Communication platform for inter-satellite links in distributed satellite systems

• Main Author: Paul, Jean R.
• Published: University of Surrey 2011
• Subjects: 621.382
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.543927

A Distributed Satellite System (DSS) for space weather monitoring, in which satellites are able to exchange data via Inter-Satellite Links (lSL) and a master node communicates with ground is the target of this research. As design of satellite systems is dictated by economical and engineering factors, the use of readily available commercial wireless terrestrial network technologies for ISLs is an attractive prospect in distributed satellite systems. This work addresses the application of wireless terrestrial networking standards to DSS operating in Low Earth Orbits (LEO), which are affected by orbital dynamics. All communication factors such as range, antenna gain, velocity, etc. vary with time, and as a result adaptive on-board data processing and transmission techniques are necessary to provide system responsiveness to orbital effects. A novel analysis of the impact of satellite attitude on the antenna loss is carried out and the minimum beam width that ensures ISL is determined. A high performance System-On-Chip (SoC) computing platform capable of supporting the adaptive MAC method has been simulated, and then implemented on hardware. The SoC design features a IEEE802.11 wireless transceiver core developed to support ISL, which is controlled by a software application running on the LEON3 32-bit RISC processor. The SOC is implemented on an FPGA for dynamic reconfigurability purposes, and the wireless transceiver is designed with the aim of extending the communication range of traditional wireless networks to hundreds of kilometres. The range determination mechanism can be hard-coded or defined in software. The Space Wire protocol, which is becoming the de facto standard for on-board spacecraft networks, is not yet defined for wireless communications. A bridge is proposed allowing fault-tolerant intra-spacecraft Space Wire networks to communicate via inter-satellite links. An analysis of the hardware requirements is presented for medium date rate systems. This reveals that the IEEE802.11 transceiver, implemented as a hardware accelerator, has the capability to support the full range of data rate provided by SpaceWire links, and adds extra robustness to SpaceWire networks.