Sentinel 6 Michael Freilich satellite. Computer illustration of the ESA's (European Space Agency's) Sentinel 6 Michael Freilich (Sentinel 6A) satellite in orbit over the Earth. The Sentinel 6 program consists of 2 identical satellites that will measure sea surface levels and sea ice thickness. Each satellite carries a radar altimeter to provide high-precision and timely observations of the topography of the global ocean in an effort to better understand and monitor climate change. Sentinel 6A will be launched in late 2020, with the second satellite scheduled for launch in 2026.