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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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At least 253 records · Page 14
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NASA NTRS1975

The new Martian nomenclature of the International Astronomical Union

A new nomenclature for Martian regions and topographic features uncovered by Mariner 9, as officially adopted by the International Astronomical Union, is described. About 180 craters generally of diameters greater than 100 km have been named, as well as 13 classes of topographic features designated catena, chasma, dorsum, fossa, labyrinthus, mensa, mons, patera, planitia, planum, tholus, vallis, and vastitas. In addition seven craters and the Kepler Dorsum are named on Phobos, and two craters on Deimos. Coordinates and maps of each named feature are displayed.

De Vaucouleurs, G.↗
NASA NTRS1976

Sensitivity of an astronomical infrared heterodyne spectrometer

The factors determining the sensitivity of a real astronomical heterodyne spectrometer are described. The deviation from the ideal heterodyne system for line detection is described in terms of a series of degradation factors. A discussion of degradation due to a low local oscillator power and to line profile detection is presented. Representative values for the degradation factors are given. Even with a total degradation of not less than 30, the heterodyne spectrometer is still found to be a highly sensitive tool in IR astronomy.

Kostiuk, T.↗
NASA NTRS1976

Asteroids as meteorite parent-bodies - The astronomical perspective

A review of astronomical evidence suggests that asteroids are the parent-bodies for most meteorites. The surfaces of most asteroids are like carbonaceous chondrites while a significant minority are of stony-iron composition. Other meteorite types are recognized in the belt but are rare. The size distribution of stony-iron asteroids implies they are remnant cores of about 100 differentiated bodies subjected to collisional fragmentation by carbonaceous objects initially about 300 times more numerous than now. Incomplete evidence on parent-body collisions exists in data on Hirayama families, asteroid lightcurves, and the compositional homogeneity of individual asteroids. Modern-day asteroid regoliths are thin and cannot have been environments for formation of most brecciated, gas-rich meteorites; such meteorites formed during early accretion of the asteroids. A scenario for the origin and evolution of meteorite parent-bodies is presented which includes: (1) interruption of planet-formation by processes due to Jupiter; (2) substantial asteroidal collisions during the first 0.5 b.y.; and (3) formation of most meteorite types within the differentiated bodies.

Chapman, C. R.↗
NASA NTRS1976

Preliminary design study of astronomical detector cooling system

The preliminary design of an astronomical detector cooling system for possible use in the NASA C-141 Airborne Infrared Observatory is presented. The system consists of the following elements: supercritical helium tank, Joule-Thomson supply gas conditioner, Joule-Thomson expander (JTX), optical cavity dewar, optical cavity temperature controller, adjustable J-T discharge gas pressure controller, and vacuum pump.

Norman, R. H.↗
NASA NTRS1977

Analyses of atmospheric extinction data obtained by astronomers. I - A time-trend analysis of data with internal accidental errors obtained at four observatories

Long-term time-trend analysis was performed on astronomical atmospheric extinction data in wideband UBV and various narrow-band systems recorded at Cerro Tololo, Kitt Peak, Lick, and McDonald observatories. All of the data had to be transformed into uniform monochromatic extinction data before trend analysis could be performed. The paper describes the various reduction techniques employed. The time-trend analysis was then carried out by the method of least squares. A special technique, called 'histogram shaping', was employed to adjust for the fact that the errors of the reduced monochromatic extinction data were not essentially Gaussian. On the assumption that there are no compensatory background and local extinction changes, the best values obtained for extinction trends due to background aerosol changes during the years 1960 to 1972 are 0.006 + or - 0.013 (rms) and 0.009 + or - 0.009 (rms) stellar magnitudes per air mass per decade in the blue and yellow wavelength regions, respectively.

