=> Update : ESA is progressing fast. All lands overflown by Sentinel-2B were available in PEPS on November 12th, thanks to EDRS relay satellites.The Sentinel-2 mission, made of two twin satellites S2A and S2B, has been stated « operational » since beginning of October, even if each satellite was only observing on one orbit out of two everywhere except in Europe and Africa. As a result, the 5 days revisit was only available in these two continents. But in the new Sentinel-2 mission status report, ESA announced this very good piece of news :
Sentinel-2A and -2B are together acquiring Europe, Africa and Greenland with 5 days revisit. The rest of the World is revisited every 10 days jointly by the two satellites. Full systematic 5-day revisit everywhere will be reached once EDRS downlink becomes available operationally, assumed during December 2017 for both S2A and S2B.
The « EDRS downlink » uses a laser terminal on board S2A and S2B, that sends data to ageostationary satellite of the European Data Relay Satellites constellations (EDRS), which is then retransmitted to a ground station. I let you imagine the pointing accuracy necessary to point a laser to a satellite at 36000 km distance. This is achieved thanks to a system provided by the German aerospace agency DLR. (For memory, such a transmission was done at CNES for the first time on SPOT4 using the PASTEL-SILEX communication system, but it was only for a successful demonstration and was not used operationally). S2B should start first, and the ramp up phase has started ! S2A communication system had an anomaly (not detailed by ESA), which seems to have been overcome lately. A great thanks to ESA and DLR for allowing us to get these long awaited data. It will be a very nice Christmas present for all users outside Africa and Europe, who will benefit from a doubled likelihood to get cloud free observations. Our MAJA L2A processor for cloud detection and atmospheric correction, which uses multi-temporal information will also benefit from this increased repetitivity. MAJA L2A products are available from Theia land data center.