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Proceedings Paper

Method to model the cross-polarization of millimeter-wave telescopes using a commercial optical software package
Author(s): Luca Olmi; Daniel J. Hoppe
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Paper Abstract

We discuss the conceptual and practical guidelines of a method to calculate the cross-polarization of a telescope, including its relay optics, using a commercial optical design software, without the need to use complex, slow and expensive Physical Optics programs. These effects are usually negligible at visible and infrared wavelengths but may be of considerable importance at radio wavelengths. Offset reflector antenna configurations, common in the telecommunication industry, and antenna relay optics consisting of offset mirrors, common in millimeter and submillimeter-wave telescopes, result in an increased contribution to the cross-polarization. Polarization measurements are also becoming very important in Radio Astronomy. In fact, dust emission polarimetry and the study of linearly polarized, nonmasing, rotational lines (e.g., CO) with submm telescopes are both powerful diagnostic of magnetic fields in molecular clouds. However, the low average source polarization requires a careful optimization of the optical design to keep any instrumental polarization contribution from both telescope and relay optics as low as possible in astronomical polarimetry experiments. Likewise, in telecommunications applications polarization separation can be used to effectively double the available bandwidth provided the isolation between the two orthogonal polarization states is sufficient.

Paper Details

Date Published: 14 February 2003
PDF: 12 pages
Proc. SPIE 4843, Polarimetry in Astronomy, (14 February 2003); doi: 10.1117/12.458234
Show Author Affiliations
Luca Olmi, Univ. of Puerto Rico (United States)
Istituto di Radio Astronomia (Italy)
Daniel J. Hoppe, Jet Propulsion Lab. (United States)

Published in SPIE Proceedings Vol. 4843:
Polarimetry in Astronomy
Silvano Fineschi, Editor(s)

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