WASHINGTON — Two weeks after going into an emergency mode that jeopardized the mission, NASA’s Kepler spacecraft has recovered and resumed normal science operations, the agency announced April 22.
In a statement, Charlie Sobeck, the Kepler mission manager, said that the spacecraft had resumed science operations as of 11:30 a.m. Eastern April 22. The spacecraft is now beginning the latest observing campaign for its extended mission, known as K2.
Kepler was scheduled to begin those observations earlier in the month, but when spacecraft controllers made contact with the spacecraft April 7 they found the spacecraft was an emergency mode, which NASA describes as the lowest operational mode of the spacecraft. The mission declared a spacecraft emergency to gain priority access to the Deep Space Network to recover the spacecraft.
Controllers were able to restore control of Kepler by April 10 and exit emergency mode, gradually bringing back up the spacecraft’s various system. That process found no evidence of damage to the spacecraft, allowing science observations to resume.
The cause of the problem that triggered the emergency is still under investigation, but Sobeck said that some kind of “transient event” may have triggered a series of false alarms that overwhelmed the spacecraft’s computers. “Power-cycling the onboard computers and subsystems appears to have cleared the problem,” he said. “We’ve returned to science data collection while the investigation proceeds.”
The problem was the most serious issue for Kepler since 2013, when the failure of the second of four reaction wheels on the spacecraft forced it to end its primary mission of observing the same region of the sky four years after its launch. Kepler monitored that region to look for minute variations in the brightness of stars there caused by planets crossing them, allowing astronomers to discover thousands of extrasolar planets.
With only two reaction wheels working, Kepler could not point stably enough to continue its primary mission. Engineers, though, developed an alternative pointing approach that allows the spacecraft to point at the same region of the sky for about three months at a time. Kepler started the series of observing campaigns for what is now called the K2 mission in 2014.
Prior to the recent problem, project officials said the spacecraft had could operate until 2018. Sobeck didn’t indicate if the anomaly affected the spacecraft’s lifetime.