STARR performs directional-hemispherical, specular, and bidirectional reflectance measurements of spectrally neutral, non-fluorescent samples at room temperature. It currently serves as the national reference instrument for directional-hemispherical reflectance measurements. The national reference instrument for specular and bidirectional reflectance measurements is the Robotic Optical Scattering Instrument (ROSI).
STARR uses a lamp-based, quasi-monochromatic system for illumination of the sample and broadband detection for the reflected radiation. Directional-hemispherical measurements are acquired using an integrating sphere and require comparison to a calibrated standard, pressed polytetrafluoroethylene (PTFE). All specular and bidirectional measurements are collected in-plane, meaning the sample normal, illumination axis, and receiver axis are in the same plane.