JUNE 2006 IEEE Robotics & Automation Magazine 27 1070-9932/06/$20.00©2006 IEEE T he Mars Exploration Rover (MER) vehicles, Spirit and Opportunity, carry a unique in situ instrument suite that has been designed to measure and under- stand the detailed geochemistry and morphology of the surface of Mars [1]. The in situ instrument suite includes the Mössbauer spectrometer (MB) [2], the alpha particle X-ray spectrometer (APXS) [3], the microscopic imager (MI) [4], and the rock abrasion tool (RAT) [5]. The deployment and placement of these instruments onto the Martian sur- face (both soil and rock targets) is controlled by the five-degree-of- freedom (5-DOF) instrument deployment device (IDD). The IDD represents the most dex- terous robotic manipulator ever flown to another lunar or plane- tary surface. Note that an extended version of this article is presented in [6], and additional details concerning the surface opera- tions of the IDD is presented in [7]. The IDD is mounted on the front end of the rover and is capable of reaching out approximately 0.8 m in front of the rover at full extent. The IDD weighs nearly 4 kg and carries a 2-kg payload mass (instruments and associated structure). During rover dri- ving activities, the IDD is contained within a stowed volume that does not impact the rover’s ability to traverse safely across the Martian terrain. Targeting for the placement of the in situ instruments on rock and soil targets is carried out using the front hazard avoidance cameras (or front Hazcams), which are configured as a stereo camera pair. Onboard software controls the IDD based on sequences developed by ground operators. The onboard software con- tains numerous low-level and high-level functions for control- ling the IDD such as actuator current limiting based on temperature and pose, inverse kinematic Cartesian control, deflection compensation due to gravity and tilt- induced droop, model-based preloading of instruments on hard targets, and instru- ment placement using proximity feed- back sensors. For the MER Project, the entire scope of work associated with the design, development, test, and operation of the IDD and in situ instruments was grouped into a subsystem known as the instrument posi- tioning system (IPS). As with many of the other rover subsys- tems, the IPS was a collaborative effort between scientists, engi- neers, and instrument developers that culminated in the successful operation of this dexterous robot arm for collecting important science data, including data that point to a significant water history at the two landing sites, Gusev Crater [8] and Meridiani Planum [9]. The following section describes the system requirements that drove the design of the overall IPS. In the “Algorithms and Software” section, this article summarizes the flight soft- ware functions and algorithms utilized to command and con- trol the IDD in order to perform autonomous surface operations. The IPS test program is described in the “System Calibration” section, including results from subsystem BY ERIC T. BAUMGARTNER, ROBERT G. BONITZ, JOSEPH P. MELKO, LORI R. SHIRAISHI, P. CHRISTOPHER LEGER, AND ASHITEY TREBI-OLLENNU Mobile Manipulation for the Mars Exploration Rover A Dexterous and Robust Instrument Positioning System MARS IMAGES: NASA/JPL/CORNELL /USGS, BINOCULAR IMAGE © PHOTODISC, INC.