NASA’s planet-hunting Kepler spacecraft has been saved from disaster after an unknown problem left it floating helplessly in space 120 million kilometers (75 million miles) from Earth.
At the end of last week, NASA announced that Kepler had gone into a fail-safe Emergency Mode (EM) due to an unknown problem with the space telescope, leaving engineers rushing to find the source of the problem over the weekend.
"During a scheduled contact on Thursday, April 7, mission operations engineers discovered that the Kepler spacecraft was in Emergency Mode (EM)," NASA said in a statement. "EM is the lowest operational mode and is fuel intensive. Recovering from EM is the team's priority at this time."
But now the agency has announced that Kepler has recovered. Unfortunately, the cause of the problem is still not clear, so Kepler is not completely out of the woods yet. The spacecraft reached a stable state on Sunday morning and has since switched into a low fuel-burn mode. Scientists will investigate the spacecraft this week to try and work out what the problem was.
"The anomalous EM event is the first that the Kepler spacecraft has encountered during its seven years in space," NASA said in its latest statement, adding that mission operations "remain vigilant".
NASA first detected the problem towards the middle of last week, when scientists had been trying to point the spacecraft towards the middle of the Milky Way for a new round of observations. Owing to the serious nature of the issue, NASA allocated the Kepler team priority access to the Deep Space Network, the Earth-based communications network used to talk to spacecraft around the Solar System. Even using this, though, back-and-forth communication with the spacecraft took 13 minutes, owing to its distance from Earth.
Kepler 452b is the most Earth-like planet found by Kepler to date. NASA/JPL-Caltech/T. Pyle
Kepler was initially launched in 2009 to find planets beyond the Solar System using the transit method – observing the dip in distant stars as planets passed in front. Via this method, the spacecraft has found thousands of potential exoplanets, far more than every other planet-hunting telescope combined. Understandably, then, NASA is pretty keen to keep the successful mission going, at least until its successor – the Transiting Exoplanet Survey Satellite (TESS) – launches in 2017.
This is not the first time Kepler has encountered a bit of a setback, though. In July 2012, one of the four gyroscopic reaction wheels used to orientate the spacecraft failed, meaning scientists had to devise an ingenious solution to use pressure from solar wind to act as a makeshift fourth wheel.
Thanks to these efforts, the spacecraft was able to resume operations as part of the K2 mission in 2014, continuing to find planets beyond the Solar System. Earlier this year, 100 new planets were reported as part of this secondary mission.
And now, Kepler's groundbreaking mission can hopefully continue.