Correlator based group delay measurement for delta-DOR signals

Abstract

Very Long Base Line Interferometry (VLBI) is a technique that allows determination of angular position of spacecraft by measuring the geometric time delay between received radio signals at two geographically separated base stations. Delta Differential One Way Ranging (Delta-DOR) is an application of VLBI where delay measurements of a spacecraft radio signals are compared with delay measurements of angularly nearby quasar radio signals. Delta-DOR is a framework that can increase the accuracy of deciding the Spacecraft position in deep space when combined with other navigation techniques. Navigation and tracking of spacecraft is rudimentary until it reaches its designated orbit. The Delta-DOR correlator system gathers signals from independent antennas which are then processed to find essential data used for guidance and navigation of spacecraft. The high speed parallel correlator designed can calculate delay up to 64 lags, with a maximum integration time of 800μs. The design was synthesized using Xilinx ISE 14.1 and simulated with ISim and validated on Virtex-5 family ML510 Embedded Development platform. The correlator structure chosen is amenable for expansion to calculate larger lags in future.