Atmospheric transmission algorithm for pulsed X-rays from high-altitude nuclear detonations based on scattering correction

In high-altitude nuclear detonations,the proportion of pulsed X-ray energy can exceed 70%,making it a specific monitoring signal for such events.These pulsed X-rays can be captured using a satellite-borne X-ray detector following atmospheric transmission.To quantitatively analyze the effects of different satellite detection altitudes,burst heights,and transmission angles on the physical processes of X-ray transport and energy fluence,we developed an atmospheric transmission algorithm for pulsed X-rays from high-altitude nuclear detonations based on scattering correction.The proposed method is an improvement over the traditional analytical method that only computes direct-transmission X-rays.The traditional analytical method exhibits a maximum relative error of 67.79% compared with the Monte Carlo method.Our improved method reduces this error to within 10% under the same conditions,even reaching 1% in certain scenarios.Moreover,its computation time is 48,000 times faster than that of the Monte Carlo method.These results have important theoretical significance and engineering application value for designing satellite-borne nuclear detonation pulsed X-ray detectors,inverting nuclear detonation source terms,and assessing ionospheric effects.

Design of fiber-optic collector for spectrometer based on curved mirror

To enlarge the detection range of traditional fiber-optic spectrometer,two rotating parabolic mirrors were first used in the design of fiber-optic collector for spectrometer,which can extend the detection range of spectrometer from centimeter-scale to50m,as a super-low altitude remote sensing detector under passive lighting conditions.According to the performance requirements of fiber-spectrometer for optical collector,this study deduced the calculation formulae of design size of parabolic optical collector applied to different sensitivity spectrometers,different detection targets,different detection ranges and different weathers.Based on the calculation results,the model of fiber-optic collector with a diameter of16mm and a height of7.8mm was designed by ZEMAX.And then,TracePro,a light simulation software,was applied to ray tracing.The simulation results of optical radiation magnification agrees well with theoretical value,and the relative error is less than0.78%.This optical collector can effectively extend the detection range of spectrometer and expand its application fields and scopes.Compared with traditional refractive optical collector,it has several advantages of compact structure,low weight and low cost.

Atmosphere Transmission Performance for 0.4 μm～0.8 μm Ray Radiation in Middle Latitude of China

This paper researched on the atmospheric transmission performance of 0.4 μm～0.8 μm ray radiation based on the characteristic of the middle latitude atmosphere in China.By analysis of the characteristic of the actual atmosphere,the absorption of molecular and the scattering of the steam and ozone,as well as the aerosol scattering(big granule scattering) are play a leading role to the 0.4 μm～0.8 μm ray radiation.Then a better atmospheric transmission formula in horizontal path has been deducted.The result of computer simulation indicates that this equation can best calculate the transmission performance of 0.4 μm～0.8 μm visible radiation in the middle latitude area of China.This computing result was applied to the nuclear explosion parameter detection system based on 0.4 μm～0.8 μm visible radiation.Through nuclear explosion simulator to produce ray radiation,the tested result indicates that this method has the better measuring precision than the traditional method with the software of LOWTRAN.The calculation result of this formula not only can apply directly to each kind of optoelectronics detecting system,but also to the optical wireless communication system based on the 0.4 μm～0.8 μm ray radiation.

Terahertz atmospheric transmission measured at the AliCPT site

Cosmic-microwave-background(CMB)B-mode measurements may reveal primordial gravitational waves from the earliest phases of the Big Bang.As the first CMB experiment in the northern hemisphere,the Ali CMB polarization telescope(Ali CPT)will carry out measurements of this kind at Ali(Nagri)in Tibet.It is therefore of particular importance to understand the terahertz atmospheric transmission at this site.Here we report on the measurement results for three consecutive seasons with a Fourier transform spectrometer(FTS)spanning a wide frequency range from 0.75 to 14 THz.The zenith median precipitable-watervapor(PWV)is found to be as low as 1 mm at the Ali CPT site,which appears as good as those CMB B-mode measurement sites in the southern hemisphere such as Chile's Atacama Desert.

Infrared radiation simulation of exhaust system by coupling FVM with narrow band k-distribution

A three-dimensional infrared radiation code for exhaust system was developed by the finite volume method coupled with narrow band k-distribution in non-gray absorbing-emitting media.The final infrared signature had considered the atmosphere effect,and the simulation values were favorably consistent with testing ones.The results indicate that the relative errors considering the effect of atmosphere compared with that of the contrary condition reduce by 31%,it shows that when simulating the infrared radiation of the target which is received by the infrared detectors,even the calculation band is in atmospheric windows 3～5 μm,the effect of atmospheric transmission on infrared signature of the target should not be neglected.