Roberto Puddu - Academia.edu (original) (raw)

Papers by Roberto Puddu

Research paper thumbnail of CCAT-prime Collaboration: Science Goals and Forecasts with Prime-Cam on the Fred Young Submillimeter Telescope

The Astrophysical Journal Supplement Series

We present a detailed overview of the science goals and predictions for the Prime-Cam direct-dete... more We present a detailed overview of the science goals and predictions for the Prime-Cam direct-detection camera–spectrometer being constructed by the CCAT-prime collaboration for dedicated use on the Fred Young Submillimeter Telescope (FYST). The FYST is a wide-field, 6 m aperture submillimeter telescope being built (first light in late 2023) by an international consortium of institutions led by Cornell University and sited at more than 5600 m on Cerro Chajnantor in northern Chile. Prime-Cam is one of two instruments planned for FYST and will provide unprecedented spectroscopic and broadband measurement capabilities to address important astrophysical questions ranging from Big Bang cosmology through reionization and the formation of the first galaxies to star formation within our own Milky Way. Prime-Cam on the FYST will have a mapping speed that is over 10 times greater than existing and near-term facilities for high-redshift science and broadband polarimetric imaging at frequencies ...

Research paper thumbnail of The Atacama Cosmology Telescope: Map-Based Noise Simulations for DR6

arXiv (Cornell University), Mar 7, 2023

Research paper thumbnail of The Atacama Cosmology Telescope: Flux Upper Limits from a Targeted Search for Extragalactic Transients

arXiv (Cornell University), Jan 18, 2023

Research paper thumbnail of Simons Observatory: characterizing the Large Aperture Telescope Receiver with radio holography

Applied Optics

We present near-field radio holography measurements of the Simons Observatory Large Aperture Tele... more We present near-field radio holography measurements of the Simons Observatory Large Aperture Telescope Receiver optics. These measurements demonstrate that radio holography of complex millimeter-wave optical systems comprising cryogenic lenses, filters, and feed horns can provide detailed characterization of wave propagation before deployment. We used the measured amplitude and phase, at 4 K, of the receiver near-field beam pattern to predict two key performance parameters: 1) the amount of scattered light that will spill past the telescope to 300 K and 2) the beam pattern expected from the receiver when fielded on the telescope. These cryogenic measurements informed the removal of a filter, which led to improved optical efficiency and reduced sidelobes at the exit of the receiver. Holography measurements of this system suggest that the spilled power past the telescope mirrors will be less than 1%, and the main beam with its near sidelobes are consistent with the nominal telescope d...

Research paper thumbnail of The Atacama Cosmology Telescope: Measurement and Analysis of 1D Beams for DR4

We describe the measurement and treatment of the telescope beams for the Atacama Cosmology Telesc... more We describe the measurement and treatment of the telescope beams for the Atacama Cosmology Telescope’s fourth data release, DR4. Observations of Uranus are used to measure the central portion (< 12′) of the beams to roughly −40 dB of the peak. Such planet maps in intensity are used to construct azimuthally averaged beam profiles, which are fit with a physically motivated model before being transformed into Fourier space. We investigate and quantify a number of percent-level corrections to the beams, all of which are important for precision cosmology. Uranus maps in polarization are used to measure the temperature-to-polarization leakage in the main part of the beams, which is . 1% (2.5%) at 150 GHz (98 GHz). The beams also have polarized sidelobes, which are measured with observations of Saturn and deprojected from the ACT time-ordered data. Notable changes relative to past ACT beam analyses include an improved subtraction of the atmospheric effects from Uranus calibration maps, ...

Research paper thumbnail of The Simons Observatory: Science goals and forecasts

The Simons Observatory (SO) is a new cosmic microwave background experiment being built on Cerro ... more The Simons Observatory (SO) is a new cosmic microwave background experiment being built on Cerro Toco in Chile, due to begin observations in the early 2020s. We describe the scientific goals of the experiment, motivate the design, and forecast its performance. SO will measure the temperature and polarization anisotropy of the cosmic microwave background in six frequency bands: 27, 39, 93, 145, 225 and 280 GHz. The initial configuration of SO will have three small-aperture 0.5-m telescopes (SATs) and one large-aperture 6-m telescope (LAT), with a total of 60,000 cryogenic bolometers. Our key science goals are to characterize the primordial perturbations, measure the number of relativistic species and the mass of neutrinos, test for deviations from a cosmological constant, improve our understanding of galaxy evolution, and constrain the duration of reionization. The SATs will target the largest angular scales observable from Chile, mapping 10 level of 2 μK-arcmin in combined 93 and 14...

