Stability and error analysis of a typical earth horizon scanning sensor system

The purpose of the paper is to present a study of the earth horizon scanning sensor's stability and performance characteristics. The open-loop frequency response of the servo system is analyzed to evaluate the open-loop gain and phase margins. The values of poles and zeros are varied from the nominal to determine the effects on the stability margin. In the closed-loop response study, the nominal and the worst case transfer functions are used to calculate the time responses to a step function and a sawtooth waveform input voltages. The steady state response characteristics between the space clamp and the peak signal point are calculated. The earth sensor noise angular errors and the instability (null shift) errors based on a specified threshold level are presented for various earth radiance levels.