Optimum Strategies for Monitoring the Operational Status of a Spacecraft

The design of a spacecraft-monitoring system based on a Neyman–Pearson detection criterion is discussed. Each noncatastrophic state of the spacecraft is indicated by the transmission of a specific signal to the ground station. Complete failure of the spacecraft is indicated by the transmission of no signal. The set of signals chosen to represent the spacecraft states consists of a group of orthogonally spaced (in frequency) carriers each with unknown (random) phase. Receiver structures derived from maximum-likelihood considerations are proposed that provide suitable performance in the presence of frequency uncertainty (due to Doppler) and frequency rate uncertainty (due to oscillator drift). Numerical results are obtained from a combination of analysis and simulation and indicate the trade-offs among the various receiver structures between performance and implementation complexity.