Space Center on August 5th, 2011. Juno is a New Frontiers mission to study Jupiter and carries as one of its payloads a six-frequency microwave radiometer to retrieve the water vapor abundance in the Jovian atmosphere, down to at least 100 bars. The Juno Microwave Radiometer (MWR) operates from 600 MHz to 22 GHz and was designed and built at the Jet Propulsion Laboratory. The MWR radiometer system consists of a MMIC-based receiver for each channel that includes a PIN-diode Dicke switch and three noise diodes distributed along the front end for receiver calibration. The receivers and electronics are housed inside the Juno payload vault, which provides radiation shielding for the Juno payloads. The antenna system consists of patch-array antennas at 600 MHz and 1.2 GHz, slotted waveguide antennas at 2.5, 5.5 and 10 GHz and a feed horn at 22 GHz, providing 20-degree beams at the lowest two frequencies and 12-degree beams at the others. Since launch, MWR has operated nearly continually over the five year cruise. During this time, the Juno spacecraft is spinning on the sky providing the MWR with an excellent calibration source. Furthermore, the spacecraft sun angle and distance have varied, offering a wide range of instrument thermal states to further constrain the calibration. An approach was developed to optimally use the pre-launch and post-launch data to find a calibration solution which minimizes the errors with respect to the pre-launch calibration targets, the post-launch cold sky data and the component level loss/reflection measurements. The extended cruise data allow traceability from the pre-launch measurements to the science observations. In addition, a special data set was taken at apojove during the capture orbits to validate the antenna patterns in-flight using Jupiter as a source. An assessment of the radiometer calibration performance during the first science orbits will be presented. Both the absolute and relative performance will be shown. The relative calibration is assessed by evaluating the temporal stability over the pass and the forward looking and aft looking observations of the same point in the atmosphere.

Calibration and Performance of the Juno Microwave Radiometer during the First Science Orbits

NASA Astrophysics Data System (ADS)

Brown, S. T.; Misra, S.; Janssen, M. A.; Williamson, R.

2016-12-01

The NASA Juno mission was launched from Kennedy Space Center on August 5, 2011 and reached Jupiter orbit on July 4, 2016. Juno is a New Frontiers mission to study Jupiter and carries as one of its payloads a six-frequency microwave radiometer to retrieve the water vapor abundance in the Jovian atmosphere, down to at least 100 bars. The Juno Microwave Radiometer (MWR) operates from 600 MHz to 22 GHz and was designed and built at the Jet Propulsion Laboratory. The MWR radiometer system consists of a MMIC-based receiver for each channel that includes a PIN-diode Dicke switch and three noise diodes distributed along the front end for receiver calibration. The receivers and electronics are housed inside the Juno payload vault, which provides radiation shielding for the Juno payloads. The antenna system consists of patch-array antennas at 600 MHz and 1.2 GHz, slotted waveguide antennas at 2.5, 5.5 and 10 GHz and a feed horn at 22 GHz, providing 20-degree beams at the lowest two frequencies and 12-degree beams at the others. Since launch, MWR has operated nearly continuously over the five year cruise. During this time, the Juno spacecraft is spinning on the sky providing the MWR with an excellent calibration source. Furthermore, the spacecraft sun angle and distance have varied, offering a wide range of instrument thermal states to further constrain the calibration. An approach was developed to optimally use the pre-launch and post-launch data to find a calibration solution which minimizes the errors with respect to the pre-launch calibration targets, the post-launch sky data and the pre-launch RF component level characterization measurements. The extended cruise data allow traceability from the pre-launch measurements to the science observations. In addition, a special data set was taken at apojove during the capture orbits to validate the antenna patterns in-flight using Jupiter as a source. An assessment of the radiometer calibration performance during the first science orbits will be presented.

VizieR Online Data Catalog: Parallaxes of high mass star forming regions (Reid+, 2014)

NASA Astrophysics Data System (ADS)

Reid, M. J.; Menten, K. M.; Brunthaler, A.; Zheng, X. W.; Dame, T. M.; Xu, Y.; Wu, Y.; Zhang, B.; Sanna, A.; Sato, M.; Hachisuka, K.; Choi, Y. K.; Immer, K.; Moscadelli, L.; Rygl, K. L. J.; Bartkiewicz, A.

2016-04-01

Table1 lists the parallaxes and proper motions of 103 regions of high-mass star formation measured with Very Long Baseline Interferometry (VLBI) techniques, using the National Radio Astronomy Observatory's Very Long Baseline Array (VLBA), the Japanese VLBI Exploration of Radio Astrometry (VERA; http://veraserver.mtk.nao.ac.jp) project, and the European VLBI Network (EVN). We have include three red supergiants (NML Cyg, S Per, VY CMa) as indicative of high-mass star forming regions. (2 data files).

NeutronSTARS: A segmented neutron and charged particle detector for low-energy reaction studies

DOE PAGES

Akindele, O. A.; Casperson, R. J.; Wang, B. S.; ...

2017-08-10

NeutronSTARS (Neutron-S ilicon T elescope A rray for R eaction S tudies) consists of 2.2-tons of gadolinium-doped liquid scintillator for neutron detection and large area silicon detectors for charged particle identification. This detector array is intended for low-energy-nuclear-reaction measurements that result in the emission of neutrons such as and fission. This paper describes the NeutronSTARS experimental setup, calibration, and the array’s response to neutral and charged particles.

Protoplanetary Disks in Multiple Star Systems

NASA Astrophysics Data System (ADS)

Harris, Robert J.

Most stars are born in multiple systems, so the presence of a stellar companion may commonly influence planet formation. Theory indicates that companions may inhibit planet formation in two ways. First, dynamical interactions can tidally truncate circumstellar disks. Truncation reduces disk lifetimes and masses, leaving less time and material for planet formation. Second, these interactions might reduce grain-coagulation efficiency, slowing planet formation in its earliest stages. I present three observational studies investigating these issues. First is a spatially resolved Submillimeter Array (SMA) census of disks in young multiple systems in the Taurus-Auriga star-forming region to study their bulk properties. With this survey, I confirmed that disk lifetimes are preferentially decreased in multiples: single stars have detectable millimeter-wave continuum emission twice as often as components of multiples. I also verified that millimeter luminosity (proportional to disk mass) declines with decreasing stellar separation. Furthermore, by measuring resolved-disk radii, I quantitatively tested tidal-truncation theories: results were mixed, with a few disks much larger than expected. I then switch focus to the grain-growth properties of disks in multiple star systems. By combining SMA, Combined Array for Research in Millimeter Astronomy (CARMA), and Jansky Very Large Array (VLA) observations of the circumbinary disk in the UZ Tau quadruple system, I detected radial variations in the grain-size distribution: large particles preferentially inhabit the inner disk. Detections of these theoretically predicted variations have been rare. I related this to models of grain coagulation in gas disks and find that our results are consistent with growth limited by radial drift. I then present a study of grain growth in the disks of the AS 205 and UX Tau multiple systems. By combining SMA, Atacama Large Millimeter/submillimeter Array (ALMA), and VLA observations, I detected radial variations of the grain-size distribution in the AS 205 A disk, but not in the UX Tau A disk. I find that some combination of radial drift and fragmentation limits growth in the AS 205 A disk. In the final chapter, I summarize my findings that, while multiplicity clearly influences bulk disk properties, it does not obviously inhibit grain growth. Other investigations are suggested.

Star Scheduling Mode—A New Observing Strategy for Monitoring Weak Southern Radio Sources with the AuScope VLBI Array

NASA Astrophysics Data System (ADS)

McCallum, Lucia; Mayer, David; Le Bail, Karine; Schartner, Matthias; McCallum, Jamie; Lovell, Jim; Titov, Oleg; Shu, Fengchun; Gulyaev, Sergei

2017-11-01

The International Celestial Reference Frame suffers from significantly less observations in the southern hemisphere compared to the northern one. One reason for this is the historically low number of very long baseline interferometry radio telescopes in the south. The AuScope very long baseline interferometry array with three new telescopes on the Australian continent and an identical antenna in New Zealand were built to address this issue. While the overall number of observations in the south has greatly improved since then, a closer look reveals that this improvement is only true for strong radio sources (source flux densities >0.6 Jy). The new array of small very long baseline interferometry antennas has a relatively low baseline sensitivity so that only strong sources can be observed within a short integration time. A new observing strategy, the star scheduling mode, was developed to enable efficient observations of weak sources during geodetic sessions, through the addition of a single more sensitive antenna to the network. This scheduling mode was implemented in the Vienna very long baseline interferometry Software and applied in four 24-h sessions in 2016. These observations provide updated positions and source flux densities for 42 weak southern radio sources and significantly reduce the formal uncertainties for these sources. The star scheduling mode now allows the AuScope very long baseline interferometry array to undertake greater responsibility in monitoring sources in the southern sky, without significantly weakening the session for geodetic purposes.

Radio emission of cataclysmic variable stars

NASA Technical Reports Server (NTRS)

Fuerst, E.; Benz, A.; Hirth, W.; Geffert, M.; Kiplinger, A.

1986-01-01

Eight cataclysmic variable stars were observed at 6 cm wavelength using the Very Large Array (VLA). The objects were: CN-Ori, SS-Aur, YZ-Cnc, SU-Uma, Z-Cam, V603-Aql, EM-Cyg, and RZ-Sge. Most of these objects were in optical high stage, but none were detected beyond flux limits between 0.1 and 0.3 mJy.

NGVLA Observations of Dense Gas Filaments in Star-Forming Regions

NASA Astrophysics Data System (ADS)

Di Francesco, James; Chen, Mike; Keown, Jared; GAS Team, KEYSTONE Team

2018-01-01

Recent observations of continuum emission from nearby star-forming regions with Herschel and JCMT have revealed that filaments are ubiquitous structures within molecular clouds. Such filaments appear to be intimately connected to star formation, with those having column densities of AV > 8 hosting the majority of prestellar cores and young protostars in clouds. Indeed, this “threshold” can be explained simply as the result of supercritical cylinder fragmentation. How specifically star-forming filaments form in molecular clouds, however, remains unclear, though gravity and turbulence are likely involved. Observations of their kinematics are needed to understand how mass flows both onto and through these filaments. We show here results from two recent surveys, the Green Bank Ammonia Survey (GAS) and the K-band Examinations of Young Stellar Object Natal Environments (KEYSTONE) that have used the Green Bank Telescope’s K-band Focal Plane Array instrument to map NH3 (1,1) emission from dense gas in nearby star-forming regions. Data from both surveys show that NH3 emission traces extremely well the high column density gas across these star-forming regions. In particular, the GAS results for NGC 1333 show NH3-based velocity gradients either predominantly parallel or perpendicular to the filament spines. Though the GAS and KEYSTONE data are vital for probing filaments, higher resolutions than possible with the GBT alone are needed to examine the kinematic patterns on the 0.1-pc scales of star-forming cores within filaments. We describe how the Next Generation Very Large Array (NGVLA) will uniquely provide the key wide-field data of high sensitivity needed to explore how ambient gas in molecular clouds forms filaments that evolve toward star formation.

VLA and ALMA Imaging of Intense Galaxy-wide Star Formation in z ˜ 2 Galaxies

NASA Astrophysics Data System (ADS)

Rujopakarn, W.; Dunlop, J. S.; Rieke, G. H.; Ivison, R. J.; Cibinel, A.; Nyland, K.; Jagannathan, P.; Silverman, J. D.; Alexander, D. M.; Biggs, A. D.; Bhatnagar, S.; Ballantyne, D. R.; Dickinson, M.; Elbaz, D.; Geach, J. E.; Hayward, C. C.; Kirkpatrick, A.; McLure, R. J.; Michałowski, M. J.; Miller, N. A.; Narayanan, D.; Owen, F. N.; Pannella, M.; Papovich, C.; Pope, A.; Rau, U.; Robertson, B. E.; Scott, D.; Swinbank, A. M.; van der Werf, P.; van Kampen, E.; Weiner, B. J.; Windhorst, R. A.

2016-12-01

We present ≃0.″4 resolution extinction-independent distributions of star formation and dust in 11 star-forming galaxies (SFGs) at z = 1.3-3.0. These galaxies are selected from sensitive blank-field surveys of the 2‧ × 2‧ Hubble Ultra-Deep Field at λ = 5 cm and 1.3 mm using the Karl G. Jansky Very Large Array and Atacama Large Millimeter/submillimeter Array. They have star formation rates (SFRs), stellar masses, and dust properties representative of massive main-sequence SFGs at z ˜ 2. Morphological classification performed on spatially resolved stellar mass maps indicates a mixture of disk and morphologically disturbed systems; half of the sample harbor X-ray active galactic nuclei (AGNs), thereby representing a diversity of z ˜ 2 SFGs undergoing vigorous mass assembly. We find that their intense star formation most frequently occurs at the location of stellar-mass concentration and extends over an area comparable to their stellar-mass distribution, with a median diameter of 4.2 ± 1.8 kpc. This provides direct evidence of galaxy-wide star formation in distant blank-field-selected main-sequence SFGs. The typical galactic-average SFR surface density is 2.5 M ⊙ yr-1 kpc-2, sufficiently high to drive outflows. In X-ray-selected AGN where radio emission is enhanced over the level associated with star formation, the radio excess pinpoints the AGNs, which are found to be cospatial with star formation. The median extinction-independent size of main-sequence SFGs is two times larger than those of bright submillimeter galaxies, whose SFRs are 3-8 times larger, providing a constraint on the characteristic SFR (˜300 M ⊙ yr-1) above which a significant population of more compact SFGs appears to emerge.

The Chemistry of Extragalactic Carbon Stars

NASA Technical Reports Server (NTRS)

Woods, Paul; Walsh, C.; Cordiner, M. A.; Kemper, F.

2013-01-01

Prompted by the ongoing interest in Spitzer Infrared Spectrometer spectra of carbon stars in the Large Magellanic Cloud, we have investigated the circumstellar chemistry of carbon stars in low-metallicity environments. Consistent with observations, our models show that acetylene is particularly abundant in the inner regions of low metallicity carbon-rich asymptotic giant branch stars - more abundant than carbon monoxide. As a consequence, larger hydrocarbons have higher abundances at the metallicities of the Magellanic Clouds than in stars with solar metallicity. We also find that the oxygen and nitrogen chemistry is suppressed at lower metallicity, as expected. Finally, we calculate molecular line emission from carbon stars in the Large and Small Magellanic Cloud and find that several molecules should be readily detectable with the Atacama Large Millimeter Array at Full Science operations.

Highlights from 4STAR Sky-Scanning Retrievals of Aerosol Intensive Optical Properties from Multiple Field Campaigns with Detailed Comparisons of SSA Reported During SEAC4RS

NASA Technical Reports Server (NTRS)

Dunagan, Stephen E.

2016-01-01

The 4STAR (Spectrometer for Sky-Scanning, Sun-Tracking Atmospheric Research) instrument combines airborne sun tracking capabilities of the Ames Airborne Tracking Sun Photometer (AATS-14) with AERONET (Aerosol Robotic Network)-like sky-scanning capability and adds state-of-the-art fiber-coupled grating spectrometry to yield hyperspectral measurements of direct solar irradiance and angularly resolved sky radiance. The combination of sun-tracking and sky-scanning capability enables retrievals of wavelength-dependent aerosol optical depth (AOD), mode-resolved aerosol size distribution (SD), asphericity, and complex refractive index, and thus also the scattering phase function, asymmetry parameter, single-scattering albedo (SSA), and absorption aerosol optical thickness (AAOT). From 2012 to 2014 4STAR participated in four major field campaigns: the U.S. Dept. of Energy's TCAP (Two-Column Aerosol Project) I & II campaigns, and NASA's SEAC4RS (Studies of Emissions, Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys) and ARISE (Arctic Radiation - IceBridge Sea & Ice Experiment) campaigns. Establishing a strong performance record, 4STAR operated successfully on all flights conducted during each of these campaigns. Sky radiance spectra from scans in either constant azimuth (principal plane) or constant zenith angle (almucantar) were interspersed with direct beam measurements during level legs. During SEAC4RS and ARISE, 4STAR airborne measurements were augmented with flight-level albedo from the collocated Shortwave Spectral Flux Radiometer (SSFR) providing improved specification of below-aircraft radiative conditions for the retrieval. Calibrated radiances and retrieved products will be presented with particular emphasis on detailed comparisons of ambient SSA retrievals and measurements during SEAC4RS from 4STAR, AERONET, HSRL2 (High Spectral Resolution Lidar), and from in situ measurements.

Calibration and Measurement Uncertainty Estimation of Radiometric Data: Preprint

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

Habte, A.; Sengupta, M.; Reda, I.

2014-11-01

Evaluating the performance of photovoltaic cells, modules, and arrays that form large solar deployments relies on accurate measurements of the available solar resource. Therefore, determining the accuracy of these solar radiation measurements provides a better understanding of investment risks. This paper provides guidelines and recommended procedures for estimating the uncertainty in calibrations and measurements by radiometers using methods that follow the International Bureau of Weights and Measures Guide to the Expression of Uncertainty (GUM). Standardized analysis based on these procedures ensures that the uncertainty quoted is well documented.

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.

Aerodynamic effect of combustor inlet-air pressure on fuel jet atomization

NASA Technical Reports Server (NTRS)

Ingebo, R. D.

1984-01-01

Mean drop diameters were measured with a recently developed scanning radiometer in a study of the atomization of liquid jets injected cross stream in high velocity and high pressure airflows. At constant inlet air pressure, reciprocal mean drop diameter was correlated with airflow mass velocity. Over a combustor inlet-air pressure range of 1 to 21 atmospheres, the ratio of orifice to mean drop diameter, D(O)/D(M), was correlated with the product of Weber and Reynolds number, WeRe, and with the molecular scale momentum transfer ratio of gravitational to inertial forces. Previously announced in STAR as N84-22910

The Cosmic Background Explorer

NASA Technical Reports Server (NTRS)

Gulkis, Samuel; Lubin, Philip M.; Meyer, Stephan S.; Silverberg, Robert F.

1990-01-01

The Cosmic Background Explorer (CBE), NASA's cosmological satellite which will observe a radiative relic of the big bang, is discussed. The major questions connected to the big bang theory which may be clarified using the CBE are reviewed. The satellite instruments and experiments are described, including the Differential Microwave Radiometer, which measures the difference between microwave radiation emitted from two points on the sky, the Far-Infrared Absolute Spectrophotometer, which compares the spectrum of radiation from the sky at wavelengths from 100 microns to one cm with that from an internal blackbody, and the Diffuse Infrared Background Experiment, which searches for the radiation from the earliest generation of stars.

Coordinated ultraviolet and radio observations of selected nearby stars

NASA Technical Reports Server (NTRS)

Lang, Kenneth R.

1987-01-01

All of the US2 shifts assigned were successfully completed with simultaneous International Ultraviolet Explorer (IUE) and the Very Large Array (VLA) observations of the proposed target stars. The target stars included dwarf M flare stars and RS CVn stars. The combined ultraviolet (IUE) and microwave (VLA) observations have provided important new insights to the radiation mechanisms at these two widely-separated regions of the electromagnetic spectrum. The VLA results included the discovery of narrow-band microwave radiation and rapid time variations in the microwave radiation of dwarf M flare stars. The results indicate that conventional radiation mechanisms cannot explain the microwave emission from these stars. In general, ultraviolet variations and bursts occur when no similar variations are detected at microwave wavelengths and vice versa. Although these is some overlap, the variations in these two spectral regions are usually uncorrelated, suggesting that there is little interaction between the activity centers at the two associated atmospheric levels.

Detection of Jasmine virus H and characterization of a second pelarspovirus infecting star jasmine (Jasminum multiflorum) and angelwing jasmine (J. nitidum) plants displaying virus-like symptoms

USDA-ARS?s Scientific Manuscript database

Star jasmine (Jasminum multiflorum) plants growing in Hawaii expressing a diverse array of virus-like foliar symptoms were examined for the presence of a causal agent. Symptomatic tissues collected from three locations on the island of Oahu, Hawaii consistently harbored double-stranded (ds)RNAs app...

Imaging Polarized Dust Emission in Star Formation Regions with the OVRO MM Array

NASA Technical Reports Server (NTRS)

Akeson, Rachel; Carlstrom, John

1996-01-01

We present OVRO interferometric observations of linearly polarized emission from magnetically aligned dust grains which allow the magnetic field geometry in nearby star formation regions to be probed on scales ranging from 100 to 3000 AU. Current results include observations of the young stellar objects NGC1333/IRAS 4A, IRAS 16293-2422 and Orion IRc2-KL.

From Large-scale to Protostellar Disk Fragmentation into Close Binary Stars

NASA Astrophysics Data System (ADS)

Sigalotti, Leonardo Di G.; Cruz, Fidel; Gabbasov, Ruslan; Klapp, Jaime; Ramírez-Velasquez, José

2018-04-01

Recent observations of young stellar systems with the Atacama Large Millimeter/submillimeter Array (ALMA) and the Karl G. Jansky Very Large Array are helping to cement the idea that close companion stars form via fragmentation of a gravitationally unstable disk around a protostar early in the star formation process. As the disk grows in mass, it eventually becomes gravitationally unstable and fragments, forming one or more new protostars in orbit with the first at mean separations of 100 au or even less. Here, we report direct numerical calculations down to scales as small as ∼0.1 au, using a consistent Smoothed Particle Hydrodynamics code, that show the large-scale fragmentation of a cloud core into two protostars accompanied by small-scale fragmentation of their circumstellar disks. Our results demonstrate the two dominant mechanisms of star formation, where the disk forming around a protostar (which in turn results from the large-scale fragmentation of the cloud core) undergoes eccentric (m = 1) fragmentation to produce a close binary. We generate two-dimensional emission maps and simulated ALMA 1.3 mm continuum images of the structure and fragmentation of the disks that can help explain the dynamical processes occurring within collapsing cloud cores.

Design of a Day/Night Star Camera System

NASA Technical Reports Server (NTRS)

Alexander, Cheryl; Swift, Wesley; Ghosh, Kajal; Ramsey, Brian

1999-01-01

This paper describes the design of a camera system capable of acquiring stars during both the day and night cycles of a high altitude balloon flight (35-42 km). The camera system will be filtered to operate in the R band (590-810 nm). Simulations have been run using MODTRAN atmospheric code to determine the worse case sky brightness at 35 km. With a daytime sky brightness of 2(exp -05) W/sq cm/str/um in the R band, the sensitivity of the camera system will allow acquisition of at least 1-2 stars/sq degree at star magnitude limits of 8.25-9.00. The system will have an F2.8, 64.3 mm diameter lens and a 1340X1037 CCD array digitized to 12 bits. The CCD array is comprised of 6.8 X 6.8 micron pixels with a well depth of 45,000 electrons and a quantum efficiency of 0.525 at 700 nm. The camera's field of view will be 6.33 sq degree and provide attitude knowledge to 8 arcsec or better. A test flight of the system is scheduled for fall 1999.

ALMA reveals sunburn: CO dissociation around AGB stars in the globular cluster 47 Tucanae

NASA Astrophysics Data System (ADS)

McDonald, I.; Zijlstra, A. A.; Lagadec, E.; Sloan, G. C.; Boyer, M. L.; Matsuura, M.; Smith, R. J.; Smith, C. L.; Yates, J. A.; van Loon, J. Th.; Jones, O. C.; Ramstedt, S.; Avison, A.; Justtanont, K.; Olofsson, H.; Blommaert, J. A. D. L.; Goldman, S. R.; Groenewegen, M. A. T.

2015-11-01

Atacama Large Millimetre Array observations show a non-detection of carbon monoxide around the four most luminous asymptotic giant branch (AGB) stars in the globular cluster 47 Tucanae. Stellar evolution models and star counts show that the mass-loss rates from these stars should be ˜1.2-3.5 × 10-7 M⊙ yr-1. We would naïvely expect such stars to be detectable at this distance (4.5 kpc). By modelling the ultraviolet radiation field from post-AGB stars and white dwarfs in 47 Tuc, we conclude that CO should be dissociated abnormally close to the stars. We estimate that the CO envelopes will be truncated at a few hundred stellar radii from their host stars and that the line intensities are about two orders of magnitude below our current detection limits. The truncation of CO envelopes should be important for AGB stars in dense clusters. Observing the CO (3-2) and higher transitions and targeting stars far from the centres of clusters should result in the detections needed to measure the outflow velocities from these stars.

On-Orbit Cross-Calibration of AM Satellite Remote Sensing Instruments using the Moon

NASA Technical Reports Server (NTRS)

Butler, James J.; Kieffer, Hugh H.; Barnes, Robert A.; Stone, Thomas C.

2003-01-01

On April 14,2003, three Earth remote sensing spacecraft were maneuvered enabling six satellite instruments operating in the visible through shortwave infrared wavelength region to view the Moon for purposes of on-orbit cross-calibration. These instruments included the Moderate Resolution Imaging Spectroradiometer (MODIS), the Multi-angle Imaging SpectroRadiometer (MISR), the Advanced Spaceborne Thermal Emission and Reflection (ASTER) radiometer on the Earth Observing System (EOS) Terra spacecraft, the Advanced Land Imager (ALI) and Hyperion instrument on Earth Observing-1 (EO-1) spacecraft, and the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) on the SeaStar spacecraft. Observations of the Moon were compared using a spectral photometric mode for lunar irradiance developed by the Robotic Lunar Observatory (ROLO) project located at the United States Geological Survey in Flagstaff, Arizona. The ROLO model effectively accounts for variations in lunar irradiance corresponding to lunar phase and libration angles, allowing intercomparison of observations made by instruments on different spacecraft under different time and location conditions. The spacecraft maneuvers necessary to view the Moon are briefly described and results of using the lunar irradiance model in comparing the radiometric calibration scales of the six satellite instruments are presented here.

Flight solar calibrations using the Mirror Attenuator Mosaic (MAM): Low scattering mirror

NASA Technical Reports Server (NTRS)

Lee, Robert B., III

1992-01-01

Measurements of solar radiances reflected from the mirror attenuator mosaic (MAM) were used to calibrate the shortwave portions of the Earth Radiation Budget Experiment (ERBE) thermistor bolometer scanning radiometers. The MAM is basically a low scattering mirror which has been used to attenuate and reflect solar radiation into the fields of view for the broadband shortwave (0.2 to 5 micrometers) and total (0.2 to 50.0+ micrometers) ERBE scanning radiometers. The MAM assembly consists of a tightly packed array of aluminum, 0.3175-cm diameter concave spherical mirrors and field of view limiting baffles. The spherical mirrors are masked by a copper plate, electro-plated with black chrome. Perforations (0.14 centimeter in diameter) in the copper plate serve as apertures for the mirrors. Black anodized aluminum baffles limit the MAM clear field of view to 7.1 degrees. The MAM assemblies are located on the Earth Radiation Budget Satellite (ERBS) and on the National Oceanic and Atmospheric Administration NOAA-9 and NOAA-10 spacecraft. The 1984-1985 ERBS and 1985-1986 NOAA-9 solar calibration datasets are presented. Analyses of the calibrations indicate that the MAM exhibited no detectable degradation in its reflectance properties and that the gains of the shortwave scanners did not change. The stability of the shortwave radiometers indicates that the transmission of the Suprasil W1 filters did not degrade detectably when exposed to Earth/atmosphere-reflected solar radiation.

MINERVA: Small Planets from Small Telescopes

NASA Astrophysics Data System (ADS)

Wittenmyer, Robert A.; Johnson, John Asher; Wright, Jason; McCrady, Nate; Swift, Jonathan; Bottom, Michael; Plavchan, Peter; Riddle, Reed; Muirhead, Philip S.; Herzig, Erich; Myles, Justin; Blake, Cullen H.; Eastman, Jason; Beatty, Thomas G.; Lin, Brian; Zhao, Ming; Gardner, Paul; Falco, Emilio; Criswell, Stephen; Nava, Chantanelle; Robinson, Connor; Hedrick, Richard; Ivarsen, Kevin; Hjelstrom, Annie; de Vera, Jon; Szentgyorgyi, Andrew

2015-09-01

The Kepler mission has shown that small planets are extremely common. It is likely that nearly every star in the sky hosts at least one rocky planet. We just need to look hard enough-but this requires vast amounts of telescope time. MINERVA (MINiature Exoplanet Radial Velocity Array) is a dedicated exoplanet observatory with the primary goal of discovering rocky, Earth-like planets orbiting in the habitable zone of bright, nearby stars. The MINERVA team is a collaboration among UNSW Australia, Harvard-Smithsonian Center for Astrophysics, Penn State University, University of Montana, and the California Institute of Technology. The four-telescope MINERVA array will be sited at the F.L. Whipple Observatory on Mt Hopkins in Arizona, USA. Full science operations will begin in mid-2015 with all four telescopes and a stabilised spectrograph capable of high-precision Doppler velocity measurements. We will observe ~100 of the nearest, brightest, Sun-like stars every night for at least five years. Detailed simulations of the target list and survey strategy lead us to expect new low-mass planets.

NuSTAR Briefing

NASA Image and Video Library

2012-05-30

Yunjin Kim, NuSTAR project manager at the Jet Propulsion Laborartory (JPL), talks about NASA's Spectroscopic Telescope Array (NuStar) during a briefing, Wednesday, May 30, 2012, at NASA Headquarters in Washington. Imaging light in the high-energy, short-wavelength X-ray range, the telescope will aim to study how black holes form and evolve along with galaxies. The instrument, packed aboard an Orbital Sciences Pegasus XL rocket is set to launch from a plane in midair no earlier than June 13 from Kwajalein Atoll in the Marshall Islands. Photo Credit: (NASA/Paul E. Alers)

The galatic and LMC extreme line supergiants compared: IUE observations of the Henize-Carlson and Zoo star samples of massive supergiants. [Large Magellanic cloud (LMC)

NASA Technical Reports Server (NTRS)

Shore, S. N.; Sanduleak, N.; Brown, D. N.; Sonneborn, G.; Bopp, B. W.; Robinson, C. R.

1988-01-01

The Henize-Carlson sample of galactic massive supergiants, and a comparison between the Galactic and LMC samples are discussed. Several of the stars, notably He3-395 and S 127/LMC, have very similar shell characteristics. There appears to be little difference, other than luminosity, between the LMC and Galactic samples. One star, He3-1482, was detected with the Very Large Array at 6 cm. The UV data is combined with IRAS and optical information.

Interferometric diameters of five evolved intermediate-mass planet-hosting stars measured with PAVO at the CHARA Array

NASA Astrophysics Data System (ADS)

White, T. R.; Huber, D.; Mann, A. W.; Casagrande, L.; Grunblatt, S. K.; Justesen, A. B.; Silva Aguirre, V.; Bedding, T. R.; Ireland, M. J.; Schaefer, G. H.; Tuthill, P. G.

2018-04-01

Debate over the planet occurrence rates around intermediate-mass stars has hinged on the accurate determination of masses of evolved stars, and has been exacerbated by a paucity of reliable, directly-measured fundamental properties for these stars. We present long-baseline optical interferometry of five evolved intermediate-mass (˜ 1.5 M⊙) planet-hosting stars using the PAVO beam combiner at the CHARA Array, which we combine with bolometric flux measurements and parallaxes to determine their radii and effective temperatures. We measured the radii and effective temperatures of 6 Lyncis (5.12±0.16 R⊙, 4949±58 K), 24 Sextantis (5.49±0.18 R⊙, 4908±65 K), κ Coronae Borealis (4.77±0.07 R⊙, 4870±47 K), HR 6817 (4.45±0.08 R⊙, 5013±59 K), and HR 8641 (4.91±0.12 R⊙, 4950±68 K). We find disagreements of typically 15 % in angular diameter and ˜ 200 K in temperature compared to interferometric measurements in the literature, yet good agreement with spectroscopic and photometric temperatures, concluding that the previous interferometric measurements may have been affected by systematic errors exceeding their formal uncertainties. Modelling based on BaSTI isochrones using various sets of asteroseismic, spectroscopic, and interferometric constraints tends to favour slightly (˜ 15 %) lower masses than generally reported in the literature.

Interferometric diameters of five evolved intermediate-mass planet-hosting stars measured with PAVO at the CHARA Array

NASA Astrophysics Data System (ADS)

White, T. R.; Huber, D.; Mann, A. W.; Casagrande, L.; Grunblatt, S. K.; Justesen, A. B.; Silva Aguirre, V.; Bedding, T. R.; Ireland, M. J.; Schaefer, G. H.; Tuthill, P. G.

2018-07-01

Debate over the planet occurrence rates around intermediate-mass stars has hinged on the accurate determination of masses of evolved stars, and has been exacerbated by a paucity of reliable, directly measured fundamental properties for these stars. We present long-baseline optical interferometry of five evolved intermediate-mass (˜ 1.5 M⊙) planet-hosting stars using the PAVO beam combiner at the CHARA Array, which we combine with bolometric flux measurements and parallaxes to determine their radii and effective temperatures. We measured the radii and effective temperatures of 6 Lyncis (5.12 ± 0.16 R⊙, 4949 ± 58 K), 24 Sextantis (5.49 ± 0.18 R⊙, 4908 ± 65 K), κ Coronae Borealis (4.77 ± 0.07 R⊙, 4870 ± 47 K), HR 6817 (4.45 ± 0.08 R⊙, 5013 ± 59 K), and HR 8461 (4.91 ± 0.12 R⊙, 4950 ± 68 K). We find disagreements of typically 15 per cent in angular diameter and ˜200 K in temperature compared to interferometric measurements in the literature, yet good agreement with spectroscopic and photometric temperatures, concluding that the previous interferometric measurements may have been affected by systematic errors exceeding their formal uncertainties. Modelling based on BaSTI isochrones using various sets of asteroseismic, spectroscopic, and interferometric constraints tends to favour slightly (˜15 per cent) lower masses than generally reported in the literature.

High Precision Photometry of Bright Transiting Exoplanet Hosts

NASA Astrophysics Data System (ADS)

Wilson, Maurice; Eastman, Jason; Johnson, John A.

2016-01-01

Within the past two decades, the successful search for exoplanets and the characterization of their physical properties have shown the immense progress that has been made towards finding planets with characteristics similar to Earth. For most exoplanets with a radius about the size of Earth, evaluating their physical properties, such as the mass, radius and equilibrium temperature, cannot be determined with satisfactory precision. The MINiature Exoplanet Radial Velocity Array (MINERVA) was recently built to obtain spectroscopic and photometric measurements to find, confirm, and characterize Earth-like exoplanets. MINERVA's spectroscopic survey targets the brightest, nearby stars which are well-suited to the array's capabilities, while its primary photometric goal is to search for transits around these bright targets. Typically, it is difficult to find satisfactory comparison stars within a telescope's field of view when the primary target is very bright. This issue is resolved by using one of MINERVA's telescopes to observe the primary bright star while the other telescopes observe a distinct field of view that contains satisfactory bright comparison stars. We describe the code used to identify nearby comparison stars, schedule the four telescopes, produce differential photometry from multiple telescopes, and show the first results from this effort.This work has been funded by the Ronald E. McNair Post-Baccalaureate Achievement Program, the ERAU Honors Program, the ERAU Undergraduate Research Spark Fund, and the Banneker Institute at the Harvard-Smithsonian Center for Astrophysics.

Exploring the multifaceted circumstellar environment of the luminous blue variable HR Carinae

NASA Astrophysics Data System (ADS)

Buemi, C. S.; Trigilio, C.; Leto, P.; Umana, G.; Ingallinera, A.; Cavallaro, F.; Cerrigone, L.; Agliozzo, C.; Bufano, F.; Riggi, S.; Molinari, S.; Schillirò, F.

2017-03-01

We present a multiwavelength study of the Galactic luminous blue variable HR Carinae, based on new high-resolution mid-infrared (IR) and radio images obtained with the Very Large Telescope (VLT) and the Australia Telescope Compact Array (ATCA), which have been complemented by far-infrared Herschel-Photodetector Array Camera and Spectrometer (PACS) observations and ATCA archive data. The Herschel images reveal the large-scale distribution of the dusty emitting nebula, which extends mainly to the north-east direction, up to 70 arcsec from the central star, and is oriented along the direction of the space motion of the star. In the mid-infrared images, the brightness distribution is characterized by two arc-shaped structures, tracing an inner envelope surrounding the central star more closely. At radio wavelengths, the ionized gas emission lies on the opposite side of the cold dust with respect to the position of the star, as if the ionized front were confined by the surrounding medium in the north-south direction. Comparison with previous data indicates significant changes in the radio nebula morphology and in the mass-loss rate from the central star, which has increased from 6.1 × 10-6 M⊙ yr-1 in 1994-1995 to 1.17 × 10-5 M⊙ yr-1 in 2014. We investigate possible scenarios that could have generated the complex circumstellar environment revealed by our multiwavelength data.

Accurate effective temperatures of the metal-poor benchmark stars HD 140283, HD 122563, and HD 103095 from CHARA interferometry

NASA Astrophysics Data System (ADS)

Karovicova, I.; White, T. R.; Nordlander, T.; Lind, K.; Casagrande, L.; Ireland, M. J.; Huber, D.; Creevey, O.; Mourard, D.; Schaefer, G. H.; Gilmore, G.; Chiavassa, A.; Wittkowski, M.; Jofré, P.; Heiter, U.; Thévenin, F.; Asplund, M.

2018-03-01

Large stellar surveys of the Milky Way require validation with reference to a set of `benchmark' stars whose fundamental properties are well determined. For metal-poor benchmark stars, disagreement between spectroscopic and interferometric effective temperatures has called the reliability of the temperature scale into question. We present new interferometric measurements of three metal-poor benchmark stars, HD 140283, HD 122563, and HD 103095, from which we determine their effective temperatures. The angular sizes of all the stars were determined from observations with the PAVO beam combiner at visible wavelengths at the CHARA array, with additional observations of HD 103095 made with the VEGA instrument, also at the CHARA array. Together with photometrically derived bolometric fluxes, the angular diameters give a direct measurement of the effective temperature. For HD 140283, we find θLD = 0.324 ± 0.005 mas, Teff = 5787 ± 48 K; for HD 122563, θLD = 0.926 ± 0.011 mas, Teff = 4636 ± 37 K; and for HD 103095, θLD = 0.595 ± 0.007 mas, Teff = 5140 ± 49 K. Our temperatures for HD 140283 and HD 103095 are hotter than the previous interferometric measurements by 253 and 322 K, respectively. We find good agreement between our temperatures and recent spectroscopic and photometric estimates. We conclude some previous interferometric measurements have been affected by systematic uncertainties larger than their quoted errors.

Geostationary Coastal and Air Pollution Events (GeoCAPE) Filter Radiometer (FR)

NASA Technical Reports Server (NTRS)

Kotecki, Carl; Chu, Martha; Wilson, Mark; Clark, Mike; Nanan, Bobby; Matson, Liz; McBirney, Dick; Smith, Jay; Earle, Paul; Choi, Mike;

Surrogate 239Pu(n, fxn) and 241Pu(n, fxn) average fission-neutron-multiplicity measurements

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

Burke, J. T.; Alan, B. S.; Akindele, O. A.

2017-09-26

We have constructed a new neutron-charged-particle detector array called NeutronSTARS. It has been described extensively in LLNL-TR-703909 [1] and Akindele et al [2]. We have used this new neutron-charged-particle array to measure the 241Pu and 239Pu fissionneutron multiplicity as a function of equivalent incident-neutron energy from 100 keV to 20 MeV. The experimental approach, detector array, data analysis, and results are summarized in the following sections.

NASA Tech Briefs, November 2012

NASA Technical Reports Server (NTRS)

2012-01-01

The topics include: Visual System for Browsing, Analysis, and Retrieval of Data (ViSBARD); Time-Domain Terahertz Computed Axial Tomography NDE System; Adaptive Sampling of Time Series During Remote Exploration; A Tracking Sun Photometer Without Moving Parts; Surface Temperature Data Analysis; Modular, Autonomous Command and Data Handling Software with Built-In Simulation and Test; In-Situ Wire Damage Detection System; Amplifier Module for 260-GHz Band Using Quartz Waveguide Transitions; Wideband Agile Digital Microwave Radiometer; Buckyball Nucleation of HiPco Tubes; FACT, Mega-ROSA, SOLAROSA; An Integrated, Layered-Spinel Composite Cathode for Energy Storage Applications; Engineered Multifunctional Surfaces for Fluid Handling; Polyolefin-Based Aerogels; Adjusting Permittivity by Blending Varying Ratios of SWNTs; Gravity-Assist Mechanical Simulator for Outreach; Concept for Hydrogen-Impregnated Nanofiber/Photovoltaic Cargo Stowage System; DROP: Durable Reconnaissance and Observation Platform; Developing Physiologic Models for Emergency Medical Procedures Under Microgravity; Spectroscopic Chemical Analysis Methods and Apparatus; Low Average Sidelobe Slot Array Antennas for Radiometer Applications; Motion-Corrected 3D Sonic Anemometer for Tethersondes and Other Moving Platforms; Water Treatment Systems for Long Spaceflights; Microchip Non-Aqueous Capillary Electrophoresis (MicronNACE) Method to Analyze Long-Chain Primary Amines; Low-Cost Phased Array Antenna for Sounding Rockets, Missiles, and Expendable Launch Vehicles; Mars Science Laboratory Engineering Cameras; Seismic Imager Space Telescope; Estimating Sea Surface Salinity and Wind Using Combined Passive and Active L-Band Microwave Observations; A Posteriori Study of a DNS Database Describing Super critical Binary-Species Mixing; Scalable SCPPM Decoder; QuakeSim 2.0; HURON (HUman and Robotic Optimization Network) Multi-Agent Temporal Activity Planner/Scheduler; MPST Software: MoonKommand

Thermal Infrared Airborne Field Studies: Applications to the Mars Global Surveyor Thermal Emission Spectrometer

NASA Astrophysics Data System (ADS)

Herr, K.; Kirkland, L.; Keim, E.; Hackwell, J.

2002-12-01

A primary goal of the Mars exploration program is to reconnoiter the planet from orbit using infrared remote sensing. Currently the Global Surveyor Thermal Emission Spectrometer (TES) and the 2001 Mars Odyssey 9-band radiometer THEMIS provide this capability. Landing site selection and modeling of the geologic and climate history depend on accurate interpretations of these data sets. Interpretations use terrestrial analog remote sensing and laboratory studies. Until recently, there have been no airborne thermal infrared spectrometer ("hyspectral") data sets available to NASA researchers that are comparable to TES. As a result, studies relied on airborne multi-channel radiometer ("multispectral") measurements (e.g. TIMS, MASTER). A radiometer has the advantage that measurement of broad bands makes it easier to measure with higher sensitivity. However, radiometers lack the spectral resolution to investigate details of spectral signatures. This gap may be partially addressed using field samples collected and measured in the laboratory. However, that leaves questions unanswered about the field environment and potentially leaves important complicating issues undiscovered. Two questions that haunt thermal infrared remote sensing investigations of Mars are: (1) If a mineral is not detected in a given data set, how definitively should we state that it is not there? (2) When does the method provide quantitative mineral mapping? In order to address these questions, we began collaborating with Department of Defense (DoD) oriented researchers and drawing on the unique instrumentation they developed. Both Mars and DoD researchers have a common need to identify materials without benefit of ground truth. Such collaborations provide a fresh perspective as well as unique data. Our work addresses uncertainties in stand-off identification of solid phase surface materials when the identification must proceed without benefit of ground truth. We will report on the results applied to TES, with a focus on the two primary questions above. We use images recorded by a unique airborne imaging spectrometer, the Spatially Enhanced Broadband Array Spectrograph System. SEBASS uses cooled prisms to measure 2.4-5.3 and 7.6-13.5 microns. Each range is measured in 128 channels, with a spectral resolution of 7 wavenumbers at 890 wavenumbers, and a one milliradian field of view per pixel. SEBASS operates as a pushbroom instrument, using two 128 x 128 detector arrays, and the entire optical bench is cooled to 4K using liquid helium. It is operated by The Aerospace Corporation, which is a non-profit Federally Funded Research and Development Center. Images are typically 128 pixels wide and 2000 pixels long, measured with a surface spatial resolution of ~1 or 2 square meters. TES measures ~6.5-50 microns in 143 channels, with a spectral resolution of 10 or 20 wavenumbers. Issues that affect the spectral signature include surface roughness, particle size, coatings, reflected downwelling radiance, atmospheric transmission, and atmospheric reemission. A full understanding of these effects is required in order to determine the uncertainties in field interpretations, whether terrestrially or on Mars. SEBASS data fill this need by measuring with a sensitivity comparable to laboratory data, and sufficient spectral resolution to examine subtle spectral effects that are not resolvable in multi-channel radiometer data.

KSC-2012-1360

NASA Image and Video Library

2012-02-16

VANDENBERG AIR FORCE BASE, Calif. -- NuSTAR’s X-ray telescope is visible during the solar array deployment test at Vandenberg Air Force Base's processing facility in California. The Pegasus will launch NASA's Nuclear Spectroscopic Telescope Array NuSTAR into space. After the rocket and spacecraft are processed at Vandenberg, they will be flown on the Orbital Sciences’ L-1011 carrier aircraft to the Ronald Reagan Ballistic Missile Defense Test Site at the Pacific Ocean’s Kwajalein Atoll for launch. The high-energy x-ray telescope will conduct a census for black holes, map radioactive material in young supernovae remnants, and study the origins of cosmic rays and the extreme physics around collapsed stars. For more information, visit science.nasa.gov/missions/nustar/. Photo credit: NASA/Randy Beaudoin, VAFB

KSC-2012-1358

NASA Image and Video Library

2012-02-16

VANDENBERG AIR FORCE BASE, Calif. -- As a technician monitors the solar array deployment test at Vandenberg Air Force Base's processing facility in California, NuSTAR’s X-ray telescope is visible. The Pegasus will launch NASA's Nuclear Spectroscopic Telescope Array NuSTAR into space. After the rocket and spacecraft are processed at Vandenberg, they will be flown on the Orbital Sciences’ L-1011 carrier aircraft to the Ronald Reagan Ballistic Missile Defense Test Site at the Pacific Ocean’s Kwajalein Atoll for launch. The high-energy x-ray telescope will conduct a census for black holes, map radioactive material in young supernovae remnants, and study the origins of cosmic rays and the extreme physics around collapsed stars. For more information, visit science.nasa.gov/missions/nustar/. Photo credit: NASA/Randy Beaudoin, VAFB

Accuracy of measurement of star images on a pixel array

NASA Technical Reports Server (NTRS)

King, I. R.

1983-01-01

Algorithms are developed for predicting the accuracy with which the brightness of a star can be determined from its image on a digital detector array, as a function of the brightness of the background. The assumption is made that a known profile is being fitted by least squares. The two profiles used correspond to ST images and to ground-based observations. The first result is an approximate rule of thumb for equivalent noise area. More rigorous results are then given in tabular form. The size of the pixels, relative to the image size, is taken into account. Astronometric accuracy is also discussed briefly; the error, relative to image size, is very similar to the photometric error relative to brightness.

KSC-2012-1359

NASA Image and Video Library

2012-02-16

VANDENBERG AIR FORCE BASE, Calif. -- As a technician monitors the solar array deployment test at Vandenberg Air Force Base's processing facility in California, NuSTAR’s X-ray telescope is visible. The Pegasus will launch NASA's Nuclear Spectroscopic Telescope Array NuSTAR into space. After the rocket and spacecraft are processed at Vandenberg, they will be flown on the Orbital Sciences’ L-1011 carrier aircraft to the Ronald Reagan Ballistic Missile Defense Test Site at the Pacific Ocean’s Kwajalein Atoll for launch. The high-energy x-ray telescope will conduct a census for black holes, map radioactive material in young supernovae remnants, and study the origins of cosmic rays and the extreme physics around collapsed stars. For more information, visit science.nasa.gov/missions/nustar/. Photo credit: NASA/Randy Beaudoin, VAFB

Stellar Parameters and Radial Velocities of Hot Stars in the Carina Nebula

NASA Astrophysics Data System (ADS)

Hanes, Richard J.; McSwain, M. Virginia; Povich, Matthew S.

