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INTERPRETATION OF REMOTE SENSING DATA FOR PLANETARY TOPOGRAPHIC MAPPING
by
Dr. Sherman S. C. Wu
United States Geological Survey
Flagstaff, Arizona U. S. ^.
Remote sensing data from devices using a broad spectrum of wavelengths
have been applied in planetary topographic mapping. A global topographic map
of Mars was compiled by the synthesis of remotely sensed data from various
scientific experiments on board the Mariner 9 spacecraft and from earth-based
radar observations. Mars topographic information is derived from surface
pressure, surface temperature, and absorption of CO,, which are acquired
respectively by the ultraviolet spectrometer (UVS), the infrared radiometer
(IRR), and the infrared interferometer spectrometer (IRIS). The S-band radio-
occultation experiment determines radii of Mars at both the entry and the exit
points of a spacecraft occultation. Topographic profiles of Mars are
calculated from radar signal time delay, i.e., the travel time to and from
Mars is associated with topographic reliefs on the martian surface. The
precision of the relative height measurements from radar is better than
200 m. Contour lines of Mars maps are also compiled by photogrammetric
methods using Martian pictures. The Mars topographic datum, the O-elevation
reference surface is defined by its gravity field which was established from
gravity data, also collected by radio tracking of Mariner 9. Mars is
currently being systematically mapped in great detail using Viking Orbiter
pictures.
A global topographic map of the Moon is being compiled using topographic
information derived from a variety of remote sensing data which includes
Apollo and Lunar Orbiter photographs, laser altimeter data, lunar radar
sounders and earth-based observations. By using radar altimeter data
transmitted from the Pioneer Venus spacecraft, a preliminary global
topographic map of Venus has been compiled. For the compilation of more
detailed maps of Venus, the technology of using side-looking radar stereo
images from the proposed VOIR mission (Venus Orbiter Imaging Radar) is under
development.
Along with the presentation of global maps of Mars, the Moon and Venus,
techniques of data processing of remote sensing data and methods of map
compilation are discussed.
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