NASA Fixes Iconic Hubble Space Telescope and Brings It Back Online

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It has now been more than a month since the Hubble Space Telescope reverted to safe mode following an apparent memory failure. NASA attempted all the standard fixes such as turning it off and on, but the aging observatory stubbornly refused to come back online. After investigating the issue, NASA traced the failure to a power component on the Science Instrument Command and Data Handling module. The team announced yesterday (July 15) that it was beginning a process to switch to the backup data handling module, which could take several days. However, NASA says Hubble is already up and running today. 

The issues started on July 13th when Hubble’s payload computer stopped working. This is separate from the spacecraft’s main computer, so NASA has not lost communication. However, the payload computer controls and coordinates the science instruments on Hubble. Without it, Hubble has no reason to continue operations. When the payload computer failed, the main computer put Hubble in safe mode, and little changed for the ensuing month. 

Initially, NASA engineers believed the problem was tied to memory modules on the payload computer. The team tried to swap in one of the four spare memory chips, but that didn’t work. Now, NASA says the issue is most likely at a higher level. The payload computer is part of the Science Instrument Command and Data Handling (SI C&DH) unit, which astronauts replaced during Hubble’s final servicing mission in 2009. The information gathered over the last several weeks has convinced NASA that the issue lies with the Power Control Unit (PCU) on the SI C&DH. Unfortunately, NASA was not able to reset the PSU via ground commands. 

A Hubble SI C&DH unit prior to its installation in the telescope.

Like most expensive hardware destined for space, Hubble was designed with numerous redundancies. The SI C&DH is a two-sided computer, so NASA decided to switch to the backup side of the system, which has its own components unconnected to the malfunctioning ones. NASA successfully flipped the switch on the backup system and loaded it with flight software. Several other components were also moved to alternate interfaces that connect with the backup payload computer. So far, all is going well and the team expects it will be able to recover all the instruments from safe mode very soon. Then, the telescope just needs calibration and it can return to science operations. 

NASA has been forced to rely on backup hardware to keep the telescope operational in recent years, but it’s running out of backups. After 30 years, Hubble is nearing the end of its useful life. It’s already lasted much longer than anyone anticipated, and if we’re lucky, it will share the sky with the James Webb Space Telescope. Webb is scheduled to launch by the end of 2021. Unless it gets delayed again, which would not be surprising at this point.

Note: This article has been updated with the latest information from NASA. 

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