The keys to the improved approach to testing complex pointing and tracking systems are the coherence analysis algorithms developed in recent years by Dr. Julius Bendat et a!. The underlying concept is that all environmental and test induced disturbances are instrumented and simultaneously recorded with the signals that characterize the pointing and tracking system performance. The hypothesis on which data analysis is predicated is that a set of measured disturbances (or inputs) accounts for the measured performance error (output). The coherence analysis algorithms permit the test analyst to break up the performance signal into components caused by each of the input paths and to quantify that part of the performance not allocatable to any of the measured disturbances.
The authors have exploited the coherence analysis methods to accurately characterize the tracking and stabilization performance of equipment being prepared for a space experiment. The environment in the ground test facilities is significantly different from that expected in the space environment and would have obscured the true system performance. Therefore, vibration signals acquired on a high bandwidth, simultaneous data collection computer were analyzed using the multiple input coherence analysis algorithm to accurately determine influences of each disturbance input on the performance. This paper presents a tutorial on the advanced testing methodology and illustrates how significant testing challenges were addressed. The ability to confirm the adequacy of the system performance would not be possible without the use of the advanced tools. The techniques are applicable to system level performance testing of a broad range of complex pointing and tracking systems.