Software Platform of the DLR Compact Satellite Series

Abstract

The German Aerospace Center (DLR) has opted for the development of the DLR Compact Satellite, to be able to promote a freely accessible, space based platform to carry out research and development activities. The term compact satellite refers to a satellite, limited to an envelope of approximately 1 cubic meter and a mass maximum of approximately 200 kg, which means the compact satellite is ranked at the lower end of the mini satellite class. For the first mission detailed design of the on-board computer (OBC) will be only available from development phase C on. As the procurement of hardware (H/W) components also depends on the availability of this design, the first breadboard H/W will be available even later in the project. Due to these project constraints, embedded software (S/W) development for the space segment Command and Data Handling (C&DH) subsystem is faced with three major challenges: (1) start the S/W design and implementation as early as possible against unknown H/W components, (2) design the S/W in a way that it is most independent from the underlying – and yet unknown – H/W and real-time operating system (RTOS), and (3) make the S/W portable to be prepared for future compact satellite missions. Within this paper we provide a brief overview of our approaches to face these challenges. They consist of several S/W development techniques, which mainly concentrate on the S/W design against the unknown H/W environment on the one hand, and on the other hand on the development of a flexible, robust and re-usable S/W platform. The core elements of this platform are composed of a H/W abstraction layer, an operating system layer, a middleware layer, and essential services like a CCSDS/PUS S/W stack. The platform is completed by a powerful logging framework, which enhances the traditional housekeeping capabilities and offers extensive filtering and debugging techniques for monitoring and Fault Detection, Isolation & Recovery (FDIR) needs.