The Tropical Rainfall Measuring Mission has been tracking hurricanes and other tropical rain events for seventeen years, ever since its launch from Tanegashima aboard an H-2 rocket in 1997. The spacecraft is a joint effort between NASA and JAXA, the Japanese space agency — JAXA supplied the radar instrument and the launch vehicle, while NASA supplied the rest of the spacecraft and takes care of spacecraft operations. But those operations have at last come to their end; TRMM ran out of propellant last year. It can no longer maintain its orbit and is gradually succumbing to drag. Now, the last instrument has been switched off, as it has sunk too low for it to be useful. The spacecraft is expected to reenter uncontrolled later this year, possibly as soon as June; it cannot control its descent. It was originally intended to dispose of itself at the end of its mission, but the value of its cyclone-tracking capabilities drove NASA to extend its mission to the point of propellant depletion instead.
The mission is a vital one, but it will not die with TRMM; NASA and JAXA collaborated to launch its replacement, the much more capable Global Precipitation Mission, last year. GPM has a higher inclination orbit and a wider swath, allowing it to cover a much larger area than TRMM could. But it’s still sad to see it go. Hopefully someone, such as the ISS crew, will be able to get a shot of its reentry. 😉