Components of the flight hardware for Mars Exploration Rover-1 are in the Payload Hazardous Servicing Facility. At left is the rover. In the center is the cruise stage, which includes elements such as the thruster clusters, launch vehicle adapter and cruise electronics module. Each rover , aeroshell and lander will undergo a full mission simulation while at KSC. All flight elements will then be integrated. After spin balance testing, each spacecraft will be mated to a solid propellant upper stage booster that will propel it out of Earth orbit. The rovers will serve as robotic geologists to seek answers about the evolution of Mars, particularly for a history of water. The rovers will be identical to each other, but will land at different regions of Mars. Launch of the MER-1 is scheduled for May 30. MER-2 will follow June 25.