Mars Exploration Rover A, B (MER A, B / Spirit / Opportunity)

MER A (Cruise configuration) [NASA]

MER A (Lander) [NASA]

The MER (Mars Exploration Rover) mission will consist of two identical rovers, which will be large (~130 kg) vehicles based on the Athena Rover design that was originally considered for the Mars 2001 Lander mission. The Cruise configuration is based on the Mars Pathfinder spacecraft. The rovers will be landed using an airbag system similar to that used on Mars Pathfinder but without the stationary lander. The first landing is scheduled to take place on 4 January 2004 and the second 18 days later on 25 January. The two landing sites were chosen: Gusev Crater and Meridani Planum. The mission should last for at least 90 days each, until late April. The rovers are designed to cover roughly 100 meters each Martian day, or sol (approximately 24 hours, 37 minutes). They carry a scientific packages which includes:

• a panoramic camera (Pancam),
• a rock abrasion tool (RAT) to expose fresh surfaces of rock,
• a miniature thermal infrared spectrometer (MiniTES),
• a microscopic camera,
• a Mössbauer spectrometer, and
• an alpha-proton-X-ray spectrometer (APXS).

The MER-A probe features the MER-2 rover, while MER-B flies with the MER-1 rover. MER A and B have been named Spirit and Opportunity respectively. The names were selected from a naming contest.

MER-A landed on January 4th 2004 in Gusev Crater. A few days later, the rover Spirit left the landing unit. On January 21st the Spirit rover entered save mode and stopped sending data. NASA resolved the software problem and Spirit resumed work.

MER B with the rover Opportunity landed on Mars in Meridani Planum on January 25th 2004.

Both rovers are still operational, more than twice the originally planned lifetime.