Emily LakdawallaMay 06, 2010

Some trouble on Voyager 2

The following was posted on JPL's website late this afternoon:

Engineers have shifted NASA's Voyager 2 spacecraft into a mode that transmits only spacecraft health and status data while they diagnose an unexpected change in the pattern of returning data. Preliminary engineering data received on May 1 show the spacecraft is basically healthy, and that the source of the issue is the flight data system, which is responsible for formatting the data to send back to Earth. The change in the data return pattern has prevented mission managers from decoding science data.

The first changes in the return of data packets from Voyager 2, which is near the edge of our solar system, appeared on April 22. Mission team members have been working to troubleshoot and resume the regular flow of science data. Because of a planned roll maneuver and moratorium on sending commands, engineers got their first chance to send commands to the spacecraft on April 30. 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.I'll post any further news as I receive it. I see good news and bad news in the information they released today. The bad news: they are still trying to "diagnose" the problem -- I am sure that if they knew exactly what the problem was, and how to fix it, they would have said so (or done so before they even talked about it).

Voyager 2 in the solar wind
Voyager 2 in the solar wind This artist's concept shows the venerable Voyager 2 spacecraft journeying out of the solar system at 15 kilometers per second (34,000 miles per hour) with the solar wind streaming past it four times faster.Image: NASA / GSFC Conceptual Image Lab

The good news: Voyager 2 is hearing and responding to commands. I don't know for sure but I would guess that for a large number of the possible things that could go wrong with Voyager 2 (or any other spacecraft, for that matter), the first symptom of the problem would simply be that the spacecraft didn't show up for a planned communication session. It's really hard to troubleshoot a problem if you have no information on what the problem is, other than the spacecraft isn't talking to you. But Voyager 2 is clearly talking to mission control, and not only is it talking, but it's responding to radioed commands, because "engineers have shifted" it into a different mode. That's very good.

But it must be hard to troubleshoot a spacecraft that is 33 years old and 13 light-hours away. Think about that: if you want to talk with Voyager 2, you set up your commands, blast them out from your biggest space antenna -- let's say, for argument's sake, it's the big dish at Canberra (it ain't Goldstone, because that one's down for repair). By the time the signal has reached Voyager 2, been responded to, and a reply signal has time to propagate across space and return to Earth, Earth has gone through one complete rotation, so it'd be Canberra again that would receive the reply. Crazy.

I hope they get the old girl back into normal operation. I know she has to go someday, but I'll hate to see that day!

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