Nowadays, spectrometers are being increasingly used in the remote sensing of the earth system processes and they can be
well conducted field spectral calibrated by using absorption features of atmospheric profile. The spectral calibration
accuracy of an ASD spectrometer in different atmospheric conditions is analyzed in this paper. First of all, set the atsensor
spectral radiance spectrum as the reference spectral curve, which is generated by the MODTRAN5 radiative
transfer model outputs convolved with the spectral response function of each channel. The results can be totally different
when input different water vapor contents. Meanwhile, under the same atmospheric conditions (the same observation
target, the sun elevation angle, azimuth, aerosol distribution, composition and concentration distribution of
atmosphere..etc. ), the diffuser whiteboard is measured by the ASD spectrometer to acquire observed spectral curve. The
best spectral matching algorithm is used to compare the observed spectrum with the reference one. Central wavelength of
the ASD is obtained by calculating the results of matching spectrum shifts within feature spectrum range. Finally,
quantitative analysis and calculation about the effect on the accuracy of instrument spectral calibration with different
water vapor contents is presented.
Aspheric surfaces are widely used in aerospace sensing optic instruments. There are numerous reflecting optical system
designs that call for oblate elliptical surfaces, such as secondary mirror or tertiary mirror in three mirror anastigmat
(TMA). The consequence brought by increase in field of view (FOV) and speed of optical system is the decrease in F/#
of aspheric surface which makes its production harder. Due to oblate ellipsoid's stigmatic points are not lined up on the
optic axis, null lenses corrector is used more often than the stigmatic null test especially in low F/# aspheric surfaces test.
Three types of null lenses tests for an oblate elliptical surface with aperture Φ360mm, F/0.8, conic=0.243 are presented
including a new type which is modified by replacing the reference flat and null lens with one lens with reflect surface.
Furthermore, sensitivity tolerances for each design are practiced.
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