Precise satellite altimetry missions have transformed the way we view Earth and its oceans. Highly accurate altimetry measurements give us the ability to observe sea surface height systematically.

The earliest altimeters were intended to demonstrate proof of concept. With Seasat (1978), the first scientific results were shown. Since 1986 (Geosat), these missions have been providing vital information for an international user community. Besides international programs dedicated to studying global oceans and climate, such as WOCE, WCRP, Clivar and GOOS, and others working on the El Niño phenomenon (TOGA), ocean forecasting projects such as GODAE are now getting underway. All these programs call for high-quality altimetry measurements, which are merged with other data to obtain the broadest picture possible of the underlying mechanisms at work, and assimilated into ocean and climate prediction models.

Past altimetry missions

Current altimetry missions

 

Future missions altimetry missions

 

Satellite Agency Launch Altitude Altimeter Frequency used Repetitivity Inclination Error budget
(Open ocean)
Skylab
skylab_mini
NASA 1973 435 km S193 ? 50° Range: 1 m;
Orbit: ~500 cm
GEOS 3
geos3_mini
NASA 1974 845 km ALT 115° Range: 25 cm;
Orbit: ~500 cm
Seasat
seasat_mini
NASA 1978 800 km ALT Ku-band 17 days? 108° Range: 5 cm;
Orbit: ~100 cm
Geosat
geosat_mini
US Navy 1985 800 km Ku-band 17 days 108 Range: 4 cm;
Orbit: 30-50 cm
ERS-1
ers_mini
ESA 1991 785 km RA Ku-band 35 days
(3 days ice phase,
168 days geodetic phase)
98.5° Range: 3 cm;
Orbit: 8-15 cm
Topex/
Poseidon
tp_mini
NASA /
CNES
1992 1336 km Topex
Poseidon-1
Ku and C-band
Ku-band
10 days 66° Range: 2 cm;
Orbit: 2-3 cm
ERS-2
ers_mini
ESA 1995 785 km RA Ku-band 35 days 98.5° Range: 3 cm;
Orbit: 7-8 cm
GFO
gfo_mini
US Navy /
NOAA
1998 800 km GFO-RA Ku-band 17 days 108° Range: 3.5 cm;
Orbit: ? cm
Jason-1
jason_mini
CNES /
NASA
2001 1336 km Poseidon-2 Ku and C-band 10 days 66° Range: 2 cm;
Orbit: 2-3 cm
Envisat
envisat_mini
ESA 2002 800 km RA-2 Ku and S-band 35 days 98.5° Range: 2-3 cm ;
Orbit: 2-3 cm
Jason-2
jason_mini
CNES /
NASA /
Eumetsat /
NOAA
2008 1336 km Poseidon-3 Ku and C-band 10 days 66°
Cryosat
cryosat_mini
ESA 2008 720 km SIRAL Ku-band 369 days 92°
HY-2 China 2010 963 km Ku and C-band 99.3°
Saral ISRO /
CNES
2013 800 km AltiKa Ka-band 35 days 92°
Sentinel 3 ESA 2016 814 km SRAL Ku and C-band 27 days 98.5º
Jason-3 CNES /
NASA /
Eumetsat /
NOAA
2016 1 336 km Ku and C-band 66°