A worker checks a component of the Mars Exploration Rover 2 before flight stow of the solar panels extended.

A worker checks a component of the Mars Exploration Rover 2 (MER-2) before flight stow of the solar panels, still extended. Set to launch in Spring 2003, the MER Mission will consist of two identical rovers designed to cover roughly 110 yards each Martian day over various terrain. The rovers will be identical to each other, but will land at different regions of Mars. 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.