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Atmospheric Channel
Published in Hamid Hemmati, Near-Earth Laser Communications, 2020
Concerning aerosol concentration, LOWTRAN provides a number of models apt to properly describe the nature of the aerosols (e.g., rural, urban, maritime, desert, etc.) and their distribution within the atmospheric profile (i.e., boundary layer, troposphere, stratosphere, etc.). Other meteorological conditions affecting the beam propagation (such as fog, clouds, cirrus clouds, and rain) can also be simulated. As an improvement to LOWTRAN, the simulation program MODTRAN (acronym for MODerate atmospheric TRANsmission) [33] was developed, allowing a narrower spectral resolution up to 0.2 cm−1 in its more recent version MODTRAN 6 [34]. However, the requirement to properly model the propagation of laser beam with a narrow linewidth in the sub-angstrom range has inspired the development of software programs such as FASCODE (acronym for FASt atmospheric Signature CODE) [35] which can compute the atmospheric transmittance with line-by-line resolution. Concerning the remainder of this section, we will present a number of simulation results of atmospheric transmittance (and sky radiance) obtained using MODTRAN software program.
Radiometric Conversion and Data Correction
Published in Shen-En Qian, Hyperspectral Satellites and System Design, 2020
The atmospheric radiative transfer code, MODTRAN 4.2, was used to perform the radiative transfer calculations. From the point of view of the characterization of the hyperspectral sensor to some specific level of accuracy, the radiative transfer reference data must be accurate to a commensurate level. From the pragmatic view of eliminating the spikes in the derived reflectance data, it is only necessary that the wavelength calibration of the measured image data matches the atmospheric reference data. In this method, the absorption features in the measured radiance are compared with those in a modeled at-sensor radiance calculated using MODTRAN 4.2.
Assessing Landsat-8 atmospheric correction schemes in low to moderate turbidity waters from a global perspective
Published in International Journal of Digital Earth, 2023
Nanyang Yan, Zhen Sun, Wei Huang, Zhao Jun, Shaojie Sun
Image correction for atmospheric effects (iCOR) offers the ability of AC over inland, coastal, and transitional waters (Guanter, Gonzalez-Sanpedro, and Moreno 2007). It first identifies land and water pixels using a band threshold approach. Scene-specific aerosol optical thickness (AOT) is obtained following the SCAPE-M algorithm (Guanter, Gonzalez-Sanpedro, and Moreno 2007). An adjacency correction can optionally be applied using the SIMilarity Environmental Correction (SIMEC) approach (Sterckx et al. 2015). A MODerate resolution atmospheric TRANsmission (MODTRAN 5) look-up table is built (Berk et al. 2006), which requires ancillary information as inputs, such as solar and viewing angles and digital elevation model. If the above steps fail, Rayleigh scattering correction is automatically initiated with a default AOT of 0.1. Proper terrestrial pixel distributions are needed to obtain the best results. iCOR can be implemented as a plugin in the SNAP software (V6.0). In this study, the default settings were applied and the adjacency correction was implemented.
Uncertainty analysis of the flame temperature determination based on atmospheric absorption effect with optical emission spectroscopy
Published in Combustion Science and Technology, 2018
where Iν,trans is the transmitted radiation, and ds is the path length of the atmospheric layer. kν,ext is the extinction coefficient of the atmospheric molecules. The optical depth is a function of the path length and the extinction coefficient, which includes the concentration of atmospheric molecules. In this study, spectral information on atmospheric transmission is obtained from the MODTRAN database and applied to the calculated spectrum (Berk et al., 2005). The MODTRAN software computes line-of-sight atmospheric spectral transmittances and radiances over the ultraviolet through long wavelength infrared spectral regime. The core of the MODTRAN radiation transfer is an atmospheric narrow band model algorithm, and it solves the radiative transfer equation including the effects of molecular and particulate absorption/emission and scattering, surface reflections and emission, solar/lunar illumination, and spherical refraction. We use the atmospheric model of the mid-latitudes in winter and obtain the atmospheric transmission data with varying path length, humidity, and CO2 volume mixing ratio to analyze the effect of atmospheric absorption. In particular, for the fitting of experimental data, atmospheric transmission data with the measurement conditions defined by a path length of 22 m, a temperature of 5°C, a relative humidity of 50%, and a CO2 volume mixing ratio of 360 ppmv are applied.
Modelling full-colour images of Earth: simulation of radiation brightness field of Earth’s atmosphere and underlying surface
Published in Annals of GIS, 2023
Vladimir Khokhlov, Valery Lukin, Sergey Khokhlov
The MODTRAN computer code series is now used worldwide by researchers and scientists in government agencies, commercial organizations and educational institutions to predict and analyse optical measurements through the atmosphere. The code is integrated into many operational and research sensor and data processing systems. They are commonly referred to as atmospheric correction in remotely sensed multispectral and hyperspectral imagery (MSI and HSI). The most advanced version is the MODTRAN6 code (Berk et al. 2014). This code provides a modern modular object-oriented software architecture, including an application programming interface, extended physics functions, a line-by-line algorithm, an additional set of physics tools and new documentation.