OverviewNASA and Centre National D'Études Spatiales (CNES) have jointly established and will operate SWOT's Ground Systems, including all facilities required to operate the satellite; acquire its telemetry; and process, distribute and archive data products. The description below covers Satellite Operations and Science Data Processing during the Science Data Collection phase of the mission, approximately six months after launch.
Satellite OperationsThrough S-band command and telemetry links with the SWOT Spacecraft Bus, CNES's Satellite Control Center in Toulouse (France) will oversee satellite control and operations. Twice per day, data will be linked through the CNES S-band network, including ground stations in Inuvik (Canada), Kiruna (Sweden), Hartebeesthoek (South Africa), Kourou (French Guyana), and Kerguelen Island (Indian Ocean). CNES will monitor its instruments from France. NASA instruments will be monitored from the instrument control center at the NASA Jet Propulsion Laboratory (JPL) in Pasadena, California (US).
Science Data ProcessingAbout 21 times per day, ground stations will receive X-band downlink from SWOT's Payload Module. These science data files will be distributed by CNES to JPL's Payload Operations Center. The bulk of the science data will be from the Ka-band Radar Interferometer (KaRIn) instrument.
Over the ocean, KaRIn will process the incoming radar signal from an interferometric channel pair and generate a complex interferogram – as well as amplitude images for each channel – to be downlinked. The onboard processor will also perform multi-look averaging to decrease the data rate over the oceans prior to downlink. Data acquired over land will undergo standard synthetic aperature radar (SAR) compression. These minimally compressed data will be acquired within a land mask covering about 86% of continental surfaces between 78° N and 78° S latitude (excluding Antarctica).
Nominal science and research products, which will be released within 60 days of data acquisition, will be processed by both NASA and CNES and then distributed to operational users.
|SWOT Data Products for Public Distribution
(from KaRIn unless otherwise noted*)
|Earth-located ocean interferograms||*Radiometer brightness temperatures and wet tropospheric delay|
|Beam-averaged Sea Surface Height (Swath & Earth fixed)||Floodplain Digital Elevation Models|
|Water mask pixel cloud||Water mask raster image|
|River single-pass vector product||River averaged vector product|
|Lake single-pass vector product||Lake averaged vector product|
|Single-look complex data in radar coordinates||*Nadir Altimeter Geophysical Data record with waveforms (including interim)|
Mission System Architecture
Pixel Cloud Data Product Status Williams, B. and Fjørtoft, R.
Lake Data Products Status Pottier, C.