June 21, 2023

Ground segment

The mission ground segment comprises: 

  • A control centre in Toulouse handling satellite command-control and operations.
  • Two mission centres (at JPL and CNES)
  • A network of S-band and X-band stations provided by CNES's multi-mission ground segment (ground stations in Inuvik and Kiruna, with additional passes over Aussaguel, Hartebeesthoek and Kourou)
  • An orbit computation centre (OCC) provided by CNES

21 passes a day are required to send the 7.9 Tb of data acquired by the satellite. Raw and processed data are transferred daily to JPL via a dedicated server.


SWOT ground segment architecture

CNES is in charge of processing data received from the nadir payload, which it sends to JPL for archiving and distribution by both agencies.

The two agencies provide level 1 and 2 KaRIn data (geolocated water elevation levels with known errors removed), complemented by a river discharge product.

SWOT offers two acquisition modes covering different resolutions and fields of investigation:

  • High-resolution (HR) mode for land surface hydrology, affording very high spatial resolution to precisely identify fine (rivers) and small (lakes) features. This mode is only activated over land surfaces (coast to coast).
  • Low-resolution (LR) mode for oceanography, affording very high elevation accuracy but much lower planimetric resolution than HR mode. Planimetric resolution is still much better than that of today’s nadir altimeters. This mode is constantly active, even over land.

CNES’s and NASA’s contributions to operational processing guarantee performance, availability and distribution of level 2 products:

  • CNES is in charge of processing high-resolution and low-resolution data from all regions of the globe on the fly.
  • NASA/JPL is in charge of reprocessing all raw mission data on a near-yearly basis
  • The two mission centres exchange raw, calibration and housekeeping data
  • Data are archived and distributed by both agencies via PODAAC for JPL and thematic data hubs in France
  • CNES processes data from the Nadir payload in the same way as for conventional altimetry missions
  • CNES is in charge of precise orbit determination

A French-U.S. Algorithm Development Team (ADT) has been set up to supply operational algorithms and test cases that are shared between CNES and NASA. The ADT is in charge of delivering operational algorithms for integration in processing chains.

Ground segment by the numbers
Telemetry1 Tb/day
Data generated20 Tb/day
Products generated33,500/day
Data transferred to JPL15 Tb/day
Processors required+ 3,000