| Instrument | Agency | Missions | Status | Type | Measurements &
applications | Technical characteristics |
ALT
Radar Altimeter | NSOAS (CAST) | Current: HY-2C, HY-2D
Future: HY-2E, HY-2F, HY-2G
Complete: HY-2A, HY-2B | Operational | Radar altimeters | Global ocean topography, sea level and gravity field measurements. |
| Waveband: | 13.58 GHz and 5.25 GHz
MW |
| Spatial resolution: | 16 km |
| Swath width: | 16 km |
| Accuracy: | < 4 cm |
| Data Access: | |
| Data Format: | |
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AltiKa
Ka-band Altimeter | CNES | Current: SARAL
Future: -
Complete: - | Operational | Radar altimeters | Sea surface height. |
| Waveband: | 35.5 - 36 GHz, passive channels (radiometer): 24 (K-band) and 37 (Ka-band) GHz; active radar altimeter: 35 GHz (Ka-band)
MW, Ka-Band, K-Band |
| Spatial resolution: | |
| Swath width: | |
| Accuracy: | |
| Data Access: | Open Access |
| Data Format: | |
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IRIS
Interferometric Radar Altimeter for Ice and Snow | ESA (EUMETSAT) (COM) | Current: -
Future: Sentinel CRISTAL-A, Sentinel CRISTAL-B
Complete: - | Approved | Radar altimeters | Ku-band Interferometric Synthetic Aperture Radar Altimeter (with added Ka-band channel for snow depth retrieval and in combination with AMR-CR MW Radiometer for ice&snow classification and wet troposphere correction) to cover the needs for continuous monitoring of sea ice
thickness and land ice elevation measurement after Cryosat-2, with enhanced performance. |
| Waveband: | Ku-band and Ka-band
Ka-Band, Ku-Band |
| Spatial resolution: | up to 0.5 m (along track resolution with fully-focused SAR processing). Various degrees of averaging depending on surface
Best resolution: 0.5 m |
| Swath width: | N/A |
| Accuracy: | Uncertainties ≤23 arcsec on Angle of Arrival; ≤3 cm on freeboard; ≤15 cm on sea ice thickness; ≤2 m on land ice surface elevation (≤0.5m for terrain with slope <0.2 degrees); ≤3.5 cm on sea surface height. |
| Data Access: | Open Access |
| Data Format: | |
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Ka-band Radar Interferometer (KaRIn)
Ka-band Radar Interferometer (KaRIn) | NASA (CNES) | Current: SWOT
Future: -
Complete: - | Operational | Radar altimeters | Swath mapping radar altimeter that provides measurements for surface water. |
| Waveband: | 35.75 GHz Center Freq / 200 MHz Bandwidth
MW, Ka-Band |
| Spatial resolution: | Vertical resolution is 2 cm |
| Swath width: | 50 km |
| Accuracy: | 8.2 cm height accuracy required |
| Data Access: | Open Access |
| Data Format: | |
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POSEIDON-3B Altimeter
Positioning Ocean Solid Earth Ice Dynamics Orbiting Navigator (Single frequency solid state radar altimeter) | CNES | Current: Jason-3
Future: -
Complete: - | Operational | Radar altimeters | Nadir viewing sounding radar for provision of real-time high precision sea surface topography, ocean circulation and wave height data. |
| Waveband: | Microwave: Ku-band (13.575 GHz), C-band (5.3 GHz)
Ku-Band, C-Band |
| Spatial resolution: | Basic measurement: 1/sec (6 km along track), Raw measurement: 20/sec (300 m along track)
Best resolution: 300 m |
| Swath width: | On baseline TOPEX/POSEIDON orbit (10 day cycle): 300 km between tracks at equator |
| Accuracy: | Sea level: 3.4 cm, Significant wave height: 0.4 m, Horizontal sea surface wind speed: 1.5 m/s |
| Data Access: | Open Access |
