Initial studies of the directional reflectance changes in pressed and sintered PTFE diffusers following exposure to contamination and ionizing radiation

Abstract

Changes in the directional reflectance properties of pressed and sintered polytetrafluoroethylene (PTFE) diffusers induced by exposure to vacuum ultraviolet (VUV) irradiation before and after controlled contamination with Pennzane are presented in this paper. A set of 99% reflective, white, optical grade diffuse calibration standards were irradiated with a VUV source positioned at 60° to the diffuser normal. The bidirectional reflectance distribution functions before and after contamination and VUV irradiation were measured and compared at a number of scatter geometries and wavelengths in the UV, VIS and IR spectral ranges. The 8° directional hemispherical reflectance’s were also measured and compared from 200 nm to 2500 nm. Our results indicate a measureable impact of VUV irradiation on pressed and sintered PTFE diffusers as manifested by a directional dependent change in their reflectance. Such an effect needs to be considered in the on-orbit deployment of PTFE diffusers.

Spectral Dependent Degradation of the Solar Diffuser on Suomi-NPP VIIRS Due to Surface Roughness-Induced Rayleigh Scattering

“…The SD is made of Spectralon TM (Fluorocarbon-based polymer) and designed to have the property of Lambertian reflectance (see Appendix A.1.). The spectral properties of SD reflectance inevitably degraded due to UV exposure and particle radiations in space [13][14][15][16][17][18][19][20], which are summarized in Appendixes A.2. and A.3.…”

“…Extensive experiments of particle and UV irradiation on SD material were performed [13][14][15][16][17][18][19][20] to study changes in directional-hemispheric spectral reflectance, the bidirectional spectral reflectance factor and the polarization properties of diffuser material after the radiation exposure. In early experiment of [13], optical-grade Spectralon material underwent proton exposure and UV-irradiation.…”

“…Other experiments [14][15][16][17][18][19] also show similar magnitude of reflectance degradation after exposure to UV radiation. Recent experiment in [20] studied changes in the reflectance properties of pressed and sintered PTFE diffusers induced by exposure to VUV irradiation before and after controlled contamination with Pennzane. Their results show that the 8˝directional hemispherical reflectance of vacuum-baked sample degraded about 70% after 40 h of VUV exposure.…”

Radiation Budget Instrument On-Board Solar Calibration Target-Concept and Operation

“…The first sintered PTFE diffuser will be used bi-weekly, the second quarterly, and the third one, also known as the reference diffuser yearly. The three diffusers monitored at different time intervals one to detect and correct for reflectance changes [4], [5]. The suite of stable on-orbit references will ensure that calibration stability is maintained over the RBI sensor lifetime.…”

The 12th international conference on new developments and applications in optical radiometry (NEWRAD 2014)

“…Chunnilall et al [3] developed instrumentation for calibration of the QKD receiver and QKD transmitter and demonstrate the ability to provide traceable measurements for the new quantum optical technologies.Solar radiometry and Earth Observation have traditionally been central topics in the NEWRAD conferences. This issue includes five articles on such applications [4][5][6][7][8]. A cryogenic solar absolute radiometer aims to reduce the uncertainty of terrestrially measured direct solar irradiance by more than one order of magnitude.…”