NASA announced that it is transitioning the Hubble Space Telescope to operate using only one gyroscope (gyro) to ensure its continued functionality and scientific observations. Currently, the telescope is in safe mode, a state it entered on May 24 due to a malfunctioning gyro. Hubble’s gyros measure slew rates and help control the telescope’s direction. Of the six installed in 2009, three remain active, but one has been providing faulty readings, causing repeated safe mode entries.
This faulty gyro has been experiencing “saturation,” where it falsely reports maximum slew rates regardless of actual movement. Though resetting the gyro temporarily resolved the issue, it reoccurred in late May. To maintain consistent operations, NASA is shifting Hubble to a one-gyro mode, keeping another gyro in reserve.
This mode was planned over 20 years ago to prolong Hubble’s operational life and was briefly tested in 2008 with no impact on observation quality. Previously, from 2005-2009, Hubble operated in a two-gyro mode, which is similar to the one-gyro mode.
Operating in one-gyro mode will introduce minor limitations. The telescope will take longer to slew and lock onto targets and will have less observational flexibility. Additionally, it won’t be able to track moving objects closer than Mars, though such targets are infrequent for Hubble. The transition involves reconfiguring both the spacecraft and the ground system, with science operations expected to resume by mid-June.
Once in one-gyro mode, Hubble is expected to continue making significant scientific contributions alongside other observatories, such as the James Webb Space Telescope and the upcoming Nancy Grace Roman Space Telescope. This change aims to extend Hubble’s mission through this decade and beyond, with most observations remaining unaffected.