The Measurement Of The Main Aperture Of Solar Irradiance Absolute Radiometer

The change of solar irradiace has a great effect on the global climate and environment. It is important to accurate measure and long-term monitor the solar irradiance. On 60’s, the type of plane radiometer was developed by Changchun Institute of Optics, Fine Mechanics and Physics. To the 90’s, the type of cavity Solar Irradiance Absolute Radiometer(SIAR) was manufactured. Then Solar Irradiance Monitor(SIM) was researched successfully. The SIM is composed of Solar Irradiance Absolute Radiometers(SIARs). The SIMs boarded on FY-3meteorological satellites and Shenzhou III spacecraft have made a long-term monitoring about the change of the solar irradiance subsequently. The SIAR is a type of dual-conical cavity compensation absolute radiometer. A main aperture is in front of the cavity of SIAR.It is a kind of knife edge circular aperture and its area need to be high-accuracy determination. The aperture area determines the solid angle needed for the definition of radiant intensity, so it determines the measurement accuracy of the SIAR directly.The main aperture area was measured by a Universal Tool Measuring Microscope in our laboratory previously. The main aperture area is defined by the relationship between the diameter and the round area(geometric method). And the measurement accuracy of this method is low. The effective-area method is proposed to solve the measurement requirements which measure the aperture area in optical method. This method defines the main aperture based on the aperture of beam-limiting effect in radiometric measurement. The measurement accuracy of this method is high. The effective-area method improves the solar irradiance measurement accuracy of SIAR,indirectly.Firstly, the measurement principle of the effective area method is introduced. Themeasurement formula is derived based on the measurement principle. From the measuring device of the effective area method to analysis and design the total measurement scheme of the effective area method. Several important parts of the measuring device are presented, including the source system, measurement system,monitoring system and control system. A detailed study on the light source of Gaussian beam are given, including the selection of the waist of laser beam and the stability of output power. At the same time, a detail research on the step-size of the precision translation stage is provided. Integrating sphere detectors are designed in measurement and monitoring systems.Secondly, the effective area method device is established through the design of specific measurement scheme. The details of the measurement equipment of effective area method are given, including the type of equipment and the characteristics. Two different main aperture area are measured by the effective area method measurement device. And the measurement results with the uncertainty budget are given. The relative standard uncertainty of the results within a series of repeated measurements is typically57 10??(n=7).Finally, in order to eliminate the non-uniformity response of integrating sphere detector which is brought by the back surface of the measured main aperture serving as a part of the integrating sphere wall in effective area method, a correction optical model is designed to tackle the issue in TracePro program. By simulations, the radiant flux responded by the integrating sphere detector is given. Then the curve of the relative change about the radiant flux is deduced and the experiment measurement data are corrected on basis of the relative change curve.