Code acquisition under strong dynamics: The case of TT&C for LEOP

Abstract

This paper tackles the issue of code acquisition of Spread Spectrum (SS) signals used for Telemetry, Tracking and Control (TT&C) of satellites operating in the Launch and Early Orbit Phase (LEOP). Peculiar to this scenario is the very low signal to noise plus interference ratio, that requires very accurate frequency estimation during code acquisition in order to guarantee the lock of the tracking loops. In this work we introduce a multi-dwell architecture composed of a first detection stage, aimed to perform coarse measurements of code delay and frequency offset, and a refinement stage in which very accurate estimations of signal frequency offset and Doppler rate are carried out. The proposed methods are tested by means of numerical simulations in terms of estimation accuracy and mean acquisition time and compared with classical code acquisition strategies, yielding compelling results and proving their effectiveness.