Order-adaptive frequency trackers for direct-to-Earth Mars communications

During the entry, descent and landing phase (EDL) of the missions to Mars, the spacecraft´s high dynamics imprints severe Doppler swings on the signals transmitted via the direct-to-Earth (DTE) channel. In order to recover the data that record the mission status from the received signal, a reliable estimate of the Doppler profile is required. We extend previous work by developing order-adaptive schemes that enforce frequency continuity and improve tracking performance and, as a result, the overall frequency mean-square error as well.