Constraints Analysis and Optimization Design of TT&C Down-Link for Spacecraft

After spacecraft is launched into orbit, TT&C link serves as the only channel for control data exchange, which is the lifeline for spacecraft operation. With the increasing hard constraints on cost, spectrum, quality, volume, energy, time limits, and other factors, TT&C link margin tension caused by the increase in spacecraft information rate, attitude changes, and high orbit operations needs to be relieved. Main factors affecting TT&C links are identified and analyzed in this paper, and start from aspects of antenna gain, polarization loss, subcarrier modulation, information rate and coding gain, optimization design methods are proposed by not changing the orbital characteristics, transmitted power of the transponder or relay terminal. Theoretical analysis and comparative calculation results show that proposed method can improve link margin by more than 10 dB, which can be applied to the design and optimization of spacecraft TT&C links.