At 19:15 Greenwich Mean Time on June 2, 2003, after one Earth orbit, the space probe Mars Express separated from the final stage of the giant Soyuz-Fregat rocket launcher that had blasted off from the Baikonur Space Center in Kazakhstan. Europe\u2019s mission to Mars was under way.The launch was faultless, and the Mars Express orbiter, along with the Beagle 2 lander, are due to reach Martian orbit on Dec. 25, 2003. Part of the credit goes to an obsessive focus on simulating what could go wrong, says simulations officer Zeina Mounzer. "As we get closer to launch, the simulations become increasingly unlikely but have a bigger impact on the mission\u2019s success," says Mounzer, who shows her colleagues the movie Apollo 13, in which NASA engineers work to save the crew of a disabled orbiter.Mounzer and eight of the Mars Express mission engineers are employed by Vega Informations-Technologien, a Darmstadt, Germany-based company that has worked on various European space programs since 1978. Over time, Vega\u2019s simulation work has grown faster than its mission control work, says company director John Lewis.Lewis says the agency\u2019s early simulations in the mid-1980s were crude, but today\u2019s take place in the very control room that will be used for the mission. Consoles send commands not to the real spacecraft but to a software simulation of it constructed by Vega, running the real mission software code. Routinely, he explains, the simulations detect software glitches that went undetected by the spacecraft\u2019s manufacturer.Europe, Lewis adds, simulates missions to a much greater extent than does NASA. Indeed, an official NASA inquiry into the failure of the U.S.\u2019s Mars Climate Orbiter mission, which burned in the Mars atmosphere in 1999, concluded that the mission\u2019s navigation team lacked training needed to detect an engineering mistake that delivered navigation data in English units rather than in metric units.