The SWOT satellite observatory is being jointly built by NASA and France's Centre National D'Études Spatiales (CNES). It consists of a Payload Module and Spacecraft Bus whose assembly is being led by the NASA Jet Propulsion Laboratory (JPL) and CNES, respectively.

3D SWOT Spacecraft Model
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The Payload has components contributed by NASA, CNES, and CSA. The primary payload is the Ka-band Radar Interferometer (KaRIn) that is being developed by JPL. The Canadian Space Agency will provide a high-power assembly component for KaRIn. CNES will build the Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) Antenna and Nadir Altimeter. JPL will also provide a Global Positioning System (GPS) science receiver, a Laser Retroreflector and a two-beam Microwave Radiometer.


SWOT's payload is comprised of the following instruments:

  • KaRIn
    • Using JPL-developed instrument technology, radar interferometry, KaRIn will measure ocean and surface water levels over a 120-km (75-mi) wide swath with a ~20 km (~12 mi) gap along nadir. It will operate in two modes:
      • Low-Resolution over the ocean with significant onboard processing to reduce data volume.
      • High-Resolution over broad, primarily continental, regions defined by the SWOT Science Team, focusing on hydrology studies.
  • Jason-class Altimeter will collect data in the gap between the KaRIn swaths. It will send and receive signals that travel straight up and down. Each pulse's round-trip travel time will be used to determine Sea Surface height.
  • DORIS Antenna will pick up signals from 50-60 ground-based radio beacons, equally distributed over Earth to ensure good coverage.
  • Microwave Radiometer will measure the amount of water vapor between SWOT and Earth's surface. More water vapor means slower radar signals.
  • X-band Antenna will be used for high-rate data downlink.
  • Laser Reflector Assembly is an array of mirrors that will provide a target for laser tracking measurements from the ground.
  • Global Positioning System (GPS) Receiver will pick up tracking signals from the constellation of GPS satellites.

Spacecraft Bus

Mounted below the Payload Module, the Spacecraft Bus is a multi-purpose platform housing many of the electronics required for the observatory to function:

  • S-band antenna will be used to communicate with Earth using a radio transmitter and receiver.
  • Command and data handler will manage the observatory's communication links and perform various tasks (e.g., data storage) using a centralized processor.
  • Electrical power subsystem is where all of the spacecraft’s power is generated, stored, and distributed.
  • Thermal control is a subsystem responsible for maintaining the temperatures of each component on the observatory within its allowable limits.
  • Solar arrays will be deployed from opposite sides of the Spacecraft Bus while SWOT is in orbit, using small drive motors to keep them pointed at the Sun.
  • Attitude control system will determine the observatory's orientation using star trackers. The satellite's attitude will be carried out by magnetic torquer bars and reaction wheels.
  • Propulsion will be used to adjust SWOT's orbit by firing a combination of its onboard thrusters. This subsystem also includes a propellant tank.


How SWOT Will Work [e-brochure]
(2017) This e-brochure explains how interferometry - the study of how waves interfere - will be used by SWOT to measure water levels with extraordinary accuracy across the globe.

Solar Panel Deployment [video]
(2016) The deployment of SWOT's solar panels is featured in this animation.

Deployment of Interferometer Antennas [video]
(2016) This animation shows the various stages of boom deployment for the interferometer antennas.

SWOT Data Collection Over Florida [video]
(2016) This animation shows the collection of data over the state of Florida, which is rich with rivers, lakes and wetlands.