As NASA continues to diagnose a computer glitch on the Hubble Space Telescope, engineers are preparing to turn on some of the observatory's backup hardware.
The main computer on the venerable telescope shut down unexpectedly on June 13; since then, the operations team has been working to identify and troubleshoot the problem, which is turning out to be rather elusive. More than two weeks into the process and while continuing to work to pinpoint the root cause of the issue, NASA is now preparing to potentially move the telescope to backup hardware, according to a statement released on Wednesday (June 30).
"In parallel with the investigation, NASA is preparing and testing procedures to turn on backup hardware onboard the spacecraft," agency officials wrote in the statement. "The telescope itself and science instruments remain healthy and in a safe configuration."
NASA personnel are continuing to approach the situation cautiously, and the agency estimates they will spend about a week reviewing and updating the procedures necessary to switch Hubble to its backup hardware. The team will also test its plan on a high-fidelity simulator, according to the statement.
When the telescope first went offline, mission personnel suspected a degrading memory module in the aging payload computer was to blame. But as NASA has continued to investigate the glitch, the fault has been elusive.
Technicians are still considering that the problem might lie with a couple of units on the telescope's Science Instrument Command and Data Handling (SI C&DH) unit, which includes the payload computer. In particular, NASA is examining the Command Unit/Science Data Formatter (CU/SDF), which handles data, and the Power Control Unit's power regulator that manages how much voltage reaches the payload computer.
Implementing a workaround for either or both of these pieces of the system would be more complicated than measures NASA has evaluated in the past weeks, according to the agency.
"If one of these systems is determined to be the likely cause, the team must complete a more complicated operations procedure to switch to the backup units," NASA personnel wrote in the statement. "This procedure would be more complex and riskier than those the team executed last week, which involved switching to the backup payload computer hardware and memory modules. To switch to the backup CU/SDF or power regulator, several other hardware boxes on the spacecraft must also be switched due to the way they are connected to the SI C&DH unit."
The computer systems on Hubble date to the 1980s and were installed in 2009 during the final servicing mission by astronauts to repair the orbiting telescope. The backup computer hadn't been used since it left Earth until engineers turned it on during tests about a week ago, only to encounter the same glitches that were troubling the primary computer.
Astronauts deployed the Hubble Space Telescope from the space shuttle Discovery in 1990; the telescope has taken more than 1.5 million observations in the intervening 31 years.
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