The Hubble Space Telescope looks like the comeback kid of the decade.
Just two years ago it was doomed to die when the shuttle mission to service it was canceled, one of the first casualties of NASA budget tightening to finance President Bush's ambitious Moon-Mars mission vision.
The mission was also deemed too risky to fly by former administrator Sean O'Keefe.
But political pressure and the emergence of a new NASA administrator who once worked on the Hubble revived hope that the celebrated telescope could be saved with one more shuttle mission, scheduled now for spring 2008.
On Tuesday, NASA officials are expected to announce plans to repair the Hubble in the mission.
NASA administrator Michael Griffin spent last Friday listening to an engineering team debate the pros and cons of a mission to service Hubble.
Earlier this summer, Griffin said Hubble was a priority for him.
"Hubble is one of the great observatories," he said. "It has revealed fundamental things about the universe of which we had no idea, and would have had no idea. It is one of the great scientific instruments of all time. It is not outmoded. It needs some refurbishment and repair."
Training Already Under Way
Tuesday's expected formal announcement will come as no surprise to the flight control team, which has already been training for this mission.
Flight director Tony Ceccacci will head the team choreographing this very complicated service mission.
Astronaut Mike Massimino, who flew on the last mission, has spent the last few months training the crew who will fly on SMA4 -- though he politely declined to reveal who was training for this mission.
The identity of the crew will be revealed at a news conference Tuesday.
The Hubble mission will require five back-to-back spacewalks.
One of the most complicated will be fixing an instrument called the Space Telescope Imaging Spectrograph. There won't be enough time to build a replacement imaging spectrograph, so the astronauts will have to repair this very delicate instrument in place.
Remember the fuss when two bolts were lost on the last shuttle mission?
The Hubble astronauts will have to remove 110 very tiny fasteners to fix the imaging spectrograph. Engineers have designed a plastic capture plate to grab those tiny screws and keep them from becoming space debris.
Massimino says he believes saving Hubble is the right thing to do.
"Hubble helps us answer so many questions. Where are the stars? Where have galaxies collided?" he said. "It tells us about black holes, and the images are so powerful one of the pictures showed up on an album cover for Pearl Jam."
What's the hitch? Since the Columbia accident, one of the requirements for future shuttle flights was a rescue option.
NASA satisfied that requirement by designating the International Space Station as a safe haven for future shuttle crews, should something go wrong with the shuttle.
Hubble and the space station circle Earth in different orbits, so it would be impossible for a crew visiting the Hubble to get to the space station and wait for rescue.
Space Shuttle Program manager Wayne Hale has suggested solving that problem by having a second shuttle on the other launch pad at the Kennedy Space Center ready for liftoff when the Hubble mission takes off.
SMA4 will be the fifth and final shuttle mission to Hubble.
Two spacewalking crews will replace the telescope's failing batteries and gyroscopes, and a wide field camera that will help Hubble see farther into the universe.
How risky is the mission to save Hubble?
Consider this: NASA launched Hubble with no problem, and has sent four shuttle missions to service Hubble.
Adm. Hal Gehman, who headed the investigation into the Columbia accident for NASA, also examined the risk of flying to Hubble for a congressional committee.
"Shuttle flights are dangerous, and we should fly the minimum number necessary," he said. "Almost all the risk is concentrated in the front and back of the mission. Where one goes on orbit makes little difference."
But this mission will make a difference to Hubble by extending its usefulness life into 2013.
By then, the James Webb telescope should be ready for launch and set to take the Hubble's place in space.