Hubble Space Telescope: Eye wide open

The world’s most prominent stargazer is back in business.

Astronauts replaced failed gyroscopes on the Hubble Space Telescope during a repair mission last month. NASA

Two months after a fourth gyroscope failure robbed the Hubble Space Telescope of its cosmic view (SN: 11/27/99, p. 341), the $1.5 billion observatory has resumed operations, NASA announced last week.

During a 9-day repair mission late in December, shuttle astronauts replaced the telescope’s six gyroscopes and installed a 486-microprocessor computer—primitive by earthly standards but of proven reliability in the harsh environment of space. They also added new battery components and a solid-state tape recorder and upgraded the telescope’s guidance system.

The crew worked in pairs during three space walks, with day passing into night and back into day every 97 minutes. One astronaut’s foot remained strapped to the shuttle’s grappling arm while the other astronaut floated inside the telescope.

Delayed 12 times due to faulty wiring and other problems with the shuttle fleet, the mission finally took off on Dec. 19. That was the last day in 1999 that NASA said it could send up the shuttle without fear of running into a Y2K computer problem.

Since last January, Hubble had been operating with just three gyroscopes, the minimum required to accurately point the telescope. That dicey situation had prompted NASA to propose a repair mission for last October. On Nov. 13, a fourth gyroscope failed, leaving Hubble too jittery to make observations. To save time, NASA relied on the same navigation software on the shuttle that it had used for a 1997 Hubble repair flight. It was Y2K certified just before the launch.

As it was, NASA eliminated a fourth space walk to ensure that the U.S.-European crew returned to Earth on Dec. 27, in time to power down shuttle and ground software before the New Year. That meant that the crew put protective sheets of insulation over fewer electronic instruments than they had intended and abandoned plans to cover cracks in Hubble’s skin with a wallpaperlike fabric.

Those tasks will have to wait until the next servicing mission, now scheduled for 2001, says Hubble senior project scientist David S. Leckrone of NASA’s Goddard Space Flight Center in Greenbelt, Md. During that mission, astronauts plan to replace Hubble’s wide-field and planetary camera with an advanced survey camera and install a new cooling system to revive the near-infrared camera that failed a year ago.

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