2018-05-01

The Carina Nebula is an active star-forming region in the southern sky that is of particular interest due to the presence of a large number of massive stars in a wide array of evolutionary stages. Here, we present the results of the spectroscopic analysis of 82 B-type stars and 33 O-type stars that were observed in 2013 and 2014. For 82 B-type stars without line blending, we fit model spectra from the Tlusty BSTAR2006 grid to the observed profiles of Hγ and He λλ4026, 4388, and 4471 to measure the effective temperatures, surface gravities, and projected rotational velocities. We also measure the masses, ages, radii, bolometric luminosities, and distances of these stars. From the radial velocities measured in our sample, we find 31 single lined spectroscopic binary candidates. We find a high dispersion of radial velocities among our sample stars, and we argue that the Carina Nebula stellar population has not yet relaxed and become virialized.

Flight Integral Field Spectrograph (IFS) Optical Design for WFIRST Coronagraphic Exoplanet Demonstration

NASA Technical Reports Server (NTRS)

Gong, Qian; Groff, Tyler D.; Zimmerman, Neil; Mandell, Avi; McElwain, Michael; Rizzo, Maxime; Saxena, Prabal

2017-01-01

Based on the experience from Prototype Imaging Spectrograph for Coronagraphic Exoplanet Studies (PISCES) for WFIRST, we have moved to the flight instrument design phase. The specifications for flight IFS have similarities and differences from the prototype. This paper starts with the science and system requirement, discusses a number of critical trade-offs: such as IFS type selection, lenslet array shape and layout versus detector pixel accuracy, how to accommodate the larger Field Of View (FOV) and wider wavelength band for a potential add-on StarShade occulter. Finally, the traditional geometric optical design is also investigated and traded: reflective versus refractive, telecentric versus non-telecentric relay. The relay before the lenslet array controls the chief angle distribution on the lenslet array. Our previous paper has addressed how the relay design combined with lenslet arraypinhole mask can further compress the residual star light and increase the contrast. Finally, a complete phase A IFS optical design is presented.

Design, fabrication, and delivery of a charge injection device as a stellar tracking device

NASA Technical Reports Server (NTRS)

Burke, H. K.; Michon, G. J.; Tomlinson, H. W.; Vogelsong, T. L.; Grafinger, A.; Wilson, R.

1979-01-01

Six 128 x 128 CID imagers fabricated on bulk silicon and with thin polysilicon upper-level electrodes were tested in a star tracking mode. Noise and spectral response were measured as a function of temperature over the range of +25 C to -40 C. Noise at 0 C and below was less than 40 rms carriers/pixel for all devices at an effective noise bandwidth of 150 Hz. Quantum yield for all devices averaged 40% from 0.4 to 1.0 microns with no measurable temperature dependence. Extrapolating from these performance parameters to those of a large (400 x 400) array and accounting for design and processing improvements, indicates that the larger array would show a further improvement in noise performance -- on the order of 25 carriers. A preliminary evaluation of the projected performance of the 400 x 400 array and a representative set of star sensor requirements indicates that the CID has excellent potential as a stellar tracking device.

Development of an Infrared Lamp Array for the Smap Spacecraft Thermal Balance Test

NASA Technical Reports Server (NTRS)

Miller, Jennifer R.; Emis, Nickolas; Forgette, Daniel

2015-01-01

NASA launched the SMAP observatory in January 2015 aboard a Delta II into a sun-synchronous orbit around Earth. The science payload of a radar and a radiometer utilizes a shared rotating six-meter antenna to provide a global map of the Earth's soil moisture content and its freeze/thaw state on a global, high-resolution scale in this three-year mission. An observatory-level thermal balance test conducted in May/June 2014 validated the thermal design and demonstrated launch readiness as part of the planned environmental test campaign. An infrared lamp array was designed and used in the thermal balance test to replicate solar heating on the solar array and sunlit side of the spacecraft that would normally be seen in orbit. The design, implementation, and operation of an infrared lamp array used for this nineteen-day system thermal test are described in this paper. Instrumental to the smooth operation of this lamp array was a characterization test performed in the same chamber two months prior to the observatory test to provide insight into its array operation and flux uniformity. This knowledge was used to identify the lamp array power settings that would provide the worst case predicted on-orbit fluxes during eclipse, cold, and hot cases. It also showed the lamp array variation when adjustments in flux were needed. Calorimeters calibrated prior to testing determined a relationship between calorimeter temperature and lamp array flux. This allowed the team to adjust the lamp output for the desired absorbed flux on the solar array. Flux levels were within 10% of the desired value at the center of the solar array with an ability to maintain these levels within 5% during steady state cases. All tests demonstrated the infrared lamp array functionality and furthered lamp array understanding for modeling purposes. This method contributed to a high-fidelity environmental simulation, which was required to replicate the extreme on-orbit thermal environments.

Semicustom integrated circuits and the standard transistor array radix (STAR)

NASA Technical Reports Server (NTRS)

Edge, T. M.

1977-01-01

The development, application, pros and cons of the semicustom and custom approach to the integration of circuits are described. Improvements in terms of cost, reliability, secrecy, power, and size reduction are examined. Also presented is the standard transistor array radix, a semicustom approach to digital integrated circuits that offers the advantages of both custom and semicustom approaches to integration.

The CHARA Array Resolves the 1.1 Day Period Spectroscopic Binary HD 146361, the Shortest Period System Resolved To-Date

NASA Astrophysics Data System (ADS)

Raghavan, Deepak; McAlister, H. A.

2007-12-01

We present a visual orbit for the spectroscopic binary, HD 146361, derived from observations at the CHARA Array's long baseline interferometer. The 26 calibrated visibility measurements obtained during May - July 2007 allow us to determine a full orbital solution and component masses for this known spectroscopic binary. The HD 146361 pair has a circular orbit of nearly equal-mass components with a good quality double-lined spectroscopic orbit (Dave Latham, private communication). We have adopted the well-constrained spectroscopic orbital elements and fit the angular semi-major axis, inclination, and longitude of nodes to the binary visibility curve equations. Using these elements and the Hipparcos parallax of 46.11 ± 0.98 mas, we obtain component masses of 1.046 ± 0.084 Msol and 1.000 ± 0.080 Msol. We have planned further observations of this system to reduce the mass uncertainties and may present an updated result at the meeting. This is the shortest period spectroscopic binary resolved as of yet with an interferometer. This work is being done in the context of Raghavan's thesis project, which is a survey of solar-type stars in the solar neighborhood. By completing this survey, we hope to build a comprehensive view of the environments around solar-type stars and improve our understanding of their habitats by analyzing their companions of all types - stars, brown dwarfs, and planets. We have chosen an unbiased, volume-limited sample of 455 primary stars as representatives of the solar-type stars in our Galaxy. Our effort is a modern update to the seminal work of Duquennoy & Mayor (1991) and will contribute to the broader subjects of stellar evolution and planetary system formation, evolution, and stability. Research at the CHARA Array is supported by the College of Arts and Sciences at Georgia State University and by the National Science Foundation through NSF Grant AST 0606958.

The Cold Gas History of the Universe as seen by the ngVLA

NASA Astrophysics Data System (ADS)

Riechers, Dominik A.; Carilli, Chris Luke; Casey, Caitlin; da Cunha, Elisabete; Hodge, Jacqueline; Ivison, Rob; Murphy, Eric J.; Narayanan, Desika; Sargent, Mark T.; Scoville, Nicholas; Walter, Fabian

2017-01-01

The Next Generation Very Large Array (ngVLA) will fundamentally advance our understanding of the formation processes that lead to the assembly of galaxies throughout cosmic history. The combination of large bandwidth with unprecedented sensitivity to the critical low-level CO lines over virtually the entire redshift range will open up the opportunity to conduct large-scale, deep cold molecular gas surveys, mapping the fuel for star formation in galaxies over substantial cosmic volumes. Informed by the first efforts with the Karl G. Jansky Very Large Array (COLDz survey) and the Atacama Large (sub)Millimeter Array (ASPECS survey), we here present initial predictions and possible survey strategies for such "molecular deep field" observations with the ngVLA. These investigations will provide a detailed measurement of the volume density of molecular gas in galaxies as a function of redshift, the "cold gas history of the universe". This will crucially complement studies of the neutral gas, star formation and stellar mass histories with large low-frequency arrays, the Large UV/Optical/Infrared Surveyor, and the Origins Space Telescope, providing the means to obtain a comprehensive picture of galaxy evolution through cosmic times.

Adaptation of a program for nonlinear finite element analysis to the CDC STAR 100 computer

NASA Technical Reports Server (NTRS)

Pifko, A. B.; Ogilvie, P. L.

1978-01-01

The conversion of a nonlinear finite element program to the CDC STAR 100 pipeline computer is discussed. The program called DYCAST was developed for the crash simulation of structures. Initial results with the STAR 100 computer indicated that significant gains in computation time are possible for operations on gloval arrays. However, for element level computations that do not lend themselves easily to long vector processing, the STAR 100 was slower than comparable scalar computers. On this basis it is concluded that in order for pipeline computers to impact the economic feasibility of large nonlinear analyses it is absolutely essential that algorithms be devised to improve the efficiency of element level computations.

Aerosol Optical Depth Value-Added Product for the SAS-He Instrument

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

Ermold, B; Flynn, CJ; Barnard, J

2013-11-27

The Shortwave Array Spectroradiometer – Hemispheric (SAS-He) is a ground-based, shadowband instrument that measures the direct and diffuse solar irradiance. In this regard, the instrument is similar to the Multi-Filter Rotating Shadowband Radiometer (MFRSR) – an instrument that has been in the ARM suite of instruments for more than 15 years. However, the two instruments differ significantly in wavelength resolution and range. In particular, the MFRSR only observes the spectrum in six discrete wavelength channels of about 10 nm width from 415 to 940 nm. The SAS-He, in contrast, incorporates two fiber-coupled grating spectrometers: a Si CCD spectrometer with overmore » 2000 pixels covering the range from 325-1040 nm with ~ 2.5 nm resolution ,and an InGaAs array spectrometer with 256 pixels covering the wavelength range from 960-1700 nm with ~ 6 nm resolution.« less

Other remote sensing systems: Retrospect and outlook

NASA Technical Reports Server (NTRS)

1982-01-01

The history of remote sensing is reviewed and the scope and versatility of the several remote sensing systems already in orbit are discussed, especially those with sensors operating in other EM spectral modes. The multisensor approach is examined by interrelating LANDSAT observations with data from other satellite systems. The basic principles and practices underlying the use of thermal infrared and radar sensors are explored and the types of observations and interpretations emanating from the Nimbus, Heat Capacity Mapping Mission, and SEASAT programs are examined. Approved or proposed Earth resources oriented missions for the 1980's previewed include LANDSAT D, Stereosat, Gravsat, the French satellite SPOT-1, and multimission modular spacecraft launched from space shuttle. The pushbroom imager, the linear array pushbroom radiometer, the multispectral linear array, and the operational LANDSAT observing system, to be designed the LANDSAT-E series are also envisioned for this decade.

Lighting up a Dead Star's Layers

NASA Technical Reports Server (NTRS)

2006-01-01

This image from NASA's Spitzer Space Telescope shows the scattered remains of an exploded star named Cassiopeia A. Spitzer's infrared detectors 'picked' through these remains and found that much of the star's original layering had been preserved.

In this false-color image, the faint, blue glow surrounding the dead star is material that was energized by a shock wave, called the forward shock, which was created when the star blew up. The forward shock is now located at the outer edge of the blue glow. Stars are also seen in blue. Green, yellow and red primarily represent material that was ejected in the explosion and heated by a slower shock wave, called the reverse shock wave.

The picture was taken by Spitzer's infrared array camera and is a composite of 3.6-micron light (blue); 4.5-micron light (green); and 8.0-micron light (red).

Investigating the Early Evolution of Planetary Systems with ALMA and the Next Generation Very Large Array

NASA Astrophysics Data System (ADS)

Ricci, Luca; Liu, Shang-Fei; Isella, Andrea; Li, Hui

2018-02-01

We investigate the potential of the Atacama Large Millimeter/submillimeter Array (ALMA) and the Next Generation Very Large Array (ngVLA) to observe substructures in nearby young disks which are due to the gravitational interaction between disk material and planets close to the central star. We simulate the gas and dust dynamics in the disk using the LA-COMPASS hydrodynamical code. We generate synthetic images for the dust continuum emission at submillimeter to centimeter wavelengths and simulate ALMA and ngVLA observations. We explore the parameter space of some of the main disk and planet properties that would produce substructures that can be visible with ALMA and the ngVLA. We find that ngVLA observations with an angular resolution of 5 milliarcsec at 3 mm can reveal and characterize gaps and azimuthal asymmetries in disks hosting planets with masses down to ≈ 5 {M}\\oplus ≈ 1{--}5 {au} from a solar-like star in the closest star-forming regions, whereas ALMA can detect gaps down to planetary masses of ≈ 20 {M}\\oplus at 5 au. Gaps opened by super-Earth planets with masses ≈ 5{--}10 {M}\\oplus are detectable by the ngVLA in the case of disks with low viscosity (α ∼ {10}-5) and low pressure scale height (h ≈ 0.025 au at 5 au). The ngVLA can measure the proper motion of azimuthal asymmetric structures associated with the disk–planet interaction as well as possible circumplanetary disks on timescales as short as one to a few weeks for planets at 1–5 au from the star.

VLA AND ALMA IMAGING OF INTENSE GALAXY-WIDE STAR FORMATION IN z ∼ 2 GALAXIES

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

Rujopakarn, W.; Silverman, J. D.; Dunlop, J. S.

2016-12-10

We present ≃0.″4 resolution extinction-independent distributions of star formation and dust in 11 star-forming galaxies (SFGs) at z  = 1.3–3.0. These galaxies are selected from sensitive blank-field surveys of the 2′ × 2′ Hubble Ultra-Deep Field at λ  = 5 cm and 1.3 mm using the Karl G. Jansky Very Large Array and Atacama Large Millimeter/submillimeter Array. They have star formation rates (SFRs), stellar masses, and dust properties representative of massive main-sequence SFGs at z  ∼ 2. Morphological classification performed on spatially resolved stellar mass maps indicates a mixture of disk and morphologically disturbed systems; half of the sample harbor X-ray active galactic nuclei (AGNs),more » thereby representing a diversity of z  ∼ 2 SFGs undergoing vigorous mass assembly. We find that their intense star formation most frequently occurs at the location of stellar-mass concentration and extends over an area comparable to their stellar-mass distribution, with a median diameter of 4.2 ± 1.8 kpc. This provides direct evidence of galaxy-wide star formation in distant blank-field-selected main-sequence SFGs. The typical galactic-average SFR surface density is 2.5 M {sub ⊙} yr{sup −1} kpc{sup −2}, sufficiently high to drive outflows. In X-ray-selected AGN where radio emission is enhanced over the level associated with star formation, the radio excess pinpoints the AGNs, which are found to be cospatial with star formation. The median extinction-independent size of main-sequence SFGs is two times larger than those of bright submillimeter galaxies, whose SFRs are 3–8 times larger, providing a constraint on the characteristic SFR (∼300 M {sub ⊙} yr{sup −1}) above which a significant population of more compact SFGs appears to emerge.« less

The EarthCARE mission BBR instrument: ground testing of radiometric performance

NASA Astrophysics Data System (ADS)

Caldwell, Martin E.; Spilling, David; Grainger, William; Theocharous, E.; Whalley, Martin; Wright, Nigel; Ward, Anthony K.; Jones, Edward; Hampton, Joseph; Parker, David; Delderfield, John; Pearce, Alan; Richards, Anthony G.; Munro, Grant J.; Poynz Wright, Oliver; Hampson, Matthew; Forster, David

2017-09-01

In the EarthCARE mission the BBR (Broad Band Radiometer) has the role of measuring the net earth radiance (i.e. total reflected-solar and thermally-emitted radiances), from the same earth scene as viewed by the other instruments (aerosol lidar, cloud radar and spectral imager). It does this measurement at 10km scene size and in 3 view angles. It is an imaging radiometer in that it uses micro-bolometer linear-array detector (pushbroom orientation), to over-sample these required scenes, with the samples being binned on-ground to produce the 10km radiance data. For the measurements of total earth radiance, the BBR is based on the heritage of Earth Radiation Budget (ERB) instruments. The ground calibration methods of this type of sensor is technically very similar to other EO instruments that measure in the thermalIR, but with added challenges: (1) The thermal-IR measurement has to have a much wider spectral range than normal thermal-IR channels to cover the whole earth-emission spectrum i.e. 4 to >50microns (2) The 2nd channel (reflected solar radiance) must also have a broad response to cover almost the whole solar spectrum, i.e. 0.3 to 4microns. And this solar channel must be measured on the same radiometric calibration as the thermal channel, which in practice is best done by using the same radiometer for both channels. The radiometer is designed to be very broad-band i.e. 0.3 to 50microns (i.e. more than two decades), to cover both ranges, and a switchable spectral filter (short-pass cutoff at 4μm) is used to separate the channels. The on-ground measurements which are required to link the calibration of these channels will be described. A calibration of absolute responsivity in each of the two bands is needed; in the thermal-IR channel this is by the normal method of using a calibrated blackbody test source, and in the solar channel it is by means of a narrow-band (laser) and a reference radiometer (from NPL). A calibration of relative spectral response is also needed, across this wide range, for the purpose of linking the two channels, and for converting the narrow-band solar channel measurement to broad-band.

Effect of Forest Canopy on Remote Sensing Soil Moisture at L-band

NASA Technical Reports Server (NTRS)

LeVine, D. M.; Lang, R. H.; Jackson, T. J.; Haken, M.

2005-01-01

Global maps of soil moisture are needed to improve understanding and prediction of the global water and energy cycles. Accuracy requirements imply the use of lower frequencies (L-band) to achieve adequate penetration into the soil and to minimize attenuation by the vegetation canopy and effects of surface roughness. Success has been demonstrated over agricultural areas, but canopies with high biomass (e.g. forests) still present a challenge. Examples from recent measurements over forests with the L-band radiometer, 2D-STAR, and its predecessor, ESTAR, will be presented to illustrate the problem. ESTAR and 2D-STAR are aircraft-based synthetic aperture radiometers developed to help resolve both the engineering and algorithm issues associated with future remote sensing of soil moisture. ESTAR, which does imaging across track, was developed to demonstrate the viability of aperture synthesis for remote sensing. The instrument has participated several soil moisture experiments (e.g. at the Little Washita Watershed in 1992 and the Southern Great Plains experiments in 1997 and 1999). In addition, measurements have been made at a forest site near Waverly, VA which contains conifer forests with a variety of biomass. These data have demonstrated the success of retrieving soil moisture at L-band over agricultural areas and the response of passive observations at L-band to biomass over forests. 2D-STAR is a second generation instrument that does aperture synthesis in two dimensions (along track and cross track) and is dual polarized. This instrument has the potential to provide measurements at L-band that simulate the measurements that will be made by the two L-band sensors currently being developed for future remote sensing of soil moisture from space: Hydros (conical scan and real aperture) and SMOS (multiple incidence angle and synthetic aperture). 2D-STAR participated in the SMEX-03 soil moisture experiment, providing images from the NASA P-3 aircraft. Preliminary results include images of the experiment site area near Huntsville, AL that included a mixture of forest and agriculture. Changes during a rain event further illustrate the issues presented by forests. Work is continuing to reduce the 2D-STAR data and to support the two future remote sensing missions. Among the goals is to process the 2D-STAR data to create multiple looks (at the same pixel) with different incidence angles. Data in this format can be used to test algorithms for retrieving soil moisture and biomass such as are planned for SMOS. Also, the data are being processed to provide images at constant incidence angles such as will be obtained by Hydros. Although Hydros will have only one incidence angle, it will also carry an L-band radar, The goal is to use the radar to improve spatial resolution, an issue for remote sensing from space at the long wavelengths. Simultaneous observations with active and passive sensors also offers interesting prospects for treating areas of high biomass (forests) and irregular terrain and may be the challenge for the future.

Radio SETI Observations of the Anomalous Star KIC 8462852

NASA Astrophysics Data System (ADS)

Harp, G. R.; Richards, Jon; Shostak, Seth; Tarter, J. C.; Vakoch, Douglas A.; Munson, Chris

2016-07-01

We report on a search for the presence of signals from extraterrestrial intelligence in the direction of the star system KIC 8462852. Observations were made at radio frequencies between 1 and 10 GHz using the Allen Telescope Array. No narrowband radio signals were found at a level of 180-300 Jy in a 1 Hz channel, or medium band signals above 10 Jy in a 100 kHz channel.

Mechanistic Selection and Growth of Twinned Bicrystalline Primary Si in Near Eutectic Al-Si Alloys

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

Jung, Choonho

2006-01-01

Morphological evolution and selection of angular primary silicon is investigated in near-eutectic Al-Si alloys. Angular silicon arrays are grown directionally in a Bridgman furnace at velocities in the regime of 10 -3 m/sec and with a temperature gradient of 7.5 x 10 3 K/m. Under these conditions, the primary Si phase grows as an array of twinned bicrystalline dendrites, where the twinning gives rise to a characteristic 8-pointed star-shaped primary morphology. While this primary Si remains largely faceted at the growth front, a complex structure of coherent symmetric twin boundaries enables various adjustment mechanisms which operate to optimize the characteristicmore » spacings within the primary array. In the work presented here, this primary silicon growth morphology is examined in detail. In particular, this thesis describes the investigation of: (1) morphological selection of the twinned bicrystalline primary starshape morphology; (2) primary array behavior, including the lateral propagation of the starshape grains and the associated evolution of a strong <100> texture; (3) the detailed structure of the 8-pointed star-shaped primary morphology, including the twin boundary configuration within the central core; (4) the mechanisms of lateral propagation and spacing adjustment during array evolution; and (5) the thermosolutal conditions (i.e. operating state) at the primary growth front, including composition and phase fraction in the vicinity of the primary tip.« less

The unexpectedly large proportion of high-mass star-forming cores in a Galactic mini-starburst

NASA Astrophysics Data System (ADS)

Motte, F.; Nony, T.; Louvet, F.; Marsh, K. A.; Bontemps, S.; Whitworth, A. P.; Men'shchikov, A.; Nguyáën Luong, Q.; Csengeri, T.; Maury, A. J.; Gusdorf, A.; Chapillon, E.; Könyves, V.; Schilke, P.; Duarte-Cabral, A.; Didelon, P.; Gaudel, M.

2018-04-01

Understanding the processes that determine the stellar initial mass function (IMF) is a critical unsolved problem, with profound implications for many areas of astrophysics1. In molecular clouds, stars are formed in cores—gas condensations sufficiently dense that gravitational collapse converts a large fraction of their mass into a star or small clutch of stars. In nearby star-formation regions, the core mass function (CMF) is strikingly similar to the IMF, suggesting that the shape of the IMF may simply be inherited from the CMF2-5. Here, we present 1.3 mm observations, obtained with the Atacama Large Millimeter/submillimeter Array telescope, of the active star-formation region W43-MM1, which may be more representative of the Galactic-arm regions where most stars form6,7. The unprecedented resolution of these observations reveals a statistically robust CMF at high masses, with a slope that is markedly shallower than the IMF. This seriously challenges our understanding of the origin of the IMF.

The unexpectedly large proportion of high-mass star-forming cores in a Galactic mini-starburst

NASA Astrophysics Data System (ADS)

Motte, F.; Nony, T.; Louvet, F.; Marsh, K. A.; Bontemps, S.; Whitworth, A. P.; Men'shchikov, A.; Nguyen Luong, Q.; Csengeri, T.; Maury, A. J.; Gusdorf, A.; Chapillon, E.; Könyves, V.; Schilke, P.; Duarte-Cabral, A.; Didelon, P.; Gaudel, M.

2018-06-01

Understanding the processes that determine the stellar initial mass function (IMF) is a critical unsolved problem, with profound implications for many areas of astrophysics1. In molecular clouds, stars are formed in cores—gas condensations sufficiently dense that gravitational collapse converts a large fraction of their mass into a star or small clutch of stars. In nearby star-formation regions, the core mass function (CMF) is strikingly similar to the IMF, suggesting that the shape of the IMF may simply be inherited from the CMF2-5. Here, we present 1.3 mm observations, obtained with the Atacama Large Millimeter/submillimeter Array telescope, of the active star-formation region W43-MM1, which may be more representative of the Galactic-arm regions where most stars form6,7. The unprecedented resolution of these observations reveals a statistically robust CMF at high masses, with a slope that is markedly shallower than the IMF. This seriously challenges our understanding of the origin of the IMF.

Eight to 14 μm spectral monitoring of long period variable stars with GLADYS.

NASA Astrophysics Data System (ADS)

Levan, P. D.; Sloan, G.; Grasdalen, G.

The authors describe an ongoing program of spectral monitoring of long period variable stars using GLADYS, a long slit prism spectrometer that employs a 58x62 pixel Si:Ga detector array. The goal is to compare the equivalent widths of the SiC emission features in carbon-rich circumstellar shells, and the silicate emission features in oxygen-rich circumstellar stars, obtained over different phases of the continuum variability cycle. Spectra of long period variables and low amplitude variables recently obtained on the Wyoming Infrared Observatory 2.3 m telescope are presented.

Technique for Radiometer and Antenna Array Calibration - TRAAC

NASA Technical Reports Server (NTRS)

Meyer, Paul; Sims, William; Varnavas, Kosta; McCracken, Jeff; Srinivasan, Karthik; Limaye, Ashutosh; Laymon, Charles; Richeson. James

2012-01-01

Highly sensitive receivers are used to detect minute amounts of emitted electromagnetic energy. Calibration of these receivers is vital to the accuracy of the measurements. Traditional calibration techniques depend on calibration reference internal to the receivers as reference for the calibration of the observed electromagnetic energy. Such methods can only calibrate errors in measurement introduced by the receiver only. The disadvantage of these existing methods is that they cannot account for errors introduced by devices, such as antennas, used for capturing electromagnetic radiation. This severely limits the types of antennas that can be used to make measurements with a high degree of accuracy. Complex antenna systems, such as electronically steerable antennas (also known as phased arrays), while offering potentially significant advantages, suffer from a lack of a reliable and accurate calibration technique. The proximity of antenna elements in an array results in interaction between the electromagnetic fields radiated (or received) by the individual elements. This phenomenon is called mutual coupling. The new calibration method uses a known noise source as a calibration load to determine the instantaneous characteristics of the antenna. The noise source is emitted from one element of the antenna array and received by all the other elements due to mutual coupling. This received noise is used as a calibration standard to monitor the stability of the antenna electronics.

Faint Submillimeter Galaxies Behind Lensing Clusters

NASA Astrophysics Data System (ADS)

Hsu, Li-Yen; Lauchlan Cowie, Lennox; Barger, Amy J.; Desai, Vandana; Murphy, Eric J.

2017-01-01

Faint submillimeter galaxies are the major contributors to the submillimeter extragalactic background light and hence the dominant star-forming population in the dusty universe. Determining how much these galaxies overlap the optically selected samples is critical to fully account for the cosmic star formation history. Observations of massive cluster fields are the best way to explore this faint submillimeter population, thanks to gravitational lensing effects. We have been undertaking a lensing cluster survey with the SCUBA-2 camera on the James Clerk Maxwell Telescope to map nine galaxy clusters, including the northern five clusters in the HST Frontier Fields program. We have also been using the Submillimeter Array and the Very Large Array to determine the accurate positions of our detected sources. Our observations have discovered high-redshift dusty galaxies with far-infrared luminosities similar to that of the Milky Way or luminous infrared galaxies. Some of these galaxies are still undetected in deep optical and near-infrared images. These results suggest that a substantial amount of star formation in even the faint submillimeter population may be hidden from rest-frame optical surveys.

The Nuclear Spectroscopic Telescope Array (NuSTAR)

NASA Technical Reports Server (NTRS)

Harrison, Fiona A.; Boggs, Steven; Christensen, Finn; Craig, William; Hailey, Charles; Stern, Daniel; Zhang, William; Angelini, Lorella; An, Hong Jun; Bhalereo, Varun;

The Importance of High Frequency Observations for the SKA

NASA Astrophysics Data System (ADS)

Welch, William J.

2007-12-01

The plan for the Square Kilometer Array (SKA) is one or more very large arrays operating in two or more contiguous frequency bands: roughly 15 - 90 MHz, 120 - 500 MHz, and 500 MHz - 25 GHz. The last band may be further divided into roughly 500 MHz - 1.5 GHz and 1.5 - 25 GHz. Construction costs may delay or forgo one or more of these bands. We argue that the entire high frequency band is of special importance for astronomy both in the local universe and at great distances and early times. One of the Key Science Projects, the Cradle of Life, requires high sensitivity and resolution at frequencies up to 20 GHz for the study of forming disks around new stars with disk opacities too great for millimeter wave observations. The larger issue of star formation, a poorly understood area, will also benefit from high sensitivity observations at short cm wavelengths. Magnetic field measurements through the Zeeman effect in the densest star forming gas are best done using tracers such as CCS at frequencies of 11 and 22 GHz. The wide frequency range of the SKA permits the observation of multiple rotational transitions of long chain molecules, providing accurate measures of both gas densities and temperatures. The wide field of view will permit large scale surveys of entire star forming clouds revealing, at high resolution, the formation of clusters of pre-protostellar stars and class 0-2 protostars in line radiation. The continuum cm wave radiation will reveal the growth of grains in disks. On the larger scale, observations of CO at high redshifts will trace the evolution of star formation and the formation of metals back to the Epic of Reionization.

AB Dor Moving Group Stars Resolved with the CHARA Array

NASA Astrophysics Data System (ADS)

Schaefer, G. H.; White, R. J.; Baines, E. K.; Boyajian, T. S.; ten Brummelaar, T. A.; Farrington, C. D.; Sturmann, J.; Sturmann, L.; Turner, N. H.

2018-05-01

We present interferometric measurements obtained with the CHARA Array of 13 adolescent-age stars in nearby moving groups. The motivation was to spatially resolve the largest stars and to search for binary companions. Nine stars have diameters smaller than the resolution limit and no evidence for companions within 0.5–50 mas and ΔH < 2.0 mag. The diameters of three stars were spatially resolved: GJ 159 (0.582 ± 0.016 mas) and GJ 393 (0.564 ± 0.021 mas) in the AB Dor moving group, and former member HD 89744 (0.556 ± 0.032 mas). Combining the angular diameters with their distances and bolometric fluxes, we measured radii and effective temperatures. The temperatures of GJ 159 (6286 ± 123 K) and GJ 393 (3515 ± 68 K) are consistent with spectroscopic measurements. Comparisons with evolutionary models show that HD 89744 has evolved off the main sequence. GJ 159 and GJ 393 lie within 1.5σ of the zero-age main sequence, complicating their age estimates because it is unclear whether the stars are contracting or expanding. GJ 159 has a mass of 1.2 ± 0.1 {M}ȯ with an age spanning 0.021–3.0 Gyr. Its debris disk and lithium abundance favor a young age. GJ 393 has a mass of 0.42 ± 0.03 {M}ȯ and a lower limit on its age 0.06 Gyr. This overlaps with the age of the moving group; however, an older age would be more consistent with its slow rotation, low activity, and luminosity, suggesting that GJ 393 is a kinematic interloper.

Characterization of a Compact Water Vapor Radiometer

NASA Astrophysics Data System (ADS)

Gill, Ajay; Selina, Rob

2018-01-01

We report on laboratory test results of the Compact Water Vapor Radiometer (CWVR) prototype for the Karl G. Jansky Very Large Array (VLA), a five-channel design centered around the 22 GHz water vapor line. Fluctuations in perceptible water vapor cause fluctuations in atmospheric brightness emission, which are assumed to be proportional to phase fluctuations of the astronomical signal seen by an antenna. The design is intended to support empirical radiometric phase corrections for each baseline in the array.The dynamic range, channel isolation, and gain stability of the device were characterized. The device has a useful dynamic range of order 18 dB after calibration, and the CWVR channel isolation requirement of < -20 dB is met.For the gain stability test, the diode detectors were operated in the square-law region, and a K-band noise diode was used as the broadband input power source to the CWVR over a period of 64 hours. Results indicate that the fluctuations in output counts are negatively correlated to the CWVR enclosure ambient temperature, with a change of ~ 405 counts per 1° C change in temperature.A correction for the CWVR ambient temperature makes a considerable improvement in stability for τ > 102.6 sec. With temperature corrections, the single channel and channel difference gain stability per channel is < 2 x 10-4 over τ = 2.5 - 103 sec, which meets the < 2 x 10-4 requirement. The observable gain stability is < 2.5 x 10-4 over τ = 2.5 - 103 sec, which meets the < 2.5 x 10-4 requirement.Overall, the test results indicate that the CWVR meets required specifications for dynamic range, channel isolation, and gain stability in order to proceed with testing on a pair of VLA antennas.

ALMA Compact Array observations of the Fried Egg nebula: Evidence for large-scale asymmetric mass-loss from the yellow hypergiant IRAS 17163-3907.

PubMed

Wallström, S H J; Lagadec, E; Muller, S; Black, J H; Cox, N L J; Galván-Madrid, R; Justtanont, K; Longmore, S; Olofsson, H; Oudmaijer, R D; Quintana-Lacaci, G; Szczerba, R; Vlemmings, W; van Winckel, H; Zijlstra, A

2017-01-10

Yellow hypergiants are rare and represent a fast evolutionary stage of massive evolved stars. That evolutionary phase is characterised by a very intense mass loss, the understanding of which is still very limited. Here we report ALMA Compact Array observations of a 50″-mosaic toward the Fried Egg nebula, around one of the few Galactic yellow hypergiants IRAS 17163-3907. The emission from the 12 CO J=2-1 line, H30 α recombination line, and continuum is imaged at a resolution of ~8″, revealing the morphology of the molecular environment around the star. The continuum emission is unresolved and peaks at the position of the star. The radio recombination line H30 α shows unresolved emission at the star, with an approximately gaussian spectrum centered on a velocity of 21±3 km s -1 with a width of 57±6 km s -1 . In contrast, the CO 2-1 emission is complex and decomposes into several components beyond the contamination from interstellar gas in the line of sight. The CO spectrum toward the star is a broad plateau, centered at the systemic velocity of +18 km s -1 and with an expansion velocity of 100±10 km s -1 . Assuming isotropic and constant mass-loss, we estimate a mass-loss rate of 8±1.5 ×10 -5 M ⊙ yr -1 . At a radius of 25″ from the star, we detect CO emission associated with the dust ring previously imaged by Herschel . The kinematics of this ring, however, is not consistent with an expanding shell, but show a velocity gradient of v sys ±20 km s -1 . In addition, we find a puzzling bright feature radially connecting the star to the CO ring, at a velocity of +40 km s -1 relative to the star. This spur feature may trace a unidirectional ejection event from the star. Our ACA observations reveal the complex morphology around IRAS 17163 and illustrate the breakthroughs that ALMA will bring to the field of massive stellar evolution.

ALMA Compact Array observations of the Fried Egg nebula: Evidence for large-scale asymmetric mass-loss from the yellow hypergiant IRAS 17163-3907

PubMed Central

Wallström, S.H.J.; Lagadec, E.; Muller, S.; Black, J.H.; Cox, N.L.J.; Galván-Madrid, R.; Justtanont, K.; Longmore, S.; Olofsson, H.; Oudmaijer, R.D.; Quintana-Lacaci, G.; Szczerba, R.; Vlemmings, W.; van Winckel, H.; Zijlstra, A.

2017-01-01

Yellow hypergiants are rare and represent a fast evolutionary stage of massive evolved stars. That evolutionary phase is characterised by a very intense mass loss, the understanding of which is still very limited. Here we report ALMA Compact Array observations of a 50″-mosaic toward the Fried Egg nebula, around one of the few Galactic yellow hypergiants IRAS 17163-3907. The emission from the 12CO J=2-1 line, H30α recombination line, and continuum is imaged at a resolution of ~8″, revealing the morphology of the molecular environment around the star. The continuum emission is unresolved and peaks at the position of the star. The radio recombination line H30α shows unresolved emission at the star, with an approximately gaussian spectrum centered on a velocity of 21±3 km s−1 with a width of 57±6 km s−1. In contrast, the CO 2-1 emission is complex and decomposes into several components beyond the contamination from interstellar gas in the line of sight. The CO spectrum toward the star is a broad plateau, centered at the systemic velocity of +18 km s−1 and with an expansion velocity of 100±10 km s−1. Assuming isotropic and constant mass-loss, we estimate a mass-loss rate of 8±1.5 ×10−5 M⊙ yr−1. At a radius of 25″ from the star, we detect CO emission associated with the dust ring previously imaged by Herschel. The kinematics of this ring, however, is not consistent with an expanding shell, but show a velocity gradient of vsys±20 km s−1. In addition, we find a puzzling bright feature radially connecting the star to the CO ring, at a velocity of +40 km s−1 relative to the star. This spur feature may trace a unidirectional ejection event from the star. Our ACA observations reveal the complex morphology around IRAS 17163 and illustrate the breakthroughs that ALMA will bring to the field of massive stellar evolution. PMID:28190887

Socket stars: UBVRJIK radial profiles

NASA Astrophysics Data System (ADS)

Schaefer, Bradley E.

1995-05-01

Visual inspectin of stars embedded in H II nebulae has shown a significant fraction to be surrounded by nearly symmetric extended regions within which the nebular brightness is apparently significantly fainter than is typical for the surrounding area. These 'socket stars' might be caused by a bubble in the nebula blown out by a stellar wind or they might be caused by a circumstellar envelope of dust hiding the emission behind the star. As such, the sockets could be the first manifestation of a previously unknown component of pre-main-sequence stars. Unfortunately, no quantitative proof of the existence of sockets has been presented. To fill this need, I have imaged 10 socket stars and six background stars with CCD cameras and infrared array cameras. From these images, I have constructed radial plots which should reveal dips in brightness immediately outside the seeing disk. The radial plots do not show any evidence for the existence of sockets. A detailed examination of the photographs orginally used to identify the sockets show that the causes of these reports are (1) artifacts resulting from the photographic process of dodging and (2) random coincidence of stars with local minima in nebular brightness. Thus, I conclude that 'socket stars' do not exist.

The Challenges of Low-Frequency Radio Polarimetry: Lessons from the Murchison Widefield Array

NASA Astrophysics Data System (ADS)

Lenc, E.; Anderson, C. S.; Barry, N.; Bowman, J. D.; Cairns, I. H.; Farnes, J. S.; Gaensler, B. M.; Heald, G.; Johnston-Hollitt, M.; Kaplan, D. L.; Lynch, C. R.; McCauley, P. I.; Mitchell, D. A.; Morgan, J.; Morales, M. F.; Murphy, Tara; Offringa, A. R.; Ord, S. M.; Pindor, B.; Riseley, C.; Sadler, E. M.; Sobey, C.; Sokolowski, M.; Sullivan, I. S.; O'Sullivan, S. P.; Sun, X. H.; Tremblay, S. E.; Trott, C. M.; Wayth, R. B.

2017-09-01

We present techniques developed to calibrate and correct Murchison Widefield Array low-frequency (72-300 MHz) radio observations for polarimetry. The extremely wide field-of-view, excellent instantaneous (u, v)-coverage and sensitivity to degree-scale structure that the Murchison Widefield Array provides enable instrumental calibration, removal of instrumental artefacts, and correction for ionospheric Faraday rotation through imaging techniques. With the demonstrated polarimetric capabilities of the Murchison Widefield Array, we discuss future directions for polarimetric science at low frequencies to answer outstanding questions relating to polarised source counts, source depolarisation, pulsar science, low-mass stars, exoplanets, the nature of the interstellar and intergalactic media, and the solar environment.

Multiwavelength pulse oximetry in the measurement of hemoglobin fractions

NASA Astrophysics Data System (ADS)

Manzke, Bernd; Schwider, Johannes; Lutter, Norbert O.; Engelhardt, Kai; Stork, Wilhelm

1996-04-01

The two wavelength design of the majority of pulse oximeters assumes only two absorbing hemoglobin fractions, oxyhemoglobin (O2Hb), and reduced hemoglobin (HHb) irrespective of the presence of methemoglobin (MetHb) and carboxyhemoglobin (COHb). If MetHb or COHb is present, it contributes to the pulse-added absorbance signal and will be interpreted as either HHb or O2Hb or some combination of the two. In this paper we describe a noninvasive multi-wavelength pulse oximeter measuring O2Hb, HHb, MetHb, and COHb at a specified accuracy of 1.0%. The system was designed with respect to the results of numerical simulations. It consists of 9 laserdiodes (LDs) and 7 light emitting diodes (LEDs), a 16-bit analog-digital converter (ADC) and has a sampling rate of 16 kHz. The laser didoes and LEDs were coupled into multi-mode fibers and led with a liquid lightguide to the finger clip and then the photodiode. It also presents the results of a clinical study, including a setup with a quartz tungsten halogen lamp (with fiber output) and a diode array spectrometer, a standard pulse oximeter and two in-vitro oximeters (radiometer OSM3 and radiometer ABL 520) as references.

Stellar Snowflake Cluster

NASA Image and Video Library

2005-12-22

Newborn stars, hidden behind thick dust, are revealed in this image of a section of the Christmas Tree cluster from NASA Spitzer Space Telescope, created in joint effort between Spitzer infrared array camera and multiband imaging photometer instrument

The First Focused Hard X-Ray Images of the Sun with NuSTAR

NASA Technical Reports Server (NTRS)

Grefenstette, Brian W.; Glesener, Lindsay; Kruckner, Sam; Hudson, Hugh; Hannah, Iain G.; Smith, David M.; Vogel, Julia K.; White, Stephen M.; Madsen, Kristin K.; Marsh, Andrew J.;

VizieR Online Data Catalog: Massive stars in 30 Dor (Schneider+, 2018)

NASA Astrophysics Data System (ADS)

Schneider, F. R. N.; Sana, H.; Evans, C. J.; Bestenlehner, J. M.; Castro, N.; Fossati, L.; Grafener, G.; Langer, N.; Ramirez-Agudelo, O. H.; Sabin-Sanjulian, C.; Simon-Diaz, S.; Tramper, F.; Crowther, P. A.; de Koter, A.; de Mink, S. E.; Dufton, P. L.; Garcia, M.; Gieles, M.; Henault-Brunet, V.; Herrero, A.; Izzard, R. G.; Kalari, V.; Lennon, D. J.; Apellaniz, J. M.; Markova, N.; Najarro, F.; Podsiadlowski, P.; Puls, J.; Taylor, W. D.; van Loon, J. T.; Vink, J. S.; Norman, C.

2018-02-01

Through the use of the Fibre Large Array Multi Element Spectrograph (FLAMES) on the Very Large Telescope (VLT), the VLT-FLAMES Tarantula Survey (VFTS) has obtained optical spectra of ~800 massive stars in 30 Dor, avoiding the core region of the dense star cluster R136 because of difficulties with crowding. Repeated observations at multiple epochs allow determination of the orbital motion of potentially binary objects. For a sample of 452 apparently single stars, robust stellar parameters-such as effective temperatures, luminosities, surface gravities, and projected rotational velocities-are determined by modeling the observed spectra. Composite spectra of visual multiple systems and spectroscopic binaries are not considered here because their parameters cannot be reliably inferred from the VFTS data. To match the derived atmospheric parameters of the apparently single VFTS stars to stellar evolutionary models, we use the Bayesian code Bonnsai. (2 data files).

New View of Distant Galaxy Reveals Furious Star Formation

NASA Astrophysics Data System (ADS)

2007-12-01

A furious rate of star formation discovered in a distant galaxy shows that galaxies in the early Universe developed either much faster or in a different way from what astronomers have thought. "This galaxy is forming stars at an incredible rate," said Wei-Hao Wang, an astronomer at the National Radio Astronomy Observatory (NRAO) in Socorro, New Mexico. The galaxy, Wang said, is forming the equivalent of 4,000 Suns a year. This is a thousand times more violent than our own Milky Way Galaxy. Location of Distant Galaxy Visible-light, left (from HST) and Infrared, right, (from Spitzer) Images: Circles indicate location of GOODS 850-5. CREDIT: Wang et al., STScI, Spitzer, NASA, NRAO/AUI/NSF Click on image for high-resolution file (1 MB) The galaxy, called GOODS 850-5, is 12 billion light-years from Earth, and thus is seen as it was only about 1.5 billion years after the Big Bang. Wang and his colleagues observed it using the Smithsonian Astrophysical Observatory's Submillimeter Array (SMA) on Mauna Kea in Hawaii. Young stars in the galaxy were enshrouded in dust that was heated by the stars and radiated infrared light strongly. Because of the galaxy's great distance from Earth, the infrared light waves have been stretched out to submillimeter-length radio waves, which are seen by the SMA. The waves were stretched or "redshifted," as astronomers say, by the ongoing expansion of the Universe. "This evidence for prolific star formation is hidden by the dust from visible-light telescopes," Wang explained. The dust, in turn, was formed from heavy elements that had to be built up in the cores of earlier stars. This indicates, Wang said, that significant numbers of stars already had formed, then spewed those heavy elements into interstellar space through supernova explosions and stellar winds. "Seeing the radiation from this heated dust revealed star formation we could have found in no other way," Wang said. Similar dusty galaxies in the early Universe may contain most of the star formation at those times. "This means that future telescopes such as the Atacama Large Millimeter/submillimeter Array (ALMA) can reveal many more such galaxies and give us a much more complete picture of star formation in the early Universe," he added. Lennox Cowie of the University of Hawaii said, "We found out in the last decade that most of the recent star formation in the Universe occurs in large dusty galaxies, but we had always expected that early star formation would be dominated by smaller and less obscured galaxies. Now it seems that even at very early times it may be the same big dusty star formers that are the sites of most of the star formation. That's quite a surprise." Astronomers believe that large galaxies originally formed through mergers of smaller objects. Seeing a large galaxy such as GOODS 850-5 forming stars so rapidly at such an early time in the history of the Universe is a surprise. "Either the mergers that formed the galaxy happened much faster than we thought or some other process altogether produced the galaxy," Wang said. Wang and Cowie worked with Jennifer van Saders of Rutgers University and NRAO, Amy Barger of the University of Wisconsin-Madison, and Jonathan Williams of the University of Hawaii. The scientists published their findings in the December 1 edition of the Astrophysical Journal. The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.The Submillimeter Array is an 8-element interferometer located atop Mauna Kea in Hawaii. It is a collaboration between the Smithsonian Astrophysical Observatory and the Institute of Astronomy and Astrophysics of the Academia Sinica of Taiwan.

Teaching Psychopathology in a Galaxy Far, Far Away: The Light Side of the Force.

PubMed

Friedman, Susan Hatters; Hall, Ryan C W

2015-12-01

Star Wars films are among the top box office hits of all time. The films have been popular internationally for almost 40 years. As such, both trainees and attending psychiatrists are likely to be aware of them. This article highlights a vast array of psychopathology in Star Wars films which can be useful in teaching, even when the characters are considered the "good guys". Included are as follows: histrionic, obsessive-compulsive, and dependent personality traits, perinatal psychiatric disorders, prodromal schizophrenia, pseudo-dementia, frontal lobe lesions, pathological gambling, and even malingering. As such, Star Wars has tremendous potential to teach psychiatric trainees about mental health issues.

Measurements of stratospheric composition using a star pointing spectrometer

NASA Technical Reports Server (NTRS)

Fish, Deb J.; Jones, Rod L.; Freshwater, Ray A.; Roscoe, Howard K.; Oldham, Derek J.

