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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 379 records · Page 21
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NASA NTRS1977

Preliminary report on the CTS transient event counter performance through the 1976 spring eclipse season

The transient event counter is described, defining its operational characteristics, and presenting the preliminary results obtained through the first 90 days of operation including the Spring 1976 eclipse season. The results show that the CTS was charged to the point where discharges have occurred. The discharge induced transients have not caused any anomalous events in spacecraft operation. The data indicate that discharges can occur at any time during the day without preference to any local time quadrant. The number of discharges occurring in the 1 sec sample interval are greater than anticipated.

Stevens, N. J.↗
NASA NTRS1977

Search for color changes and brightening of Io upon eclipse reappearance

Medium-resolution spectra were made of Io as it emerged from two eclipses in December 1975. In the wavelength range 4000-5800 A, no spectral changes greater than the standard deviations were observed when the spectrum of Io just after reappearance was divided by the spectrum of Io 20 min later. No substantial increase in total brightness was observed over the same time interval. These observations were made at a time when the sub-earth point was in Io's northern hemisphere; therefore, prediction of positive posteclipse brightening in this circumstance is not confirmed.

Nelson, R. M.↗
NASA NTRS1978

NTS-2 battery after 1 year and 3 eclipse seasons

The performance of the nickel hydrogen batteries on board the NTS-2 satellite was determined after being in orbit for several months. The effects of the eclipses were presented as well as the power loading operations.

Stockel, J.↗
NASA NTRS1980

IR brightness and eclipse cooling of Saturn's rings

Equatorial scans of Saturn at 20 microns wavelength, obtained with the Mayall 4-m telescope in 1978-79, show a continuing decrease in the specific brightness of the A and B rings as the ring plane projection approaches and edge-on apparition. The decreased brightness of the previously dominant B ring reveals more clearly a large difference in brightness between the east and west ansae portions of the C ring, in contrast to a barely discernible difference for the other ring ansae. The amount of eclipse cooling is compatible with a C ring particle size of about 1 cm. It is proposed here that the B ring brightness variation could partially result from a decrease of absorbed insolation by a modest amount of visible scattering.

Nolt, I. G.↗
NASA NTRS1981

The 1979 eclipse of zeta Aurigae

Observations of the system zeta Aurigae made around primary eclipse are described, and their significance is discussed in a preliminary fashion.

Chapman, R. D.↗
NASA NTRS1980

Galilean satellite eclipse studies. I - Observations and satellite characteristics

Spectrophotometric light curves of 12 Galilean satellite eclipses are reported. The observations were made in 20 to 30 channels over the wavelength range 3240 to 10,500 A using the 200-in. telescope. The initial data processing is described. These data measure the Jovian aerosol content in the lower stratosphere and uppermost troposphere and the methane abundance in the lower stratosphere. The data are consistent with a lack of limb darkening on the Galilean satellites. The orbit of Callisto is shown to be inclined 0.08 + or - 0.02 deg to the equatorial plane of Jupiter.

Greene, T. F.↗
NASA NTRS1980

Galilean satellite eclipse studies. II - Jovian stratospheric and tropospheric aerosol content

Aerosol profiles of the Jovian stratosphere and troposphere are presented using the Galilean satellite eclipse technique. The aerosol content is tenuous and varies with altitude, increasing rapidly with downward passage through the tropopause. The data indicate the presence of some aerosols of undetermined structure above the tropopause. An extended haze distribution is proposed, but the possibility that the stratospheric aerosol resides in a thin layer is not excluded.

Smith, D. W.↗
NASA NTRS1980

Galilean satellite eclipse studies. III - Jovian methane abundance

The methane abundance in the lower Jovian stratosphere is measured using the Galilean satellite eclipse technique. The average mixing ratio at the locations measured is larger than the expected value for a solar abundance of carbon with the expected value for a solar abundance of carbon with the possibility of some zenographic variation. Observationally compatible values are found for the South Temperate Zone, the edge of the Great Red Spot and the South Tropical Zone, and the Great Red Spot.

