Polarization Characterization of a Multi-Moded Feed Structure

Metadata Updated: February 28, 2019

The  Polarization Characterization of a Multi-Moded Feed Structure projects characterize the polarization response of a multi-moded feed horn as an innovative approach to polarized measurements in the far-infrared.  Multi-moded optics provide a significant increase in instrument sensitivity per detector, but the polarization response of such quasi-optical structures is not well understood. We will measure the co-polar and cross-polar beam patterns of a multi-moded feed horn.A simple, focused investigation will measure the co-polar and cross-polar response of a multi-moded feed. We will fabricate a larger version of a far-IR feed, mount it within the Goddard Electromagnetic Anechoic Chamber (GEMAC), and measure the co-polar and cross-polar response using wire grid polarizers mounted at the source and multi-mode detector.The polarization response of a multi-moded feed is difficult to model.  Geometric optics (ray tracing) yields the response in the high-frequency (short wavelength) limit, but ignores effects of beam diffraction at the edges of the feed. Solution of Maxwell's equations within the feed structure provides an analytic expansion of the response using waveguide theory, but is computationally tractable only in the few-mode (long wavelength) regime.  Astrophysical signals in the far-infrared (e.g. the cosmic microwave background) are bright at  frequencies near 300 GHz (1 mm wavelength), squarely between the two limits.  Diffraction is important at these wavelengths, yet tens to hundreds of electromagnetic modes propagate within the feed structure, making direct calculation extremely difficult. Measurements of a first-generation feed horn demonstrate basic functionalit and provide a simple model to guid future design.  Based on the initial results, we plan to design and test a second-generation feed to maximize throughput while minimizing the cross-polar response.

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Public: This dataset is intended for public access and use. License: U.S. Government Work

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Dates

Metadata Created Date August 1, 2018
Metadata Updated Date February 28, 2019

Metadata Source

Harvested from NASA Data.json

Additional Metadata

Resource Type Dataset
Metadata Created Date August 1, 2018
Metadata Updated Date February 28, 2019
Publisher Space Technology Mission Directorate
Unique Identifier TECHPORT_11954
Maintainer
TECHPORT SUPPORT
Maintainer Email
Public Access Level public
Bureau Code 026:00
Metadata Context https://project-open-data.cio.gov/v1.1/schema/catalog.jsonld
Metadata Catalog ID https://data.nasa.gov/data.json
Schema Version https://project-open-data.cio.gov/v1.1/schema
Catalog Describedby https://project-open-data.cio.gov/v1.1/schema/catalog.json
Harvest Object Id 7558f97d-5cc5-4fba-898e-9f4844f65f4b
Harvest Source Id 39e4ad2a-47ca-4507-8258-852babd0fd99
Harvest Source Title NASA Data.json
Data First Published 2015-09-01
Homepage URL https://techport.nasa.gov/view/11954
License http://www.usa.gov/publicdomain/label/1.0/
Data Last Modified 2018-07-19
Program Code 026:027
Source Datajson Identifier True
Source Hash be80ed84fff12d58790387cfcee60ccbe771f3a8
Source Schema Version 1.1

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