Prelaunch calibration of Chang´E-2 Lunar Microwave radiometer

CE-2 Lunar Microwave Sounder (CELMS) is the second passive microwave radiometer in the world to sound the surface of the Moon on the orbit of 100 km. The scientific objective of CELMS is to further obtain global brightness temperature (TB) of the Moon, to retrieve information on lunar regolith, and to evaluate the distribution of helium-3 on the Moon. Before launch of CELMS, calibration experiments were carried out in laboratories to test the performances of the systems, and to derive transfer parameters on the transfer paths of CELMS. This paper the procedure of calibration is introduced and the method of computing the coefficients of each path is given. The calibration results on nonlinearity and accuracy of the system are summed and analyzed.