The climate on Earth is affected by the Sun. It is thus necessary to determine the solar spectral irradiance (SSI) with high precision on the ground for the improved accuracy of climate models used for Earth. To achieve this purpose, a solar spectral irradiance monitor (VISM) with a wavelength ranging from 380 to 2400 nm is developed. In this work, the optical design and spectral calibration of the VISM are explored, with two optical paths designed to determine the SSI in the wide spectral region. One of them is the main optical path through which the sunlight is dispersed and imaged by a single Féry prism. A laser and a concave mirror are used in the other optical path to determine the rotated angle of the Féry prism, which is crucial to determining the spectral information. Furthermore, a new spectral calibration method is developed for VISM. According to this method, the dispersion equation of the prism is combined with the results of three characteristic wavelengths to determine the relationship between the dispersed wavelengths and the pixels in the detector for the whole spectrum. An apparatus is set up in the laboratory for spectral calibration. It is revealed that the uncertainty of spectral calibration is about 0.3 nm, which exceeds the design requirement. When the designed VISM works outdoor, the SSI can be determined readily. It is shown that the optical design and spectral calibration proposed in this study for VISM are correct.
Attitude fluctuation of satellite platform is a crucial error source that influences the performance of the satellite
surveying and mapping and extensively existed in all spacecrafts. Verification and detection of fluctuation frequency of
the high spatial resolution remote sensing satellite plays a key role in farther optimizing the geo-location accuracy when
the geometric accuracy of satellite reaches a fairly high precision. In this paper, an approximate sampling theorem is
designed to verify and detect the attitude fluctuation frequency of satellite, and this novel method is based on Nyquist-
Shannon sampling theorem, which applies ingeniously attitude acquisition time interval. The sampling interval of this
approach will be appropriately altered by proposed sampling model while the satellite attitude acquisition frequency is
not proportional to the fluctuation frequency. A simulative triangular wave and a strip attitude data of ZY-3 obtained
while satellite was early on-orbit are experimented, and these results demonstrate the following findings: 1)the method
proposed is effective and can filter irrelevant wave partially; 2)the fluctuation components obtained contain a distinct
frequency of around 0.67Hz meets the inherent frequency of ZY-3 detected by other methods.
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