Automatic computer reduction of astronomical television images
Automatic data reduction system for TV images of star fields acquired from OAO
Deutschman, W. A.↗
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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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A variable conductance heat-pipe flight experiment
Gas controlled variable conductance heat pipe for OAO-C onboard processor temperature stabilization, describing thermal performance tests under simulated flight conditions
Kirkpatrick, J. P.↗
MESS /Misalignment Estimation Software System/ for in-flight alignment and calibration of spacecraft attitude sensors
Misalignment estimation software system /MESS/ for in-flight celestial and inertial reference attitude sensor alignment and calibration on OAO
Desjardins, R.↗
The Advanced On-board Processor (AOP)
The goal of the Advanced On-Board Processor (AOP) development program is to design, build, and flight qualify a highly reliable, moderately priced, digital computer for application on a variety of spacecraft. Included in this development program is the preparation of a complete support software package which consists of an assembler, simulator, loader, system diagnostic, operational executive, and many useful subroutines. The AOP hardware/software system is an extension of the On-Board Processor (OBP) which was developed for general purpose use on earth orbiting spacecraft with its initial application being on-board the fourth Orbiting Astronomical Observatory (OAO-C). Although the OBP possesses the significant features that are required for space application, however, when operating at 100% duty cycle the OBP is too power-consuming for use on many smaller spacecraft. Computer volume will be minimized by implementing the processor and input/output portions of the machine with large scale integrated circuits. Power consumption will be reduced through the use of plated wire and, in some cases, semiconductor memory elements.
Hartenstein, R. G.↗
UV and radiofrequency observations of Wolf-Rayet stars
Observations of W stars in the ultraviolet by OAO 2 and at 750 and 1400 MHz with the Green Bank telescopes are discussed. The emphasis is on the Green Bank observations of W stars with symmetric nebulae around them, their interpretation, and comparisons with other data. The implications regarding mass distribution, internal motion, flux density, ejected mass, velocity dispersion, and expanding envelopes are considered in detail.
Johnson, H. M.↗
The UV spectrum of the Crab Nebula
Observations of the Crab nebula are described, which were made under the OAO 2/NASA guest-investigator program with WEP stellar photometers. The 10 foot-diameter focal plane diaphragm was ample enough to accept the 4 ft X 6 ft image. The logarithm of the integrated relative intensity per wavelength interval, corrected for sky background, and the rms error, from 11 passbands in the range 4250 to 1380 A, are given. No correction was given for polarization of light. The data were converted to logarithm of the flux density per frequency interval and plotted on scales of log nu (Hz) and of reciprocal microns with two adjustments.
Johnson, H. M.↗
Fabrication and evaluation of aluminum heat pipes
An evaluation is presented for the current heat pipe system on the OAO spacecraft, in order to increase its capability for future missions. A detailed analysis was made of the requirements, and approaches for the design of optimized heat pipes to meet future needs were identified. A composite wick heat pipe was developed, which has significantly higher transport capability than those of conventional wick design.
Source record↗
The ultraviolet flux envelopes of main-sequence B stars
Flux envelopes on an absolute energy scale from 1100 to 6000 A prepared from OAO-2 scans and from published ground-based material are presented for gamma Leporis, B0.5 5 eta Ursae Majoris, B3 5, gamma Ursae Majoris, A0 5, and alpha Lyrae, A0 5, and for alpha Canis Majoris Al 5 from rocket scans. These, with already published flux envelopes for Zeta Draconis, B6 3, and alpha Leonis, B7 5 (Underhill 1972) are intercompared and compared with reference flux envelopes predicted by LTE theory from lightly line-blanketed model atmospheres. A considerable line blocking occurs at wavelengths shortward of 3000 A with respect to the theoretical continuous spectra. The line blocking may be as much as 50 per cent at 1500 A and between 1500 A and 2500 A it is comparable to that which exists in the sun between 3000 A and 4000 A. Although gamma Urase Majoris, alpha Lyrae and alpha Canis Majoris have very similar visible spectra when viewed at low resolution, their ultraviolet spectra are significantly different, in particular alpha Lyrae shows an ultraviolet excess.
Underhill, A. B.↗
Ultraviolet photometry of the eclipsing variable CW Cephei
A series of photometric observations was made of the eclipsing variable CW Cephei on the OAO 2. Approximate elements were derived from the eclipse depths and shape of the secondary. Persistent asymmetries and anomalous light variations, larger than the expected experimental error, were also found, subsequent ground-based observations show H alpha entirely in emission, indicating the presence of an extended gaseous system surrounding one or both components. A detailed comparison was made of the flux distribution of the binary relative to that for the nominally unreddened stars delta Pic, BlIII, and eta Aur, B3V, to investigate the effects of interstellar extinction. The resultant extinction curves, normalized at a wavelength of 3330 A, show a relatively smooth increase with decreasing wavelength.
