From Space.com

CAPE CANAVERAL, Fla. -- Columbia’s astronauts are in hot pursuit of the Hubble Space Telescope, but a faulty shuttle coolant line could force NASA to order the crew to abandon their $172 million servicing mission.

STS-109
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Just 90 minutes after Columbia rocketed away from Kennedy Space Center early Friday, flight controllers noted that the flow of coolant within one of two crucial shuttle radiators appeared to be restricted.

And if mission managers declare the Freon coolant loop failed, strict NASA flight safety rules call for the shuttle to land back on Earth at the earliest opportunity.

Senior NASA managers will meet late Friday to determine whether the problem is severe enough to call off a planned rendezvous Sunday with the storied observatory.

The crew will get the news when they wake up Friday night for their first full day in orbit.

"First thing in the morning, we’ll give you the outcome of their discussion," Canadian astronaut Steve MacLean told the crew from NASA’s Mission Control Center in Houston. "And we’re all hoping that we can rendezvous with the Hubble and fix it."

The potential mission showstopper cropped up just before the shuttle’s two cargo bay doors swung open about 85 minutes after a sunrise liftoff from Kennedy Space Center.

A warning message seen on computers both onboard Columbia and in Mission Control showed that the flow of coolant within the shuttle’s portside radiator had dropped to a level that approached safety limits.

The coolant flow returned to normal once the clamshell-like doors opened. But engineers suspect that the problem could crop up again when the doors are closed prior to a return to Earth.

The coolant loops within the two radiators -- which are located on the inner side of each of the doors -- are considered key to cooling sensitive spaceship electronics throughout a flight and during a supersonic dive back through the planet’s atmosphere.

The flight rule calling for a quick return to Earth aims to guard against the chance that both shuttle radiators might break down during orbital operations.

A similar situation cropped up during Columbia’s last flight, a July 1999 mission to deploy NASA’s $1.5 billion Chandra Observatory, a Hubble-class x-ray telescope.

In that case, restricted coolant flow was seen in the same port radiator, but the five-day mission went on as planned. Columbia’s flight is slated to last 11 days.

Another mission-threatening problem also cropped up -- but was overcome -- as the crew moved to open the ship’s inner airlock hatch, the initial orbital portal for the astronauts who will be servicing Hubble.

Working side by side with crewmate James Newman, Altman tried to turn a hatch handle but simply couldn’t get the hatch to unlatch during an initial attempt. But Newman gave it a try and quickly reported success.

"I fixed it," Newman radioed down to Mission Control. "What I did this time is when I went to unlock, I kept the handle hard and flush against the airlock, and the handle is now rotating effortlessly."

"That’s excellent news," MacLean called back.

Columbia suffered a similar problem during a November 1996 mission when astronauts Tom Jones and Tammy Jernigan couldn’t get the airlock hatch to open. A spacewalk planned for the flight had to be scrapped as a result.

A stuck airlock hatch, meanwhile, would prevent Columbia’s telescope repair crew from setting out on any of five planned spacewalks.

The double dose of trouble came on the heels of a virtually flawless dawn launch from NASA’s Kennedy Space Center.

Fresh off a $100 million overhaul, the veteran spaceship blasted off at 6:22 a.m. EST (1122 GMT), punching its way through partly cloudy skies as it arced out over the Atlantic Ocean and rocketed into orbit.

The $3 billion Hubble telescope could be seen passing 362 miles (579 kilometers) over the launch site as Columbia climbed toward orbit, the ship’s twin solid rocket boosters trailing sunlit white contrails as they tumbled toward the ocean.

"It was something that was a sight to behold -- absolutely extraordinary," said new NASA Administrator Sean O’Keefe, a former White House budget official who was attending his first shuttle launch.

"We saw them almost all the way to splashdown, which was unprecedented, as far as I’m concerned," added NASA shuttle launch director Mike Leinbach. "It was just a beautiful launch."

The launch set the stage for one of the most ambitious shuttle missions in NASA history.

During the planned spacewalks, the astronauts aim to equip Hubble with a fresh set of solar wings, install a new planetary camera, resuscitate a dead science instrument, replace a faulty pointing control device and overhaul the observatory’s electrical system.

"They’ve got an important mission ahead of themselves," O’Keefe said. "They’re up there now on their way to five spacewalks in order to service the Hubble telescope, and that’ll be a historic event all by itself."

A shortened flight, on such a high-stakes mission, would be historic, too. Only three shuttle flights to date have been cut short by technical problems, two for fuel cell failures and the other when a key guidance control unit broke down in orbit.

As it stands, Columbia and its crew remain scheduled to rendezvous with the 13-ton telescope at 4:14 a.m. EST (9:14 GMT) Sunday. A full mission would lead to a landing here at NASA’s coastal Florida spaceport on March 12.