Japan Aerospace Exploration Agency (JAXA) completed normal mission operation of the Precipitation Radar (PR) on board the Tropical Rainfall Measuring Mission (TRMM) satellite on 7 October 2014 (UTC). Rainfall observation by PR will be succeeded by the Dual-frequency Precipitation Radar (DPR) on board the Global Precipitation Measurement (GPM) Core Observatory, which was launched on 28 February 2014 (JST).
The TRMM satellite was launched by H-II launch vehicle No.6 from the Tanegashima Space Center on 28 November 1997 (JST). After completion of its nominal mission on 31 January 2001, JAXA and U.S. National Aeronautics and Space Administration (NASA) extended mission operation of the TRMM satellite. The TRMM satellite was raised its altitude from 350 km to 402.5 km in order to extend its lifetime in August 2001. Ever since then, it continues observations on the orbit more than 17 years, which is far beyond its design life of 3-year and 2-month.
On July 8 2014, rapid pressure decreases was read from the fuel tank during the station keeping maneuver, and NASA indicated that TRMM is at the end of its fuel. As a result, NASA and JAXA have decided to cease station keeping maneuvers, and the TRMM satellite has begun its drift downward from its operating altitude of 402.5 km. On 5 October 2014, satellite altitude has reached to 392.5 km, which is lower limits of PR’s observable altitude, and JAXA completed PR’s extended operation on 7 October.
Since the PR hardware is still in healthy condition, JAXA plans to conduct extra experimental operations of the PR during about 6 months while the spacecraft descending. The PR observation data around 350 km, which is original nominal altitude, will be distributed to public after verification. Also, NASA continues operations of the TRMM Microwave Imager (TMI) while the spacecraft descending, since its operations do not depend on altitude.
We greatly appreciate relevant agencies and people for their cooperation to the TRMM/PR mission, and would ask further supports to the GPM/DPR mission.