The Discovery astronauts chased down the crippled Hubble Space Telescope today, plucked it out of open space and mounted it on a repair stand in the shuttle's cargo bay for a crucial orbital repair job.

At the moment of capture, both spacecraft were streaking through space at five miles per second, 370 miles above the Gulf of Mexico just south of Houston.

With Hubble locked down in Discovery's cargo bay, the stage is set for the first of three back-to-back spacewalks, starting Wednesday afternoon, to install six new gyroscopes and other critical equipment intended to give the telescope a new lease on life. The observatory has been in a protective form of electronic hibernation since a gyro failure Nov. 13 that left it without the minimum of three needed to carry out astronomical observations.

Today's high-flying retrieval was slightly more difficult than originally anticipated because of the very gyroscope failures that necessitated Discovery's quick-response repair mission. Had Hubble been fully operational, its aft would have been pointed at the center of the Earth and Cmdr. Curtis Brown would have carried out a straightforward approach from below, rising up until the shuttle's robot arm could simply lock on.

But in protective safe mode, the telescope's electronic brain was focused solely on keeping the observatory and its electricity-generating solar arrays oriented perpendicular to the sun. Without the gyros, the telescope slowly rotated through space at about one revolution per hour. To simplify today's retrieval, backup gyros were activated that all but eliminated the rotation while keeping the arrays properly oriented.

That allowed Brown to fly around to properly position Discovery's robot arm, allowing French astronaut Jean-Francois Clervoy to snare the telescope.

Astronauts Steven Smith and John Grunsfeld are scheduled to venture into Discovery's cargo bay at 2:40 p.m. Wednesday to complete the top priority of the 96th shuttle mission: Installation of six new gyroscopes valued at $8 million. They also plan to install six voltage regulators to keep Hubble's batteries from overheating.

Astronaut Michael Foale and Swiss flier Claude Nicollier will carry out a second spacewalk Thursday to install a new flight computer and a refurbished guidance sensor, one of three such devices that help Hubble lock onto its targets.

Smith and Grunsfeld will wrap things up Christmas Eve with installation of a new radio transmitter, a solid-state data recorder and insulation panels to repair areas where blankets have deteriorated after years in the harsh environment of space. If all goes well, the refurbished Hubble will be released back into open space on Christmas Day. The astronauts plan to return to Earth Dec. 27.