On June 13, the Hubble Space Telescope stopped working due to a malfunction in its computer, which runs the telescope’s science instruments. Since then, NASA has been doing the kind of troubleshooting familiar to many of us — with the added stress of the irreplaceable device, in space, and in the same old fashion as the Commodore 64.
So far, consoles have been able to discover many things Not At fault, based on unsuccessful repair attempts. The workers narrowed down the problem, but did not define it precisely. At this point, the next steps will depend on the exact nature of the problem, so getting a diagnosis is the top priority.
If at first you don’t succeed…
The devices in question are part of a payload computer system, which contains a control processor, a communications bus, a memory unit, and a processor that coordinates data and commands so that the controller can “talk” to all of the individual scientific instruments (the system also converts the data produced by the instruments into a standard format for transmission to Earth). There is also a power supply that is supposed to keep everything running at the proper voltage.
Out of caution, the people who designed Hubble provided a spare console and three spare memory modules.
Initial indications showed a possible problem with the memory module, so the first attempt to restore Hubble involved trying to switch to one of the backups. This fix failed, indicating that the individual memory behavior was merely a symptom of problems elsewhere. Switching to the backup console also failed to fix the problem; Regardless of the combination of the controller and memory module used, Hubble could neither read nor write to memory.
Given this information, the observers turned their attention elsewhere. The main candidates now are the power supply, data bus, and data format processor. It is still possible to switch to console and backup memory, but the sequence of action will vary based on the exact error. In a press release, NASA referred to the process as “more complex and more dangerous.”
But we also have reason to be optimistic: the data coordinator failed in 2008, and NASA successfully switched to backups, which worked until a maintenance task replaced the failed devices.
Given that NASA no longer has access to a vehicle designed for these types of service missions, having a functional backup in place will be essential if we are to spend more years at this unique observatory.