FengYun-4A (FY-4A) is the first three-axis stabilized geostationary meteorological satellite in China, which was launched in the early morning of 11 Dec., 2016. Advanced Geosynchronous Radiation Imager (AGRI) is one of the four payloads onboard FY-4A, and acquired the first image on 20 Feb., 2017. FY-4A AGRI contains 14 spectral bands, in which 6 bands are in reflective solar region, with the nominal wavelengths at 0.47, 0.65, 0.825, 1.375, 1.61 and 2.25μm. The spatial resolution is 0.5 km for 0.65 μm band, 2 km for the shortwave infrared bands and 1 km for others. AGRI is designed with a solar diffuser, however it revealed the insufficient capacity for in-flight calibration mainly due to the partial aperture effect. The first vicarious calibration field campaign was conducted at the Dunhuang site of China Radiometric Calibration Site (CRCS) in Apr. 2017. It revealed the large bias of the AGRI data calibrated using the prelaunch calibration parameters, mostly underestimated. Using multiple land sites in Asia and Oceania, the calibration correction factors were derived combined with the CRCS data. The sensor's on-orbit radiometric response variation and observation bias against the simulated radiation were also monitored. It revealed that the bands at 0.65 μm was most stable, while 0.47 μm band showed the large degradation with an annual rate nearly 17%. In this paper, the calibration status of the FY-4A AGRI solar bands was presented.
Millimeter wave imaging technology provides a new detection method for security, fast and
safe. But the wave of the images is its own shortcomings, such as noise and low sensitivity.
Systems used for security, since only the corresponding specific objects to retain the information,
and other information missing, so the actual image is difficult to locate in the millimeter wave .
Image fusion approach can be used to effectively solve this problem. People usually use visible
and millimeter-wave image fusion. The use of visible image contains the visual information. The
fused image can be more convenient site for the detection of concealed weapons and to provide
accurate positioning. The integration of information from different detectors, and there are
different between the two levels of signal to noise ratio and pixel resolution, so traditional
pixel-level fusion methods often cannot satisfy the fusion. Many experts and scholars apply
wavelet transform approach to deal with some remote sensing image fusion, and the performance
has been greatly improved. Due to these wavelet transform algorithm with complexity and large
amount of computation, many algorithms are still in research stage.
In order to improve the fusion performance and gain the real-time image fusion, an Integer
Wavelet Transform CDF97 based with regional energy enhancement fusion algorithm is proposed
in this paper. First, this paper studies of choice of wavelet operator. The paper invites several
characteristics to evaluate the performance of wavelet operator used in image fusion. Results show
that CDF97 wavelet fusion performance is better than traditional wavelet wavelets such as db
wavelet, the vanishing moment longer the better. CDF97 wavelet has good energy concentration
characteristic. The low frequency region of the transformed image contains almost the whole
The target in millimeter wave image often has the low-pass characteristics and with a higher
energy compare to the ambient region. Based on this assumption, a new fusion rule is proposed here. Firstly, get the low-frequency part of the selection matrix according to the comparison
regional low-frequency energy matrix of the two images. Then, taking into account the
consistency and continuity of low-frequency detail, high frequency and low frequency selection
matrix can be the same. And this can ensure a better fusion of the edge of the image
characteristics. Simulation results show that this algorithm's performance is much better compared
to traditional energy-weighted and average method, though less quantitative comparison point
compared to the region based method, yet, the difference is small according to the visible
This algorithm is tested in the self-developed image processing platform based on DM642. By
using the optimization strategy, the speed of 256 × 256 dual-channel image fusion can be more
than 28 F/S. Therefore, the proposed fusion algorithm can meet the system performance and
This article from two factors including the signal to noise ratio (SNR) and image registration accuracy,
discussed the situation on 3.5um band on Multi-Channel Scanning Imagery Radiometer of
geosychronous orbit meteorological satellite FY-4 used to apply sub-pixel detection technology to
enhance image spatial resolution, thereby improve accuracy of fire position and calculation of fire area
on the earth surface.