In the Payload Hazardous Servicing Facility elements of one of the Mars Exploration Rovers come together.

In the Payload Hazardous Servicing Facility, elements of one of the Mars Exploration Rovers (MER) come together. In the foreground is a lander. In the background are an aeroshell, with the heat shield on top, and cruise stage below. The two rovers, MER-1 and MER-2 , aeroshells and landers 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.