title: Creation and Validation of Sintered PTFE BRDF Targets & Standards.
abstract: Sintered polytetrafluoroethylene (PTFE) is an extremely stable, near-perfect Lambertian reflecting diffuser and calibration standard material that has been used by national labs, space, aerospace and commercial sectors for over two decades. New uncertainty targets of 2 % on-orbit absolute validation in the Earth Observing Systems community have challenged the industry to improve is characterization and knowledge of almost every aspect of radiometric performance (space and ground). Assuming "near perfect" reflectance for angular dependent measurements is no longer going to suffice for many program needs. The total hemispherical spectral reflectance provides a good mark of general performance; but, without the angular characterization of bidirectional reflectance distribution function (BRDF) measurements, critical data is missing from many applications and uncertainty budgets. Therefore, traceable BRDF measurement capability is needed to characterize sintered PTFE's angular response and provide a full uncertainty profile to users. This paper presents preliminary comparison measurements of the BRDF of sintered PTFE from several laboratories to better quantify the BRDF of sintered PTFE, assess the BRDF measurement comparability between laboratories, and improve estimates of measurement uncertainties under laboratory conditions.
authors.affiliation: Labsphere, Inc., North Sutton, NH USA.
authors.forename: Christopher
authors.initials: C
authors.lastname: Durell
authors.affiliation: Labsphere, Inc., North Sutton, NH USA.
authors.forename: Dan
authors.initials: D
authors.lastname: Scharpf
authors.affiliation: Labsphere, Inc., North Sutton, NH USA.
authors.forename: Greg
authors.initials: G
authors.lastname: McKee
authors.affiliation: Labsphere, Inc., North Sutton, NH USA.
authors.forename: Michelle
authors.initials: M
authors.lastname: L'Heureux
authors.affiliation: NASA Goddard Space Flight Center, Greenbelt, MD USA.
authors.forename: Georgi
authors.initials: G
authors.lastname: Georgiev
authors.affiliation: CNAM LNE, St. Denis, FRANCE.
authors.forename: Gael
authors.initials: G
authors.lastname: Obein
authors.affiliation: NIST, Gaithersburg, MD USA.
authors.forename: Catherine
authors.initials: C
authors.lastname: Cooksey
keywords: BRF; Bi-Directional Reflectance Distribution Function; absolute calibration; ground truth; lambertian; reflectance standard; reflectance target; sintered PTFE BRDF; vicarious calibration