The first of two Mars Exploration Rovers, MER-A, is targeted for launch no earlier than Sunday, June 8 at 2:05:55 p.m. EDT. Liftoff will occur aboard a Boeing Delta II launch vehicle from Pad A at Space Launch Complex 17 on Cape Canaveral Air Force Station. A second launch opportunity exists at 2:44:07 p.m. EDT, if necessary.

Should launch be delayed by 24 hours, the two launch times available are 2:02:23 p.m. and 2:40:30 p.m. EDT. The planetary launch period window extends through June 19. The second of the two rovers, MER-B, is scheduled to launch June 25.

MER-A will reach Mars on Jan. 4, 2004, and MER-B on Jan. 25. The two MER missions seek to determine the history of climate and water at two sites on Mars where conditions may once have been favorable to life. Both rovers are identical.

Each rover carries five scientific instruments including a panoramic camera and microscope, plus a rock abrasion tool that will grind away the outer surfaces of rocks to expose their interiors for examination. The rovers each weigh approximately 400 pounds. They will navigate themselves around obstacles as they drive across the Martian surface, traveling up to about 130 feet each Martian day. Each rover's prime mission is planned to last three months on Mars.

FMI: http://mars.jpl.nasa.gov/mer