The Tropical Rainfall Measuring Mission (TRMM), one of the spacecraft in the NASA Earth Probe series of research satellites, is a highly-focused, limited-objective program aimed at measuring monthly and seasonal rainfall over the global tropics and subtropics. TRMM is a joint project between the USA and Japan to measure rainfall between 35 degrees N and 35 degrees S at 350 km altitude.
The TRMM Precipitaing Radar data will provide the first opportunity to estimate the vertical profile of latent heat release. Instruments on-board the satellite are: (1) a single frequency (13.8 GHz) Precipitation Radar (PR) provided by Japan; (2) a visible-infrared scanning radiometer (VIRS) similar to AVHRR; (3) a passive microwave radiometer called the TRMM Microwave Imager (TMI), similar to the SSM/I microwave radiometer on the DMSP-series; (4) a Lightning Imaging Sensor (LIS) for the detection and distribution of global lightning; and (5) the Clouds and Earth's Radiant Energy System (CERES) instrument for the measurement of the Earth's radiation budget. With the exception of the PR, all of the instruments are provided by NASA.
The launch vehicle was provided by Japan and the satellite by NASA. The TRMM spacecraft is planned to be a free-flyer launched on an expendable Japanese HII rocket with a low-altitude, non-sun-synchronous orbit. The primary C&DH link for the TRMM payload is the S-band Single Access (SSA) channel through the Tracking and Data Relay Satellite System (TDRSS). Spacecraft housekeeping command and telemetry and back-up for the science data are via the TDRSS S-band Multiple Access (SMA) channel. The orbital position of the spacecraft is determined by the TDRSS ranging system. The minimum mission life for TRMM was to be three years.
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