Vis-NIR bidirectional reflection spectra of spherical water ice particles for different sizes (2 to 100 µm), temperatures (173 and 223 K) and temporal evolutions

Three types of water ice particles were prepared, having three grain size distributions: 4.5±2.5 µm, 67±31 μm, and between 2 and 100 µm. Reflectance spectra (from 0.4 to 4 µm) of 5mm-deep surfaces of these particles were measured at 173 K, and some at 223 K, under primary vacuum. During time, the particles undergo metamorphism (recristallisation/sintering, change of grains shape and size) and spectra were measured again several hours after the measurement of the fresh samples.