This work covers two programs that accomplish the same goal: creation of a “reachability map” from stereo imagery that tells where operators of a robotic arm can reach or touch the surface, and with which instruments. The programs are “marsreach” (for MER) and “phxreach.” These programs make use of the planetary image geometry (PIG) library. However, unlike the other programs, they are not multi-mission. Because of the complexity of arm kinematics, the programs are specific to each mission.
In each case, the input consists of XYZ and surface normal data. The output is a multiband image, co-registered to the input image. Each band represents a predefined combination of arm instrument and arm configuration (e.g., elbow up, elbow down), and the value indicates whether or not the instrument can observe (see or touch) the surface at the corresponding pixel.
This software models the arm precisely, using the same algorithms as the flight software. It is thus uniquely suited to determining reachability and safety of robot arm operations. The MER RAT instrument provides additional information beyond just a flag — it supplies a “preload” value, which indicates how much force the arm can apply at that spot. The MER reachability program considers collisions of the arm with terrain in determining reachability; the PHX program does not.
These programs provide this reachability information in an easy-to-use format by combining the surface position and orientation, arm kinematics, instrument mounting, and instrument approach angles. This software is also integrated into the ground data system and the automated processing pipelines. It understands the EDR and RDR file formats and metadata, and products tailored for in situ surface operations.
This work was done by Robert G. Deen,
Patrick C. Leger, Matthew L. Robinson, and
Robert G. Bonitz of Caltech for NASA’s Jet
Propulsion Laboratory. For more information,