The Sojourner is one of the two key pieces of equipment used in the July 1997 Mars Landing of the Mars Pathfinder project.
Sojourner is the 6-wheeled rover that is carried inside the larger Mars Pathfinder Lander that is used for exploration once the lander has touched down on the Red Planet. Sojourner's full name is The Microrover Flight Experiment (or MFEX), though the name 'Sojourner' was the result of a year-long essay contest to find a more "PR Friendly" designation.
The name chosen was submitted my 12-year-old Valerie Ambroise of Bridgeport, CT, in her essay about Civil War-era American Heroine Sojourner Truth. By no coincidence, the name Sojourner also mean, in a dictionary sense, "traveler".
The design of the MFEX rover is a prime example of NASA's current "Build it fast, build it cheap" design philosophy. The basic design is a 6-wheel vehicle of a rocker bogie design which allows the traversing of obstacles of up to 13cm in size. Each wheel is independently powered, geared, steered and actuated to give the best climbing ability possible. All told, the vehicle has a top speed of 0.4m/min.
The rover is electrically powered (obviously), with it's prime source of power being it's top-mounted solar collector panel composed of 234 5.5mil GaAs solar cells. A secondary set of 9 D-Sized LiSOCL2 batteries provide supplemental power of 150WHrs. Maximum power available, during mid-day, is 30 Watts, though average power usage is 10 watts.
The control electronics are based on an 80c85 processor with 176Kbytes of PROM and 576Kbytes of RAM (yes, I'm serious). The system provides motor control and interfacing with some 70 sensor systems. Some of the electronics components are not designed for survival in the sub-zero night temperatures (reaching -110 Degrees Celsius) are kept in a WEB, or Warm Electronics Box, that maintains a slightly higher ambient temperature for certain components.
During movement, the rovers' "vision" is supplied by a Laser Striping and Camera System to determine the lay of the land immediately in the path of the rover. The vehicle can then steer itself automatically to avoid these obstacles. The microrover communicates with the Lander via a UHF modem link which, in turn, coresponds with mission control.
Among the more interesting features of the rover is its stereo camera system which takes side-by-side pictures in order to approximate depth perception and use calculation based on that to designate the rovers' next waypoint.
The Sojourner Microrover operated for over 3 times it's projected 7-day life span, and eventually failed due to a combination of temperature extremes and bombardment from damaging radiation. | 