Taylor, B. J.↗
NASA NTRS1976

Recent developments at JPL in the application of digital image processing techniques to astronomical images

Several techniques of a digital image-processing nature are illustrated which have proved useful in visual analysis of astronomical pictorial data. Processed digital scans of photographic plates of Stephans Quintet and NGC 4151 are used as examples to show how faint nebulosity is enhanced by high-pass filtering, how foreground stars are suppressed by linear interpolation, and how relative color differences between two images recorded on plates with different spectral sensitivities can be revealed by generating ratio images. Analyses are outlined which are intended to compensate partially for the blurring effects of the atmosphere on images of Stephans Quintet and to obtain more detailed information about Saturn's ring structure from low- and high-resolution scans of the planet and its ring system. The employment of a correlation picture to determine the tilt angle of an average spectral line in a low-quality spectrum is demonstrated for a section of the spectrum of Uranus.

Lorre, J. J.↗
NASA NTRS1976

A telescope for the Infrared Astronomical Satellite /IRAS/

The Infrared Astronomical Satellite (IRAS) will be used to survey the 8 to 120 micron spectrum of the entire sky to the faintest flux levels possible by using state-of-the-art detectors and preamplifiers. As a result of a recently completed study of the telescope and focal plane, a concept has been devised that demonstrates the feasibility of using stored cryogen to cool the telescope for one year of operation in a polar twilight orbit at an altitude of 900 km. Predictions regarding noise equivalent flux density, cryogenic lifetime, and the number of noise spikes caused by Van Allen belt radiation are presented. The telescope is cooled both by supercritical and by superfluid helium. The on-board signal processing includes provisions for suppressing noise spikes.

Hedden, R. L.↗
NASA NTRS1977

An infrared upconverter for astronomical imaging

An imaging upconverter has been constructed which is suitable for use in the study of the thermal 10-micron radiation from astronomical sources. The infrared radiation is converted to visible radiation by mixing in a 1-cm-long proustite crystal. The phase-matched 2-kayser bandpass is tunable from 9 to 11 microns. The conversion efficiency is 2 by 10 to the -7th power and the field of view of 40 arc seconds on the sky contains several hundred picture elements, approximately diffraction-limited resolution in a large telescope. The instrument has been used in studies of the sun, moon, Mercury, and VY Canis Majoris.

Boyd, R. W.↗
NASA NTRS1976

Report of the Joint Scientific Mission Definition Team for an infrared astronomical satellite

The joint effort is reported of scientists and engineers from the Netherlands, the United Kingdom, and the United States working as a team for the purpose of exploring the possibility of a cooperative venture. The proposed mission builds upon experience gained from the successful Astronomical Netherlands Satellite (ANS). This satellite will be in a polar orbit at an altitude of 900 km. It will carry an 0.6 m diameter telescope cooled with helium to a temperature near 10K. An array of approximately 100 detectors will be used to measure the infrared flux in four wavelength bands centered at 10, 20, 50, and 100 microns. Sources will be located on the sky with positional accuracy of 1/2 arcminute. The instrument should be able to investigate the structure of extended sources with angular scales up to 1.0 deg. The entire sky will be surveyed and the full lifetime of the mission of about one year will be necessary to complete the survey. Special observational programs will also be incorporated into the mission.

Source record↗
NASA NTRS1978

Continued development of doped-germanium photoconductors for astronomical observations at wavelengths from 30 to 120 micrometers

The development of doped-germanium detectors which have optimized performance in the 30- to 120-mu m wavelength range and are capable of achieving the objectives of the infrared astronomical satellite (IRAS) space mission is discussed. Topics covered include the growth and evaluation of Ge:Ga and Ge:Be crystals, procedures for the fabrication and testing of detectors, irradiance calculations, detector responsivity, and resistance measurements through MOSFET. Test data are presented in graphs and charts.

Bratt, P. R.↗
NASA NTRS1978

Grain formation in astronomical systems: A critical review of condensation processes

An analysis is presented of the assumption and the applicability of the three theoretical methods for calculating condensations in cosmic clouds where no pre-existing nuclei exist. The three procedures are: thermodynamic equilibrium calculations, nucleation theory, and a kinetic treatment which would take into account the characteristics of each individual collision. Thermodynamics provide detailed results on the composition temperature and composition of the condensate provided the system attains equilibrium. Because of the cosmic abundance mixture of elements, large supersaturations in some cases and low pressures, equilibrium is not expected in astronomical clouds. Nucleation theory, a combination of thermodynamics and kinetics, has the limitations of each scheme. Kinetics, not requiring equilibrium, avoids nearly all the thermodynamics difficulties but requires detailed knowledge of many reactions which thermodynamics avoids. It appears to be the only valid way to treat grain formation in space. A review of experimental studies is given.