1994-01-01

Measurements of stratospheric composition have been made with a novel star-pointing spectrometer. The instrument consists of a telescope that focuses light from stars, planets, or the moon onto a spectrometer and two dimensional CCD array detector. Atmospheric absorptions can be measured, from which atmospheric columns of several gases can be determined. The instrument was deployed in Abisko, 69 deg N, during the European Arctic Stratospheric Ozone Experiment (EASOE). The instrument has the potential for measuring O3, OClO, NO2, and NO3. In this paper, a method for the retrieval of vertical columns is described, and some examples of ozone measurements given.

IOTA: recent science and technology

NASA Astrophysics Data System (ADS)

Schloerb, F. Peter; Berger, J.-P.; Carleton, N. P.; Hagenauer, P.; Kern, P. Y.; Labeye, P. R.; Lacasse, M. G.; Malbet, F.; Millan-Gabet, R.; Monnier, J. D.; Pearlman, M. R.; Pedretti, E.; Rousselet-Perraut, K.; Ragland, S. D.; Schuller, P. A.; Traub, W. A.; Wallace, G.

2006-06-01

We present a brief review of recent scientific and technical advances at the Infrared Optical Telescope Array (IOTA). IOTA is a long-baseline interferometer located atop Mount Hopkins, Arizona. Recent work has emphasized the use of the three-telescope interferometer completed in 2002. We report on results obtained on a range of scientific targets, including AGB stars, Herbig AeBe Stars, binary stars, and the recent outburst of the recurrent nova RS Oph. We report the completion of a new spectrometer which allows visibility measurements at several high spectral resolution channels simultaneously. Finally, it is our sad duty to report that IOTA will be closed this year.

CCD Centroiding Experiment for Correcting a Distorted Image on the Focal Plane

NASA Astrophysics Data System (ADS)

Yano, Taihei; Araki, Hiroshi; Gouda, Naoteru; Kobayashi, Yukiyasu; Tsujimoto, Takuji; Nakajima, Tadashi; Kawano, Nobuyuki; Tazawa, Seiichi; Yamada, Yoshiyuki; Hanada, Hideo; Asari, Kazuyoshi; Tsuruta, Seiitsu

2006-10-01

JASMINE (Japan Astrometry Satellite Mission for Infrared Exploration) and ILOM (In situ Lunar Orientation Measurement) are space missions that are in progress at the National Astronomical Observatory of Japan. These two projects require a common astrometric technique to obtain precise positions of star images on solid-state detectors in order to accomplish their objectives. In the laboratory, we have carried out measurements of the centroid of artificial star images on a CCD array in order to investigate the precision of the positions of the stars, using an algorithm for estimating them from photon-weighted means of the stars. In the calibration of the position of a star image at the focal plane, we have also taken into account the lowest order distortion due to optical aberrations, which is proportional to the cube of the distance from the optical axis. Accordingly, we find that the precision of the measurement for the positions of the stars reaches below 1/100 pixel for one measurement.

Correlated Si isotope anomalies and large C-13 enrichments in a family of exotic SiC grains

NASA Technical Reports Server (NTRS)

Stone, J.; Hutcheon, I. D.; Epstein, S.; Wasserburg, G. J.

1991-01-01

A hypothesis is presented to the effect that the distinctive morphological characteristics and comparatively simple Si isotope systematics identify the platy SiC crystals as a genetically related family, formed around a single isotopically heterogeneous presolar star on an association of related stars. The enrichments in C-13 and the Si isotope systematics of the platy SiC are broadly consistent with theoretical models of nucleosynthesis in low-mass, carbon stars on the ASG. The Si isotope array most plausibly reflects mixing between (Si-28)-rich material, inherited from a previous generation of stars, and material enriched in Si-29 and Si-30, produced in intershell regions by neutron capture during He-burning. The absence of a correlation between the Si and C isotopic compositions of the SiC suggests either episodic condensation of SiC, extending over several thermal pulses, in the atmosphere of a single star, or the derivation of the SiC from several stars characterized by different rates of C-13 production.

Water masers and ammonia (1, 1) and (2, 2) towards six regions in the Carina Nebula

NASA Astrophysics Data System (ADS)

Breen, S. L.; Green, C.-E.; Cunningham, M. R.; Voronkov, M. A.; Horiuchi, S.; Green, J. A.

2018-01-01

We present water maser and ammonia (1, 1) and (2, 2) observations, towards six regions in the Carina Nebula, conducted with the Australia Telescope Compact Array. In total five water masers were detected within two of the target fields, and we provide their accurate positions and characteristics. These five water masers constitute all of the known masers detected towards star formation regions in the Carina Nebula and we argue, that given the evidence for active star formation, and the presence of many high-mass stars, the Carina Nebula is uncharacteristically devoid of masers. Our results are consistent with the Carina Nebula having a lack of young high-mass stars, despite the presence of older high-mass stars. Ammonia (1, 1) and (2, 2) emission was detected towards all but one of the target fields and we find that their linewidths and derived temperatures are consistent with the presence of young star formation regions.

Multi-messenger astronomy of gravitational-wave sources with flexible wide-area radio transient surveys

NASA Astrophysics Data System (ADS)

Kavic, Michael; Cregg C. Yancey, Brandon E. Bear, Bernadine Akukwe, Kevin Chen, Jayce Dowell, Jonathan D. Gough, Jonah Kanner, Kenneth Obenberger, Peter Shawhan, John H. Simonetti , Gregory B. Taylor , Jr-Wei Tsai

2016-01-01

We explore opportunities for multi-messenger astronomy using gravitational waves (GWs) and prompt, transient low-frequency radio emission to study highly energetic astrophysical events. We review the literature on possible sources of correlated emission of GWs and radio transients, highlighting proposed mechanisms that lead to a short-duration, high-flux radio pulse originating from the merger of two neutron stars or from a superconducting cosmic string cusp. We discuss the detection prospects for each of these mechanisms by low-frequency dipole array instruments such as LWA1, the Low Frequency Array and the Murchison Widefield Array. We find that a broad range of models may be tested by searching for radio pulses that, when de-dispersed, are temporally and spatially coincident with a LIGO/Virgo GW trigger within a ˜30 s time window and ˜200-500 deg(2) sky region. We consider various possible observing strategies and discuss their advantages and disadvantages. Uniquely, for low-frequency radio arrays, dispersion can delay the radio pulse until after low-latency GW data analysis has identified and reported an event candidate, enabling a prompt radio signal to be captured by a deliberately targeted beam. If neutron star mergers do have detectable prompt radio emissions, a coincident search with the GW detector network and low-frequency radio arrays could increase the LIGO/Virgo effective search volume by up to a factor of ˜2. For some models, we also map the parameter space that may be constrained by non-detections.

Multi-messenger Astronomy of Gravitational-wave Sources with Flexible Wide-area Radio Transient Surveys

NASA Astrophysics Data System (ADS)

Yancey, Cregg C.; Bear, Brandon E.; Akukwe, Bernadine; Chen, Kevin; Dowell, Jayce; Gough, Jonathan D.; Kanner, Jonah; Kavic, Michael; Obenberger, Kenneth; Shawhan, Peter; Simonetti, John H.; -Wei Tsai, Gregory B. Taylor, Jr.

2015-10-01

We explore opportunities for multi-messenger astronomy using gravitational waves (GWs) and prompt, transient low-frequency radio emission to study highly energetic astrophysical events. We review the literature on possible sources of correlated emission of GWs and radio transients, highlighting proposed mechanisms that lead to a short-duration, high-flux radio pulse originating from the merger of two neutron stars or from a superconducting cosmic string cusp. We discuss the detection prospects for each of these mechanisms by low-frequency dipole array instruments such as LWA1, the Low Frequency Array and the Murchison Widefield Array. We find that a broad range of models may be tested by searching for radio pulses that, when de-dispersed, are temporally and spatially coincident with a LIGO/Virgo GW trigger within a ˜30 s time window and ˜200-500 deg2 sky region. We consider various possible observing strategies and discuss their advantages and disadvantages. Uniquely, for low-frequency radio arrays, dispersion can delay the radio pulse until after low-latency GW data analysis has identified and reported an event candidate, enabling a prompt radio signal to be captured by a deliberately targeted beam. If neutron star mergers do have detectable prompt radio emissions, a coincident search with the GW detector network and low-frequency radio arrays could increase the LIGO/Virgo effective search volume by up to a factor of ˜2. For some models, we also map the parameter space that may be constrained by non-detections.

Integrating a Microwave Radiometer into Radar Hardware for Simultaneous Data Collection Between the Instruments

NASA Technical Reports Server (NTRS)

McLinden, Matthew; Piepmeier, Jeffrey

2013-01-01

The conventional method for integrating a radiometer into radar hardware is to share the RF front end between the instruments, and to have separate IF receivers that take data at separate times. Alternatively, the radar and radiometer could share the antenna through the use of a diplexer, but have completely independent receivers. This novel method shares the radar's RF electronics and digital receiver with the radiometer, while allowing for simultaneous operation of the radar and radiometer. Radars and radiometers, while often having near-identical RF receivers, generally have substantially different IF and baseband receivers. Operation of the two instruments simultaneously is difficult, since airborne radars will pulse at a rate of hundreds of microseconds. Radiometer integration time is typically 10s or 100s of milliseconds. The bandwidth of radar may be 1 to 25 MHz, while a radiometer will have an RF bandwidth of up to a GHz. As such, the conventional method of integrating radar and radiometer hardware is to share the highfrequency RF receiver, but to have separate IF subsystems and digitizers. To avoid corruption of the radiometer data, the radar is turned off during the radiometer dwell time. This method utilizes a modern radar digital receiver to allow simultaneous operation of a radiometer and radar with a shared RF front end and digital receiver. The radiometer signal is coupled out after the first down-conversion stage. From there, the radar transmit frequencies are heavily filtered, and the bands outside the transmit filter are amplified and passed to a detector diode. This diode produces a DC output proportional to the input power. For a conventional radiometer, this level would be digitized. By taking this DC output and mixing it with a system oscillator at 10 MHz, the signal can instead be digitized by a second channel on the radar digital receiver (which typically do not accept DC inputs), and can be down-converted to a DC level again digitally. This unintuitive step allows the digital receiver to sample both the radiometer and radar data at a rapid, synchronized data rate (greater than 1 MHz bandwidth). Once both signals are sampled by the same digital receiver, high-speed quality control can be performed on the radiometer data to allow it to take data simultaneously with the radar. The radiometer data can be blanked during radar transmit, or when the radar return is of a power level high enough to corrupt the radiometer data. Additionally, the receiver protection switches in the RF front end can double as radiometer calibration sources, the short (four-microsecond level) switching periods integrated over many seconds to estimate the radiometer offset. The major benefit of this innovation is that there is minimal impact on the radar performance due to the integration of the radiometer, and the radiometer performance is similarly minimally affected by the radar. As the radar and radiometer are able to operate simultaneously, there is no extended period of integration time loss for the radiometer (maximizing sensitivity), and the radar is able to maintain its full number of pulses (increasing sensitivity and decreasing measurement uncertainty).

Beyond the Borders of a Galaxy

NASA Technical Reports Server (NTRS)

2008-01-01

[figure removed for brevity, see original site] Side-by-Side Comparison Click on image for larger view

The outlying regions around the Southern Pinwheel galaxy, or M83, are highlighted in this composite image from NASA's Galaxy Evolution Explorer and the National Science Foundation's Very Large Array in New Mexico. The blue and pink pinwheel in the center is the galaxy's main stellar disk, while the flapping, ribbon-like structures are its extended arms.

The Galaxy Evolution Explorer is an ultraviolet survey telescope. Its observations, shown here in blue and green, highlight the galaxy's farthest-flung clusters of young stars up to 140,000 light-years from its center. The Very Large Array observations show the radio emission in red. They highlight gaseous hydrogen atoms, or raw ingredients for stars, which make up the lengthy, extended arms.

Astronomers are excited that the clusters of baby stars match up with the extended arms, because this helps them better understand how stars can be created out in the 'backwoods' of a galaxy.

In this image, far-ultraviolet light is blue, near-ultraviolet light is green and radio emission at a wavelength of 21 centimeters is red.

What Lies Beyond the Edge of a Galaxy The side-by-side comparison shows the Southern Pinwheel galaxy, or M83, as seen in ultraviolet light (right) and at both ultraviolet and radio wavelengths (left). While the radio data highlight the galaxy's long, octopus-like arms stretching far beyond its main spiral disk (red), the ultraviolet data reveal clusters of baby stars (blue) within the extended arms.

The ultraviolet image was taken by NASA's Galaxy Evolution Explorer between March 15 and May 20, 2007, at scheduled intervals. Back in 2005, the telescope first photographed M83 over a shorter period of time. That picture was the first to reveal far-flung baby stars forming up to 63,000 light-years from the edge of the main spiral disk. This came as a surprise to astronomers because a galaxy's outer territory typically lacks high densities of star-forming materials.

The newest picture of M83 from the Galaxy Evolution Explorer is shown at the right, and was taken over a longer period of time. In fact, it is one of the 'deepest,' or longest-exposure, images of a nearby galaxy in ultraviolet light. This deeper view shows more clusters of stars, as well as stars in the very remote reaches of the galaxy, up to 140,000 light-years away from its core.

The view at the left is a combination of the ultraviolet picture at the right and data taken by the telescopes of the National Science Foundation's Very Large Array in New Mexico. The radio data, colored here in red, reveal extended galactic arms of gaseous hydrogen atoms, which are raw ingredients for stars. Astronomers are excited that the remote clusters of baby stars match up with the extended arms, because this helps them better understand how stars can be created out in the boondocks of a galaxy.

M83 is located 15 million light-years away in the southern constellation Hydra.

In the Galaxy Evolution Explorer image on the right, near-ultraviolet light (or longer-wavelength ultraviolet light) is colored yellow and far-ultraviolet light is blue. In the combined image at the left, far-ultraviolet light is blue, near-ultraviolet light is green, and the radio emission at a wavelength of 21 centimeters is red.

Submillimeter Array reveals molecular complexity of dying stars

NASA Astrophysics Data System (ADS)

Tomasz

2018-01-01

The unique capabilities of the Submillimeter Array (SMA) have allowed unprecedented studies of cool evolved stars at submillimeter wavelengths. In particular, the SMA now offers the possibility to image multiple molecular transitions at once, owing to the 32-GHz wide instantaneous bandwidth of SWARM, the SMA’s new correlator. Molecular gas located far and very close to the photosphere of an asymptotic-giant branch (AGB) star, a red supergiant, or a pre-planetary nebula can now be examined in transitions observed simultaneously from a wide range of energy levels. This allows a very detailed quantitative investigation of physical and chemical conditions around these variable objects. Several imaging line surveys have been obtained with the SMA to reveal the beautiful complexity of these evolved systems. The surveys resulted in first submillimeter-wave identifications of molecules of prime astrophysical interest, e.g. of TiO, TiO2, and of rotational transitions at excited vibrational states of CO. An overview of recent SMA observations of cool evolved stars will be given with an emphasize on the interferometric line surveys. We will demonstrate their importance in unraveling the mass-loss phenomena, propagation of shocks in the circumstellar medium, and production of dust at elevated temperatures. The SMA studies of these molecular factories have a direct impact on our understanding of the chemical evolution of the Galaxy and stellar evolution at low and high masses.

Switched-beam radiometer front-end network analysis

NASA Technical Reports Server (NTRS)

Trew, R. J.; Bilbro, G. L.

1994-01-01

The noise figure performance of various delay-line networks fabricated from microstrip lines with varying number of elements was investigated using a computer simulation. The effects of resistive losses in both the transmission lines and power combiners were considered. In general, it is found that an optimum number of elements exists, depending upon the resistive losses present in the network. Small resistive losses are found to have a significant degrading effect upon the noise figure performance of the array. Extreme stability in switching characteristics is necessary to minimize the nondeterministic noise of the array. For example, it is found that a 6 percent tolerance on the delay-line lengths will produce a 0.2 db uncertainty in the noise figure which translates into a 13.67 K temperature uncertainty generated by the network. If the tolerance can be held to 2 percent, the uncertainty in noise figure and noise temperature will be 0.025 db and 1.67 K, respectively. Three phase shift networks fabricated using a commercially available PIN diode switch were investigated. Loaded-line phase shifters are found to have desirable RF and noise characteristics and are attractive components for use in phased-array networks.

A Spitzer Space Telescope Survey of Extreme Asymptotic Giant Branch Stars in M32

NASA Technical Reports Server (NTRS)

Jones, O.C.; McDonald, I.; Rich, R.M.; Kemper, F.; Boyer, M.L.; Zijlstra, A.A.; Bendo, G.J.

2014-01-01

We investigate the population of cool, evolved stars in the Local Group dwarf elliptical galaxy M32, using Infrared Array Camera observations from the Spitzer Space Telescope. We construct deep mid-infrared colour-magnitude diagrams for the resolved stellar populations within 3.5 arcminutes of M32's centre, and identify those stars that exhibit infrared excess. Our data is dominated by a population of luminous, dustproducing stars on the asymptotic giant branch (AGB) and extend to approximately 3 magnitudes below the AGB tip. We detect for the first time a sizeable population of 'extreme' AGB stars, highly enshrouded by circumstellar dust and likely completely obscured at optical wavelengths. The total dust-injection rate from the extreme AGB candidates is measured to be 7.5 x 10 (sup -7) solar masses per year, corresponding to a gas mass-loss rate of 1.5 x 10 (sup -4) solar masses per year. These extreme stars may be indicative of an extended star-formation epoch between 0.2 and 5 billion years ago.

Kepler Mission: A Technical Overview

NASA Technical Reports Server (NTRS)

Borucki, W. J.

2003-01-01

The Kepler Mission is a Discovery-class mission designed to continuously monitor the brightness of 100,000 solar-like stars to detect the transits of Earth-size and larger planets. It is a wide field of view photometer Schmidt-type telescope with an array of 42 CCDs. It has a 0.95 m aperture and 1.4 m primary and is designed to attain a photometric precision of 2 parts in 10(exp 5) for 12th magnitude solar-like stars for a 6 hr transit duration. It will continuously observe 100,000 main-sequence stars from 9th to 14th magnitude in the Cygnus constellation for a period of four years with a cadence of 4/hour. An additional 250 stars can be monitored at a cadence of l/minute to do astro-seismology of stars brighter than 11.5 mv. The photometer is scheduled to be launched into heliocentric orbit in 2007. A ground-based program to classify all 225,000 stars in the FOV and to do a detailed examination of a subset of the stars that show planetary companions is also planned.

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.

1989 IEEE Aerospace Applications Conference, Breckenridge, CO, Feb. 12-17, 1989, Conference Digest

NASA Astrophysics Data System (ADS)

Recent advances in electronic devices for aerospace applications are discussed in reviews and reports. Topics addressed include large-aperture mm-wave antennas, a cross-array radiometer for spacecraft applications, a technique for computing the propagation characteristics of optical fibers, an analog light-wave system for improving microwave-telemetry data communication, and a ground demonstration of an orbital-debris radar. Consideration is given to a verifiable autonomous satellite control system, Inmarsat second-generation satellites for mobile communication, automated tools for data-base design and criteria for their selection, and a desk-top simulation work station based on the DSP96002 microprocessor chip.

Remote sensing of oceanic phytoplankton - Present capabilities and future goals

NASA Technical Reports Server (NTRS)

Esaias, W. E.

1980-01-01

A description is given of current work in the development of sensors, and their integration into increasingly powerful systems, for oceanic phytoplankton abundance estimation. Among the problems relevant to such work are phytoplankton ecology, the spatial and temporal domains, available sensor platforms, and sensor combinations. Among the platforms considered are satellites, aircraft, tethered balloons, helicopters, ships, and the Space Shuttle. Sensors discussed include microwave radiometers, laser fluorosensors, microwave scatterometers, multispectral scanners, Coastal Ocean Dynamics Radar (CODAR), and linear array detectors. Consideration is also given to the prospects for such future sensor systems as the National Oceanic Satellite System (NOSS) and the Airborne Integrated Mapping System (AIMS).

LAPR: An experimental aircraft pushbroom scanner

NASA Technical Reports Server (NTRS)

Wharton, S. W.; Irons, J. I.; Heugel, F.

1980-01-01

A three band Linear Array Pushbroom Radiometer (LAPR) was built and flown on an experimental basis by NASA at the Goddard Space Flight Center. The functional characteristics of the instrument and the methods used to preprocess the data, including radiometric correction, are described. The radiometric sensitivity of the instrument was tested and compared to that of the Thematic Mapper and the Multispectral Scanner. The radiometric correction procedure was evaluated quantitatively, using laboratory testing, and qualitatively, via visual examination of the LAPR test flight imagery. Although effective radiometric correction could not yet be demonstrated via laboratory testing, radiometric distortion did not preclude the visual interpretation or parallel piped classification of the test imagery.

Blazing Black Holes Spotted in Spiral Beauty

NASA Image and Video Library

2013-01-07

This new view of spiral galaxy IC 342, also known as Caldwell 5, includes data from NASA Nuclear Spectroscopic Telescope Array, or NuSTAR. IC 342 lies 7 million light-years away in the Camelopardalis constellation.

TEMPEST-D MM-Wave Radiometer

NASA Astrophysics Data System (ADS)

Padmanabhan, S.; Gaier, T.; Reising, S. C.; Lim, B.; Stachnik, R. A.; Jarnot, R.; Berg, W. K.; Kummerow, C. D.; Chandrasekar, V.

2016-12-01

The TEMPEST-D radiometer is a five-frequency millimeter-wave radiometer at 89, 165, 176, 180, and 182 GHz. The direct-detection architecture of the radiometer reduces its power consumption and eliminates the need for a local oscillator, reducing complexity. The Instrument includes a blackbody calibrator and a scanning reflector, which enable precision calibration and cross-track scanning. The MMIC-based millimeter-wave radiometers take advantage of the technology developed under extensive investment by the NASA Earth Science Technology Office (ESTO). The five-frequency millimeter-wave radiometer is built by Jet Propulsion Laboratory (JPL), which has produced a number of state-of-the-art spaceborne microwave radiometers, such as the Microwave Limb Sounder (MLS), Advanced Microwave Radiometer (AMR) for Jason-2/OSTM, Jason-3, and the Juno Microwave Radiometer (MWR). The TEMPEST-D Instrument design is based on a 165 to 182 GHz radiometer design inherited from RACE and an 89 GHz receiver developed under the ESTO ACT-08 and IIP-10 programs at Colorado State University (CSU) and JPL. The TEMPEST reflector scan and calibration methodology is adapted from the Advanced Technology Microwave Sounder (ATMS) and has been validated on the Global Hawk unmanned aerial vehicle (UAV) using the High Altitude MMIC Sounding radiometer (HAMSR) instrument. This presentation will focus on the design, development and performance of the TEMPEST-D radiometer instrument. The flow-down of the TEMPEST-D mission objectives to instrument level requirements will also be discussed.

Nist Microwave Blackbody: The Design, Testing, and Verification of a Conical Brightness Temperature Source

NASA Astrophysics Data System (ADS)

Houtz, Derek Anderson

Microwave radiometers allow remote sensing of earth and atmospheric temperatures from space, anytime, anywhere, through clouds, and in the dark. Data from microwave radiometers are high-impact operational inputs to weather forecasts, and are used to provide a vast array of climate data products including land and sea surface temperatures, soil moisture, ocean salinity, cloud precipitation and moisture height profiles, and even wind speed and direction, to name a few. Space-borne microwave radiometers have a major weakness when it comes to long-term climate trends due to their lack of traceability. Because there is no standard, or absolute reference, for microwave brightness temperature, nationally or internationally, individual instruments must each rely on their own internal calibration source to set an absolute reference to the fundamental unit of Kelvin. This causes each subsequent instrument to have a calibration offset and there is no 'true' reference. The work introduced in this thesis addresses this vacancy by proposing and introducing a NIST microwave brightness temperature source that may act as the primary reference. The NIST standard will allow pre-launch calibration of radiometers across a broad range of remote sensing pertinent frequencies between 18 GHz and 220 GHz. The blackbody will be capable of reaching temperatures ranging between liquid nitrogen boiling at approximately 77 K and warm-target temperature of 350 K. The brightness temperature of the source has associated standard uncertainty ranging as a function of frequency between 0.084 K and 0.111 K. The standard can be transferred to the calibration source in the instrument, providing traceability of all subsequent measurements back to the primary standard. The development of the NIST standard source involved predicting and measuring its brightness temperature, and minimizing the associated uncertainty of this quantity. Uniform and constant physical temperature along with well characterized and maximized emissivity are fundamental to a well characterized blackbody. The chosen geometry is a microwave absorber coated copper cone. Electromagnetic and thermal simulations are introduced to optimize the design. Experimental verifications of the simulated quantities confirm the predicted performance of the blackbody.

Spectral measurements of the cosmic microwave background

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

Kogut, A.J.

1989-04-01

Three experiments have measured the intensity of the Cosmic Microwave Background (CMB) at wavelengths 4.0, 3.0, and 0.21 cm. The measurement at 4.0 cm used a direct-gain total-power radiometer to measure the difference in power between the zenith sky and a large cryogenic reference target. Foreground signals are measured with the same instrument and subtracted from the zenith signal, leaving the CMB as the residual. The reference target consists of a large open-mouth cryostat with a microwave absorber submerged in liquid helium; thin windows block the radiative heat load and prevent condensation atmospheric gases within the cryostat. The thermodynamic temperaturemore » of the CMB at 4.0 cm is 2.59 +- 0.07 K. The measurement at 3.0 cm used a superheterodyne Dicke-switched radiometer with a similar reference target to measure the zenith sky temperature. A rotating mirror allowed one of the antenna beams to be redirected to a series of zenith angles, permitting automated atmospheric measurements without moving the radiometer. A weighted average of 5 years of data provided the thermodynamic temperature of the CMB at 3.0 cm of 2.62 +- 0.06 K. The measurement at 0.21 cm used Very Large Array observations of interstellar ortho-formaldehyde to determine the CMB intensity in molecular clouds toward the giant HII region W51A (G49.5-0.4). Solutions of the radiative transfer problem in the context of a large velocity gradient model provided estimates of the CMB temperature within the foreground clouds. Collisional excitation from neutral hydrogen molecules within the clouds limited the precision of the result. The thermodynamic temperature of the CMB at 0.21 cm is 3.2 +- 0.9 K. 72 refs., 27 figs., 38 tabs.« less

A Complete Census of the ~7000 Milky Way HII Regions

NASA Astrophysics Data System (ADS)

Armentrout, William Paul; Anderson, Loren Dean; Wenger, Trey; Bania, Thomas; Balser, Dana; Dame, Thomas; Dickey, John M.; Dawson, Joanne; Jordan, Christopher H.; McClure-Griffiths, Naomi M.; Andersen, Morten

2018-01-01

HII regions are the archetypical tracers of high-mass star formation. Because of their high luminosities, they can be seen across the entire Galactic disk from mid-infrared to radio wavelengths. A uniformly sensitive survey of Galactic HII regions would allow us to constrain the properties of Galactic structure and star formation. We have cataloged over 8000 HII regions and candidates in the WISE Catalog of Galactic HII Regions (astro.phys.wvu.edu/wise), but only 2000 of these are confirmed HII regions to date.To bring us closer to a complete census of high-mass star formation regions in the Milky Way, we have several ongoing observational campaigns. These efforts include (1) Green Bank Telescope radio recombination line (RRL) observations as part of the HII Region Discovery Survey (HRDS); (2) Australia Telescope Compact Array observations of southern HII region candidates in the Southern HII Region Discovery Survey (SHRDS); (3) Green Bank and Gemini North Telescope observations of star formation regions thought to reside at the edge of the star forming disk in the Outer Scutum-Centaurus Arm (OSC); and (4) Very Large Array continuum observations of the faintest HII region candidates in the second and third Galactic quadrants.Together, these observations will detect the RRL emission from all Galactic HII regions with peak cm-wavelength flux densities > 60mJy, establish the outer edge of Galactic high-mass star formation, and determine the number of HII regions in the Galaxy. The HRDS and SHRDS surveys have more than doubled the known population of Galactic HII regions. We use the OSC observations to determine the properties of high-mass star formation in the extreme outer Galaxy and our VLA observations to determine how many of our faint candidates are indeed HII regions. We combine the completeness limits we obtain through these HII region surveys with an HII region population synthesis model to estimate the total number of Galactic HII regions. From this, we predict nearly 7000 HII regions in the Milky Way created by a central star of type B2 or earlier.

Digital signal processing in microwave radiometers

NASA Technical Reports Server (NTRS)

Lawrence, R. W.; Stanley, W. D.; Harrington, R. F.

1980-01-01

A microprocessor based digital signal processing unit has been proposed to replace analog sections of a microwave radiometer. A brief introduction to the radiometer system involved and a description of problems encountered in the use of digital techniques in radiometer design are discussed. An analysis of the digital signal processor as part of the radiometer is then presented.

Soil Moisture Active/Passive (SMAP) L-band microwave radiometer post-launch calibration

USDA-ARS?s Scientific Manuscript database

The SMAP microwave radiometer is a fully-polarimetric L-band radiometer flown on the SMAP satellite in a 6 AM / 6 PM sun-synchronous orbit at 685-km altitude. Since April 2015, the radiometer has been under calibration and validation to assess the quality of the radiometer L1B data product. Calibrat...

Getting NuSTAR on target: predicting mast motion

NASA Astrophysics Data System (ADS)

Forster, Karl; Madsen, Kristin K.; Miyasaka, Hiromasa; Craig, William W.; Harrison, Fiona A.; Rana, Vikram R.; Markwardt, Craig B.; Grefenstette, Brian W.

2016-07-01

The Nuclear Spectroscopic Telescope Array (NuSTAR) is the first focusing high energy (3-79 keV) X-ray observatory operating for four years from low Earth orbit. The X-ray detector arrays are located on the spacecraft bus with the optics modules mounted on a flexible mast of 10.14m length. The motion of the telescope optical axis on the detectors during each observation is measured by a laser metrology system and matches the pre-launch predictions of the thermal flexing of the mast as the spacecraft enters and exits the Earths shadow each orbit. However, an additional motion of the telescope field of view was discovered during observatory commissioning that is associated with the spacecraft attitude control system and an additional flexing of the mast correlated with the Solar aspect angle for the observation. We present the methodology developed to predict where any particular target coordinate will fall on the NuSTAR detectors based on the Solar aspect angle at the scheduled time of an observation. This may be applicable to future observatories that employ optics deployed on extendable masts. The automation of the prediction system has greatly improved observatory operations efficiency and the reliability of observation planning.

A Multi-Frequency Study of the Milky Way-Like Spiral Galaxy NGC 6744

NASA Astrophysics Data System (ADS)

Yew, Miranda; Filipović, Miroslav D.; Roper, Quentin; Collier, Jordan D.; Crawford, Evan J.; Jarrett, Thomas H.; Tothill, Nicholas F. H.; O'Brien, Andrew N.; Pavlović, Marko Z.; Pannuti, Thomas G.; Galvin, Timothy J.; Kapińska, Anna D.; Cluver, Michelle E.; Banfield, Julie K.; Schlegel, Eric M.; Maxted, Nigel; Grieve, Kevin R.

2018-03-01

We present a multi-frequency study of the intermediate spiral SAB(r)bc type galaxy NGC 6744, using available data from the Chandra X-Ray telescope, radio continuum data from the Australia Telescope Compact Array and Murchison Widefield Array, and Wide-field Infrared Survey Explorer infrared observations. We identify 117 X-ray sources and 280 radio sources. Of these, we find nine sources in common between the X-ray and radio catalogues, one of which is a faint central black hole with a bolometric radio luminosity similar to the Milky Way's central black hole. We classify 5 objects as supernova remnant (SNR) candidates, 2 objects as likely SNRs, 17 as H ii regions, 1 source as an AGN; the remaining 255 radio sources are categorised as background objects and one X-ray source is classified as a foreground star. We find the star-formation rate (SFR) of NGC 6744 to be in the range 2.8-4.7 M⊙ yr - 1 signifying the galaxy is still actively forming stars. The specific SFR of NGC 6744 is greater than that of late-type spirals such as the Milky Way, but considerably less that that of a typical starburst galaxy.

Getting NuSTAR on Target: Predicting Mast Motion

NASA Technical Reports Server (NTRS)

Forster, Karl; Madsen, Kristin K.; Miyasaka, Hiroshima; Craig, William W.; Harrison, Fiona A.; Rana, Vikram R.; Markwardt, Craig B.; Grenfenstette, Brian W.

2017-01-01

The Nuclear Spectroscopic Telescope Array (NuSTAR) is the first focusing high energy (3-79 keV) X-ray observatory operating for four years from low Earth orbit. The X-ray detector arrays are located on the spacecraft bus with the optics modules mounted on a flexible mast of 10.14m length. The motion of the telescope optical axis on the detectors during each observation is measured by a laser metrology system and matches the pre-launch predictions of the thermal flexing of the mast as the spacecraft enters and exits the Earths shadow each orbit. However, an additional motion of the telescope field of view was discovered during observatory commissioning that is associated with the spacecraft attitude control system and an additional flexing of the mast correlated with the Solar aspect angle for the observation. We present the methodology developed to predict where any particular target coordinate will fall on the NuSTAR detectors based on the Solar aspect angle at the scheduled time of an observation. This may be applicable to future observatories that employ optics deployed on extendable masts. The automation of the prediction system has greatly improved observatory operations efficiency and the reliability of observation planning.

ISM Properties of a Massive Dusty Star-forming Galaxy Discovered at z ˜ 7

NASA Astrophysics Data System (ADS)

Strandet, M. L.; Weiss, A.; De Breuck, C.; Marrone, D. P.; Vieira, J. D.; Aravena, M.; Ashby, M. L. N.; Béthermin, M.; Bothwell, M. S.; Bradford, C. M.; Carlstrom, J. E.; Chapman, S. C.; Cunningham, D. J. M.; Chen, Chian-Chou; Fassnacht, C. D.; Gonzalez, A. H.; Greve, T. R.; Gullberg, B.; Hayward, C. C.; Hezaveh, Y.; Litke, K.; Ma, J.; Malkan, M.; Menten, K. M.; Miller, T.; Murphy, E. J.; Narayanan, D.; Phadke, K. A.; Rotermund, K. M.; Spilker, J. S.; Sreevani, J.

2017-06-01

We report the discovery and constrain the physical conditions of the interstellar medium of the highest-redshift millimeter-selected dusty star-forming galaxy to date, SPT-S J031132-5823.4 (hereafter SPT0311-58), at z=6.900+/- 0.002. SPT0311-58 was discovered via its 1.4 mm thermal dust continuum emission in the South Pole Telescope (SPT)-SZ survey. The spectroscopic redshift was determined through an Atacama Large Millimeter/submillimeter Array 3 mm frequency scan that detected CO(6-5), CO(7-6), and [{{C}} {{I}}](2-1), and subsequently was confirmed by detections of CO(3-2) with the Australia Telescope Compact Array and [{{C}} {{II}}] with APEX. We constrain the properties of the ISM in SPT0311-58 with a radiative transfer analysis of the dust continuum photometry and the CO and [{{C}} {{I}}] line emission. This allows us to determine the gas content without ad hoc assumptions about gas mass scaling factors. SPT0311-58 is extremely massive, with an intrinsic gas mass of {M}{gas}=3.3+/- 1.9× {10}11 {M}⊙ . Its large mass and intense star formation is very rare for a source well into the epoch of reionization.

An array of antenna-coupled superconducting microbolometers for passive indoors real-time THz imaging

NASA Astrophysics Data System (ADS)

Luukanen, A.; Grönberg, L.; Helistö, P.; Penttilä, J. S.; Seppä, H.; Sipola, H.; Dietlein, C. R.; Grossman, E. N.

2006-05-01

The temperature resolving power (NETD) of millimeter wave imagers based on InP HEMT MMIC radiometers is typically about 1 K (30 ms), but the MMIC technology is limited to operating frequencies below ~ 150 GHz. In this paper we report the first results from a pixel developed for an eight pixel sub-array of superconducting antenna-coupled microbolometers, a first step towards a real-time imaging system, with frequency coverage of 0.2 - 3.6 THz. These detectors have demonstrated video-rate NETDs in the millikelvin range, close to the fundamental photon noise limit, when operated at a bath temperature of ~ 4K. The detectors will be operated within a turn-key cryogen-free pulse tube refrigerator, which allows for continuous operation without the need for liquid cryogens. The outstanding frequency agility of bolometric detectors allows for multi-frequency imaging, which greatly enhances the discrimination of e.g. explosives against innoncuous items concealed underneath clothing.

Performance and Results from a Space Borne, Uncooled Microbolometer Array Spectral Radiometric Imager

NASA Technical Reports Server (NTRS)

Spinhirne, James M; Scott, V. Stan; Lancaster, Redgie S.; Manizade, Kathrine; Palm, Steven P.

2000-01-01

The Infrared Spectral Imaging Radiometer experiment was flown on a space shuttle mission as a shuttle hitchhiker experiment in August of 1997. The goals of the experiment were to test uncooled array detectors for infrared spectral imaging from space and to apply for the first time retrieval from space of brightness temperatures of cloud, land and sea along with direct laser measurements of cloud top height. The instrument operates in 3 narrow and one broad spectral band, all between 7 and 13 microns in either stare or time-delay and integration mode. The nominal spatial resolution was 1/4 kilometer. Using onboard calibrations along with periodic views of deep space, radiometric calibration of imagery was carried out and performance analyzed. The noise equivalent temperature difference and absolute accuracy reported here varied with operating mode, spectral band and scene temperature but were within requirements. This paper provides a description of the instrument, its operating modes, the method of brightness temperature retrieval, the method of spectral registration and results from the flight.

High-mass Star Formation and Its Initial Conditions

NASA Astrophysics Data System (ADS)

Zhang, C. P.

2017-11-01

In this thesis, we present four works on the infrared dark clouds, fragmentation and deuteration of compact and cold cores, hyper-compact (HC) HII regions, and infrared dust bubbles, respectively. They are not only the products of early high-mass star formation, but reflect different evolutionary sequences of high-mass star formation. (1) Using the IRAM (Institut de Radioastronomie Millimétrique) 30 m telescope, we obtained HCO^+, HNC, N_2^+, and C^{18}O emission in six IRDCs (infrared dark clouds), and study their dynamics, stability, temperature, and density. (2) Fragmentation at the earliest phases is an important process of massive star formation. Eight massive precluster clumps (G18.17, G18.21, G23.97N, G23.98, G23.44, G23.97S, G25.38, and G25.71) were selected from the SCUBA (submillimetre Common-User Bolometer Array) 850 μm and 450 μm data. The VLA (Very Large Array) at 1.3 cm, PbBI at 3.5 mm and 1.3 mm, APEX (Atacama Pathfinder Experiment telescope) at 870 μm observations were followed up, and archival infrared data at 4.5 μm, 8.0 μm, 24 μm, and 70 μm were combined to study the fragmentation and evolution of these clumps. We explored the habitats of the massive clumps at large scale, cores/condensations at small scale, and the fragmentation process at different wavelengths. Star formation in these eight clumps may have been triggered by the UC (ultra-compact) HII regions nearby. (3) The formation of hyper-compact (HC) HII regions is an important stage in massive star formation. We present high angular resolution observations carried out with the SMA (Submillimeter Array) and the VLA (Very Large Array) toward the HC HII region G35.58-0.03. With the 1.3 mm SMA and 1.3 cm VLA, we detected a total of about 25 transitions of 8 different species and their isotopologues (CO, CH_3CN, SO_2, CH_3CCH, OCS, CS, H30α/38β, and NH_{3}). G35.58-0.03 consists of an HC HII core with electron temperature Te* ≥ 5500 K, emission measure EM ≈ 1.9×10^{9} pc\\cdotcm^{-6}, local volume electron density ne= 3.3×10^{5} cm^{-3}, FWHM ≈ 43.2 km\\cdots^{-1} for radio recombination lines from both H30α and H38β at its intrinsic core size 3714 au. The H30α line shows evidence of an ionized outflow driving a molecular outflow. The molecular envelope shows evidence of infall and outflow with an infall rate of 0.033 M_{⊙}\\cdotyr^{-1} and a mass loss rate 0.052 M_{⊙}\\cdotyr^{-1}. The derived momenta (˜0.05 M_{⊙}\\cdot{km}\\cdot{s}^{-1}) are comparable for both the infalling and outflowing gas per year. It is suggested that the infall is predominant and the envelope mass of the dense core is increasing rapidly, but accretion in the inner part might have already been halted. (4) OB type stars have strong free-free radiation. The ultraviolet radiation from ionizing stars may heat the dust and ionize the gas to sweep up an expanding bubble, probably accompanied by formation of next generation of stars. The position-velocity diagram clearly shows that N68 may be expanding outward. The structure of bubble S51, carried with shell and front side, is exhibited with ^{13}CO and C^{18}O emission. Both outflow and inflow may exist in the shell of the bubble S51. They may represent the next generation of stars whose formation was triggered by the bubble expanding into the molecular gas. For the bubble N131, we aim to further explore the molecular clumps and star formation at a higher spatial resolution compared with previous CO observations, and try to speculate its origin. The bubble N131 is likely originated in a filamentary nebula, within which the strong stellar wind from a group of massive stars broke up a pre-existing filamentary nebula into the clumps AD and BC, and sweeped up the surrounded material onto the ringlike shell of the bubble N131.

Is there a cluster in the massive star forming region IRAS 20126+4104?

NASA Astrophysics Data System (ADS)

Montes, V. A.; Hofner, Peter; Anderson, C.; Rosero, V.

2017-03-01

A Chandra X-ray Observatory ACIS-I observation and a 6 cm continuum radio observation with the Karl G. Jansky Very Large Array (VLA) together with a multiwavelength study in infrared (2MASS and Spitzer) and optical (USNO-B1.0) shows an increasing surface density of X-ray sources toward the massive protostar. There are at least 43 YSOs within 1.2 pc distance from the massive protostar. This number is consistent with typical B-type stars clusters (Lada & Lada 2003).

The Fast Rotating Star 51 Oph Probed by VEGA/CHARA

NASA Astrophysics Data System (ADS)

Jamialahmadi, N.; Berio, P.; Meilland, A.; Perraut, K.; Mourard, D.; Lopez, B.; Stee, P.; Nardetto, N.; Pichon, B.; Clausse, J. M.; Spang, A.; McAlister, H.; ten Brummelaar, T.

2015-12-01

Stellar rotation is a key in our understanding of both mass-loss and evolution of intermediate and massive stars. It can lead to anisotropic mass-loss in the form of radiative wind or an excretion disk. We used the VEGA visible beam combiner installed on the CHARA array that reaches a sub milliarcsecond resolution. We derived, for the first time, the extension and flattening of 51 Oph photosphere. We found an elongated ratio of 1.45 ± 0.12.

Nustar: Bringing the High-Energy Universe into Focus

NASA Technical Reports Server (NTRS)

Fineberg, Larry

2016-01-01

This is a presentation to students at the University of Florida in the Small Satellite Design Club. The subject matter is the NuSTAR mission and covers topics about the spacecraft itself and the launch campaign. NASA's Nuclear Spectroscopic Telescope Array (NuSTAR) is the first focusing high-energy X-ray mission. Studies the hottest, densest, most energetic phenomena in the Universe. Purpose is to search for black holes, map the remnants of stellar explosions, and study the most extreme active galaxies.

High angular resolution observations of the cool giant V Hya

NASA Astrophysics Data System (ADS)

Pedretti, E.; Monnier, J. D.; Millan Gabet, R.; Traub, W. A.; Tuthill, P.; Danchi, W.; Berger, J.; Schloerb, F. P.; Thureau, N. D.; Carleton, N. P.; Lacasse, M. G.; Schuller, P. A.; Ragland, S.; Brewer, M.

2005-12-01

We present the preliminary interferometric observations of the cool giant star V Hya. V Hya, which is known to have mass-loss and to be surrounded by a dust shell,was observed in three narrow-band filters in the H bandpass at the infrared optical telescope array (IOTA), using the IONIC three-telescope beam combiner. The star was also observed at the Keck telescope using an aperture mask. We discuss the results and try to fit simple models to the observed data.

Photon counting photodiode array detector for far ultraviolet (FUV) astronomy

NASA Technical Reports Server (NTRS)

Hartig, G. F.; Moos, H. W.; Pembroke, R.; Bowers, C.

1982-01-01

A compact, stable, single-stage intensified photodiode array detector designed for photon-counting, far ultraviolet astronomy applications employs a saturable, 'C'-type MCP (Galileo S. MCP 25-25) to produce high gain pulses with a narrowly peaked pulse height distribution. The P-20 output phosphor exhibits a very short decay time, due to the high current density of the electron pulses. This intensifier is being coupled to a self-scanning linear photodiode array which has a fiber optic input window which allows direct, rigid mechanical coupling with minimal light loss. The array was scanned at a 250 KHz pixel rate. The detector exhibits more than adequate signal-to-noise ratio for pulse counting and event location. Previously announced in STAR as N82-19118

High-Altitude MMIC Sounding Radiometer for the Global Hawk Unmanned Aerial Vehicle

NASA Technical Reports Server (NTRS)

Brown, Shannon T.; Lim, Boon H.; Tanner, Alan B.; Tanabe, Jordan M.; Kangaslahti, Pekka P.; Gaier, Todd C.; Soria, Mary M.; Lambrigtsen, Bjorn H.; Denning, Richard F.; Stachnik, Robert A.

2012-01-01

Microwave imaging radiometers operating in the 50-183 GHz range for retrieving atmospheric temperature and water vapor profiles from airborne platforms have been limited in the spatial scales of atmospheric structures that are resolved not because of antenna aperture size, but because of high receiver noise masking the small variations that occur on small spatial scales. Atmospheric variability on short spatial and temporal scales (second/ km scale) is completely unresolved by existing microwave profilers. The solution was to integrate JPL-designed, high-frequency, low-noise-amplifier (LNA) technology into the High-Altitude MMIC Sounding Radiometer (HAMSR), which is an airborne microwave sounding radiometer, to lower the system noise by an order of magnitude to enable the instrument to resolve atmospheric variability on small spatial and temporal scales. HAMSR has eight sounding channels near the 60-GHz oxygen line complex, ten channels near the 118.75-GHz oxygen line, and seven channels near the 183.31-GHz water vapor line. The HAMSR receiver system consists of three heterodyne spectrometers covering the three bands. The antenna system consists of two back-to-back reflectors that rotate together at a programmable scan rate via a stepper motor. A single full rotation includes the swath below the aircraft followed by observations of ambient (roughly 0 C in flight) and heated (70 C) blackbody calibration targets located at the top of the rotation. A field-programmable gate array (FPGA) is used to read the digitized radiometer counts and receive the reflector position from the scan motor encoder, which are then sent to a microprocessor and packed into data files. The microprocessor additionally reads telemetry data from 40 onboard housekeeping channels (containing instrument temperatures), and receives packets from an onboard navigation unit, which provides GPS time and position as well as independent attitude information (e.g., heading, roll, pitch, and yaw). The raw data files are accessed through an Ethernet port. The HAMSR data rate is relatively low at 75 kbps, allowing for real-time access over the Global Hawk high-data-rate downlink. Once on the ground, the raw data are unpacked and processed through two levels of processing. The Level 1 product contains geo-located, time-stamped, calibrated brightness temperatures for the Earth scan. These data are then input to a lD variational retrieval algorithm to produce temperature, water vapor, and cloud liquid water profiles, as well as several derived products such as potential temperature and relative humidity.

Beginning the Journey to the Launch Pad

NASA Image and Video Library

2012-01-25

NASA Nuclear Spectroscopic Telescope Array, or NuSTAR, mission is lowered into its shipping container at Orbital Sciences Corporation in Dulles, Va. It is scheduled to launch from Kwajalein Atoll in the Marshall Islands on March 14, 2012.

A Tale of Two Comets: ISON

NASA Image and Video Library

2013-11-25

An optical color image of galaxies is seen here overlaid with X-ray data magenta from NASA Nuclear Spectroscopic Telescope Array NuSTAR. Both magenta blobs show X-rays from massive black holes buried at the hearts of galaxies.

