Methods for increasing the wavefront detection SNR based on extended-beacon

In order to achieve and maintain high resolution imaging performance in space-based earth-observing system, extended-beacon (extended-scene) and H-S wavefront sensors are employed to estimate the pupil wavefront for compensating the aberrations. Taking this model into consideration, sufficient illuminance of the extended-beacon is required, thus directly constrains the application of extended-beacon to the space-based earth-observing system. By the derivation and analysis of the signal to noise ratio (SNR) formula of the sub-aperture image on the detector array, two methods are proposed to raise the SNR: decreasing the lateral magnification of the wavefront sensing system and increasing the number of measurement. The feasibility of these two methods is shown by a practical example.