A Study on "Nadir Hole" in Space Based Radar

Nadir hole in monostatic Space based radar(SBR) is described at first and a judgement rule about nadir hole is summarized from mathematical point of view based on the spherical-earth assumption.Then two expansion judgement rules about nadir hole-fill in bistatic SBR are proposed,which supply the theoretical basis for the capability of resolving nadir hole in bistatic SBR.Based on the two expansion rules the resolving method of nadir hole does not need to increase the total numbers of satellites,which is a remarkable result for reference in the constellation design in SBR.