Environments of z~0.2 Star Forming Galaxies: Building on the Citizen Science Discovery of the Green Peas

NASA Astrophysics Data System (ADS)

Cardamone, Carolin; Cappelluti, Nico; Powell, Meredith; Urry, Meg; Galaxy Zoo Science Team

2018-01-01

‘Green Pea’ galaxies, discovered in the Galaxy Zoo citizen science project, are rare low-mass (M < 1 x 1010 M⊙) galaxies, experiencing an episode of compact, relatively low-metalicity (z ≈ 1/5 z⊙), intense starformation (3-60 M⊙/yr). While their spectra have been investigated in a wide-array of follow-up studies, a detailed study of their environments is missing. Two-point correlation functions have been used to show the environmental dependence of an array of galaxy properties (eg., mass, luminosity, color, star formation, and morphology). In this study, we present a cross-correlation analysis between the Green Peas and the Luminous Red Galaxies throughout the SDSS footprint, and we find that the population of Green Peas at 0.11

KSC-2012-3123

NASA Image and Video Library

2012-05-30

VANDENBERG AIR FORCE BASE, Calif. -- On the runway at Vandenberg Air Force Base in California, the Orbital Sciences L-1011 carrier aircraft is readied for flight. Once the Pegasus XL rocket with NASA's Nuclear Spectroscopic Telescope Array NuSTAR spacecraft is attached, the L-1011 will fly to the Ronald Reagan Ballistic Missile Defense Test Site at the Pacific Ocean’s Kwajalein Atoll. The Pegasus will launch NuSTAR into space where the high-energy x-ray telescope will conduct a census for black holes, map radioactive material in young supernovae remnants, and study the origins of cosmic rays and the extreme physics around collapsed stars. For more information, visit science.nasa.gov/missions/nustar/. Photo credit: NASA/Randy Beaudoin, VAFB

MINERVA: A Dedicated Observatory for Detection of Nearby Low-Mass Exoplanets

NASA Astrophysics Data System (ADS)

McCrady, Nate; Johnson, John; Wright, Jason; Wittenmyer, Robert A.; Blake, Cullen; Swift, Jonathan; Eastman, Jason D.; Plavchan, Peter; Riddle, Reed L.; Muirhead, Philip Steven; Bottom, Michael; Zhao, Ming; Beatty, Thomas G.

2015-01-01

Detection of low-mass planets around GKM stars requires sub-meter-per-second radial velocity precision. Stellar noise sources (starspots, oscillations, and granulation) necessitate high cadence observations. MINERVA is a dedicated observatory for velocimetric detection of low mass exoplanets orbiting nearby stars. Our array of four robotic 0.7-meter PlaneWave telescopes feeds a purpose-built, temperature-stabilized, iodine cell spectrometer from Callaghan Innovation. We will monitor bright, sun-like stars within 100 pc every clear night from Whipple Observatory on Mt Hopkins, Arizona. Each telescope is also equipped with an Andor CCD for followup photometry and education use. Commissioning is underway on the site and science observations will begin in early 2015.

KSC-2012-3124

NASA Image and Video Library

2012-05-30

VANDENBERG AIR FORCE BASE, Calif. -- On the runway at Vandenberg Air Force Base in California, the Orbital Sciences L-1011 carrier aircraft is readied for flight. Once the Pegasus XL rocket with NASA's Nuclear Spectroscopic Telescope Array NuSTAR spacecraft is attached, the L-1011 will fly to the Ronald Reagan Ballistic Missile Defense Test Site at the Pacific Ocean’s Kwajalein Atoll. The Pegasus will launch NuSTAR into space where the high-energy x-ray telescope will conduct a census for black holes, map radioactive material in young supernovae remnants, and study the origins of cosmic rays and the extreme physics around collapsed stars. For more information, visit science.nasa.gov/missions/nustar/. Photo credit: NASA/Randy Beaudoin, VAFB

The nature, origin and evolution of embedded star clusters

NASA Technical Reports Server (NTRS)

Lada, Charles J.; Lada, Elizabeth A.

1991-01-01

The recent development of imaging infrared array cameras has enabled the first systematic studies of embedded protoclusters in the galaxy. Initial investigations suggest that rich embedded clusters are quite numerous and that a significant fraction of all stars formed in the galaxy may begin their lives in such stellar systems. These clusters contain extremely young stellar objects and are important laboratories for star formation research. However, observational and theoretical considerations suggest that most embedded clusters do not survive emergence from molecular clouds as bound clusters. Understanding the origin, nature, and evolution of embedded clusters requires understanding the intimate physical relation between embedded clusters and the dense molecular cloud cores from which they form.

New far infrared images of bright, nearby, star-forming regions

NASA Technical Reports Server (NTRS)

Harper, D. AL, Jr.; Cole, David M.; Dowell, C. Darren; Lees, Joanna F.; Lowenstein, Robert F.

1995-01-01

Broadband imaging in the far infrared is a vital tool for understanding how young stars form, evolve, and interact with their environment. As the sensitivity and size of detector arrays has increased, a richer and more detailed picture has emerged of the nearest and brightest regions of active star formation. We present data on M 17, M 42, and S 106 taken recently on the Kuiper Airborne Observatory with the Yerkes Observatory 60-channel far infrared camera, which has pixel sizes of 17 in. at 60 microns, 27 in. at 100 microns, and 45 in. at 160 and 200 microns. In addition to providing a clearer view of the complex central cores of the regions, the images reveal new details of the structure and heating of ionization fronts and photodissociation zones where radiation form luminous stars interacts with adjacent molecular clouds.

Modelling of celestial backgrounds

NASA Astrophysics Data System (ADS)

Hickman, Duncan L.; Smith, Moira I.; Lim, Jae-Wan; Jeon, Yun-Ho

2018-05-01

For applications where a sensor's image includes the celestial background, stars and Solar System Bodies compromise the ability of the sensor system to correctly classify a target. Such false targets are particularly significant for the detection of weak target signatures which only have a small relative angular motion. The detection of celestial features is well established in the visible spectral band. However, given the increasing sensitivity and low noise afforded by emergent infrared focal plane array technology together with larger and more efficient optics, the signatures of celestial features can also impact performance at infrared wavelengths. A methodology has been developed which allows the rapid generation of celestial signatures in any required spectral band using star data from star catalogues and other open-source information. Within this paper, the radiometric calculations are presented to determine the irradiance values of stars and planets in any spectral band.

KSC-2012-1259

NASA Image and Video Library

2012-02-03

VANDENBERG AIR FORCE BASE, Calif. – In processing facility 1555 at Vandenberg Air Force Base in California, spacecraft technicians move a Pegasus fairing separation ring toward the workstand for NASA's Nuclear Spectroscopic Telescope Array (NuSTAR). A Pegasus XL rocket is being prepared to launch NuSTAR into space in March. Once processing of the rocket and spacecraft are completed at Vandenberg, they will be flown on the Orbital Sciences’ L-1011 carrier aircraft to the Ronald Reagan Ballistic Missile Defense Test Site at the Pacific Ocean’s Kwajalein Atoll for launch. NuSTAR, a high-energy x-ray telescope, will conduct a census for black holes, map radioactive material in young supernovae remnants, and study the origins of cosmic rays and the extreme physics around collapsed stars. For more information, visit http://www.nasa.gov/nustar. Photo credit: NASA/Randy Beaudoin, VAFB

Simulation of the Impact of New Aircraft and Satellite-Based Ocean Surface Wind Measurements on H*Wind Analyses

NASA Technical Reports Server (NTRS)

Miller, TImothy L.; Atlas, R. M.; Black, P. G.; Case, J. L.; Chen, S. S.; Hood, R. E.; Johnson, J. W.; Jones, L.; Ruf, C. S.; Uhlborn, E. W.

2008-01-01

Accurate observations of surface ocean vector winds (OVW) with high spatial and temporal resolution are required for understanding and predicting tropical cyclones. As NASA's QuikSCAT and Navy's WindSat operate beyond their design life, many members of the weather and climate science communities recognize the importance of developing new observational technologies and strategies to meet the essential need for OVW information to improve hurricane intensity and location forecasts. The Hurricane Imaging Radiometer (HIRAD) is an innovative technology development which offers new and unique remotely sensed satellite observations of both extreme oceanic wind events and strong precipitation. It is based on the airborne Stepped Frequency Microwave Radiometer (SFMR), which is the only proven remote sensing technique for observing tropical cyclone (TC) ocean surface wind speeds and rain rates. The proposed HIRAD instrument advances beyond the current nadir viewing SFMR to an equivalent wide-swath SFMR imager using passive microwave synthetic thinned aperture radiometer (STAR) technology. This sensor will operate over 4-7 GHz (C-band frequencies) where the required TC remote sensing physics has been validated by both SFMR and WindSat radiometers. The instrument is described in more detail in a paper by Jones et al. presented to the Tropical Meteorology Special Symposium at this AMS Annual Meeting. Simulated HIRAD passes through a simulation of hurricane Frances are being developed to demonstrate HIRAD estimation of surface wind speed over a wide swath in the presence of heavy rain. These are currently being used in "quick" OSSEs (Observing System Simulation Experiments) with H'Wind analyses as the discriminating tool. The H'Wind analysis, a product of the Hurricane Research Division of NOAA's Atlantic , Oceanographic and Meteorological Laboratory, brings together wind measurements from a variety of observation platforms into an objective analysis of the distribution of wind speeds in a tropical cyclone. This product is designed to improve understanding of the extent and strength of the wind field, and to improve the assessment of hurricane intensity. See http://www.aoml.noaa._ov/hrd/data sub/wind.html. Observations have been simulated from both aircraft altitudes and space. The simulated flight patterns for the aircraft platform cases have been designed to duplicate the timing and flight patterns used in routine NOAA and USAF hurricane surveillance flights, and the spaceborne case simulates a TRMM orbit and altitude.

Inorganic chemistry in nuclear imaging and radiotherapy: current and future directions

PubMed Central

Carroll, Valerie; Demoin, Dustin W.; Hoffman, Timothy J; Jurisson, Silvia S

2013-01-01

Summary Radiometals play an important role in diagnostic and therapeutic radiopharmaceuticals. This field of radiochemistry is multidisciplinary, involving radiometal production, separation of the radiometal from its target, chelate design for complexing the radiometal in a biologically stable environment, specific targeting of the radiometal to its in vivo site, and nuclear imaging and/or radiotherapy applications of the resultant radiopharmaceutical. The critical importance of inorganic chemistry in the design and application of radiometal-containing imaging and therapy agents is described from a historical perspective to future directions. PMID:25382874

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

Steele, Amy; Hughes, A. Meredith; Carpenter, John

The presence of debris disks around young main-sequence stars hints at the existence and structure of planetary systems. Millimeter-wavelength observations probe large grains that trace the location of planetesimal belts. The Formation and Evolution of Planetary Systems Spitzer Legacy survey of nearby young solar analogues yielded a sample of five debris disk-hosting stars with millimeter flux suitable for interferometric follow-up. We present observations with the Submillimeter Array (SMA) and the Combined Array for Research in Millimeter-wave Astronomy at ∼2″ resolution that spatially resolve the debris disks around these nearby (d ∼ 50 pc) stars. Two of the five disks (HDmore » 377, HD 8907) are spatially resolved for the first time and one (HD 104860) is resolved at millimeter wavelengths for the first time. We combine our new observations with archival SMA and Atacama Large Millimeter/Submillimeter Array data to enable a uniform analysis of the full five-object sample. We simultaneously model the broadband photometric data and resolved millimeter visibilities to constrain the dust temperatures and disk morphologies, and perform a Markov Chain Monte Carlo analysis to fit for basic structural parameters. We find that the radii and widths of the cold outer belts exhibit properties consistent with scaled-up versions of the Solar System's Kuiper Belt. All the disks exhibit characteristic grain sizes comparable to the blowout size, and all the resolved observations of emission from large dust grains are consistent with an axisymmetric dust distribution to within the uncertainties. These results are consistent with comparable studies carried out at infrared wavelengths.« less

Determination and characterization of the Hubble Space Telescope pointing stability

NASA Technical Reports Server (NTRS)

Bradley, A. J.; Connor, C. T.; Del Toro, Y.; Andersen, G. C.; Bely, Pierre Y.; Decker, J.; Franz, O. G.; Wasserman, L. H.; Van Altena, William F.

1993-01-01

The Hubble Space Telescope (HST) was designed to maintian a pointing stability (jitter) of 0.007 arc seconds rms throughout every observing period, which can last from a few seconds to several orbits. On-orbit measurements indicate that the hardware excitation induced by the reaction wheels. gyros, high gain antennae, science instrument mechanisms and tape recorders are well within specifications. Unexpectedly, the solar arrays because the dominant source of jitter. Every passage through an orbital terminator produces vibrations which emanate from the solar arrays due to thermal effects, which affect the relative positional stability. Broadband frequencies centered about 0.11 and 0.65 Hz were detected in the frequency content of the vehicle jitter. On-board modifications to the control law have attenuated the disturbance torques and reduced the vehicle jitter close to specification. Replacement of the solar arrays in December, 1993, should eliminate the torque distubances. Astrometric science observations are extremely susceptible to corruption from vehicle jitter. The removal of vehicle jitter from astrometric Transfer function scans of binary stars is explained in detail. A binary star separation of 16 milli-seconds of arc has been achieved, a separation resolution of 10 to 12 milli-seconds of arc appears feasible, with a binary star magnitude of 9 m(sub V). The achievement of this resolution is in part due to vehicle jitter removal. Comparison of vehicle jitter measurements from the position path of the vehicle control law, or from the guiding Fine Guidance Sensors (FGS), are shown to be equivalent to approximately 0.001 arc second.

Interferometric Gravity Darkening Observations of Vega with the CHARA Array

NASA Astrophysics Data System (ADS)

Aufdenberg, J. P.; Merand, A.; Coude Foresto, V.; Absil, O.; Di Folco, E.; Kervella, P.; Ridgway, S. T.; Sturmann, J.; Sturmann, L.; ten Brummelaar, T. A.; Turner, N. H.; Berger, D. H.; McAlister, H. A.

2005-12-01

We have obtained high-precision interferometric measurements of the A0 V standard star Vega with the Center for High Angular Resolution Astronomy (CHARA) Array and the Fiber Linked Unit for Optical Recombination (FLUOR) beam combiner in the K' band at projected baselines between 103 m and 273 m. The measured squared visibility amplitudes beyond the first lobe are significantly weaker than expected for a slowly rotating star and provide strong evidence for the model of Vega as a rapidly rotating star viewed very nearly pole on. We have constructed a Roche-von Zeipel gravity-darkened model atmosphere which is in generally good agreement with both our interferometric data and archival spectrophotometry. Our model indicates Vega is rotating at ˜92% of its angular break-up rate with an equatorial velocity of ˜275 km s-1. We find a polar effective temperature of ˜10150 K and a pole-to-equator effective temperature difference of ˜2500 K, much larger than the ˜300 K derived by Gulliver, Hill, and Adelman. Our model suggests that Vega's cool equatorial atmosphere may have significant convective flux and predicts a significantly cooler spectral energy distribution for Vega as seen by its surrounding debris disk. This work was performed in part under contract with the Jet Propulsion Laboratory (JPL) funded by NASA through the Michelson Fellowship Program. JPL is managed for NASA by the California Institute of Technology. The CHARA Array is operated by the Center for High Angular Resolution Astronomy with support from Georgia State University and the National Science Foundation, the Keck Foundation and the Packard Foundation.

Determination and characterization of the Hubble Space Telescope pointing stability

NASA Astrophysics Data System (ADS)

Bradley, A. J.; Connor, C. T.; del Toro, Y.; Andersen, G. C.; Bely, Pierre Y.; Decker, J.; Franz, O. G.; Wasserman, L. H.; van Altena, William F.

The Hubble Space Telescope (HST) was designed to maintian a pointing stability (jitter) of 0.007 arc seconds rms throughout every observing period, which can last from a few seconds to several orbits. On-orbit measurements indicate that the hardware excitation induced by the reaction wheels. gyros, high gain antennae, science instrument mechanisms and tape recorders are well within specifications. Unexpectedly, the solar arrays because the dominant source of jitter. Every passage through an orbital terminator produces vibrations which emanate from the solar arrays due to thermal effects, which affect the relative positional stability. Broadband frequencies centered about 0.11 and 0.65 Hz were detected in the frequency content of the vehicle jitter. On-board modifications to the control law have attenuated the disturbance torques and reduced the vehicle jitter close to specification. Replacement of the solar arrays in December, 1993, should eliminate the torque distubances. Astrometric science observations are extremely susceptible to corruption from vehicle jitter. The removal of vehicle jitter from astrometric Transfer function scans of binary stars is explained in detail. A binary star separation of 16 milli-seconds of arc has been achieved, a separation resolution of 10 to 12 milli-seconds of arc appears feasible, with a binary star magnitude of 9 m(sub V). The achievement of this resolution is in part due to vehicle jitter removal. Comparison of vehicle jitter measurements from the position path of the vehicle control law, or from the guiding Fine Guidance Sensors (FGS), are shown to be equivalent to approximately 0.001 arc second.

MULTI-MESSENGER ASTRONOMY OF GRAVITATIONAL-WAVE SOURCES WITH FLEXIBLE WIDE-AREA RADIO TRANSIENT SURVEYS

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

Yancey, Cregg C.; Shawhan, Peter; Bear, Brandon E.

We explore opportunities for multi-messenger astronomy using gravitational waves (GWs) and prompt, transient low-frequency radio emission to study highly energetic astrophysical events. We review the literature on possible sources of correlated emission of GWs and radio transients, highlighting proposed mechanisms that lead to a short-duration, high-flux radio pulse originating from the merger of two neutron stars or from a superconducting cosmic string cusp. We discuss the detection prospects for each of these mechanisms by low-frequency dipole array instruments such as LWA1, the Low Frequency Array and the Murchison Widefield Array. We find that a broad range of models may bemore » tested by searching for radio pulses that, when de-dispersed, are temporally and spatially coincident with a LIGO/Virgo GW trigger within a ∼30 s time window and ∼200–500 deg{sup 2} sky region. We consider various possible observing strategies and discuss their advantages and disadvantages. Uniquely, for low-frequency radio arrays, dispersion can delay the radio pulse until after low-latency GW data analysis has identified and reported an event candidate, enabling a prompt radio signal to be captured by a deliberately targeted beam. If neutron star mergers do have detectable prompt radio emissions, a coincident search with the GW detector network and low-frequency radio arrays could increase the LIGO/Virgo effective search volume by up to a factor of ∼2. For some models, we also map the parameter space that may be constrained by non-detections.« less

On-sky performance evaluation and calibration of a polarization-sensitive focal plane array

NASA Astrophysics Data System (ADS)

Vorobiev, Dmitry; Ninkov, Zoran; Brock, Neal; West, Ray

2016-07-01

The advent of pixelated micropolarizer arrays (MPAs) has facilitated the development of polarization-sensitive focal plane arrays (FPAs) based on charge-coupled devices (CCDs) and active pixel sensors (APSs), which are otherwise only able to measure the intensity of light. Polarization sensors based on MPAs are extremely compact, light-weight, mechanically robust devices with no moving parts, capable of measuring the degree and angle of polarization of light in a single snapshot. Furthermore, micropolarizer arrays based on wire grid polarizers (so called micro-grid polarizers) offer extremely broadband performance, across the optical and infrared regimes. These devices have potential for a wide array of commercial and research applications, where measurements of polarization can provide critical information, but where conventional polarimeters could be practically implemented. To date, the most successful commercial applications of these devices are 4D Technology's PhaseCam laser interferometers and PolarCam imaging polarimeters. Recently, MPA-based polarimeters have been identified as a potential solution for space-based telescopes, where the small size, snapshot capability and low power consumption (offered by these devices) are extremely desirable. In this work, we investigated the performance of MPA-based polarimeters designed for astronomical polarimetry using the Rochester Institute of Technology Polarization Imaging Camera (RITPIC). We deployed RITPIC on the 0.9 meter SMARTS telescope at the Cerro Tololo Inter-American Observatory and observed a variety of astronomical objects (calibration stars, variable stars, reflection nebulae and planetary nebulae). We use our observations to develop calibration procedures that are unique to these devices and provide an estimate for polarimetric precision that is achievable.

Narrow Angle Wide Spectral Range Radiometer Design FEANICS/REEFS Radiometer Design Report

NASA Technical Reports Server (NTRS)

Camperchioli, William

2005-01-01

A critical measurement for the Radiative Enhancement Effects on Flame Spread (REEFS) microgravity combustion experiment is the net radiative flux emitted from the gases and from the solid fuel bed. These quantities are measured using a set of narrow angle, wide spectral range radiometers. The radiometers are required to have an angular field of view of 1.2 degrees and measure over the spectral range of 0.6 to 30 microns, which presents a challenging design effort. This report details the design of this radiometer system including field of view, radiometer response, radiometric calculations, temperature effects, error sources, baffling and amplifiers. This report presents some radiometer specific data but does not present any REEFS experiment data.

Factors affecting calculation of L

NASA Astrophysics Data System (ADS)

Ciotola, Mark P.

2001-08-01

A detectable extraterrestrial civilization can be modeled as a series of successive regimes over time each of which is detectable for a certain proportion of its lifecycle. This methodology can be utilized to produce an estimate for L. Potential components of L include quantity of fossil fuel reserves, solar energy potential, quantity of regimes over time, lifecycle patterns of regimes, proportion of lifecycle regime is actually detectable, and downtime between regimes. Relationships between these components provide a means of calculating the lifetime of communicative species in a detectable state, L. An example of how these factors interact is provided, utilizing values that are reasonable given known astronomical data for components such as solar energy potential while existing knowledge about the terrestrial case is used as a baseline for other components including fossil fuel reserves, quantity of regimes over time, and lifecycle patterns of regimes, proportion of lifecycle regime is actually detectable, and gaps of time between regimes due to recovery from catastrophic war or resource exhaustion. A range of values is calculated for L when parameters are established for each component so as to determine the lowest and highest values of L. roadmap for SETI research at the SETI Institute for the next few decades. Three different approaches were identified. 1) Continue the radio search: build an affordable array incorporating consumer market technologies, expand the search frequency, and increase the target list to 100,000 stars. This array will also serve as a technology demonstration and enable the international radio astronomy community to realize an array that is a hundred times larger and capable (among other things) of searching a million stars. 2) Begin searches for very fast optical pulses from a million stars. 3) As Moore's Law delivers increased computational capacity, build an omni-directional sky survey array capable of detecting strong, transient, radio signals from billions of stars. SETI could succeed tomorrow, or it may be an endeavor for multiple generations. We are a very young technology in a very old galaxy. While our own leakage radiation continues to outshine the Sun at many frequencies, we remain detectable to others. When our use of the spectrum becomes more efficient, it will be time to consider deliberate transmissions and the really tough questions: Who will speak for Earth? What will they say?

Devastated Stellar Neighborhood

NASA Technical Reports Server (NTRS)

2008-01-01

This image from NASA's Spitzer Space Telescope shows the nasty effects of living near a group of massive stars: radiation and winds from the massive stars (white spot in center) are blasting planet-making material away from stars like our sun. The planetary material can be seen as comet-like tails behind three stars near the center of the picture. The tails are pointing away from the massive stellar furnaces that are blowing them outward.

The picture is the best example yet of multiple sun-like stars being stripped of their planet-making dust by massive stars.

The sun-like stars are about two to three million years old, an age when planets are thought to be growing out of surrounding disks of dust and gas. Astronomers say the dust being blown from the stars is from their outer disks. This means that any Earth-like planets forming around the sun-like stars would be safe, while outer planets like Uranus might be nothing more than dust in the wind.

This image shows a portion of the W5 star-forming region, located 6,500 light-years away in the constellation Cassiopeia. It is a composite of infrared data from Spitzer's infrared array camera and multiband imaging photometer. Light with a wavelength of 3.5 microns is blue, while light from the dust of 24 microns is orange-red.

VizieR Online Data Catalog: Main-sequence A, F, G, and K stars photometry (Boyajian+, 2013)

NASA Astrophysics Data System (ADS)

Boyajian, T. S.; von Braun, K.; van Belle, G.; Farrington, C.; Schaefer, G.; Jones, J.; White, R.; McAlister, H. A.; Ten Brummelaar, T. A.; Ridgway, S.; Gies, D.; Sturmann, L.; Sturmann, J.; Turner, N. H.; Goldfinger, P. J.; Vargas, N.

2016-07-01

Akin to the observing outlined in DT1 and DT2, observations for this project were made with the CHARA Array, a long-baseline optical/infrared interferometer located on Mount Wilson Observatory in southern California. The target stars were selected based on their approximate angular size (a function of their intrinsic linear size and distance to the observer). We limit the selection to stars with angular sizes >0.45mas, in order to adequately resolve their sizes to a few percent precision with the selected instrument setup. Note that all stars that meet this requirement are brighter than the instrumental limits of our detector by several magnitudes. The stars also have no known stellar companion within 3-arcsec to avoid contamination of incoherent light in the interferometers' field of view. From 2008 to 2012, we used the CHARA Classic beam combiner operating in the H band (λH=1.67um) and the K' band (λK'=2.14um) to collect observations of 23 stars using CHARA's longest baseline combinations. (5 data files).

Performance of the Satellite Test Assistant Robot in JPL's Space Simulation Facility

NASA Technical Reports Server (NTRS)

Mcaffee, Douglas; Long, Mark; Johnson, Ken; Siebes, Georg

1995-01-01

An innovative new telerobotic inspection system called STAR (the Satellite Test Assistant Robot) has been developed to assist engineers as they test new spacecraft designs in simulated space environments. STAR operates inside the ultra-cold, high-vacuum, test chambers and provides engineers seated at a remote Operator Control Station (OCS) with high resolution video and infrared (IR) images of the flight articles under test. STAR was successfully proof tested in JPL's 25-ft (7.6-m) Space Simulation Chamber where temperatures ranged from +85 C to -190 C and vacuum levels reached 5.1 x 10(exp -6) torr. STAR's IR Camera was used to thermally map the entire interior of the chamber for the first time. STAR also made several unexpected and important discoveries about the thermal processes occurring within the chamber. Using a calibrated test fixture arrayed with ten sample spacecraft materials, the IR camera was shown to produce highly accurate surface temperature data. This paper outlines STAR's design and reports on significant results from the thermal vacuum chamber test.

The first focused hard X-ray images of the sun with NuSTAR

DOE PAGES

Grefenstette, Brian W.; Glesener, Lindsay; Krucker, Sam; ...

2016-07-18

Here, we present results from the the first campaign of dedicated solar observations undertaken by the Nuclear Spectroscopic Telescope ARray (NuSTAR) hard X-ray (HXR) telescope. Designed as an astrophysics mission, NuSTAR nonetheless has the capability of directly imaging the Sun at HXR energies (>3 keV) with an increase in sensitivity of at least two magnitude compared to current non-focusing telescopes. In this paper we describe the scientific areas where NuSTAR will make major improvements on existing solar measurements. We report on the techniques used to observe the Sun with NuSTAR, their limitations and complications, and the procedures developed to optimizemore » solar data quality derived from our experience with the initial solar observations. These first observations are briefly described, including the measurement of the Fe K-shell lines in a decaying X-class flare, HXR emission from high in the solar corona, and full-disk HXR images of the Sun.« less

Is there a propeller neutron star in γ Cas?

NASA Astrophysics Data System (ADS)

Smith, M. A.; Lopes de Oliveira, R.; Motch, C.

2017-08-01

γ Cas is the prototype of a small population of B0-B1.5 III-V classical Be (cBe) stars that emit anomalous and hard X-rays with a unique array of properties. γ Cas is known to host, like other cBe stars, a decretion disc and also a low-mass companion. Recently, Postnov et al. have posited that this companion is a magnetized rapidly spinning neutron star that deflects direct gravitational accretion from a stellar/disc wind via the 'propeller mechanism'. These authors state that the key X-ray observations are 'remarkably well produced' in this scenario. We re-examine this mechanism in detail and conclude that there are a number of fatal objections in its application to the γ Cas case. Among other considerations these issues include the prediction under the propeller scenario of a much smaller population of γ Cas stars than is observed and the lack of allowance for observed correlations of X-ray and UV and/or optical properties over a variety of time-scales.

Dust formation and wind acceleration around the aluminum oxide-rich AGB star W Hydrae

NASA Astrophysics Data System (ADS)

Takigawa, Aki; Kamizuka, Takafumi; Tachibana, Shogo; Yamamura, Issei

2017-11-01

Dust grains, formed around asymptotic giant branch (AGB) stars, are accelerated by stellar radiation to drive stellar winds, which supply freshly synthesized nuclides to the Galaxy. Silicate is the dominant dust species in space, but 40% of oxygen-rich AGB stars are thought to have comparable amounts of aluminum oxide dust. Dust formation and the wind-driving mechanism around these oxygen-rich stars, however, are poorly understood. We report on the spatial distributions of AlO and 29SiO molecules around an aluminum oxide-rich M-type AGB star, W Hydrae, based on observations obtained with the Atacama Large Millimeter/submillimeter Array. AlO molecules were only observed within three stellar radii (Rstar), whereas 29SiO was distributed in the accelerated wind beyond 5 Rstar without significant depletion. This strongly suggests that condensed aluminum oxide dust plays a key role in accelerating the stellar wind and in preventing the efficient formation of silicate dust around W Hydrae.

Cosmic evolution of star formation properties of galaxies

NASA Astrophysics Data System (ADS)

Kim, Sungeun

2014-01-01

Development of bolometer array and camera at submillimeter wavelength has played an important role in detecting submillimeter bright galaxies, so called submillimeter galaxies. These galaxies seem to be progenitors of present-day massive galaxies and account for their considerable contributions to the light from the early universe and their expected high star formation rates if there is a close link between the submillimeter galaxies and the star formation activities, and the interstellar dust in galaxies is mainly heated by the star light. We review assembly of submillimeter galaxies chosen from the AzTEC and the Herschel SPIRE/PACS data archives, and investigate their spectral energy distribution fits including the data at other wavelengths to deduce details about stellar parameters including star formation rates and parameters yielding the metallicity, composition and abundance in dust, and disc structure of these galaxies. This work has been supported in part by Mid-career Researcher Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology 2011-0028001.

The first focused hard X-ray images of the sun with NuSTAR

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

Grefenstette, Brian W.; Glesener, Lindsay; Krucker, Sam

Here, we present results from the the first campaign of dedicated solar observations undertaken by the Nuclear Spectroscopic Telescope ARray (NuSTAR) hard X-ray (HXR) telescope. Designed as an astrophysics mission, NuSTAR nonetheless has the capability of directly imaging the Sun at HXR energies (>3 keV) with an increase in sensitivity of at least two magnitude compared to current non-focusing telescopes. In this paper we describe the scientific areas where NuSTAR will make major improvements on existing solar measurements. We report on the techniques used to observe the Sun with NuSTAR, their limitations and complications, and the procedures developed to optimizemore » solar data quality derived from our experience with the initial solar observations. These first observations are briefly described, including the measurement of the Fe K-shell lines in a decaying X-class flare, HXR emission from high in the solar corona, and full-disk HXR images of the Sun.« less

THE FIRST FOCUSED HARD X-RAY IMAGES OF THE SUN WITH NuSTAR

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

Grefenstette, Brian W.; Madsen, Kristin K.; Forster, Karl

We present results from the the first campaign of dedicated solar observations undertaken by the Nuclear Spectroscopic Telescope ARray ( NuSTAR ) hard X-ray (HXR) telescope. Designed as an astrophysics mission, NuSTAR nonetheless has the capability of directly imaging the Sun at HXR energies (>3 keV) with an increase in sensitivity of at least two magnitude compared to current non-focusing telescopes. In this paper we describe the scientific areas where NuSTAR will make major improvements on existing solar measurements. We report on the techniques used to observe the Sun with NuSTAR , their limitations and complications, and the procedures developedmore » to optimize solar data quality derived from our experience with the initial solar observations. These first observations are briefly described, including the measurement of the Fe K-shell lines in a decaying X-class flare, HXR emission from high in the solar corona, and full-disk HXR images of the Sun.« less

Dust formation and wind acceleration around the aluminum oxide–rich AGB star W Hydrae

PubMed Central

Takigawa, Aki; Kamizuka, Takafumi; Tachibana, Shogo; Yamamura, Issei

2017-01-01

Dust grains, formed around asymptotic giant branch (AGB) stars, are accelerated by stellar radiation to drive stellar winds, which supply freshly synthesized nuclides to the Galaxy. Silicate is the dominant dust species in space, but ~40% of oxygen-rich AGB stars are thought to have comparable amounts of aluminum oxide dust. Dust formation and the wind-driving mechanism around these oxygen-rich stars, however, are poorly understood. We report on the spatial distributions of AlO and 29SiO molecules around an aluminum oxide–rich M-type AGB star, W Hydrae, based on observations obtained with the Atacama Large Millimeter/submillimeter Array. AlO molecules were only observed within three stellar radii (Rstar), whereas 29SiO was distributed in the accelerated wind beyond 5 Rstar without significant depletion. This strongly suggests that condensed aluminum oxide dust plays a key role in accelerating the stellar wind and in preventing the efficient formation of silicate dust around W Hydrae. PMID:29109978

Aerosol and cloud properties derived from hyperspectral transmitted light in the southeast Atlantic sampled during field campaign deployments in 2016 and 2017

NASA Astrophysics Data System (ADS)

LeBlanc, S. E.; Redemann, J.; Flynn, C. J.; Segal-Rosenhaimer, M.; Kacenelenbogen, M. S.; Shinozuka, Y.; Pistone, K.; Karol, Y.; Schmidt, S.; Cochrane, S.; Chen, H.; Meyer, K.; Ferrare, R. A.; Burton, S. P.; Hostetler, C. A.; Hair, J. W.

2017-12-01

We present aerosol and cloud properties collected from airborne remote-sensing measurements in the southeast Atlantic during the recent NASA ObseRvations of CLouds above Aerosols and their intEractionS (ORACLES) field campaign. During the biomass burning seasons of September 2016 and August 2017, we sampled aerosol layers which overlaid marine stratocumulus clouds off the southwestern coast of Africa. We sampled these aerosol layers and the underlying clouds from the NASA P3 airborne platform with the Spectrometer for Sky-Scanning, Sun-Tracking Atmospheric Research (4STAR). Aerosol optical depth (AOD), along with trace gas content in the atmospheric column (water vapor, NO2, and O3), is obtained from the attenuation in the sun's direct beam, measured at the altitude of the airborne platform. Using hyperspectral transmitted light measurements from 4STAR, in conjunction with hyperspectral hemispheric irradiance measurements from the Solar Spectral Flux Radiometers (SSFR), we also obtained aerosol intensive properties (asymmetry parameter, single scattering albedo), aerosol size distributions, cloud optical depth (COD), cloud particle effective radius, and cloud thermodynamic phase. Aerosol intensive properties are retrieved from measurements of angularly resolved skylight and flight level spectral albedo using the inversion used with measurements from AERONET (Aerosol Robotic Network) that has been modified for airborne use. The cloud properties are obtained from 4STAR measurements of scattered light below clouds. We show a favorable initial comparison of the above-cloud AOD measured by 4STAR to this same product retrieved from measurements by the MODIS instrument on board the TERRA and AQUA satellites. The layer AOD observed above clouds will also be compared to integrated aerosol extinction profile measurements from the High Spectral Resolution Lidar-2 (HSRL-2).

A Blind Search for Magnetospheric Emissions from Planetary Companions to Nearby Solar-type Stars

NASA Astrophysics Data System (ADS)

Lazio, T. Joseph W.; Carmichael, S.; Clark, J.; Elkins, E.; Gudmundsen, P.; Mott, Z.; Szwajkowski, M.; Hennig, L. A.

2010-01-01

This paper reports a blind search for planetary magnetospheric emissions from planets around nearby stars. Young stars are likely to have much stronger stellar winds than the Sun, and because planetary magnetospheric emissions are powered by stellar winds, stronger stellar winds may enhance the radio luminosity of any orbiting planets. Using various stellar catalogs, we selected nearby stars (< 30 pc) with relatively young age estimates (< 3 Gyr), finding between 100 and several hundred stars. We stacked images from the 74-MHz (4-m wavelength) VLA Low-frequency Sky Survey, obtaining 3\\sigma limits on planetary emission of between 10 and 33 mJy. These flux density limits correspond to average planetary luminosities less than 5--10 x 1023erg/s. Using models for the scaling of stellar wind velocity, density, and magnetic field with stellar age, we estimate scaling factors for the strength of stellar winds, relative to the Sun, in our samples. The typical kinetic (magnetic) energy carried by the stellar winds in our samples is 15--50 (5--10) times larger than that of the solar wind. If we assume that every star is orbited by a Jupiter-like planet with a luminosity larger than that of the Jovian decametric radiation by the above factors, our limits on planetary luminosities from the stacking analysis are likely to be a factor of 300 above what would be required to detect the planets in a statistical sense. Similar statistical analyses with observations by future instruments, such as the Low Frequency Array (LOFAR) and the Long Wavelength Array (LWA), offer the promise of improvements by factors of 10--100. Basic research in radio astronomy at NRL is supported by 6.1 Base funding. The LUNAR consortium, is funded by the NASA Lunar Science Institute (Cooperative Agreement NNA09DB30A) to investigate concepts for astrophysical observatories on the Moon.

A first look for molecules between 103 and 133 MHz using the Murchison Widefield Array

NASA Astrophysics Data System (ADS)

Tremblay, Chenoa D.; Hurley-Walker, Natasha; Cunningham, Maria; Jones, Paul A.; Hancock, Paul J.; Wayth, Randall; Jordan, Christopher H.

2017-11-01

We detail and present results from a pilot study to assess the feasibility of detecting molecular lines at low radio frequencies. We observed a 400 square degree region centred on the Galactic Centre with the Murchison Widefield Array between 103 and 133 MHz targeting 28 known molecular species that have significant transitions. The results of this survey yield tentative detections of nitric oxide (NO) and the mercapto radical (SH). Both of these molecules appear to be associated with evolved stars.

Microwave monolithic integrated circuit development for future spaceborne phased array antennas

NASA Astrophysics Data System (ADS)

Anzic, G.; Kascak, T. J.; Downey, A. N.; Liu, D. C.; Connolly, D. J.

The development of fully monolithic gallium arsenide (GaAs) receive and transmit modules suitable for phased array antenna applications in the 30/20 gigahertz bands is presented. Specifications and various design approaches to achieve the design goals are described. Initial design and performance of submodules and associated active and passive components are presented. A tradeoff study summary is presented, highlighting the advantages of a distributed amplifier approach compared to the conventional single power source designs. Previously announced in STAR as N84-13399

Microwave monolithic integrated circuit development for future spaceborne phased array antennas

NASA Technical Reports Server (NTRS)

Anzic, G.; Kascak, T. J.; Downey, A. N.; Liu, D. C.; Connolly, D. J.

1984-01-01

The development of fully monolithic gallium arsenide (GaAs) receive and transmit modules suitable for phased array antenna applications in the 30/20 gigahertz bands is presented. Specifications and various design approaches to achieve the design goals are described. Initial design and performance of submodules and associated active and passive components are presented. A tradeoff study summary is presented, highlighting the advantages of a distributed amplifier approach compared to the conventional single power source designs. Previously announced in STAR as N84-13399

Single-Pole Double-Throw MMIC Switches for a Microwave Radiometer

NASA Technical Reports Server (NTRS)

Montes, Oliver; Dawson, Douglas E.; Kangaslahti, Pekka P.

2012-01-01

In order to reduce the effect of gain and noise instabilities in the RF chain of a microwave radiometer, a Dicke radiometer topology is often used, as in the case of the proposed surface water and ocean topography (SWOT) radiometer instrument. For this topology, a single-pole double-throw (SPDT) microwave switch is needed, which must have low insertion loss at the radiometer channel frequencies to minimize the overall receiver noise figure. Total power radiometers are limited in accuracy due to the continuous variation in gain of the receiver. High-frequency SPDT switches were developed in the form of monolithic microwave integrated circuits (MMICs) using 75 micron indium phosphide (InP) PIN-diode technology. These switches can be easily integrated into Dicke switched radiometers that utilize microstrip technology.

Stellar Jewels Shine in New Spitzer Image

NASA Technical Reports Server (NTRS)

2004-01-01

One of the most prolific birthing grounds in our Milky Way galaxy, a nebula called RCW 49, is exposed in superb detail for the first time in this new image from NASA's Spitzer Space Telescope. Located 13,700 light-years away in the southern constellation Centaurus, RCW 49 is a dark and dusty stellar nursery that houses more than 2,200 stars.

Because many of the stars in RCW 49 are deeply embedded in plumes of dust, they cannot be seen at visible wavelengths. When viewed with Spitzer's infrared eyes, however, RCW 49 becomes transparent. Like cracking open a quartz rock to discover its jewels inside, the nebula's newborn stars have been dramatically exposed.

This image taken by Spitzer's infrared array camera highlights the nebula's older stars (blue stars in center pocket), its gas filaments (green) and dusty tendrils (pink). Speckled throughout the murky clouds are more than 300 never-before-seen newborn stars.

Astronomers are interested in further studying these newfound proto-stars because they offer a fresh look at star formation in our own galaxy.

This image was taken on Dec. 23, 2003, and is composed of photographs obtained at four wavelengths: 3.6 microns (blue), 4.5 microns (green), 5.8 microns (orange) and 8 microns (red).

Stellar Jewels Shine in New Spitzer Image

NASA Image and Video Library

2004-05-27

One of the most prolific birthing grounds in our Milky Way galaxy, a nebula called RCW 49, is exposed in superb detail for the first time in this new image from NASA's Spitzer Space Telescope. Located 13,700 light-years away in the southern constellation Centaurus, RCW 49 is a dark and dusty stellar nursery that houses more than 2,200 stars. Because many of the stars in RCW 49 are deeply embedded in plumes of dust, they cannot be seen at visible wavelengths. When viewed with Spitzer's infrared eyes, however, RCW 49 becomes transparent. Like cracking open a quartz rock to discover its jewels inside, the nebula's newborn stars have been dramatically exposed. This image taken by Spitzer's infrared array camera highlights the nebula's older stars (blue stars in center pocket), its gas filaments (green) and dusty tendrils (pink). Speckled throughout the murky clouds are more than 300 never-before-seen newborn stars. Astronomers are interested in further studying these newfound proto-stars because they offer a fresh look at star formation in our own galaxy. This image was taken on Dec. 23, 2003, and is composed of photographs obtained at four wavelengths: 3.6 microns (blue), 4.5 microns (green), 5.8 microns (orange) and 8 microns (red). http://photojournal.jpl.nasa.gov/catalog/PIA05989

New Views of a Familiar Beauty

NASA Technical Reports Server (NTRS)

2005-01-01

[figure removed for brevity, see original site] Figure 1

[figure removed for brevity, see original site] [figure removed for brevity, see original site] Figure 2Figure 3Figure 4Figure 5

This image composite compares the well-known visible-light picture of the glowing Trifid Nebula (left panel) with infrared views from NASA's Spitzer Space Telescope (remaining three panels). The Trifid Nebula is a giant star-forming cloud of gas and dust located 5,400 light-years away in the constellation Sagittarius.

The false-color Spitzer images reveal a different side of the Trifid Nebula. Where dark lanes of dust are visible trisecting the nebula in the visible-light picture, bright regions of star-forming activity are seen in the Spitzer pictures. All together, Spitzer uncovered 30 massive embryonic stars and 120 smaller newborn stars throughout the Trifid Nebula, in both its dark lanes and luminous clouds. These stars are visible in all the Spitzer images, mainly as yellow or red spots. Embryonic stars are developing stars about to burst into existence. Ten of the 30 massive embryos discovered by Spitzer were found in four dark cores, or stellar 'incubators,' where stars are born. Astronomers using data from the Institute of Radioastronomy millimeter telescope in Spain had previously identified these cores but thought they were not quite ripe for stars. Spitzer's highly sensitive infrared eyes were able to penetrate all four cores to reveal rapidly growing embryos.

Astronomers can actually count the individual embryos tucked inside the cores by looking closely at the Spitzer image taken by its infrared array camera (figure 4). This instrument has the highest spatial resolution of Spitzer's imaging cameras. The Spitzer image from the multiband imaging photometer (figure 5), on the other hand, specializes in detecting cooler materials. Its view highlights the relatively cool core material falling onto the Trifid's growing embryos. The middle panel is a combination of Spitzer data from both of these instruments.

The embryos are thought to have been triggered by a massive 'type O' star, which can be seen as a white spot at the center of the nebula in all four images. Type O stars are the most massive stars, ending their brief lives in explosive supernovas. The small newborn stars probably arose at the same time as the O star, and from the same original cloud of gas and dust.

The Spitzer infrared array camera image is a three-color composite of invisible light, showing emissions from wavelengths of 3.6 microns (blue), 4.5 microns (green), 5.8 and 8.0 microns (red). The Spitzer multiband imaging photometer image (figure 3) shows 24-micron emissions. The Spitzer mosaic image combines data from these pictures, showing light of 4.5 microns (blue), 8.0 microns (green) and 24 microns (red). The visible-light image (figure 2) is from the National Optical Astronomy Observatory, Tucson, Ariz.

Design of an Airborne L-Band Cross-Track Scanning Scatterometer

NASA Technical Reports Server (NTRS)

Hilliard, Lawrence M. (Technical Monitor)

2002-01-01

In this report, we describe the design of an airborne L-band cross-track scanning scatterometer suitable for airborne operation aboard the NASA P-3 aircraft. The scatterometer is being designed for joint operation with existing L-band radiometers developed by NASA for soil moisture and ocean salinity remote sensing. In addition, design tradeoffs for a space-based radar system have been considered, with particular attention given to antenna architectures suitable for sharing the antenna between the radar and radiometer. During this study, we investigated a number of imaging techniques, including the use of real and synthetic aperture processing in both the along track and cross-track dimensions. The architecture selected will permit a variety of beamforming algorithms to be implemented, although real aperture processing, with hardware beamforming, provides better sidelobe suppression than synthetic array processing and superior signal-to-noise performance. In our discussions with the staff of NASA GSFC, we arrived at an architecture that employs complete transmit/receive modules for each subarray. Amplitude and phase control at each of the transmit modules will allow a low-sidelobe transmit pattern to be generated over scan angles of +/- 50 degrees. Each receiver module will include all electronics necessary to downconvert the received signal to an IF offset of 30 MHz where it will be digitized for further processing.

Advances in real-time millimeter-wave imaging radiometers for avionic synthetic vision

NASA Astrophysics Data System (ADS)

Lovberg, John A.; Chou, Ri-Chee; Martin, Christopher A.; Galliano, Joseph A., Jr.

1995-06-01

Millimeter-wave imaging has advantages over conventional visible or infrared imaging for many applications because millimeter-wave signals can travel through fog, snow, dust, and clouds with much less attenuation than infrared or visible light waves. Additionally, passive imaging systems avoid many problems associated with active radar imaging systems, such as radar clutter, glint, and multi-path return. ThermoTrex Corporation previously reported on its development of a passive imaging radiometer that uses an array of frequency-scanned antennas coupled to a multichannel acousto-optic spectrum analyzer (Bragg-cell) to form visible images of a scene through the acquisition of thermal blackbody radiation in the millimeter-wave spectrum. The output from the Bragg cell is imaged by a standard video camera and passed to a computer for normalization and display at real-time frame rates. An application of this system is its incorporation as part of an enhanced vision system to provide pilots with a synthetic view of a runway in fog and during other adverse weather conditions. Ongoing improvements to a 94 GHz imaging system and examples of recent images taken with this system will be presented. Additionally, the development of dielectric antennas and an electro- optic-based processor for improved system performance, and the development of an `ultra- compact' 220 GHz imaging system will be discussed.

