Correction method of the manned spacecraft low altitude ranging based on γ ray

γ photons altimeter, which is a low altitude measurement of the spacecraft based on Compton effect at the moment when it lands on earth, is an important equipment for spacecraft landing control. Manned spacecraft landing control needs γ-ray altitude control system to revise ignition signal for retrograde landing rocket at different landing speed. To make the spacecraft speed zero at the moment landing on the surface, a method that makes ignition altitude correction of the spacecraft at different landing speeds is figured out, which is based on the number of γ-ray particles reflected field gradient. According to the established theoretical model, the method feasibility is proved by a mathematical derivation and verified by an experiment, and the adaptability of the method under different parameters is also described. The results indicate that the error of the altitude signal error is less than 0.05 m at the height of 0.5 m to 1.5 m when the landing speed of spacecraft is in the range of 6 m/s to 10 m/s. The method provided has great significance for the manned spacecraft engineering need.