Table 1: Five skin parameters used in the retrieval algorithm. The range of each parameter is selected from the literature. The retrieval parameters are bounded to these limits.

Skin parameter Symbol Range

Melanin concentration 1.3 to 45%
Epidermis thickness 0.01–0.15 mm
Volume fraction of haemoglobin 0.2–7%
Oxygenated haemoglobin 25–90%
Dermis thickness 0.6–3 mm