In early August, the Mars Pathfinder Microrover Flight Experiment (MFEX or "Sojourner") completed its final set of system tests with the Mars Pathfinder lander. This has been an exciting time for the MFEX team. Many of the design features and operation plans have been verified by the conduct of these tests. For the first time Sojourner was imaged by the lander camera, or IMP (Imager for Mars Pathfinder), and that image was displayed at the rover control workstation for use in planning traverses. During these tests Sojourner was released from the rover petal (one of the four petals making up the lander) and commanded to drive down a ramp to reach flooring (simulating the Martian surface) for traverse. In several tests of its navigation system, Sojourner drove in front of the lander, avoiding obstacles as it went, and reached its destination - a goal location some 3 m away from the edge of the exit ramp. Along the way, Sojourner excited technicians in the test area by driving near portions of the lander. Each time, the vehicle recognized the lander as an obstacle and turned away, while still heading for the destination. Sojourner decided, based on the onboard navigation measurements (distance traveled and heading), that it had reached its destination. Once it reached its destination, it stopped and reported that it had completed the traverse. Its position was measured and found to be no more than 20 cm from its commanded target.
Elements of these final tests repeated earlier tests conducted at Mars-environment temperatures. In addition, during these tests, Sojourner performed experiments with its science instrument, the alpha, proton, x-ray spectrometer (APXS); imaged from its cameras' locations in the test chambers; and conducted portions of the material adherence, wheel abrasion, and soil mechanics experiments. During this time, Sojourner also routinely reached a safe state regardless of the inadvertent command errors issued by the MFEX team, in training for operations on the surface of Mars.
Once these tests were completed, the MFEX team prepared Sojourner for shipment to the Cape. On August 23, 1996, Sojourner was air shipped from Los Angeles to Orlando and transported later that day to the Kennedy Space Center. There it met the Mars Pathfinder lander in the Spacecraft Assembly and Encapsulation Facility 2 (SAEF2) for final integration in preparation for launch. By September 6, 1996, Sojourner had successfully completed a series of functional tests: extensive health checks (i.e., all actuators and sensors tested), a functional test with the APXS, and a communication test with an initial configuration of the lander (undergoing reassembly at the Cape after transport). Following these tests, Sojourner was stowed along with its exit ramps on the rover petal. All components were tied down in preparation for petal attachment to the lander and petal closing later this month. Additional communication checks are planned with the lander prior to petal closing as the lander completes its reassembly later this month.
Manager, Microrover Development
For further information on the Rover, go to the Rover Home Page!
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