LOCO - Software for the MMX Rover Locomotion System

In situ exploration of the surface of celestial bodies requires hardware purposely developed for the target environment and sophisticated software architectures for efficient operation. So does the Martian Moons Exploration (MMX) rover IDEFIX, which is developed by the French Centre National d'Études Spatiales (CNES) and the German Aerospace Center (DLR) to explore the surface of the Martian moon Phobos. It is equipped with a locomotion system responsible for the movements.The software for the rover locomotion system (LOCO-SW) translates system-level commands into actions executed by the locomotion system while monitoring the status of its mechanical and electrical components. To do so, it takes care of the following tasks: Reception of telecommands, sending of housekeeping telemetry, timing, inter-subsystem communication and signaling, processing of telecommands, SpaceWire communication with the LOCO electronic box for actuator control and monitoring of the sensor data. Few functionalities can rest upon existing frameworks, though many features have to be designed particularly for IDEFIX. The paper will present how they are defined and realized while various quality goals are fulfilled. Comprehensive testing is conducted to ensure the reliability and effectiveness of the software architecture. The test suite comprises unit tests and regression testing on hardware similar to flight hardware, as well as tests in simulation. These tests validate the functionality and performance of the software architecture and show its suitability for the MMX locomotion system. This paper focuses on the architecture, design and testing of the LOCO-SW. The design of the software will be presented, and the decisions will be linked back to the requirements and use cases that motivate the design.