Research paper thumbnail of Simulations and performance of the QUBIC optical beam combiner

Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy IX

Research paper thumbnail of Detection chain and electronic readout of the QUBIC instrument

The Q and U Bolometric Interferometer for Cosmology (QUBIC) Technical Demonstrator (TD) aiming to... more The Q and U Bolometric Interferometer for Cosmology (QUBIC) Technical Demonstrator (TD) aiming to shows the feasibility of the combination of interferometry and bolometric detection. The electronic readout system is based on an array of 128 NbSi Transition Edge Sensors cooled at 350mK readout with 128 SQUIDs at 1K controlled and amplified by an Application Specific Integrated Circuit at 40K. This readout design allows a 128:1 Time Domain Multiplexing. We report the design and the performance of the detection chain in this paper. The technological demonstrator unwent a campaign of test in the lab. Evaluation of the QUBIC bolometers and readout electronics includes the measurement of I-V curves, time constant and the Noise Equivalent Power. Currently the mean Noise Equivalent Power is ~ 2 x 10-16W= p √Hz

Research paper thumbnail of QUBIC Technological Design Report

QUBIC is an instrument aiming at measuring the B mode polarisation anisotropies at medium scales ... more QUBIC is an instrument aiming at measuring the B mode polarisation anisotropies at medium scales angular scales (30-200 multipoles). The search for the primordial CMB B-mode polarization signal is challenging, because of many difficulties: smallness of the expected signal, instrumental systematics that could possibly induce polarization leakage from the large E signal into B, brighter than anticipated polarized foregrounds (dust) reducing to zero the initial hope of finding sky regions clean enough to have a direct primordial B-modes observation. The QUBIC instrument is designed to address all aspects of this challenge with a novel kind of instrument, a Bolometric Interferometer, combining the background-limited sensitivity of Transition-Edge-Sensors and the control of systematics allowed by the observation of interference fringe patterns, while operating at two frequencies to disentangle polarized foregrounds from primordial B mode polarization. Its characteristics are described in...

Research paper thumbnail of Thermal architecture for the QUBIC cryogenic receiver

Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy IX

Research paper thumbnail of Astro 2020 APC White

Co-authors: Felix J. Lockman (GBO), Paul Goldsmith (JPL), Andrew I. Harris (Univ. of Maryland), K... more Co-authors: Felix J. Lockman (GBO), Paul Goldsmith (JPL), Andrew I. Harris (Univ. of Maryland), Kieran A. Cleary (Caltech), Joshua O. Gundersen (Univ. of Miami), Laura Jensen (GBO), Alvaro Hacar (Leiden University), Che-Yu Chen (Univ. of Virginia), Will Armentrout (GBO), Natalie Butterfield (GBO), Larry Morgan (GBO), Amanda Kepley (NRAO), Jialu Li (Univ. of Maryland), Ian Stephens (CfA/SAO), Sarah Sadavoy (CfA/SAO), Kevin Harrington (Univ. of Bonn, AIfA), Jaime Pineda (Max-Planck), Zhi-Yun Li (Univ. of Virginia), Anthony Readhead (Caltech), Sarah Church (Stanford), Steven White (GBO), Randy McCullough (GBO), Galen Watts (GBO), Dennis Egan (GBO), Martin Bloss (GBO)

Research paper thumbnail of QUBIC: the Q and U bolometric interferometer for cosmology

QUBIC, the Q & U Bolometric Interferometer for Cosmology, is a novel ground-based instrument that... more QUBIC, the Q & U Bolometric Interferometer for Cosmology, is a novel ground-based instrument that has been designed to measure the extremely faint B-mode polarisation anisotropy of the cosmic microwave background at intermediate angular scales (multipoles of 𝑙 = 30 − 200). Primordial B-modes are a key prediction of Inflation as they can only be produced by gravitational waves in the very early universe. To achieve this goal, QUBIC will use bolometric interferometry, a technique that combines the sensitivity of an imager with the systematic error control of an interferometer. It will directly observe the sky through an array of 400 back-to-back entry horns whose signals will be superimposed using a quasi-optical beam combiner. The resulting interference fringes will be imaged at 150 and 220 GHz on two focal planes, each tiled with NbSi Transition Edge Sensors, cooled to 320 mK and read out with time-domain multiplexing. A dichroic filter placed between the optical combiner and the fo...

