Application to the VIS/IR Imaging System of ITER Cameras in ITER: 18 views in the VIS and IR range needed to cover 80 % of the inner vacuum chamber of ITER Mandatory diagnostic for the ITER machine protection Used for monitoring in real time the Plasma Facing Components (PFCs) heating (200°C-3600°C) Strong issues to get accurate surface temperature measurements of PFCs in highly reflective environment Measured flux Issues in future metallic tokamak (ITER) Low and changing emissivities  (λ, T, surface properties) Multiple reflections adding parasitic signals = Target camera ελ’Lλ(Tsurf) (1-ελ’)Lλ(To) Thermal Emission Reflection To (Blackbody) Cause major errors in the surface temperature measurement Tsurf A realistic photonic simulation necessary to quantify accurately the contribution of the reflected flux on the surface temperature measurement 20th ITPA Topical Group Meeting on Diagnostics 25th May, 2011