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NASA saves Kepler space 'scope by turning it off and on again

Exoplanet mission back on after forcing an unexpected reboot

By Iain Thomson, 22 Apr 2016

The Kepler space telescope is back in action after a tense couple of weeks for NASA engineers.

On April 8 the space agency reported that Kepler was stuck in emergency mode, which not only made stellar observations impossible but also burns through the telescope's limited fuel reserves at a prodigious rate.

In a couple of days, NASA had a grip on the problem, managing to get the telescope firmly aligned for Earth-bound communications links. The instrument, currently orbiting the Sun around 75 million miles from Earth, was at last responding to commands.

Now it's back in action, NASA reports, after engineers tried one of the oldest tricks in the computer repair playbook.

"Power-cycling the onboard computers and subsystems appears to have cleared the problem," the agency said – meaning they turned it off and on again, although it's slightly more complex than that.

"The pointing tables and science targets – instructions that tell the spacecraft where to look and at what – were reloaded and confirmed, onboard logs and counters were reset, and a new command sequence was created, tested and uploaded to account for the late start of the campaign."

The cause of the breakdown is still under investigation, but NASA said it was most likely a "transient event," which triggered a cascade of false alarms that kicked the telescope's subsystems into emergency mode. The agency will try and replicate the problem using ground-based systems to find out more.

In the meantime, Kepler is back on track and surveying the center of our Milky Way looking for exoplanets around stars, or just wandering through the celestial depths. It will continue until July 1, when the galactic center moves out of the spacecraft's view, and then new targets will be found.

Kepler's rebirth is yet another example of why NASA has some of the best engineering hackers in the world. In 2013, the telescope was feared lost after two reaction wheels that point the instrument failed, but NASA boffins used the pressure of particle streams from the Sun on its solar panels and the remaining two reaction wheels to steady the 'scope for further use. ®

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