The Shuttle Radar Topography Mission produced the most complete, highest‐resolution digital elevation model of the Earth. The project was a joint endeavor of NASA, the National Geospatial‐Intelligence Agency, and the German and Italian Space Agencies and flew in February 2000. It used dual radar antennas to acquire interferometric radar data, processed to digital topographic data at 1 arc sec resolution. Details of the development, flight operations, data processing, and products are provided for users of this revolutionary data set.

On February 22, 2000, the Space Shuttle Endeavour landed at Kennedy Space Center, completing the highly successful 11‐day flight of the Shuttle Radar Topography Mission (SRTM). Onboard were over 300 high‐density tapes containing data for the highest resolution digital topographic map of Earth ever made. SRTM is a cooperative project between the National Aeronautics and Space Administration (NASA) and the National Imagery and Mapping Agency (NIMA) of the U.S. Department of Defense. The mission was designed to use a single‐pass radar interferometer to produce a digital elevation model (DEM) of the Earth's land surface between about 60 north and 56 south latitude. When completed, the DEM will have 30‐m pixel spacing and about 15‐m vertical accuracy. Two ortho‐rectified image mosaics, one from the ascending passes with illumination from the southeast, and one from descending passes with illumination from the southwest, will also be produced (Figure 1).

ABSTRACT:NASADEM is a near-global elevation model that is being produced primarily by completely reprocessing the Shuttle Radar Topography Mission (SRTM) radar data and then merging it with refined ASTER GDEM elevations. The new and improved SRTM elevations in NASADEM result from better vertical control of each SRTM data swath via reference to ICESat elevations and from SRTM void reductions using advanced interferometric unwrapping algorithms. Remnant voids will be filled primarily by GDEM3, but with reduction of GDEM glitches (mostly related to clouds) and therefore with only minor need for secondary sources of fill.

ABSTRACT:NASADEM is a near-global elevation model that is being produced primarily by completely reprocessing the Shuttle Radar Topography Mission (SRTM) radar data and then merging it with refined ASTER GDEM elevations. The new and improved SRTM elevations in NASADEM result from better vertical control of each SRTM data swath via reference to ICESat elevations and from SRTM void reductions using advanced interferometric unwrapping algorithms. Remnant voids will be filled primarily by GDEM3, but with reduction of GDEM glitches (mostly related to clouds) and therefore with only minor need for secondary sources of fill.

A model of Venusian global topography has been obtained by fitting an eighteenth‐degree harmonic series to Pioneer Venus orbiter radar altimeter data. The mean radius is (6051.45±0.04) km. The corresponding mean density is (5244.8±0.5) kg m−3. The center of figure is displaced from the center of mass by (0.339±0.088) km towards (6.6±10.1)°N, (148.8±7.7)°E. The figure of Venus is distinctly triaxial, but the orientation and magnitudes of the principal topographic axes correlate rather poorly with the gravitational principal axes. However, the higher‐degree harmonics of topography and gravity are significantly correlated. The topographic variance spectrum of Venus is very similar in form to those of the moon, Mars, and especially Earth. We suggest that this spectral similarity simply reflects a statistical balance between constructional and degradational geomorphic processes. Venus and Earth are particularly similar (and differ from the moon and Mars) in that the larger bodies both exhibit a significant low degree‐deficit (relative to the extrapolated trend of the higher harmonics).