Dear NWP centers, The two Sentinel-6 satellites “Michael Freilich” (MF, also known as “A”) and “B” are currently in a tandem orbit separated in time by about 30 seconds. As a result, and to our knowledge, RO NRT BUFR products from both satellites are not assimilated together currently into weather forecasts. The S6-B commissioning phase is coming to an end. The Sentinel-6 Project is planning to start moving the S6-MF satellite no earlier than November 17, 2026 to a new orbit. At the end of this transition, the two satellites will be sufficiently far away that RO NRT BUFR products from both satellites can be assimilated together into weather forecasts. In addition, the GNSS-RO instrument software on S6-MF will be upgraded to match the configuration of the S6-B instrument no earlier than November 2, 2026. Therefore, we recommend users to start assimilating S6-B RO NRT BUFR products on November 2, 2026. Doing so will ensure that operational BUFR products will be available from one satellite (namely, S6-B) during the S6-MF software upgrade and transition to the new orbit. We will follow up with another email when S6-MF BUFR products are available again for you to assimilate, perhaps towards the end of November (TBC). At that point, the two satellites will no longer be in tandem and assimilation of BUFR products from both S6-MF and S6-B can occur. Please let us know if you have any questions. Best, Chad, on behalf of the Sentinel-6 RO team [JPL logo] Chad Galley, PhD Group Supervisor 362F | Space Geodesy & Geodynamics JPL 4800 Oak Grove Drive Pasadena, CA 91109 Mail Stop 238-600 M: 410.491.0024 O: 818.354.1013 F: 818.393.4965 chad.r.galley@jpl.nasa.gov<mailto:chad.r.galley@jpl.nasa.gov>
