Fast map-based simulations of systematics in CMB surveys including effects of the scanning strategy

McCallum, Nialh; Thomas, Daniel B.; Brown, Michael L.

doi:10.1093/mnras/stac561

Cited by 3 publications

(3 citation statements)

References 57 publications

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“…• Differential Gain g: The absolute value of the difference between the maximal peak directivity of the beam in the E and H-planes (1), and respectively, expected to be 1% or lower [18,21,23] to avoid contaminations of the B-mode signal,…”

Section: Beam Systematics For Cmb Observationsmentioning

confidence: 99%

Experimental characterisation of a planar phase-engineered metamaterial lenslet for millimetre astronomy

Gascard¹,

Pisano²,

Doyle³

et al. 2023

Preprint

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To unveil presently inscrutable details of the origins of our Universe imprinted in the Cosmic Microwave Background, future experiments in the millimetre and sub-millimetre range are focusing on the detection of fine features which necessitate large and sensitive detector arrays to enable multichroic mapping of the sky. Currently, various approaches for coupling light to such detectors are under investigation, namely: coherently summed hierarchical arrays, platelet horns and antenna coupled planar lenslets. The last option offers increased bandwidth and a simpler fabrication whilst maintaining the desired optical performance. In this work, the design, fabrication and experimental characterisation of a prototype planar metamaterial phase-engineered lenslet operating in W-band [75GHz;110GHz] is presented. Its radiated field, initially modelled and measured on a systematics limited optical bench, is compared against a simulated hyper-hemispherical lenslet, a more established technology. It is reported here that our device reaches the CMB specification for the next stages of experiments, demonstrating power coupling above 95%, beam gaussicity above 97% whilst maintaining ellipticity below 10% and cross-polarisation level below -21dB through its operating bandwidth. Such results underlines the potential advantages our lenslet can offer as focal optics for future CMB experiments.

show abstract

Section: Beam Systematics For Cmb Observationsmentioning

confidence: 99%

Experimental characterisation of a planar phase-engineered metamaterial lenslet for millimetre astronomy

Gascard¹,

Pisano²,

Doyle³

et al. 2023

Preprint

View full text Add to dashboard Cite

show abstract

“…In these analyses, the detectors and their coupled focal optics are merged into a single pixel object receiving two orthogonal polarisations. The beam of each pixel constituting the focal plane is reshaped by the modelled telescope fore-optics and sky maps are either reconstructed by projecting the simulated detector signals through the instrument model or by convoluting an input sky map with the telescope beam following its devised scanning strategy [21,22]. In order to establish the performances of our metamaterial-based lenslet for CMB experiments, it is useful to underline some optics induced systematics and properties:…”

Section: Beam Systematics For Cmb Observationsmentioning

confidence: 99%

“…• Gaussicity 𝜂 0 : Fraction of the power contained in the beam main lobe corresponding to the 0 th order optical mode of a Laguerre-Gaussian Beam (LGB) beam decomposition, • Differential Gain 𝚫g: The absolute value of the difference between the maximal peak directivity of the beam in the E and H-planes (1), 𝑔 𝐸 and 𝑔 𝐻 respectively, expected to be 1% or lower [18,21,23] to avoid contaminations of the B-mode signal, • Beam Ellipticity E: Square of the numerical eccentricity of the beam (2), where 𝑤 𝐸 0 and 𝑤 𝐻 0 are the beam waist in the E and H-planes, • Cross-polarisation Beam Shapes: The cross-polarisation is defined as per [24] and effectively describes a leakage from one polarisation to the other. For axi-symmetrical optics radiating a linearly polarised wave, the cross-polarisation shapes presents a quadrupole symmetry near the optical axis, transforming to a dipole-like symmetry off axis which can be derived in the limit case of a circular aperture [25].…”

Section: Beam Systematics For Cmb Observationsmentioning

confidence: 99%

Experimental characterization of a planar phase-engineered metamaterial lenslet for millimeter astronomy

et al. 2023

View full text Add to dashboard Cite

To unveil presently inscrutable details of the origins of our Universe imprinted in the Cosmic Microwave Background, future experiments in the millimetre and sub-millimetre range are focusing on the detection of fine features which necessitate large and sensitive detector arrays to enable multichroic mapping of the sky. Currently, various approaches for coupling light to such detectors are under investigation, namely: coherently summed hierarchical arrays, platelet horns and antenna coupled planar lenslets. The last option offers increased bandwidth and a simpler fabrication whilst maintaining the desired optical performance. In this work, the design, fabrication and experimental characterisation of a prototype planar metamaterial phase-engineered lenslet operating in W-band [75GHz; 110GHz] is presented. Its radiated field, initially modelled and measured on a systematics limited optical bench, is compared against a simulated hyper-hemispherical lenslet, a more established technology. It is reported here that our device reaches the CMB specification for the next stages of experiments, demonstrating power coupling above 95%, beam gaussicity above 97% whilst maintaining ellipticity below 10% and cross-polarisation level below −21dB through its operating bandwidth. Such results underlines the potential advantages our lenslet can offer as focal optics for future CMB experiments.

show abstract

Multi-dimensional optimisation of the scanning strategy for the LiteBIRD space mission

Takase,

Vacher,

Ishino

et al. 2024

J. Cosmol. Astropart. Phys.

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Large angular scale surveys in the absence of atmosphere are essential for measuring the primordial B-mode power spectrum of the Cosmic Microwave Background (CMB). Since this proposed measurement is about three to four orders of magnitude fainter than the temperature anisotropies of the CMB, in-flight calibration of the instruments and active suppression of systematic effects are crucial. We investigate the effect of changing the parameters of the scanning strategy on the in-flight calibration effectiveness, the suppression of the systematic effects themselves, and the ability to distinguish systematic effects by null-tests. Next-generation missions such as LiteBIRD, modulated by a Half-Wave Plate (HWP), will be able to observe polarisation using a single detector, eliminating the need to combine several detectors to measure polarisation, as done in many previous experiments and hence avoiding the consequent systematic effects. While the HWP is expected to suppress many systematic effects, some of them will remain. We use an analytical approach to comprehensively address the mitigation of these systematic effects and identify the characteristics of scanning strategies that are the most effective for implementing a variety of calibration strategies in the multi-dimensional space of common spacecraft scan parameters. We verify that LiteBIRD's standard configuration yields good performance on the metrics we studied. We also present Falcons.jl, a fast spacecraft scanning simulator that we developed to investigate this scanning parameter space.

show abstract

Fast map-based simulations of systematics in CMB surveys including effects of the scanning strategy

Cited by 3 publications

References 57 publications

Experimental characterisation of a planar phase-engineered metamaterial lenslet for millimetre astronomy

Experimental characterisation of a planar phase-engineered metamaterial lenslet for millimetre astronomy

Experimental characterization of a planar phase-engineered metamaterial lenslet for millimeter astronomy

Multi-dimensional optimisation of the scanning strategy for the LiteBIRD space mission

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