Credit: NASA

Preparations for a shuttle mission to upgrade and repair the Hubble Space Telescope in late 2007 or early 2008 are picking up steam as engineers map out the details of a five-spacewalk flight designed to keep the venerable observatory alive and well through at least 2013.

Servicing Mission 4, canceled by former NASA Administrator Sean O'Keefe in January 2004, is expected to be officially reinstated by current Administrator Mike Griffin if the next shuttle mission, STS-121, goes smoothly and if ongoing analyses show the flight can be conducted in relative safety.

"For any given single mission, I would say that the Hubble servicing represents the highest priority utilization of a single shuttle mission that I can conceive," Griffin said in a recent interview. "Because servicing the Hubble is something only the shuttle can do, it's only one flight and is, therefore, I think a very high agency priority if we can do it technically."

That will depend on whether engineers can resolve the foam shedding problem that grounded the fleet after Discovery's return-to-flight mission last July and whether shuttle planners can figure out how to carry out thorough inspections of a shuttle's heat-shield tiles in the absence of help from the space station.

It also will depend on NASA's level of comfort launching a crew with only rudimentary heat shield repair techniques and no practical way to mount a rescue mission.

Hubble and the station circle the globe in different orbits and a shuttle crew sent to the telescope would not be able to use the station and its crew for inspections, repairs or safe haven in the event of major damage that might prevent a safe re-entry.

But engineers are confident a Hubble crew can carry out its own inspections, using the ship's robot arm and instruments mounted on the end of a long boom. They believe the foam problem will, in fact, be successfully resolved. And, contrary to early interpretations of a key recommendation of the Columbia Accident Investigation Board, Griffin said certified tile and reinforced carbon carbon wing leading edge repair techniques will not be required for a flight to Hubble.

"We're certainly not putting a certified repair capability in series with flying the shuttle to the Hubble or anything else," he told CBS News. "The spirit of the recommendation was to the extent possible, we should develop a shuttle tile repair capability. And we've spent many, many millions of dollars, I'm tempted to say tens and hundreds of millions of dollars, on shuttle tile repair.

"At some point, what you have to honestly say is it's a capability that's so far eluded us. Not every recommendation that a failure board makes is something that can be done. It's sort of like you can tell me I have to be smarter, but achieving that is a more difficult goal.

"And so, we, NASA, and the contractor community have not yet been able to develop the technology for a workable tile repair solution," Griffin said. "We've got some promising candidates, but we would not say that we're there. So we're going to continue to do the best we can, but it can't be in series with flying the shuttle or we'll never fly."

Instead, the Hubble astronauts will have whatever repair materials and procedures are available at the time, techniques that would be able to cope with minor foam/debris strike damage. Engineers do not expect to have any viable repair procedures for major, Columbia-class impact damage.

As a result, astronauts visiting the space station would have a better chance of survival if major damage did, in fact, occur because the station, as it matures, will be increasingly able to support stranded crews until a rescue mission could be launched.

Wayne Hale, shuttle program manager at the Johnson Space Center, says NASA likely would not be able to launch a rescue mission for a stranded Hubble crew even if a second shuttle was ready to go. That's because one of the agency's two shuttle launch pads likely will be out of action by then - either mothballed to save money or undergoing modifications to support the new Crew Exploration Vehicle. And without that second pad, there would not be enough time to haul a second shuttle to the remaining pad and get it launched before a stranded Hubble crew ran out of critical supplies.

That's not necessarily true for station-bound crews. When Discovery took off last July, the station had enough supplies on board to support an expanded crew for about six weeks. A second shuttle had been prepared for launch and had it been needed, a rescue mission could have been launched in time to bring the stranded crew home.

NASA cannot keep a second shuttle on standby for more than a couple of more missions. But by the time Hubble flies, the station should be able to support crews from 60 to 90 days, enough time to get a rescue shuttle launched even with one operational pad.

"If we can get it out to 90-plus days, then we are basically home free for the rest of the program," Hale said. "If it's in the 60-day kind of time frame, then we can probably talk for the near term some minor impacts."

So in Hale's view, station flights offer more options to save the crew of a damaged shuttle than non-station flights like Servicing Mission 4. Even so, Hale would support a Hubble flight if upcoming launches are free of major foam shedding.

"What I would have to be satisfied with, basically, is that we have put the kibosh on foam coming off the tank," Hale said in a telephone interview. "I mean, that is really the key thing. If you think that you have reduced the risk significantly of needing either repair or a rescue flight, then I feel very comfortable launching with (repair) limitations. So by the time you get to the 10th flight down the road, philosophically we ought to have reached that point where we're very confident we have, in fact, licked our ascent debris problem. Or, we probably ought not be flying."

That said, if the next shuttle flight goes off without any major foam loss, "I think we can kick off Hubble planning in a serious way," Hale said.

But the final decision is Griffin's.

"It's not really so much about foam shedding, although we do need to make sure that our fixes have that under control," the administrator said. "But it's also about looking at crew timelines for inspections."

"Bear in mind, if we do the Hubble flight we won't have the space station crew available to do the tile inspections (on the shuttle's belly). That we would have to do with the shuttle crew alone using a camera on the end of a manipulator arm and things like that. So we need to satisfy ourselves that just operating the shuttle within itself and using our new safety-of-flight guidelines that we can do everything we need to do in the context of the available crew resource timeline that we've got."

In the meantime, Hubble engineers at the Goddard Space Flight Center in Greenbelt, Md., plan to meet with their shuttle counterparts at the Johnson Space Center in Houston later this month to discuss the flight in detail. And astronauts will begin working through spacewalk scenarios in late January or early February in a giant pool used to simulate weightlessness..

"We'd like to make the decision (to fly SM-4) after we fly the next flight," Griffin said. "We think we'll have all the pieces in place and that will be the last piece. Bear in mind, we're already working on that mission and the phrase I once used was 'betting on the come.' We received congressional direction in '05 to spent up to $291 million on the Hubble servicing mission, so I've had people working at Goddard on that mission since I arrived and they are continuing to work in '06.

"The Congress elected to risk some of the nation's money on a presumption that we would be able technically to do a Hubble flight," he said. "And I support that, I mean, I've said nothing other than that I support that decision on their part, precisely because we needed to get started ... if we were going to be able to do the mission by early '08."

The current target launch date is December 2007. In the latest internal shuttle manifest, which lists 18 flights to the space station and then the retirement of the fleet in 2010, SM-4 - the only non-station mission on the books - is listed as the 10th flight in the sequence.

"If we waited until after STS-121 to even start talking about it, we'd end up with a big bow wave of integration work," said Chuck Shaw, SM-4 mission director at the Johnson Space Center. "So what we're doing is starting that integration work to make sure that hopefully, right after 121, Mike can make a formal announcement that we're back to flying and we feel good about it and good enough that we can add an HST servicing mission."

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