An Intelligent 2-D Chart Method With Autodetection for Weak Quasar Blind TDD Estimation in Deep Space △DOR Measurement

To achieve high accuracy navigation for deep space probes, the △differential one-way ranging (△DOR) measurement relies on the corrections from the time delay difference (TDD) estimation of reference weak Quasar signal, which is guided by the forecasting data compensation. However, disturbed by the interference, the forecasting data sometimes is unavailable, which directly leads to invalid compensation and Quasar TDD estimation failure. In this article, an intelligent 2-D chart method with autodetection is proposed for △DOR measurement without forecasting data support. Consisted of 2-D correlation chart generation, two stages autodetection and rough estimations iteration refining, the proposed scheme realizes the autodetection and TDD blind estimations of weak Quasar signal. The validation experiment is established with developed radio science software defined receiver systems, which are installed in ground stations for space △DOR navigation and positioning. Results show that the presented 2-D correlation chart extends the system weak Quasar signal detection ability with signal SNR can reach –23 dB. The overall accuracy of designed two stages autodetection for Quasar correlation spectral line search is 85.17%. The proposed scheme improves the utilization rate of Quasar data collected by the system by 24.01%. And the average P-F curve fitting residue error which reflects the TDD estimation accuracy is 0.1931/rad. It proves an equivalent precision to accurate forecasting data processing, which meets the △DOR measurement accuracy requirements.