Two potato cultivars, sprayed and nonsprayed with fungicides, were evaluated to determine the association of late blight (caused by Phytophtora infestans) and radiometric leaf reflectance to disease development. Spectral radiance measurements were taken with Cl MEL CE3132 luminancemeter in the visible (450 nm, 550 nm and 650 nm) and near-infrared (850 nm) range of the electromagnetic spectrum. The measurements were taken at two view zenithal angles.ó.> 0° (at nadir) and o.> 50°. Six vegetative indices based on these measurements were used to detect differences between sprayed and nonsprayed plants. Vegetation indices based on the reflectance measurement enable to distinguish infected potato plants from noninfected plants. Among the vegetation indices used in this studies the best indicators of disease were NlR/RED and ELA!. Results of our study show that for Mila cultivar oblique viewing may be more effective then nadir viewing (perpendicular to the ground surface) for distinguishing between plants infested at different degree.

This paper addresses the influence of land topography and cover on 3D radiative effects under cloudless skies in the Hornsund area, Spitsbergen, Svalbard. The authors used Monte Carlo simulations of solar radiation transfer over a heterogeneous surface to study the impact of a non-uniform surface on: (1) the spatial distribution of irradiance transmittance at the fjord surface under cloudless skies; (2) the spectral shortwave aerosol radiative forcing at the fjord surface; (3) normalized nadir radiance at the Top Of the Atmosphere (TOA) over the fjord. The modelled transmittances and radiances over the fjord are compared to the transmittances and radiances over the open ocean under the same conditions. The dependence of the 3D radiative effects on aerosol optical thickness, aerosol type, surface albedo distribution, solar azimuth and zenith angle and spectral channel is discussed. The analysis was done for channels 3 (459-479 nm) and 2 (841-876 nm) of the MODIS radiometer. In the simulations a flat water surface was assumed. The study shows that snow-covered land surrounding the fjord strongly modifies the radiation environment over the fjord surface. The enhancement of the mean irradiance transmittance over the fjord with respect to the open ocean is up to 0.06 for channel 3. The enhancement exceeds 0.11 in the vicinity of sunlit cliffs. The influence of the snow-covered land on the TOA radiance over the fjord in channel 3 is comparable to the impact of an increase in aerosol optical thickness of over 100%, and in lateral fjords of up to several hundred percent. The increase in TOA radiance is wavelength dependent. These effects may affect retrievals of aerosol optical thickness.

Lasers emitting mid-infrared (MIR) beams have become indispensable for spectroscopy, free space communication or remote security measures. To the one of the most promising families of the lasers suitable for these applications certainly belongs a group of the Quantum Cascade Lasers (QCL). However, among the conditions they must satisfy there is a high enough radiance of the beam they emit. Radiance depends in a complicated way on the laser output power and optical quality of the laser beam. This paper has been devoted to a description and a short analysis of the factors that decide about radiance of so far developed QCLs. Literature concerning both single devices and QCL arrays operating in beam combining systems have been examined and results described. The survey may be useful for estimation of how far the QCLs have come of age.