Shuttle flight will test safety and get space station back on track.
The main goal of mission STS-114, the first shuttle flight since the Columbia disaster, was always going to be getting seven astronauts into space and returning them safely to Earth. But the astronauts also have a hectic work schedule planned, including delivering supplies to the International Space Station (ISS).
After the planned launch at 19:51 GMT on 13 July, Discovery should reach orbit some eight minutes later. Once established there, the international crew will start a new inspection procedure to check the craft for any damage. The previous shuttle, Columbia, burned up when it re-entered the Earth's atmosphere after a piece of foam fell from the craft during lift-off, punching a hole in the protective panels on its wing. So now the astronauts have been given the tools to inspect for and fix any such damage.
They will attach a new 15-metre boom to Discovery's robotic arm and use this to peer around the craft with infrared and optical cameras. They will also send photographs of the external fuel tank, taken during the launch, back to ground control. And just before Discovery docks with the ISS, Commander Eileen Collins will slowly turn the craft so that the station crew can take a series of high-resolution pictures of its underside, allowing mission controllers to check for any scarring left by impacts.
It is highly unlikely that the shuttle will actually be damaged, so most of this is being done as a precaution - and to prove that the inspection is possible.
Crew members Stephen Robinson and Soichi Noguchi also plan to practise repairing the heat-shield tiles and reinforced carbon plates that protect the shuttle. They'll take a batch of pre-damaged tiles from the cargo and spend half an hour trying to repair the cracks using a gritty glue, foams and polymer sealants.
If Discovery does sustain any damage on its way into orbit, the crew will use the ISS as a safe haven for up to eight weeks until a second shuttle can be dispatched on a rescue mission.
Filling the pantry
Most of the rest of the crew's planned eight days at the ISS will be spent on basic repairs and re-stocking the station. Discovery's cargo bay is stacked with food, water, clothes, spare parts and laboratory equipment. The three-strong ISS crew got their last deliveries from an unmanned craft on 18 June, so these are not emergency supplies. But the fresh delivery will help to fill up the pantry for future construction missions to the ISS.
The astronauts will also do some external work on two of the station's four gyroscopes, which keep the station properly oriented. One has been out of service since February this year after a circuit breaker failed. The other broke in June 2002 and will be completely replaced. With the gyros back in working order, construction can resume on the ISS without throwing it out of orbit.
A few minor improvements will also be made to the station to make construction easier. For example, the astronauts plan to bolt a new equipment rack on the outside of the ISS to hold all the tools and materials needed to add extra modules. The next construction flight, STS-115, is planned for February 2006.
For scientists, the most important part of the mission may be the installation of the Human Research Facility-2 module, containing lab kit that will allow the ISS crew to do more research into how life in space affects astronauts' bodies. The module includes a refrigerated centrifuge to separate fluids and a 'weighing scale' made from a system of springs that can measure an astronaut's mass in zero gravity.
After all the installations, repairs, eating and sleeping, crew members will have just a few hours off-duty during their thirteen days in space. At the end of their tiring stint, they will fill up Discovery's cargo bay with broken parts and waste material for shipping back to Earth. On 25 July they will separate from the ISS and begin the ultimate test of Discovery's safety modifications: flying its crew back home.