Ground Calibration Method for the Chang’E-7 Lunar Microwave Imaging Radar

After the Chang’E-7 lunar microwave imaging radar in the fourth phase of the Lunar Exploration Project is put into on-orbit operation in the future, calibration devices will not be deployed on the lunar surface, making on-orbit External calibration impossible. To ensure the acquisition of high-precision lunar surface image data, a ground calibration method is proposed. This method combines the internal calibration of the radar system with the performance calibration in the inner field. During ground testing, the internal calibration accuracy and the consistency of internal calibration channels are obtained by measuring the temperature characteristics of the internal calibration network under a full-temperature environment. The internal calibration constants are acquired in an anechoic chamber. By constructing a wireless transceiver environment in the inner field with the help of the anechoic chamber, the absolute transceiver gains and the stability of the transceiver channels of the system are accurately calibrated. The basic data obtained through ground calibration can be used for the calibration of indicators such as on-orbit internal calibration constants, absolute and relative radiation accuracy, and polarization channel consistency, providing guarantee for high-resolution lunar surface exploration.