After a tense month, the Hubble Space Telescope resumed operations this past weekend.

Peculiar galaxies
These early snapshots demonstrate Hubble's return to full science operations, following correction of a computer anomaly aboard the spacecraft. These two peculiar galaxies are part of a program led by Julianne Dalcanton of the University of Washington in Seattle, to survey oddball galaxies scattered across the sky.
Science: NASA / ESA / STScI / Julianne Dalcanton (UW); Image processing: Alyssa Pagan (STScI)

It has been a difficult past few weeks for NASA’s famous Hubble Space Telescope, but on Saturday, July 17th, engineers announced that the switch to the backup computer system was successful, and that Hubble is once again operational.

“Hubble is an icon, giving us incredible insight into the cosmos over the past three decades,” says NASA Administrator Bill Nelson in a recent press release. “I’m proud of the Hubble team, from current members to Hubble alumni who stepped in to lend their support and expertise.”

The current round of problems started on June 13th, when a fault in the payload computer placed the telescope in safe mode, suspending science operations. Hubble has a completely redundant backup system. One of the initial suspects was a degraded memory module, but switching to onboard backups did not solve the issue. Engineers then came up with a plan to switch over to backup hardware, installed in 2009 on Hubble's last servicing mission during STS-125 space shuttle Atlantis. This switch was moderately risky, as the backup system hadn't been turned on since installation more than a decade ago.

In continuing investigations, NASA engineers discovered last week the probable cause of the malfunction: a faulty power control unit. When it is functioning properly, the power control unit guarantees a steady power supply to the payload computer, but a problem with the unit caused it to tell the computer to cease operations. The backup payload computer contains a completely separate power control unit.

With the switch over successful, Hubble made the first new set of observations in more than a month on Saturday afternoon, after instrument calibration checkouts were complete. Observations missed during troubleshooting and repair will be rescheduled to a later date.

Hubble Space Telescope
Hubble in the payload bay of space shuttle Atlantis, during the telescope's final servicing mission.

Launched in 1990, Hubble has been operating in space for 31 years. In that time, it has made more than 1.5 million observations, and astronomers have made use of its data in more than 18,000 scientific papers. An entire generation of modern professional astronomers have come of age with Hubble. As it enters its fourth decade of operation, Hubble should now overlap with the James Webb Space Telescope, set to launch in November.

Hubble is back in business, and the final tale of its saga is yet to be written.


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Peter Wilson

July 19, 2021 at 2:19 pm


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July 19, 2021 at 10:58 pm


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