Last week, the MRO spacecraft unexpectedly “safed.” This is when it reboots and puts itself into a precautionary mode; in this case it was in response to an unexpected voltage reading (more information in this press release about the safing). The engineers at JPL and Lockheed Martin spent long hours investigating the cause, making sure the spacecraft is healthy and unharmed (which it does appear to be), and cautiously getting things back to normal. I’ll jump right to the happy ending of the story, which is that we are now back to normal, imaging Mars as usual (here’s the press release about resuming routine operations).
What do the people at the HiRISE Operations Center (HiROC) do when the MRO spacecraft safes?
When the spacecraft safes, the automatic reset sequence also turns off all the scientific instruments on board. So we were shut down early last week. We knew from preliminary investigations that HiRISE wasn’t involved with the cause of the event (whew!), so we couldn’t really help analyze the cause. This was different from some situations in the past where HiRISE caused itself to safe; in those cases, we were responsible for figuring out why. This time we just had to wait while the spacecraft engineers figured out the problem.
Once the engineers determined we could go back to normal operations, we worked with them on our instrument safe mode recovery. This involves radiating a set of pre-written commands and files to the spacecraft, verifying that the setup commands executed correctly on the instrument, and watching the instrument telemetry to make sure we power up correctly. We have a series of checks built in to this sequence. They work like a checksum, and send that information back down to Earth in the telemetry. We check those values against what we expect them to be, and that’s how we know the correct values were written to memory. Without this confirmation, we couldn’t be sure that HiRISE’s memory was uncorrupted.
Every step in the lengthy procedure executed successfully, and all of the checks matched what we expected, so we were able to confirm that HiRISE was ready to return to normal imaging. The next day, they restarted the sequence on board that calls our imaging commands, and we were back in business!
- Related HiBlog post: On the Safe Side