SPACE CENTER, Houston -- Space shuttle Discovery and its seven-man crew were gaining on the crippled Hubble Space Telescope today and gearing up for their big repair job.
The 370-mile-high chase was scheduled to end this evening, when the astronauts seize the malfunctioning telescope with the shuttle's robot arm and tuck it into the cargo bay for three days of work.
Late this morning, Discovery trailed Hubble by 230 miles and was getting closer with each passing orbit.
The most crucial task for the astronauts is replacing Hubble's six gyroscopes, four of which have failed due to corroded wires, shutting down NASA's $3 billion observatory since Nov. 13.
Besides replacing the gyroscopes -- used to aim the telescope and keep it steady -- Hubble will get a new data recorder, radio transmitter, fine guidance sensor and battery-voltage regulators. The new equipment cost $69 million. Along with shuttle and other expenses, the mission is costing NASA more than $200 million.
NASA and astronomers everywhere are eager to get the 9«-year-old Hubble working as soon as possible. The space agency spends $25 million to operate the telescope every month whether it's working or not.
Already, Hubble has missed some 150 astronomical observations. If all goes well, the telescope should be back in action by the second week of January.
It was a relatively quiet day Monday for the astronauts, all but one of whom is a seasoned space flier. They tested Discovery's 50-foot arm in preparation for the rendezvous and checked the spacesuits and tools they will use while working on Hubble. They have about 300 tools at their disposal.
The eight-day mission is the third servicing flight to Hubble, the first coming in December 1993 to correct a blurred lens and the second in February 1997 to add new equipment. Discovery brought the telescope to space in 1990.
Discovery almost didn't make it off the ground before the New Year, sacked with a record nine delays because of bad weather and equipment trouble. The delays mean Discovery will be the first space shuttle to fly over Christmas in the program's 18« years.
It will be mostly work and little play for the astronauts this Christmas: they are scheduled to send Hubble back into orbit at around 6 p.m. EST Saturday.
Shuttle commander Curtis Brown Jr. said the tasks wouldn't keep the crew from celebrating, even if just for a moment.
"We can't tell you all our secrets, but we're looking forward to the deploy of Hubble and if we have a chance to say hello to our families, we'll definitely take advantage of that," Brown said Monday from orbit.
In 38 years of manned spaceflight, NASA has flown only two missions over Christmas: the Apollo 8 mission to the moon in 1968 and the Skylab space station in 1973.
The shuttle is due back next Monday. NASA wants the shuttle back on Earth before New Year's because it does not want to risk Y2K computer trouble.