One of the Mars Exploration Rovers MER) sits on a stand in the Payload Hazardous Servicing Facility.

One of the Mars Exploration Rovers (MER) sits on a stand in the Payload Hazardous Servicing Facility. Processing of the rovers, cruise stage, lander and heat shield elements is ongoing. Set to launch in 2003, the MER Mission will consist of two identical rovers designed to cover roughly 110 yards 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.