SARAL mission results from the common interest of both CNES and ISRO in studying ocean from space using altimetry system and in promoting maximum use of the ARGOS Data Collecting System. Radar altimetry by satellite is a technique used in oceanography to measure, globally over the oceans, the sea level needed to understand ocean circulation and its variability. The importance of altimetry data to better understand the ocean circulation and its impact on the climate of the Earth led to the TOPEX/Poseidon and Jason series of satellites complemented by ERS1-2, GFO and ENVISAT. With the launch of these missions began a data collection that must continue well into the century in order to monitor the inter-annual evolution and separate transient phenomena from secular variations.
SARAL/AltiKa mission belongs to the global altimetry system and then participates to the precise and accurate observations of ocean circulation and sea surface elevation for its life time.
Thus it is the aim of AltiKa part of the SARAL mission to provide altimetric measurements designed to study ocean circulation and sea surface elevation with the same accuracy as the one provided by ENVISAT mission and complementary to Jasons mission.
The AltiKa project developed by CNES is based on a large Ka-band altimeter (35.75 GHz, 500MHz), 1st oceanographic altimeter using such a high frequency. The use of the Ka-band frequency will supply more accurate measurements (improvement of the spatial and vertical resolution) enabling a better observation of ices, coastal areas, continental water bodies as well as the waves height. The drawback of this Ka-band frequency is its sensitivity to rain that can lead to signal attenuation.
The SARAL/AltiKa mission is part of the operational satellite altimetry system, jointly with Jason-2, and enables to ensure the service continuity which is nowadays provided by ENVISAT altimeter jointly with Jason-2 and Jason-1.
By ensuring the observations continuity and widening the observation areas, CNES answers the wish of the oceanography community by bringing a description:
- For the meso-scale in open ocean,,
- In coastal areas,
- For the seasonal forecast,
- For the hydrology,
- For the climate studies.
AltiKa data will thus contribute, along with data from others altimetry missions, to the development of operational oceanography, to our climate understanding and to the development of forecasting capabilities through data assimilation methods improvement in coupled oceanatmosphere coupling models, bio-chemistry models, etc.