Evaluating the design of satellite scanning radiometers for earth radiation budget measurements with system simulations. Part 1: Instantaneous estimates

NASA Technical Reports Server (NTRS)

Stowe, Larry; Ardanuy, Philip; Hucek, Richard; Abel, Peter; Jacobowitz, Herbert

1991-01-01

A set of system simulations was performed to evaluate candidate scanner configurations to fly as a part of the Earth Radiation Budget Instrument (ERBI) on the polar platforms during the 1990's. The simulation is considered of instantaneous sampling (without diurnal averaging) of the longwave and shortwave fluxes at the top of the atmosphere (TOA). After measurement and subsequent inversion to the TOA, the measured fluxes were compared to the reference fluxes for 2.5 deg lat/long resolution targets. The reference fluxes at this resolution are obtained by integrating over the 25 x 25 = 625 grid elements in each target. The differences between each of these two resultant spatially averaged sets of target measurements (errors) are taken and then statistically summarized. Five instruments are considered: (1) the Conically Scanning Radiometer (CSR); (2) the ERBE Cross Track Scanner; (3) the Nimbus-7 Biaxial Scanner; (4) the Clouds and Earth's Radiant Energy System Instrument (CERES-1); and (5) the Active Cavity Array (ACA). Identical studies of instantaneous error were completed for many days, two seasons, and several satellite equator crossing longitudes. The longwave flux errors were found to have the same space and time characteristics as for the shortwave fluxes, but the errors are only about 25 pct. of the shortwave errors.

Satellite Calibration With LED Detectors at Mud Lake

NASA Technical Reports Server (NTRS)

Hiller, Jonathan D.

2005-01-01

Earth-monitoring instruments in orbit must be routinely calibrated in order to accurately analyze the data obtained. By comparing radiometric measurements taken on the ground in conjunction with a satellite overpass, calibration curves are derived for an orbiting instrument. A permanent, automated facility is planned for Mud Lake, Nevada (a large, homogeneous, dry lakebed) for this purpose. Because some orbiting instruments have low resolution (250 meters per pixel), inexpensive radiometers using LEDs as sensors are being developed to array widely over the lakebed. LEDs are ideal because they are inexpensive, reliable, and sense over a narrow bandwidth. By obtaining and averaging widespread data, errors are reduced and long-term surface changes can be more accurately observed.

Application of the Langley plot for calibration of sun sensors for the Halogen Occultation Experiment (HALOE)

NASA Technical Reports Server (NTRS)

Moore, Alvah S., Jr.; Mauldin, L. ED, III; Stump, Charles W.; Reagan, John A.; Fabert, Milton G.

1989-01-01

The calibration of the Halogen Occultation Experiment (HALOE) sun sensor is described. This system consists of two energy-balancing silicon detectors which provide coarse azimuth and elevation control signals and a silicon photodiode array which provides top and bottom solar edge data for fine elevation control. All three detectors were calibrated on a mountaintop near Tucson, Ariz., using the Langley plot technique. The conventional Langley plot technique was modified to allow calibration of the two coarse detectors, which operate wideband. A brief description of the test setup is given. The HALOE instrument is a gas correlation radiometer that is now being developed for the Upper Atmospheric Research Satellite.

The radio-X-ray relation as a star formation indicator: results from the Very Large Array-Extended Chandra Deep Field-South

NASA Astrophysics Data System (ADS)

Vattakunnel, S.; Tozzi, P.; Matteucci, F.; Padovani, P.; Miller, N.; Bonzini, M.; Mainieri, V.; Paolillo, M.; Vincoletto, L.; Brandt, W. N.; Luo, B.; Kellermann, K. I.; Xue, Y. Q.

2012-03-01

In order to trace the instantaneous star formation rate (SFR) at high redshift, and thus help in understanding the relation between the different emission mechanisms related to star formation, we combine the recent 4-Ms Chandra X-ray data and the deep Very Large Array radio data in the Extended Chandra Deep Field-South region. We find 268 sources detected both in the X-ray and radio bands. The availability of redshifts for ˜95 per cent of the sources in our sample allows us to derive reliable luminosity estimates and the intrinsic properties from X-ray analysis for the majority of the objects. With the aim of selecting sources powered by star formation in both bands, we adopt classification criteria based on X-ray and radio data, exploiting the X-ray spectral features and time variability, taking advantage of observations scattered across more than 10 years. We identify 43 objects consistent with being powered by star formation. We also add another 111 and 70 star-forming candidates detected only in the radio and X-ray bands, respectively. We find a clear linear correlation between radio and X-ray luminosity in star-forming galaxies over three orders of magnitude and up to z˜ 1.5. We also measure a significant scatter of the order of 0.4 dex, higher than that observed at low redshift, implying an intrinsic scatter component. The correlation is consistent with that measured locally, and no evolution with redshift is observed. Using a locally calibrated relation between the SFR and the radio luminosity, we investigate the LX(2-10 keV)-SFR relation at high redshift. The comparison of the SFR measured in our sample with some theoretical models for the Milky Way and M31, two typical spiral galaxies, indicates that, with current data, we can trace typical spirals only at z≤ 0.2, and strong starburst galaxies with SFRs as high as ˜100 M⊙ yr-1, up to z˜ 1.5.

A Massive Prestellar Clump Hosting No High-mass Cores

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

Sanhueza, Patricio; Lu, Xing; Tatematsu, Ken’ichi

The infrared dark cloud (IRDC) G028.23-00.19 hosts a massive (1500 M {sub ⊙}), cold (12 K), and 3.6–70 μ m IR dark clump (MM1) that has the potential to form high-mass stars. We observed this prestellar clump candidate with the Submillimeter Array (∼3.″5 resolution) and Jansky Very Large Array (∼2.″1 resolution) in order to characterize the early stages of high-mass star formation and to constrain theoretical models. Dust emission at 1.3 mm wavelength reveals five cores with masses ≤15 M {sub ⊙}. None of the cores currently have the mass reservoir to form a high-mass star in the prestellar phase.more » If the MM1 clump will ultimately form high-mass stars, its embedded cores must gather a significant amount of additional mass over time. No molecular outflows are detected in the CO (2-1) and SiO (5-4) transitions, suggesting that the SMA cores are starless. By using the NH{sub 3} (1, 1) line, the velocity dispersion of the gas is determined to be transonic or mildly supersonic (Δ V {sub nt}/Δ V {sub th} ∼ 1.1–1.8). The cores are not highly supersonic as some theories of high-mass star formation predict. The embedded cores are four to seven times more massive than the clump thermal Jeans mass and the most massive core (SMA1) is nine times less massive than the clump turbulent Jeans mass. These values indicate that neither thermal pressure nor turbulent pressure dominates the fragmentation of MM1. The low virial parameters of the cores (0.1–0.5) suggest that they are not in virial equilibrium, unless strong magnetic fields of ∼1–2 mG are present. We discuss high-mass star formation scenarios in a context based on IRDC G028.23-00.19, a study case believed to represent the initial fragmentation of molecular clouds that will form high-mass stars.« less

An SSM/I radiometer simulator for studies of microwave emission from soil. [Special Sensor Microwave/Imager

NASA Technical Reports Server (NTRS)

Galantowicz, J. F.; England, A. W.

1992-01-01

A ground-based simulator of the defense meterological satellite program special sensor microwave/imager (DMSP SSM/I) is described, and its integration with micrometeorological instrumentation for an investigation of microwave emission from moist and frozen soils is discussed. The simulator consists of three single polarization radiometers which are capable of both Dicke radiometer and total power radiometer modes of operation. The radiometers are designed for untended operation through a local computer and a daily telephone link to a laboratory. The functional characteristics of the radiometers are described, together with their field deployment configuration and an example of performance parameters.

Radiometric observations of atmospheric attenuation at 20.6 and 31.65 GHz: The Wave Propagation Laboratory data base

NASA Technical Reports Server (NTRS)

Jacobson, Mark D.; Snider, J. B.; Westwater, E. R.

1993-01-01

The National Oceanic and Atmospheric Administration (NOAA) Wave Propagation Laboratory (WPL) presently operates five dual-channel microwave radiometers, one triple-channel microwave radiometer, and one six-channel microwave radiometer. The dual-channel radiometers operate at frequencies of 20.6 or 23.87 GHz and 31.4 or 31.65 GHz. The triple-channel radiometer operates at 20.6, 31.65, and 90.0 GHz. The six-channel radiometer operates at frequencies of 20.6, 31.65, 52.85, 53.85, 55.45, and 58.8 GHz. Recent brightness temperature measurements and attenuation values from some of the above radiometers are presented. These radiometric measurements, taken in different locations throughout the world, have given WPL a diverse set of measurements under a variety of atmospheric conditions. We propose to do a more complete attenuation analysis on these measurements in the future. In addition, a new spinning reflector was installed recently for the dual-channel radiometer at the Platteville, Colorado site. This reflector will extend our measurement capabilities during precipating conditions. Locating the three-channel and portable dual-channel radiometers at or near Greeley, Colorado to support the Advanced Communications Technology Satellite (ACTS) program is discussed.

The Age of Planet Host κ Andromedae Based on Interferometric Observations

NASA Astrophysics Data System (ADS)

Jones, Jeremy; White, Russel J.; Quinn, Samuel N.; Baines, Ellyn K.; Boyajian, Tabetha S.; Ireland, Michael; CHARA Team

2016-01-01

We present CHARA Array interferometric observations, obtained with the PAVO beam combiner in the optical (~750 nm), of κ Andromedae. This nearby (51.6 pc) B9/A0V star hosts a directly-imaged low mass companion. Observations made at multiple orientations show the star to be oblate (~15%), consistent with its large projected rotational velocity (vsini = 161.6 ± 22.2 km s-1). The interferometric observations, combined with photometry and the vsini are used to constrain an oblate star model of κ And, enabling us to determine its fundamental properties (e.g., average radius, bolometric luminosity, and equatorial velocity). These stellar properties are compared to the predictions of MESA evolution models to determine an age and mass for the star. The best fit model favors a young age for the system (< 100 Myr), which implies that κ And b has a mass around the limit separating planets and brown dwarfs.

KSC-2012-1378

NASA Image and Video Library

2012-02-16

VANDENBERG AIR FORCE BASE, Calif. -- Technicians watch closely as NASA's NuSTAR spacecraft is Under the watchful eyes of technicians, NASA's NuSTAR spacecraft is lifted inside Orbital Sciences' processing facility at Vandenberg Air Force Base, Calif. The spacecraft will be rotated to horizontal for joining with the Pegasus XL rocket. The Orbital Sciences Pegasus will launch NASA's Nuclear Spectroscopic Telescope Array NuSTAR into space. After the rocket and spacecraft are processed at Vandenberg, they will be flown on Orbital's L-1011 carrier aircraft to the Ronald Reagan Ballistic Missile Defense Test Site at the Pacific Ocean’s Kwajalein Atoll for launch. The high-energy x-ray telescope will conduct a census for black holes, map radioactive material in young supernovae remnants, and study the origins of cosmic rays and the extreme physics around collapsed stars. For more information, visit science.nasa.gov/missions/nustar/. Photo credit: NASA/Randy Beaudoin, VAFB

Ultra Stable Microwave Radiometers for Future Sea Surface Salinity Missions

NASA Technical Reports Server (NTRS)

Wilson, William J.; Tanner, Alan B.; Pellerano, Fernando A.; Horgan, Kevin A.

2005-01-01

The NASA Earth Science System Pathfinder (ESSP) mission Aquarius will measure global sea surface salinity with 100-km spatial resolution every 8 days with an average monthly salinity accuracy of 0.2 psu (parts per thousand). This requires an L-band low-noise radiometer with the long-term calibration stability of less than 0.1 K over 8 days. This three-year research program on ultra stable radiometers has addressed the radiometer requirements and configuration necessary to achieve this objective for Aquarius and future ocean salinity missions. The system configuration and component performance have been evaluated with radiometer testbeds at both JPL and GSFC. The research has addressed several areas including component characterization as a function of temperature, a procedure for the measurement and correction for radiometer system non-linearity, noise diode calibration versus temperature, low noise amplifier performance over voltage, and temperature control requirements to achieve the required stability. A breadboard radiometer, utilizing microstrip-based technologies, has been built to demonstrate this long-term stability. This report also presents the results of the radiometer test program, a detailed radiometer noise model, and details of the operational switching sequence optimization that can be used to achieve the low noise and stability requirements. Many of the results of this research have been incorporated into the Aquarius radiometer design and will allow this instrument to achieve its goals.

Progress and prospects of silicon-based design for optical phased array

NASA Astrophysics Data System (ADS)

Hu, Weiwei; Peng, Chao; Chang-Hasnain, Connie

2016-03-01

The high-speed, high-efficient, compact phase modulator array is indispensable in the Optical-phased array (OPA) which has been considered as a promising technology for realizing flexible and efficient beam steering. In our research, two methods are presented to utilize high-contrast grating (HCG) as high-efficient phase modulator. One is that HCG possesses high-Q resonances that origins from the cancellation of leaky waves. As a result, sharp resonance peaks appear on the reflection spectrum thus HCGs can be utilized as efficient phase shifters. Another is that low-Q mode HCG is utilized as ultra-lightweight mirror. With MEMS technology, small HCG displacement (~50 nm) leads to large phase change (~1.7π). Effective beam steering is achieved in Connie Chang-Hasnian's group. On the other hand, we theoretically and experimentally investigate the system design for silicon-based optical phased array, including the star coupler, phased array, emission elements and far-field patterns. Further, the non-uniform optical phased array is presented.

Finite element dynamic analysis on CDC STAR-100 computer

NASA Technical Reports Server (NTRS)

Noor, A. K.; Lambiotte, J. J., Jr.

1978-01-01

Computational algorithms are presented for the finite element dynamic analysis of structures on the CDC STAR-100 computer. The spatial behavior is described using higher-order finite elements. The temporal behavior is approximated by using either the central difference explicit scheme or Newmark's implicit scheme. In each case the analysis is broken up into a number of basic macro-operations. Discussion is focused on the organization of the computation and the mode of storage of different arrays to take advantage of the STAR pipeline capability. The potential of the proposed algorithms is discussed and CPU times are given for performing the different macro-operations for a shell modeled by higher order composite shallow shell elements having 80 degrees of freedom.

High-resolution Interferometric Observations of Nova RS Ophiuchi and a Proposed Unification Model for Persistent Dust Creation in Recurrent Novae

NASA Astrophysics Data System (ADS)

Barry, R. K.; Danchi, W. C.

2008-12-01

We review observations of nova RS Ophiuchi using long-baseline near-infrared and mid-infrared interferometry at three observatories: the Keck Interferometer in the Nulling mode (KIN), the Palomar Testbed Interferometer (PTI), and the Infrared and Optical Telescope Array (IOTA). We discuss these observations in the context of a unifying model of the system that includes an increase in density in the plane of the orbit of the two stars created by a spiral shock wave caused by the motion of the stars through the cool wind of the red giant star. We discuss how recent observations using the Spitzer Space Telescope and the VLTI support this proposed model.

Blast from the Past Gives Clues About Early Universe

NASA Astrophysics Data System (ADS)

2009-10-01

Astronomers using the National Science Foundation's Very Large Array (VLA) radio telescope have gained tantalizing insights into the nature of the most distant object ever observed in the Universe -- a gigantic stellar explosion known as a Gamma Ray Burst (GRB). The explosion was detected on April 23 by NASA's Swift satellite, and scientists soon realized that it was more than 13 billion light-years from Earth. It represents an event that occurred 630 million years after the Big Bang, when the Universe was only four percent of its current age of 13.7 billion years. This explosion provides an unprecedented look at an era when the Universe was very young and also was undergoing drastic changes. The primal cosmic darkness was being pierced by the light of the first stars and the first galaxies were beginning to form. The star that exploded in this event was a member of one of these earliest generations of stars," said Dale Frail of the National Radio Astronomy Observatory. Astronomers turned telescopes from around the world to study the blast, dubbed GRB 090423. The VLA first looked for the object the day after the discovery, detected the first radio waves from the blast a week later, then recorded changes in the object until it faded from view more than two months later. "It's important to study these explosions with many kinds of telescopes. Our research team combined data from the VLA with data from X-ray and infrared telescopes to piece together some of the physical conditions of the blast," said Derek Fox of Pennsylvania State University. "The result is a unique look into the very early Universe that we couldn't have gotten any other way," he added. The scientists concluded that the explosion was more energetic than most GRBs, was a nearly-spherical blast, and that it expanded into a tenuous and relatively uniform gaseous medium surrounding the star. Astronomers suspect that the very first stars in the Universe were very different -- brighter, hotter, and more massive -- from those that formed later. They hope to find evidence for these giants by observing objects as distant as GRB 090423 or more distant. "The best way to distinguish these distant, early-generation stars is by studying their explosive deaths, as supernovae or Gamma Ray Bursts," said Poonam Chandra, of the Royal Military College of Canada, and leader of the research team. While the data on GRB 090423 don't indicate that it resulted from the death of such a monster star, new astronomical tools are coming that may reveal them. "The Atacama Large Millimeter/submillimeter Array (ALMA), will allow us to pick out these very-distant GRBs more easily so we can target them for intense followup observations. The Expanded Very Large Array, with much greater sensitivity than the current VLA, will let us follow these blasts much longer and learn much more about their energies and environments. We'll be able to look back even further in time," Frail said. Both ALMA and the EVLA are scheduled for completion in 2012. Chandra, Frail and Fox worked with Shrinivas Kulkarni of Caltech, Edo Berger of Harvard University, S. Bradley Cenko of the University of California at Berkeley, Douglas C.-J. Bock of the Combined Array for Research in Millimeter-wave Astronomy in California, and Fiona Harrison and Mansi Kasliwal of Caltech. The scientists described their research in a paper submitted to the Astrophysical Journal Letters.

Consolidated RXTE Observing Grants on Observation of Neutron Stars and Black Holes in Binaries

NASA Technical Reports Server (NTRS)

Prince, Thomas A.; Vaughan, Brian A.

1998-01-01

This final report is a study of neutron stars and black holes in binaries. The activities focused on observation made with the Rossi X-ray Timing Explorer. The following areas were covered: long term observations of accreting binary pulsars with the All-Sky Monitor (ASM); observations of Centaurus X-3 with the Proportional Counter Array (PCA) and the High-Energy X-ray Timing Experiment (HEXTE); observations of accreting pulsars with the PCA and HEXTE; studies of quasi-periodic oscillations (QPO); and investigations of accreting black-hole candidates.

Photometric and Spectroscopic Analysis for the Determination of Physical Parameters of an Eclipsing Binary Star System

NASA Astrophysics Data System (ADS)

Reid, Piper

2013-01-01

A binary star system is a pair of stars that are bound together by gravity. Most of the stars that we see in the night sky are members of multiple star systems. A system of stars where one star passes in front of the other (as observed from Earth) on a periodic basis is called an eclipsing binary. Eclipsing binaries can have very short rotational periods and in all cases these pairs of stars are so far away that they can only be resolved from Earth as a single point of light. The interaction of the two stars serves to produce physical phenomena that can be observed and used to study stellar properties. By careful data collection and analysis is it possible for an amateur astronomer using commercial, low cost equipment (including a home built spectroscope) to gather photometric (brightness versus time) and spectroscopic (brightness versus wavelength) data, analyze the data, and calculate the physical properties of a binary star system? Using a CCD camera, tracking mount and telescope photometric data of BB Pegasi was collected and a light curve produced. 57 Cygni was also studied using a spectroscope, tracking mount and telescope to prove that Doppler shift of Hydrogen Balmer absorption lines can be used to determine radial velocity. The orbital period, orbital velocity, radius of each star, separation of the two stars and mass of each star was calculated for the eclipsing binary BB Pegasi using photometric and spectroscopic data and Kepler’s 3rd Law. These data were then compared to published data. By careful use of consumer grade astronomical equipment it is possible for an amateur astronomer to determine an array of physical parameters of a distant binary star system from a suburban setting.

Radiometer Calibration and Characterization (RCC) User's Manual: Windows Version 4.0

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

Andreas, Afshin M.; Wilcox, Stephen M.

2016-02-29

The Radiometer Calibration and Characterization (RCC) software is a data acquisition and data archival system for performing Broadband Outdoor Radiometer Calibrations (BORCAL). RCC provides a unique method of calibrating broadband atmospheric longwave and solar shortwave radiometers using techniques that reduce measurement uncertainty and better characterize a radiometer's response profile. The RCC software automatically monitors and controls many of the components that contribute to uncertainty in an instrument's responsivity. This is a user's manual and guide to the RCC software.

Soil Moisture Active Passive (SMAP) L-Band Microwave Radiometer Post-Launch Calibration

NASA Technical Reports Server (NTRS)

Peng, Jinzheng; Piepmeier, Jeffrey R.; Misra, Sidharth; Dinnat, Emmanuel P.; Hudson, Derek; Le Vine, David M.; De Amici, Giovanni; Mohammed, Priscilla N.; Yueh, Simon H.; Meissner, Thomas

2016-01-01

The SMAP microwave radiometer is a fully-polarimetric L-band radiometer flown on the SMAP satellite in a 6 AM/ 6 PM sun-synchronous orbit at 685 km altitude. Since April, 2015, the radiometer is under calibration and validation to assess the quality of the radiometer L1B data product. Calibration methods including the SMAP L1B TA2TB (from Antenna Temperature (TA) to the Earth's surface Brightness Temperature (TB)) algorithm and TA forward models are outlined, and validation approaches to calibration stability/quality are described in this paper including future work. Results show that the current radiometer L1B data satisfies its requirements.

Soil Moisture ActivePassive (SMAP) L-Band Microwave Radiometer Post-Launch Calibration

NASA Technical Reports Server (NTRS)

Peng, Jinzheng; Piepmeier, Jeffrey R.; Misra, Sidharth; Dinnat, Emmanuel P.; Hudson, Derek; Le Vine, David M.; De Amici, Giovanni; Mohammed, Priscilla N.; Yueh, Simon H.; Meissner, Thomas

2016-01-01

The SMAP microwave radiometer is a fully-polarimetric L-band radiometer flown on the SMAP satellite in a 6 AM/ 6 PM sun-synchronous orbit at 685 km altitude. Since April, 2015, the radiometer is under calibration and validation to assess the quality of the radiometer L1B data product. Calibration methods including the SMAP L1B TA2TB (from Antenna Temperature (TA) to the Earth’s surface Brightness Temperature (TB)) algorithm and TA forward models are outlined, and validation approaches to calibration stability/quality are described in this paper including future work. Results show that the current radiometer L1B data satisfies its requirements.

Stellar Diameters and Temperatures. III. Main-sequence A, F, G, and K Stars: Additional High-precision Measurements and Empirical Relations

NASA Astrophysics Data System (ADS)

Boyajian, Tabetha S.; von Braun, Kaspar; van Belle, Gerard; Farrington, Chris; Schaefer, Gail; Jones, Jeremy; White, Russel; McAlister, Harold A.; ten Brummelaar, Theo A.; Ridgway, Stephen; Gies, Douglas; Sturmann, Laszlo; Sturmann, Judit; Turner, Nils H.; Goldfinger, P. J.; Vargas, Norm

2013-07-01

Based on CHARA Array measurements, we present the angular diameters of 23 nearby, main-sequence stars, ranging from spectral types A7 to K0, 5 of which are exoplanet host stars. We derive linear radii, effective temperatures, and absolute luminosities of the stars using Hipparcos parallaxes and measured bolometric fluxes. The new data are combined with previously published values to create an Angular Diameter Anthology of measured angular diameters to main-sequence stars (luminosity classes V and IV). This compilation consists of 125 stars with diameter uncertainties of less than 5%, ranging in spectral types from A to M. The large quantity of empirical data is used to derive color-temperature relations to an assortment of color indices in the Johnson (BVR J I J JHK), Cousins (R C I C), Kron (R K I K), Sloan (griz), and WISE (W 3 W 4) photometric systems. These relations have an average standard deviation of ~3% and are valid for stars with spectral types A0-M4. To derive even more accurate relations for Sun-like stars, we also determined these temperature relations omitting early-type stars (T eff > 6750 K) that may have biased luminosity estimates because of rapid rotation; for this subset the dispersion is only ~2.5%. We find effective temperatures in agreement within a couple of percent for the interferometrically characterized sample of main-sequence stars compared to those derived via the infrared flux method and spectroscopic analysis.

Radiometer calibration methods and resulting irradiance differences: Radiometer calibration methods and resulting irradiance differences

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

Habte, Aron; Sengupta, Manajit; Andreas, Afshin

Accurate solar radiation measured by radiometers depends on instrument performance specifications, installation method, calibration procedure, measurement conditions, maintenance practices, location, and environmental conditions. This study addresses the effect of different calibration methodologies and resulting differences provided by radiometric calibration service providers such as the National Renewable Energy Laboratory (NREL) and manufacturers of radiometers. Some of these methods calibrate radiometers indoors and some outdoors. To establish or understand the differences in calibration methodologies, we processed and analyzed field-measured data from radiometers deployed for 10 months at NREL's Solar Radiation Research Laboratory. These different methods of calibration resulted in a difference ofmore » +/-1% to +/-2% in solar irradiance measurements. Analyzing these differences will ultimately assist in determining the uncertainties of the field radiometer data and will help develop a consensus on a standard for calibration. Further advancing procedures for precisely calibrating radiometers to world reference standards that reduce measurement uncertainties will help the accurate prediction of the output of planned solar conversion projects and improve the bankability of financing solar projects.« less

Thermodynamic and liquid profiling during the 2010 Winter Olympics

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

Ware, R.; Cimini, D.; Campos, E.

2013-10-01

Tropospheric observations by a microwave profiling radiometer and six-hour radiosondes were obtained during the Alpine Venue of the 2010 Winter Olympic Games at Whistler, British Columbia, by Environment Canada. The radiometer provided continuous temperature, humidity and liquid (water) profiles during all weather conditions including rain, sleet and snow. Gridded analysis was provided by the U.S. National Oceanic and Atmospheric Administration. We compare more than two weeks of radiometer neural network and radiosonde temperature and humidity soundings including clear and precipitating conditions. Corresponding radiometer liquid and radiosonde wind soundings are shown. Close correlation is evident between radiometer and radiosonde temperature andmore » humidity profiles up to 10 km height and among southwest winds, liquid water and upper level thermodynamics, consistent with up-valley advection and condensation of moist maritime air. We compare brightness temperatures observed by the radiometer and forward-modeled from radiosonde and gridded analysis. Radiosonde-equivalent observation accuracy is demonstrated for radiometer neural network temperature and humidity retrievals up to 800 m height and for variational retrievals that combine radiometer and gridded analysis up to 10 km height« less

Comparing the Accuracy of AMSRE, AMSR2, SSMI and SSMIS Satellite Radiometer Ice Concentration Products with One-Meter Resolution Visible Imagery in the Arctic

NASA Astrophysics Data System (ADS)

Peterson, E. R.; Stanton, T. P.

2016-12-01

Determining ice concentration in the Arctic is necessary to track significant changes in sea ice edge extent. Sea ice concentrations are also needed to interpret data collected by in-situ instruments like buoys, as the amount of ice versus water in a given area determines local solar heating. Ice concentration products are now routinely derived from satellite radiometers including the Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR-E), the Advanced Microwave Scanning Radiometer 2 (AMSR2), the Special Sensor Microwave Imager (SSMI), and the Special Sensor Microwave Imager/Sounder (SSMIS). While these radiometers are viewed as reliable to monitor long-term changes in sea ice extent, their accuracy should be analyzed, and compared to determine which radiometer performs best over smaller features such as melt ponds, and how seasonal conditions affect accuracy. Knowledge of the accuracy of radiometers at high resolution can help future researchers determine which radiometer to use, and be aware of radiometer shortcomings in different ice conditions. This will be especially useful when interpreting data from in-situ instruments which deal with small scale measurements. In order to compare these passive microwave radiometers, selected high spatial resolution one-meter resolution Medea images, archived at the Unites States Geological Survey, are used for ground truth comparison. Sea ice concentrations are derived from these images in an interactive process, although estimates are not perfect ground truth due to exposure of images, shadowing and cloud cover. 68 images are retrieved from the USGS website and compared with 9 useable, collocated SSMI, 33 SSMIS, 36 AMSRE, and 14 AMSR2 ice concentrations in the Arctic Ocean. We analyze and compare the accuracy of radiometer instrumentation in differing ice conditions.

Spectral radiance source based on supercontinuum laser and wavelength tunable bandpass filter: the spectrally tunable absolute irradiance and radiance source.

PubMed

Levick, Andrew P; Greenwell, Claire L; Ireland, Jane; Woolliams, Emma R; Goodman, Teresa M; Bialek, Agnieszka; Fox, Nigel P

2014-06-01

A new spectrally tunable source for calibration of radiometric detectors in radiance, irradiance, or power mode has been developed and characterized. It is termed the spectrally tunable absolute irradiance and radiance source (STAIRS). It consists of a supercontinuum laser, wavelength tunable bandpass filter, power stabilization feedback control scheme, and output coupling optics. It has the advantages of relative portability and a collimated beam (low étendue), and is an alternative to conventional sources such as tungsten lamps, blackbodies, or tunable lasers. The supercontinuum laser is a commercial Fianium SC400-6-02, which has a wavelength range between 400 and 2500 nm and a total power of 6 W. The wavelength tunable bandpass filter, a PhotonEtc laser line tunable filter (LLTF), is tunable between 400 and 1000 nm and has a bandwidth of 1 or 2 nm depending on the wavelength selected. The collimated laser beam from the LLTF filter is converted to an appropriate spatial and angular distribution for the application considered (i.e., for radiance, irradiance, or power mode calibration of a radiometric sensor) with the output coupling optics, for example, an integrating sphere, and the spectral radiance/irradiance/power of the source is measured using a calibration optical sensor. A power stabilization feedback control scheme has been incorporated that stabilizes the source to better than 0.01% for averaging times longer than 100 s. The out-of-band transmission of the LLTF filter is estimated to be < -65 dB (0.00003%), and is sufficiently low for many end-user applications, for example the spectral radiance calibration of earth observation imaging radiometers and the stray light characterization of array spectrometers (the end-user optical sensor). We have made initial measurements of two end-user instruments with the STAIRS source, an array spectrometer and ocean color radiometer.

Sizing up the stars

NASA Astrophysics Data System (ADS)

Boyajian, Tabetha S.

For the main part of this dissertation, I have executed a survey of nearby, main sequence A, F, and G-type stars with the CHARA Array, successfully measuring the angular diameters of forty-four stars to better than 4% accuracy. The results of these observations also yield empirical determinations of stellar linear radii and effective temperatures for the stars observed. In addition, these CHARA-determined temperatures, radii, and luminosities are fit to Yonsei-Yale isochrones to constrain the masses and ages of the stars. These quantities are compared to the results found in Allende Prieto & Lambert (1999), Holmberg et al. (2007), and Takeda (2007), who indirectly determine these same properties by fitting models to observed photometry. I find that for most cases, the models underestimate the radius of the star by ~ 12%, while in turn they overestimate the effective temperature by ~ 1.5-4%, when compared to my directly measured values, with no apparent correlation to the star's metallicity or color index. These overestimated temperatures and underestimated radii in these works appear to cause an additional offset in the star's surface gravity measurements, which consequently yield higher masses and younger ages, in particular for stars with masses greater than ~ 1.3 [Special characters omitted.] . Alternatively, these quantities I measure are also compared to direct measurements from a large sample of eclipsing binary stars in Andersen (1991), and excellent agreement is seen within both data sets. Finally, a multi-parameter solution is found to fit color-temperature-metallicity values of the stars in this sample to provide a new calibration of the effective temperature scale for these types of stars. Published work in the field of stellar interferometry and optical spectroscopy of early-type stars are presented in Appendix D and E, respectively. INDEX WORDS: Interferometry, Infrared, Stellar Astronomy, Fundamental Properties, Effective Temperatures, Stellar Radii

Exoplanet-induced Radio Emission from M Dwarfs

NASA Astrophysics Data System (ADS)

Turnpenney, Sam; Nichols, Jonathan D.; Wynn, Graham A.; Burleigh, Matthew R.

2018-02-01

We consider the magnetic interaction of exoplanets orbiting M dwarfs, calculating the expected Poynting flux carried upstream along Alfvén wings to the central star. A region of emission analogous to the Io footprint observed in Jupiter’s aurora is produced, and we calculate the radio flux density generated near the surface of the star via the electron-cyclotron maser instability. We apply the model to produce individual case studies for the TRAPPIST-1, Proxima Centauri, and dwarf NGTS-1 systems. We predict steady-state flux densities of up to ∼10 μJy and sporadic bursts of emission of up to ∼1 mJy from each case study, suggesting these systems may be detectable with the Very Large Array and the Giant Metrewave Radio Telescope, and perhaps the Square Kilometre Array in the future. Finally, we present a survey of 85 exoplanets orbiting M dwarfs, identifying 11 such objects capable of generating radio emission above 10 μJy.

Upgrades to MINERVA control software

NASA Astrophysics Data System (ADS)

Wilson, Maurice; Eastman, Jason D.

2017-01-01

The MINiature Exoplanet Radial Velocity Array (MINERVA) is an array of four robotic telescopes located on Mt. Hopkins in Arizona that will find and characterize rocky planets around our nearest stars. We discuss the latest upgrades to the MINERVA robotic control software. Previously, our robotic control software was only capable of taking radial velocities or photometry for the entire night, but not both. We have recently increased the speed and ease of transitioning between photometry and radial velocity (RV) observations. We can now arbitrarily assign a subset of the telescopes to either photometric or spectroscopic observations. This capability enables us to monitor stellar activity while measuring the star’s RV, gather photometry on one star while continuing our RV survey of other targets and provide education and public outreach opportunities where others can observe with one or more telescopes while we continue using the remaining telescopes for research. This material is based upon work supported by the National Science Foundation Graduate Research Fellowship Program under Grant No. 1144152.

The First Year of Robotic Science with MINERVA

NASA Astrophysics Data System (ADS)

McCrady, Nate; Johnson, John A.; Wright, Jason; Wittenmyer, Robert; Eastman, Jason; Beatty, Thomas G.; Bottom, Michael; Johnson, Samson

2016-01-01

Detection of low-mass exoplanets orbiting Sun-like stars requires high cadence, long time-baseline observations that are impossible to obtain on shared large telescopes. MINERVA is a dedicated observatory for exoplanet detection that consists of four robotic 0.7-meter PlaneWave telescopes located at Whipple Observatory on Mt Hopkins, Arizona. First light science began in May 2015 with photometric monitoring of transit and microlensing events. The four telescopes can observe different targets, or provide simultaneous multi-color light curves of a single event. We will add a purpose-built, temperature-stabilized, high precision iodine cell spectrometer from Callaghan Innovation in 2016 to facilitate velocimetric search for low-mass exoplanets around nearby stars. The flexibility of the MINERVA array provides a natural avenue for educational and public outreach activities. One telescope in the array can break formation to observe targets from a queue or respond to remote operations from astronomy courses at a partner institution. MINERVA is a collaboration among Harvard U., Penn State U., U. Montana, and U. New South Wales.

Thermal analysis of radiometer containers for the 122m hoop column antenna concept

NASA Technical Reports Server (NTRS)

Dillon-Townes, L. A.

1986-01-01

A thermal analysis was conducted for the 122 Meter Hoop Column Antenna (HCA) Radiometer electronic package containers. The HCA radiometer containers were modeled using the computer aided graphics program, ANVIL 4000, and thermally simulated using two thermal programs, TRASYS and MITAS. The results of the analysis provided relationships between the absorptance-emittance ratio and the average surface temperature of the orbiting radiometer containers. These relationships can be used to specify the surface properties, absorptance and reflectance, of the radiometer containers. This is an initial effort in determining the passive thermal protection needs for the 122 m HCA radiometer containers. Several recommendations are provided which expand this effort so specific passive and active thermal protection systems can be defined and designed.

SONS: The JCMT legacy survey of debris discs in the submillimetre

NASA Astrophysics Data System (ADS)

Holland, Wayne S.; Matthews, Brenda C.; Kennedy, Grant M.; Greaves, Jane S.; Wyatt, Mark C.; Booth, Mark; Bastien, Pierre; Bryden, Geoff; Butner, Harold; Chen, Christine H.; Chrysostomou, Antonio; Davies, Claire L.; Dent, William R. F.; Di Francesco, James; Duchêne, Gaspard; Gibb, Andy G.; Friberg, Per; Ivison, Rob J.; Jenness, Tim; Kavelaars, JJ; Lawler, Samantha; Lestrade, Jean-François; Marshall, Jonathan P.; Moro-Martin, Amaya; Panić, Olja; Phillips, Neil; Serjeant, Stephen; Schieven, Gerald H.; Sibthorpe, Bruce; Vican, Laura; Ward-Thompson, Derek; van der Werf, Paul; White, Glenn J.; Wilner, David; Zuckerman, Ben

2017-09-01

Debris discs are evidence of the ongoing destructive collisions between planetesimals, and their presence around stars also suggests that planets exist in these systems. In this paper, we present submillimetre images of the thermal emission from debris discs that formed the SCUBA-2 Observations of Nearby Stars (SONS) survey, one of seven legacy surveys undertaken on the James Clerk Maxwell Telescope between 2012 and 2015. The overall results of the survey are presented in the form of 850 μm (and 450 μm, where possible) images and fluxes for the observed fields. Excess thermal emission, over that expected from the stellar photosphere, is detected around 49 stars out of the 100 observed fields. The discs are characterized in terms of their flux density, size (radial distribution of the dust) and derived dust properties from their spectral energy distributions. The results show discs over a range of sizes, typically 1-10 times the diameter of the Edgeworth-Kuiper Belt in our Solar system. The mass of a disc, for particles up to a few millimetres in size, is uniquely obtainable with submillimetre observations and this quantity is presented as a function of the host stars' age, showing a tentative decline in mass with age. Having doubled the number of imaged discs at submillimetre wavelengths from ground-based, single-dish telescope observations, one of the key legacy products from the SONS survey is to provide a comprehensive target list to observe at high angular resolution using submillimetre/millimetre interferometers (e.g. Atacama Large Millimeter Array, Smithsonian Millimeter Array).

The most distant, luminous, dusty star-forming galaxies: redshifts from NOEMA and ALMA spectral scans

NASA Astrophysics Data System (ADS)

Fudamoto, Y.; Ivison, R. J.; Oteo, I.; Krips, M.; Zhang, Z.-Y.; Weiss, A.; Dannerbauer, H.; Omont, A.; Chapman, S. C.; Christensen, L.; Arumugam, V.; Bertoldi, F.; Bremer, M.; Clements, D. L.; Dunne, L.; Eales, S. A.; Greenslade, J.; Maddox, S.; Martinez-Navajas, P.; Michalowski, M.; Pérez-Fournon, I.; Riechers, D.; Simpson, J. M.; Stalder, B.; Valiante, E.; van der Werf, P.

2017-12-01

We present 1.3- and/or 3-mm continuum images and 3-mm spectral scans, obtained using Northern Extended Millimeter Array (NOEMA) and Atacama Large Millimeter Array (ALMA), of 21 distant, dusty, star-forming galaxies. Our sample is a subset of the galaxies selected by Ivison et al. on the basis of their extremely red far-infrared (far-IR) colours and low Herschel flux densities; most are thus expected to be unlensed, extraordinarily luminous starbursts at z ≳ 4, modulo the considerable cross-section to gravitational lensing implied by their redshift. We observed 17 of these galaxies with NOEMA and four with ALMA, scanning through the 3-mm atmospheric window. We have obtained secure redshifts for seven galaxies via detection of multiple CO lines, one of them a lensed system at z = 6.027 (two others are also found to be lensed); a single emission line was detected in another four galaxies, one of which has been shown elsewhere to lie at z = 4.002. Where we find no spectroscopic redshifts, the galaxies are generally less luminous by 0.3-0.4 dex, which goes some way to explaining our failure to detect line emission. We show that this sample contains the most luminous known star-forming galaxies. Due to their extreme star-formation activity, these galaxies will consume their molecular gas in ≲ 100 Myr, despite their high molecular gas masses, and are therefore plausible progenitors of the massive, 'red-and-dead' elliptical galaxies at z ≈ 3.

Hierarchical fragmentation and differential star formation in the Galactic `Snake': infrared dark cloud G11.11-0.12

NASA Astrophysics Data System (ADS)

Wang, Ke; Zhang, Qizhou; Testi, Leonardo; van der Tak, Floris; Wu, Yuefang; Zhang, Huawei; Pillai, Thushara; Wyrowski, Friedrich; Carey, Sean; Ragan, Sarah E.; Henning, Thomas

2014-04-01

We present Submillimeter Array (SMA) λ = 0.88 and 1.3 mm broad-band observations, and Very Large Array (VLA) observations in NH3 (J, K) = (1,1) up to (5,5), H2O and CH3OH maser lines towards the two most massive molecular clumps in infrared dark cloud (IRDC) G11.11-0.12. Sensitive high-resolution images reveal hierarchical fragmentation in dense molecular gas from the ˜1 pc clump scale down to ˜0.01 pc condensation scale. At each scale, the mass of the fragments is orders of magnitude larger than the Jeans mass. This is common to all four IRDC clumps we studied, suggesting that turbulence plays an important role in the early stages of clustered star formation. Masers, shock heated NH3 gas, and outflows indicate intense ongoing star formation in some cores while no such signatures are found in others. Furthermore, chemical differentiation may reflect the difference in evolutionary stages among these star formation seeds. We find NH3 ortho/para ratios of 1.1 ± 0.4, 2.0 ± 0.4, and 3.0 ± 0.7 associated with three outflows, and the ratio tends to increase along the outflows downstream. Our combined SMA and VLA observations of several IRDC clumps present the most in-depth view so far of the early stages prior to the hot core phase, revealing snapshots of physical and chemical properties at various stages along an apparent evolutionary sequence.

Drivers of Turbulence in the Neutral Interstellar Medium of Dwarf Galaxies

NASA Astrophysics Data System (ADS)

Stilp, Adrienne M.

The cause of HI velocity dispersions in the interstellar medium (ISM) of galaxies is often attributed to star formation, but recent evidence has shown these two quantities are not connected in regions of low star formation. This lack of connection is most apparent in dwarf galaxies and the outer disks of spiral galaxies. However, unique data sets have recently been collected that can help address this discrepancy. The ACS Nearby Survey Treasury Project (ANGST) has measured time-resolved star formation histories (SFHs) in ˜ 70 nearby galaxies. The followup Very Large Array-ANGST survey (VLA-ANGST) provides complementary HI observations of a subset of ANGST galaxies. In this thesis, I explore the connection between star formation and HI kinematics in a number of nearby dwarf galaxies. I first present the Very Large Array-ACS Nearby Galaxy Survey Treasury Project (ANGST). VLA-ANGST was designed to provide high spatial and velocity resolution observations of the HI component of the interstellar medium (ISM) in ANGST galaxies. I describe the data calibration and imaging procedures, and then present the publicly-available data products. The observations from this survey and from The HI Nearby Galaxy Survey (THINGS) comprise the majority of data in my thesis. Using VLA-ANGST and THINGS data, I present a method to measure the average HI kinematics in a number of nearby dwarf galaxies by co-adding individual line-of-sight profiles. These "superprofiles" are composed of a central narrow peak (˜ 6-10 km s-1) with higher velocity wings to either side. When scaled to the same half-width half-maximum, the shapes of the superprofiles are very similar. I interpret the central peak as representative of the average turbulent motion; the wings are then due to HI moving faster than expected compared to the average kinematics. I then compare the superprofile parameters to physical properties such as mass surface density and star formation intensity. The average velocity dispersion correlate most strongly with HI surface density, and do not show correlations with star formation intensity unless higher mass galaxies were included. The properties of the wings are more connected with star formation. By applying energy arguments, I determine that star formation can provide enough energy to drive the HI kinematics over ˜ 10 Myr timescales, while a gravitational instability cannot. I then extend this analysis to spatially-resolved scales in these galaxies, and generated superprofiles in regions determined by radius or by star formation intensity. These superprofiles provide a more direct comparison between H I kinematics and local ISM properties compared to the analysis on global scales. The spatially-resolved superprofiles indicate that star formation does not uniquely determine the HI velocity dispersion, but it does appear to provide a lower floor below which velocity dispersions cannot fall. I also find that the coupling efficiency between star formation and HI kinematics decreases with increasing star formation surface density, which may indicate that star formation energy couples more consistently to other phases of the ISM. I finally explore the timescale over which HI responds to star formation using a combination of VLA-ANGST, THINGS, and ANGST data. Using time-resolved SFHs from ANGST, I measure the average star formation rate as a function of time and compared it to present-day HI kinematics. I find that the HI kinematics are most strongly correlated with star formation that occurred ˜ 30 -- 40 Myr ago, which supports the idea that supernova explosions are one driver of HI kinematics even in low star formation systems.

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.

Star Formation in Nearby Galaxies

NASA Astrophysics Data System (ADS)

O'Connell, Robert

2009-07-01

Star formation is a fundamental astrophysical process; it controls phenomena ranging from the evolution of galaxies and nucleosynthesis to the origins of planetary systems and abodes for life. The WFC3, optimized at both UV and IR wavelengths and equipped with an extensive array of narrow-band filters, brings unique capabilities to this area of study. The WFC3 Scientific Oversight Committee {SOC} proposes an integrated program on star formation in the nearby universe which will fully exploit these new abilities. Our targets range from the well-resolved R136 in 30 Dor in the LMC {the nearest super star cluster} and M82 {the nearest starbursting galaxy} to about half a dozen other nearby galaxies that sample a wide range of star-formation rates and environments. Our program consists of broad-band multiwavelength imaging over the entire range from the UV to the near-IR, aimed at studying the ages and metallicities of stellar populations, revealing young stars that are still hidden by dust at optical wavelengths, and showing the integrated properties of star clusters. Narrow-band imaging of the same environments will allow us to measure star-formation rates, gas pressure, chemical abundances, extinction, and shock morphologies. The primary scientific issues to be addressed are: {1} What triggers star formation? {2} How do the properties of star-forming regions vary among different types of galaxies and environments of different gas densities and compositions? {3} How do these different environments affect the history of star formation? {4} Is the stellar initial mass function universal or determined by local conditions?

Light from Red-Hot Planet

NASA Technical Reports Server (NTRS)

2009-01-01

This figure charts 30 hours of observations taken by NASA's Spitzer Space Telescope of a strongly irradiated exoplanet (an planet orbiting a star beyond our own). Spitzer measured changes in the planet's heat, or infrared light.

The lower graph shows precise measurements of infrared light with a wavelength of 8 microns coming from the HD 80606 stellar system. The system consists of a sun-like star and a planetary companion on an extremely eccentric, comet-like orbit. The geometry of the planet-star encounter is shown in the upper part of the figure.

As the planet swung through its closest approach to the star, the Spitzer observations indicated that it experienced very rapid heating (as shown by the red curve). Just before close approach, the planet was eclipsed by the star as seen from Earth, allowing astronomers to determine the amount of energy coming from the planet in comparison to the amount coming from the star.

The observations were made in Nov. of 2007, using Spitzer's infrared array camera. They represent a significant first for astronomers, opening the door to studying changes in atmospheric conditions of planets far beyond our own solar system.

Circumstellar Disks Around Rapidly Rotating Be-type Stars

NASA Astrophysics Data System (ADS)

Touhami, Yamina

2012-01-01

Be stars are rapidly rotating B-type stars that eject large amounts of gaseous material into a circumstellar equatorial disk. The existence of this disk has been confirmed through the presence of several observational signatures such as the strong hydrogen emission lines, the IR flux excess, and the linear polarization detected from these systems. Here we report simultaneous near-IR interferometric and spectroscopic observations of circumstellar disks around Be stars obtained with the CHARA Array long baseline interferometer and the Mimir spectrograph at Lowell observatory. The goal of this project was to measure precise angular sizes and to characterize the fundamental geometrical and physical properties of the circumstellar disks. We were able to determine spatial extensions, inclinations, and position angles, as well as the gas density profile of the circumstellar disks using an elliptical Gaussian model and a physical thick disk model, and we show that the K-band interferometric angular sizes of the circumstellar disks are correlated with the H-alpha angular sizes. By combining the projected rotational velocity of the Be star with the disk inclination derived from interferometry, we provide estimates of the equatorial rotational velocities of these rapidly rotating Be stars.

