Abstract: Considering the working conditions of satellite sensors in earth observation， the loading experiments of rock under the condition of cold sky background were carried out. The influence of cover layers on microwave radiation from loaded bare rock in elastic phase is analyzed， and the influence mechanism is discussed as well. The horizontal loading machine and C band microwave radiometer were applied for observing the microwave radiation from the stressed granite samples covered by different materials: dry or humid silver sands. The experimental results show good synchronicity between the microwave radiation and the loaded stress in the elastic deformation phase of granite samples， which with the correlation coefficient of 0.94 and the microwave brightness increases by 0.015K/MPa. When covered by dry or humid sands(with layer thickness of about 2.5cm)， the characteristics of affected microwave radiation from the stressed rock are much different: 1)the dry sand has no obvious influence on the affected microwave radiation from stressed rock; 2)the humid sand weakens the signals received by microwave radiometer significantly.

Key words: remote sensing-rock mechanics, microwave radiation, sand cover, sky cold background, water