K.U.Leuven > ESAT > PSI > Visics > Research > Topics > Item 1.7

Payload support for planetary exploration (ROBUST)

L. Van Gool, M. Pollefeys, M. Vergauwen

In order to investigate how the cost of planetary exploration missions could be reduced the European Space Agency (ESA) started the PSPE (Payload Support for Planetary Exploration) project. In this project a demonstrator is built that shows that it is feasible to control a micro rover on a planet autonomously. The concept foresees three important parts: a planetary rover, a lander with a stereo camera mounted on a pan-tilt unit and a ground control system. Three important tasks in this project are developed by VISICS: the calibration of the camera system, the reconstruction of the 3D terrain and the visualization of the rover and the lander for simulation and real mission.

Before any measurement of reconstruction can be performed, the cameras on the stereo head need to be calibrated. This means that the relative position and orientation of the two cameras must be computed as well as the pose of the pan and tilt axes of the pan-tilt unit on which the cameras are mounted. Typical calibration procedures use known markers in the scene. This is not possible in this project because the only images that are available are pictures of the (unknown) planetary surface. A new calibration procedure, based on the concept of epipolar geometry, has been developed which makes use of these images only to perform the calibration. The figure below shows two images of the planetary test bed at ESA that were used for calibration with superimposed features and epipolar lines.

Once the calibration has been performed, the same images of the planetary terrain, taken by the cameras on the lander and sent to the ground control system, are used to compute a 3D reconstruction of the terrain. The technique that is applied in this module uses dense matching between pairs of images and computes a Digital Elevation Map as well as textured triangulated meshes. This reconstructed model is shown to scientists who select interesting sites on the terrain. These sites are connected through a path and this path is uploaded to the lander and executed by the planetary rover.

For simulation as well as well during real execution of the commands the motion of the rover on the terrain needs to be visualized on the ground control system. To this end we developed a simulator, which can both compute the interaction between rover and terrain, using a gravitation model, and play back telemetry received from the lander. In the movie robust.mpg we show a simulation of the rover moving on the reconstructed terrain.