| Data Format: | NetCDF |
|
POSEIDON-3C Altimeter
Positioning Ocean Solid Earth Ice Dynamics Orbiting Navigator (Single frequency solid state radar altimeter) | NASA | Current: SWOT
Future: -
Complete: - | Operational | Radar altimeters | Nadir viewing sounding radar for provision of real-time high precision sea surface topography, ocean circulation and wave height data. |
| Waveband: | Microwave: Ku-band (13.575 GHz), C-band (5.3 GHz)
Ku-Band, C-Band |
| Spatial resolution: | Basic measurement: 1/sec (6 km along track), Raw measurement: 20/sec (300 m along track) |
| Swath width: | On baseline TOPEX/POSEIDON orbit (10 day cycle): 300 km between tracks at equator |
| Accuracy: | Sea level: 3.4 cm, Significant wave height: 0.4 m, Horizontal sea surface wind speed: 1.5 m/s |
| Data Access: | Open Access |
| Data Format: | NetCDF |
|
Poseidon-4 Altimeter
Poseidon-4 SAR Radar Altimeter | ESA (EUMETSAT) (NASA) (CNES) | Current: Sentinel-6 A Michael Freilich, Sentinel-6 B
Future: Sentinel-6 C
Complete: - | Operational | Radar altimeters | Nadir viewing sounding radar for provision of real-time high-precision sea surface topography, ocean circulation and wave height data. |
| Waveband: | Microwave: Ku-band (13.575 GHz), C-band (5.3 GHz)
Ku-Band, C-Band |
| Spatial resolution: | |
| Swath width: | On baseline TOPEX/POSEIDON orbit (10 day cycle): 300 km between tracks at equator. |
| Accuracy: | Sea level: 3.2 cm, Significant wave height: 0.15 m, Horizontal sea surface wind speed: 1.5 m/s |
| Data Access: | Open Access |
| Data Format: | NetCDF-4 |
|
Poseidon-5 Altimeter
Poseidon-5 SAR Radar Altimeter | ESA (EUMETSAT) (CNES) | Current: -
Future: S3NGT-A, S3NGT-B
Complete: - | Proposed | Radar altimeters | Nadir viewing sounding radar for provision of real-time high-precision sea surface topography, ocean circulation and wave height data. |
| Waveband: | Microwave: Ku-band (13.575 GHz), C-band (5.3 GHz)
Ku-Band, C-Band |
| Spatial resolution: | |
| Swath width: | On Sentninel-3 A&B tracks |
| Accuracy: | Sea level: 3.2 cm, Significant wave height: 0.15 m, Horizontal sea surface wind speed: 1.5 m/s |
| Data Access: | |
| Data Format: | |
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SAOOH
Swath Altimeter for Oceanography and Operational Hydrology | ESA (COM) | Current: -
Future: S3NGT-A, S3NGT-B
Complete: - | Proposed | Radar altimeters | Interferometric swath altimeter building on the heritage of the SWOT mission. It will enhance sampling coverage and performance of hydrology water surface elevation measurements. |
| Waveband: | Microwave Ka-band (35GHz)
Ka-Band |
| Spatial resolution: | |
| Swath width: | On Sentinel-3 A&B tracks |
| Accuracy: | Sea level: 3.2 cm, Significant wave height: 0.15 m |
| Data Access: | |
| Data Format: | |
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SIRAL
SAR Interferometer Radar Altimeter | ESA | Current: CryoSat-2 | Operational | Radar altimeters | Marine ice and terrestrial ice sheet thickness measurement. |
| Waveband: | Microwave: 13.575 GHz (Ku-Band)
MW, Ku-Band |
| Spatial resolution: | Range resolution 45 cm, along-track resolution 250 m |
| Swath width: | Footprint 15 km |
| Accuracy: | Arctic sea-ice: 1.6 cm/year for 300 km x 300 km cells, Land ice (small scale): 3.3 cm/year for 100 x 100 km cells, Land ice (large scale): 0.17 cm/year for Antarctica size area |
| Data Access: | Open Access |
| Data Format: | |
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