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Abstract

Measuring solar-induced chlorophyll fluorescence from smallsized Unmanned Aircraft Systems (UAS) can potentially fill the scaling gap between ground-based and airborne/spaceborne observations. These measurements require well calibrated, high-spectral resolution spectroradiometers and precise measurements of vegetation radiance and incoming solar irradiance. Here we present a system equipped with a spectroradiometer with a split optical path that measures incoming irradiance through a cosine corrector/diffuser. The objectives of this study are to characterise cosine corrected solar irradiance measurements with regard to sensor homogeneity and possible offset from an ideal cosine response. We further suggest a methodology to calculate a corrected zenith angle that accounts for changing sensor orientation due to pitch, roll and heading of the UAS platform during flight. We found that the cosine corrector is sufficiently homogeneous, thus measurements are independent of UAS heading. The response follows the cosine law for zenith angles, however, the sensor significantly underestimated irradiance for zenith angles >10◦ , with overall cosine errors ranging from 0.991 to 1.229. Yet, typical in-flight platform pitch and roll angles produce a zenith angle offset of up to 6 ◦ in low wind conditions. Cosine sensor measurements corrected for the zenith angle offset and the cosine error resulted in a 1.7 % change in irradiance.

Item Type:	Conference Publication
Authors/Creators:	Bendig, J and Gautam, D and Malenovsky, Z and Lucieer, A
Keywords:	pectroradiometer, solar-induced chloro- phyll fluorescence, unmanned aircraft system, sun zenith an- gle, irradiance cosine corrector
Journal or Publication Title:	Proceedings of the 2018 IEEE International Symposium Geoscience and Remote Sensing
Publisher:	Institute of Electrical and Electronics Engineers
Copyright Information:	Copyright 2018 IEEE
Related URLs:	Google Scholar: Gautam, D Google Scholar: Malenovsky, Z UTAS Profile: Malenovsky, Z Google Scholar: Lucieer, A UTAS Profile: Lucieer, A
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