The up-close comet mission is currently out of control.
|Update: NASA announced September 20th the end of operations for the Deep Impact spacecraft. You can read more about the spacecraft's legacy in the University of Maryland press release|
The Jet Propulsion Laboratory announced yesterday that the problem appears to be a software glitch that reset Deep Impact’s computers into a constant reboot mode. Without computers to control its thrusters, the craft can’t hold still, and the team doesn’t know its current orientation. That makes reestablishing communication hard: it’s tricky broadcasting to antennas when you don’t know which ones are pointing at you, and especially when you only have one chance every few days to try.
There’s also the problem of power. Deep Impact’s solar cells aim in one direction, and if they’re not facing the Sun, the craft won’t be able to recharge its batteries. A dead craft can’t be communicated with, regardless of orientation.
Deep Impact is a long-lived interplanetary mission. It jettisoned a projectile that Comet 9P/Tempel 1 “ran over” on Independence Day in 2005, excavating material and allowing scientists to study the comet’s composition. The spacecraft was subsequently recommissioned to a dual mission called EPOXI (short for EPOCH and DIXI, both of which are also acronyms) to investigate comets and exoplanets. In 2010 the craft swept past Comet 103P/Hartley 2, taking fantastic images of the individual jets of gas and dust on the comet’s surface.
Right now the spacecraft was supposed to be observing Comet ISON, which has been the recipient (or victim?) of much fanfare this year. Deep Impact’s pre-perihelion observing window extended from early July to early September. For reasons unrelated to the glitch, observing hadn't begun before the last communication on August 8th. The observing sequence would have started August 14th if they hadn't lost communication, A'Hearn says.
Still, considering that the spacecraft's original mission was slated to end in August 2005, making it another eight years is pretty darn good.