The Jason-CS Mission
Francis, Richard1; Parisot, François2; Coutin-Faye, Sophie3; Peter, Wilczynski4; Parag, Vaze5

The Jason-CS Mission is conceived as the successor to the long standing series of missions dedicated to measurement of the ocean surface height, starting with TOPEX-Poseidon in 1992 and continuing to Jason-2 in orbit, with Jason-3 due to be launched in 2015. This unbroken record will be continued up to at least 2030 with a pair of Jason-CS satellites. These missions operate from a relatively high altitude prograde orbit with an inclination of 66 degrees. The repeat period is 10 days, so to provide a complete picture of the ocean surface, including mesoscale features, it is necessary to combine the measurements with a high inclination mission (typically but not necessarily sun-synchronous) with a longer repeat cycle, or order a month. This combination has been continuously available, first with ERS-1 and -2, then with EnviSat and now with CryoSat as the only mission able to fill this role until the launch of CNES's AltiKa altimeter on SARAL expected in February 2013, and then with the operational Sentinel-3 satellites. Jason-CS is in fact built on the heritage of CryoSat. This ice mission was specifically designed to meet the requirements of altimetry measurements from a non sun-synchronous orbit. The payload complement needs to be enhanced for the so-called reference mission, notably with the addition of a microwave radiometer and additional POD capabilities using a GNSS receiver. Some of these new payload instruments are produced by JPL and provided by NOAA, following on from the previous Jason missions. But Jason-CS will provide a new generation of measurement capability compared to the previous Jasons. It will use the SAR principle of CryoSat's SIRAL radar, but further enhanced to allow simultaneous SAR measurements and data collected in the more traditional pulse-width limited mode. To capitalise on this new high resolution altimetry, a new high-resolution microwave radiometer (operating at high frequencies) is now under study, to augment the standard radiometer. Continuing work on the Jason-CS mission was approved at the ESA Council at Ministerial Level, held in November 2012, and this will allow the work to reach the level, by mid-2014, where the implementation can start, subject to further approval. In parallel, the approval process in the partner agencies is underway, with the intention of launching the first Jason-CS at the end of 2018.