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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 433 records · Page 24
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NASA NTRS1972

Mariner 9 ultraviolet spectrometer experiment - Photometry and topography of Mars.

Reflectance properties of Mars were measured in a 100-A band (centered at 3050 A) by the UV spectrometer on board Mariner 9 during the period from Nov. 14, 1971 to Mar. 1, 1972. A topographic map of Mars based on the scattering of UV light from the Mars atmosphere (after clearing of the dust storm) is illustrated. The UV light which is Rayleigh-scattered by the Mars molecular atmosphere (with allowance for uniform turbidity) is proportional to surface pressure regardless of the atmospheric temperature structure. Comparison with Mariner 9 radio occultation measurements determines the fraction of total reflectance that is due to atmospheric scattering.

Hord, C. W.↗
NASA NTRS1972

Surface colour photometry of galaxies with Schmidt telescopes.

A method is described which owes its practicality to the capability of Schmidt telescopes to record a number of galaxy images on a single plate and to the existence of high speed computer controlled area-scanning precision microdensitometers such as the Photometric Data Systems model 1010. The method of analysis results in quantitative color-index information which is displayed in a manner that allows any user to effectively study the morphological properties of the distribution of color-index in galaxies.

Wray, J. D.↗
NASA NTRS1973

UBV photometry of Iapetus.

UBV observations of Iapetus on 34 nights have revealed a 0.30-mag difference in the depths of two successive minima in the light curve of this satellite. The difference can be explained by a two-hemisphere model with the leading darker hemisphere having a much stronger variation in brightness with solar phase angle than the trailing brighter hemisphere. Aside from the variation in the depths of the minima, the general character of the light and color curves is similar to that reported by earlier investigators.

Millis, R. L.↗
NASA NTRS1972

Narrow-band photometry of the Galilean satellites.

Observations were made of the Galilean satellites in a narrow-band photometric system with a resolution of about 30 that covers the wavelength range from 0.3 to 1.1 micron. The absolute scale of the system is determined from stellar model computations. It is concluded that 35 Leo, the main comparison star used, has an energy distribution similar to the sun. An attempt is made to interpret the albedo curves in terms of surface constituents.

Wamsteker, W.↗
NASA NTRS1973

Digital multichannel photometry with digicons

The digital system is described and compared to other sensor systems. The digicon system starts with a photocathode, has magnetic focusing of the accelerated photoelectrons, and the electrons hit an array of solid-state diodes. These characteristics, however, are the only ones which are applicable to both the digicon and the other systems. With the digicon system, instead of attempting to read the resulting charges on the diodes by probing electrons, or by a charge transfer out, an actual physical wire is connected to each separate diode. This provides a huge advantage in improved signal-to-noise ratio.

Mcilwain, C. E.↗
NASA NTRS1974

Infrared photometry and spectrophotometry of Titan

The wide variation in infrared brightness temperature of Titan is explained in terms of a greenhouse effect. Radiometric observations in the infrared and microwave frequencies indicate an alternate hot atmospheric model. Methane, ammonia, hydrogen atoms, and nitrogen atoms are suggested as main constituents for the Titan atmosphere.

Morrison, D.↗
NASA NTRS1974

Six-color photometry of Iapetus, Titan, Rhea, Dione and Tethys

The extensive photometric observations of Titan, Iapetus, Rhea, Dione and Tethys have made it possible to separate the solar phase and orbital phase contributions to the observed light variations of these satellites. For Titan, the wavelength dependence of its solar phase coefficient has been obtained. This dependence should prove useful in constructing future model atmospheres. The other four satellites show a surprising array of different photometric behaviors. Despite these differences, all four satellites have similar spectral reflectivities. Clearly Iapetus, Rhea, Dione and Tethys are complex objects, varying substantially from one another in surface structure and/or composition.

Noland, M.↗
NASA NTRS1973

Ultraviolet photometry from the Orbiting Astronomical Observatory. VIII

A comprehensive ultraviolet photometric survey of the blue Ap stars was conducted in order to determine whether the close similarity, deduced from ground observations, between the blue Ap stars and normal B stars with similar UBV colors is maintained at wavelengths shortward of 3000 A. Data are presented for 24 Ap stars and 31 normal comparison standard dwarfs and giants observed by the Wisconsin Experiment Package on OAO 2. Both normal and peculiar stars were chosen, with a few exceptions, for their minimal interstellar reddening and for the absence of known bright companions. The similarity between blue Ap stars and normal B stars of similar UBV colors is not maintained in the ultraviolet. The blue Ap stars emit less ultraviolet flux than normal stars of like UBV colors. They are underluminous and cool in effective temperature for their colors.

Leckrone, D. S.↗
NASA NTRS1973

Ultraviolet photometry from the orbiting Astronomical Observatory. IX - The ultraviolet behavior of U Ophiuchi

Seven simultaneous light curves of U Oph have been obtained which cover a wavelength range from the blue part of the optical spectrum to just longward of L alpha in the ultraviolet. An analysis of these curves has been carried out to determine the spectral variation of limb and gravity darkening as well as to determine geometrical elements for the system. We conclude that (1) U Oph is gravity darkened to the extent expected from von Zeipel's law, (2) limb darkening increases toward shorter wavelengths, and (3) at the shortest wavelengths observed, the two stars are limb-darkened totally.

Source record↗
NASA NTRS1973

Broad-band 20-micron photometry of 76 stars

Observations in the 16 to 28 micron spectral band made with an infrared photometer mounted at the Cassegrain f/10 focus of a 2.24-m telescope are discussed. The stars observed belonged to classes B through M and included several carbon and S stars. Most of them are Mira, semiregular, or irregular variables. The remaining 12 stars are nonvariable objects of which the brightest (both in the visible and infrared) are alpha-Boo and alpha-Tau. Since 16 of the Mira stars varied during the period of observation, it is concluded that they are probably intrinsic variables at 20 microns. There is no conclusive evidence for variation of any other star. Because the variation at this wavelength originates largely in circumstellar shells for most of these stars, the nonvariability suggests that these shells are stable phenomena, at least on a time scale of a year.

Morrison, D.↗
NASA NTRS1974

Ultraviolet photometry from the orbiting astronomical observatory. XV - The strongly magnetic variable HD 215441

The Wisconsin Experiment Package on OAO-2 was used to obtain light curves of the strongly magnetic, variable Ap star HD 215441 over the wavelength range 1550 to 4250 A. This star is characterized by a lack of outstanding spectrum variability at wavelengths accessible from the ground, while undergoing UBV photometric variations of large amplitude. The observations of HD 215441 demonstrate that an Ap star need not be a striking spectrum variable at blue-visible wavelengths for its photometric variations to be controlled by opacity variations in the ultraviolet.

Leckrone, D. S.↗