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Jessica Patel

Publications and source records attributed to Jessica Patel.

4 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2023

New Mie Scattering Diffuse Targets Development and Characterization

Earth science remote sensing observations require the detection and measurement of light originating from bright targets, such as clouds, and darker targets, such as an open ocean. This requirement drives the need to design, develop, and characterize improved calibration targets in support of current and future NASA instruments. New diffuse targets to be used as spectral albedo calibration standards were developed and characterized. The new targets based on fused silica or/and pressed and sintered Polytetrafluoroethylene (PTFE) were developed to be Earth scene specific. The various reflectance levels are achieved by modifying the material parameters, thickness, and surface finish. The new targets were characterized in laboratory and simulated space environments. We acquired high accuracy reflectance and transmittance data using a precision optical scatterometer and spectrophotometer located in the NASA Goddard Space Flight Center (GSFC) Diffuser Calibration Lab. The Total hemispherical reflectance (THR) and Bidirectional Reflectance Distribution Function (BRDF) were measured over the range of solar incident and scattered elevation and azimuthal angles typically realized on orbit by remote sensing instruments. We intend to space certify the new calibration targets after concluding on-orbit testing on the International Space Stations (ISS) scheduled for the second half of 2023.

Georgi Georgiev↗
NASA NTRSDate not supplied

Black-silicon as a Wideband Infrared Absorber for the Space Instruments: Fabrication, Modeling, and Characterization

The uniform black silicon (BSI) cryogenically etched has been demonstrated as a superior absorber in par with other ultra-absorbers such as carbon nano tubes in the visible and near-infrared spectrum. In this work, we discuss the fabrication, modeling, and characterization of the BSI aiming at the 2.5-5 microns range. We investigated a series of cryogenic parameters such as temperature, pressure, oxygen flowrate, power, and etching duration and fabricated a series of uniformly etched wafers. Additionally, we established at hree-dimensional mathematical model of a unit cell and manipulated the silicon needle geometry and shape. Our preliminary fabrication results show silicon needles of 8 micron height have five orders of magnitude specular reflectance in the infrared region. The modeling efforts how longer pillar heights could be better absorbers as the wavelength increases.

Wideband absorber↗