The Hubble Telescope Is Back Online a Month After Going Dark

Science operations are expected to resume within days, according to the mission team.
July 16, 2021, 2:33pm
Science operations are expected to resume within days, according to the mission team.
The Hubble Space Telescope. Image: NASA/Smithsonian Institution/Lockheed Corporation
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Space lovers around the world breathed a collective sigh of relief on Friday, after NASA announced that the Hubble Space Telescope was brought back online more than a month after the iconic observatory halted operations due to a malfunction with its primary computer, which sparked speculation and concerns about its fate. 

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“Hubble is back!” said Tom Brown, Hubble’s mission head, in an early morning email to his colleagues, reports Science. “I am excited to watch Hubble get back to exploring the universe.”

Hubble shut down on June 13 when its primary computer, which controls the science instruments onboard the spacecraft, stopped receiving a “keep-alive” signal that coordinates communications between all the telescope’s computers. Since then, Hubble has remained offline to allow the mission team to perform diagnostics tests that might isolate the problem. NASA has kept an updated log of the ongoing procedures at this link.

Operators had originally hoped to fix the primary computer, but they have changed course after weeks of failed attempts to resolve its issue. The problem appears to be the primary Power Control Unit (PCU), which is supposed to supply steady voltage levels to the telescope’s hardware. The voltage has fallen outside of its normal levels for reasons that the team is still investigating, leaving the primary computer with signals that it should cease operations.

Fortunately, NASA builds many redundancies into its spacecraft, and Hubble is equipped with a backup computer system and PCU. The observatory was successfully switched over to the secondary system on Thursday, and mission leads are now running tests to ensure all backups are operating normally. It may take a few days for the telescope’s instruments to be taken out of safe mode and calibrated, but NASA expects the mission’s science goals to resume shortly.

Hubble’s ordeal over the past month is a reminder of both the advanced age of the telescope, as well as its remarkable resilience. The computers onboard Hubble were designed and built in the 1980s, and the observatory was launched into orbit a generation ago, in 1990. Over the decades, Hubble has experienced a variety of technical failures and close calls that required repairs and upgrades, but it has managed to survive them all, maintaining its position as one of the most influential science instruments in history.  

NASA is now preparing to launch Hubble’s successor, the James Webb Space Telescope, within the next year, which will provide an even more spectacular and high-resolution view of our universe. But as space lovers around the world celebrate Hubble’s presumed return to observations, it’s clear that no telescope will ever be able to replace this juggernaut workhorse mission in the minds and hearts of so many.