|
Mars is the important goal in the exploration of the solar system. The maximum distance between Mars and earth is over 400 million kilometers, which means 22 minutes are needed for the earth station to transmit the telecommand to the spacecraft on Mars or receive the telemetry from them. Therefore, the real time control of the spacecraft on Mars is such a difficulty for earth station and a total automatic communication network is needed for orbiters and rovers themselves. The international common communication protocol for extraterrestrial planets is CCSDS proximity-1, which is widely used in various Mars probes of the United States, Europe and China. However, the CCSDS proximity-1 always operates between fixed pairs of spacecraft that usually belong to the same mission, which means the callers and the responders between these spacecraft are usually predefined, even when change is allowed, are pre-scheduled. For the possible hailing interferences from the spacecraft of other missions, the traditional method is “random back-off strategy”, which postpones the hailing process randomly when the failure of hailing is detected. The drawbacks are obvious: 1) the valuable communication time is wasted especially when the arc segment time is limited; 2) the random back-off cannot guarantee that the second time or third time will be successful; 3) the more the spacecraft of different missions are, the high the failure possibility is. In this paper, the multi-node efficient anti-interference communication method based on CCSDS protocol for Mars proximity space communication network is presented, which can monitor not only the return link, but also the side lobe of the forward link. Besides, the merging judgment mechanism is implemented in the data service sublayer of the CCSDS architecture, which can adjust the hailing process properly when the collision occurred and no extra time will be wasted. The method will be used in Chinese TW-3 probe. By using the conception products which simulate 5 orbiters and 5 rovers of different missions, real test shows that the presented method performs well in Mars proximity space communication network.
|
