SARAL/AltiKa is the world’s first satellite equipped with a Ka-band (35.75 GHz) altimeter for the measurement of ocean levels.

Launched on 25 February 2013, the SARAL/AltiKa satellite is a joint French-Indian project focusing on environmental observation and monitoring. The satellite bus, which was developed by the Indian space agency, carries two independent instruments—ARGOS-3 and AltiKa. ARGOS-3 is the third-generation receiver of the Argos system, allowing the localisation and collection of environmental data from any ‘object’ equipped with an Argos transmitter, from mud drifts to turtles, birds and so on.

AltiKa is a ground-breaking payload that incorporates an altimeter, a radiometer and a DORIS positioning instrument. It measures ocean surface topography using a very high electromagnetic wave frequency—the Ka band (around 35.75 GHz instead of the previous 13.6 GHz). Developed for CNES by Thales Alenia Space, the AltiKa altimeter provides improved ground resolution, giving better access to coastlines and to continental rivers and lakes. It also penetrates less deeply into snow and ice, thereby enabling the collection of information about their surface levels. So in addition to contributing to the mesoscale (50 to 500 km) ocean current observations that are essential to our understanding of ocean dynamics and their impact on the climate, AltiKa data is also widely used by glaciologists and hydrologists.

Placed in the same orbit as the ENVISAT satellite (polar orbit at 800 km altitude), the SARAL/AltiKa satellite permits continuous monitoring of the long series of temporal data required for studying climate change. AltiKa data is also used in operational oceanography and on a daily basis by the Copernicus Marine Environment and Monitoring Service and by the French and European meteorological agencies.