WASHINGTON — With its fuel supply depleted past the point where orbit-boosting maneuvers are practical, NASA has decided to shut down the 17-year-old precipitation-monitoring Tropical Rainfall Measuring Mission satellite in 2016, according to a note posted to the agency’s website Aug. 25.
“Pressure readings from the Tropical Rainfall Measuring Mission’s (TRMM) fuel tank on July 8 indicated that the satellite was nearly at the end of its fuel supply,” NASA wrote in the Aug. 25 note. “As a result, NASA has ceased maneuvers to keep the satellite at its operating altitude of 402 kilometers.”
Shutdown is slated for February 2016, and re-entry projected for November of that year, NASA said. TRMM will continue observations until shutdown. However, the satellite’s main job of measuring planet-wide rainfall has already been taken over by the Global Precipitation Measurement (GPM) core observatory, which launched in February. TRMM and GPM are collaborations of NASA and the Japan Aerospace Exploration Agency. Japan launched both spacecraft.
TRMM was launched in 1997 on what was supposed to be a three-year mission. But the spacecraft’s observations proved popular with weather forecasters, who nearly a decade ago helped turn back a NASA decision to end the mission while the roughly 3,500-kilogram spacecraft still had enough propellant left to steer itself into an uninhabited stretch of the Pacific Ocean — a NASA requirement for all satellites deemed to pose a greater than 1-in-10,000 chance of harming people or damaging property on the ground should they be left to re-enter on their own.
NASA approved a few short-term extensions before waiving the safety guidelines in 2005. NASA said at the time that not requiring TRMM to hold fuel in reserve for a controlled deorbit would allow the satellite to remain in service through at least 2010 — the year it had expected GPM to enter service.