Categories: Hubble

Hubble is Back Online — Partially

The Hubble Space Telescope has been in ‘safe mode’ since October 23, with all of the science instruments offline and unavailable for observations. However, engineers have now been able to bring one instrument, the Advanced Camera for Surveys (ACS), back online, and have restarted its science observations. NASA said engineers are still investigating the issue as the other four instruments remain offline.

The underlying cause appears to be a “synchronization error” which means the instruments could not sync up to collect data properly. An earlier update from NASA said the root cause appeared to be a timing problem in the command flow. But the Hubble team has remained confident throughout this latest glitch that the instruments are all still in good health, and the recovery of the ACS is bolster for their continued work on the issue.

Safe mode is designed to keep the telescope stable and allow it to remain powered via its solar panels while the engineering team works through the technical issues.

Hubble has gone through a series of technical problems recently. In June of this year, a malfunctioning main computer required operators to switch to a backup copy, causing five weeks of downtime. In March 2021, an issue with a software update took the spacecraft offline for a few days. This may be par for the course for the aging observatory.

Astronaut Mike Good works on repairing the Space Telescope Imaging Spectrograph during the final Hubble servicing mission in May 2009. Periodic upgrades have kept the telescope equipped with state-of-the-art instruments, which have given astronomers increasingly better views of the cosmos. Credits: NASA

Hubble has been in space since 1990 and has revolutionized our understanding of the cosmos. With the five servicing missions by Space Shuttle astronauts to repair and replace systems on the telescope — including all five of the main instruments – the observatory has basically been completely upgraded since it launched. But the last servicing mission was in 2009, and Hubble’s age is becoming apparent.

NASA said that over the past week, the mission team has continued investigating the root cause of the synchronization issues and has seen no additional problems. The team will continue looking into possible short-term solutions this week and develop estimates for implementation. Once this occurs, the team will discuss returning the other instruments to operational status and resuming their science observations.

You can see the latest Hubble status reports here.

Nancy Atkinson

Nancy has been with Universe Today since 2004, and has published over 6,000 articles on space exploration, astronomy, science and technology. She is the author of two books: "Eight Years to the Moon: the History of the Apollo Missions," (2019) which shares the stories of 60 engineers and scientists who worked behind the scenes to make landing on the Moon possible; and "Incredible Stories from Space: A Behind-the-Scenes Look at the Missions Changing Our View of the Cosmos" (2016) tells the stories of those who work on NASA's robotic missions to explore the Solar System and beyond. Follow Nancy on Twitter at and and Instagram at and

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