衛星アルティメトリィと衛星重力ミッション Satellite Altimetry and Satellite Gravity Missions
This paper reviews satellite altimetry mainly from a geodetic and oceanographic point of view; discusses the relationship between satellite altimetry and gravity missions; besides it gives a preview of the gravity missions and their meaning in the study of the Earth's sciences. Satellite altimetry is a technique for measuring sea surface heights from a satellite orbit using a microwave radar altimeter. This technique has brought about a revolution in the study of marine gravity fields, and then in the oceanographic studies. With the sea surface being a good approximation of the geoid, sea surface heights measured by satellite altimeter are con sidered to be approximate geoid heights. On the other hand, there exist small differences between sea surface and geoid heights. The differences are referred to as sea surface dynamic heights which are caused by the ocean currents. Therefore absolute current flux could be de tected by satellite altimetry, if precise geoid is determined independently from satellite altimeter data, This is the main reason why a precise oceanic geoid has been desired for a longperiod of time by oceanographers. All the satellite gravity missions which were planed late 1980's and early 1990's aimed at the improvement of the accuracy of static gravity fields. Compared with these missions, GRACE has a rather different concept. Very accurate measurements by GRACE will be expected to reveal not only precise static gravity fields, but also the temporal variations of the gravity fields. GRACE aims, for the first time in history, to ob serve various mass movements which occur in, on and above the Earth's surface as gravity changes. There is no doubt coming satellite gravity missions will bring about revolution in the studies of the Earth's sciences.
測地学会誌 46(1), 53-67, 2000-03-25
The Geodetic Society of Japan