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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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NASA NTRS1990

A plan for the development of lunar astronomy

This is a report synthesizing discussions of the Astronomy/Astrophysics Definition Team at the Lunar Science Strategy Workshop for the Exploration and Development of the moon which was held at the NASA Johnson Space Center during August 15-16, 1989. The long-term goal of lunar based astronomy is envisioned as the development of a diverse facility covering all wavelengths of the electromagnetic spectrum. This facility will build on and eventually replace the Great Observatories. The development of optical and infrared interferometry should be a principal activity, optimized by a lunar site. However, lunar observatories should evolve from simple to complex systems and should not and need not make major demands on the limited amount of manpower envisioned for the first 20 years of the lunar outpost.

Sykes, M. V.↗
NASA NTRS1990

Lunar low-frequency radio array

A simple, inexpensive experiment is proposed for the early lunar mission to make high angular resolution observations in one of the last unexplored parts of the electromagnetic spectrum. An array of nineteen simple crossed-dipole antennas will make images at frequencies below the earth's ionospheric cut-off - from about 100 kHz to 10 MHz. It would serve as a precursor to a major low-frequency telescope which would eventually be built on the back of the moon, away from terrestrial interference.

Kuiper, T. B. H.↗
NASA NTRS1990

Four lunar astronomical observatories - Concepts developed in the NASA 90-day study for the Human Exploration Initiative

A number of astrophysical observatory concepts were studied under the overall direction of the NASA Astrophysics Division in support of NASA's 90-day study of the Human Exploration Initiative. The four observatory concepts described here were investigated at JPL. In three of them, interferometric techniques would be used to acquire high resolution synthetic aperture images in several different parts of the electromagnetic spectrum: in the UV/visible near infrared; the submillimeter; and the very low frequency (1 to 30 MHz region). The fourth is a gravitational wave detector which uses laser optical interferometry to measure the strains induced by the passage of a gravitational wave. The observatory concepts reflect the constraints on lunar surface science deployment anticipated for the Human Exploration Initiative in the period 2002 through 2015.

Cutts, James A.↗
NASA NTRS1991

The great observatories for space astrophysics

The nation's strategy for astrophysics research during the rest of this century and into the next is a coordinated, multispectral examination of the universe. NASA plans to launch a family of large orbital observatories, each tuned to a different part of the electromagnetic spectrum. They are as follows: the Gamma Ray Observatory (GRO); the Advanced X Ray Astrophysics Facility (AXAF); the Hubble Space Telescope (HST); and the Space Infrared Telescope Facility (SIRTF). To complement these sensitive space telescopes, a powerful new radio observatory system is envisioned: the Very Long Baseline Array (VLBA), an intercontinental network of radio telescopes, working with radio observatories in space to perform orbiting very long baseline interferometry (OVLBI). Observing the universe across the spectrum requires different kinds of telescopes based on quite different techniques of detection. An optical telescope has little in common with a gamma ray detector; they do not look alike, nor do they operate on the same principles. No single telescope can answer all the questions or make all the discoveries that await.

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NASA NTRS1991

A new technique for simulating composite material

This project dealt with the development on new methodologies and algorithms for the multi-spectrum electromagnetic characterization of large scale nonmetallic airborne vehicles and structures. A robust, low memory, and accurate methodology was developed which is particularly suited for modern machine architectures. This is a hybrid finite element method that combines two well known numerical solution approaches. That of the finite element method for modeling volumes and the boundary integral method which yields exact boundary conditions for terminating the finite element mesh. In addition, a variety of high frequency results were generated (such as diffraction coefficients for impedance surfaces and material layers) and a class of boundary conditions were developed which hold promise for more efficient simulations. During the course of this project, nearly 25 detailed research reports were generated along with an equal number of journal papers. The reports, papers, and journal articles are listed in the appendices along with their abstracts.

