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Thompson, T. W.

Publications and source records attributed to Thompson, T. W..

At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Lava flows in Mare Imbrium - An evaluation of anomalously low earth-based radar reflectivity

The surface of Mare Imbrium contains some of the most distinct red-blue colorimetric boundaries and depolarized 70-cm wavelength-reflectivity variations on the near side of the moon. The weakest levels of both 3.8-cm and 70-cm reflectivity within Imbrium are confined to spectrally blue regional mare surfaces that can be recognized as stratigraphically unique flow surfaces. Frequency distributions of the 70-cm polarized and depolarized radar-return power for five mare surfaces within the basin indicate that signal absorption, and probably ilmenite content, increases generally from the beginning of the Imbrium Period to the end of the Eratosthenian Period with slight reversal between the end of the Imbrium and beginning of the Eratosthenian. TiO2 calibrated radar-reflectivity curves can be utilized for lunar-maria geochemical mapping in the same manner as the TiO2 calibrated spectral-reflectivity curves of Charette et al. (1974).

Schaber, G. D.↗
NASA NTRS1975

The U.S. SEASAT program

The SEASAT program is a space-based operational oceanographic measurement system, which will be capable of providing continuous, all-weather, world-wide, timely data on global ocean dynamics and other physical properties of practical importance to a wide community of governmental and private sector users. This paper describes user requirements, case studies of projected applications, the sensor systems employed, and testing programs.

Mccandless, S. W.↗
NASA NTRS1974

The mapping of lunar radar scattering characteristics

This is the first of four articles describing a comprehensive series of radar maps of the entire visible lunar hemisphere carried out at wavelengths of 3.8 and 70 cm and analyzing the echoes in both orthogonal senses of circular polarization. In this paper, the basic techniques of delay-Doppler mapping by radar are developed, and the particular steps employed in mapping the moon are outlined. Succeeding articles present the results obtained and discuss the way in which these results relate to other, nonradar measurements as well as to the actual lunar surface properties.

Pettengill, G. H.↗
NASA NTRS1974

Atlas of lunar radar maps at 70-cm wavelength

The intensity distribution of lunar radar echoes has been mapped for two-thirds of the earth-visible lunar surface at a wavelength of 70 cm. The depolarizing effects of the lunar surface were observed by simultaneously receiving the radar echoes in opposite polarizations. These echoes were mapped with areal resolutions of 25-100 sq km. Mapping with this resolution confirmed that the young craters have enhanced returns. A few craters were found to have enhanced echoes only from their rims. Backscattering differences were also observed between various areas within a mare, between different highland areas, and between maria and adjacent highlands. These scattering differences were interpreted with a simple model, which assumed that the surface backscattered with varying amounts of quasi-specular and diffuse power. Only an increase in the diffuse power was needed to give the numerical values of the enhancements.

Thompson, T. W.↗
NASA NTRS1974

A comparison of infrared, radar, and geologic mapping of lunar craters

Between 1000 and 2000 infrared (eclipse) and radar anomalies have been mapped on the nearside hemisphere of the moon. A study of 52 of these anomalies indicates that most are related to impact craters and that the nature of the infrared and radar responses is compatible with a previously developed geologic model of crater aging processes. The youngest craters are pronounced thermal and radar anomalies; that is, they have enhanced eclipse temperatures and are strong radar scatterers. With increasing crater age, the associated thermal and radar responses become progressively less noticeable until they assume values for the average lunar surface. The last type of anomaly to disappear is radar enhancement at longer wavelengths. A few craters, however, have infrared and radar behaviors not predicted by the aging model. One previously unknown feature - a field strewn with centimeter-sized rock fragments - has been identified by this technique of comparing maps at the infrared, radar, and visual wavelengths.

Thompson, T. W.↗
NASA NTRS1974

Mare Serenitatis - A preliminary definition of surface units by remote observations

Mare Serenitatis is a ringed mare about 600 km in diameter situated in the northeast quadrant of the moon. The floor of the mare is comprised of several units. Remote observations of Mare Serenitatis are presented. Color difference photographs were produced by photographing the moon at two wavelength bands. Radar images were obtained by delay-Doppler mapping of radar echoes. The definition of surface units is discussed together with surface properties obtained from remote observations.

Thompson, T. W.↗
NASA NTRS1973

Mission planning for remote exploration of the surface of Venus.

A science rationale for exploration of the surface of Venus by remote means together with the role of science goals in mission planning is presented. Specific attention is devoted to radar imagery. Earth-based radar images will provide 60% coverage with resolution at 10-km or better surface resolution are anticipated by 1980. A Venus orbiting imaging radar system could map 100% of the surface at 200 meter surface resolution and 3 to 6% at 40 meters or less. Such coverage and resolution are essential for identification of surface processes and for evaluation of lander observations in a planet-wide context. By deduction of surface observation goals, objectives for a Venus orbiter mission are derived and placed in a comprehensive Venus exploration program. The characteristics of such a mission are briefly discussed.

Saunders, R. S.↗
NASA NTRS1973

Remote sensing of Mare Serenitatis

An examination was made of earth based observations of optical color differences, infrared eclipse temperatures, and radar backscatter for Mare Serenitatis. Information is also included on orbital observations, physical properties of surface types, and correlation of surface types with geologic units. Differences in these remote observations are attributed to variations in chemical and minerological compositions.

Thompson, T. W.↗
NASA NTRS1972

Lunar topography - Global determination by radar.

Previous methods used for two-dimensional radar mapping of the moon are contrasted with new techniques that add altitude information to the radar map. Delay-Doppler stereoscopy and delay-Doppler interferometry are shown to provide surface-height variations with higher accuracy and better global fidelity than has been possible previously. Sample results are presented for altitude contours on the moon as obtained with the Haystack and Westford radar systems of the Massachusetts Institute of Technology. An appendix describes the mathematical principles of delay-Doppler interferometry in determining the position of an arbitrary reflecting region of the lunar surface from measurements of the time delay, Doppler shift, and fringe phase of radar echoes from that region.

Shapiro, I. I.↗
NASA NTRS1972

Radar mapping of lunar surface roughness.

Comparison of anomalous behavior at infrared and radar wavelengths provides an estimation of lunar surface structure at centimeter-to-meter sizes. Although a simple classification is used, it is shown that the combination of the infrared and radar data contains more information than any of the sets by themselves. The infrared data indicate that bare surface rocks are the source of the roughness which generates enhanced radar backscatter. The different radar maps indicate the size of surface rocks, as was demonstrated for the strewn fields of centimeter-sized rubble (the Type II anomaly). As craters age, they have a rim-bright appearance in the radar maps, and eventually lose their anomalous-behavior at infrared and 3.8-cm radar wavelengths.

Thompson, T. W.↗
NASA NTRS1972

Apollo 16 landing site: Summary of earth based remote sensing data, part W

Infrared and radar studies of the Apollo 16 landing site are summarized. Correlations and comparisons between earth based remote sensing data, IR observations, and other data are discussed in detail. Remote sensing studies were devoted to solving two problems: (1) determining the physical difference between Cayley and Descartes geologic units near the landing site; and (2) determining the nature of the bright unit of Descartes mountain material.

Zisk, S. H.↗