Dynamic Imaging Simulation and Angular Measurement Performance Degradation of Interferometric Star Trackers

Interferometric star trackers (ISTs) achieve high-precision angular measurement by encoding the stellar incident direction into multichannel interference phases. Besides image smearing, platform motion continuously changes the interference phase during a finite exposure, an effect not captured by conventional geometric star-image models. However, the quantitative relationship between platform motion characteristics and interferometric measurement degradation, which is essential for dynamic performance assessment and system-level optimization of ISTs, remains insufficiently characterized. We develop a full-link dynamic imaging model that incorporates broadband stellar radiation, multiple synthetic diffraction orders, multichannel energy modulation, exposure integration, and detector noise. The four-channel response is expressed as the temporal mean of a complex interference phasor, whose magnitude and argument define the modulation retention factor and dynamic phase bias, respectively. Static angular scanning experiments yield correlation coefficients above 0.97 between simulated and measured channel responses. Under a locally linear phase-to-angle relationship along the interferometric sensing direction, constant-rate motion produces a sinc response, whereas integer-cycle periodic jitter produces a zeroth-order Bessel response. For noninteger-cycle jitter, the response additionally depends on the exposure-to-jitter period ratio and initial phase. When constant-rate motion and periodic jitter coexist, they modulate the same phasor and produce a generally nonseparable response. Within the investigated parameter range, the maximum absolute difference in modulation retention between the coupled response and the independent sinc–Bessel product reaches approximately 0.58. This peak occurs near a normalized phase sweep of 1 and a normalized jitter-induced phase amplitude of 0.8. The model provides a basis for defining dynamic operating limits and selecting exposure parameters and platform stability requirements for ISTs.