Limitations of Daytime Star Detection Based on Attitude-Correlated Frames Adding

In order to expand the applications of daytime star tracker (ST) to low-altitude platforms, it is necessary to solve the problem of daytime star detection inside the atmosphere. Currently, the short-wave infrared (SWIR) camera with InGaAs sensor is widely used for daytime ST, to suppress the strong background radiation during daytime. The attitude-correlated frames adding (ACFA) approach can be used to further improve the sensitivity to starlight by correlating and adding successive star images. However, InGaAs sensor has both temporal and spatial noise charge, distinct from charge coupled device (CCD) detectors. These two types of noise exhibit different growth trends during the stacking process, which limits the improvement of the star detection capability of the AFCA. To accurately estimate the limitations of daytime star detection after using ACFA, the influence of this approach on the signal-to-noise ratio (SNR) of star images is revealed. The noise model of InGaAs sensor is first established in this article according to the imaging process of the SWIR camera. Then the changing trend of gray value noise and SNR growth factor with the number of correlated frames is theoretically derived for SWIR star images. Finally, the SNR improvement based on ACFA is proved by the results of stacking the star images. It successfully improves the star detection capability of the ST under dynamic conditions. The star detection limitation of
${H}$
-band magnitude is expected to increase from −0.21 to 1.5 by ACFA.