Smith, D. W.↗
NASA NTRS1981

IO - Could SO2 condensation/sublimation cause the sometimes reported post-eclipse brightening

It is shown that each of the three quantifiable brightening characteristics (i.e., amplitude, time-scale /half-life/, and temporal variability) suggests that brightening of Io may be due to condensation and sublimation of SO2 frost. This is concentrated within a region that encompasses both the subsolar points at the time of entrance into and emergence from eclipse, and volcanic sources. Qualitatively and intuitively, an SO2 frost hypothesis is found to provide good possibilities for explaining any variations in Io's ability to brighten, which may occur on a time scale of years.

Fanale, F. P.↗
NASA NTRS1981

A model of solar flux attenuation during eclipse passage and its effects on photoelectron emission from satellite surfaces

The basic theory of solar flux attenuation by the earth's atmosphere is reviewed and a model of the time-varying flux observed by a satellite during eclipse passage developed. The general model is applied to the specific problem of variations in photoelectron flux during penumbral passage and the effects of wavelength, solar activity, and atmospheric constituents on photoelectron emission investigated. Predictions of the photoelectron current expected from tungsten and aluminum surfaces are then successfully compared with actual observations from the ATS-5 and Injun 5 satellites confirming the validity of the model.

Garrett, H. B.↗
NASA NTRS1981

Measurement of stratospheric aerosol on Saturn using an eclipse of Titan

Measurements of the aerosol content in the Saturn atmosphere made during an eclipse of Titan by Saturn are presented. Observations of the ingress of Titan into the shadow of Saturn on December 20.08, 1979 were made by the 74-in telescope at Kottamia Station in Egypt at an effective wavelength of 6728 A with FWHM of 1000 A. The deviation of the observed light curve after a satellite darkening of 3 mag from that predicted for a clear Saturn atmosphere is interpreted in terms of an aerosol layer decreasing in extinction coefficient from a base altitude 5 km below the planetary tropopause to an altitude of up to 75 km above the tropopause. For an aerosal layer extending to 75 km above the tropopause calculations reveal possible optical depths ranging from 0.020 to 0.050. The range of the optical depth is comparable to that of the Jupiter atmosphere, and suggests that similar processes may be responsible for the stratospheric haze on both planets.

Smith, D. W.↗
NASA NTRS1981

Submillimeter observations of solar limb-brightening in the total solar eclipse of 31 July 1981

Eight flights of the Kuiper Airborne Observatory (KAO) were devoted to solar observation. The successful observation of a total solar eclipse was accomplished. The observations were made simultaneously at 30, 50, 100, and 200 microns. The successful adaptation of the KAO for solar observations thus provided the most detailed data to date in this spectral band. The results from a preliminary analysis of the KAO data are summarized: (1) the 200 micron limb is extended about 3 arc sec above the 30 micron limb, indicating the prescence of cool dense material up to the altitudes of spicules; (2) strong radial darkening of the quiet sun intensity profile appeared at 200 microns, probably an indication that hot material in the low chromosphere is recessed into vertical magnetic flux tubes embedded in a cooler nonmagnetic substrate, which obscures the heated material approaching the limb; (3) active regions were observed to undergo a strong increase in contrast above the quiet sun background at wave lengths of 100 microns and longer; and (4) the moon was mapped for use as a photometric standard for determining the absolute intensity of the sun in all four wavelength bands.

Becklin, E. E.↗
NASA NTRS1982

UV observations of the 1981 eclipse of 32 Cygni

Preliminary results of an extensive set of high dispersion UV spectra of the supergiant eclipsing system 32 Cyg are detailed and contrasted with spectroscopic studies of other Zeta Aur systems.

