Credits CNES/CLS, MIT/GCM sampled with JPL simulator
Example of SWOT simulated data from the MIT-Global Circulation Model sampled by the JPL simulator.
The data represent the Absolute Sea Surface Height (in cm) over the Gulf Stream area. This animation integrates two cycles of 21 days so a total time lapse of 42 days. The contiguous ground tracks can be separated by several days in time, explaining the topography discontinuities looking like a patchwork. Products to end-users will integrate more processing like dynamic optimal interpolation in order to fill in temporal gaps and to have a continuous reconstruction.
The satellite Swot (Surface Water Ocean Topography) is envisioned for 2020 in a joint project including Nasa, Cnes, the Canadian Space Agency and the UK Space Agency.
The SWOT satellite includes two kind of altimeters: a dual-frequency (C and Ku-band) conventional altimeter which is only available for the nadir point over a ground footprint of 5-10 km. This is the thin line displayed in the middle of each ground track of the animation.
The second altimeter is the core instrument: a Ka-band radar Interferometer (KaRin). KaRin contains two Ka-band SAR antennae at opposite ends of a 10-meter boom (A1 and A2 on the figure) which forms the the interferometric baseline (B on the figure). The interferometric is a dual-swath system, alternatively illuminating the left and right swaths on each side of the nadir track. These two swaths measure 50 km wide in a 1°-4° plan. These are the two large bands displayed on each ground track of the animation.
Sampling simulations (based on a T/P-type orbit) show that the SWOT concept would require a constellation of four conventional nadir-pointing satellites in a repeating orbit. The instantaneous field of view would be wider than with a conventional altimeter, making it possible to cover coastal zones and to improve temporal resolution.
