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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Orbiting Astronomical Observatory (OAO-A2) stabilization and control subsystem

The OAO was successfully operating for approximately 11 months and has made over 2500 stellar observations. The OAO control system was a complex system which takes the 4500-lb vehicle through initial stabilization to star tracker control where a pointing accuracy of less than 1 arc minute was achieved. To obtain this pointing accuracy, the system used six orthogonally mounted gimbaled star trackers. The trackers were two gimbaled devices, having a 1-deg field of view with a + or - 43 deg gimbal excursion. The tracker could recognize and track 2.0 magnitude stars or brighter. The flight results indicated spacecraft pointing accuracies of less than 1 arc minute after tracker calibration with spacecraft jitter less than 3 arc seconds.

Huber, T. E.↗
NASA NTRS1978

Ultraviolet photometry from the Orbiting Astronomical Observatory. XXVIII - Ultraviolet light curves for Alpha Lupi and BW Vulpeculae

Photometric data from the Wisconsin Experiment Package on OAO-2 have been used to construct light curves at three ultraviolet wavelengths for Alpha Lup and at seven wavelengths for BW Vul. Both stars are well-known variables of the Beta Cephei (Beta Canis Majoris) type. The light curves for Alpha Lup are in good agreement with the radial-velocity period. A temperature variation of 400-500 K is derived. The BW Vul light curves confirm recent ephemerides based on a secularly varying period and show a stillstand near light maximum at some wavelengths. Both stars exhibit increasing light amplitude at the shortest ultraviolet wavelengths. There is little evidence for cycle-to-cycle variations on a time scale of the order of 1 day.

Lesh, J. R.↗
NASA NTRS1978

Ultraviolet photometry from the orbiting astronomical observatory. XXX - The Orion reflection nebulosity

Surface-brightness measurements are presented that cover the region of Orion in nine intermediate-width bandpasses ranging from 4250 to 1550 A. The existence of an extended ultraviolet reflection nebulosity in this area is confirmed, and the characteristics of its spectrum and spatial distribution are derived. The observations are consistent with a model in which the dense molecular cloud complex in Orion is illuminated by the foreground Orion aggregate of early-type stars. The interpretation is complicated by the fact that foreground dust may contribute to the observed scattered light. The scattering particles in the cloud appear to exhibit a wavelength-dependent albedo similar to that found for interstellar grains in general, with a strong indication that the phase function changes to a less forward-scattering form in the ultraviolet.

Witt, A. N.↗
NASA NTRS1977

Orbiting astronomical observatory battery and power system design

The battery design of OAO-C (OAO-3) is given and consists of three-20 ampere hour 22 series connected cells in the battery. There are three batteries per spacecraft. The packaging configuration is described. The charging-discharging operations and the voltage potential of the battery system are discussed. Graphs are presented for the voltage limits (battery voltage versus temperature) and end of dark voltages (battery voltage versus ampere-hours discharged) of the battery system used on OAO-3. Data tables are also presented which give a summary of the battery performance and a comparison of OAO-3 with OAO A-2.

Ford, F. E.↗
NASA NTRS1979

Ultraviolet photometry from the Orbiting Astronomical Observatory. XXXII - An atlas of ultraviolet stellar spectra

Ultraviolet stellar fluxes are presented in graphs and tables for 164 bright stars in the spectral region from 1200 to 3600 A. The spectra represent a subset of OAO 2 spectrometer data on file at the National Space Science Data Center. The monochromatic flux is given in units of erg per (sq cm-s-A) with a spectral resolution of about 22 A in the region from 3600 to 1850 A and of approximately 12 A in the region from 1850 to 1160 A.

Code, A. D.↗
NASA NTRS1979

Ultraviolet photometry from the Orbiting Astronomical Observatory. XXXIII - The symbiotic star AG Pegasi

Ultraviolet broadband photometry obtained with the Wisconsin Experiment Package on OAO 2 is presented for the symbiotic binary star AG Peg. The hot component of the binary is found to be a luminous ultraviolet source, with an energy distribution consistent with its WN6 optical spectral type. Total luminosities of 1000 and 17,000 suns are found for the hot star by assuming, respectively, that the giant primary of AG Peg is a normal M3 III star and that it fills its Roche lobe. The eruptive behavior of AG Peg is shown to require the higher luminosity, and the activity in AG Peg is discussed in terms of a very slow novalike nuclear-powered event.

