Aging Hubble Telescope Moves To 'One-Gyro' Operations

The 34-year-old Hubble Space Telescope is now operating with its final two working gyroscopes, necessitating a switch to a less productive "one-gyro" mode to extend its operational life. This contingency plan will reduce Hubble's productivity by over 12%, limit its ability to track fast-moving objects, and decrease the portion of the sky it can observe. That said, NASA expects it to keep functioning through 2035. Science.org reports: Normally, Hubble measures its location in space with a system that includes three gyroscopes -- rapidly spinning wheels that can sense forces in three directions. But in a 4 June press conference, NASA officials said one of the telescope's three remaining gyroscopes is on the fritz. The agency is now invoking a contingency plan: a "one-gyro" mode that keeps the other functioning gyroscope in reserve. The mode will reduce the telescope's productivity by more than 12% but preserve its ability to observe for years to come, Mark Clampin, NASA's astrophysics division director, said at the press conference. "We believe this is our best approach to support Hubble science through this decade and into the next." Hubble's gyroscopes, which spin at 19,200 revolutions per minute, are extremely precise but finicky. The agency has flown a total of 22 gyroscopes across various servicing missions and is now down to the last two of the six currently onboard. In one-gyro mode, Hubble must rely on its less precise star trackers and other sensors to verify its position, a slower process that leads to reduced productivity. "It will take us more time to slew from one target attitude to the next, and to be able to lock on to that science target," said Patrick Crouse, Hubble's project manager at NASA's Goddard Space Flight Center. A one-gyro Hubble will also struggle to track fast-moving targets, such as asteroids within the orbit of Mars, and to swivel to spot transient distant phenomena such as supernovae, according to a 2016 report (PDF) from the Space Telescope Science Institute, which operates Hubble. In addition, the inefficiencies of one-gyro mode will reduce the portion of the sky that Hubble can safely point to at any given moment, from 82% to roughly 40%, including a larger avoidance zone near the Sun. It won't be able to observe Venus or the Moon, nor will it be able to reliably spot comets when they're near the Sun. Its ability to scrutinize distant exoplanets will also be hampered, especially in gathering the spectral measurements used to discern alien atmospheres. Furthermore, a one-gyro Hubble won't be able to perform as many simultaneous observations with the new JWST space observatory. Moving forward, the two telescopes' fields of view at any given moment may overlap by less than 20%, according to a 2019 estimate anticipating this event from a Hubble advisory committee.

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