First, a brief introductory review of previous works on atmospheric correction of satellite imagery over lands was given. Then we presented the theoretical basis of the atmospheric correction algorithm which removes both atmospheric scattering and adjacent effects from the satellite image data with a fine ground resolution. We proposed a simple algorithm for estimating aerosol optical thickness from satellite image data by using dark target pixels and applied it to Landsat TM and ADEOS AVNIR data. As for the algorithm validation, several simultaneous ground and sky measurements data were used. We found that the satisfactory results were obtained in the cases of sub-scene imagery, whereas the agreement was not so good in the full-scene case due to local aerosol's spatial variation.
ADEOS/POLDER (POLarization and Directionality of the Earth's Reflectance) provides polarization of solar radiation reflected by the earth atmosphere-surface system in the visible and near-infrared wavelengths. This work examines a role of polarization information for extraction of optical properties of atmospheric aerosols using the POLDER data.
An analytic model for the radiance applicable to the remote sensing of mountainous terrain is described. This radiance model includes the radiation arising from adjacent terrain outside the instantaneous field of view (IFOV) of the sensor. The atmosphere is treated as the optically thin, horizontally uniform layer bounded by non-homogeneous Lambertian surface. The results derived from the radiance model show that the component of the irradiance impinging on the target due to multiple reflections by adjacent terrain is of no significance except in regions covered with high reflectance materials. It is also shown that the component of the uniform sky irradiance is of no significance exept in very poorly illuminated regions. Furthermore, the correction algorithm for removing atmospheric and topographic effects from high-resolution satellite images is formulated, and the image correction for the Landsat TM image is performed.
An influence due to non-spherical oceanic aerosol particles containing bubbles on estimation of the top of the atmosphere(ToA) radiance is clarified together with an influence due to relative humidity(RH). It is found that the difference of ToA radiance between the phase function of Maritime and Henyey-Greenstein with the same size distribution and refractive index is 0.5% for RH of 76% while that for RH of 99% is 1.3%. It is also found that the influences due to bubbles in oceanic aerosol particles and due to non-spherical parameter on ToA radiance are within arange of 0.3%. Meanwhile, influence due to RH on ToA radiance ranges from0.3 to 0.6%when the RH is changed from76% to 99%.
The difficulties of calculating the underwater light fields differ from those of the atmospheric radiative transfer computation due to the large difference of the refractive index at the interface between air and water (sea surface), the existence of sea surface wave, extreme forward peak of the scattering phase function by large suspended particles in water and so on, so that it is not simply applicable numerical algorithms used in the atmospheric radiative transfer problems. Because of these reasons, the developments of the models of underwater light fields have been carried out almost independently apart from the atmospheric radiative transfer studies. This article reviews the historically important milestone underwater light field models as well as the latest development of irradiance two flow model. Further, we briefly introduce the direct solution numerical algorithms of radiative transfer in the sea, which became popular in marine optics as the result of the development of computer technology, i.e. Monte Carlo and Quad Averaging methods.
Implications of radiative transfer of vegetation in visible and near infrared wavelength regions in remote sensing of eco-physiological plant variables are investigated. Comparative analysis of canopy reflectance models is conducted for correction and normalization of directional effects in remote sensing, based on directional measurements over rice canopies. It is also shown promising to assimilate the remotely sensed information on radiation absorptance of a canopy into radiation-based growth model.
Our solar system consists of the Sun, nine planets, their satellites, and many small bodies including asteroid and comets. Asteroids and comets are believed to be fossils, which retain the records of planet-forming age fairly well. In order to investigate physical properties of the surface layers of such small bodies, a large number of ground-based observations and laboratory measurements of terrestrial rocks and meteorites have been performed. It is demonstrated from those works that most atmosphereless bodies in the solar system are covered with regolith layers, which were generated by impacts of meteorites. Understanding the light scattering process by such regolith surface is an important subject to estimate the composition and structure. However, it is not established how the scattering properties of an isolated particle are related to the average properties of an ensemble of similar particles in a close-packed powder like regolith. In this paper, we summarize the light scattering properties of small bodies in the solar system by referring to previous works and our laboratory analogue experiments.
The optical properties of snow and ice surfaces at the visible and near infrared wavelengths are accounted by a radiative transfer theory in the atmosphere-snow/ice system. In those optical parameters, the important factors as albedo and BRDF (Bidirectional Reflectance Distribution Function) can be estimated by the radiative interaction between the atmosphere and snow/ice, in which light scattering and absorption are theoretically calculated. These theoretical studies began with the modelings of spectral snow albedo in 1950's, and progressed to the operational stage in 1980's and to the modeling of BRDF in 1990's. On the other hand, the observational studies have advanced from the spectrally integrated measurements to the spectral measurements of snow/ice surfaces. These observational results have contributed to the modelings of albedo and BRDF. The radiative transfer theory in the atmosphere-snow/ice system is also applied to the remote sensing of snow and ice surfaces such as the retrievals of snow grain size and snow impurities. Since the influence of global warming is expected to appear significantly in the cryosphere, the remote sensing of snow/ice physical parameters is effective to monitor the global warming. For that purpose, it is necessary to develop the accurate BRDF model for various snow/ice conditions and to validate it with the measurements.
In the first stage of remote sensing, it was enough that an image showed some distribution. As the technique improves high quality data have become required in order to discuss quantitatively on the change of the Earth environments, Global Warming and so on. Therefore the calibration of the radiometers on satellites becomes more important. Here is described our experience of the preflight and on-board calibration of JERS-1 OPS and Terra ASTER and that of the preflight cross-calibration of Terra and ADEOS.
The Remote Sensing Group at the University of Arizona has been successfully using vicarious calibration techniques since the mid-1980s to calibrate both airborne and satellite-based imaging spectroradiometers using vicarious techniques. These approaches use ground-based measurements of atmospheric and surface properties of a selected test site as input to a radiative transfer code to predict at-sensor radiances at 1-nm intervals from 350-2500 nm for a given sensor overpass. Past work has focused on sensors with view angles less than 30 degrees from nadir but recently-developed sensors use much larger view angles and these sensors will still benefit from vicarious calibrations. However, calibrations at such angles require more accurate atmospheric and surface characterizations. This paper examines the sensitivity of vicarious calibrations at large view angles to uncertainties in the atmospheric characterization and surface bi-directional reflectance. The results show that the inclusion of surface BRDF effects are critical to ensuring accurate results. Furthermore, the uncertainty in the vicarious calibration of a large view angle sensor will be of the same level as or less than that of the near-nadir case when aerosol optical thickness is less than 0.10, the aerosols have low imaginary index, and the solar zenith angle is less than 50 degrees. From the results of this study it is found that currently-used test sites are adequate for use in the vicarious calibration of large view-angle sensors and should give reflectance-based results with uncertainties less than 5%.