Rani Gran, NASA’s Goddard Space Flight Center
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. As a result, NASA has ceased maneuvers to keep the satellite at its operating altitude of 402 kilometers (~250 miles). With its speed decreasing, TRMM has begun to drift downward. A small amount of fuel remains to conduct debris avoidance maneuvers to ensure the satellite remains safe.
TRMM’s slow descent will continue over the next 2 to 3 years. It will continue to collect useful data as its orbit descends to about 350 (217.5 miles) over the next 18 months. Once TRMM reaches an altitude of 150 to 120 kilometers (93 to 75 miles), it will re-enter the atmosphere.
The TRMM satellite, a joint mission between NASA and the Japan Aerospace Exploration Agency (JAXA), was launched in 1997 to measure precipitation over the tropics, carrying the first precipitation radar into space.
“TRMM has met and exceeded its original goal of advancing our understanding of the distribution of tropical rainfall and its relation to the global water and energy cycles,” said Scott Braun, the mission’s project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
Its planned three-year mission has already lasted 17 years and provided researchers with an unprecedented data set that combined more traditional radiometer measurements with 3-dimensional radar scans across the tropical ocean and into the lower mid-latitudes from 35N to 35S latitude. Also unique to TRMM is its inclined orbit that allows it to cut across the paths of polar orbiting satellites and revisit locations at different times of day, which is important for understanding how rainfall evolves with the day/night cycle. TRMM provided the first measurements of this type over the tropical ocean.