The cosine error of a class of in situ hyperspectral irradiance sensors largely applied for ocean color investigations, has been characterized for both in-air and in-water measurements. Results for in-air measurements indicate a slight wavelength dependence of the cosine error with differences up to 2% in the 412-865 nm spectral interval at 65 degrees zenith angle (i.e., the angle of incidence of the incoming flux with respect to the normal axis of the irradiance collector). However, the dependence of the cosine error with the zenith angle is generally quite marked and significantly varies from radiometer to radiometer with values ranging from -5% up to +7% at 65 degrees. Additionally, aside the expected increase of the cosine error with the angle of incidence, in-air measurements generally indicate an irregular deviation from the ideal cosine response near the normal angle of incidence. A more pronounced increase of the cosine error is generally observed when radiometers are operated in-water with respect to in-air.

MEKAOUI Sabri;  ZIBORDI Giuseppe; 

2013-06-27

IOP PUBLISHING LTD

JRC77973

0026-1394,   

http://iopscience.iop.org/0026-1394/50/3/187,    jsessionid=ED72E8D522B2F2B2579EF2AD5C58C9FE.c2,    https://publications.jrc.ec.europa.eu/repository/handle/JRC77973,   

10.1088/0026-1394/50/3/187,