Mission to monitor our rising oceans

Two Sentinel-6 spacecraft will provide centimetre-scale measurements of global sea-level rise. The twin craft – Sentinel-6A and Sentinel-6B – will each carry powerful new Poseidon-4 radar altimeters


Global sea level variation (mm)

Jan 1995: 13.0
Mar 2011: 47.9
Jan 2013: 67.2
Jul 2020: 94.7 

30% of sea level rise attributed to ocean thermal expansion, 70% to ice melt

100
80
60
40
20
0
1993 95 00 05 10 15 20


Nov 10, 2020: Launch of Sentinel-6A Michael Freilich atop SpaceX Falcon-9


Solar array


1. Poseidon-4 radar altimeter: Bounces pulses off ocean surface and measures time taken to return to low earth orbit, ≈1,330km

Data determines change in height of sea surface

2. Microwave radiometer: Corrects any delay caused by water vapour in atmosphere

Precise Orbit Determination (POD)

3. DORIS: Doppler Orbit Radio positioning system

4. GNS: Global navigation system receiver

5. Star trackers: Compare craft’s absolute position to stars

1 2 3 4 5 5 


3.3mm per year
Rate of sea level rise, 1995-2020


Sources: European Space Agency, NASA Goddard Space Flight Center 
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