Named after a series of historic exploration ships, Discovery made its maiden voyage into space on August 30, 1984. Since then it's logged the most flight hours of any space shuttle in NASA's fleet: Discovery has flown 38 missions into space and spent 351 days in orbit so far.
Over the years the spaceship has earned a reputation among historians and shuttle enthusiasts as the "dependable older sibling" of the shuttle fleet.
"Its legacy is that it is the reliable workhorse," said Robert Pearlman, editor of the space history and artifacts website collectSPACE.com.
"Whenever it's been called into service, it's performed."
Discovery's missions have also been the most varied of any orbiter, said Valerie Neal, space shuttle curator at the National Air and Space Museum in Washington, D.C. (Take an Air and Space Museum quiz.)
"When the first space shuttle was introduced in 1981, it was meant to be an extremely versatile spacecraft that would take care of all of our needs in space for the foreseeable future," Neal said.
"Although other launchers are now also in use"—such as the Atlas and Delta rockets—"shuttles did prove to be extremely versatile, and I think Discovery really embodies that."
Discovery a Machine With Personality
Discovery's upcoming launch is expected to be the second-to-last space shuttle mission, followed only by the scheduled launch of the shuttle Endeavour next February. An additional shuttle mission has been approved by Congress but still faces a funding review later this year.
If ultimately given the green light, the extra mission would most likely involve the shuttle Atlantis lifting off no earlier than June 2011—so either way, this will probably be the last launch for Discovery. (See pictures from the last official mission of Atlantis.)
Watching Discovery's final mission will be especially poignant for collectSPACE.com's Pearlman, who counts the craft as his favorite.
"It's always had a special place in my thoughts," he said. "When I watch it land for the last time, it will be emotional. It's watching a machine, but it's a machine that's taken on a personality over the years." (Find out how to vote for the wake-up songs to be played during Discovery's final flight.)
Technically Discovery was the third of the orbiters to be built, but it's now the oldest working vehicle in NASA's shuttle fleet.
During its missions, Discovery has carried a variety of payloads into space, including several science experiments as well as Department of Defense satellites with still classified purposes.
In 1990 Discovery delivered into orbit one of the crown jewels of modern astronomy, the Hubble Space Telescope, and the shuttle was called upon to repair Hubble when the observatory required servicing in 1997 and again in 1999.
Discovery is also associated with a number of notable firsts in human spaceflight history. It was the first space shuttle to rendezvous with Russia's Mir space station in 1995, the first shuttle to transport a U.S. Congressman into space (Utah senator Jake Garn, in April 1985), and the first U.S. spacecraft to carry a Russian cosmonaut (Sergei Krikalev, in February 1994).
Discovery's crews have included the first African-American mission commander (Frederick D. Gregory, in November 1989), the first woman to pilot a spacecraft (Eileen Collins, in February 1995), and the oldest person to fly in space (a 77-year-old John Glenn, in October 1998).
Discovery also flew the first "return to flight" missions following the loss of Challenger in 1986 and of Columbia in 2003. (See "Space Shuttle Returns to Flight With Discovery.")
"Discovery served as the test bed for shuttle improvements after those [accidents]," such as the inspection boom used to perform the now standard check of a shuttle's undersides before reentry, Pearlman said.
When Discovery embarks on its last mission, the space shuttle will rack up a final first that could be a preview of things to come in space exploration. In addition to carrying a storage module for the International Space Station, Discovery will deliver the first humanoid robot in space, called Robonaut2 (picture).
"It looks like a human and is the first robot designed to assist astronauts, both inside and eventually outside the space station," Pearlman said.
Discovery Bound for Museum Display?
As someone who has witnessed every space shuttle launch, either in person or via live television, Pearlman says watching the space shuttle era draw to a close is bittersweet.
"It's great that the shuttles have performed so well in the last five years since we returned to flight," he said. "But each vehicle was designed to fly a hundred flights, and even Discovery, which has flown the most fights, hasn't flown even half that many."
The trouble, Pearlman said, came from safety concerns with the reusable fleet.
"Before the loss of Challenger in 1986, NASA anticipated flying as many as two dozen shuttle flights per year, including Department of Defense-dedicated flights from a pad at Vandenberg Air Force Base in California," he said.
"After the accident, the flight rate did not necessary drop"—NASA launched nine flights in 1985, the most for a given year, and went on to launch eight flights in both 1992 and 1997—"but they never were as a frequent as first envisioned."
Discovery's fate after its last mission is still unclear, but NASA has stated its intent to hand the orbiter over to the Air and Space Museum's Steven F. Udvar-Hazy Center for public display—if the museum is OK with the cost.
"Once the shuttles are done flying, NASA will 'safe' them by removing [some systems that contain] hazardous chemicals, an invasive process that will leave them unfit for display," NASA spokesperson Michael Curie explained in an email.
"NASA will pay for the shuttles to be safed. However, NASA's budget does not include money to prepare the shuttles for public display by restoring them to their normal appearance, or transporting them to their final destinations.
"The cost for display and transporting them is estimated to be $28.8 million." (Find out about a recent online auction of NASA artifacts.)
NASA expects to make an announcement about Discovery's retirement plans in the coming months, Curie said.