Abstract:  In order to meet the demand of transmitting down the key telemetry parameters and transmitting up the remote control command in the period of satellite orbit entry，a launch vehicle space-based TT & C relay system during satellite orbit entry was designed.The scheme was mainly based on rocket ready-made space-based TT & C terminal and satellite ready-made TT & C equipment.The composition，working principle and workflow of the relay system were introduced，the beam pointing algorithm for spacebased TT & C phased array antenna was studied，and a kind of ground test system for satellite telemetry relay and remote control communication function was designed.The relay system completed two flight tests in KZ-1A flying commission，the relay forward data of satellite was intact，and the carrier to noise ratio of the satellite communication terminal were all greater than 20dB.The bit signaltonoise ratio of space-based telemetry return signal received by ground TT&C center had more than 3dB margins to the receiving threshold.The test shows that the relay system has sufficient communication link margin and reliable operation，which can save more than half of the cost compared with the support of ground TT & C resources or the use of space-based TT & C by the satellite itself.

Key words: satellite into orbit, launch vehicle, space-based TT &, C, relay system, flight test