In the Payload Hazardous Servicing Facility, both Mars Exploration Rovers (MER) can be seen, MER-1 in the foreground and MER-2 in the background. Workers are preparing the shrouded MER-2 for mating to the lander. Set to launch in Spring 2003, the MER Mission consists of two identical rovers, landing at different regions of Mars, designed to cover roughly 110 yards each Martian day over various terrain. Each rover will carry five scientific instruments that will allow it to search for evidence of liquid water that may have been present in the planet's past. The first rover has a launch window opening May 30, and the second rover a window opening June 25.