Abstract
The visible-IR scanning radiometer (VIRR) of FY1-C/D meteorological satellites consists of 10 bands with 4 different focal plane assemblies (FPAs). However, there are significant band-to-band registration (BBR) errors between different bands, which cannot be compensated for by a simple shift in the along-scan direction. A rigorous BBR frame was proposed to analyze the sources of misregistration in the whisk-broom camera. According to theory, the 45° scanning mirror introduces tangent function style misregistration in the along-track direction and secant function style misregistration in the across-track direction between different bands if the bands are not in the same optical axis. As proven by the experiments of both FY-1C and FY-1D, the image rotation caused by the 45° scanning mirrors plays a major role in the misregistration. However, misregistration between different FPAs does not strictly adhere to this theory. Therefore, a polynomial-based co-registration method was proposed to model the BBR errors for the VIRR. To achieve 0.1 pixel accuracy, a fourth-degree polynomial was used for BBR in the along-scan direction, and a fifth-degree polynomial was used for the along-track direction. For the reflective bands, the root-mean-square errors (RMSEs) of misregistration could be improved from 3 pixels to 0.11 pixels. Limited by matching accuracy, the RMSEs of misregistration between thermal bands and reflective bands were approximately 0.2 to 0.4 pixels, depending on the signal-to-noise ratio.
Highlights
The FY-1C and FY-1D satellites are the second group of Chinese polar-orbiting meteorological satellites after FY-1A and FY-1B launched on 10 May 1999 and 15 May 2002.Compared with the main payload of the first generation, the number of bands of the visible-IR scanning radiometer (VIRR) increased from 5 to 10
The FY-1C and FY-1D VIRRs suffered from large misregistrations
We proposed a theoretical framework for analyzing the bandto-band registration (BBR) of the VIRR
Summary
Compared with the main payload of the first generation, the number of bands of the visible-IR scanning radiometer (VIRR) increased from 5 to 10. The 10 bands acquired imagery with 5 spectral groups, including visible (VIS) bands 1, 7, 8, and 9, near-infrared (NIR) bands 2 and 10, short-wavelength infrared (SWIR) band 6, middle-wavelength infrared (MWIR) band 3, and long-wavelength infrared (LWIR) bands 4 and 5. Two types of data with different transmission rates are available: high-resolution picture transmission (HRPT) with 10 bands and global delayed picture transmission (GDPT) with 4 bands. Over 20 years of operation, the VIRR has captured enormous amounts of data, which is valuable for global observation and disaster preparedness
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