History of Radar Altimeters
First flown on Skylab
Then Seasat launched in 1978, which lasted 90 days
GEOSAT Geodetic Mission
- 3 day near repeat ground tracks
- Mar 85 to Sept 86 (18 months)
- Average track separation 4 km
- Created a gravity model and Geoid, useful for
- Originally classified data, released in stages starting
with the far southern latitudes. All data released when European
altimeter created an equivalent geoid.
GEOSAT Exact Repeat Mission
- 17 day exact repeat
- 244 equatorial node crossings
- equatorial ground track separation 164 km. This spacing does not
allow creation of an accurate geoid.
- Primary goal to monitor currents and eddies (ocean weather), wave
heights, and wind speeds.
- Nov 86 to Dec 1989
TOPEX/Poseidon: joint NASA French satellite
- 10 day exact repeat. In a 10 day period, the ocean dynamic
topography does not change appreciably, however the wind speed and wave
height might as atmospheric weather systems pass.
- 1336 km altitude
- equatorial ground track separation about 300 km at equator (much
less near poles)
- There is a reading along track approximately every 6 km or every second
- 254 passes in 127 orbits
JASON follow-on to TOPEX
- Jason-1 had a 14 month geodetic phase, with 7.5 km track spacing
- 4 years in orbit, track spacing abut 2.5 km
Last revision 4/9/2016