On April 11th, 2016 we learned about

NASA spends the weekend saving our link to the Kepler spacecraft

Surprises can be a scary prospect in science. On the one hand, you might be pleasantly surprised by the diversity of planets in the universe, but sometimes the unexpected comes in the more crushing realization that your satellite isn’t working, and you may never get to look for planets with it again. The latter was the unfortunate news that the Kepler spacecraft team had to confront on April 9th. Rather than send new instructions for their K2 mission, the team instead had to work to restore operations to their seven-year-old instrument after discovering that it had gone into Emergency Mode when nobody was looking.

Little recourse for repairs

As you might expect, there aren’t a lot of options for repairing inoperable spacecraft. While astronauts did conduct manual repairs on the Hubble telescope in 1993, that kind of mission was only an option because it could be done in the Earth’s orbit. Kepler, on the other hand, is about 75 million miles away, so nobody will be arriving with spare parts any time soon. On the bright side, finding out that the spacecraft had automatically switched to Emergency Mode was actually a good sign, because it meant that whatever had gone wrong might not require any new hardware. Compared to the apparent destruction of the Hitomi satellite in March, the fact that Kepler could still broadcast a signal was reason for hope.

The hope of recovery didn’t mean that the Kepler team could act casually though. Time was critical since Emergency Mode uses more fuel than normal, and so the longer the team took to normalize Kepler, the shorter it’s operational lifespan would be before it ran out of power.  Kepler’s distance from Earth means that sending and receiving a signal takes at least 13 minutes. To help, the Kepler team was given priority status to NASA’s Deep Space Network, disrupting other missions’ communication schedules for the time being.

Unexplained but undeterred

The good news is that the thorough response to this unexpected dilemma paid off. Kepler is now operating normally, transferring data with its antenna pointed towards Earth. It’s not yet clear what caused the spacecraft to enter Emergency Mode in the first place, but engineers have ruled out that it was any of the new commands for the K2 mission, as logs recovered so far indicate the problem started at least 14 hours before a new maneuver was requested. Since it may take some time to fully understand what went wrong, the spacecraft will resume its search for exoplanets without waiting for a final diagnosis.

Source: Mission Manager Update: Kepler Recovered from Emergency and Stable by Charlie Sobeck​, NASA News

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