Limited magnitude detectivity of space-based opto-electronic telescope

Based on the basic principles of radiometry and photometry, the limited detectable magnitude formula of space-based telescope was derived by analyzing the features of target photometry signals and the optical signals of CCD noises. According to the equation, the limited detectable magnitude was studied with illumination and without illumination respectively. By using a set of typical parameters, the limited detectable magnitude was 14.2 without illumination, and then the relationship between the limited detectable magnitude and the parameters was discussed in detail. In the case of illumination, the relationship between magnitude and the sun angle was studied. As a result, the sun illumination has great effect on the limited detectable magnitude. Consequently, the space-based optoelectronic telescope can only work without sun direct illumination.