In the Payload Hazardous Servicing Facility, workers prepare the Mars Exploration Rover (MER) aeroshell for transfer to a rotation stand. Set to launch in 2003, the MER Mission will consist of two identical rovers designed to cover roughly 110 yards (100 meters) each Martian day. 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 rovers will be identical to each other, but will land at different regions of Mars. The first rover has a launch window opening May 30, and the second rover a window opening June 25, 2003.