Light Source Stability Issues and Measurements in Flux Calibrations for Space Gaze Camera

Flux calibration is an important test item in laboratory calibration experiments of space gaze cameras, which is the basis for obtaining high-precision scientific application data. In the flux calibration of a space gaze camera, the multi-field calibration method is adopted. The instability of the calibration light source will introduce uncertainty during the calibration process. When the spatial camera adopts the gaze imaging mode, the stability of the light source indicates the change in the total energy received by the image plane during the gaze time, which is characterized by relative uncertainty. When the luminous intensity standard lamp runs for the long-term calibration of the stability of the calibration light source, real-time performance and accuracy cannot be guaranteed. Therefore, it is proposed to use a photodetector to measure the stability of the calibration light source for long-term and real-time accurate measurements. First, the stability of the photodetector is calibrated using the light emitting diode; then, the stability of the calibration light source is measured using the photodetector; finally, the stability uncertainty of the calibration light source and the measurement uncertainty of the method is evaluated. The results of the simulation analysis and experimental verification indicate that the gaze time is 5 min and the sampling frequency of the photodetector is 15 Hz; for example, when the flux calibration time is 8 h, the stability uncertainty of the calibration source is 0.42%, and the relative measurement uncertainty is 0.01%.