The Hubble Space Telescope entered safe mode on Friday, October 5 following a gyro failure. The telescope is, however, expected to return to service and remain operational for several years.
NASA’s Hubble Space Telescope spacecraft utilises its gyroscopes to point and steady the telescope. Ideally, the telescope requires three gyros for optimal performance. However, scientific operations can continue with just one functioning gyro.
Following the fourth servicing mission completed in 2009, six new gyros were installed aboard the Hubble spacecraft. Prior to this latest gyro fail two of the six had already failed. As a result, the telescope currently only has three operational gyros.
Two of three remaining gyros are running and after the latest failure, the last operational gyro should have been powered on. However, telemetry from the spacecraft has indicated that it’s currently not operating at the level required. As a result, Hubble has remained in safe mode while engineers at NASA’s Goddard Space Flight Center and the Space Telescope Science Institute study the problem.
If it is determined that the third operational gyro is unusable, Hubble will be placed in a “reduced-gyro” mode utilizes just one gyro. Although this will ensure the telescope remains operations for potentially years to come, the “reduced-gyro” mode would offer less coverage. NASA officials have, however, stated that this would have a “relatively limited impact on the overall scientific capabilities.”
Hubble’s history of issues
This is not the first potentially impactful issues the Hubble Space Telescope has suffered. Weeks after Hubble was launched, the images that operators received indicated a serious issue with the telescope’s optical system. After analysis of the images, engineers discovered that there was a problem with the shape of the primary mirror. As it was impractical to replace the primary mirror, new optical components were designed to counteract the flaw. Three years after the telescope was launched, the new components were successfully installed by the crew of the Shuttle Endeavour during STS-61.
However, today we do not have the same capabilities for in-orbit servicing as we did two decades ago, or even a decade ago. The Space Shuttle offered a unique set of capabilities including a stable base for a number of weeks, a robotic arm, and a large crew complement. Not only do we not have those capabilities in any spacecraft currently in service, but there are also no spacecraft in the development or even concept stages that could fulfil those requirements.