Technology of Precise Measurement of Slit Aperture Area

In order to achieve the absolute uncertainty which is less than 0.05%and the relative stability which is 0.03%per year in 0.4～1.0μm of solar absolute spectral irradiance observation,the slit aperture area must be measured with high-precision in the development of solar absolute irradiance spectra-radiometer.The flux comparison method is developed by using laser scanning for precise measurement of the slit aperture area.The laser-illuminated integrating sphere system is used as a light source,and the high-precision.trap detector is used to receive signals.Small size apertures can be measured without a reference aperture.In the measurement of the entrance area of solar absolute irradiance spectra-radiometer of which the nominal area is 7 mm×0.l mm,the total relative uncertainty is about 4.5×10~(-4).