BEST: New Satellite Mission Dedicated to Tropical System Energy Budget

The energy budget of the global atmosphere is dominated by tropical energy sources. To accurately estimate the energy balance requires the simultaneous measurement of its various components: sources (radiation budget and surface fluxes), conversions (convection and precipitations), and transports. These terms are related to the primary variables: temperature, pressure, water vapor, and wind, the observation of which is generally poor and irregularly distributed. Assimilation of available data in general circulation models should then present a more coherent space and time description to emerge. BEST (Bilan Energetique du Systeme Tropical—Tropical System Energy Budget) is a satellite project designed to provide the required simultaneous measurement of wind and precipitation fields in the tropical zone. The project‐sponsored satellite would be placed in a 400–600 km altitude 28.5° inclination orbit with a three‐year lifetime. It is scheduled to carry a rain radar, a wind Doppler lidar with four fixed telescopes, and a microwave scanning radiometer. The possible addition of a differential absorption lidar is also considered. The BEST project is currently under phase A study at Centre National d'Etudes Spatiales (CNES) in conjunction with several French scientific laboratories. This project is expected to involve international cooperation in view of a possible launch in 1998–2000 time frame. The BEST mission will contribute to the global energy and water cycle experiment (GEWEX) and global change international programs.