We determine the backscatter reflectance (more properly the bidirectional reflectance distribution function at a 45 degrees angle of incidence and observation) for circularly polarized radiation of lambda = 10.6 microm for 120-grit aluminum oxide sandcloth (1.5 x 10(-2) sr(-1)) and 400-grit silicon carbide sandpaper (1.1 x 10(-2) sr(-1)) with respect to sublimed flowers of sulfur (1.8 x 10(-1) sr(-1)). The effect of range and the atmospheric effect of turbulence-induced beam wander are discussed for both rotating disks and linearly translated belts. The advantages of large slowly rotating disks for field calibrations are presented.