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.

Ring Beholds a Delicate Flower

NASA Technical Reports Server (NTRS)

2005-01-01

NASA's Spitzer Space Telescope finds a delicate flower in the Ring Nebula, as shown in this image. The outer shell of this planetary nebula looks surprisingly similar to the delicate petals of a camellia blossom. A planetary nebula is a shell of material ejected from a dying star. Located about 2,000 light years from Earth in the constellation Lyra, the Ring Nebula is also known as Messier Object 57 and NGC 6720. It is one of the best examples of a planetary nebula and a favorite target of amateur astronomers.

The 'ring' is a thick cylinder of glowing gas and dust around the doomed star. As the star begins to run out of fuel, its core becomes smaller and hotter, boiling off its outer layers. The telescope's infrared array camera detected this material expelled from the withering star. Previous images of the Ring Nebula taken by visible-light telescopes usually showed just the inner glowing loop of gas around the star. The outer regions are especially prominent in this new image because Spitzer sees the infrared light from hydrogen molecules. The molecules emit infrared light because they have absorbed ultraviolet radiation from the star or have been heated by the wind from the star.

Download the QuickTime movie for the animated version of this Ring Nebula image.

Magnetic STAR technology for real-time localization and classification of unexploded ordnance and buried mines

NASA Astrophysics Data System (ADS)

Wiegert, R. F.

2009-05-01

A man-portable Magnetic Scalar Triangulation and Ranging ("MagSTAR") technology for Detection, Localization and Classification (DLC) of unexploded ordnance (UXO) has been developed by Naval Surface Warfare Center Panama City Division (NSWC PCD) with support from the Strategic Environmental Research and Development Program (SERDP). Proof of principle of the MagSTAR concept and its unique advantages for real-time, high-mobility magnetic sensing applications have been demonstrated by field tests of a prototype man-portable MagSTAR sensor. The prototype comprises: a) An array of fluxgate magnetometers configured as a multi-tensor gradiometer, b) A GPS-synchronized signal processing system. c) Unique STAR algorithms for point-by-point, standoff DLC of magnetic targets. This paper outlines details of: i) MagSTAR theory, ii) Design and construction of the prototype sensor, iii) Signal processing algorithms recently developed to improve the technology's target-discrimination accuracy, iv) Results of field tests of the portable gradiometer system against magnetic dipole targets. The results demonstrate that the MagSTAR technology is capable of very accurate, high-speed localization of magnetic targets at standoff distances of several meters. These advantages could readily be transitioned to a wide range of defense, security and sensing applications to provide faster and more effective DLC of UXO and buried mines.

Galaxy Evolution in the Radio Band: The Role of Star-forming Galaxies and Active Galactic Nuclei

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

Mancuso, C.; Prandoni, I.; Lapi, A.

We investigate the astrophysics of radio-emitting star-forming galaxies and active galactic nuclei (AGNs) and elucidate their statistical properties in the radio band, including luminosity functions, redshift distributions, and number counts at sub-mJy flux levels, which will be crucially probed by next-generation radio continuum surveys. Specifically, we exploit the model-independent approach by Mancuso et al. to compute the star formation rate functions, the AGN duty cycles, and the conditional probability of a star-forming galaxy to host an AGN with given bolometric luminosity. Coupling these ingredients with the radio emission properties associated with star formation and nuclear activity, we compute relevant statisticsmore » at different radio frequencies and disentangle the relative contribution of star-forming galaxies and AGNs in different radio luminosity, radio flux, and redshift ranges. Finally, we highlight that radio-emitting star-forming galaxies and AGNs are expected to host supermassive black holes accreting with different Eddington ratio distributions and to occupy different loci in the galaxy main-sequence diagrams. These specific predictions are consistent with current data sets but need to be tested with larger statistics via future radio data with multiband coverage on wide areas, as will become routinely achievable with the advent of the Square Kilometre Array and its precursors.« less

A search for circumstellar material around pulsars

NASA Astrophysics Data System (ADS)

Phillips, J. A.; Chandler, C. J.

1994-01-01

We have searched for thermal dust emission from circumstellar disks around five neutron stars using the Owens Valley millimeter array at 99 GHz and the James Clerk Maxwell Telescope at 380 GHz. Two of the neutron stars (PSR 0950+08 and 1133+16) are nearby isolated pulsars with characteristic ages 106 to 107 yr. The remaining three (PSR 1257+12, 1534+12, and 1937+21) are old millisecond pulsars with ages in the range 108 to 109 yr. None of the pulsars was detected above the noise, giving 2 sigma limits on the mass of disk material of approximately 10-2 solar mass if their disks are similar to those around pre-main-sequence stars. We discuss mechanisms for clearing dust grains from circumpulsar disks. We show that dust particles orbiting a neutron star lose angular momentum due to the ram pressure of the interstellar medium, which is approximately 104 times stronger for pulsars than for normal stars because of their high space velocity. For a pulsar moving at 100 km/s through an ambient medium with number density n approximately 1/cu cm, dust grains 0.1 micrometer(s) in size spiral into the star in approximately 106 years. This mechanism is more effective at clearing grains than the Poynting-Robertson effect and may limit the detectability of disks around old neutron stars.

Improvement of electrical resistivity tomography for leachate injection monitoring.

PubMed

Clément, R; Descloitres, M; Günther, T; Oxarango, L; Morra, C; Laurent, J-P; Gourc, J-P

2010-03-01

Leachate recirculation is a key process in the scope of operating municipal waste landfills as bioreactors, which aims to increase the moisture content to optimize the biodegradation in landfills. Given that liquid flows exhibit a complex behaviour in very heterogeneous porous media, in situ monitoring methods are required. Surface time-lapse electrical resistivity tomography (ERT) is usually proposed. Using numerical modelling with typical 2D and 3D injection plume patterns and 2D and 3D inversion codes, we show that wrong changes of resistivity can be calculated at depth if standard parameters are used for time-lapse ERT inversion. Major artefacts typically exhibit significant increases of resistivity (more than +30%) which can be misinterpreted as gas migration within the waste. In order to eliminate these artefacts, we tested an advanced time-lapse ERT procedure that includes (i) two advanced inversion tools and (ii) two alternative array geometries. The first advanced tool uses invariant regions in the model. The second advanced tool uses an inversion with a "minimum length" constraint. The alternative arrays focus on (i) a pole-dipole array (2D case), and (ii) a star array (3D case). The results show that these two advanced inversion tools and the two alternative arrays remove almost completely the artefacts within +/-5% both for 2D and 3D situations. As a field application, time-lapse ERT is applied using the star array during a 3D leachate injection in a non-hazardous municipal waste landfill. To evaluate the robustness of the two advanced tools, a synthetic model including both true decrease and increase of resistivity is built. The advanced time-lapse ERT procedure eliminates unwanted artefacts, while keeping a satisfactory image of true resistivity variations. This study demonstrates that significant and robust improvements can be obtained for time-lapse ERT monitoring of leachate recirculation in waste landfills. Copyright 2009 Elsevier Ltd. All rights reserved.

Improvement of electrical resistivity tomography for leachate injection monitoring

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

Clement, R., E-mail: remi.clement@hmg.inpg.f; Descloitres, M.; Guenther, T., E-mail: Thomas.Guenther@liag-hannover.d

2010-03-15

Leachate recirculation is a key process in the scope of operating municipal waste landfills as bioreactors, which aims to increase the moisture content to optimize the biodegradation in landfills. Given that liquid flows exhibit a complex behaviour in very heterogeneous porous media, in situ monitoring methods are required. Surface time-lapse electrical resistivity tomography (ERT) is usually proposed. Using numerical modelling with typical 2D and 3D injection plume patterns and 2D and 3D inversion codes, we show that wrong changes of resistivity can be calculated at depth if standard parameters are used for time-lapse ERT inversion. Major artefacts typically exhibit significantmore » increases of resistivity (more than +30%) which can be misinterpreted as gas migration within the waste. In order to eliminate these artefacts, we tested an advanced time-lapse ERT procedure that includes (i) two advanced inversion tools and (ii) two alternative array geometries. The first advanced tool uses invariant regions in the model. The second advanced tool uses an inversion with a 'minimum length' constraint. The alternative arrays focus on (i) a pole-dipole array (2D case), and (ii) a star array (3D case). The results show that these two advanced inversion tools and the two alternative arrays remove almost completely the artefacts within +/-5% both for 2D and 3D situations. As a field application, time-lapse ERT is applied using the star array during a 3D leachate injection in a non-hazardous municipal waste landfill. To evaluate the robustness of the two advanced tools, a synthetic model including both true decrease and increase of resistivity is built. The advanced time-lapse ERT procedure eliminates unwanted artefacts, while keeping a satisfactory image of true resistivity variations. This study demonstrates that significant and robust improvements can be obtained for time-lapse ERT monitoring of leachate recirculation in waste landfills.« less

Study of exoplanets host stars with VEGA/CHARA

NASA Astrophysics Data System (ADS)

Ligi, R.; Mourard, D.; Lagrange, Anne-Marie; Perraut, Karine; Tallon-Bosc, I.

2012-07-01

In the framework of the understanding of extrasolar systems, the study of host stars is a fundamental point. We need to understand the link between them and the presence of companions, i.e. what makes a star becoming a host star. In this perspective, we used the instrument called VEGA, situated at Mount Wilson (California) on the CHARA array to perform optical interferometric measurements. Interferometry at visible wavelengths allows reaching very high spatial frequencies well adapted for very small (less than 1 millisecond of arc) angular diameters. Therefore, we can access limb darkening measurements which is one of the very few directly measurable constraints on the structure of the atmosphere of a star. From this we can derive stars fundamental parameters. A precise measurement within spectral lines is also a very powerful tool to study the temperature and density structure of the atmosphere of distant stars. Besides, the detection of exoplanets is also related to this method. Combined with the radial velocity method and the transit method, one can study the atmosphere of exoplanets and learn more about their internal structure. We started a large program of observations made of 40 stars hosting exoplanets and observable by VEGA/CHARA. We will measure their limb darkened diameters and derive their parameters. We also aim at better understanding stellar noise sources like spots, and study surface brightness relationships.

Long-life 3-axis satellite attitude sensing, phase 1

NASA Technical Reports Server (NTRS)

Arild, Tor

1987-01-01

The purpose was to investigate the feasibility of new, moderate-cost, high reliability navigation sensors for high-altitude satellites, using stellar sources to obviate the use of gyroscopic devices. The primary investigation focused on the need for developing a star tracker model to replace an old star tracker which is still needed for current probe and satellite programs. One innovative element of the proposed star tracker was the design, development, and testing of technology components related to a phase scrambler plate. The purpose of the phase scrambler plate is to convert the impulse response of the optical system from a point image to a uniformly bright, square, angularly large, in-focus image of the star source. A collimated star source was built and tested. A breadboard star tracker with an 8 x 8 degree field of view was designed and built. It was tested in normal quad-cell mode (without the phase scrambler plate) and with the phase scrambler plate. Although the phase scrambler plate was crudely made, the performance of the star tracker breadboard was greatly improved using the phase scrambler plate, instead of system defocus. If further developed, the phase scrambler plate may be added as a low-cost retroconversion to any objective lens to greatly improve quad-cell or CCD array tracking; applications include star trackers, laser metrology, laser machining optics, and surveying instrumentation.

Radio Interferometry with the SMA: Uncovering Hidden Star Formation in Our Extreme Galactic Center

NASA Astrophysics Data System (ADS)

Gutierrez, Elizabeth; Battersby, Cara; MacGregor, Meredith Ann

2018-01-01

Radio interferometry provides the best tool to identify embedded star-forming cores in cold, dense, molecular clouds of gas and dust. Observations at long, submillimeter wavelengths can be used to investigate the physical properties in the youngest stages of star formation. Interferometers provide the resolution necessary to resolve small scale structures like dense cores where star formation is expected to occur. CMZoom is the first large area survey of the Central Molecular Zone (CMZ) at high resolution in the submillimeter, allowing us to identify early sites of star formation. The survey uses both the subcompact and compact configurations of the Submillimeter Array (SMA) interferometric radio telescope. The CMZ, or the inner 500 pc of the Milky Way Galaxy, is a high extinction region comprised of hot, dense, and turbulent molecular gas. This region is forming about an order of magnitude fewer stars than predicted based on simple star formation prescriptions. Here, we present new high resolution images of G0.068-0.075, a region from the CMZoom survey, obtained using CASA. We highlight the importance of interferometric observations of different baseline lengths by comparing the spatial information obtained through different configurations. We will use these new images, in conjunction with the rest of the CMZoom survey, to reveal the mechanisms driving star formation at the center of the galaxy.

KSC-2009-6236

NASA Image and Video Library

2009-11-09

CAPE CANAVERAL, Fla. – At the Astrotech Space Operations facility in Titusville, Fla., the Solar Dynamics Observatory, or SDO, with its solar arrays deployed, is ready to receive signal commands to test the release mechanism sequence for the arrays. SDO is the first space weather research network mission in NASA's Living With a Star Program. The spacecraft's long-term measurements will give solar scientists in-depth information about changes in the sun's magnetic field and insight into how they affect Earth. Liftoff on an Atlas V rocket is scheduled for Feb. 3, 2010. Photo credit: NASA/Jack Pfaller

Calibrating Images from the MINERVA Cameras

NASA Astrophysics Data System (ADS)

Mercedes Colón, Ana

2016-01-01

The MINiature Exoplanet Radial Velocity Array (MINERVA) consists of an array of robotic telescopes located on Mount Hopkins, Arizona with the purpose of performing transit photometry and spectroscopy to find Earth-like planets around Sun-like stars. In order to make photometric observations, it is necessary to perform calibrations on the CCD cameras of the telescopes to take into account possible instrument error on the data. In this project, we developed a pipeline that takes optical images, calibrates them using sky flats, darks, and biases to generate a transit light curve.

Polar-interferometry: what can be learnt from the IOTA/IONIC experiment

NASA Astrophysics Data System (ADS)

Le Bouquin, Jean-Baptiste; Rousselet-Perraut, Karine; Berger, Jean-Philippe; Herwats, Emilie; Benisty, Myriam; Absil, Olivier; Defrere, Denis; Monnier, John; Traub, Wesley

2008-07-01

We report the first near-IR polar-interferometric observations, performed at the IOTA array using its integrated optics combiner IONIC. Fringes have been obtained on calibration stars and resolved late-type giants. Optical modeling of the array and dedicated laboratory measures allowed us to confirm the good accuracy obtained on the calibrated polarized visibilities and closure phases. However, no evidences for polarimetric features at high angular resolution have been detected. The simulations and the results presented here open several perspectives for polar-interferometry, especially in the context of fibered, single-mode combiners.

Separated Fringe Packet Observations with the Chara Array. 1. Methods and New Orbits for chi Draconis, HD 184467, and HD 198084

DTIC Science & Technology

2010-06-01

similar experiments using the Infrared Optical Telescope Array ( IOTA ) on the well- studied, widely separated binary ζ Hercules, in an attempt to revive...SUBJECT TERMS 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT Same as Report (SAR) 18. NUMBER OF PAGES 11 19a. NAME OF RESPONSIBLE PERSON...SFPs with IOTA As noted by Dyck et al. (1995), for a binary star for which both components are within the field of view of the interferometer, it is

The missing links of neutron star evolution in the eROSITA all-sky X-ray survey

NASA Astrophysics Data System (ADS)

Pires, A. M.

2017-12-01

The observational manifestation of a neutron star is strongly connected with the properties of its magnetic field. During the star’s lifetime, the field strength and its changes dominate the thermo-rotational evolution and the source phenomenology across the electromagnetic spectrum. Signatures of magnetic field evolution are best traced among elusive groups of X-ray emitting isolated neutron stars (INSs), which are mostly quiet in the radio and γ-ray wavelengths. It is thus important to investigate and survey INSs in X-rays in the hope of discovering peculiar sources and the long-sought missing links that will help us to advance our understanding of neutron star evolution. The Extended Röntgen Survey with an Imaging Telescope Array (eROSITA), the primary instrument on the forthcoming Spectrum-RG mission, will scan the X-ray sky with unprecedented sensitivity and resolution. The survey has thus the unique potential to unveil the X-ray faint end of the neutron star population and probe sources that cannot be assessed by standard pulsar surveys.

The Impact of Indoor and Outdoor Radiometer Calibration on Solar Measurements: Preprint

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

Habte, Aron; Sengupta, Manajit; Andreas, Afshin

2016-07-01

Accurate solar radiation data sets are critical to reducing the expenses associated with mitigating performance risk for solar energy conversion systems, and they help utility planners and grid system operators understand the impacts of solar resource variability. The accuracy of solar radiation measured by radiometers depends on the instrument performance specification, installation method, calibration procedure, measurement conditions, maintenance practices, location, and environmental conditions. This study addresses the effect of calibration methodologies and the resulting calibration responsivities provided by radiometric calibration service providers such as the National Renewable Energy Laboratory (NREL) and manufacturers of radiometers. Some of these radiometers are calibratedmore » indoors, and some are calibrated outdoors. To establish or understand the differences in calibration methodology, we processed and analyzed field-measured data from these radiometers. This study investigates calibration responsivities provided by NREL's broadband outdoor radiometer calibration (BORCAL) and a few prominent manufacturers. The reference radiometer calibrations are traceable to the World Radiometric Reference. These different methods of calibration demonstrated 1% to 2% differences in solar irradiance measurement. Analyzing these values will ultimately assist in determining the uncertainties of the radiometer data and will assist in developing consensus on a standard for calibration.« less

Exploring Redox States, Doping and Ordering of Electroactive Star-Shaped Oligo(aniline)s.

PubMed

Mills, Benjamin M; Fey, Natalie; Marszalek, Tomasz; Pisula, Wojciech; Rannou, Patrice; Faul, Charl F J

2016-11-14

We have prepared a simple star-shaped oligo(aniline) (TDPB) and characterised it in detail by MALDI-TOF MS, UV/Vis/NIR spectroscopy, time-dependent DFT, cyclic voltammetry and EPR spectroscopy. TDPB is part of an underdeveloped class of π-conjugated molecules with great potential for organic electronics, display and sensor applications. It is redox active and reacts with acids to form radical cations. Acid-doped TDPB shows behaviour similar to discotic liquid crystals, with X-ray scattering investigations revealing columnar self-assembled arrays. The combination of unpaired electrons and supramolecular stacking suggests that star-shaped oligo(aniline)s like TDPB have the potential to form conducting nanowires and organic magnetic materials. © 2016 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

KSC-2012-3224a

NASA Image and Video Library

2012-06-06

KWAJALEIN ATOLL, Marshall Islands – Orbital Sciences' L-1011 carrier aircraft approaches the runway at the U.S. Army's Ronald Reagan Ballistic Missile Defense Test Site on Kwajalein Atoll to deliver Orbital’s Pegasus rocket and NASA’s Nuclear Spectroscopic Telescope Array, or NuSTAR, for launch. The Pegasus, mated to its NuSTAR payload, will be launched from the carrier aircraft 117 nautical miles south of Kwajalein at latitude 6.75 degrees north of the equator. The high-energy X-ray telescope will conduct a census of black holes, map radioactive material in young supernovae remnants, and study the origins of cosmic rays and the extreme physics around collapsed stars. Launch and deployment of the telescope is scheduled for June 13. For more information, visit http://www.nasa.gov/nustar. Photo courtesy of Orbital Sciences Corp.

The past, present and future of pulsars

NASA Astrophysics Data System (ADS)

Bell Burnell, Jocelyn

2017-12-01

On the 50th anniversary of the accidental discovery of pulsars (pulsating radio stars, also known as neutron stars) I reflect on the process of their detection and how our understanding of these stars gradually grew. Fifty years on, we have a much better (but still incomplete) understanding of these extreme objects, which I summarize here. The study of pulsars is advancing several areas of fundamental physics, including general relativity, particle physics, condensed-matter physics, and radiation processes in extreme electric and magnetic fields. New observational facilities coming online in the radio regime (such as the Five hundred meter Aperture Spherical Telescope and the Square Kilometre Array precursors) will revolutionize the search for pulsars by accessing thousands more, thus ushering in a new era of discovery for the field.

Seeing Stars - Intensity Interferometry in the Laboratory & on the Ground

NASA Astrophysics Data System (ADS)

Carlile, Colin; Dravins, Dainis

2018-04-01

In many ways it is a golden age for astronomy. Spectacular new discoveries, for example the detection of gravitational waves, are very dependent upon instrumental development. The specific instrument development we propose, Intensity Interferometry (II), aims toimprove the spatial resolution of optical telescopes by 100x to 50µas [1]. This is impractical to achieve by increasing the size of telescopes or by extending the capabilities of phase interferometry. II, if implemented on the Cherenkov Telescope Array (CTA) currently being installed in La Palma and Paranal, would record the light intensity – the photon train - from many different telescopes, up to 2 km apart, on a nanosecond timescale and compare them. The signal from the many pairs of telescopes would quantify the degree of correlation by extracting the second-order correlation function, and thus create an image. This is not a real space image. However we can invert the data by Fourier Transform and create a real image. The more telescopes, the better resolved and more physical is the image, enabling the study of sunspots on nearby stars; orbiting binary stars; or exoplanets traversing the disc of their own star. We understand the Sun well but we have little experimental knowledge of how representative it is of main sequence stars. To test the II method, at Lund Observatory we have set up a laboratory analogue comprising ten small telescopes observing an artificial star created by light from a laser. The method has been shown to work [2] and the telescope array has now been extended to two dimensions. We are in discussion with other groups to explore the possibility of implementing this method on real telescopes observing actual stars. We plan to do this with the prototype Small Size Telescopes being built by groups in Europe, and ultimately with the CTA itself. A Science Working Group for II has now been set up within the CTA Consortium, of which Lund University is an integral part. A Letter of Intent has been sent to CTA expressing these intentions. An attractive aspect of II is its complementarity to the principle goal of CTA - the exploration of high energy cosmic rays via the Cherenkov light they generate in the atmosphere. This can only be observed under the most demanding atmospheric conditions whereas II can be recorded when conditions are poor: with a bright Moon, during periods of turbulence; in hazy conditions; or after dusk and before dawn. Two further advantages of implementing an II option on CTA are the minimal marginal costs incurred to an already 400M€ investment and, secondly, that even a few telescopes would produce unique scientific results even in the early days when the CTA array is far from complete. [1] Dainis Dravins and Colin Carlile, SPIE Newsroom (2016), http://spie.org/newsroom/6504-kilometer-baseline-optical-intensity-interferometry-for-stellar-surface-observations [2] D. Dravins, T. Lagadec, P.D. Nuñez, Nature Communications 6, 6852 (2015)

Spitzer Reveals Stellar 'Family Tree'

NASA Technical Reports Server (NTRS)

2008-01-01

[figure removed for brevity, see original site] High resolution poster version

Generations of stars can be seen in this new infrared portrait from NASA's Spitzer Space Telescope. In this wispy star-forming region, called W5, the oldest stars can be seen as blue dots in the centers of the two hollow cavities (other blue dots are background and foreground stars not associated with the region). Younger stars line the rims of the cavities, and some can be seen as pink dots at the tips of the elephant-trunk-like pillars. The white knotty areas are where the youngest stars are forming. Red shows heated dust that pervades the region's cavities, while green highlights dense clouds.

W5 spans an area of sky equivalent to four full moons and is about 6,500 light-years away in the constellation Cassiopeia. The Spitzer picture was taken over a period of 24 hours.

Like other massive star-forming regions, such as Orion and Carina, W5 contains large cavities that were carved out by radiation and winds from the region's most massive stars. According to the theory of triggered star-formation, the carving out of these cavities pushes gas together, causing it to ignite into successive generations of new stars.

This image contains some of the best evidence yet for the triggered star-formation theory. Scientists analyzing the photo have been able to show that the ages of the stars become progressively and systematically younger with distance from the center of the cavities.

This is a three-color composite showing infrared observations from two Spitzer instruments. Blue represents 3.6-micron light and green shows light of 8 microns, both captured by Spitzer's infrared array camera. Red is 24-micron light detected by Spitzer's multiband imaging photometer.

Spitzer Reveals Stellar 'Family Tree'

NASA Technical Reports Server (NTRS)

2008-01-01

[figure removed for brevity, see original site] High resolution poster version

Generations of stars can be seen in this new infrared portrait from NASA's Spitzer Space Telescope. In this wispy star-forming region, called W5, the oldest stars can be seen as blue dots in the centers of the two hollow cavities (other blue dots are background and foreground stars not associated with the region). Younger stars line the rims of the cavities, and some can be seen as dots at the tips of the elephant-trunk-like pillars. The white knotty areas are where the youngest stars are forming.

W5 spans an area of sky equivalent to four full moons and is about 6,500 light-years away in the constellation Cassiopeia. The Spitzer picture was taken over a period of 24 hours.

Like other massive star-forming regions, such as Orion and Carina, W5 contains large cavities that were carved out by radiation and winds from the region's most massive stars. According to the theory of triggered star-formation, the carving out of these cavities pushes gas together, causing it to ignite into successive generations of new stars.

This image contains some of the best evidence yet for the triggered star-formation theory. Scientists analyzing the photo have been able to show that the ages of the stars become progressively and systematically younger with distance from the center of the cavities.

This picture was taken with Spitzer's infrared array camera. It is a four-color composite, in which light with a wavelength of 3.6 microns is blue; 4.5-micron light is green; 5.8-micron light is orange; and 8-micron light is red.

A Higher Efficiency of Converting Gas to Stars Pushes Galaxies at z ˜ 1.6 Well Above the Star-forming Main Sequence

NASA Astrophysics Data System (ADS)

Silverman, J. D.; Daddi, E.; Rodighiero, G.; Rujopakarn, W.; Sargent, M.; Renzini, A.; Liu, D.; Feruglio, C.; Kashino, D.; Sanders, D.; Kartaltepe, J.; Nagao, T.; Arimoto, N.; Berta, S.; Béthermin, M.; Koekemoer, A.; Lutz, D.; Magdis, G.; Mancini, C.; Onodera, M.; Zamorani, G.

2015-10-01

Local starbursts have a higher efficiency of converting gas into stars, as compared to typical star-forming galaxies at a given stellar mass, possibly indicative of different modes of star formation. With the peak epoch of galaxy formation occurring at z > 1, it remains to be established whether such an efficient mode of star formation is occurring at high redshift. To address this issue, we measure the molecular gas content of seven high-redshift (z ˜ 1.6) starburst galaxies with the Atacama Large Millimeter/submillimeter Array and IRAM/Plateau de Bure Interferometer. Our targets are selected from the sample of Herschel far-infrared-detected galaxies having star formation rates (˜300-800 M⊙ yr-1) elevated (≳4×) above the star-forming main sequence (MS) and included in the FMOS-COSMOS near-infrared spectroscopic survey of star-forming galaxies at z ˜ 1.6 with Subaru. We detect CO emission in all cases at high levels of significance, indicative of high gas fractions (˜30%-50%). Even more compelling, we firmly establish with a clean and systematic selection that starbursts, identified as MS outliers, at high redshift generally have a lower ratio of CO to total infrared luminosity as compared to typical MS star-forming galaxies, although with a smaller offset than expected based on past studies of local starbursts. We put forward a hypothesis that there exists a continuous increase in star formation efficiency with elevation from the MS with galaxy mergers as a possible physical driver. Along with a heightened star formation efficiency, our high-redshift sample is similar in other respects to local starbursts, such as being metal rich and having a higher ionization state of the interstellar medium.

Radiometals (non-Tc, non-Re) and Bifunctional Labeling Chemistry

NASA Astrophysics Data System (ADS)

Fani, M.; Good, S.; Maecke, H. R.

Radiometals are of increased current interest because of the growing use of targeted radiotherapy for tumors and the development of generators that produce positron-emitting radiometals. In addition, biomedical cyclotrons allow the cheap production of some relevant radiometals. The design of the corresponding radiopharmaceuticals includes the synthesis of bifunctional chelators, which carry a functional unit for the immobilization of the radiometal and a functional group for the covalent attachment to a vector molecule. Radiometals of interest for therapeutic applications are some lanthanides, 67Cu, and 90Y. For diagnostic applications 61Cu, 62Cu, 64Cu, 89Zr, and 68Ga are currently used and corresponding radiopharmaceuticals are being designed. In this chapter, some properties and the synthesis of bifunctional chelators including metal ion selectivity and special aspects of coupling chemistry are being described.

A hot wire radiant energy source for mapping the field of view of a radiometer

NASA Technical Reports Server (NTRS)

Edwards, S. F.; Stewart, W. F.; Vann, D. S.

1977-01-01

The design and performance of a calibration device that allows the measurement of a radiometer's field of view are described. The heart of the device is a heated 0.0254-mm (0.001-inch) diameter filament that provides a variable, isothermal line source of radiant energy against a cold background. By moving this discrete line source across the field of view of a radiometer, the radiometer's spatial response can be completely mapped. The use of a platinum filament provides a durable radiation source whose temperature is stable and repeatable to 10 K over the range of 600 to 1200 K. By varying the energy emitted by the filament, the field of view of radiometers with different sensitivities (or multiple channel radiometers) can be totally mapped.

The Ages of A-Stars. I. Interferometric Observations and Age Estimates for Stars in the Ursa Major Moving Group

NASA Astrophysics Data System (ADS)

Jones, Jeremy; White, R. J.; Boyajian, T.; Schaefer, G.; Baines, E.; Ireland, M.; Patience, J.; ten Brummelaar, T.; McAlister, H.; Ridgway, S. T.; Sturmann, J.; Sturmann, L.; Turner, N.; Farrington, C.; Goldfinger, P. J.

2015-11-01

We have observed and spatially resolved a set of seven A-type stars in the nearby Ursa Major moving group with the Classic, CLIMB, and PAVO beam combiners on the Center for High Angular Resolution Astronomy Array. At least four of these stars have large rotational velocities (v{sin}i ≳ 170 {km} {{{s}}}-1) and are expected to be oblate. These interferometric measurements, the stars’ observed photometric energy distributions, and v{sin}i values are used to computationally construct model oblate stars from which stellar properties (inclination, rotational velocity, and the radius and effective temperature as a function of latitude, etc.) are determined. The results are compared with MESA stellar evolution models to determine masses and ages. The value of this new technique is that it enables the estimation of the fundamental properties of rapidly rotating stars without the need to fully image the star. It can thus be applied to stars with sizes comparable to the interferometric resolution limit as opposed to those that are several times larger than the limit. Under the assumption of coevality, the spread in ages can be used as a test of both the prescription presented here and the MESA evolutionary code for rapidly rotating stars. With our validated technique, we combine these age estimates and determine the age of the moving group to be 414 ± 23 Myr, which is consistent with, but much more precise than previous estimates.

Ring of Stellar Death

NASA Technical Reports Server (NTRS)

2004-01-01

This false-color image from NASA's Spitzer Space Telescope shows a dying star (center) surrounded by a cloud of glowing gas and dust. Thanks to Spitzer's dust-piercing infrared eyes, the new image also highlights a never-before-seen feature -- a giant ring of material (red) slightly offset from the cloud's core. This clumpy ring consists of material that was expelled from the aging star.

The star and its cloud halo constitute a 'planetary nebula' called NGC 246. When a star like our own Sun begins to run out of fuel, its core shrinks and heats up, boiling off the star's outer layers. Leftover material shoots outward, expanding in shells around the star. This ejected material is then bombarded with ultraviolet light from the central star's fiery surface, producing huge, glowing clouds -- planetary nebulas -- that look like giant jellyfish in space.

In this image, the expelled gases appear green, and the ring of expelled material appears red. Astronomers believe the ring is likely made of hydrogen molecules that were ejected from the star in the form of atoms, then cooled to make hydrogen pairs. The new data will help explain how planetary nebulas take shape, and how they nourish future generations of stars.

This image composite was taken on Dec. 6, 2003, by Spitzer's infrared array camera, and is composed of images obtained at four wavelengths: 3.6 microns (blue), 4.5 microns (green), 5.8 microns (orange) and 8 microns (red).

Design and development of a multibeam 1.4 GHz pushbroom microwave radiometer

NASA Technical Reports Server (NTRS)

Lawrence, R. W.; Bailey, M. C.; Harrington, R. F.; Hearn, C. P.; Wells, J. G.; Stanley, W. D.

1986-01-01

The design and operation of a multiple beam, digital signal processing radiometer are discussed. The discussion includes a brief description of each major subsystem and an overall explanation of the hardware requirements and operation. A series of flight tests was conducted in which sea-truth sites, as well as an existing radiometer were used to verify the Pushbroom Radiometer performance. The results of these tests indicate that the Pushbroom Radiometer did meet the sensitivity design goal of 1.0 kelvin, and exceeded the accuracy requirement of 2.0 kelvin. Additional performance characteristics and test results are also presented.

A New Way to Demonstrate the Radiometer as a Heat Engine

ERIC Educational Resources Information Center

Hladkouski, V. I.; Pinchuk, A. I.

2015-01-01

While the radiometer is readily available as a toy, A. E. Woodruff notes that it is also a very useful tool to help us understand how to resolve certain scientific problems. Many physicists think they know how the radiometer works, but only a few actually understand it. Here we present a demonstration that shows that a radiometer can be thought of…

Shortwave Radiometer Calibration Methods Comparison and Resulting Solar Irradiance Measurement Differences: A User Perspective

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

Habte, Aron; Sengupta, Manajit; Andreas, Afshin

Banks financing solar energy projects require assurance that these systems will produce the energy predicted. Furthermore, utility planners and grid system operators need to understand the impact of the variable solar resource on solar energy conversion system performance. Accurate solar radiation data sets reduce the expense associated with mitigating performance risk and assist in understanding the impacts of solar resource variability. The accuracy of solar radiation measured by radiometers depends on the instrument performance specification, installation method, calibration procedure, measurement conditions, maintenance practices, location, and environmental conditions. This study addresses the effect of different calibration methods provided by radiometric calibrationmore » service providers, such as NREL and manufacturers of radiometers, on the resulting calibration responsivity. Some of these radiometers are calibrated indoors and some outdoors. To establish or understand the differences in calibration methodology, we processed and analyzed field-measured data from these radiometers. This study investigates calibration responsivities provided by NREL's broadband outdoor radiometer calibration (BORCAL) and a few prominent manufacturers. The BORCAL method provides the outdoor calibration responsivity of pyranometers and pyrheliometers at 45 degree solar zenith angle, and as a function of solar zenith angle determined by clear-sky comparisons with reference irradiance. The BORCAL method also employs a thermal offset correction to the calibration responsivity of single-black thermopile detectors used in pyranometers. Indoor calibrations of radiometers by their manufacturers are performed using a stable artificial light source in a side-by-side comparison between the test radiometer under calibration and a reference radiometer of the same type. In both methods, the reference radiometer calibrations are traceable to the World Radiometric Reference (WRR). These different methods of calibration demonstrated +1% to +2% differences in solar irradiance measurement. Analyzing these differences will ultimately help determine the uncertainty of the field radiometer data and guide the development of a consensus standard for calibration. Further advancing procedures for precisely calibrating radiometers to world reference standards that reduce measurement uncertainty will allow more accurate prediction of solar output and improve the bankability of solar projects.« less

Pulsar Candidate in Andromeda

NASA Image and Video Library

2017-03-23

NASA's Nuclear Spectroscope Telescope Array, or NuSTAR, has identified a candidate pulsar in Andromeda -- the nearest large galaxy to the Milky Way. This likely pulsar is brighter at high energies than the Andromeda galaxy's entire black hole population. The inset image shows the pulsar candidate in blue, as seen in X-ray light by NuSTAR. The background image of Andromeda was taken by NASA's Galaxy Evolution Explorer in ultraviolet light. Andromeda is a spiral galaxy like our Milky Way but larger in size. It lies 2.5 million light-years away in the Andromeda constellation. http://photojournal.jpl.nasa.gov/catalog/PIA20970

Mass loss

NASA Technical Reports Server (NTRS)

Goldberg, Leo

1987-01-01

Observational evidence for mass loss from cool stars is reviewed. Spectra line profiles are used for the derivation of mass-loss rates with the aid of the equation of continuity. This equation implies steady mass loss with spherical symmetry. Data from binary stars, Mira variables, and red giants in globular clusters are examined. Silicate emission is discussed as a useful indicator of mass loss in the middle infrared spectra. The use of thermal millimeter-wave radiation, Very Large Array (VLA) measurement of radio emission, and OH/IR masers are discussed as a tool for mass loss measurement. Evidence for nonsteady mass loss is also reviewed.

Development of an Aerosol Opacity Retrieval Algorithm for Use with Multi-Angle Land Surface Images

NASA Technical Reports Server (NTRS)

Diner, D.; Paradise, S.; Martonchik, J.

1994-01-01

In 1998, the Multi-angle Imaging SpectroRadiometer (MISR) will fly aboard the EOS-AM1 spacecraft. MISR will enable unique methods for retrieving the properties of atmospheric aerosols, by providing global imagery of the Earth at nine viewing angles in four visible and near-IR spectral bands. As part of the MISR algorithm development, theoretical methods of analyzing multi-angle, multi-spectral data are being tested using images acquired by the airborne Advanced Solid-State Array Spectroradiometer (ASAS). In this paper we derive a method to be used over land surfaces for retrieving the change in opacity between spectral bands, which can then be used in conjunction with an aerosol model to derive a bound on absolute opacity.

Assessment of the use of space technology in the monitoring of oil spills and ocean pollution: Technical volume. Executive summary

NASA Technical Reports Server (NTRS)

Alvarado, U. R. (Editor); Chafaris, G.; Chestek, J.; Contrad, J.; Frippel, G.; Gulatsi, R.; Heath, A.; Hodara, H.; Kritikos, H.; Tamiyasu, K.

1980-01-01

The potential of space systems and technology for detecting and monitoring ocean oil spills and waste pollution was assessed as well as the impact of this application on communication and data handling systems. Agencies charged with responsibilities in this area were identified and their measurement requirements were ascertained in order to determine the spatial resolution needed to characterize operational and accidental discharges. Microwave and optical sensors and sensing techniques were evaluated as candidate system elements. Capabilities are described for the following: synthetic aperture radar, microwave scatterometer, passive microwave radiometer, microwave altimeter, electro-optical sensors currently used in airborne detection, existing space-based optical sensors, the thematic mapper, and the pointable optical linear array.

Earthquake in Hindu Kush Region, Afghanistan

NASA Image and Video Library

2015-10-27

On Oct. 26, 2015, NASA Terra spacecraft acquired this image of northeastern Afghanistan where a magnitude 7.5 earthquake struck the Hindu Kush region. The earthquake's epicenter was at a depth of 130 miles (210 kilometers), on a probable shallowly dipping thrust fault. At this location, the Indian subcontinent moves northward and collides with Eurasia, subducting under the Asian continent, and raising the highest mountains in the world. This type of earthquake is common in the area: a similar earthquake occurred 13 years ago about 12 miles (20 kilometers) away. This perspective image from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument on NASA's Terra spacecraft, looking southwest, shows the hypocenter with a star. The image was acquired July 8, 2015, and is located near 36.4 degrees north, 70.7 degrees east. http://photojournal.jpl.nasa.gov/catalog/PIA20035

Solar array flight dynamic experiment

NASA Technical Reports Server (NTRS)

Schock, R. W.

1986-01-01

The purpose of the Solar Array Flight Dynamic Experiment (SAFDE) is to demonstrate the feasibility of on-orbit measurement and ground processing of large space structures dynamic characteristics. Test definition or verification provides the dynamic characteristic accuracy required for control systems use. An illumination/measurement system was developed to fly on space shuttle flight STS-31D. The system was designed to dynamically evaluate a large solar array called the Solar Array Flight Experiment (SAFE) that had been scheduled for this flight. The SAFDE system consisted of a set of laser diode illuminators, retroreflective targets, an intelligent star tracker receiver and the associated equipment to power, condition, and record the results. In six tests on STS-41D, data was successfully acquired from 18 retroreflector targets and ground processed, post flight, to define the solar array's dynamic characteristic. The flight experiment proved the viability of on-orbit test definition of large space structures dynamic characteristics. Future large space structures controllability should be greatly enhanced by this capability.

Solar array flight dynamic experiment

NASA Technical Reports Server (NTRS)

Schock, Richard W.

1986-01-01

The purpose of the Solar Array Flight Dynamic Experiment (SAFDE) is to demonstrate the feasibility of on-orbit measurement and ground processing of large space structures dynamic characteristics. Test definition or verification provides the dynamic characteristic accuracy required for control systems use. An illumination/measurement system was developed to fly on Space Shuttle flight STS-31D. The system was designed to dynamically evaluate a large solar array called the Solar Array Flight Experiment (SAFE) that had been scheduled for this flight. The SAFDE system consisted of a set of laser diode illuminators, retroreflective targets, an intelligent star tracker receiver and the associated equipment to power, condition, and record the results. In six tests on STS-41D, data was successfully acquired from 18 retroreflector targets and ground processed, post flight, to define the solar array's dynamic characteristic. The flight experiment proved the viability of on-orbit test definition of large space structures dynamic characteristics. Future large space structures controllability should be greatly enhanced by this capability.

Solar array flight dynamic experiment

NASA Technical Reports Server (NTRS)

Schock, Richard W.

1987-01-01

The purpose of the Solar Array Flight Dynamic Experiment (SAFDE) is to demonstrate the feasibility of on-orbit measurement and ground processing of large space structures' dynamic characteristics. Test definition or verification provides the dynamic characteristic accuracy required for control systems use. An illumination/measurement system was developed to fly on space shuttle flight STS-41D. The system was designed to dynamically evaluate a large solar array called the Solar Array Flight Experiment (SAFE) that had been scheduled for this flight. The SAFDE system consisted of a set of laser diode illuminators, retroreflective targets, an intelligent star tracker receiver and the associated equipment to power, condition, and record the results. In six tests on STS-41D, data was successfully acquired from 18 retroreflector targets and ground processed, post flight, to define the solar array's dynamic characteristic. The flight experiment proved the viability of on-orbit test definition of large space structures dynamic characteristics. Future large space structures controllability should be greatly enhanced by this capability.

Signal Processing for a Lunar Array: Minimizing Power Consumption

NASA Technical Reports Server (NTRS)

D'Addario, Larry; Simmons, Samuel

2011-01-01

Motivation for the study is: (1) Lunar Radio Array for low frequency, high redshift Dark Ages/Epoch of Reionization observations (z =6-50, f=30-200 MHz) (2) High precision cosmological measurements of 21 cm H I line fluctuations (3) Probe universe before first star formation and provide information about the Intergalactic Medium and evolution of large scale structures (5) Does the current cosmological model accurately describe the Universe before reionization? Lunar Radio Array is for (1) Radio interferometer based on the far side of the moon (1a) Necessary for precision measurements, (1b) Shielding from earth-based and solar RFI (12) No permanent ionosphere, (2) Minimum collecting area of approximately 1 square km and brightness sensitivity 10 mK (3)Several technologies must be developed before deployment The power needed to process signals from a large array of nonsteerable elements is not prohibitive, even for the Moon, and even in current technology. Two different concepts have been proposed: (1) Dark Ages Radio Interferometer (DALI) (2)( Lunar Array for Radio Cosmology (LARC)

Intercomparison of 51 radiometers for determining global horizontal irradiance and direct normal irradiance measurements

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

Habte, Aron; Sengupta, Manajit; Andreas, Afshin

Accurate solar radiation measurements require properly installed and maintained radiometers with calibrations traceable to the World Radiometric Reference. This study analyzes the performance of 51 commercially available and prototype radiometers used for measuring global horizontal irradiances or direct normal irradiances. These include pyranometers, pyrheliometers, rotating shadowband radiometers, and a pyranometer with an internal shading mask deployed at the National Renewable Energy Laboratory's (NREL) Solar Radiation Research Laboratory. The radiometers in this study were deployed for one year (from April 1, 2011, through March 31, 2012), and their measurements were compared under clear-sky, partly cloudy, and mostly cloudy conditions to referencemore » values of low estimated measurement uncertainties. The intent of this paper is to present a general overview of each radiometer's performance based on the instrumentation and environmental conditions available at NREL.« less

The DC-8 Submillimeter-Wave Cloud Ice Radiometer

NASA Technical Reports Server (NTRS)

Walter, Steven J.; Batelaan, Paul; Siegel, Peter; Evans, K. Franklin; Evans, Aaron; Balachandra, Balu; Gannon, Jade; Guldalian, John; Raz, Guy; Shea, James

2000-01-01

An airborne radiometer is being developed to demonstrate the capability of radiometry at submillimeter-wavelengths to characterize cirrus clouds. At these wavelengths, cirrus clouds scatter upwelling radiation from water vapor in the lower troposphere. Radiometric measurements made at multiple widely spaced frequencies permit flux variations caused by changes in scattering due to crystal size to be distinguished from changes in cloud ice content. Measurements at dual polarizations can also be used to constrain the mean crystal shape. An airborne radiometer measuring the upwelling submillimeter-wave flux should then able to retrieve both bulk and microphysical cloud properties. The radiometer is being designed to make measurements at four frequencies (183 GHz, 325 GHz, 448 GHz, and 643 GHz) with dual-polarization capability at 643 GHz. The instrument is being developed for flight on NASA's DC-8 and will scan cross-track through an aircraft window. Measurements with this radiometer in combination with independent ground-based and airborne measurements will validate the submillimeter-wave radiometer retrieval techniques. The goal of this effort is to develop a technique to enable spaceborne characterization of cirrus, which will meet a key climate measurement need. The development of an airborne radiometer to validate cirrus retrieval techniques is a critical step toward development of spaced-based radiometers to investigate and monitor cirrus on a global scale. The radiometer development is a cooperative effort of the University of Colorado, Colorado State University, Swales Aerospace, and Jet Propulsion Laboratory and is funded by the NASA Instrument Incubator Program.

Formaldehyde in Absorption: Tracing Molecular Gas in Early-Type Galaxies

NASA Astrophysics Data System (ADS)

Dollhopf, Niklaus M.; Donovan Meyer, Jennifer

2016-01-01

Early-Type Galaxies (ETGs) have been long-classified as the red, ellipsoidal branch of the classic Hubble tuning fork diagram of galactic structure. In part with this classification, ETGs are thought to be molecular and atomic gas-poor with little to no recent star formation. However, recent efforts have questioned this ingrained classification. Most notably, the ATLAS3D survey of 260 ETGs within ~40 Mpc found 22% contain CO, a common tracer for molecular gas. The presence of cold molecular gas also implies the possibility for current star formation within these galaxies. Simulations do not accurately predict the recent observations and further studies are necessary to understand the mechanisms of ETGs.CO traces molecular gas starting at densities of ~102 cm-3, which makes it a good tracer of bulk molecular gas, but does little to constrain the possible locations of star formation within the cores of dense molecular gas clouds. Formaldehyde (H2CO) traces molecular gas on the order of ~104 cm-3, providing a further constraint on the location of star-forming gas, while being simple enough to possibly be abundant in gas-poor ETGs. In cold molecular clouds at or above ~104 cm-3 densities, the structure of formaldehyde enables a phenomenon in which rotational transitions have excitation temperatures driven below the temperature of the cosmic microwave background (CMB), ~2.7 K. Because the CMB radiates isotropically, formaldehyde can be observed in absorption, independent of distance, as a tracer of moderately-dense molecular clouds and star formation.This novel observation technique of formaldehyde was incorporated for observations of twelve CO-detected ETGs from the ATLAS3D sample, including NGC 4710 and PGC 8815, to investigate the presence of cold molecular gas, and possible star formation, in ETGs. We present images from the Very Large Array, used in its C-array configuration, of the J = 11,0 - 11,1 transition of formaldehyde towards these sources. We report our preliminary results here.Niklaus M. Dollhopf gratefully acknowledges the support of the National Radio Astronomy Observatory Summer Student REU Program sponsored by the National Science Foundation.

