Olaf Maibaum

OBC-NG: Towards a reconfigurable on-board computing architecture for spacecraft

The computational demands on spacecraft are rapidly increasing. Current on-board computing components and architectures cannot keep up with the growing requirements. Only a small selection of space-qualified processors and FPGAs are available and current architectures stick with the inflexible cold-redundant structure. The objective of the ongoing project OBC-NG (On-board Computer - Next Generation) is to find new concepts for on-board-computer to fulfill future requirements. The concept presented in this paper is based on a distributed reconfigurable system, consisting of different nodes for processing, management and interface operations. OBC-NG will exploit the high performance of commercial off-the-shelf (COTS) hardware parts. To compensate the shortcomings of COTS parts the OBC-NG redundancy approach differs from the classic way and error mitigation techniques will work mainly on software level. This paper discusses the hardware and software architecture of the system as well as the redundancy and reconfiguration concept. Our ideas will be proven in an OBC-NG prototype, planned for the next year.

A methodology for model-based development and automated verification of software for aerospace systems

Todays software for aerospace systems typically is very complex. This is due to the increasing number of features as well as the high demand for safety, reliability, and quality. This complexity also leads to significant higher software development costs. To handle the software complexity, a structured development process is necessary. Additionally, compliance with relevant standards for quality assurance is a mandatory concern. To assure high software quality, techniques for verification are necessary. Besides traditional techniques like testing, automated verification techniques like model checking become more popular. The latter examine the whole state space and, consequently, result in a full test coverage. Nevertheless, despite the obvious advantages, this technique is rarely yet used for the development of aerospace systems. In this paper, we propose a tool-supported methodology for the development and formal verification of safety-critical software in the aerospace domain. The methodology relies on the V-Model and defines a comprehensive work flow for model-based software development as well as automated verification in compliance to the European standard series ECSS-E-ST-40C. Furthermore, our methodology supports the generation and deployment of code. For tool support we use the tool SCADE Suite (Esterel Technology), an integrated design environment that covers all the requirements for our methodology. The SCADE Suite is well established in avionics and defense, rail transportation, energy and heavy equipment industries. For evaluation purposes, we apply our approach to an up-to-date case study of the TET-1 satellite bus. In particular, the attitude and orbit control software is considered. The behavioral models for the subsystem are developed, formally verified, and optimized.

Robust and Fault Tolerant AOCS of the TET Satellite

The chapter presents the design of the attitude and orbit control system (AOCS) of the small satellite TET-1 (Technology verification career) as an example of a cost effective but still robust and reliable AOCS for small satellites. The AOCS of TET-1 is fully three-axis stabilized. Particular attention is paid to the implementation of robust and fault tolerant design of the AOCS. The redundancy management concept and robust control algorithms are presented. Furthermore the fault detection, isolation and recovery (FDIR) mechanism, which are implemented in various functional levels, are shown. Finally the chapter presents the test strategy for verifying the proposed fault tolerant design.

Robustness as Key to Success for Space Missions

To lead space missions to a success requires a high degree of autonomous intelligence in software and highly reliable hardware. In particular, all software and hardware components should be robust against failures, inexact measurement of data, and, ideally, unforeseen events. This chapter provides an introduction to the demanding conditions in the space environment and describes measures in hardware and software and their testing that are necessary for the development of robust systems for space missions.

Lessons Learned from the Object-Oriented Design of the BIRD Attitude Control System Software

Abstract We give an insight in the software architecture and the object oriented development method of the attitude control system for the Bird microsatellite. Further we show how the unified modelling language is used to described the software design and the developed design patterns