In a press conference on Wednesday, NASA warned that its Kepler orbital telescope, which has had much success in spotting Earth-sized planets, may be on its last legs after a serious equipment failure.
The telescope relies on four spinning reaction wheels to keep it aligned on target, and one failed last year. Now another has gone on the blink, leaving the craft spinning in space. The telescope is now in "safe mode," pointed at the sun to power its solar panels but rotating, meaning that it occasionally loses contact with mission control.
"We attempted to return to reaction wheel control as the spacecraft rotated into communication, and commanded a stop rotation," said the Kepler team in a statement.
"Initially, it appeared that all three wheels responded and that rotation had been successfully stopped, but reaction wheel 4 remained at full torque while the spin rate dropped to zero. This is a clear indication that there has been an internal failure within the reaction wheel, likely a structural failure of the wheel bearing."
The telescope can still be controlled using thrusters, but that chews fuel and there's only enough left on board for a few months of orientation. In the meantime, the thrusters can be used to ensure continuous communication with Earth while scientists try to fix the problem.
The Kepler team has been granted extra time on NASA's Deep Space Network to communicate with the telescope, and over the next few weeks will try to jury-rig a system that uses the remaining reaction wheels and the thrusters to regain control. If that isn’t possible, the telescope will be shut down.
"With the failure of a second reaction wheel, it's unlikely that the spacecraft will be able to return to the high pointing accuracy that enables its high-precision photometry. However, no decision has been made to end data collection," the team said.
Kepler was launched in 2009 and completed its primary mission last year. However, such was its success in spotting exoplanets that NASA received extra funding to keep the mission going.
To date it has discovered over 100 Earth-sized planets and thousands of unconfirmed possible candidates, some of which could be capable of supporting life as we know it. More could yet be found as scientists pick through the data the craft has sent back. ®