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NPL Gonio RAdiometric Spectrometer System (GRASS) BRDF system

The FSF houses and maintains the NPL Gonio RAdiometric Spectrometer System (GRASS) BRDF system. GRASS has been designed to measure the Earth's reflected sunlight over half a hemisphere, at 30-degree intervals i.e. 0°, 30°, 60°, 90°, 120°, 150°, 180°, on a series of seven arms. The positions of the entrance optics on the arms are also designed to be moveable so that effectively any five-zenith angles (up to 60°), can be chosen to be captured during each measurement sequence. This allows detailed studies of particular BRDF characteristics, e.g. the specular peak.

The GRASS system comes in 3 large (62x67x114cm) cases, and requies significant logistical planning and training for use. Please see the paper below (Pegrum-Browning, Fox, Milton (2008)) for further insight into the GRASS system, and get in contact with us if you would like to discuss the GRASS system further.




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