Computation of intermodulation and interference in telecommand due to the ranging signal of the ESA multi purpose tracking system: lack of degradation

The performance of the European Space Agency (ESA) spacecraft telecommand subsystem due to simultaneous ranging is analyzed. The use of the ESA multipurpose tracking system, which represents an improved version of the deep space tracking system, is assumed. Numerical results show that the telecommand bit error rate degradation is negligible and that the frequency optimization proposed by T.M. Nguyen (IEEE 1987 National Symp. on Electromag. Compat., Conf. Record, p.308-17) is not applicable because of the wrong Fourier code expansion proposed. It is also shown that the interference level strongly depends on the relative phase between the telecommand subcarrier and the ranging tone, so that it cannot be neglected as assumed by Nguyen.<>