Volakis, John L.↗
NASA NTRS1991

Determination of the in-flight spectral and radiometric characteristics of the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS)

AVIRIS is a science research imaging spectrometer that measures radiance in 224 channels between 400 to 2450 nm in the electromagnetic spectrum. To determine the inflight spectral and radiometric characteristics of AVIRIS a validation and calibration experiment was performed. Five data sets were acquired over a calibration site on the homogeneous playa of Rogers Dry Lake, California, U.S. Surface reflectance, atmospheric optical depths, and atmospheric water vapor measurements were acquired concurrently with the overflights. These in situ measurements were used to constrain the LOWTRAN 7 radiative transfer code to predict the total spectral radiance incident at the AVIRIS aperture. These predicted radiances and the AVIRIS measured radiances were analyzed to validate the inflight characteristics. Inflight spectral channel positions and response functions over the AVIRIS spectral range were derived. Radiometric calibration coefficients were calculated for each channel as well as radiometric accuracy, intraflight stability, and noise equivalent delta radiance.

Green, Robert O.↗
NASA NTRS1990

Research and technology, 1990: Goddard Space Flight Center

Goddard celebrates 1990 as a banner year in space based astronomy. From above the Earth's obscuring atmosphere, four major orbiting observatories examined the heavens at wavelengths that spanned the electromagnetic spectrum. In the infrared and microwave, the Cosmic Background Explorer (COBE), measured the spectrum and angular distribution of the cosmic background radiation to extraordinary precision. In the optical and UV, the Hubble Space Telescope has returned spectacular high resolution images and spectra of a wealth of astronomical objects. The Goddard High Resolution Spectrograph has resolved dozens of UV spectral lines which are as yet unidentified because they have never before been seen in any astronomical spectrum. In x rays, the Roentgen Satellite has begun returning equally spectacular images of high energy objects within our own and other galaxies.

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NASA NTRS1991

Geologic mapping in Death Valley, California/Nevada using NASA/JPL airborne systems (AVIRIS, TIMS, and AIRSAR)

A multi-sensor aircraft campaign called the Geologic Remote Sensing Field Experiment (GRSFE) conducted during 1989 resulted in acquisition of high quality multispectral images in the visible, near infrared, shortwave infrared, thermal infrared, and microwave regions of the electromagnetic spectrum. The airborne data sets include the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS), the Thermal Infrared Multispectral Scanner (TIMS), and the Airborne Synthetic Aperture Radar (SAR). Ancillary data include Landsat Thematic Mapper, laboratory and field spectral measurements, and traditional geologic mapping. The GRSFE data for a site in the northern Death Valley, (California and Nevada) region were calibrated to physical units and geometrically registered to a map base. Various aspects of this experiment are briefly discussed.

Kruse, Fred A.↗
NASA NTRS1991

Performance of the Multi-Spectral Solar Telescope Array. III - Optical characteristics of the Ritchey-Chretien and Cassegrain telescopes

The Multi-Spectral Solar Telescope Array (MSSTA), which is a sounding-rocket-borne observatory for investigating the sun in the soft X-ray/EUV and FUV regimes of the electromagnetic spectrum, utilizes single reflection multilayer coated Herschelian telescopes for wavelengths below 100 A, and five doubly reflecting multilayer coated Ritchey-Chretien and two Cassegrain telescopes for selected wavelengths in the EUV region between 100 and 1000 A. The paper discusses the interferometric alignment, testing, focusing, visible light testing, and optical performance characteristics of the Ritchey-Chretien and Cassegrain telescopes of MSSTA. A schematic diagram of the MSSTA Ritchey-Chretien telescope is presented together with diagrams of the system autocollimation testing.

Hoover, Richard B.↗
NASA NTRS1993

The FNAS Gamma Ray Observatory

Highly stressed and nonpotential magnetic fields in solar active region are believed to be the site and source of M or X class flares which release as much as 10(exp 32) ergs in a periods of 10 to 1000 s with intense emission detected over most of the electromagnetic spectrum. Such M or X class flares are the most likely gamma-ray emission candidates since sheared magnetic field is the means of energy storage for flare events. We have studied the correlation between 'nonpotentiality' parameters such as 'shear angle' and maximum magnetic field strength with the occurrences gamma-ray events. Also the angle of deviation of the magnetic field from the line of sight was studied since the bremsstrahlung gamma-ray beam produced by relativistic ions and electrons is highly directional in the forward direction and required non-vertical field-lines for the detection of the disk-center events.

