CoAuthors

Walter Smith (NOAA, USA); David Sandwell (SIO, USA); Gerald Dibarboure (CNES, France); Hugh Harper (SIO, USA); Alejandro Egido (NOAA, USA); Adili Abulaitijiang (DTU Space, Denmark)

In July 2017 Jason-2 was put in a End-of-Life orbit the so-called GM/LRO orbits. The design of the orbit was such that after approximately 2 cycles or a little more than 2 years complete coverage with a equal track spacing of 4 km across track would be achieved to the huge benefit of marine geodesy. The optimal Jason-2 LRO orbit was chosen to be 27 km lower than the nominal orbit and designed to have a fallback geodetic sub-cycle of approximately 145 days. This sub-cycle was selected as a "coarse geodetic grid", i.e. as a safety net if full geodetic cycles cannot be completed. The strategy was inherited from Jason-1 EoL trying to optimize all sub-cycles to make it valuable to oceanography as well (shorter ones for sea-state and mesoscale, and longer ones for geodesy).
The first GM/LRO cycle was completed in summer of 2018. During the first cycle safe-hold modes created a small set of 8-km gaps that are sometimes next to the ongoing and incomplete 145-day sub-cycle. Approximately 13% of the data have been lost to safe hold modes. It has been decided not to try to fill in these safehold-gaps but to continue into the second cycle trying to maximize the number of good data that can be achieved before Jason-2 cease functioning.
In this presentation we analyze the first cycle of Jason-2 GM/LRO data and the importance of these for marine gravity field modelling. The Jason-2 waveforms should be superior to the Jason-1 waveforms and we analyse the effect on this for gravity field modelling.
Since 2016 SARAL/AltiKa is in a uncontrolled geodetic orbit. Along with the Cryosat-2 recently completing its eight’ 369 days cycle we will try to quantify how these missions complement each other in order to create the next generation high resolution global marine gravity field.