CFOSAT Mission objectives

The China France SATellite (CFOSAT) mission aims to study ocean surface winds and waves starting in 2018. CFOSAT is a pre-operational mission that provides real-time wind and wave observations to meteorological agencies to improve forecasts and sea state models. These measurements also support oceanographic and climate research by improving ocean models and understanding the impact of sea state on surface fluxes. In other words, CFOSAT serves the operational and scientific communities by improving wind and wave forecasts and contributing to a more comprehensive understanding of ocean surface dynamics.

Key objectives

• Modeling and prediction of ocean surface wind and waves
• Understanding the physical processes of wind and waves
• Investigate interactions between surface waves, the atmosphere, and the ocean
• Investigate interactions between electromagnetic signals and the ocean surface
• Study the evolution of waves in coastal regions

Other objectives include estimating radar cross section dependence and deriving properties related to sea surface slope statistics, wind characteristics, and surface features in polar regions and over land.

CFOSAT instruments and scientific requirements

Developed jointly by CNES and the China National Space Administration (CNSA), CFOSAT is equipped with two radar instruments: SWIM (Surface Waves Investigation and Monitoring) and SCAT (Wind SCATterometer), provided by CNES and CNSA respectively. SWIM, with its 6 rotating beams, measures wave properties such as direction and wavelength, while SCAT measures wind intensity and direction. The data are transmitted to French and Chinese receiving stations.
Designed by the LATMOS (Laboratory for Atmosphere, Environment and Space Observations) in Paris and Guyancourt, SWIM was built by Thales Alenia Space under the supervision and funding of CNES.
Other key partners include the French Institute for Research and Exploration of the Sea (IFREMER), the French National Meteorological Service (Meteo-France) and the French Naval Hydrographic and Oceanographic Office (SHOM).

The scientific requirements are:

• Estimate directional spectra of ocean waves along the satellite orbit at scales ranging from 50 x 50 km² to 70 x 70 km²
• Transmit data near-real time within 3 hours of acquisition
• Estimate wind speed and significant wave height from the nadir-looking beam, similar to altimeter missions
• Estimate the wind vector over a swath of approximately 900 km with a nominal resolution of 50 x 50 km² (target 25 x 25 km²)
• Sample spectral wave properties with a global coverage on a time scale of 10 to 15 days
• Obtain wind measurements with a global coverage on a time scale of 1 to 2 days
• Estimate the radar cross section dependence with incidence (from 0 to 10° and from 18 to 50° for SWIM and SCAT, respectively) and azimut to derive from these profiles:
  • Sea surface slope statistics (mean square slope, slope probability density function shape)
  • Estimation of wind direction and speed
  • Contribution of volume scattering to surface scattering and ice surface and snowpack characteristics in the polar ice sheet
  • Bare soil moisture and roughness