Free-space satellite optical communication: adaptive information bandwidth to maintain constant bit error rate during periods of high satellite vibration amplitudes

Abstract

Satellites in free space suffer from periods of high displacement amplitude vibrations (for example: during the operation of the thruster, the antenna pointing mechanism, or the solar array drive mechanism). In order to utilize the advantages of optical communication in space, very narrow divergence transmitted beams are used. The high amplitude vibrations of the satellite cause decrease of received signal power in the receiver satellite due to mispointing of the transmitted beam. One way to overcome this problem is to develop very complicated stabilization systems. The disadvantages of this solution are: complexity, reliability, and cost. Most of the time, the amplitude of the vibrations is low and does not affect the communication performance. Considering these facts, we derive a model of a communication system that adapts the communication system parameters to changes in received signal caused by changes in vibration amplitude. The purpose of this model is to keep the bit error rate (BER) low and constant by adapting the system bandwidth and the receiver parameters to the vibration amplitude. The duration amplitude and occurrence of the high amplitude vibrations are assumed to be known so the adaptation of the communication system parameters is simple. The adaptive model is derived for the on off keying (OOK) modulation method. An example for practical optical space communication systems based on the adaptive model is given. Comparison and analysis of the performance of standard and adaptive models of communication systems for variable amplitudes of vibration amplitude are presented.