Emslie, A. Gordon↗
NASA NTRS1992

A second generation expert system for checking and diagnosing AXAF's electric power system

AXAF - Advanced X-ray Astrophysics Facility - is a third NASA's great space observatory. Each of these observatories is intended to cover different parts of the electromagnetic spectrum (x-ray for AXAF) and to provide high resolution images of celestial sources in our universe. While the spacecraft is in orbit, the electric power system (EPS) performance is monitored via sensors measuring voltages, currents, pressures, and temperatures. The sensor data are sent from the spacecraft to the ground station as telemetry and analyzed on arrival. Monitoring, diagnosis and maintenance of such EPS is an arduous task which requires expertise and constant attention of the ground personnel. To help the ground crew in this task, much of it should be automated and delegated to expert systems, which draw engineer's attention to possible malfunctions and allows him to review the telemetry to determine the source of the trouble, diagnose the suspected fault and to propose a corrective action. Those systems are built on assumptions such as: (1) domain knowledge is available and can be represented as a set of rules; (2) domain knowledge is circumscribed, static, and monotonic; and (3) expert decision making can be emulated by a logical inference mechanism.

Bykat, Alex↗
NASA NTRS1991

Extreme Ultraviolet Explorer. Long look at the next window

The Extreme Ultraviolet Explorer (EUVE) will map the entire sky to determine the existence, direction, brightness, and temperature of thousands of objects that are sources of so-called extreme ultraviolet (EUV) radiation. The EUV spectral region is located between the x-ray and ultraviolet regions of the electromagnetic spectrum. From the sky survey by EUVE, astronomers will determine the nature of sources of EUV light in our galaxy, and infer the distribution of interstellar gas for hundreds of light years around the solar system. It is from this gas and the accompanying dust in space that new stars and solar systems are born and to which evolving and dying stars return much of their material in an endless cosmic cycle of birth, death, and rebirth. Besides surveying the sky, astronomers will make detailed studies of selected objects with EUVE to determine their physical properties and chemical compositions. Also, they will learn about the conditions that prevail and the processes at work in stars, planets, and other sources of EUV radiation, maybe even quasars. The EUVE mission and instruments are described. The objects that EUVE will likely find are described.

Maran, Stephen P.↗
NASA NTRS1992

Imaging solar flares in hard X-rays using Fourier telescopes

The sun emits hard X-rays (above 10 keV) during solar flares. Imaging hard X-ray sources on the sun with spatial resolutions on the order of 1-5 arcsec and integration times of 1 sec will provide greater insight into the energy release processes during a solar flare. In these events, tremendous amounts of energy stored in the solar magnetic field are rapidly released leading to emission across the electromagnetic spectrum. Two Fourier telescope designs, a spatial modulation collimator and a rotating modulation collimator, were developed to image the full sun in hard X-rays (10-100 keV) in an end-to-end simulation. Emission profiles were derived for two hard X-ray solar flare models taken from the current solar theoretical literature and used as brightness distributions for the telescope simulations. Both our telescope models, tailored to image solar sources, were found to perform equally well, thus offering the designer significant flexibility in developing systems for space-based platforms. Given sufficient sensitive areas, Fourier telescopes are promising concepts for imaging solar hard X-rays.

Campbell, Jonathan W.↗
NASA NTRS1993

The Airborne Visible/Infrared Imaging Spectrometer (AVIRIS)

AVIRIS is a facility consisting of a flight system, a ground data system, a calibration facility, and a full-time operations team. The facility was developed by JPL under funding from NASA. NASA also provides funding for operations and maintenance. The flight system is a whisk-broom imager that acquires data in 224 narrow, contiguous spectral bands covering the solar reflected portion of the electromagnetic spectrum. It is flown aboard the NASA high altitude ER-2 research aircraft. The ground data system is a facility dedicated to the processing and distribution of data acquired by AVIRIS. It operates year round at JPL. The calibration facility consists of a calibration laboratory at JPL and a suite of field instruments and procedures for performing inflight calibration of AVIRIS. A small team of engineers, technicians, and scientists supports a yearly operations schedule that includes 6 months of flight operations, 6 months of routine ground maintenance of the flight system, and year-round data processing and distribution. Details of the AVIRIS system, its performance history, and future plans are described.

