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Soberman, R. K.

Publications and source records attributed to Soberman, R. K..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1995

Generation of Venus' nightside ionospheric structure by particle streams from cosmoids

A newly discovered source of energetic particle streams directed at Venus' nightside may cause several exosphere phenomena. The streams evolve from dispersed cosmoids, a surreptitious population of meteoroids in nearly hyperbolic orbits, measured with three dust experiments on Pioneer 10/11. Loose fragile comet-like ensembles of frozen volatile material, they are orders of magnitude more populous than short-period meteoroids. Dispersion is forced near a planet masking the meteor signature at Earth, but recently terrestrial exosphere interactions have been detected principally from VLF radar returns and as suddenly formed layers of neutral sodium and iron probed by lidar. Venus influx is estimated greater than 10(exp -14)(g)/((sq cm)(s)) with nightside directed kinetic power of greater than 0.3 (erg)/((sq cm)s)). Compared to Earth, Venus, lacking a dipole field with almost no rotation, has a readily recognized set of nightside interaction signatures of these downward energetic particle streams: i.e., density depressions of the neutral thermosphere, hydrogen and helium bulges, a non-disappearing ionosphere, electron holes, nightglows, VLF bursty signals, and local magnetic fields. From Pioneer Venus Orbiter (PVO) measurements, the cosmoid population, its temporal and solar azimuthal variation may be determined.

Dubin, M.↗
NASA NTRS1991

Cosmoids - Solution to the Pioneer 10 and 11 meteoroid measurement enigma

Experimental results from the three dust experiments on the Pioneer 11 and 12 spacecraft are used here to define the distribution and structural characteristics of what is believed to be the dominant population of meteoroids in the inner solar system. No two experiments agreed on the dust distribution and only the Imaging Photopolarimeter experiment could be fitted to the prevailing model of dust spiraling inward from the asteroid belt. Meteoroid Detection Experiment data showed a nearly constant flux from 1 to 18 AU. Reexamination of Asteoroid/Meteoroid Experiment or 'Sisyphus' data shows that the instrument measured a population of long-period meteoroids called cosmoids, composed mainly of water which dominates the dust distribution. Once the prevailing short period dust model is discounted, the results from the three instruments are shown to agree.

Dubin, Maurice↗
NASA NTRS1976

Results of the asteroid-meteoroid particle experiment on Pioneer 11

The Asteroid-Meteoroid Detector, an electro-optical instrument that detects and measures particles in space by sensing the sunlight reflected from them, is part of the payload of both the Pioneer 10 and 11 spacecraft. The Pioneer 11 instrument is essentially identical to that on Pioneer 10, with some minor modifications. Reduction of the Pioneer 11 data was complicated by the failure of one of the four sensor channels at about 1.1 AU from the sun. Detailed analysis yielded 51 events between 1.0 and 3.5 AU, which were used to determine the particle concentration distribution in that region of space. Weighted curve-fitting of the results shows agreement with the concentrations derived from Pioneer 10 to within about a factor of two. As with the Pioneer 10 results, the exponent of the size dependency varies from about -1.7 for 100-micron radius particles to about -3.2 for 10-cm bodies. The instrument, its operation, and the method of data analysis are reviewed.

Soberman, R. K.↗
NASA NTRS1974

Optical measurement of interplanetary particulates from Pioneer 10

The spatial concentration and size distribution for particulates measured in situ by the asteroid/meteoroid detector on Pioneer 10 between 1.0 and 3.5 AU are presented. The size distribution includes particles of radii from about 35 microns to 10 cm. Extrapolation from the smallest particle sizes measured shows good agreement with the results of the particle penetration detector carried on the same spacecraft. Within the uncertainties of this experiment, a single size distribution seems appropriate for all but the smallest particles measured. There is evidence for the existence of a planetary sweeping effect in the vicinity of the Mars orbit. As calculated from the particle spatial distribution, the zodiacal light brightness is found to vary approximately as the inverse square of solar distance out to about 2.25 AU and then decrease more rapidly. The absolute value of the zodiacal light brightness as calculated from the particle spatial concentration is found to be too high by a factor of 10.

