Scholarlink

The Pakistan Lunar Exploration CubeSat, carried by the Chang ‘e-6 spacecraft of China's lunar exploration project, was released from the orbiter on May 8, 2024 and successfully returned lunar images. With a total mass of only 6.5 kg, the CubeSat, jointly developed by Institute of Space Technology (IST) in Pakistan and Shanghai Jiao Tong University, is China's lightest orbiting satellite around the moon. It is the first time in the world that the Earth Moon satellite TT&C communication with uplink residual carrier and downlink suppressed carrier is adopted, and orbit determination is achieved only by coherent carrier velocity measurement. The TT&C subsystem of the satellite consists of an X-band transponder and four X-band conical spiral antennas. A residual carrier secondary PM modulation system is used for uplink, while downlink telemetry transmission employs a suppressed carrier direct BPSK modulation system. It features precision speed measurement of uplink and downlink coherent carriers, considering the equipment of China's deep space tracking stations while reducing the transmitter's power consumption, size, and weight. The transponder’s specifications include an uplink data rate of 125 bps, downlink data rate of 1000 bps, receiving sensitivity of −127 dBm, transmission power of 1 W, power consumption less than 10 W, dimensions of 147 mm * 92 mm * 64 mm, and a weight of 0.7 kg. The size of a single antenna is ɸ43 mm*52 mm, and the total weight of four antennas and RF cables is about 0.2 kg. Four antennas constitute omni-directional coverage, two left-handed circular polarizations for receiving and two right-handed circular polarizations for transmitting. The gain is greater than −5 dBi in the 90% Angle range, and the minimum gain at the concave point is −10 dBi, including cable and power splitter losses. The X-band Transponder functions normally in orbit, with stable tracking and locking of uplink signals. The downlink telemetry signal-to-noise ratio (Eb/N0) is approximately 20 dB, matching theoretical calculations.

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Design of the TT&C Subsystem for Lunar Exploration CubeSat in “Chang'e-6” Mission

  • 会议论文

  • 发表日期：

    2025年

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  • Qiankun Mo,
  • Jun Liu,
  • Xuelin Li,
  • Yifei Jiang,
  • Yixin Huang

摘要

The Pakistan Lunar Exploration CubeSat, carried by the Chang ‘e-6 spacecraft of China's lunar exploration project, was released from the orbiter on May 8, 2024 and successfully returned lunar images. With a total mass of only 6.5 kg, the CubeSat, jointly developed by Institute of Space Technology (IST) in Pakistan and Shanghai Jiao Tong University, is China's lightest orbiting satellite around the moon. It is the first time in the world that the Earth Moon satellite TT&C communication with uplink residual carrier and downlink suppressed carrier is adopted, and orbit determination is achieved only by coherent carrier velocity measurement. The TT&C subsystem of the satellite consists of an X-band transponder and four X-band conical spiral antennas. A residual carrier secondary PM modulation system is used for uplink, while downlink telemetry transmission employs a suppressed carrier direct BPSK modulation system. It features precision speed measurement of uplink and downlink coherent carriers, considering the equipment of China's deep space tracking stations while reducing the transmitter's power consumption, size, and weight. The transponder’s specifications include an uplink data rate of 125 bps, downlink data rate of 1000 bps, receiving sensitivity of −127 dBm, transmission power of 1 W, power consumption less than 10 W, dimensions of 147 mm * 92 mm * 64 mm, and a weight of 0.7 kg. The size of a single antenna is ɸ43 mm*52 mm, and the total weight of four antennas and RF cables is about 0.2 kg. Four antennas constitute omni-directional coverage, two left-handed circular polarizations for receiving and two right-handed circular polarizations for transmitting. The gain is greater than −5 dBi in the 90% Angle range, and the minimum gain at the concave point is −10 dBi, including cable and power splitter losses. The X-band Transponder functions normally in orbit, with stable tracking and locking of uplink signals. The downlink telemetry signal-to-noise ratio (Eb/N0) is approximately 20 dB, matching theoretical calculations.