Stencel, R. E.↗
NASA NTRS1981

High resolution interferometric observations of the solar limb at 4.9 and 10.7 GHz during the solar eclipse of October, 1977

The radial intensity profile of the quiet solar limb has been measured at high spatial resolution using the VLA at 4.9 GHz and the Owens Valley solar interferometer at 10.7 GHz during the partial solar eclipse of October 12, 1977. The spatial resolution (13.8 arcsec at 4.9 GHz and 7.4 arcsec at 10.7 GHz) was provided primarily by the lunar limb. Substantial limb brightening at 4.9 GHz was found with a peak brightness temperature corresponding to an 80% increase over the disk value, and a possible small limb enhancement at 10.7 GHz. The results are consistent with a simple model consisting of a uniform disk (provided by a thoroughly roughened transition zone) overlaid by a corona in hydrostatic equilibrium with a density of 5 x 10 to the 8th at its base. The lack of the secant-like variation in the microwave intensity from center to limb is explained by a corona contained in loop structures rather than in spherically symmetric layers.

Marsh, K. A.↗
NASA NTRS1982

Submillimeter extensions of the solar limb determined from observations of the total eclipse of 1981 July 31

First results are presented of observations of a lunar occultation of the solar limb made from the Kuiper Airborne Observatory in the 30 micrometr, 50 micrometer, 100 micrometer, and 200 micrometer continuum during the total solar eclipse of 1981 July 31. The solar limb was extended at the longer wavelengths up to 1000 km higher than predicted from smooth plane-parallel chromospheric models. Results at both second and third contact show the infrared limb extensions to be approximately 0".8, 1"5, 2".5 and 3".0 above the visible limb in the observed bands, respectively. A possible interpretation proposes chromospheric fine structure inhomogeneities of greater density than presently incorporated in models of the middle chromosphere.

Lindsey, C.↗
NASA NTRS1982

Secondaries of eclipsing binaries. IV - The triple system Lambda Tauri

High signal-to-noise ratio Reticon observations of Lambda Tauri have been obtained along with high-quality orbital elements for both the primary and secondary of the eclipsing system. The velocity curve of the secondary is determined for the first time. The findings include: K(1) = 56.9 + or - 0.6 km/s, K(2 = 215.6 + or - 0.7 km/s, m(1) = 7.18 + or - 0.09 solar masses, and m(2) = 1.89 + or - 0.04 solar masses. The 33-day periodicity in the residuals is confirmed and is present in the secondary velocities as well as those of the primary, and can unambiguously be ascribed to orbital motion about a third body. The K and f(m) for the 33-day orbit are 10.1 + or - 0.7 km/s and 0.0034 + or - 0.0008 solar masses. The photometry shows that the orbits are coplanar to within seven degrees. The mass of the third body is 0.7 + or - 0.2 solar masses; it is most probably a K dwarf.

Fekel, F. C., Jr.↗
NASA NTRS1983

Local circumstances in Java during the total solar eclipse of 1983

A total solar eclipse of unusually long duration will occur on 11 June 1983. The path of totality begins in the Indian Ocean, passes over many of the islands of Indonesia and ends in the Coral Sea. The duration of totality is maximum near Java where weather prospects are also quite favourable. Local circumstances are examined in detail, presenting predictions for 34 cities on the island. A consideration of lunar-shadow geometry is given to clarify some of the confusion concerning the advantages of observing from the centre line. A comparison of the present predictions with those of the U.S. Naval Observatory reveals some differences which could have important implications for observers.

Espenak, F.↗
NASA NTRS1984

The 1982 eclipse of 31 Cygni

UBV photometry and optical-UV spectroscopy of the primary eclipse of the long period Zeta Aurigae-like system 31 Cygni are reported. The precise timings made possible by the photometry imply that the spectral features could be due to an accretion shock associated with a hot star embedded in an extended chromosphere surrounding the red supergiant. The data also suggest an extended clumpy structure to the atmosphere of the late-type supergiant in the binary.

Hopkins, J. L.↗