Soberman, R. K.↗
NASA NTRS1974

Particle concentration in the asteroid belt from Pioneer 10

The spatial concentration and size distribution for particles measured by the asteroid/meteoroid detector on Pioneer 10 between 2 and 3.5 AU are presented. The size distribution is from about 35 micrometers to 10 centimeters. The exponent of the size dependence varies from approximately -1.7 for the smallest to approximately -3.0 for the largest size measured.

Soberman, R. K.↗
NASA NTRS1974

The Sisyphus particle detector

The particle measurement subsystem planned for the MJS 77 mission is described. Scientific objectives with respect to Saturn's rings are as follows: (1) measure particles outside the visible rings, including particulates orbiting in more distant rings and particles scattered out of visible rings, (2) measure meteoroid environment in vicinity of Saturn, and (3) develop an understanding of the dynamics of the rings with respect to their collisional interaction with the environment.

Soberman, R. K.↗
NASA NTRS1974

Results of the asteroid/meteoroid particle experiment on Pioneer 10 /1.0-3.3 AU/

The asteroid/meteoroid detector (Sisyphus), an optical array to measure particle size and orbit, has been performing successfully on Pioneer 10 since it was initially activated on 9 March 1972. During the first ten months of operation over 200 meteoroid and asteroid events were detected between 1.0 and 3.3 AU. These events are being analyzed to determine the spatial concentration as a function of heliocentric distance. The early results of these analyses are presented with particular emphasis on the distribution in the asteroid belt. Preliminary orbital parameters for some particles which have been analyzed are presented with a discussion of instrumental limitations.

Neste, S. L.↗
NASA NTRS1974

The radial dependence of the zodiacal light

The asteroid/meteoroid detector (Sisyphus) has, in addition to its primary role of detecting and analyzing individual meteoroids, been used for measuring the brightness of the night sky from its platform on board the Pioneer 10 spacecraft. This spacecraft has traversed the asteroid belt and will fly by Jupiter in December 1973. It was quickly found that the brightness of the night sky in the antisolar hemisphere decreased rapidly with increasing distance from the sun. This decrease is due solely to the decrease in the brightness of the zodiacal light. The heliocentric dependence of the zodiacal light has been deduced from several months of data. Some data are shown to illustrate the sensitivity of the instrument to features in the night sky and the technique used for subtracting out the integrated brightness due to starlight is described. Preliminary results showing the decrease of the zodiacal light with solar distance is not inconsistent with an inverse square dependence.

Zook, H. A.↗
NASA NTRS1973

Early results of Pioneer 10 particulate experiments.

On March 2, 1972 the Pioneer 10 spacecraft was launched on an interplanetary trajectory to encounter Jupiter late in 1973. The spacecraft carries four experiments designed to measure interplanetary particulates in a wide range of sizes from submicron to millimeter diameters. One experiment measures individual particulates by reflected sunlight. Two measure the aggregate particulates by scattered sunlight, while the fourth measures penetrations caused by individual particles. All have been collecting data from one to beyond four astronomical units. The data includes the first in situ measurements of small particulates in the Asteroid Belt. The results of the early analyses will be presented with particular emphasis on the distribution in the Asteroid Belt and its comparison to the interplanetary particulate distribution between the orbits of Earth and Mars.

Soberman, R. K.↗
NASA NTRS1971

Earth orbiting Sisyphus system study

The feasibility of employing an optical meteoroid detecting system, known as Sisyphus, to measure the near-earth particulates from an earth orbiting vehicle, is considered. A Sisyphus system can discriminate between natural and man-made particles since the system measures orbital characteristics of particles. A Sisyphus system constructed for the Pioneer F/G missions to Jupiter is used as the baseline, and is described. The amount of observing time which can be obtained by a Sisyphus instrument launched into various orbits is determined. Observation time is lost when, (1) the Sun is in or near the field of view, (2) the lighted Earth is in or near the field of view, (3) the instrument is eclipsed by the Earth, and (4) the phase angle measured at the particle between the forward scattering direction and the instrument is less than a certain critical value. The selection of the launch system and the instrument platform with a dedicated, attitude controlled payload package is discussed. Examples of such systems are SATS and SOLRAD 10(C) vehicles, and other possibilities are AVCO Corp. S4 system, the OWL system, and the Delta Payload Experiment Package.

Jurkevich, I.↗