China had successfully launched its first lunar exploration satellite Chang’E-1 (CE-1) on 24 October 2007 at lunar circle orbit ~200 km. A duplicate CE-2 at lower orbit ~100 km was also launched in 1 October 2010. A multi-channel microwave radiometer, for the first time, was aboard the CE-1 (and CE-2) satellite with the purpose of measuring the microwave thermal emission from the lunar surface layer (Jiang and Jin 2011). There are four frequency channels for CE-1 microwave radiometer: 3.0, 7.8, 19.35 and 37.0 GHz. The observation angle is 0°, the spatial resolution is about 35 km (for the channels 7, 19, 37 GHz) and 50 km (for 3 GHz), and the radiometric sensitivity about 0.5 K. The measurements of the multi-channel brightness temperature,
, are applied to invert the global distribution of the regolith layer thickness, from which the total inventory of
He (Helium-3) stored in the lunar regolith layer can be estimated quantitatively (Jiang and Jin 2011; Fa and Jin 2007a,b; 2010a,b; Jin and Fa 2009, 2010).