Sobieski, S.↗
Precision digital solar aspect sensor
The development of a digital solar aspect sensor with a resolution of approximately 14 arc-seconds is discussed. An interpolation technique was used to generate the fine angle measurements. The sensor and its mode of operation are described. The electronic and mechanical design of the sensor were completed, and two flight units, one for the OAO 4 and the other for determining the attitude of a spinning spacecraft, are being fabricated.
Scherer, H. P.↗
Measurements of the earth's airglow in the vacuum ultraviolet
A valuable by-product of the OAO-2 astronomy mission has been the first extensive set of measurements of the earth's airglow between 1000 and 3000 A. These measurements, made with the Wisconsin experiment package, provide clues to the structure and chemistry of the upper atmosphere. The most significant results from these observations are: (1) the detailed altitude profile of the emissions from the dark and sunlit earth limb; and (2) the confirmation of recent theories concerning the source of the dayglow radiation between 1350 and 1700 A.
Waters, C. R.↗
Minor constituents in planetary atmospheres: Ultraviolet spectroscopy from the orbiting astronomical observatory
OAO data between 2000 A and 3600 A, obtained by the Wisconsin experimental package objective grating scanning spectrometer, are used to set upper limits to the abundances of many minor constituents in the atmospheres of Mars, Jupiter, Saturn, and Venus.
Owen, T.↗
Interstellar extinction in the ultraviolet
Interstellar extinction curves over the region 3600-1100 A for 17 stars are presented. The observations were made by the two Wisconsin spectrometers onboard the OAO-2 with spectral resolutions of 10 A and 20 A. The extinction curves generally show a pronounced maximum at 2175 plus or minus 25 A, a broad minimum in the region 1800-1350 A, and finally a rapid rise to the far ultraviolet. Large extinction variations from star to star are found, especially in the far ultraviolet; however, with only two possible exceptions in this sample, the wavelength at the maximum of the extinction bump is essentially constant. These data are combined with visual and infrared observations to display the extinction behavior over a range in wavelength of about a factor of 20.
Bless, R. C.↗
Diffuse galactic light in the 1500-4200 angstrom region
Diffuse galactic light has been observed with the four stellar photometers of the OAO-2 in 29 of Kapteyn's selected areas. The data can be understood in terms of a wavelength dependent albedo of the interstellar grains with a pronounced minimum around 2200 A with a rapid increase towards unity at wavelengths below 2000 A.
Witt, A. N.↗
The ultraviolet spectrum of the Crab Nebula
New observations of the Crab Nebula by OAO 2 stellar photometers are reported. Processed image data of the Crab give the logarithm of the integrated relative intensity per wavelength interval, corrected for sky background, and the rms error from 11 passbands in the ultraviolet range. The data are converted to logarithms of flux density per frequency interval and plotted on logarithmic scales with corrections for interstellar extinction.
Johnson, H. M.↗
Ultraviolet photometry of the eclipsing variable CW Cephei
An extended series of photometric observations were made of the eclipsing variable CW Cephei using the Wisconsin instrument on OAO-2. Approximate elements which were derived based solely on the eclipse depths and shape of the secondary are in satisfactory agreement with those found using ground based observations. However, persistent asymmetries and anomalous light variations, all larger than the expected experimental error, were also found; subsequent ground-based observations show H sub alpha entirely in emission indicating the presence of an extended gaseous system surrounding one or both of the components. Consistent solutions utilizing all data at all wavelengths were not found.
Sobieski, S.↗
Absolute ultraviolet spectrophotometry of Alpha Canis Majoris, Gamma Orionis, Kappa Orionis and Alpha Leonis
Spectral observations of the stars Alpha Canis Majoris, Gamma Orionis, Kappa Orionis and Alpha Leonis have been obtained in the range 1150-4000 A, using rocket borne spectrometers. The payloads have a 13-inch diameter telescope, a rotatable concave diffraction grating, and three pulse counting photomultiplier photometers. The observations are systematically lower than those of Carruthers (1968) at 1270 A, of Smith (1967) at 1376 A, and of Campbell (1970) at 2150 and 2550 A. The data are also about 15 percent lower than the ground-based photometry reported by Schild, Peterson and Oke (1971). The OAO-2 short wavelength scanner calibration agrees with the alpha Leo observations, but disagrees for Kappa Ori and Gamma Ori.
Evans, D. C.↗
The near ultraviolet spectrum of B and A type main sequence stars
Scans of lambda Lep, eta UMa, xi Dra, epsilon Dor, alpha Leo, phi Dra, upsilon Dra, beta Aur, alpha Pic and alpha Dor have been obtained with scanner OAO-2 over the range 1800-3600 A. These scans have been reduced to tracings of F sub lambda in the 20 A pass band vs. wavelength using a wavelength conversion scale and a relative spectral sensitivity function. The general trend of the relative flux plots compares well with the continua predicted by simple model atmospheres.
Underhill, A. B.↗