Reference Panel

Field reference panels are highly reflective surfaces used to approximate the amount of incoming radiation from instruments with a narrow field of view [FOV] (generally less than hemispherical, but in the case of most of the instruments used by SNRS, the instruments have a 1-15^o FOV.)  The reference panels that SNRS owns are either coated with Spectraflect© (painted Barium Sulfate (BaSO₄)) or constructed of  Spectralon© (molded sintered,  pressed, powdered polytetraflourethylene) sections made by Labsphere.

Reference panels, although highly reflective, are non-Lambertian surfaces. However, they can be characterized to approximate Lambertian surfaces (see Jackson et al., Walter-Shea et al., and Walter-Shea and Biehl).

Ideally the response over the target and over the reference panel should be collected simultaneously with the same instrument so that the illumination conditions and instrument characteristics are identical. If two cross-calibrated instruments are available, measures over the target and reference can be made simultaneously. If only one instrument is available, measures over the reference panel must be made prior to and periodically after target reflected radiation measurements are made. The instrument output over the reference panel must be approximated between the times of panel measurements. Therefore, it is important that illumination conditions do not vary (i.e., due to clouds or aerosols) between the times of reference measurements.