A SINGLE CHANNEL COMMAND DETECTOR FOR DEEP SPACE MISSIONS

Abstract

AEG-TELEFUNKEN has developed a Single Channel Command Detector which will be used in the solar probe HELIOS. This command detector demodulates command data, PSK-modulated on a subcarrier with a symbol error-probability of less than 1x10^-5 at an input signal to noise ratio of 13,2 db per symbol-length. The command detector consists of two succeessive second-order phase locked loops and a matched filter. The subcarrier synchronizer loop tracks the 512 Hz subcarrier, the bitsynchronizer loop performs data-synchronisation and in contrast to former space concepts, requires no additional power. The matched filter correlates the input signal and its estimate, generated by the subcarrier synchronizer-loop. The integration over exact dataperiods is dumped by the bitsyncpulse. This command detector enables the HELIOS Receiver chain to demodulate command data with less than 1 error in 100 000 symbols over a distance of ~ 300 mill. km. Due to sophisticated digital decoding of the HELIOS Decoder, this error-probability results in 1 false command being executed in 64 years.