NASA is continuing work to resolve an issue that has suspended science operations on the Hubble Space Telescope. The science instruments entered a safe mode configuration on Oct. 25 after detecting a loss of specific data synchronisation messages.
The Hubble team is focusing its efforts to isolate the problem on hardware that commands the instruments and is part of the Science Instrument Command and Data Handling Unit. Specifically, the team is analysing the circuitry of the Control Unit, which generates synchronisation messages and passes them onto the instruments.
While analysing the Control Unit, the team is working to identify potential workarounds for the issue. These include possible changes to instrument flight software that could check for these lost messages and compensate for them without putting the instruments into safe mode. These workarounds would first be verified using ground simulators to ensure they work as planned.
Over the weekend of Oct. 30, the team prepared to turn on parts of the Near Infrared Camera and Multi Object Spectrometer (NICMOS) instrument to collect data on this issue, allowing the team to determine how frequently this problem occurs. Installed in 1997, NICMOS has been inactive since 2010, when the Wide Field Camera 3 became operational. NICMOS allowed the team to use an instrument to collect information on these lost messages while keeping the active instruments off as a safety precaution. Since NICMOS was recovered on Nov. 1, no additional synchronisation messages have been lost.
The team is now taking steps to recover Hubble’s Advanced Camera for Surveys (ACS) instrument from safe mode and start collecting science with that instrument at the beginning of next week. The team will make the decision on Sunday after analysing the latest data. If a lost message is seen before then, the decision to activate ACS will also be revisited. The team is proceeding cautiously to ensure the safety of the instruments and avoid additional stresses on the hardware. Therefore, only ACS will be used in this capacity next week. ACS was selected as the first instrument to recover as it faces the fewest complications should a lost message occur.
Over the next week, the team will continue analysing the Control Unit design diagrams and data associated with the lost messages to determine what may have caused this problem. They will also be looking into potential instrument software changes that could help address it. Once the team better understands the frequency of the problem and has determined the time needed to implement possible software changes, they will discuss a plan for returning the other instruments to science operations.