The Star Formation in Radio Survey: Jansky Very Large Array 33 GHz Observations of Nearby Galaxy Nuclei and Extranuclear Star-forming Regions

NASA Astrophysics Data System (ADS)

Murphy, E. J.; Dong, D.; Momjian, E.; Linden, S.; Kennicutt, R. C., Jr.; Meier, D. S.; Schinnerer, E.; Turner, J. L.

2018-02-01

We present 33 GHz imaging for 112 pointings toward galaxy nuclei and extranuclear star-forming regions at ≈2″ resolution using the Karl G. Jansky Very Large Array (VLA) as part of the Star Formation in Radio Survey. A comparison with 33 GHz Robert C. Byrd Green Bank Telescope single-dish observations indicates that the interferometric VLA observations recover 78% ± 4% of the total flux density over 25″ regions (≈kpc scales) among all fields. On these scales, the emission being resolved out is most likely diffuse non-thermal synchrotron emission. Consequently, on the ≈30–300 pc scales sampled by our VLA observations, the bulk of the 33 GHz emission is recovered and primarily powered by free–free emission from discrete H II regions, making it an excellent tracer of massive star formation. Of the 225 discrete regions used for aperture photometry, 162 are extranuclear (i.e., having galactocentric radii r G ≥ 250 pc) and detected at >3σ significance at 33 GHz and in Hα. Assuming a typical 33 GHz thermal fraction of 90%, the ratio of optically-thin 33 GHz to uncorrected Hα star formation rates indicates a median extinction value on ≈30–300 pc scales of A Hα ≈ 1.26 ± 0.09 mag, with an associated median absolute deviation of 0.87 mag. We find that 10% of these sources are “highly embedded” (i.e., A Hα ≳ 3.3 mag), suggesting that on average, H II regions remain embedded for ≲1 Myr. Finally, we find the median 33 GHz continuum-to-Hα line flux ratio to be statistically larger within r G < 250 pc relative to the outer disk regions by a factor of 1.82 ± 0.39, while the ratio of 33 GHz to 24 μm flux densities is lower by a factor of 0.45 ± 0.08, which may suggest increased extinction in the central regions.

A Submillimeter Perspective on the Goods Fields. II. The High Radio Power Population in the Goods-N

NASA Astrophysics Data System (ADS)

Barger, A. J.; Cowie, L. L.; Owen, F. N.; Hsu, L.-Y.; Wang, W.-H.

2017-01-01

We use ultradeep 20 cm data from the Karl G. Jansky Very Large Array and 850 μm data from SCUBA-2 and the Submillimeter Array of an 124 arcmin2 region of the Chandra Deep Field-north to analyze the high radio power ({P}20{cm}> {10}31 erg s-1 Hz-1) population. We find that 20 (42 ± 9%) of the spectroscopically identified z> 0.8 sources have consistent star formation rates (SFRs) inferred from both submillimeter and radio observations, while the remaining sources have lower (mostly undetected) submillimeter fluxes, suggesting that active galactic nucleus (AGN) activity dominates the radio power in these sources. We develop a classification scheme based on the ratio of submillimeter flux to radio power versus radio power and find that it agrees with AGN and star-forming galaxy classifications from Very Long Baseline Interferometry. Our results provide support for an extremely rapid drop in the number of high SFR galaxies above about a thousand solar masses per year (Kroupa initial mass function) and for the locally determined relation between X-ray luminosity and radio power for star-forming galaxies applying at high redshifts and high radio powers. We measure far-infrared (FIR) luminosities and find that some AGNs lie on the FIR-radio correlation, while others scatter below. The AGNs that lie on the correlation appear to do so based on their emission from the AGN torus. We measure a median radio size of 1.″0 ± 0.3 for the star-forming galaxies. The radio sizes of the star-forming galaxies are generally larger than those of the AGNs. The W. M. Keck Observatory is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA, and was made possible by the generous financial support of the W. M. Keck Foundation.

The Search for Extraterrestrial Intelligence in Earth's Solar Transit Zone.

PubMed

Heller, René; Pudritz, Ralph E

2016-04-01

Over the past few years, astronomers have detected thousands of planets and candidate planets by observing their periodic transits in front of their host stars. A related method, called transit spectroscopy, might soon allow studies of the chemical imprints of life in extrasolar planetary atmospheres. Here, we address the reciprocal question, namely, from where is Earth detectable by extrasolar observers using similar methods. We explore Earth's transit zone (ETZ), the projection of a band around Earth's ecliptic onto the celestial plane, where observers can detect Earth transits across the Sun. ETZ is between 0.520° and 0.537° wide due to the noncircular Earth orbit. The restricted Earth transit zone (rETZ), where Earth transits the Sun less than 0.5 solar radii from its center, is about 0.262° wide. We first compile a target list of 45 K and 37 G dwarf stars inside the rETZ and within 1 kpc (about 3260 light-years) using the Hipparcos catalogue. We then greatly enlarge the number of potential targets by constructing an analytic galactic disk model and find that about 10(5) K and G dwarf stars should reside within the rETZ. The ongoing Gaia space mission can potentially discover all G dwarfs among them (several 10(4)) within the next 5 years. Many more potentially habitable planets orbit dim, unknown M stars in ETZ and other stars that traversed ETZ thousands of years ago. If any of these planets host intelligent observers, they could have identified Earth as a habitable, or even as a living, world long ago, and we could be receiving their broadcasts today. The K2 mission, the Allen Telescope Array, the upcoming Square Kilometer Array, or the Green Bank Telescope might detect such deliberate extraterrestrial messages. Ultimately, ETZ would be an ideal region to be monitored by the Breakthrough Listen Initiatives, an upcoming survey that will constitute the most comprehensive search for extraterrestrial intelligence so far.

The Search for Extraterrestrial Intelligence in Earth's Solar Transit Zone

NASA Astrophysics Data System (ADS)

Heller, René; Pudritz, Ralph E.

2016-04-01

Over the past few years, astronomers have detected thousands of planets and candidate planets by observing their periodic transits in front of their host stars. A related method, called transit spectroscopy, might soon allow studies of the chemical imprints of life in extrasolar planetary atmospheres. Here, we address the reciprocal question, namely, from where is Earth detectable by extrasolar observers using similar methods. We explore Earth's transit zone (ETZ), the projection of a band around Earth's ecliptic onto the celestial plane, where observers can detect Earth transits across the Sun. ETZ is between 0.520° and 0.537° wide due to the noncircular Earth orbit. The restricted Earth transit zone (rETZ), where Earth transits the Sun less than 0.5 solar radii from its center, is about 0.262° wide. We first compile a target list of 45 K and 37 G dwarf stars inside the rETZ and within 1 kpc (about 3260 light-years) using the Hipparcos catalogue. We then greatly enlarge the number of potential targets by constructing an analytic galactic disk model and find that about 105 K and G dwarf stars should reside within the rETZ. The ongoing Gaia space mission can potentially discover all G dwarfs among them (several 104) within the next 5 years. Many more potentially habitable planets orbit dim, unknown M stars in ETZ and other stars that traversed ETZ thousands of years ago. If any of these planets host intelligent observers, they could have identified Earth as a habitable, or even as a living, world long ago, and we could be receiving their broadcasts today. The K2 mission, the Allen Telescope Array, the upcoming Square Kilometer Array, or the Green Bank Telescope might detect such deliberate extraterrestrial messages. Ultimately, ETZ would be an ideal region to be monitored by the Breakthrough Listen Initiatives, an upcoming survey that will constitute the most comprehensive search for extraterrestrial intelligence so far.

Nobeyama Radio Observatory

NASA Astrophysics Data System (ADS)

Murdin, P.

2000-11-01

Nobeyama Radio Observatory has telescopes at millimeter and submillimeter wavelengths. It was established in 1982 as an observatory of Tokyo Astronomical Observatory (NATIONAL ASTRONOMICAL OBSERVATORY, JAPAN since 1987), and operates the 45 m telescope, Nobeyama Millimeter Array, and Radioheliograph. High-resolution images of star forming regions and molecular clouds have revealed many aspects of...

Two Thumbs Up, Five Stars, and an Oscar?

ERIC Educational Resources Information Center

Riley, Tracy

1998-01-01

Discusses the themes of "Good Will Hunting" and "Titanic" and their messages to educators. The need for gifted children to have an array of people in their lives to nurture their abilities and the need for the development of a New Zealand national policy for gifted children is emphasized. (CR)

Aircraft Route Optimization using the A-Star Algorithm

DTIC Science & Technology

2014-03-27

Map Cost array allows a search for a route that not only seeks to minimize the distance travelled, but also considers other factors that may impact ...Rules (VFR) flight profile requires aviators to plan a 20-minute fuel reserve into the flight while an Instrument Flight Rules ( IFR ) flight profile

Compton thick AGN in the NuSTAR era

NASA Astrophysics Data System (ADS)

Marchesi, Stefano; Ajello, Marco; Marcotulli, Lea; Comastri, Andrea

2017-08-01

The recent launch of the Nuclear Spectroscopic Telescope Array (NuSTAR), the first telescope with focusing optics at >10 keV, represented a major breakthrough in the study of obscured active galactic nuclei (AGN). In this talk, I present the results of the 0.3-100 keV spectral analysis of the 30 Compton thick (CT-; i.e., those sources having column density NH>1E24 cm-2) AGN detected within z~0.1 in the BAT 100-month survey with available NuSTAR data. Particularly, I will focus on how adding NuSTAR data to the 0.3-10 keV information helps to characterize the CT-AGN population, significantly improving the measurements of important X-ray spectral parameters such as the photon index, the intrinsic absorption, the intensity of the Iron K alpha line at 6.4 keV and the obscuring torus opening angle. Finally, I will discuss the role of these objects in the context of obscured AGN accretion physics, and their contribution to the cosmic X-ray background.

VLBA Determination of the Distance to Nearby Star-forming Regions. VIII. The LkHα 101 Cluster

NASA Astrophysics Data System (ADS)

Dzib, Sergio A.; Ortiz-León, Gisela N.; Loinard, L.; Mioduszewski, A. J.; Rodríguez, L. F.; Medina, S.-N. X.; Torres, R. M.

2018-02-01

The LkHα 101 cluster takes its name from its more massive member, the LkHα 101 star, which is an ∼15 M ⊙ star whose true nature is still unknown. The distance to the LkHα 101 cluster has been controversial for the last few decades, with estimated values ranging from 160 to 800 pc. We have observed members and candidate members of the LkHα 101 cluster with signs of magnetic activity, using the Very Long Baseline Array, in order to measure their trigonometric parallax and, thus, obtain a direct measurement of their distances. A young star member, LkHα 101 VLA J043001.15+351724.6, was detected at four epochs as a single radio source. The best fit to its displacement on the plane of the sky yields a distance of 535 ± 29 pc. We argue that this is the distance to the LkHα 101 cluster.

Microwave radiometer and scatterometer design for the aquarius sea surface Salinity Mission

NASA Technical Reports Server (NTRS)

Wilson, William J.; Yueh, Simon H.; Pellerano, Fernando

2004-01-01

The measurement of sea surface salinity with L-band microwave radiometers is a very challenging task. Since the L-band brightness temperature variations associated with salinity changes are small, it is necessary to have a very sensitive and stable radiometer. In addition, the corrections for the ocean surface roughness require real time scatterometer measurements. The designs of the Aquarius radiometer and scatterometer are described in this paper.

The radiometer transfer function for the AAFE composite two-frequency radiometer scatterometer. M.S. Thesis - Pennsylvania Univ.

NASA Technical Reports Server (NTRS)

Moore, J. H.

1973-01-01

A model was developed for the switching radiometer utilizing a continuous method of calibration. Sources of system degradation were identified and include losses and voltage standing wave ratios in front of the receiver input. After computing the three modes of operation, expressions were developed for the normalized radiometer output, the minimum detectable signal (normalized RMS temperature fluctuation), sensitivity, and accuracy correction factors).

Scheduling Observations of Celestial Objects for Earth Observing Sensor Calibration

NASA Technical Reports Server (NTRS)

Wilson, Truman; Xiong, Xiaoxiong

2016-01-01

Radiometric calibration of Earth-observing satellite sensors is critical for tracking on-orbit gain changes through- out the satellite's mission. The Moon, being a stable, well-characterized radiometric target, has been used effectively for tracking the relative gain changes of the reflective solar bands for the Moderate Resolution Imaging Spectroradiometer (MODIS) on board EOS AM-1 (Terra) and PM-1 (Aqua). The Moon is viewed through the MODIS space-view port, and the relative phase of the Moon is restricted to within 0.5 degrees of a chosen target phase to increase the accuracy of the calibration. These geometric restrictions require spacecraft maneuvers in order to bring space-view port into proper alignment with the position of the Moon when the phase requirement is met. In this paper, we describe a versatile tool for scheduling such maneuvers based on the required geometry and lunar phase restrictions for a general spacecraft bound instrument. The results of the scheduling tool have been verified using lunar images from Aqua and Terra MODIS after a scheduled roll maneuver was performed. This tool has also been tested for the Visible Infrared Imaging Radiometer Suite (VIIRS) and the Advanced Technology Microwave Sounder on-board the Suomi-NPP spacecraft. As an extension of this work, we have also developed a tool for scheduling views of bright stars. These stars provide another well-characterized radiometric source that can be used for sensor calibration. This tool has been implemented to determine the times in which a chosen star can be viewed by the high gain stages of the day/night band for the VIIRS instrument.

First Transmitted Hyperspectral Light Measurements and Cloud Properties from Recent Field Campaign Sampling Clouds Under Biomass Burning Aerosol

NASA Technical Reports Server (NTRS)

Leblanc, S.; Redemann, Jens; Shinozuka, Yohei; Flynn, Connor J.; Segal Rozenhaimer, Michal; Kacenelenbogen, Meloe Shenandoah; Pistone, Kristina Marie Myers; Schmidt, Sebastian; Cochrane, Sabrina

2016-01-01

We present a first view of data collected during a recent field campaign aimed at measuring biomass burning aerosol above clouds from airborne platforms. The NASA ObseRvations of CLouds above Aerosols and their intEractionS (ORACLES) field campaign recently concluded its first deployment sampling clouds and overlying aerosol layer from the airborne platform NASA P3. We present results from the Spectrometer for Sky-Scanning, Sun-Tracking Atmospheric Research (4STAR), in conjunction with the Solar Spectral Flux Radiometers (SSFR). During this deployment, 4STAR sampled transmitted solar light either via direct solar beam measurements and scattered light measurements, enabling the measurement of aerosol optical thickness and the retrieval of information on aerosol particles in addition to overlying cloud properties. We focus on the zenith-viewing scattered light measurements, which are used to retrieve cloud optical thickness, effective radius, and thermodynamic phase of clouds under a biomass burning layer. The biomass burning aerosol layer present above the clouds is the cause of potential bias in retrieved cloud optical depth and effective radius from satellites. We contrast the typical reflection based approach used by satellites to the transmission based approach used by 4STAR during ORACLES for retrieving cloud properties. It is suspected that these differing approaches will yield a change in retrieved properties since light transmitted through clouds is sensitive to a different cloud volume than reflected light at cloud top. We offer a preliminary view of the implications of these differences in sampling volumes to the calculation of cloud radiative effects (CRE).

Ground registration of data from an airborne Multifrequency Microwave Radiometer (MfMR). [Colby, Kansas

NASA Technical Reports Server (NTRS)

Richter, J. C. (Principal Investigator)

1981-01-01

The agricultural soil moisture experiment was conducted near Colby, Kansas, in July and August 1978. A portion of the data collected was taken with a five band microwave radiometer. A method of locating the radiometer footprints with respect to a ground based coordinate system is documented. The procedure requires that the airplane's flight parameters along with aerial photography be acquired simultaneously with the radiometer data. The software which documented reads in data from the precision radiation thermometer (PRT Model 5) and attaches the scene temperature to the corresponding multifrequency microwave radiometer data. Listings of the programs used in the registration process are included.

Preliminary development of digital signal processing in microwave radiometers

NASA Technical Reports Server (NTRS)

Stanley, W. D.

1980-01-01

Topics covered involve a number of closely related tasks including: the development of several control loop and dynamic noise model computer programs for simulating microwave radiometer measurements; computer modeling of an existing stepped frequency radiometer in an effort to determine its optimum operational characteristics; investigation of the classical second order analog control loop to determine its ability to reduce the estimation error in a microwave radiometer; investigation of several digital signal processing unit designs; initiation of efforts to develop required hardware and software for implementation of the digital signal processing unit; and investigation of the general characteristics and peculiarities of digital processing noiselike microwave radiometer signals.

Comparison of Profiling Microwave Radiometer, Aircraft, and Radiosonde Measurements From the Alliance Icing Research Study (AIRS)

NASA Technical Reports Server (NTRS)

Reehorst, Andrew L.

2001-01-01

Measurements from a profiling microwave radiometer are compared to measurements from a research aircraft and radiosondes. Data compared is temperature, water vapor, and liquid water profiles. Data was gathered at the Alliance Icing Research Study (AIRS) at Mirabel Airport outside Montreal, Canada during December 1999 and January 2000. All radiometer measurements were found to lose accuracy when the radome was wet. When the radome was not wetted, the radiometer was seen to indicate an inverted distribution of liquid water within a cloud. When the radiometer measurements were made at 15 deg. instead of the standard zenith, the measurements were less accurate.

The Structure of the Star-forming Cluster RCW 38

NASA Astrophysics Data System (ADS)

Winston, E.; Wolk, S. J.; Bourke, T. L.; Megeath, S. T.; Gutermuth, R.; Spitzbart, B.

2011-12-01

We present a study of the structure of the high-mass star-forming region RCW 38 and the spatial distribution of its young stellar population. Spitzer Infrared Array Camera (IRAC) photometry (3-8 μm) is combined with Two Micron All Sky Survey near-IR data to identify young stellar objects (YSOs) by IR-excess emission from their circumstellar material. Chandra X-ray data are used to identify class III pre-main-sequence stars lacking circumstellar material. We identify 624 YSOs: 23 class 0/I and 90 flat spectrum protostars, 437 class II stars, and 74 class III stars. We also identify 29 (27 new) O star candidates over the IRAC field. Seventy-two stars exhibit IR-variability, including 7 class 0/I and 12 flat spectrum YSOs. A further 177 tentative candidates are identified by their location in the IRAC [3.6] versus [3.6]-[5.8] color-magnitude diagram. We find strong evidence of subclustering in the region. Three subclusters were identified surrounding the central cluster, with massive and variable stars in each subcluster. The central region shows evidence of distinct spatial distributions of the protostars and pre-main-sequence stars. A previously detected IR cluster, DB2001_Obj36, has been established as a subcluster of RCW 38. This suggests that star formation in RCW 38 occurs over a more extended area than previously thought. The gas-to-dust ratio is examined using the X-ray derived hydrogen column density, N H and the K-band extinction, and found to be consistent with the diffuse interstellar medium, in contrast with Serpens and NGC 1333. We posit that the high photoionizing flux of massive stars in RCW 38 affects the agglomeration of the dust grains.

Searching for dark matter with neutron star mergers and quiet kilonovae

NASA Astrophysics Data System (ADS)

Bramante, Joseph; Linden, Tim; Tsai, Yu-Dai

2018-03-01

We identify new astrophysical signatures of dark matter that implodes neutron stars (NSs), which could decisively test whether NS-imploding dark matter is responsible for missing pulsars in the Milky Way galactic center, the source of some r -process elements, and the origin of fast-radio bursts. First, NS-imploding dark matter forms ˜10-10 solar mass or smaller black holes inside neutron stars, which proceed to convert neutron stars into ˜1.5 solar mass black holes (BHs). This decreases the number of neutron star mergers seen by LIGO/Virgo (LV) and associated merger kilonovae seen by telescopes like DES, BlackGEM, and ZTF, instead producing a population of "black mergers" containing ˜1.5 solar mass black holes. Second, dark matter-induced neutron star implosions may create a new kind of kilonovae that lacks a detectable, accompanying gravitational signal, which we call "quiet kilonovae." Using DES data and the Milky Way's r-process abundance, we constrain quiet kilonovae. Third, the spatial distribution of neutron star merger kilonovae and quiet kilonovae in galaxies can be used to detect dark matter. NS-imploding dark matter destroys most neutron stars at the centers of disc galaxies, so that neutron star merger kilonovae would appear mostly in a donut at large radii. We find that as few as ten neutron star merger kilonova events, located to ˜1 kpc precision could validate or exclude dark matter-induced neutron star implosions at 2 σ confidence, exploring dark matter-nucleon cross-sections 4-10 orders of magnitude below current direct detection experimental limits. Similarly, NS-imploding dark matter as the source of fast radio bursts can be tested at 2 σ confidence once 20 bursts are located in host galaxies by radio arrays like CHIME and HIRAX.

Tracing the atomic nitrogen abundance in star-forming regions with ammonia deuteration

NASA Astrophysics Data System (ADS)

Furuya, Kenji; Persson, Magnus V.

2018-06-01

Partitioning of elemental nitrogen in star-forming regions is not well constrained. Most nitrogen is expected to be partitioned among atomic nitrogen (N I), molecular nitrogen (N_2), and icy N-bearing molecules, such as NH_3 and N_2. N I is not directly observable in the cold gas. In this paper, we propose an indirect way to constrain the amount of N I in the cold gas of star-forming clouds, via deuteration in ammonia ice, the [ND2H/NH2D]/[NH2D/NH3] ratio. Using gas-ice astrochemical simulations, we show that if atomic nitrogen remains as the primary reservoir of nitrogen during cold ice formation stages, the [ND2H/NH2D]/[NH2D/NH3] ratio is close to the statistical value of 1/3 and lower than unity, whereas if atomic nitrogen is largely converted into N-bearing molecules, the ratio should be larger than unity. Observability of ammonia isotopologues in the inner hot regions around low-mass protostars, where ammonia ice has sublimated, is also discussed. We conclude that the [ND2H/NH2D]/[NH2D/NH3] ratio can be quantified using a combination of Very Large Array and Atacama Large Millimeter/submillimeter Array observations with reasonable integration times, at least towards IRAS 16293-2422, where high molecular column densities are expected.

THE MAGNETOSPHERE OF THE ULTRACOOL DWARF DENIS 1048-3956

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

Ravi, V.; Hallinan, G.; Hobbs, G.

2011-07-01

Ultracool dwarfs, the least-massive contributors to the stellar mass function, exhibit striking magnetic properties that are inconsistent with trends for more massive stars. Here, we present the widest-band radio observations to date of an ultracool dwarf, DENIS-P J104814.9-395604, in four 2 GHz bandwidths between wavelengths of 1 cm and 10 cm. These data were obtained with the Australia Telescope Compact Array using the new Compact Array Broadband Backend instrument. We detected a stable negatively sloped power-law spectrum in total intensity, with spectral index {alpha} = 1.71 {+-} 0.09. Circular polarization fractions between 0.25 and 0.4 were found at the low-frequencymore » end of our detection band. We interpret these results as indicative of gyrosynchrotron emission. We suggest that the radio emission originates from beyond the corotation radius, R{sub C} , of the star. Adopting this model, we find R{sub C} between 1.2 R{sub *} and 2.9 R{sub *}, and a non-thermal electron density and magnetic field strength between 10{sup 5} and 10{sup 7.2} cm{sup -3} and between 70 and 260 G, respectively, at R{sub C} . The model accounts for the violation of the Guedel-Benz relation between X-ray and radio luminosities of low-mass stars by DENIS-P J104814.9-395604.« less

The environment of the wind-wind collision region of η Carinae

NASA Astrophysics Data System (ADS)

Panagiotou, C.; Walter, R.

2018-02-01

Context. η Carinae is a colliding wind binary hosting two of the most massive stars and featuring the strongest wind collision mechanical luminosity. The wind collision region of this system is detected in X-rays and γ-rays and offers a unique laboratory for the study of particle acceleration and wind magneto-hydrodynamics. Aim. Our main goal is to use X-ray observations of η Carinae around periastron to constrain the wind collision zone geometry and understand the reasons for its variability. Methods: We analysed 10 Nuclear Spectroscopic Telescope Array (NuSTAR) observations, which were obtained around the 2014 periastron. The NuSTAR array monitored the source from 3 to 30 keV, which allowed us to grasp the continuum and absorption parameters with very good accuracy. We were able to identify several physical components and probe their variability. Results: The X-ray flux varied in a similar way as observed during previous periastrons and largely as expected if generated in the wind collision region. The flux detected within 10 days of periastron is lower than expected, suggesting a partial disruption of the central region of the wind collision zone. The Fe Kα line is likely broadened by the electrons heated along the complex shock fronts. The variability of its equivalent width indicates that the fluorescence region has a complex geometry and that the source obscuration varies quickly with the line of sight.

A Stellar Ripple

NASA Technical Reports Server (NTRS)

2006-01-01

This false-color composite image shows the Cartwheel galaxy as seen by the Galaxy Evolution Explorer's far ultraviolet detector (blue); the Hubble Space Telescope's wide field and planetary camera 2 in B-band visible light (green); the Spitzer Space Telescope's infrared array camera at 8 microns (red); and the Chandra X-ray Observatory's advanced CCD imaging spectrometer-S array instrument (purple).

Approximately 100 million years ago, a smaller galaxy plunged through the heart of Cartwheel galaxy, creating ripples of brief star formation. In this image, the first ripple appears as an ultraviolet-bright blue outer ring. The blue outer ring is so powerful in the Galaxy Evolution Explorer observations that it indicates the Cartwheel is one of the most powerful UV-emitting galaxies in the nearby universe. The blue color reveals to astronomers that associations of stars 5 to 20 times as massive as our sun are forming in this region. The clumps of pink along the outer blue ring are regions where both X-rays and ultraviolet radiation are superimposed in the image. These X-ray point sources are very likely collections of binary star systems containing a blackhole (called massive X-ray binary systems). The X-ray sources seem to cluster around optical/ultraviolet-bright supermassive star clusters.

The yellow-orange inner ring and nucleus at the center of the galaxy result from the combination of visible and infrared light, which is stronger towards the center. This region of the galaxy represents the second ripple, or ring wave, created in the collision, but has much less star formation activity than the first (outer) ring wave. The wisps of red spread throughout the interior of the galaxy are organic molecules that have been illuminated by nearby low-level star formation. Meanwhile, the tints of green are less massive, older visible-light stars.

Although astronomers have not identified exactly which galaxy collided with the Cartwheel, two of three candidate galaxies can be seen in this image to the bottom left of the ring, one as a neon blob and the other as a green spiral.

Previously, scientists believed the ring marked the outermost edge of the galaxy, but the latest GALEX observations detect a faint disk, not visible in this image, that extends to twice the diameter of the ring.

Electromagnetic Design and Performance of a Conical Microwave Blackbody Target for Radiometer Calibration

NASA Astrophysics Data System (ADS)

Houtz, Derek A.; Emery, William; Gu, Dazhen; Jacob, Karl; Murk, Axel; Walker, David K.; Wylde, Richard J.

2017-08-01

A conical cavity has been designed and fabricated for use as a broadband passive microwave calibration source, or blackbody, at the National Institute of Standards and Technology. The blackbody will be used as a national primary standard for brightness temperature and will allow for the prelaunch calibration of spaceborne radiometers and calibration of ground-based systems to provide traceability among radiometric data. The conical geometry provides performance independent of polarization, minimizing reflections, and standing waves, thus having a high microwave emissivity. The conical blackbody has advantages over typical pyramidal array geometries, including reduced temperature gradients and excellent broadband electromagnetic performance over more than a frequency decade. The blackbody is designed for use between 18 and 230 GHz, at temperatures between 80 and 350 K, and is vacuum compatible. To approximate theoretical blackbody behavior, the design maximizes emissivity and thus minimizes reflectivity. A newly developed microwave absorber is demonstrated that uses cryogenically compatible, thermally conductive two-part epoxy with magnetic carbonyl iron (CBI) powder loading. We measured the complex permittivity and permeability properties for different CBI-loading percentages; the conical absorber is then designed and optimized with geometric optics and finite-element modeling, and finally, the reflectivity of the resulting fabricated structure is measured. We demonstrated normal incidence reflectivity considerably below -40 dB at all relevant remote sensing frequencies.

Boundary-Layer Characteristics Over a Coastal Megacity

NASA Astrophysics Data System (ADS)

Melecio-Vazquez, D.; Ramamurthy, P.; Arend, M.; Moshary, F.; Gonzalez, J.

2017-12-01

Boundary-layer characteristics over New York City are analyzed for various local and synoptic conditions over several seasons. An array of vertical profilers, including a Doppler LiDAR, a micro-pulse LiDAR and a microwave radiometer are used to observe the structure and evolution of the boundary-layer. Additionally, an urbanized Weather Research and Forecasting (uWRF) model coupled to a high resolution landcover/land-use database is used to study the spatial variability in boundary layer characteristics. The summer daytime averaged potential temperature profile from the microwave radiometer shows the presence of a thermal internal boundary layer wherein a superadiabatic layer lies underneath a stable layer instead of a mixed-layer. Both the winter daytime and nighttime seasonal averages show that the atmosphere remains unstable near the surface and does not reach stable conditions during the nighttime. The mixing ratio seasonal averages show peaks in humidity near 200-m and 1100-m, above instrument level, which could result from sea breeze and anthropogenic sources. Ceilometer measurements show a high degree of variability in boundary layer height depending on wind direction. Comparison with uWRF results show that the model tends to overestimate convective efficiency for selected summer and winter cases and therefore shows a much deeper thermal boundary layer than the observed profiles. The model estimates a less humid atmosphere than seen in observations.

METimage: an innovative multi-spectral imaging radiometer for the EUMETSAT polar system follow-on satellite mission

NASA Astrophysics Data System (ADS)

Alpers, Matthias; Brüns, Christian; Pillukat, Alexander

2017-11-01

The evolving needs of the meteorological community concerning the EUMETSAT Polar System follow-on satellite mission (Post-EPS) require the development of a high-performance multi-spectral imaging radiometer. Recognizing these needs, Jena Optronik GmbH proposed an innovative instrument concept, which comprises a high flexibility to adapt to user requirements as a very important feature. Core parameters like ground sampling distance (GSD), number and width of spectral channels, signal-to-noise ratio, polarization control and calibration facilities can be chosen in a wide range without changing the basic instrument configuration. Core item of the METimage instrument is a rotating telescope scanner to cover the large swath width of about 2800 km, which all polar platforms need for global coverage. The de-rotated image facilitates use of in-field spectral channel separation, which allows tailoring individual channel GSD (ground sampling distance) and features like TDI (time delay and integration). State-of-the-art detector arrays and readout electronics can easily be employed. Currently, the German DLR Space Agency, Jena- Optronik GmbH and AIM Infrarot Module GmbH work together implementing core assemblies of METimage: the rotating telescope scanner and the infrared detectors. The METimage instrument phase B study was kicked-off in September 2008. Germany intents to provide METimage as an in-kind contribution of the first METimage flight model to the EUMETSAT Post-EPS Programme.

Radiometer for accurate (+ or - 1%) measurement of solar irradiance equal to 10,000 solar constants

NASA Technical Reports Server (NTRS)

Kendall, J. M., Sr.

1981-01-01

The 10,000 solar constant radiometer was developed for the accurate (+ or - 1%) measurement of the irradiance produced in the image formed by a parabolic reflector or by a multiple mirror solar installation. This radiometer is water cooled, weighs about 1 kg, and is 5 cm (2 in.) in diameter by 10 cm (4 in.) long. A sting is provided for mounting the radiometer in the solar installation capable of measuring irradiances as high as 20,000 solar constants, the instrument is self calibrating. Its accuracy depends on the accurate determination of the cavity aperture, and absorptivity of the cavity, and accurate electrical measurements. The spectral response is flat over the entire spectrum from far UV to far IR. The radiometer responds to a measurement within 99.7% of the final value within 8 s. During a measurement of the 10,000 solar constant irradiance, the temperature rise of the water is about 20 C. The radiometer has perfect cosine response up to 60 deg off the radiometer axis.

Star Formation in Henize 206

NASA Image and Video Library

2004-03-08

This image from NASA Spitzer Space Telescope, shows the wispy filamentary structure of Henize 206, is a four-color composite mosaic created by combining data from an infrared array camera IRAC. The LMC is a small satellite galaxy gravitationally bound to our own Milky Way. Yet the gravitational effects are tearing the companion to shreds in a long-playing drama of 'intergalactic cannibalism.' These disruptions lead to a recurring cycle of star birth and star death. Astronomers are particularly interested in the LMC because its fractional content of heavy metals is two to five times lower than is seen in our solar neighborhood. [In this context, 'heavy elements' refer to those elements not present in the primordial universe. Such elements as carbon, oxygen and others are produced by nucleosynthesis and are ejected into the interstellar medium via mass loss by stars, including supernova explosions.] As such, the LMC provides a nearby cosmic laboratory that may resemble the distant universe in its chemical composition. The primary Spitzer image, showing the wispy filamentary structure of Henize 206, is a four-color composite mosaic created by combining data from an infrared array camera (IRAC) at near-infrared wavelengths and the mid-infrared data from a multiband imaging photometer (MIPS). Blue represents invisible infrared light at wavelengths of 3.6 and 4.5 microns. Note that most of the stars in the field of view radiate primarily at these short infrared wavelengths. Cyan denotes emission at 5.8 microns, green depicts the 8.0 micron light, and red is used to trace the thermal emission from dust at 24 microns. The separate instrument images are included as insets to the main composite. An inclined ring of emission dominates the central and upper regions of the image. This delineates a bubble of hot, x-ray emitting gas that was blown into space when a massive star died in a supernova explosion millions of years ago. The shock waves from that explosion impacted a cloud of nearby hydrogen gas, compressed it, and started a new generation of star formation. The death of one star led to the birth of many new stars. This is particularly evident in the MIPS inset, where the 24-micron emission peaks correspond to newly formed stars. The ultraviolet and visible-light photons from the new stars are absorbed by surrounding dust and re-radiated at longer infrared wavelengths, where it is detected by Spitzer. This emission nebula was cataloged by Karl Henize (HEN-eyes) while spending 1948-1951 in South Africa doing research for his Ph.D. dissertation at the University of Michigan. Henize later became a NASA astronaut and, at age 59, became the oldest rookie to fly on the Space Shuttle during an eight-day flight of the Challenger in 1985. He died just short of his 67th birthday in 1993 while attempting to climb the north face of Mount Everest, the world's highest peak. http://photojournal.jpl.nasa.gov/catalog/PIA05517

Special Pyrheliometer Shroud Development

NASA Technical Reports Server (NTRS)

Dennison, E. W.

1984-01-01

To insure that the insolation values accurately represent the input power to a power conversion unit the field of view (FOV) of the concentrator aperture and the insolation radiometer must be the same. The calculations, implementation, and results of this approach are covered. Three instruments were used to measure the insolation: an Eppley Normal Incidence Radiometer (NIP) and two versions of the kendall cavity radiometer. The shrouds used to limit the FOV of the radiometers were designed to simulate the FOV of the PDC-1 concentrater with the cold water cavity calorimeter. This technique of matching the FOV of an insolation radiometer to the FOV of a specific concentrater and receiver aperture appears to be both practical and effective. The efficiency of a power conversion unit will be too low if the insolation is measured with a radiometer which has a FOV which is larger than the FOV of the concentrator.

Earth Radiation Budget Experiment scanner radiometric calibration results

NASA Technical Reports Server (NTRS)

Lee, Robert B., III; Gibson, M. A.; Thomas, Susan; Meekins, Jeffrey L.; Mahan, J. R.

1990-01-01

The Earth Radiation Budget Experiment (ERBE) scanning radiometers are producing measurements of the incoming solar, earth/atmosphere-reflected solar, and earth/atmosphere-emitted radiation fields with measurement precisions and absolute accuracies, approaching 1 percent. ERBE uses thermistor bolometers as the detection elements in the narrow-field-of-view scanning radiometers. The scanning radiometers can sense radiation in the shortwave, longwave, and total broadband spectral regions of 0.2 to 5.0, 5.0 to 50.0, and 0.2 to 50.0 micrometers, respectively. Detailed models of the radiometers' response functions were developed in order to design the most suitable calibration techniques. These models guided the design of in-flight calibration procedures as well as the development and characterization of a vacuum-calibration chamber and the blackbody source which provided the absolute basis upon which the total and longwave radiometers were characterized. The flight calibration instrumentation for the narror-field-of-view scanning radiometers is presented and evaluated.

Large Antenna Multifrequency Microwave Radiometer (LAMMR) system design

NASA Technical Reports Server (NTRS)

King, J. L.

1980-01-01

The large Antenna Multifrequency Microwave Radiometer (LAMMR) is a high resolution 4 meter aperture scanning radiometer system designed to determine sea surface temperature and wind speed, atmospheric water vapor and liquid water, precipitation, and various sea ice parameters by interpreting brightness temperature images from low Earth orbiting satellites. The LAMMR with dual linear horizontal and vertical polarization radiometer channels from 1.4 to 91 GHZ can provide multidiscipline data with resolutions from 105 to 7 km. The LAMMR baseline radiometer system uses total power radiometers to achieve delta T's in the 0.5 to 1.7 K range and system calibration accuracies in the 1 to 2 deg range. A cold sky horn/ambient load two point calibration technique is used in this baseline concept and the second detector output uses an integrated and dump circuit to sample the scanning cross-tract resolution cells.

In-flight shortwave calibrations of the active cavity radiometers using tungsten lamps

NASA Technical Reports Server (NTRS)

Thomas, Susan; Lee, Robert B.; Gibson, Michael A.; Wilson, Robert S.; Bolden, William C.

1992-01-01

The Earth Radiation Budget Experiment (ERBE) active cavity radiometers are used to measure the incoming solar, reflected shortwave solar, and emitted longwave radiations from the Earth and atmosphere. The radiometers are located on the NASA's Earth Radiation Budget Satellite (ERBS) and the NOAA-9 and NOAA-10 spacecraft platforms. Two of the radiometers, one wide field of view (WFOV) and one medium field of view (MFOV), measure the total radiation in the spectral region of 0.2 to 50 microns and the other two radiometers (WFOV and MFOV) measure the shortwave radiation in the spectral region of 0.2 to 5.0 microns. For the in-flight calibrations, tungsten lamp and the sun are used as calibration sources for shortwave radiometers. Descriptions of the tungsten lamp and solar calibration procedures and mechanisms are presented. The tungsten lamp calibration measurements are compared with the measurements of solar calibration for ERBS and NOAA-9 instruments.

A 94/183 GHz aircraft radiometer system for Project Storm Fury

NASA Technical Reports Server (NTRS)

Gagliano, J. A.; Stratigos, J. A.; Forsythe, R. E.; Schuchardt, J. M.; Welch, J. M.; Gallentine, D. O.

1980-01-01

A radiometer design suitable for use in NASA's WB-57F aircraft to collect data from severe storm regions was developed. The design recommended was a 94/183 GHz scanning radiometer with 3 IF channels on either side of the 183.3 GHz water vapor line and a single IF channel for a low loss atmospheric window channel at 94 GHz. The development and construction of the 94/183 GHz scanning radiometer known as the Advanced Microwave Moisture Sounder (AMMS) is presented. The radiometer scans the scene below the aircraft over an angle of + or - 45 degrees with the beamwidth of the scene viewed of approximately 2 degrees at 94 GHz and 1 degree at 183 GHz. The AMMS data collection system consists of a microcomputer used to store the radiometer data on the flight cartridge recorder, operate the stepper motor driven scanner, and collect housekeeping data such as thermistor temperature readings and aircraft time code.

Miniature Extreme Ultraviolet Solar Radiometers

NASA Astrophysics Data System (ADS)

McMullin, D. R.; Seely, J. F.; Bremer, J.; Jones, A. R.; Vest, R.; Sakdinawat, A.

2015-12-01

Free-standing zone plates for use in EUV solar radiometers have been fabricated using electron beam lithography and calibrated at the NIST SURF synchrotron facility. The radiometers that we are developing use zone plates (ZPs) to focus the total solar irradiance in narrow EUV spectral bands and measure it with negligible sensitivity to field angle and polarization, and with greater accuracy and greater long-term stability than radiometers that have alternative architectures. These radiometers are easy to accommodate on spacecraft due to their small size, low mass, low power requirements, low data rates, and modest pointing requirements. A proto-type instrument will be presented with performance characteristics and spacecraft resource requirements for hosting these new instruments. The compact size of the optical train make these zone plates attractive for small CubeSats. The robustness of the compact design makes these radiometers available for a large variety of applications.

Microstrip Antenna for Remote Sensing of Soil Moisture and Sea Surface Salinity

NASA Technical Reports Server (NTRS)

Ramhat-Samii, Yahya; Kona, Keerti; Manteghi, Majid; Dinardo, Steven; Hunter, Don; Njoku, Eni; Wilson, Wiliam; Yueh, Simon

2009-01-01

This compact, lightweight, dual-frequency antenna feed developed for future soil moisture and sea surface salinity (SSS) missions can benefit future soil and ocean studies by lowering mass, volume, and cost of the antenna system. It also allows for airborne soil moisture and salinity remote sensors operating on small aircraft. While microstrip antenna technology has been developed for radio communications, it has yet to be applied to combined radar and radiometer for Earth remote sensing. The antenna feed provides a key instrument element enabling high-resolution radiometric observations with large, deployable antennas. The design is based on the microstrip stacked-patch array (MSPA) used to feed a large, lightweight, deployable, rotating mesh antenna for spaceborne L-band (approximately equal to 1 GHz) passive and active sensing systems. The array consists of stacked patches to provide dual-frequency capability and suitable radiation patterns. The stacked-patch microstrip element was designed to cover the required L-band center frequencies at 1.26 GHz (lower patch) and 1.413 GHz (upper patch), with dual-linear polarization capabilities. The dimension of patches produces the required frequencies. To achieve excellent polarization isolation and control of antenna sidelobes for the MSPA, the orientation of each stacked-patch element within the array is optimized to reduce the cross-polarization. A specialized feed-distribution network was designed to achieve the required excitation amplitude and phase for each stacked-patch element.

Multi-epoch very long baseline interferometric observations of the nuclear starburst region of NGC 253: Improved modeling of the supernova and star formation rates

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

Rampadarath, H.; Morgan, J. S.; Tingay, S. J.

2014-01-01

The results of multi-epoch observations of the southern starburst galaxy, NGC 253, with the Australian Long Baseline Array at 2.3 GHz are presented. As with previous radio interferometric observations of this galaxy, no new sources were discovered. By combining the results of this survey with Very Large Array observations at higher frequencies from the literature, spectra were derived and a free-free absorption model was fitted of 20 known sources in NGC 253. The results were found to be consistent with previous studies. The supernova remnant, 5.48-43.3, was imaged with the highest sensitivity and resolution to date, revealing a two-lobed morphology.more » Comparisons with previous observations of similar resolution give an upper limit of 10{sup 4} km s{sup –1} for the expansion speed of this remnant. We derive a supernova rate of <0.2 yr{sup –1} for the inner 300 pc using a model that improves on previous methods by incorporating an improved radio supernova peak luminosity distribution and by making use of multi-wavelength radio data spanning 21 yr. A star formation rate of SFR(M ≥ 5 M {sub ☉}) < 4.9 M {sub ☉} yr{sup –1} was also estimated using the standard relation between supernova and star formation rates. Our improved estimates of supernova and star formation rates are consistent with studies at other wavelengths. The results of our study point to the possible existence of a small population of undetected supernova remnants, suggesting a low rate of radio supernova production in NGC 253.« less

Extra X-rays at the Hub of Our Milky Way Galaxy

NASA Image and Video Library

2015-04-29

NASA's Nuclear Spectroscopic Telescope Array, or NuSTAR, has captured a new high-energy X-ray view (magenta, Figure 1) of the bustling center of our Milky Way galaxy. The smaller circle shows the area where the NuSTAR image was taken -- the very center of our galaxy, where a giant black hole resides. That region is enlarged to the right, in the larger circle, to show the NuSTAR data. The NuSTAR picture is one of the most detailed ever taken of the center of our galaxy in high-energy X-rays. The X-ray light, normally invisible to our eyes, has been assigned the color magenta. The brightest point of light near the center of the X-ray picture is coming from a spinning dead star, known as a pulsar, which is near the giant black hole. While the pulsar's X-ray emissions were known before, scientists were surprised to find more high-energy X-rays than predicted in the surrounding regions, seen here as the elliptical haze. Astronomers aren't sure what the sources of the extra X-rays are, but one possibility is a population of dead stars. The background picture was captured in infrared light by NASA's Spitzer Space Telescope. The NuSTAR image has an X-ray energy range of 20 to 40 kiloelectron volts. http://photojournal.jpl.nasa.gov/catalog/PIA19334

PHOTOMETRY OF VARIABLE STARS FROM DOME A, ANTARCTICA: RESULTS FROM THE 2010 OBSERVING SEASON

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

Wang, Lingzhi; Zhu, Zonghong; Macri, Lucas M.

We present results from a season of observations with the Chinese Small Telescope ARray, obtained over 183 days of the 2010 Antarctic winter. We carried out high-cadence time-series aperture photometry of 9125 stars with i ∼< 15.3 mag located in a 23 deg{sup 2} region centered on the south celestial pole. We identified 188 variable stars, including 67 new objects relative to our 2008 observations, thanks to broader synoptic coverage, a deeper magnitude limit, and a larger field of view. We used the photometric data set to derive site statistics from Dome A. Based on two years of observations, wemore » find that extinction due to clouds at this site is less than 0.1 and 0.4 mag during 45% and 75% of the dark time, respectively.« less

KSC-2012-3203

NASA Image and Video Library

2012-06-05

VANDENBERG AIR FORCE BASE, Calif. – An Orbital Sciences’ Pegasus rocket and NASA’s Nuclear Spectroscopic Telescope Array, or NuSTAR, are installed under Orbital’s L-1011 carrier aircraft awaiting departure from Vandenberg Air Force Base in California for the U.S. Army's Ronald Reagan Ballistic Missile Defense Test Site on Kwajalein Atoll, part of the Marshall Islands in the Pacific Ocean. The Pegasus, mated to its NuSTAR payload, will be launched from the carrier aircraft 117 nautical miles south of Kwajalein at latitude 6.75 degrees north of the equator. The high-energy X-ray telescope will conduct a census of black holes, map radioactive material in young supernovae remnants, and study the origins of cosmic rays and the extreme physics around collapsed stars. Launch is scheduled for June 13. For more information, visit http://www.nasa.gov/nustar. Photo credit: NASA/Randy Beaudoin, VAFB

KSC-2012-1388

NASA Image and Video Library

2012-02-16

VANDENBERG AIR FORCE BASE, Calif. -- Technicians move the tilt-rotation fixture holding NASA's NuSTAR spacecraft inside Orbital Sciences' processing facility at Vandenberg Air Force Base, Calif. The spacecraft will be rotated to horizontal for joining with the Pegasus XL rocket. The Orbital Sciences Pegasus will launch NASA's Nuclear Spectroscopic Telescope Array NuSTAR into space. After the rocket and spacecraft are processed at Vandenberg, they will be flown on Orbital's L-1011 carrier aircraft to the Ronald Reagan Ballistic Missile Defense Test Site at the Pacific Ocean’s Kwajalein Atoll for launch. The high-energy x-ray telescope will conduct a census for black holes, map radioactive material in young supernovae remnants, and study the origins of cosmic rays and the extreme physics around collapsed stars. For more information, visit science.nasa.gov/missions/nustar/. Photo credit: NASA/Randy Beaudoin, VAFB

KSC-2012-3227a

NASA Image and Video Library

2012-06-06

KWAJALEIN ATOLL, Marshall Islands – Orbital Sciences' L-1011 carrier aircraft has arrived at the U.S. Army's Ronald Reagan Ballistic Missile Defense Test Site on Kwajalein Atoll, delivering Orbital’s Pegasus rocket and NASA’s Nuclear Spectroscopic Telescope Array, or NuSTAR, from Vandenberg Air Force Base in California. The Pegasus, mated to its NuSTAR payload, will be launched from the carrier aircraft 117 nautical miles south of Kwajalein at latitude 6.75 degrees north of the equator. The high-energy X-ray telescope will conduct a census of black holes, map radioactive material in young supernovae remnants, and study the origins of cosmic rays and the extreme physics around collapsed stars. Launch and deployment of the telescope is scheduled for June 13. For more information, visit http://www.nasa.gov/nustar. Photo courtesy of Orbital Sciences Corp.

