As the clock ticks on the soon-to-be-retired space shuttle, the president has kept alive the hopes of scientists who want to install a device that would be used for one more experiment on the International Space Station.

First, an update on the space shuttle. The shuttle, which first orbited the Earth in 1981, is slated for retirement in 2010. The Bush administration in 2004 decided to wind down the program so that funding allocated to the shuttle could be redirected to building its successor. As a result, NASA had to cut the number of shuttle flights assigned to assembling and supporting the International Space Station. Originally, the shuttle had been expected to operate throughout the lifetime of the ISS. Under the new Bush policy, all flights were to be completed by the end of fiscal year 2010, specifically Sept. 30, 2010.

Cutting the flights meant limiting the amount of equipment that could be taken to the ISS. One device NASA initially determined it could not carry was an instrument called the Alpha Magenetic Spectrometer, or AMS.  It is a particle-physics experiment "designed to examine fundamental issues about matter and the origin and structure of the universe." An international consortium — not NASA — built it, so the prospect of it not getting to the space station meant breaking an international commitment and wasting $1.5 billion spent so far on the project. Because the designers fabricated the equipment specifically to fit in the shuttle's cargo bay, it would not be easy to carry it to space any other way.

AMS advocates lobbied the space agency to add a shuttle launch. Their argument convinced Congress. In the 2008 NASA Authorization Act, lawmakers directed that NASA launch AMS. Bush signed the bill into law on Oct. 15, 2008, and NASA added the flight to its launch schedule.

Once in office, Obama did two things. First, with passage of the fiscal 2010 budget resolution on April 29, 2009, he presided over the removal of the Sept. 30, 2010, cutoff date for the shuttle program, giving NASA the scheduling flexibility to complete the remaining flights without excessive time pressure. Second, on May 7, 2009, Obama requested funds for the AMS mission in his fiscal year 2010 NASA budget. The mission is scheduled to launch in mid to late 2010, although it is widely expected that some shuttle launches will slip into the first half of fiscal year 2011.

Such slippage poses a potential hangup. Obama did not include any funds for the shuttle in his projected budget for fiscal year 2011. Should any of the flights be delayed, the president would need to provide that funding in the proper fiscal year in order to keep his promise. For now, that's a hypothetical.

But Obama has done what he said he would do — supported the launch and provided money for it. On Aug. 11, 2009, NASA moved the ball forward by naming the crew for the mission. We consider this a Promise Kept.