Donn, B.↗
NASA NTRS1977

Infrared Astronomical Satellite

The objective of the Infrared Astronomical Satellite is to produce an unbiased all-sky survey in the wavelength region between 8 and 120 microns. Using a 60 cm diameter helium cooled telescope and detector arrays which are essentially zodiacal light background photon noise limited, heretofore unprecedented sensitivity can be achieved. The optical design, the focal plane layout and expected performance of the current design concept are discussed.

Aumann, H. H.↗
NASA NTRS1978

An investigation of the astronomical theory of the ice ages using a simple climate-ice sheet model

The astronomical theory of the Quaternary ice ages is incorporated into a simple climate model for global weather; important features of the model include the albedo feedback, topography and dynamics of the ice sheets. For various parameterizations of the orbital elements, the model yields realistic assessments of the northern ice sheet. Lack of a land-sea heat capacity contrast represents one of the chief difficulties of the model.

Pollard, D.↗
NASA NTRS1978

Airborne infrared astronomical observations by Fourier transform spectroscopy

Infrared spectroscopic observations from NASA-operated aircraft constitute a rapidly maturing application of FTS methods initially developed for ground-based telescopes. Coupled to airborne telescopes up to 36 in. in diameter, these experiments are now producing new astronomical results as exciting and unexpected as those derived from Connes's first high resolution planetary observations at mountain-top observatories. This review examines the special problems of the IR spectral region that led to aircraft observatories and includes a brief survey of the facilities themselves and their modes of operation. The special problems of operating FTS devices on aircraft and the scientific results achieved with current capabilities are discussed. Finally, airborne observations are compared to the ultimate in high-altitude observing platforms: earth-orbiting cooled and uncooled telescopes carried by the Space Shuttle vehicle.

Larson, H. P.↗
NASA NTRS1977

High resolution X-ray optics for astronomical and laboratory sources

In recent years X-ray telescopes have been used successfully for high resolution observations of astronomical objects, in particular the solar corona. At the present time X-ray microscopes are being developed for diagnostics of laser and electron beam induced fusion plasmas. This paper describes both types of imaging systems using as examples the AS&E X-ray telescope on Skylab and a 10X microscope being built for Los Alamos Scientific Laboratories. The designs, manufacturing tolerances, fabrication, testing, and performance are discussed. Steps for further development in both imaging areas are identified.

Silk, J. K.↗
NASA NTRS1978

Astronomical monochromatic imaging as applied to the Io sodium cloud

Four types of instruments for recording monochromatic astronomical images are compared: filters; slitless spectrographs; multislit spectrographs; and interferometers. Each of these instruments has been used on the sodium emission cloud of Io, with varying degrees of success. Multislit spectrographs and interferometers encode the signal, and it can be extracted with a noise level close to that for photon statistics. This is not normally the case for filters and slitless spectrographs. On balance, it is found that a Mach-Zehnder interferometer provides the best system for imaging faint monochromatic signals on a brighter continuum background.

Murcray, F. J.↗
NASA NTRS1978

Assessment study of infrared detector arrays for low-background astronomical research

The current state-of-the-art of infrared detector arrays employing charge coupled devices (CCD) or charge injection devices (CID) readout are assessed. The applicability, limitations and potentials of such arrays under the low-background astronomical observing conditions of interest for SIRFT (Shuttle Infrared Telescope Facility) are determined. The following are reviewed: (1) monolithic extrinsic arrays; (2) monolithic intrinsic arrays; (3) charge injection devices; and (4) hybrid arrays.

Ando, K. J.↗