Gallagher, J. S.↗
NASA NTRS1980

Ultraviolet photometry from the Orbiting Astronomical Observatory. XXXVIII - A second atlas of ultraviolet stellar spectra

Ultraviolet stellar spectra are presented for 132 stars in the spectral region from 1200 to 1850 A and 34 stars in the region from 1800 to 3600 A in a graphical and tabular form. The spectra represent a subset of OAO 2 spectrometer data on file at the National Space Science Data Center. The monochromatic flux is given in units of ergs/sq cm s A with a spectral resolution of about 12 A in the region from 1850 to 1160 A and of about 22 A in the region from 3600 to 1800 A.

Meade, M. R.↗
NASA NTRS1980

Ultraviolet photometry from the Orbiting Astronomical Observatory. XXXIV - Filter photometry of 531 stars of diverse types

Ultraviolet magnitudes for 531 stars observed with the Wisconsin Experiment Package on OAO 2 are tabulated. It is noted that these data constitute a subset of the OAO 2 data on file at the National Space Science Data Center. The tabulation contains previously published data all reduced to a uniform magnitude system. It is pointed out that the observations were obtained with the medium band interference filter photometers. Eleven magnitudes are given designated by their centroid wavelengths.

Code, A. D.↗
NASA NTRS1982

Ultraviolet photometry from the Orbiting Astronomical Observatory. XL - The energy distributions of spiral and irregular galaxies

Measurements of the total light of 40 spiral and irregular galaxies are presented. The photometry covers the wavelength range 1550-4250 A and is calibrated on an absolute basis. On the average later-type galaxies are not only bluer at short wavelengths than ellipticals but significantly bluer than visual colors would imply. This reflects a recent history of more vigorous formation of massive stars. The shape of the upper part of the initial mass function apparently varies more among early-type galaxies, producing a wide scatter in their energy distributions. In at least some galaxies interstellar dust appears to have little influence upon the emerging radiation. The local volume luminosity spectrum due to galaxies turns up steeply at short wavelengths, and is shaped largely by contributions from late-type galaxies. The observed ultraviolet background cannot be produced by normal galaxies, although the large corrections implied by theoretical evolutionary models may account for the measurements.

Code, A. D.↗
NASA NTRS1984

The PDS-VAX intelligent plate scanning system of Trieste Astronomical Observatory

An intelligent subsystem for interfacing a PDS1010A digital microdensitometer to a DEC DR11W DMA 16 bit UNIBUS port in DEC VAX VMS environment was tested. The subsystem employs two MOTOROLA M68000 microprocessors with 128 KB data memory. The PDS primitives and the user defined high level scanning functions and preprocessing modules are loaded from the host computer into two 8 KB RAM memories in the microprocessors using a dedicated PDS control language. The subsystem is planned to employ a nonstandard photomultiplier electronics. Two design schemes were tested: (1) based on three amplifiers of gain 10 cascaded and multiplexed to a 12 bit AD converter, and (2) based on a single amplifier of gain 100 and two 14 bit AD converters.

Pucillo, M.↗
NASA NTRS1984

Ultraviolet photometry from the Orbiting Astronomical Observatory. XXXIX - The structure of the eclipsing Wolf-Rayet binary V444 Cygni as derived from light curves between 2460 A and 3. 5 microns

The WN5 component of V444 Cyg is characterized on the basis of light curves constructed using 1971 OAO observations at 425, 332, 298, and 246 nm and the broadband data at 2.2 and 3.5 microns of Hartmann (1978). Data and calculation results are presented in tables and graphs and discussed. Parameters estimated include core radius 2.9 solar radii, surface temperature 90,000 K, surface electron density 9 x 10 to the 12th/cu cm, surface outflow velocity 400 km/s, and terminal velocity (at about 10 solar radii) 2500 km/s, suggesting that the flow is He. These results are found to agree with the model of Wolf-Rayet atmospheres proposed by Beals (1929, 1944).

Cherepashchuk, A. M.↗
NASA NTRS1988

Advanced technology for a lunar astronomical observatory

Significant new technologies are required for three proposed telescopes to be operated on the moon. These technologies are in the areas of contamination/interference control, test and evaluation, manufacturing, construction autonomous operations and maintenance, power and heating/cooling, stable precision structures, optics, parabolic antennas, and communications/control. Telescopes for the lunar surface need to be engineered to operate for long periods with minimal intervention by humans or robots.

Johnson, Stewart W.↗
NASA NTRS1989

The South African Astronomical Observatory

Topics discussed in the Overview of Year 1988 include the following: Supernova in the Large Magellanic Cloud; Galaxies; Ground based observations of celestial x ray sources; the Magellanic Clouds; Pulsating variables; Galactic structure; Binary star phenomena; The provision of photometric standards; Nebulae and interstellar matter; Stellar astrophysics; Astrometry; Solar system studies; Visitors programs; Publications; and General matters.

Source record↗
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.↗