Term Analysis of a TDRS Tracking a User Satellite

The space-based TTC network is a trend to be developed. The coverage of a TDRS tracking a user satellite is the first consideration for designers and depends on different elements. From the view point of engineering application, the terms of a TDRS tracking a user satellite are analyzed here in detail. Based on their orbital characteristics, the algorithm of a TDRS tracking user satellites without the earth blocking, which will diminish the coverage, is presented. Then the terms to decide whether the earth blocking happens are divided into three cases to be discussed in detail. The ways to accurately predicate the occurrence of earth block and sun interference are given here too. Despite of the two satellites being in line of sight, the position of the antenna fixed onboard a user satellite will cause exclusion sometimes. But, with the appropriate mast's length, it is sure for a TDRS to track the use satellite without any block when they are in line of sight. Therefore, the presented formulas and conclusions, which are verified by simulation means, are suitable for all cases. They can be used as means to determinate the number of TDRS to construct a space TTC network and strategies to allocate the resource of an on-orbit TDRS to user satellites. It can improve the TTC coverage for a TDRS tracking user satellites.