KSC-2012-1367

NASA Image and Video Library

2012-02-16

VANDENBERG AIR FORCE BASE, Calif. -- At Vandenberg Air Force Base's processing facility in California, technicians prepare NASA’s NuSTAR spacecraft to be lifted into a tilt-rotation fixture. The spacecraft will be rotated to horizontal for joining with the Pegasus XL rocket. The Orbital Sciences Pegasus will launch NASA's Nuclear Spectroscopic Telescope Array NuSTAR into space. After the rocket and spacecraft are processed at Vandenberg, they will be flown on Orbital's L-1011 carrier aircraft to the Ronald Reagan Ballistic Missile Defense Test Site at the Pacific Ocean’s Kwajalein Atoll for launch. The high-energy x-ray telescope will conduct a census for black holes, map radioactive material in young supernovae remnants, and study the origins of cosmic rays and the extreme physics around collapsed stars. For more information, visit science.nasa.gov/missions/nustar/. Photo credit: NASA/Randy Beaudoin, VAFB

KSC-2012-1381

NASA Image and Video Library

2012-02-16

VANDENBERG AIR FORCE BASE, Calif. -- At Vandenberg Air Force Base in California, technicians inside Orbital Sciences' processing facility watch as NASA's NuSTAR spacecraft is lifted by the tilt-rotation fixture. The spacecraft will be rotated to horizontal for joining with the Pegasus XL rocket. The Orbital Sciences Pegasus will launch NASA's Nuclear Spectroscopic Telescope Array NuSTAR into space. After the rocket and spacecraft are processed at Vandenberg, they will be flown on Orbital's L-1011 carrier aircraft to the Ronald Reagan Ballistic Missile Defense Test Site at the Pacific Ocean’s Kwajalein Atoll for launch. The high-energy x-ray telescope will conduct a census for black holes, map radioactive material in young supernovae remnants, and study the origins of cosmic rays and the extreme physics around collapsed stars. For more information, visit science.nasa.gov/missions/nustar/. Photo credit: NASA/Randy Beaudoin, VAFB

KSC-2012-1371

NASA Image and Video Library

2012-02-16

VANDENBERG AIR FORCE BASE, Calif. -- Inside Orbital Sciences' processing facility at Vandenberg Air Force Base in California, a lifting device is lowered toward NASA's NuSTAR spacecraft. The spacecraft will be rotated to horizontal for joining with the Pegasus XL rocket. The Orbital Sciences Pegasus will launch NASA's Nuclear Spectroscopic Telescope Array NuSTAR into space. After the rocket and spacecraft are processed at Vandenberg, they will be flown on Orbital's L-1011 carrier aircraft to the Ronald Reagan Ballistic Missile Defense Test Site at the Pacific Ocean’s Kwajalein Atoll for launch. The high-energy x-ray telescope will conduct a census for black holes, map radioactive material in young supernovae remnants, and study the origins of cosmic rays and the extreme physics around collapsed stars. For more information, visit science.nasa.gov/missions/nustar/. Photo credit: NASA/Randy Beaudoin, VAFB

Spiral density waves in a young protoplanetary disk.

PubMed

Pérez, Laura M; Carpenter, John M; Andrews, Sean M; Ricci, Luca; Isella, Andrea; Linz, Hendrik; Sargent, Anneila I; Wilner, David J; Henning, Thomas; Deller, Adam T; Chandler, Claire J; Dullemond, Cornelis P; Lazio, Joseph; Menten, Karl M; Corder, Stuartt A; Storm, Shaye; Testi, Leonardo; Tazzari, Marco; Kwon, Woojin; Calvet, Nuria; Greaves, Jane S; Harris, Robert J; Mundy, Lee G

2016-09-30

Gravitational forces are expected to excite spiral density waves in protoplanetary disks, disks of gas and dust orbiting young stars. However, previous observations that showed spiral structure were not able to probe disk midplanes, where most of the mass is concentrated and where planet formation takes place. Using the Atacama Large Millimeter/submillimeter Array, we detected a pair of trailing symmetric spiral arms in the protoplanetary disk surrounding the young star Elias 2-27. The arms extend to the disk outer regions and can be traced down to the midplane. These millimeter-wave observations also reveal an emission gap closer to the star than the spiral arms. We argue that the observed spirals trace shocks of spiral density waves in the midplane of this young disk. Copyright © 2016, American Association for the Advancement of Science.

Direct Interferometric Imaging with IOTA Interferometer: Morphology of the Water Shell around U Ori

NASA Astrophysics Data System (ADS)

Pluzhnik, Eugene; Ragland, S.; Le Coroller, H.; Cotton, W.; Danchi, W.; Traub, W.; Willson, L.

2007-12-01

Optical interferometric observations of Mira stars with adequate resolution using the 3-telescope Infrared Optical Telescope Array (IOTA) interferometer have shown detectable asymmetry in several Mira stars. Several mechanisms have been proposed to explain the observed asymmetry. In this paper, we present subsequent IOTA observations of a Mira star, namely, U Ori taken at 1.51, 1.64 and 1.78 μm in 2005. The reconstructed images based on a model independent algorithm are also presented. These images show asymmetric structures of the water shell that is similar to the structure of 22 GHz masers obtained by Vlemmings et al. in 2003. We explore the possibility of the detection of molecular shell rotation with a period of about 30 years by comparing our results with radio observations and discuss a possible geometric structure of the shell.

Near-Infrared Keck Interferometer and IOTA Closure Phase Observations of Wolf-Rayet stars

NASA Astrophysics Data System (ADS)

Rajagopal, J.; Wallace, D.; Barry, R.; Richardson, L. J.; Traub, W.; Danchi, W. C.

We present first results from observations of a small sample of IR-bright Wolf-Rayet stars with the Keck Interferometer in the near-infrared, and with the IONIC beam three-telescope beam combiner at the Infrared and Optical Telescope Array (IOTA) observatory. The former results were obtained as part of shared-risk observations in commissioning the Keck Interferometer and form a subset of a high-resolution study of dust around Wolf-Rayet stars using multiple interferometers in progress in our group. The latter results are the first closure phase observations of these stars in the near-infrared in a separated telescope interferometer. Earlier aperture-masking observations with the Keck-I telescope provide strong evidence that dust-formation in late-type WC stars are a result of wind-wind collision in short-period binaries.Our program with the Keck interferometer seeks to further examine this paradigm at much higher resolution. We have spatially resolved the binary in the prototypical dusty WC type star WR 140. WR 137, another episodic dust-producing star, has been partially resolved for the first time, providing the first direct clue to its possible binary nature.We also include WN stars in our sample to investigate circumstellar dust in this other main sub-type of WRs. We have been unable to resolve any of these, indicating a lack of extended dust.Complementary observations using the MIDI instrument on the VLTI in the mid-infrared are presented in another contribution to this workshop.

The RECONS Hunt for Intriguing Binaries in the Solar Neighborhood

NASA Astrophysics Data System (ADS)

Bean, J. L.; Henry, T. J.; Jao, W. C.; Subasavage, J. P.

2001-12-01

As part of an effort to characterize the Sun's neighbors, photometric research was carried out on two samples of low-mass stars known or suspected to lie within 25 parsecs of the Sun. Quality filtered optical photometric data (UBVRI) from published research were merged with recently released infrared data (JHK) from the Two Micron All Sky Survey (2MASS) to create comprehensive long baseline V-I or V-K colors for more than 1400 stars. These were then combined with parallaxes from the NStars Database to create color-absolute magnitude diagrams. The results of this research include increasing the breadth of the NStars Database by adding photometric data for over 1400 stars, and identifying intriguing multiple systems (close spectroscopic binaries, BY Dra types, RS CVn systems) as well as white dwarfs and evolved stars in the solar neighborhood. More than two dozen objects have been identified as probable new multiple systems from their positions above the main sequence. Additional investigations for these intriguing systems are planned, including observations made with the GSU CHARA Array to resolve very close binary systems. This research is a continuation of the work done by RECONS (Research Consortium on Nearby Stars) based at Georgia Sate U., Johns Hopkins U., and U. Virginia, and NASA's Nearby Stars Project (NStars).

Stellar Population Synthesis of Star-forming Clumps in Galaxy Pairs and Non-interacting Spiral Galaxies

NASA Astrophysics Data System (ADS)

Zaragoza-Cardiel, Javier; Smith, Beverly J.; Rosado, Margarita; Beckman, John E.; Bitsakis, Theodoros; Camps-Fariña, Artemi; Font, Joan; Cox, Isaiah S.

2018-02-01

We have identified 1027 star-forming complexes in a sample of 46 galaxies from the Spirals, Bridges, and Tails (SB&T) sample of interacting galaxies, and 693 star-forming complexes in a sample of 38 non-interacting spiral (NIS) galaxies in 8 μm observations from the Spitzer Infrared Array Camera. We have used archival multi-wavelength UV-to IR observations to fit the observed spectral energy distribution of our clumps with the Code Investigating GALaxy Emission using a double exponentially declined star formation history. We derive the star formation rates (SFRs), stellar masses, ages and fractions of the most recent burst, dust attenuation, and fractional emission due to an active galactic nucleus for these clumps. The resolved star formation main sequence holds on 2.5 kpc scales, although it does not hold on 1 kpc scales. We analyzed the relation between SFR, stellar mass, and age of the recent burst in the SB&T and NIS samples, and we found that the SFR per stellar mass is higher in the SB&T galaxies, and the clumps are younger in the galaxy pairs. We analyzed the SFR radial profile and found that the SFR is enhanced through the disk and in the tidal features relative to normal spirals.

Why Are Galaxies So Smooth?

NASA Image and Video Library

2009-04-30

This image from NASA's Spitzer Space Telescope shows the spiral galaxy NGC 2841, located about 46 million light-years from Earth in the constellation Ursa Major. The galaxy is helping astronomers solve one of the oldest puzzles in astronomy: Why do galaxies look so smooth, with stars sprinkled evenly throughout? An international team of astronomers has discovered that rivers of young stars flow from their hot, dense stellar nurseries, dispersing out to form large, smooth distributions. This image is a composite of three different wavelengths from Spitzer's infrared array camera. The shortest wavelengths are displayed inblue, and mostly show the older stars in NGC 2841, as well as foreground stars in our own Milky Way galaxy. The cooler areas are highlighted in red, and show the dusty, gaseous regions of the galaxy. Blue shows infrared light of 3.6 microns, green represents 4.5-micron light and red, 8.0-micron light. The contribution from starlight measured at 3.6 microns has been subtracted from the 8.0-micron data to enhance the visibility of the dust features.The shortest wavelengths are displayed inblue, and mostly show the older stars in NGC 2841, as well as foreground stars in our own Milky Way galaxy. http://photojournal.jpl.nasa.gov/catalog/PIA12001

Revolutionizing Our Understanding of AGN Feedback and its Importance to Galaxy Evolution in the Era of the Next Generation Very Large Array

NASA Astrophysics Data System (ADS)

Nyland, Kristina; Harwood, Jeremy; Jagannathan, Preshanth; Mukherjee, Dipanjan; Lacy, Mark; Morabito, Leah; Maksym, W. Peter; Kimball, Amy; Alatalo, Katherine; Bicknell, Geoff; Patil, Pallavi; Emonts, Bjorn

2018-01-01

Energetic feedback by Active Galactic Nuclei (AGNs) likely plays an important evolutionary role in the regulation of star formation (SF) on galactic scales. However, the effects of this feedback under different host galaxy conditions and environments remain unknown due to the scarcity of observational examples of this process in action given the limitations of current telescopes. The Next Generation Very Large Array (ngVLA) will serve as a transformational new tool in our understanding of how radio jets affect their surroundings. Current plans for the ngVLA consist of an array of 214 18m antennas with baselines out to 500 km operating over a frequency range of 1-115 GHz. By combining deep, broadband continuum data with measurements of the atomic and/or molecular gas content and kinematics, the ngVLA will quantify the energetic impact of radio jets hosted by gas-rich galaxies as the jets interact with the star-forming gas reservoirs of their hosts. Here, we evaluate the progress in our understanding of AGN feedback and its connection to galaxy evolution that may be accomplished with the unique capabilities of the ngVLA. Our analysis includes simulations of ngVLA observations of redshifted analogs of nearby AGNs with diverse properties, along with examples of opportunities for multiwavelength synergies with current and future next-generation instruments that are currently under development.

S193 radiometer brightness temperature precision/accuracy for SL2 and SL3

NASA Technical Reports Server (NTRS)

Pounds, D. J.; Krishen, K.

1975-01-01

The precision and accuracy with which the S193 radiometer measured the brightness temperature of ground scenes is investigated. Estimates were derived from data collected during Skylab missions. Homogeneous ground sites were selected and S193 radiometer brightness temperature data analyzed. The precision was expressed as the standard deviation of the radiometer acquired brightness temperature. Precision was determined to be 2.40 K or better depending on mode and target temperature.

NGS2: a focal plane array upgrade for the GeMS multiple tip-tilt wavefront sensor

NASA Astrophysics Data System (ADS)

Rigaut, François; Price, Ian; d'Orgeville, Céline; Bennet, Francis; Herrald, Nick; Paulin, Nicolas; Uhlendorf, Kristina; Garrel, Vincent; Sivo, Gaetano; Montes, Vanessa; Trujillo, Chad

2016-07-01

NGS2 is an upgrade for the multi-natural guide star tip-tilt & plate scale wavefront sensor for GeMS (Gemini Multi-Conjugate Adaptive Optics system). It uses a single Nüvü HNü-512 Electron-Multiplied CCD array that spans the entire GeMS wavefront sensor focal plane. Multiple small regions-of-interest are used to enable frame rates up to 800Hz. This set up will improve the optical throughput with respect to the current wavefront sensor, as well as streamline acquisition and allow for distortion compensation.

Aquarius's Instrument Science Data System (ISDS) Automated to Acquire, Process, Trend Data and Produce Radiometric System Assessment Reports

NASA Technical Reports Server (NTRS)

2008-01-01

The Aquarius Radiometer, a subsystem of the Aquarius Instrument required a data acquisition ground system to support calibration and radiometer performance assessment. To support calibration and compose performance assessments, we developed an automated system which uploaded raw data to a ftp server and saved raw and processed data to a database. This paper details the overall functionalities of the Aquarius Instrument Science Data System (ISDS) and the individual electrical ground support equipment (EGSE) which produced data files that were infused into the ISDS. Real time EGSEs include an ICDS Simulator, Calibration GSE, Labview controlled power supply, and a chamber data acquisition system. ICDS Simulator serves as a test conductor primary workstation, collecting radiometer housekeeping (HK) and science data and passing commands and HK telemetry collection request to the radiometer. Calibration GSE (Radiometer Active Test Source) provides source choice from multiple targets for the radiometer external calibration. Power Supply GSE, controlled by labview, provides real time voltage and current monitoring of the radiometer. And finally the chamber data acquisition system produces data reflecting chamber vacuum pressure, thermistor temperatures, AVG and watts. Each GSE system produce text based data files every two to six minutes and automatically copies the data files to the Central Archiver PC. The Archiver PC stores the data files, schedules automated uploads of these files to an external FTP server, and accepts request to copy all data files to the ISDS for offline data processing and analysis. Aquarius Radiometer ISDS contains PHP and MATLab programs to parse, process and save all data to a MySQL database. Analysis tools (MATLab programs) in the ISDS system are capable of displaying radiometer science, telemetry and auxiliary data in near real time as well as performing data analysis and producing automated performance assessment reports of the Aquarius Radiometer.

GPM Plans for Radiometer Intercalibration

NASA Technical Reports Server (NTRS)

Stocker, Erich Franz; Stout, John; Chou, Joyce

2011-01-01

The international Global Precipitation Measurement (GPM) mission led by NASA and JAXA is planned as a multi-radiometer constellation mission. A key mission component is the ability to intercalibrate the Tb from the partner constellation radiometers and create inter-calibrated, mission consistent Tc. One of the enabling strategies for this approach is the launching of a joint NASA/JAXA core satellite which contains a JAXA/NICT provided dual precipitation radar and a NASA provided Microwave Imaging passive radiometer. The observations from these instruments on the core satellite provide the opportunity to develop a transfer reference standard that can then be applied across the partner provided constellation radiometers that enables the creation of mission consistent brightness temperatures. The other aspect of the strategy is the development of a community consensus intercalibration algorithm that will be applied to the Tb observations from partner radiometers and create the best calibrated Tc. Also described is the development of the framework in which the inter-calibration is included in the final algorithm. A part of the latter effort has been the development of a generic, logical structure which can be applied across radiometer types and which guarantees the user community that key information for using Tc properly is recorded. Key

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

Harp, G. R.; Richards, Jon; Tarter, Jill C.

We report radio SETI observations on a large number of known exoplanets and other nearby star systems using the Allen Telescope Array (ATA). Observations were made over about 19000 hr from 2009 May to 2015 December. This search focused on narrowband radio signals from a set totaling 9293 stars, including 2015 exoplanet stars and Kepler objects of interest and an additional 65 whose planets may be close to their habitable zones. The ATA observations were made using multiple synthesized beams and an anticoincidence filter to help identify terrestrial radio interference. Stars were observed over frequencies from 1 to 9 GHzmore » in multiple bands that avoid strong terrestrial communication frequencies. Data were processed in near-real time for narrowband (0.7–100 Hz) continuous and pulsed signals with transmitter/receiver relative accelerations from −0.3 to 0.3 m s{sup −2}. A total of 1.9 × 10{sup 8} unique signals requiring immediate follow-up were detected in observations covering more than 8 × 10{sup 6} star-MHz. We detected no persistent signals from extraterrestrial technology exceeding our frequency-dependent sensitivity threshold of 180–310 × 10{sup −26} W m{sup −2}.« less

Dark gamma-ray bursts

NASA Astrophysics Data System (ADS)

Brdar, Vedran; Kopp, Joachim; Liu, Jia

2017-03-01

Many theories of dark matter (DM) predict that DM particles can be captured by stars via scattering on ordinary matter. They subsequently condense into a DM core close to the center of the star and eventually annihilate. In this work, we trace DM capture and annihilation rates throughout the life of a massive star and show that this evolution culminates in an intense annihilation burst coincident with the death of the star in a core collapse supernova. The reason is that, along with the stellar interior, also its DM core heats up and contracts, so that the DM density increases rapidly during the final stages of stellar evolution. We argue that, counterintuitively, the annihilation burst is more intense if DM annihilation is a p -wave process than for s -wave annihilation because in the former case, more DM particles survive until the supernova. If among the DM annihilation products are particles like dark photons that can escape the exploding star and decay to standard model particles later, the annihilation burst results in a flash of gamma rays accompanying the supernova. For a galactic supernova, this "dark gamma-ray burst" may be observable in the Čerenkov Telescope Array.

NuSTAR Observations of X-Ray Flares from Young Stellar Objects

NASA Astrophysics Data System (ADS)

Vievering, Juliana; Glesener, Lindsay; Grefenstette, Brian; Smith, David

2018-01-01

Young stellar objects (YSOs), which tend to flare more frequently and at higher temperatures than what is typically observed on Sun-like stars, are excellent targets for studying the physical processes behind large flaring events. In the hard x-ray regime, radiation can penetrate through dense circumstellar material, and it is possible to measure thermal emission from hot plasma and to search for nonthermal emission from accelerated particles, which are key components for understanding the nature of energy release in these flares. Additionally, high-energy x-ray emission can ionize material in the disk, which may have implications for planet formation. To investigate hard x-ray emission from YSOs, three 50ks observations of a star-forming region called rho Ophiuchi have been taken with the Nuclear Spectroscopic Telescope Array (NuSTAR). Through use of direct focusing optics, NuSTAR provides unprecedented sensitivity in the hard x-ray regime, making these YSO observations the first of their kind. Multiple stellar flares have been identified in the data set; here we present the current spectral and timing analyses of the brightest of the these events, exploring the way energy is released as well as the effects of these large flares on the surrounding environment.

The faint young Sun paradox: an observational test of an alternative solar model

NASA Technical Reports Server (NTRS)

Gaidos, E. J.; Gudel, M.; Blake, G. A.

2000-01-01

We report the results of deep observations at radio (3.6 cm) wavelengths of the nearby solar-type star pi 01 Ursa Majoris with the Very Large Array (VLA) intended to test an alternative theory of solar luminosity evolution. The standard model predicts a solar luminosity only 75% of the present value and surface temperatures below freezing on Earth and Mars at 4 Ga, seemingly in conflict with geologic evidence for liquid water on these planets. An alternative model invokes a compensatory mass loss through a declining solar wind that results in a more consistent early luminosity. The free-free emission from an enhanced wind around nearby young Sun-like stars should be detectable at microwave frequencies. Our observations of pi 01 UMa, a 300 million year-old solar-mass star, place an upper limit on the mass loss rate of 4-5 x 10(-11) M(solar) yr-1. Total mass loss from such a star over 4 Gyr would be less than 6%. If this star is indeed an analog of the early Sun, it casts doubt on the alternative model as a solution to the faint young Sun paradox, particularly for Mars.

GEOSTAR-II: A Prototype Water Vapor Imager/Sounder for the Path Mission

NASA Technical Reports Server (NTRS)

Gaier, Todd; Lambrigtsen, Bjorn; Kangaslahti, Pekka; Lim, Boon; Tanner, Alan; Harding, Dennis; Owen, Heather; Soria, Mary; ODwyer, Ian; Ruf, Christopher;

CMOS Active-Pixel Image Sensor With Intensity-Driven Readout

NASA Technical Reports Server (NTRS)

Langenbacher, Harry T.; Fossum, Eric R.; Kemeny, Sabrina

1996-01-01

Proposed complementary metal oxide/semiconductor (CMOS) integrated-circuit image sensor automatically provides readouts from pixels in order of decreasing illumination intensity. Sensor operated in integration mode. Particularly useful in number of image-sensing tasks, including diffractive laser range-finding, three-dimensional imaging, event-driven readout of sparse sensor arrays, and star tracking.

Improving MWA/HERA Calibration Using Extended Radio Source Models

NASA Astrophysics Data System (ADS)

Cunningham, Devin; Tasker, Nicholas; University of Washington EoR Imaging Team

2018-01-01

The formation of the first stars and galaxies in the universe is among the greatest mysteries in astrophysics. Using special purpose radio interferometers, it is possible to detect the faint 21 cm radio line emitted by neutral hydrogen in order to characterize the Epoch of Reionization (EoR) and the formation of the first stars and galaxies. We create better models of extended radio sources by reducing component number of deconvolved Murchison Widefield Array (MWA) data by up to 90%, while preserving real structure and flux information. This real structure is confirmed by comparisons to observations of the same extended radio sources from the TIFR GMRT Sky Survey (TGSS) and NRAO VLA Sky Survey (NVSS), which detect at a similar frequency range as the MWA. These sophisticated data reduction techniques not only offer improvements to the calibration of the MWA, but also hold applications for the future sky-based calibration of the Hydrogen Epoch of Reionization Array (HERA). This has the potential to reduce noise in the power spectra from these instruments, and consequently provide a deeper view into the window of EoR.

Multi-messenger studies of compact binary mergers in the in the ngVLA era

NASA Astrophysics Data System (ADS)

Corsi, Alessandra

2018-01-01

We explore some of the scientific opportunities that the next generation Very Large Array (ngVLA) will open in the field of multi-messenger time-domain astronomy. We focus on compact binary mergers, golden astrophysical targets of ground-based gravitational wave (GW) detectors such as advanced LIGO. A decade from now, a large number of these mergers is likely to be discovered by a world-wide network of GW detectors. We discuss how a radio array with 10 times the sensitivity of the current Karl G. Jansky VLA and 10 times the resolution, would enable resolved radio continuum studies of binary merger hosts, probing regions of the galaxy undergoing star formation (which can be heavily obscured by dust and gas), AGN components, and mapping the offset distribution of the mergers with respect to the host galaxy light. For compact binary mergers containing at least one neutron star (NS), from which electromagnetic counterparts are expected to exist, we show how the ngVLA would enable direct size measurements of the relativistic merger ejecta and probe, for the first time directly, their dynamics.

Improved charge injection device and a focal plane interface electronics board for stellar tracking

NASA Technical Reports Server (NTRS)

Michon, G. J.; Burke, H. K.

1984-01-01

An improved Charge Injection Device (CID) stellar tracking sensor and an operating sensor in a control/readout electronics board were developed. The sensor consists of a shift register scanned, 256x256 CID array organized for readout of 4x4 subarrays. The 4x4 subarrays can be positioned anywhere within the 256x256 array with a 2 pixel resolution. This allows continuous tracking of a number of stars simultaneously since nine pixels (3x3) centered on any star can always be read out. Organization and operation of this sensor and the improvements in design and semiconductor processing are described. A hermetic package incorporating an internal thermoelectric cooler assembled using low temperature solders was developed. The electronics board, which contains the sensor drivers, amplifiers, sample hold circuits, multiplexer, analog to digital converter, and the sensor temperature control circuits, is also described. Packaged sensors were evaluated for readout efficiency, spectral quantum efficiency, temporal noise, fixed pattern noise, and dark current. Eight sensors along with two tracker electronics boards were completed, evaluated, and delivered.

Protostellar Outflows Mapped with ALMA and Techniques to Include Short Spacings

NASA Astrophysics Data System (ADS)

Plunkett, Adele

2018-01-01

Protostellar outflows are early signs of star formation, yet in cluster environments - common sites of star formation - their role and interaction with surrounding gas are complicated. Protostellar outflows are interesting and complex because they connect protostars (scales 10s au) to the surrounding gas environment (few pc), and their morphology constrains launching and/or accretion modes. A complete outflow study must use observing methods that recover several orders of magnitude of spatial scales, ideally with sub-arcsecond resolution and mapping over a few parsecs. ALMA provides high-resolution observations of outflows, and in some cases outflows have been mapped in clusters. Combining with observations using the Total Power array is possible, but challenging, and a large single dish telescope providing more overlap in uv space is advantageous. In this presentation I show protostellar outflows observed with ALMA using 12m, 7m, and To tal Power arrays. With a new CASA tool TP2VIS we create total power ``visibility'' data and perform joint imaging and deconvolution of interferometry and single dish data. TP2VIS will ultimately provide synergy between ALMA and AtLAST data.

Scientists Track Collision of Powerful Stellar Winds

NASA Astrophysics Data System (ADS)

2005-04-01

Astronomers using the National Science Foundation's Very Long Baseline Array (VLBA) radio telescope have tracked the motion of a violent region where the powerful winds of two giant stars slam into each other. The collision region moves as the stars, part of a binary pair, orbit each other, and the precise measurement of its motion was the key to unlocking vital new information about the stars and their winds. WR 140 Image Sequence Motion of Wind Collision Region Graphic superimposes VLBA images of wind collision region on diagram of orbit of Wolf-Rayet (WR) star and its giant (O) companion. Click on image for larger version (412K) CREDIT: Dougherty et al., NRAO/AUI/NSF In Motion: Shockwave File Animated Gif File AVI file Both stars are much more massive than the Sun -- one about 20 times the mass of the Sun and the other about 50 times the Sun's mass. The 20-solar-mass star is a type called a Wolf-Rayet star, characterized by a very strong wind of particles propelled outward from its surface. The more massive star also has a strong outward wind, but one less intense than that of the Wolf-Rayet star. The two stars, part of a system named WR 140, circle each other in an elliptical orbit roughly the size of our Solar System. "The spectacular feature of this system is the region where the stars' winds collide, producing bright radio emission. We have been able to track this collision region as it moves with the orbits of the stars," said Sean Dougherty, an astronomer at the Herzberg Institute for Astrophysics in Canada. Dougherty and his colleagues presented their findings in the April 10 edition of the Astrophysical Journal. The supersharp radio "vision" of the continent-wide VLBA allowed the scientists to measure the motion of the wind collision region and then to determine the details of the stars' orbits and an accurate distance to the system. "Our new calculations of the orbital details and the distance are vitally important to understanding the nature of these Wolf-Rayet stars and of the wind-collision region," Dougherty said. The stars in WR 140 complete an orbital cycle in 7.9 years. The astronomers tracked the system for a year and a half, noting dramatic changes in the wind collision region. "People have worked out theoretical models for these collision regions, but the models don't seem to fit what our observations have shown," said Mark Claussen, of the National Radio Astronomy Observatory in Socorro, New Mexico. "The new data on this system should provide the theorists with much better information for refining their models of how Wolf-Rayet stars evolve and how wind-collision regions work," Claussen added. The scientists watched the changes in the stellar system as the star's orbits carried them in paths that bring them nearly as close to each other as Mars is to the Sun and as far as Neptune is from the Sun. Their detailed analysis gave them new information on the Wolf-Rayet star's strong wind. At some points in the orbit, the wind collision region strongly emitted radio waves, and at other points, the scientists could not detect the collison region. Wolf-Rayet stars are giant stars nearing the time when they will explode as supernovae. "No other telescope in the world can see the details revealed by the VLBA," Claussen said. "This unmatched ability allowed us to determine the masses and other properties of the stars, and will help us answer some basic questions about the nature of Wolf-Rayet stars and how they develop." he added. The astronomers plan to continue observing WR 140 to follow the system's changes as the two massive stars continue to circle each other. Dougherty and Claussen worked with Anthony Beasley of the Atacama Large Millimeter Array office, Ashley Zauderer of the University of Maryland and Nick Bolingbroke of the University of Victoria, British Columbia. The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

Techniques for computing regional radiant emittances of the earth-atmosphere system from observations by wide-angle satellite radiometers, phase 3

NASA Technical Reports Server (NTRS)

Pina, J. F.; House, F. B.

1975-01-01

Radiometers on earth orbiting satellites measure the exchange of radiant energy between the earth-atmosphere (E-A) system and space at observation points in space external to the E-A system. Observations by wideangle, spherical and flat radiometers are analyzed and interpreted with regard to the general problem of the earth energy budget (EEB) and to the problem of determining the energy budget of regions smaller than the field of view (FOV) of these radiometers.

Infrared radiometer for measuring thermophysical properties of wind tunnel models

NASA Technical Reports Server (NTRS)

Corwin, R. R.; Moorman, S. L.; Becker, E. C.

1978-01-01

An infrared radiometer is described which was developed to measure temperature rises of wind tunnel models undergoing transient heating over a temperature range of -17.8 C to 260 C. This radiometer interfaces directly with a system which measures the effective thermophysical property square root of rho ck. It has an output temperature fluctuation of 0.26 C at low temperatures and 0.07 C at high temperatures, and the output frequency response of the radiometer is from dc to 400 hertz.

The violent interstellar medium in Messier 31

NASA Technical Reports Server (NTRS)

Brinks, Elias; Braun, Robert; Unger, Stephen W.

1990-01-01

Taurus observations in the line of H alpha and Very Large Array (VLA) HI mapping of the HII complex No. 722 in M31, reveal what seems to be a spherical cavity 330 pc in diameter blown out by a stellar association of over 20(exp 6) years old. Evidence of induced star formation which was initiated less than 5(exp 6) years ago is present in the form of bright HII emission and numerous O, B and Wolf-Rayet stars which are found within the shell surrounding the cavity. The energy necessary to create the HI shell is estimated to be about 5(exp 51) erg.

KSC-2010-5266

NASA Image and Video Library

2010-09-16

VANDENBERG AIR FORCE BASE, Calif. -- At Vandenberg Air Force Base in California, the third stage of the Pegasus XL rocket that will launch the Nuclear Spectroscopic Telescope Array (NuSTAR) to orbit arrives at Building 1555 for processing. After the rocket and spacecraft are processed at Vandenberg, they will be shipped to the Ronald Reagan Ballistic Missile Defense Test Site located at the Pacific Ocean's Kwajalein Atoll for launch. The high-energy X-ray telescope will conduct a census for black holes, map radioactive material in young supernovae remnants, and study the origins of cosmic rays and the extreme physics around collapsed stars. Photo credit: NASA/Dan Liberotti, VAFB

KSC-2010-5269

NASA Image and Video Library

2010-09-16

VANDENBERG AIR FORCE BASE, Calif. -- At Vandenberg Air Force Base in California, the third stage of the Pegasus XL rocket that will launch the Nuclear Spectroscopic Telescope Array (NuSTAR) to orbit is moved onto a jackable rail for processing in Building 1555. After the rocket and spacecraft are processed at Vandenberg, they will be shipped to the Ronald Reagan Ballistic Missile Defense Test Site located at the Pacific Ocean’s Kwajalein Atoll for launch. The high-energy X-ray telescope will conduct a census for black holes, map radioactive material in young supernovae remnants, and study the origins of cosmic rays and the extreme physics around collapsed stars. Photo credit: NASA/Dan Liberotti, VAFB

KSC-2010-5268

NASA Image and Video Library

2010-09-16

VANDENBERG AIR FORCE BASE, Calif. -- At Vandenberg Air Force Base in California, the third stage of the Pegasus XL rocket that will launch the Nuclear Spectroscopic Telescope Array (NuSTAR) to orbit is offloaded for processing in Building 1555. After the rocket and spacecraft are processed at Vandenberg, they will be shipped to the Ronald Reagan Ballistic Missile Defense Test Site located at the Pacific Ocean’s Kwajalein Atoll for launch. The high-energy X-ray telescope will conduct a census for black holes, map radioactive material in young supernovae remnants, and study the origins of cosmic rays and the extreme physics around collapsed stars. Photo credit: NASA/Dan Liberotti, VAFB

KSC-2010-4695

NASA Image and Video Library

2010-09-16

VANDENBERG AIR FORCE BASE, Calif. -- At Vandenberg Air Force Base in California, the first stage of the Pegasus XL rocket that will launch the Nuclear Spectroscopic Telescope Array (NuSTAR) to orbit is offloaded for processing in Building 1555. After the rocket and spacecraft are processed at Vandenberg, they will be shipped to the Ronald Reagan Ballistic Missile Defense Test Site located at the Pacific Ocean’s Kwajalein Atoll for launch. The high-energy X-ray telescope will conduct a census for black holes, map radioactive material in young supernovae remnants, and study the origins of cosmic rays and the extreme physics around collapsed stars. Photo credit: NASA/Randy Beaudoin, VAFB

KSC-2010-4691

NASA Image and Video Library

2010-09-16

VANDENBERG AIR FORCE BASE, Calif. -- At Vandenberg Air Force Base in California, the third stage of the Pegasus XL rocket that will launch the Nuclear Spectroscopic Telescope Array (NuSTAR) to orbit is offloaded for processing in Building 1555. After the rocket and spacecraft are processed at Vandenberg, they will be shipped to the Ronald Reagan Ballistic Missile Defense Test Site located at the Pacific Ocean’s Kwajalein Atoll for launch. The high-energy X-ray telescope will conduct a census for black holes, map radioactive material in young supernovae remnants, and study the origins of cosmic rays and the extreme physics around collapsed stars. Photo credit: NASA/Randy Beaudoin, VAFB

KSC-2010-5270

NASA Image and Video Library

2010-09-16

VANDENBERG AIR FORCE BASE, Calif. -- At Vandenberg Air Force Base in California, the third stage of the Pegasus XL rocket that will launch the Nuclear Spectroscopic Telescope Array (NuSTAR) to orbit is moved onto a jackable rail for processing in Building 1555. After the rocket and spacecraft are processed at Vandenberg, they will be shipped to the Ronald Reagan Ballistic Missile Defense Test Site located at the Pacific Ocean’s Kwajalein Atoll for launch. The high-energy X-ray telescope will conduct a census for black holes, map radioactive material in young supernovae remnants, and study the origins of cosmic rays and the extreme physics around collapsed stars. Photo credit: NASA/Dan Liberotti, VAFB

KSC-2010-4694

NASA Image and Video Library

2010-09-16

VANDENBERG AIR FORCE BASE, Calif. -- At Vandenberg Air Force Base in California, the second stage of the Pegasus XL rocket that will launch the Nuclear Spectroscopic Telescope Array (NuSTAR) to orbit is moved to a stationary rail in Building 1555 for processing. After the rocket and spacecraft are processed at Vandenberg, they will be shipped to the Ronald Reagan Ballistic Missile Defense Test Site located at the Pacific Ocean’s Kwajalein Atoll for launch. The high-energy X-ray telescope will conduct a census for black holes, map radioactive material in young supernovae remnants, and study the origins of cosmic rays and the extreme physics around collapsed stars. Photo credit: NASA/Randy Beaudoin, VAFB

KSC-2010-4693

NASA Image and Video Library

2010-09-16

VANDENBERG AIR FORCE BASE, Calif. -- At Vandenberg Air Force Base in California, the second stage of the Pegasus XL rocket that will launch the Nuclear Spectroscopic Telescope Array (NuSTAR) to orbit is moved to a stationary rail in Building 1555 for processing. After the rocket and spacecraft are processed at Vandenberg, they will be shipped to the Ronald Reagan Ballistic Missile Defense Test Site located at the Pacific Ocean’s Kwajalein Atoll for launch. The high-energy X-ray telescope will conduct a census for black holes, map radioactive material in young supernovae remnants, and study the origins of cosmic rays and the extreme physics around collapsed stars. Photo credit: NASA/Randy Beaudoin, VAFB

KSC-2010-5306

NASA Image and Video Library

2010-10-16

VANDENBERG AIR FORCE BASE, Calif. -- At Vandenberg Air Force Base in California, the Pegasus XL rocket that will launch the Nuclear Spectroscopic Telescope Array (NuSTAR) to orbit is coming together in the west high bay of Building 1555. After the rocket and spacecraft are processed at Vandenberg, they will be shipped to the Ronald Reagan Ballistic Missile Defense Test Site located at the Pacific Ocean’s Kwajalein Atoll for launch. The high-energy X-ray telescope will conduct a census for black holes, map radioactive material in young supernovae remnants, and study the origins of cosmic rays and the extreme physics around collapsed stars. Photo credit: NASA/Randy Beaudoin, VAFB

KSC-2010-5267

NASA Image and Video Library

2010-09-16

VANDENBERG AIR FORCE BASE, Calif. -- At Vandenberg Air Force Base in California, the third stage of the Pegasus XL rocket that will launch the Nuclear Spectroscopic Telescope Array (NuSTAR) to orbit arrives at Building 1555 for processing. After the rocket and spacecraft are processed at Vandenberg, they will be shipped to the Ronald Reagan Ballistic Missile Defense Test Site located at the Pacific Ocean’s Kwajalein Atoll for launch. The high-energy X-ray telescope will conduct a census for black holes, map radioactive material in young supernovae remnants, and study the origins of cosmic rays and the extreme physics around collapsed stars. Photo credit: NASA/Dan Liberotti, VAFB

KSC-2010-4690

NASA Image and Video Library

2010-09-16

VANDENBERG AIR FORCE BASE, Calif. -- At Vandenberg Air Force Base in California, the third stage of the Pegasus XL rocket that will launch the Nuclear Spectroscopic Telescope Array (NuSTAR) to orbit is offloaded for processing in Building 1555. After the rocket and spacecraft are processed at Vandenberg, they will be shipped to the Ronald Reagan Ballistic Missile Defense Test Site located at the Pacific Ocean’s Kwajalein Atoll for launch. The high-energy X-ray telescope will conduct a census for black holes, map radioactive material in young supernovae remnants, and study the origins of cosmic rays and the extreme physics around collapsed stars. Photo credit: NASA/Randy Beaudoin, VAFB

Night Sky Weather Monitoring System Using Fish-Eye CCD

NASA Astrophysics Data System (ADS)

Tomida, Takayuki; Saito, Yasunori; Nakamura, Ryo; Yamazaki, Katsuya

Telescope Array (TA) is international joint experiment observing ultra-high energy cosmic rays. TA employs fluorescence detection technique to observe cosmic rays. In this technique, tho existence of cloud significantly affects quality of data. Therefore, cloud monitoring provides important information. We are developing two new methods for evaluating night sky weather with pictures taken by charge-coupled device (CCD) camera. One is evaluating the amount of cloud with pixels brightness. The other is counting the number of stars with contour detection technique. The results of these methods show clear correlation, and we concluded both the analyses are reasonable methods for weather monitoring. We discuss reliability of the star counting method.

Digital Beamforming Scatterometer

NASA Technical Reports Server (NTRS)

Rincon, Rafael F.; Vega, Manuel; Kman, Luko; Buenfil, Manuel; Geist, Alessandro; Hillard, Larry; Racette, Paul

2009-01-01

This paper discusses scatterometer measurements collected with multi-mode Digital Beamforming Synthetic Aperture Radar (DBSAR) during the SMAP-VEX 2008 campaign. The 2008 SMAP Validation Experiment was conducted to address a number of specific questions related to the soil moisture retrieval algorithms. SMAP-VEX 2008 consisted on a series of aircraft-based.flights conducted on the Eastern Shore of Maryland and Delaware in the fall of 2008. Several other instruments participated in the campaign including the Passive Active L-Band System (PALS), the Marshall Airborne Polarimetric Imaging Radiometer (MAPIR), and the Global Positioning System Reflectometer (GPSR). This campaign was the first SMAP Validation Experiment. DBSAR is a multimode radar system developed at NASA/Goddard Space Flight Center that combines state-of-the-art radar technologies, on-board processing, and advances in signal processing techniques in order to enable new remote sensing capabilities applicable to Earth science and planetary applications [l]. The instrument can be configured to operate in scatterometer, Synthetic Aperture Radar (SAR), or altimeter mode. The system builds upon the L-band Imaging Scatterometer (LIS) developed as part of the RadSTAR program. The radar is a phased array system designed to fly on the NASA P3 aircraft. The instrument consists of a programmable waveform generator, eight transmit/receive (T/R) channels, a microstrip antenna, and a reconfigurable data acquisition and processor system. Each transmit channel incorporates a digital attenuator, and digital phase shifter that enables amplitude and phase modulation on transmit. The attenuators, phase shifters, and calibration switches are digitally controlled by the radar control card (RCC) on a pulse by pulse basis. The antenna is a corporate fed microstrip patch-array centered at 1.26 GHz with a 20 MHz bandwidth. Although only one feed is used with the present configuration, a provision was made for separate corporate feeds for vertical and horizontal polarization. System upgrades to dual polarization are currently under way. The DBSAR processor is a reconfigurable data acquisition and processor system capable of real-time, high-speed data processing. DBSAR uses an FPGA-based architecture to implement digitally down-conversion, in-phase and quadrature (I/Q) demodulation, and subsequent radar specific algorithms. The core of the processor board consists of an analog-to-digital (AID) section, three Altera Stratix field programmable gate arrays (FPGAs), an ARM microcontroller, several memory devices, and an Ethernet interface. The processor also interfaces with a navigation board consisting of a GPS and a MEMS gyro. The processor has been configured to operate in scatterometer, Synthetic Aperture Radar (SAR), and altimeter modes. All the modes are based on digital beamforming which is a digital process that generates the far-field beam patterns at various scan angles from voltages sampled in the antenna array. This technique allows steering the received beam and controlling its beam-width and side-lobe. Several beamforming techniques can be implemented each characterized by unique strengths and weaknesses, and each applicable to different measurement scenarios. In Scatterometer mode, the radar is capable to.generate a wide beam or scan a narrow beam on transmit, and to steer the received beam on processing while controlling its beamwidth and side-lobe level. Table I lists some important radar characteristics

CMOS VLSI Active-Pixel Sensor for Tracking

NASA Technical Reports Server (NTRS)

Pain, Bedabrata; Sun, Chao; Yang, Guang; Heynssens, Julie

2004-01-01

An architecture for a proposed active-pixel sensor (APS) and a design to implement the architecture in a complementary metal oxide semiconductor (CMOS) very-large-scale integrated (VLSI) circuit provide for some advanced features that are expected to be especially desirable for tracking pointlike features of stars. The architecture would also make this APS suitable for robotic- vision and general pointing and tracking applications. CMOS imagers in general are well suited for pointing and tracking because they can be configured for random access to selected pixels and to provide readout from windows of interest within their fields of view. However, until now, the architectures of CMOS imagers have not supported multiwindow operation or low-noise data collection. Moreover, smearing and motion artifacts in collected images have made prior CMOS imagers unsuitable for tracking applications. The proposed CMOS imager (see figure) would include an array of 1,024 by 1,024 pixels containing high-performance photodiode-based APS circuitry. The pixel pitch would be 9 m. The operations of the pixel circuits would be sequenced and otherwise controlled by an on-chip timing and control block, which would enable the collection of image data, during a single frame period, from either the full frame (that is, all 1,024 1,024 pixels) or from within as many as 8 different arbitrarily placed windows as large as 8 by 8 pixels each. A typical prior CMOS APS operates in a row-at-a-time ( grolling-shutter h) readout mode, which gives rise to exposure skew. In contrast, the proposed APS would operate in a sample-first/readlater mode, suppressing rolling-shutter effects. In this mode, the analog readout signals from the pixels corresponding to the windows of the interest (which windows, in the star-tracking application, would presumably contain guide stars) would be sampled rapidly by routing them through a programmable diagonal switch array to an on-chip parallel analog memory array. The diagonal-switch and memory addresses would be generated by the on-chip controller. The memory array would be large enough to hold differential signals acquired from all 8 windows during a frame period. Following the rapid sampling from all the windows, the contents of the memory array would be read out sequentially by use of a capacitive transimpedance amplifier (CTIA) at a maximum data rate of 10 MHz. This data rate is compatible with an update rate of almost 10 Hz, even in full-frame operation

Six mechanisms used on the SSM/1 radiometer

NASA Technical Reports Server (NTRS)

Ludwig, H. R.

1985-01-01

Future USAF Block 5D Defense Meteorological Satellites will carry a scanning microwave radiometer sensor (SSM/1). SSM/1 senses the emission of microwave energy and returns to earth data used to determine weather conditions, such as rainfall rates, soil moisture, and oceanic wind speed. The overall design of the SSM/1 radiometer was largely influenced by the mechanisms. The radiometer was designed to be stowed in a cavity on the existing spacecraft. The deployment of the sensor is complex due to the constraint of this cavity and the need for precision in the deployment. The radiometer will continuously rotate, instead of oscillate, creating the need for a bearing and power transfer assembly and a momentum compensation device. The six mechanisms developed for this program are described.

Geosynchronous Microwave Atmospheric Sounding Radiometer (MASR) feasibility studies. Volume 1: Management summary

NASA Technical Reports Server (NTRS)

1978-01-01

The mission of the microwave atmospheric sounding radiometer (MASR) is to collect data to aid in the observation and prediction of severe storms. The geosynchronous orbit allows the continuous atmospheric measurement needed to resolve mesoscale dynamics. The instrument may operate in conjunction with this document, Volume 1 - Management, which summarizes the highlights of final reports on both the radiometer instrument and antenna studies. The radiometer instrument summary includes a synopsis of Volume 2 - Radiometer Receiver Feasibility, including design, recommended configuration, performance estimates, and weight and power estimates. The summary of the antenna study includes a synopsis of Volume 3 - Antenna Feasibility, including preliminary design tradeoffs, performance of selected design, and details of the mechanical/thermal design.