The storied Hubble telescope has gone into ‘safe mode.’ Here’s NASA’s plan to keep it alive

Sign up for CNN’s Wonder Theory science newsletter. Explore the universe with news on fascinating discoveries, scientific advancements and more.

The Hubble Space Telescope will transition to a new way of operating that aims to prevent the space observatory from experiencing lapses in its ability to observe the universe, according to NASA officials.

The storied telescope, which has captured breathtaking images of the cosmos for 34 years, has traditionally operated using six gyroscopes. These gyroscopes, or gyros, are part of a system that controls and determines the direction the telescope is pointed in, said Mark Clampin, director of the Astrophysics Division within NASA’s Science Mission Directorate, during a news conference Tuesday.

As Hubble shifts in direction to capture images of exoplanets, galaxies and other celestial phenomena, the gyros measure the rate of the telescope’s movement so it arrives in the right place for the next science observation, Clampin said.

As the telescope has aged, the gyros have required replacement, and six new gyros were installed during the final Hubble servicing mission that astronauts aboard a NASA space shuttle conducted in 2009.

NASA's Hubble Space Telescope eyes the universe in May 2009 after one of the space shuttle missions to service the space observatory. - NASA
NASA's Hubble Space Telescope eyes the universe in May 2009 after one of the space shuttle missions to service the space observatory. - NASA

Over time, some of the gyros have stopped functioning, but three have remained operational, making no change to how the telescope operates — until now.

Faulty readings disrupt Hubble

Over the past six months, one of the three remaining gyroscopes has been returning faulty readings that have caused the telescope to enter “safe mode” multiple times and cease its observations of the universe, Clampin said.

The Hubble team has been able to reset the gyro from the ground, but these fixes have been temporary, and the problem has appeared more frequently, said Patrick Crouse, the Hubble Space Telescope’s project manager at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

The telescope entered safe mode on May 24 after another faulty event with the problematic gyro, and it remains that way, Crouse said.

After careful consideration, the Hubble team decided to operate Hubble using a single gyro, and the other functioning gyro will be kept in reserve for future use, Clampin said.

The team has long considered shifting the telescope to one-gyro mode to prolong its lifespan after developing the plan more than 20 years ago.

“We believe this is our best approach to support Hubble science through this decade and into the next since most of the observations in space will be completely unaffected by this change,” Clampin said.

Hubble operated in two-gyro mode from 2005 to 2009, and one-gyro mode for a short time in 2008 with no impact on the quality of science observations, according to the agency.

The future of Hubble’s observations

The change doesn’t come without limitations, Crouse said.

The telescope will need more time to shift and lock onto the objects it is observing, which reduces its efficiency and flexibility. It also won’t be able to track moving objects that are closer to Earth than Mars, but historically, Hubble has rarely observed such targets, Crouse said.

Now, the team will reconfigure both the telescope and the ground system that sends information to Hubble. The goal is to restore Hubble to routine observations by mid-June.

Previously, there was a feasibility study to assess how commercial partners could help boost Hubble to a higher orbit to buy the telescope more operational time so Earth’s atmosphere doesn’t tug it down for a controlled reentry in the 2030s. The agency is looking at the risks and requirements of such a maneuver but is not moving forward with any plans of a “reboost” at this time, Clampin said.

Hubble is expected to operate into the mid-2030s, with its cosmic observations providing a complement to the work of the James Webb Space Telescope and future observatories that haven’t launched yet, Clampin said.

“We do not see Hubble as being on its last legs,” Crouse said, “and we think it’s a very capable observatory.”

For more CNN news and newsletters create an account at