Conquering the Cold: Thermal Testing of MMX Rover IDEFIX's Locomotion Subsystem for the Exploration on Phobos

Abstract

The Martian Moon eXploration (MMX) mission, led by the Japan Aerospace Exploration Agency (JAXA), is scheduled for launch in 2024 with the objective of sample-return from the Martian Moon Phobos and additional scientific observations of Deimos. As part of this mission, the MMX rover 'IDEFIX', developed collaboratively by the French Centre National d'Études Spatiales (CNES) and the German Aerospace Center (DLR), will serve as a mobile scout on the surface of Phobos. With its four-wheeled design and a weight of 25 kg, the rover will operate in microgravity and conducting in-situ measurements in areas of scientific interest. The locomotion subsystem (LSS) of the MMX rover, developed, build and qualified by DLR's Robotics and Mechatronics Center, plays a key role in fulfilling the mission objectives. The LSS is designed to accomplish various high-level requirements, including the correct reorientation (so-called uprighting) of the rover after ballistic landing, precise alignment of the solar cells for optimal power generation, and the provision of different driving modes to explore Phobos and interact with its surface. Additionally, the LSS allows for adjusting the rover's ground distance to allow measurements with the Raman spectrometer. To ensure the LSS can withstand the challenging conditions of the MMX mission, particularly the harsh environment during the cruise phase and the expected extremely low temperatures on Phobos, a comprehensive thermal design was developed. The LSS was subsequently subjected to rigorous testing throughout the development phases. The testing involved evaluating the mechanical, electrical and thermal aspects of various subunits, including the complex hold-down and release mechanism (HDRM), as well as conducting full functionality tests of the flight representative LSS during the qualification and acceptance stages. This presentation provides an overview of DLR's approach to thermal testing activities for the LSS during the development phase of the MMX rover. It offers insights into the MMX mission as a whole and presents a detailed examination of the qualification and acceptance thermal tests conducted for the LSS, emphasizing the significance of these tests in ensuring the successful operation of the rover during the mission.