The Mars Express is a spacecraft that has been in orbit around Mars since 2004. Yesterday it conducted a fly-by of the Phobos, the larger of the two moons of Mars. As it passed by the moon, the gravity of the moon deflected the orbit of the Mars Express. From this deflection, scientists can calculate the mass of the moon. The Mars Express Blog has published the flight dynamics of the flyby so that anyone can visualize it with Celestia. Celestia is a free space simulation software that is available on Mac OS X, Linux, and Windows. Celestia enables you to explore the solar system, or even the universe, in three dimensions.
via : Mars Express Blog
