KEYWORDS: Temperature metrology, Monte Carlo methods, Target detection, Infrared radiation, Solar radiation, Computer simulations, Solar radiation models, Error analysis
When the target to be measured temperature is far away, and the prior information of the target such as the emissivity of the detected object can not be known, the traditional infrared single-band temperature measurement method will produce larger temperature measurement error. According to the characteristics of target infrared radiation spectrum, assuming that the target is grey body, this paper uses infrared dual-band temperature measurement algorithm and Monte Carlo method to extract the temperature feature of the object under test. The effectiveness of the algorithm is analyzed. The influence of parameters such as iteration times of the algorithm and the minimum error threshold of dual-band radiation ratio on the accuracy of target temperature inversion is simulated and analyzed. On this basis, the influence of different target emissivity, distance between wavebands and detection distance on target temperature inversion accuracy is analyzed. The results show that the two-band temperature measurement algorithm can extract the target temperature information quickly and accurately under the set parameters, and the temperature inversion error is related to the distance between infrared bands. This provides guidance for improving the accuracy of target temperature measurement in practical measurement.
With the continuous occurrence of aircraft crash, it is very important to realize the detection of aerial targets on the spaced-based platform. Many countries have carried out some researches in this field, but there is still no good conclusion about the methods and systems for aerial target detection. Meanwhile, the actual cost of satellite experiments is very expensive, and it is impractical to test the detection system by launching satellites several times. Therefore, the system simulation model can be used as the basis for the design of detection system. In the simulation process, combined with the optical system parameters and detector indicators, the imaging relationship between the satellite platform, the turntable and the target are calculated, and various imaging modes such as scanning and gazing are obtained according to the specific parameters of the actual application. This simulation mode directly presents the actual satellite motion, camera imaging and target motion state. And such a simulation system greatly shortens the actual design time of the system in engineering applications. It more realistically inverts the actual operating state and can obtain the detection result without the actual satellite launch. And such a simulation system can flexibly change parameters according to the actual conditions, so it can not only be applied to aerial targets detection, but also play an important role in other fields.
Soil moisture (SM) is a key variable in controlling the water, carbon, and energy exchange processes of land atmosphere interface. One of the widely used approaches to retrieve soil moisture is based on satellite remote sensing technology. However, these spatiotemporally continuous soil moisture products retrieved from microwave remote sensing data are not able to meet the accuracy requirement of flood prediction and irrigation management due to the coarse spatial resolution. As one of the relatively new passive microwave products, The Fengyun-3B Microwave Radiation Imager (FY-3B/MWRI) soil moisture product was retrieved from passive microwave brightness temperature data based on the Qp model. However, it has rarely been applied at the catchment and regional scale due to the coarse resolution with 25- km grid. In this study, the Fengyun-3B soil moisture product was downscaled from 25-km to 1-km based on Moderate Resolution Imaging Spectroradiometer (MODIS) data. The downscaling approach uses MODIS land surface temperature (LST) and normalized difference vegetation index (NDVI) to construct soil evaporative efficiency (SEE). The 1-km SM was then estimated based on the difference value of high resolution and average SEE in original FY3B pixel. The downscaling method was applied to every Fengyun-3B pixel in the Naqu area on the Tibetan Plateau to retrieve the downscaled 1-km resolution FY3B soil moisture product. The downscaling results were validated using the in-situ soil moisture from Soil Moisture/ Temperature Monitoring Network on the central Tibetan Plateau (TP-STMNS) in August 2015. The validation results revealed that the downscaling approach showed promising results. We can conclude that the downscaled FY3B SM product better characterize the spatial and temporal continuity and have higher consistency with validation soil moisture data. The approach proposed in this study are applicable to bare surface or sparse vegetation covered land surface.
KEYWORDS: Target detection, Mid-IR, Long wavelength infrared, Infrared radiation, 3D modeling, Optical engineering, Skin, Signal detection, Signal to noise ratio, Infrared detectors
To ensure flight safety of an aerial aircraft and avoid recurrence of aircraft collisions, a method of multi-information fusion is proposed to design the key parameter to realize aircraft target detection on a space-based platform. The key parameters of a detection wave band and spatial resolution using the target-background absolute contrast, target-background relative contrast, and signal-to-clutter ratio were determined. This study also presented the signal-to-interference ratio for analyzing system performance. Key parameters are obtained through the simulation of a specific aircraft. And the simulation results show that the boundary ground sampling distance is 30 and 35 m in the mid- wavelength infrared (MWIR) and long-wavelength infrared (LWIR) bands for most aircraft detection, and the most reasonable detection wavebands is 3.4 to 4.2 μm and 4.35 to 4.5 μm in the MWIR bands, and 9.2 to 9.8 μm in the LWIR bands. We also found that the direction of detection has a great impact on the detection efficiency, especially in MWIR bands.
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