Analysis of Manned Spacecraft Attitude Variation to Relay Terminal Antenna Pointing Error

With the application field expanding of the data relay satellite in modern space technology, manned spacecraft will install the relay terminal and realize the high speed data transmission from spacecraft to control center by use of data relay satellites system. However, there are many factors such as the spacecraft regular orbit maneuver, astronauts intravehicular activity, extravehicular walk and so on, which will cause the spaceship attitude variation. As we all known, in order to obtain a higher speed data transmission rate, the relay terminal gradually adopts Ka band. The Ka band beam angel is smaller than C, S band. If the spacecraft attitude change amplitude exceeds a certain range, the attitude variation will affect the spacecraft relay terminal antenna accurate pointing to data relay satellites, which leads to inter satellite relay link lose lock or BER (bit error rate) increasing and affects the data transmission quality. Based on the detailed analysis of the coupling between the spacecraft attitude and the relay terminal antenna pointing relations, in this paper, by using of mathematical error analysis method, the accurate pointing error model is established for spacecraft attitude errors on the relay terminal of antenna, and the correctness of the model is verified by simulation. The error model has a strong practical value to accurately and reliably establish the data transmitting link between spacecraft relay terminal and relay satellite.