4. Missions

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

The first altimetric satellites : Skylab, GEOS 3, Seasat
Geosat
ERS-1
Topex/Poseidon

Current altimetry missions

Future altimetry missions

Jason-2
Cryosat
(AltiKa) (name of mission to be defined)
NPOESS
Sentinel 3
See also future technology improvements

Satellite	Agency	Launch	Altitude	Altimeter	Frequency used	Repetitivity	Inclination	Error budget
Skylab	NASA	1973	435 km	S193		?	50°	Range: 1 m; Orbit: ~500 cm
GEOS 3	NASA	1974	845 km	ALT			115°	Range: 25 cm; Orbit: ~500 cm
Seasat	NASA	1978	800 km	ALT	Ku-band	17 days?	108°	Range: 5 cm; Orbit: ~100 cm
Geosat	US Navy	1985	800 km		Ku-band	17 days	108	Range: 4 cm; Orbit: 30-50 cm
ERS-1	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	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	ESA	1995	785 km	RA	Ku-band	35 days	98.5°	Range: 3 cm; Orbit: 7-8 cm
GFO	US Navy / NOAA	1998	800 km	GFO-RA	Ku-band	17 days	108°	Range: 3.5 cm; Orbit: ? cm
Jason-1	CNES / NASA	2001	1336 km	Poseidon-2	Ku and C-band	10 days	66°	Range: 2 cm; Orbit: 2-3 cm
Envisat	ESA	2002	800 km	RA-2	Ku and S-band	35 days	98.5°	Range: 2-3 cm ; Orbit: 2-3 cm
Jason-2	CNES / NASA / Eumetsat / NOAA	2008	1336 km	Poseidon-3	Ku and C-band	10 days	66°
Cryosat	ESA	2009	720 km	SIRAL	Ku-band	369 days	92°
TBD	ISRO / CNES	2009	TBD	AltiKa	Ka-band	TBD	TBD

	URL: http://www.altimetry.info/html/missions/welcome_en.html