Acquisition and tracking of high dynamics Doppler profiles for space applications

In this paper, we use an adaptive sweep carrier acquisition and tracking algorithm to acquire and track high dynamic Doppler frequency profiles with high Doppler shift, Doppler rate, and Doppler acceleration. The acquisition and tracking system is a Phase-Locked Loop combined with a bidirectional smart sweeping algorithm. This system is a modified version of previously proposed method that enhances the performance in high dynamic Doppler scenarios. Therefore, our goal is to acquire the received carrier in the presence of high dynamics, over a short acquisition time, while operating at the lowest possible received carrier to noise ratios experienced in realistic flight scenarios. Additionally, in the paper we discuss the system parameters that are key to have a robust acquisition and tracking system for such scenarios. For simulations, we considered Doppler profiles of Goldstone to Mars Science Laboratory (MSL)- Curiosity Rover, Entry, Descent, and Landing (EDL), and Lunar South Pole (LSP) to Lunar Relay Satellite (LRS). Both S-Band, and X-Band were considered for Doppler profiles. For simulations and results, we used MATLAB Simulink models to prototype the system. The true and estimated Doppler frequency, threshold, and direction functions, as well as Doppler estimation errors during tracking mode were obtained from simulations. Similarly, the standard deviation of Doppler estimation error was measured at various received carrier to noise ratios and compared with an approximated analytical result both for a 2nd and a 3rd order loop.