Voyager 2 Update from Dr. Ed Stone

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In early May 2010, the 33-year-old Voyager 2 spacecraft experienced an anomaly where the data it returned to Earth was unreadable. Engineers diagnosed the problem as a flip of a bit in the memory in the flight data system computer that packages data to transmit back to Earth, and were able to successfully reset the computer. On May 23, Voyager 2 sent back data that was again formatted properly, but the teams wanted to check out all the systems on the spacecraft to make sure everything was working properly. We checked in with Dr. Ed Stone, former director of JPL and the project scientist for the Voyager project since 1972 to get the latest news on how Voyager 2’s checkout is progressing.

“The science teams have confirmed that Voyager 2 is again transmitting science data in the expected format and the instruments are fully functional,” Stone said via email. “The only remaining action is to reset the clock in the spacecraft’s data system that lost time while the memory bit was in the wrong state. The reset commands will be sent to the Voyager 2 in the next two weeks.”

The flipped or bad bit in the flight data system was likely caused by a cosmic ray that slipped by the radiation protection on the spacecraft. Since the computer stores information in ones and zeroes, a cosmic ray hit can change the value of a memory bit. The concern was that the flipped bit took place in an important location that could have a serious effect on the spacecraft, but fortunately, the problem was solved “easily.”

I say easily in quotes because of the complexities of diagnosing and fixing a spacecraft at such great distances. Since Voyager 2 is about 13.8 billion kilometers, or 8.6 billion miles, from Earth, it takes nearly 13 hours for signals to reach the spacecraft and nearly 13 hours for signals to come down to NASA’s Deep Space Network on Earth.

Hats off to the scientists and engineers at JPL for their efforts and dedication so we all can continue to follow Voyager’s continuing journey to interstellar space.

Sources: JPL, email exchange with Dr. Ed Stone, Planetary Blog.