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.
Privacy Notice Accessibility Notice