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 October 25 after detecting a loss of specific data synchronization 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 analyzing the circuitry of the Control Unit, which generates synchronization messages and passes them onto the instruments.
While analyzing 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 October 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 November 1, no additional synchronization 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 analyzing 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 analyzing 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.
Re: Hubble problems. Fresh out of college, I worked on Surveyor at an aerospace company, and my boss had me review the entire schematic to the landing radar & write a memo about any problems I found. One was using a 1N914 signal diode to charge a big capacitor from a firing SCR. When Surveyor 3 “happily landed 3 times in order to sample the surface” my boss came to me very angry and asked why I missed that diode overstress, because the diode had failed in the latest Thermal Vaccum test. I told him it was in my memo. His face turned white and he walked away without another word. He had not bothered to read my memo. The Surveyor engine had not fired The 13 Foot Mark to shut off the rocket and slowly fall. It simply had run out of fuel and “bounced” twice, making 3 delightful footprints. That was what NASA told the press. “Now we know the surface is like face powder.”