047.doc
ALTIMETER METHODS FOR SATELLITE GEODESY
C.K. Shum, Laboratory for Space Geodesy and Remote Sensing Research, Department of
Civil and Environmental Engineering and Geodetic Science, The Ohio State University,
2070 Neil Avenue, Columbus, Ohio 43210-1275, USA. Tel: 614-292-7118; Fax: 614292-2957; Email: ckshum@osu.edu
Spaceborne satellite radar altimeters have demonstrated their abilities to provide global
synoptic measurements of the sea surface topography with a temporal sampling of weeks
and approaching an absolute accuracy of 3-4 cm rms. There are currently five operating
spaceborne radar altimeters (TOPEX/POSEIDON, ERS-2, GFO, Jason and ENVISAT),
and historic missions well (Geos-3, Seasat, Geosat, and ERS-1). TOPEX/POSEIDON
(T/P) represents the first satellite mission dedicated to the measurement of the large-scale
global ocean circulation. Since then, stringent accuracy requirements placed on the T/P
have also been realized in the new missions for precision orbit determination, reference
frame stability, and altimeter instrument system. The design and precise computation of
the T/P orbit allows the use of the altimetric measurements to provide the most
significant advances in the prediction of the ocean tides in the last century. Accuracy of
T/P altimetry (its orbits and reference frames) enables establishment of absolute vertical
datum for combination with other altimeters, and for the long-term measurement of
global mean sea level variations. The geodetic phases of altimetric missions (Geosat and
ERS-1) have allowed unprecedented improvement in the spatial resolution (>25 km
resolution at equator) and accuracy of models of the mean sea surface, marine geoid, and
predicted bathymetry. Direct and indirect, single- and multiple-satellite crossovers, use
of altimeters enable a powerful determination of the Earth’s gravity field model. ERS-1
and ERS-2 radar altimeters have been providing measurements of inner ice sheet
topography and its changes. Finally, accurate and long-term altimetry is a critical
component for the combination with the gravity mapping mission measurements from
CHAMP, GRACE, and GOCE to potentially separate thermal expansion of the ocean
from oceanic mass redistribution towards quantification of ocean’s role in global climate
change.
Oral or Poster Presentation
Geodesy