The Central on-Board Computer of the Philae Lander in the Context of the Rosetta Space Mission

Abstract

The Rosetta-Philae space mission is an unprecedented venture. After a ten-year journey across the Solar System and many complicated manoeuvres, the Rosetta spacecraft smoothly approached a small (2-4 km in diameter) celestial body, comet CG/67P. Furthermore, the spacecraft executed additional fine manoeuvres to fly a multitude of low and high altitude orbits around the comet, mapping its shape and surface in detail never seen before, and has continued to observe it for a year since then. The Rosetta spacecraft is equipped with scientific instruments that deliver a wealth of new knowledge about the CG/67P comet, in addition to spectacular pictures. Delivering the Philae lander onto the surface of the comet 500 million km away from Earth was also a remarkable technological success. The direct measurements made by the Philae lander on the surface of the comet provided significant new knowledge. The first half of this paper gives a brief overview of the objectives and highlights of the Rosetta-Philae mission. In the second half the major hardware and software design aspects, including the conceptual design and implementation of the central on-board computer (CDMS) of the Philae lander are outlined. It focuses on the implementation of fault tolerance, autonomous operation and operational flexibility by means of specific linked data structures and code execution mechanisms that can be interpreted as a kind of object oriented model for mission sequencing.