In Endeavour’s Final Act, the Supporting Cast Draws Outsize Attention

Captain Kelly said on arriving at the space center from Houston that Ms. Giffords, who has spent the past three months in a Houston rehabilitation hospital recovering from being shot in the head in an assassination attempt, would be coming to Florida “pretty soon.”

“It’s something she’s been looking forward to for a long time,” he told reporters gathered here for the launching, scheduled for 3:47 p.m. Friday. “She’s been working really hard so that her doctors would permit her to come.”

Captain Kelly and five other astronauts are to lift off on Friday for a 14-day mission to the International Space Station. His wife will watch from a private viewing area, and aside from a possible news photograph or two of the scene, the public will not get a glimpse of her.

But her expected appearance — her doctors cleared her for travel early in the week — has made this liftoff, the next-to-last in the shuttle program, one of the most anticipated in years.

Her plans have overshadowed the expected appearance of President Obama — which would be the first in-person viewing of a launching by a president since 1998 — and the details of the mission itself, which is to deploy a particle-physics experiment that is one of the most ambitious and expensive scientific instruments ever lofted to orbit.

So far, preparations for this mission have been relatively free of the kinds of technical problems that have delayed shuttle flights in the past. On Tuesday, NASA officials were optimistic about the weather for Friday, although they said there was a potential for high winds that could force a postponement for a day or longer.

Mr. Obama’s visit to the center will be his first since last April, when in a speech he tried to win over NASA employees for his administration’s blueprint for space exploration. It was a tough sell, since those plans called for scrapping a program to return to the Moon in favor of a longer-term goal of exploring deeper space. He also called for a shift to private companies and away from NASA in the development of new space hardware.

Since the speech, the administration and Congress canceled NASA’s manned launcher project, the Ares 1 rocket. Just last week, NASA awarded $269 million to four companies in a second round of financing to develop new spacecraft to take astronauts into orbit.

As if to underscore the changing nature of the space program, representatives of some of those companies were on hand at the space center this week to discuss their efforts.

But commercial launchings of astronauts are years away. For now, NASA will rely on Russian rockets, this flight of the Endeavour and the final shuttle flight, by the Atlantis, scheduled for late June.

The Endeavour mission is the 134th in the program and the 25th for the spacecraft. The shuttle was built to replace the Challenger, which broke apart shortly after liftoff in 1986, killing all seven astronauts aboard. NASA announced this month that the Endeavour would eventually end up in a science museum in Los Angeles.

But before it heads into retirement it has a busy fortnight ahead. Among the objects in its cargo bay is a box of spare parts for the International Space Station. Astronauts will conduct four spacewalks to perform maintenance on the station, and the mission may be extended two days to perform more upkeep.

But the mission’s most high-profile task is to install a $2 billion particle detector, the Alpha Magnetic Spectrometer, on the space station’s external truss, where it will sit until the station is abandoned, perhaps in 2020 or later.

The spectrometer, the long-gestating brainchild of Sam Ting, a Nobel physics laureate at the Massachusetts Institute of Technology, consists of a giant magnet and detectors that together act as a cosmic sifter, looking for evidence of the elusive “dark matter” that is thought to pervade the universe.

The project has been in the works for nearly two decades, and Dr. Ting and his team of collaborators from 16 countries are hoping for a smooth ascent on Friday after years of what could only be described as a bumpy ride. After the loss of the Columbia and its seven astronauts in 2003, the experiment was pulled from the shuttle program, then resurrected five years later after intensive lobbying by Dr. Ting, who has proved to be as much a salesman as a physicist in his long career.

In the past year, Dr. Ting himself was responsible for another delay in the project, deciding to replace the instrument’s huge superconducting magnet with a weaker one. The reason, he explained at the time, was that the superconducting magnet required liquid helium to keep it cool, and the helium would run out in a few years. The weaker magnet requires no cooling liquid, and can last as long as the station.