Discovery set for final landing

By Jonathan Amos
Science correspondent, BBC News

America’s most experienced space shuttle, Discovery, is about to close its remarkable 27-year career.

The orbiter has fired its thrusters to bring itself out of the sky and into a glide path towards the Kennedy Space Center in Florida.

Discovery is destined for a museum on its return – Nasa is retiring its three remaining reusable spaceplanes.

The “leader of the fleet” has been on a 12-day mission to the International Space Station (ISS).

Duties have included delivering a new store room and a sophisticated humanoid robot.

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The ship’s crew also performed two spacewalks to carry out maintenance tasks on the exterior of the platform.

The landing at KSC is timed to occur just before midday local Florida time (1657 GMT).

Within hours of Discovery’s touchdown, Nasa will turn its attention to shuttle Endeavour.

It will roll out of Kennedy’s vast Vehicle Assembly Building to go to the launch pad in preparation for its final voyage into space next month.

The Atlantis orbiter will close the shuttle programme with a flight in June or just beyond.

The plan then is for US astronauts to be transported to the ISS on Russian Soyuz rockets, perhaps until the middle of the decade.

A number of American companies should be in a position by that stage to sell launch services to Nasa on a range of new vehicles.

Such matters though are secondary on what is surely to be a day of high emotion.

Eileen Collins was the first woman to pilot a shuttle and commanded Discovery in 2005 on the “return to flight” mission after the Columbia accident.

“The shuttle-in-general’s biggest achievement, I believe, was building the International Space Station, which is pretty much 99% complete – and Discovery was part of doing that,” she told BBC News.

“But also Discovery took up the Hubble Space Telescope and also visited the Mir space station, and did many satellite deploys and spacelab missions prior to the space station.

“When you look at the shuttle programme as a whole, we have learned not only to fly space shuttles to low-Earth orbit and re-use them, but we’ve learned about the environment of space and how to make future spacecraft better through the mistakes that were made in the shuttle programme. So overall I think the shuttle was a huge success.”

Endeavour’s scheduled lift-off date is 19 April. It will deliver a flagship scientific experiment to the ISS known as the Alpha Magnetic Spectrometer (AMS).

This seven-tonne instrument will sit on the platform’s truss, or backbone, to conduct a survey of cosmic rays.

Researchers hope this study will reveal new insights into the make-up and origin of the Universe.

Endeavour will be commanded by astronaut Mark Kelly, whose wife, Congresswoman Gaby Giffords, is still recovering from a bullet wound to the head sustained during an assassination attempt in January.