Satellite radar altimetry is a technique used in oceanography to measure sea level on a large scale. The data obtained is vital to understanding ocean circulation and its variations.

The AltiKa project, which was developed by CNES, is based on a wideband Ka-band altimeter (35.75 GHz, 500 MHz), which will be the first oceanography altimeter to operate at such a high frequency. This unique technical characteristic of the instrument will offer higher performance both in terms of spatial and vertical resolution. The instrument’s more accurate measurements will lead to improved observation of ice, coastal areas, inland waters and wave height .

The AltiKa project will contribute to operational satellite altimetry by providing round-the-clock data of an accuracy demanded by the user community. When combined with data from Jason-2, they will ensure the continuity of the service presently offered by the 'double act' comprising Jason-1 and Envisat's altimetry payload.

By guaranteeing uninterrupted observations and extending the coverage, CNES is responding to the oceanography community's needs for accurate tools for:

• better characterisation of the mesoscale ocean and coastal areas, 
• seasonal forecasting, 
• climate studies.

The high-resolution AltiKa altimeter has a dual-frequency radiometric function which allows the altimetry measurements to be corrected for the effects due to the signal passing through the wet troposphere. This is coupled with the Doris¹ precise orbit determination system, in association with a laser retro-reflector, which determines the satellite's precise position in orbit. This parameter is essential for measuring sea level.

AltiKa data, along with that from other altimetry missions, will thus play a major role in the development of operational oceanography and its forecasting capabilities, as well as improving our understanding of the climate.

Together with instruments from the Argos 3 mission, the AltiKa payload will be carried on the Saral² satellite, developed jointly with the Indian Space Agency (ISRO), which is providing the platform and overseeing satellite operations, including launch, orbit acquisition and station keeping. CNES is supplying the AltiKa payload and will be responsible for receiving and processing data using the SALP altimetry and precise location service.

The agreement signed by CNES and ISRO in February 2007 will reinforce the working relationship of the two Agencies. The Saral satellite, to be placed on Envisat's orbit, is scheduled for launch end of 2010.

_{1 Doppler Orbitography and Radiopositionning Integrated by Satellite
2 Satellite with ARgos & ALtika, or "simple" in Hindi}

_{Last updated : January 2009}