&lt;title&gt;Alignment and polarization sensitivity study for the Cassini composite infrared spectrometer (CIRS) far-infrared (FIR) interferometer&lt;/title&gt;

The Cassini spacecraft orbiting Saturn carries the composite infrared spectrometer (CIRS) designed to study thermal emission from Saturn and its rings and moons. CIRS, a Fourier transform spectrometer, is an indispensable part of the payload providing unique measurements and important synergies with the other instruments. It takes full advantage of Cassini's 13-year-long mission and surpasses the capabilities of previous spectrometers on Voyager 1 and 2. The instrument, consisting of two interferometers sharing a telescope and a scan mechanism, covers over a factor of 100 in wavelength in the mid and far infrared. It is used to study temperature, composition, structure, and dynamics of the atmospheres of Jupiter, Saturn, and Titan, the rings of Saturn, and surfaces of the icy moons. CIRS has returned a large volume of scientific results, the culmination of over 30 years of instrument development, operation, data calibration, and analysis. As Cassini and CIRS reach the end of their mission in 2017, we expect that archived spectra will be used by scientists for many years to come.

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“…The far-infrared optics have been described by Crooke and Hagopian [18,19]. Optical design of the far-infrared portion of CIRS is shown in Fig.…”

Section: Figmentioning

confidence: 99%

Composite infrared spectrometer (CIRS) on Cassini

et al. 2017

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“…Nevertheless, the substrate results in increased transmission losses when compared to a free-standing wire grid. Like the free-standing wire grids, the photolithographic polarizers have been cooled to cryogenic temperatures [9], and they have already been used in previous spaceborne instruments [3], [5].…”

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confidence: 99%

Transmission and Reflection Characterization of Polarizing Beam Splitters at Submillimeter Wavelengths

Jacob

Kotiranta

Murk

2019

IEEE Trans. THz Sci. Technol.

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This paper presents a comparison of the transmission and reflection performance of different free-standing wire grids and photolithographic polarizers. This study has been carried out in the frame of the development work of the submillimeter-wave instrument (SWI) as part of the JUpiter and ICy moons Explorer mission of the European Space Agency. SWI is a passive heterodyne radiometer that is operating in the frequency bands from 530 to 625 GHz and from 1080 to 1275 GHz. The optical coupling network of SWI includes a polarizing beam splitter to separate the signal into the two channels. Simulations of the transmittance and reflectance in co-polarization and in cross-polarization have been performed at different incidence angles and polarizations to support the selection of the optimum beam splitter for SWI. The nominal and actual design parameters of the investigated polarizing beam splitters, measured with a confocal laser microscope, have been considered in the simulations. Measurements of the transmission and reflection losses in co-and in cross-polarization have been performed at 636.5 GHz to validate these numerical calculations. The very low losses of the beam splitters in co-polarization were accurately measured by means of a free-space cavity resonator setup. These measurements are in very good agreement with the simulations and radiometric measurements of the transmission loss which were performed with a breadboard model of the SWI receiver unit at 590.0 GHz. The lowest transmission losses among the studied beam splitters are observed for a free-standing wire grid with a single plane of gold-coated wires. The highest reflectance in copolarization and the lowest levels of cross-polarization leakage are determined for the photolithographic polarizers. Index Terms-Electromagnetic transmission, electromagnetic reflection, submillimeter-wave measurements, submillimeter-wave components, polarizing beam splitters (PBS), wire grids. I. INTRODUCTION B ROADBAND and low-loss polarizing components operating at millimetre and submillimeter wavelengths are established in a variety of applications. In quasi-optical networks, polarizers are used as variable attenuators and reflectors, filters, and coupling elements [1]-[3]. Polarizing beam splitters (PBS) with a high polarization selectivity are frequently applied as Manuscript

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