With the successful landing of Discovery, NASA now turns its attention to the final flights of Endeavour and Atlantis. Both flights will carry some controversy and a heavy share of emotion.

Endeavour's last flight – STS-134 in NASA-speak – is targeted for launch on April 19, assuming there are no mechanical hiccups like those that plagued Discovery's launch attempts last year. The flight will take a canister of supplies and the long-delayed Alpha Magnetic Spectrometer (AMS). Designed measure cosmic radiation will shed light on the presence of antimatter and dark matter in the universe, a simplified first version of the AMS flew aboard a Shuttle mission in 1999. 

AMS version 2.0 was supposed to fly to the International Space Station (ISS) in 2003 but was bumped off the flight manifest after the loss of Columbia, with higher priorities given to finishing the space station and getting a final servicing flight to the Hubble Space telescope. Building the new 15,000 pound instrument ran up a price tag (News - Alert) of $1.5 billion dollars, including considerable contributions from Europe and Asia.

Lobbying and a media campaign ensued, with Congress adding a "final" space shuttle flight in 2008 to deliver AMS, along with a bunch of large spare parts to be stockpiled on board the ISS; a new freezer and a sensor test for the Orion capsule.

Mission Commander for STS-134 is Mark Kelly, husband of critically wounded Congresswoman Gabrielle Giffords.   After his wife was shot by a gunman in January, Kelly spent a month with her before resuming training in February. He expects Giffords to be well enough to attend the launch.

The final-final Space Shuttle flight should be STS-135, the flight of Atlantis. Originally, Atlantis was scheduled to simply be ready as an emergency rescue flight for STS-134, but NASA officials started thinking "Well, we have the External Tank, we have the everything else, the ISS could use more supplies since commercial cargo flights haven't been moving as swiftly as we expect..."

Congress tacked on authorization for STS-135 in July 2010, but the flight still does not have official congressional funding. NASA managers have already started vehicle prep and are hoping to launch on June 28 this year in anticipation that Capitol Hill will figure out how to provide the cash.

When it leaves the pad, Atlantis will carry four astronauts, a logistics module to deliver supplies and spare parts to the ISS, and a robot refueling experiment. The reduced crew size means more payload to deliver ISS, but also is necessary in case of a problem with Atlantis not being able to safely to return to earth.   In case of a problem, the plan would be to return the Atlantis crew via Russian Soyuz capsules docked at the ISS.

Atlantis is expected to spend 12 days in orbit and if all went according to schedule, the last flight of the craft and the Space Shuttle program would end on July 10.