Dynamic testing and simulation of the Mars Exploration Rover

In January of 2004, NASA landed two mobile robotic spacecraft on the surface of Mars as part of the Mars Exploration Rover (MER) project. Named Spirit and Opportunity, each of these rovers is performing their separate scientific missions of exploration more than a year after landing. The Mars Exploration Rovers represent a great advance in planetary rover technology. Part of that advance is represented by the mobility capabilities of these vehicles. At the 1.5 year mark, the two vehicles have traversed more than 10 km over broad plains, craters, rocks, and hills. In order to assess the mobility characteristics of the rovers in the Mars environment, an engineering model vehicle was tested before the mission launches in a representative environment of slopes, rock obstacles, and soft soil. In addition, to gain better insight into the rovers' capabilities, a dynamic model of the rovers was created in the software package ADAMS. The rover model was then used to simulate many of the test cases, which provided a means for model correction and correlation. The results and lessons learned of the test and dynamic simulation of the MER vehicles is provided in this paper. The results from the test and simulation program allowed Spirit and Opportunity to be used in terrain well outside of the original mission requirements. The resulting increase in terrain access, led to substantial additions to the missions science return.