Small Mobile Ground Terminal Design for a Microsatellite Data Collection System

Abstract

Many developing countries with the help of developed ones have gained space technologies experience by building and launching microsatellites which involve affordable costs. Apart from technology transfer, different applications could be achieved using a LEO (low earth orbit) microsatellite over large areas where other communication systems are lacking. The use of a single LEO microsatellite for data collection implies a complex hardware and software architectures of the ground terminals especially when they are designed to be small, lightweight and economical. The ground terminal proposed in this paper is a small, assembled device that incorporates a microcontroller, RAM, Flash memory, Real Time Clock, OEM GPS board, AFSK modem, backup lithium battery, and a transceiver. Its built-in software handles all functions involved in collecting, packaging, and transmitting the various data to the microsatellite. A satellite visibility calculation algorithm, developed in assembly language, makes the terminal intelligent without the need of a PC which makes other available commercial terminals heavy and difficult to carry. The small terminal can be mounted on any mobile or fixed platform to accomplish missions such as data collection from remote sites or mobile automatic position reporting. The connected sensors or GPS are sampled at regular time intervals and data stored in memory. Once the satellite comes into range, the gathered data is packetized and transmitted. The terminal can even be connected to any text editing device for messaging. This paper describes the hardware and software solutions achieved to develop a small, very low cost and automatic ground terminal for use with a single microsatellite data collection system.