Vane, Gregg↗
NASA NTRS1992

The Lunar Transit Telescope (LTT) - An early lunar-based science and engineering mission

The Sentinel, the soft-landed lunar telescope of the LTT project, is described. The Sentinel is a two-meter telescope with virtually no moving parts which accomplishes an imaging survey of the sky over almost five octaves of the electromagnetic spectrum from the ultraviolet into the infrared, with an angular resolution better than 0.1 arsec/pixel. The Sentinel will incorporate innovative techniques of interest for future lunar-based telescopes and will return significant engineering data which can be incorporated into future lunar missions. The discussion covers thermal mapping of the Sentinel, measurement of the cosmic ray flux, lunar dust, micrometeoroid flux, the lunar atmosphere, and lunar regolith stability and seismic activity.

Mcgraw, John T.↗
NASA NTRS1992

EOS Moderate Resolution Imaging Spectroradiometer - Phase C/D status and comments on calibration and georeferencing approaches

The Moderate Resolution Imaging Spectroradiometer-Nadir (MODIS-N) is a key observing instrument to be flown on the Earth Observing System (EOS). The MODIS-N is being built under contract to NASA by the Santa Barbara Research Center. MODIS-N is a 36-band instrument with bands chosen in the visible through the emitted thermal IR part of the electromagnetic spectrum to observe key features of the Earth's land and ocean surfaces plus the properties of clouds and other constituents in the troposphere. To provide improved radiometric accuracy, several on-board approaches are used to monitor the calibration of the instrument. The calibration accuracy requirements are 5 percent absolute in the reflected solar radiation observations, 2 percent relative to the sun, and 1 percent absolute in the emitted thermal IR. Requirements for georeferencing of observations are still under study. At the present time, it appears that MODIS-N pixels can be georeferenced to better than 500 meters based on the EOS pointing knowledge capabilities.

Salomonson, Vincent V.↗
NASA NTRS1994

Wavelet compression techniques for hyperspectral data

Hyperspectral sensors are electro-optic sensors which typically operate in visible and near infrared bands. Their characteristic property is the ability to resolve a relatively large number (i.e., tens to hundreds) of contiguous spectral bands to produce a detailed profile of the electromagnetic spectrum. In contrast, multispectral sensors measure relatively few non-contiguous spectral bands. Like multispectral sensors, hyperspectral sensors are often also imaging sensors, measuring spectra over an array of spatial resolution cells. The data produced may thus be viewed as a three dimensional array of samples in which two dimensions correspond to spatial position and the third to wavelength. Because they multiply the already large storage/transmission bandwidth requirements of conventional digital images, hyperspectral sensors generate formidable torrents of data. Their fine spectral resolution typically results in high redundancy in the spectral dimension, so that hyperspectral data sets are excellent candidates for compression. Although there have been a number of studies of compression algorithms for multispectral data, we are not aware of any published results for hyperspectral data. Three algorithms for hyperspectral data compression are compared. They were selected as representatives of three major approaches for extending conventional lossy image compression techniques to hyperspectral data. The simplest approach treats the data as an ensemble of images and compresses each image independently, ignoring the correlation between spectral bands. The second approach transforms the data to decorrelate the spectral bands, and then compresses the transformed data as a set of independent images. The third approach directly generalizes two-dimensional transform coding by applying a three-dimensional transform as part of the usual transform-quantize-entropy code procedure. The algorithms studied all use the discrete wavelet transform. In the first two cases, a wavelet transform coder was used for the two-dimensional compression. The third case used a three dimensional extension of this same algorithm.

Evans, Bruce↗
NASA NTRS1991

NASA Report to Education, Volume 9

This is an edition of 'NASA Report to Education' covering NASA's Educational Workshop, Lewis Research Center's T-34 and the Space Exploration Initiative. The first segment shows NASA Education Workshop program (NEWEST - NASA Educational Workshops for Elementary School Teachers). Highlights of the 14 days of intense training, lectures, fieldtrips and simple projects that the educators went through to teach the program are included. Participants are shown working on various projects such as the electromagnetic spectrum, living in Space Station Freedom, experience in T-34, tour of tower at the Federal Aviation Administrative Facilities, conducting an egg survival system and an interactive video conference with astronaut Story Musgrave. Participants share impressions of the workshop. The second segment tells how Lewis Research Center's T-34 aircraft is used to promote aerospace education in several Cleveland schools and excite students.

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