Summary
ESA says Sentinel-3C has returned its first colour images and radar-altimeter measurements, including data on sea-surface height and Greenland’s ice sheet. The satellite remains in commissioning, which is expected to take another five months.
The European Space Agency (ESA) says its Sentinel-3C satellite has returned its first observations from two instruments: colour images of parts of Italy, the Canadian Arctic and the Caribbean, and radar-altimeter measurements of sea-surface height and Greenland’s ice sheet. The acquisitions came about two weeks after launch and provide an early check of the satellite’s performance. Sentinel-3C is still being commissioned, a process ESA expects to take another five months.
First views of land and sea
The satellite’s ocean and land colour instrument captured the Italy image on 30 September. It shows the Po Valley, the Alps, Sicily and surrounding seas. ESA describes differences in the land’s brown and green tones as reflecting vegetation, agriculture and other land cover. Lighter blue water along parts of Italy’s eastern coast may be associated with sediment carried by rivers and moved along the coast.
A second image, also captured on 30 September, covers part of the Canadian Arctic Archipelago west of Greenland. Snow- and ice-covered islands, fjords and exposed rock are visible, along with fractured sea-ice floes on open water. The Caribbean image, captured on 29 September, shows Cuba and the Bahamas; shallow water around the islands appears turquoise against the darker open sea.
These are observations from an instrument designed to measure the colour of both ocean and land. Across the Sentinel-3 mission, such measurements contribute to monitoring marine conditions and land changes, including vegetation health, drought and wildfires.
Altimeter measurements provide an early performance check
Sentinel-3C’s synthetic aperture radar altimeter measures surface height. Satellite altimeters use radar returns to estimate the distance between the spacecraft and the surface below; combined with the satellite’s position, those measurements provide surface-elevation data.
ESA’s first sea-surface-height map covers parts of the Atlantic Ocean and Mediterranean Sea. The agency compared the new measurements with the Copernicus Marine Service’s multi-mission sea-level anomaly data and says they are comparable to current measurements. A separate set of measurements taken between 30 September and 4 October traces the elevation of Greenland’s ice sheet; ESA says the tracks closely match a reference digital elevation model.
The instrument is intended to measure changes in sea-surface height as well as the height of lakes, rivers, sea ice and land ice. Long-term satellite altimetry records are used to track sea-level change: ESA cites a global average rise of 3.64 mm per year since 1999, with the rate accelerating. Sentinel-3C will add observations to records that include missions such as Copernicus Sentinel-6 and Jason.
Sentinel-3 satellites also measure ocean temperature and sea-ice thickness, and support observation of land, inland water and the atmosphere. The first Sentinel-3C acquisitions are an initial step toward that wider monitoring role. Routine service will follow completion of commissioning, which ESA says is expected to take another five months.