Research On Autonomous Orbit Determination With Spaceborne GPS Measurements Assisted By Onboard Accelerometer

High-accuracy autonomous orbit determination based on GPS is a fundamental requirement to Low Earth Orbit satellites(LEO).With the development of observation accuracy random model and mathematical model recently,GPS based autonomous orbit determination techniques is dramatically improved in equations of motion,perturbation force models and statistical orbit determination theories.As a result,the autonomous orbit determination is efficiently performed with increasingly real-time accuracy.However,LEO is frequently adjusted called orbit maneuver because of orbit altitude and atmospheric drag which may lead to the divergence of filter algorithm.And the atmospheric drag considered to be a challenging task of modern orbit determination is also a main influential factor for orbit accuracy.Therefore,to relize the autonomous orbit determination as the LEO orbit maneuver and acquire more precise non-gravitational perturbations all play important roles in the improvement of stability and reliability of autonomous orbit determination techniques.With the purpose of solving the above-mentioned problems,studies on appropriate autonomous orbit determination methods for the LEO orbit maneuver are performed in this paper.Non-gravitational perturbation models are replaced by GPS based accelerometer data in order to propose the method which is autonomous orbit determination with spaceborne GPS measurements assisted by onboard accelerometer.The main contents consist of the following several points:(1)At first,autonomous orbit determination method based on accelerometer data are constructed with the traditional reduced-dynamic orbit determination theory.And a comparing method,which is designed by comparing the accelerometer data and the non-gravitational perturbation model acceleration accordingly,is adopted as the filter initialization for accelerometer data bias parameters.The proposed comparing method is used to calibrate GRACE accelerometer data compared with the reference GRACE calibration parameters.Tests have show that the calibration accuracy of the comparing method achieve 1.77×10-8.1.69X 10-8.3.51 ×10-8 m/s2,respectively.These results outperform the reference GRACE calibration parameters by 73.58%?96.98%?45.68%,respectively.It is obvious that the proposed comparing method has an advantage in the convergence of filter precisely and efficiently;(2)In order to define the state vector of the constructed autonomous orbit determination method based on accelerometer data,the influences of accelerometer calibration parameters and experience acceleration on orbit determination results are evaluated.Continous orbit determination experiments for long epochs are carried out in comparison with autonomous orbit determination method based on non-gravitational perturbation models.Tests have show that for the autonomous orbit determination method based on non-gravitational perturbation models,its position accuracy achieve 0.872?0.913 m for GRACE-A and GRACE-B respectively.And its velocity accuracy achieve 1.080?1.126 mm/s.While for the autonomous orbit determination method based on non-gravitational perturbation models,its position accuracy achieve 0.830?0.878 m for GRACE-A and GRACE-B respectively which outperform the former method by 4.2?3.5 cm.And its velocity accuracy achieve 1.005?1.063 mm/s which outperform the former method by 0.075?0.063 mm/s.These improvements fully prove the autonomous orbit determination method based on accelerometer data to be correct and reliable;(3)The autonomous orbit determination with spaceborne GPS measurements assisted by onboard accelerometer is used for the real GRACE satellites maneuver compared with the autonomous orbit determination method based on non-gravitational perturbation models.Tests have show that the autonomous orbit determination method based on non-gravitational perturbation models is not available at the period of GRACE satellites maneuver because of insufferable large orbit deviations which can be 9921.710?10353.729 m for GRACE-A and GRACE-B respectively.And the velocity accuracy can be 1075.040?1081.843 mm/s.But the proposed autonomous orbit determination with spaceborne GPS measurements assisted by onboard accelerometer is well operated with orbit accuracies 0.985m.1.021 m for GRACE-A and GRACE-B respectively.And the velocity accuracy can be 1.182?1.204 mm/s.The improvements fully indicate the effectiveness of the proposed method.In this paper,the main innovating point is combining the autonomous orbit determination method based on non-gravitational perturbation models and the autonomous orbit determination method based on accelerometer data.This combination confirms the computation efficiency and realizes the high-accuracy orbit determination for LEO maneuver meanwhile.The proposed method can provide continous and reliable orbit results and improve the stability and reliability of GPS based autonomous orbit determination techniques.