Only valid for 300-800nm (range of downwelling radiometer)
Raw hyperspectral exposures are calibrated for images in full sunlight. Other times and cloudy days are not well-tested yet.
Zenith angles used in the calibration data are: 42.3, 47.6, 53.0, 58.4, 64.0, 75.1, 80.7, 86.5
The closer the raw data is to these angles the better the result
The calibration needs improvement to obtain accurate absolute reflectances. Environmental conditions (such as shade and specular reflection) and irregular calibration of known targets (such as tilted surfaces and field-based calibration) can bias retrieved reflectances by an unknown factor. However, the scale bias factors out of indices created as ratios of reflectances, e.g., (A-B) / (A+B).