Limits due to instrumental polarisation in CMB experiments at microwave wavelengths

Carretti, E.; Tascone, R.; Cortiglioni, S.; Monari, Jader; Orsini, M.

doi:10.1016/s1384-1076(01)00050-1

Cited by 26 publications

(43 citation statements)

References 32 publications

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“…This result extends Eq. (18) in Carretti et al (2001) to Q. Further properties of the axisymmetric case lead to a better understanding of the nature of this contamination and the instrumental polarization beam Π = Π Q + jΠ U .…”

Section: Axisymmetric Casementioning

confidence: 99%

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Antenna instrumental polarization and its effects on E- and B-modes for CMBP observations

Carretti¹,

Cortiglioni²,

Sbarra³

et al. 2004

A&A

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Abstract. We analyze the instrumental polarization generated by the antenna system (optics and feed horn) due to the unpolarized sky emission. Our equations show that it is given by the convolution of the unpolarized emission map T b (θ, φ) with a sort of instrumental polarization beam Π defined by the co-and cross-polar patterns of the antenna. This result is general, it can be applied to all antenna systems and is valid for all schemes to detect polarization, like correlation and differential polarimeters. The axisymmetric case is attractive: it generates an E-mode-like Π pattern, the contamination does not depend on the scanning strategy and the instrumental polarization map does not have B-mode contamination, making axisymmetric systems suitable to detect the faint B-mode signal of the Cosmic Microwave Background Polarization. The E-mode of the contamination only affects the FWHM scales leaving the larger ones significantly cleaner. Our analysis is also applied to the SPOrt experiment where we find that the contamination of the E-mode is negligible in the -range of interest for CMBP large angular scale investigations (multipole < 10).

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Section: Axisymmetric Casementioning

confidence: 99%

“…(A.6) in Carretti et al (2001), where only the effect on U with the antenna pointing towards the North Pole was computed.…”

Section: Instrumental Polarization Of the Antenna Systemmentioning

confidence: 99%

Antenna instrumental polarization and its effects on E- and B-modes for CMBP observations

Carretti¹,

Cortiglioni²,

Sbarra³

et al. 2004

A&A

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“…Furthermore, there are no reflections from optical surfaces to induce spurious instrumental polarization, an unavoidable problem for any system with imaging optics 26,27,28,29 . In MBI there are no aberrations from off-axis pixels: all feed elements are equivalent and all the optics are at cryogenic temperatures to minimize losses.…”

Section: Control Of Systematic Effectsmentioning

confidence: 99%

The millimeter-wave bolometric interferometer

et al. 2006

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The Millimeter-Wave Bolometric Interferometer (MBI) is designed for sensitive measurements of the polarization of the cosmic microwave background (CMB). MBI combines the differencing capabilities of an interferometer with the high sensitivity of bolometers at millimeter wavelengths. It views the sky directly through corrugated horn antennas with low sidelobes and nearly symmetric beam patterns to avoid spurious instrumental polarization from reflective optics. The design of the first version of the instrument with four 7-degree-FOV corrugated horns (MBI-4) is discussed. The MBI-4 optical band is defined by filters with a central frequency of 90 GHz. The set of baselines determined by the antenna separation makes the instrument sensitive to CMB polarization fluctuations over the multipole range l=150-270. In MBI-4, the signals from antennas are combined with a Fizeau beam combiner and interference fringes are detected by an array of spider-web bolometers with NTD germanium thermistors. In order to separate the visibility signals from the total power detected by each bolometer, the phase of the signal from each antenna is modulated by a ferrite-based waveguide phase shifter. Observations are planned from the Pine Bluff Observatory outside Madison, WI.

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“…However, when using correlation techniques, the knee frequency is reduced by a factor (T offset /T sys ) 2 , with T offset and T sys the instrumental offset and the system noise temperature, respectively (Wollack & Pospiesalski 1998;Carretti et al 2001). The present state of the instrument already guarantees a value f k < 2.5 × 10 −5 Hz , close to the goal knee frequency of one tenth of the ISS orbit frequency, i.e.…”

Section: Introductionmentioning

confidence: 99%

An iterative destriping technique for diffuse background polarization data

Sbarra¹,

Carretti²,

Cortiglioni³

et al. 2003

A&A

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Abstract. We describe a simple but effective iterative procedure specifically designed to destripe Q and U Stokes parameter data as those collected by the SPOrt experiment onboard the International Space Station (ISS). The method is general enough to be useful for other experiments, both in polarization and total intensity. The only requirement for the algorithm to work properly is that the receiver knee frequency must be lower than the signal modulation frequency, corresponding in our case to the ISS orbit period. Detailed performances of the technique are presented in the context of the SPOrt experiment, both in terms of added rms noise and residual correlated noise.

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Limits due to instrumental polarisation in CMB experiments at microwave wavelengths

Cited by 26 publications

References 32 publications

Antenna instrumental polarization and its effects on E- and B-modes for CMBP observations

Antenna instrumental polarization and its effects on E- and B-modes for CMBP observations

The millimeter-wave bolometric interferometer

An iterative destriping technique for diffuse background polarization data

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