FPGA based On-Board Computer System for the “Flying Laptop” Micro-Satellite

The availability of new high density FPGA technologies enables innovative approaches to the architecture of onboard computer systems (OBCS) for demanding small satellite applications. In the paper, we present the architecture of a highly integrated satellite computer exploiting the powerful features of Xilinx’s Virtex-II Pro FPGA technology. The computing resources of the “Flying Laptop” satellite are provided by a single OBCS performing the control functions of a traditional satellite bus controller (SBC) as well as all tasks of the payload data handling and processing system (PDH). The unification of the different computing functions on board the satellite onto a single but highly redundant computer system results in clear-cut system structure and provides a high degree of fault tolerance with minimal resource requirements. The “Flying Laptop” micro satellite is under development at the Institute of Space Systems at the Universität Stuttgart. The primary mission objective is to demonstrate and qualify new small-satellite technologies for the future projects. In addition, the three main scientific payloads of the satellite will allow performing a number of ambitious earth observation experiments. According to the primary mission objectives, the OBCS itself will be a subject for evaluations of its innovative concepts and for qualification of its underlying hardware. 1 THE “FLYING LAPTOP” MICRO-SATELLITE The total mass of the cubical satellite body with 60 cm edge length will be around 100 kg. The power supply system is based on three solar panels two of which are deployable. The triple-junction solar cells have an efficiency of approx. 26%. The peak power consumption of the satellite will be about 300 W which will be delivered by a battery pack consisting of 8 Lithium ion cells. The attitude control system is designed to achieve a pointing accuracy of better than 2.5 arc seconds. In addition, the planned scientific experiments require a very high manoeuvrability which both are challenging requirements for a micro-satellite. The “Flying Laptop” satellite is three-axis stabilized by momentum wheels, which can be de-saturated using magnetic coils. The attitude motion is monitored by five different types of sensors: a 3-axis magnetometer, a coarse sun sensor system, four fibre optical rate sensors, a star tracker unit with two camera heads and a navigation system consisting of three GPS receivers.