Mars Pathfinder (MPF, Discovery 1)

Mars Pathfinder (Cruise configuration) [NASA]

Mars Pathfinder (Lander) with rover [NASA]

The MPF (Mars Pathfinder) (formerly known as the Mars Environmental Survey, or MESUR Pathfinder) is the second of NASA's low-cost planetary Discovery missions. The mission consists of a stationary lander and a surface rover. The mission has the primary objective of demonstrating the feasibility of low-cost landings on and exploration of the Martian surface. This objective will be met by tests of communications between the rover and lander, and the lander and Earth, and tests of the imaging devices and sensors.

The scientific objectives include atmospheric entry science, long-range and close-up surface imaging, with the general objective being to characterize the Martian environment for further exploration. The spacecraft entered the Martian atmosphere without going into orbit around the planet and landed on Mars with the aid of parachutes, rockets and airbags, taking atmospheric measurements on the way down. Prior to landing, the spacecraft was enclosed by three triangular solar panels (petals), which unfolded onto the ground after touchdown. The lander and rover operated until communication was lost for unknown reasons on 27 September.

The rover "Sojourner" is a six-wheeled vehicle which is controlled by an Earth-based operator, who uses images obtained by both the rover and lander systems. Note that the time delay is about 10 minutes, requiring some autonomous control by the rover. The primary objectives were scheduled for the first seven sols (1 sol = 1 Martian day = ~24.7 hours), all within about 10 meters of the lander. The extended mission included more analyses of nearby rock and soil and more tests of the rover capabilities.

Mars Pathfinder impacted the surface on July 4 at 16:57 UT (12:57 PM EDT) at a velocity of about 18 m/s (40 mph) - approximately 12.5 m/s vertical and 12.5 m/s horizontal - and bounced about 15 meters (50 feet) into the air, bouncing another 15 times and rolling before coming to rest approximately 2.5 minutes after impact and about 1 km from the initial impact site. The landing site in the Ares Vallis region is at 19.33 N, 33.55 W and has been named the Sagan Memorial Station.