Story 2015-05-30

Software glitch disables LightSail spacecraft

in space on (#A388)
story imageAfter two days sending data back to Earth, a suspected software glitch in the LightSail spacecraft's Linux-based flight software has silenced the craft. Every 15 seconds, LightSail transmits a telemetry beacon packet. The software writes corresponding information to a file called beacon.csv. When it reaches 32 megabytes it can crash the flight system. The manufacturer corrected this glitch in later software revisions, but LightSail's software version doesn't include the update. A fix was scheduled to be uploaded, but before that happened, LightSail fell silent.

A reboot should clear the contents of the problematic beacon.csv file, giving the team a couple days to implement a fix. But the outcome of the freeze is "non-deterministic." Sometimes the processor will still accept a reboot command; other times, it won't. Multiple reboot commands were sent to the spacecraft. Nothing has happened yet. Therefore, we have to assume that LightSail is only going to respond to someone pushing the power button. Spacecraft, however, are susceptible to charged particles zipping through deep space. If one of these particles strikes an electronics component in just the right way, it can cause a reboot. This is not an uncommon occurrence. Cal Poly's experience with CubeSats suggest most experience a reboot in the first three weeks. LightSail is capable of remaining in orbit about six months.