Research On LEO-LEO Occultation Receiving Techniques

Radio occultation is an important approach to the near space environment detecting.The GNSS-LEO radio occultation has been applied to the Earth's neutral atomsphere and ionosphere detecting since the mid-1990 s and yielded great achievements.However,the accuracy of the GNSS-LEO occultation cannot meet the detecting requirement of the neutral atmosphere above 60 km due to the influence of the ionosphere and gradual Doppler decrease generated by the neutral atmosphere.In order to solve this problem,we proposed the LEO-LEO occultation detecting scheme for the neutral atmosphere above 60 km.So far,there is no practical LEO-LEO occultation detecting system all over the world.Domestic research on the LEO-LEO occultation mostly aimed at the simulation studies of occultation characteristics,or simulation of orbital parameters.No domestic researchs on transmitter or receiver of the LEO-LEO occultation are found.In this paper,a prototype of LEO-LEO occultation signal receiver based on software defined radio technology is designed and developed successfully.It achieved high-dynamic and high-precision occultation signal open-loop/closed-loop tracking as well as amplitude and phase information extraction.Actual testing to the performance of receiver prototype shows that the uncertainty of occultation signal phase measurement is about 0.12 mm,and the measurement bandwidth of Doppler frequency is about 3MHz,which satisfies the detection requirements of 60 to 90 km of neutral atmosphere.