Abstract: Autonomous sample-return lunar probe has made successful achievements on unmanned and autonomous sampling and return mission from far-side of the Moon for the first time of humankind, under the support of lunar relay satellite. To ensure the probe and relay satellite can smoothly and stably establish a relay link to successfully complete the whole mission, a probe-satellite relay communication link was established in advance after these two targets having been sent into space. Therefore， an all-directional TT&C data transmission link for in-orbit relay communication test is indispensable. The scheme design on lunar probe and lunar relay satellite is summarized. First, the relay communication process is introduced while the principles for relay communication link establishment are concluded by introducing the flight orbit characteristics of both lunar probe and relay satellite. Then a data flow chart for modules of probe in communication with satellite is shown. Besides, a scheme design for relay communication link establishment of probe and satellite is presented, including the selection of relay communication link establishment test arc, allocation for ground TT&C stations, flight attitude design for test, test item design in coverage of overall data flow between facilities in single capsule and between different capsules, and flight procedure design for relay communication link establishment. Finally, inorbit test result is demonstrated, and it is indicated that this designed scheme on relay communication link establishment of probe and satellite satisfied the mission requirements. The compatibility of interfaces between the probe and relay satellite is verified and the correctness is testified via in-orbit test process. Comprehensive factors such as allocation of resources on the ground, flight safety, flight attitude design, flight procedure design, relay communication link design, and data flow design have been taken into account within this scheme. Moreover, through modular design method, it can be flexibly adjusted to accommodate various launching windows and orbital phase changes between the probe and relay satellite, providing a stable foundation for technical knowledge and in-orbit flight experience of relay communication link establishment between complex integrated spacecraft and cooperative relay communication target for follow-up missions in the coming future and is of promising application prospects.

Key words: autonomous sample and return mission, lunar relay satellite, relay link establishment, in-orbit test, omnidirectional telemetry and command telecommunication, directional data transmission