Research paper thumbnail of The Simons Observatory: Astro2020 Decadal Project Whitepaper

arXiv: Instrumentation and Methods for Astrophysics, 2019

The Simons Observatory (SO) is a ground-based cosmic microwave background (CMB) experiment sited ... more The Simons Observatory (SO) is a ground-based cosmic microwave background (CMB) experiment sited on Cerro Toco in the Atacama Desert in Chile that promises to provide breakthrough discoveries in fundamental physics, cosmology, and astrophysics. Supported by the Simons Foundation, the Heising-Simons Foundation, and with contributions from collaborating institutions, SO will see first light in 2021 and start a five year survey in 2022. SO has 287 collaborators from 12 countries and 53 institutions, including 85 students and 90 postdocs. The SO experiment in its currently funded form ('SO-Nominal') consists of three 0.4 m Small Aperture Telescopes (SATs) and one 6 m Large Aperture Telescope (LAT). Optimized for minimizing systematic errors in polarization measurements at large angular scales, the SATs will perform a deep, degree-scale survey of 10% of the sky to search for the signature of primordial gravitational waves. The LAT will survey 40% of the sky with arc-minute resolu...

Research paper thumbnail of The CCAT-Prime Submillimeter Observatory

The Cerro Chajnantor Atacama Telescope-prime (CCAT-prime) is a new 6-m, off-axis, low-emissivity,... more The Cerro Chajnantor Atacama Telescope-prime (CCAT-prime) is a new 6-m, off-axis, low-emissivity, large field-of-view submillimeter telescope scheduled for first light in the last quarter of 2021. In summary, (a) CCAT-prime uniquely combines a large field-of-view (up to 8-deg), low emissivity telescope (< 2%) and excellent atmospheric transmission (5600-m site) to achieve unprecedented survey capability in the submillimeter. (b) Over five years, CCAT-prime first generation science will address the physics of star formation, galaxy evolution, and galaxy cluster formation; probe the re-ionization of the Universe; improve constraints on new particle species; and provide for improved removal of dust foregrounds to aid the search for primordial gravitational waves. (c) The Observatory is being built with non-federal funds (~ \$40M in private and international investments). Public funding is needed for instrumentation (~ \$8M) and operations (\$1-2M/yr). In return, the community will b...

Research paper thumbnail of The Simons Observatory: modeling optical systematics in the Large Aperture Telescope

Applied Optics

We present geometrical and physical optics simulation results for the Simons Observatory Large Ap... more We present geometrical and physical optics simulation results for the Simons Observatory Large Aperture Telescope. This work was developed as part of the general design process for the telescope; allowing us to evaluate the impact of various design choices on performance metrics and potential systematic effects. The primary goal of the simulations was to evaluate the final design of the reflectors and the cold optics which are now being built. We describe non-sequential ray tracing used to inform the design of the cold optics, including absorbers internal to each optics tube. We discuss ray tracing simulations of the telescope structure that allow us to determine geometries that minimize detector loading and mitigate spurious near-field effects that have not been resolved by the internal baffling. We also describe physical optics simulations, performed over a range of frequencies and field locations, that produce estimates of monochromatic far field beam patterns which in turn are used to gauge general optical performance. Finally, we describe simulations that shed light on beam sidelobes from panel gap diffraction.

Research paper thumbnail of QUBIC: Observing the Polarized Microwave Sky over the Puna

Science Reviews - from the end of the world

QUBIC (Q&U Bolometric Interferometer for Cosmology) is an experiment designed to measure the pola... more QUBIC (Q&U Bolometric Interferometer for Cosmology) is an experiment designed to measure the polarization of the cosmic microwave background (CMB), the relic radiation from the Big- Bang. Detailed measurements of tiny temperature anisotropies in the CMB shaped our understanding of the early Universe. Accurate measurements of its polarization may reveal even earlier features, in particular the presence of gravitational waves with primordial origin. Such measurements can probe inflationary cosmological models, which postulate that quantum effects during an accelerated expansion at the earliest stages after the Big-Bang produced gravitational waves along with the density fluctuations that later seeded galaxy formation. QUBIC will join other international efforts currently pursuing this goal using a novel approach, which combines the sensitivity of bolometric detectors with the control of systematic effects provided by interferometry. After its current calibration phase is completed a t...

Research paper thumbnail of Performance of NbSi transition-edge sensors readout with a 128 MUX factor for the QUBIC experiment

Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy IX, Jul 9, 2018

Research paper thumbnail of Far sidelobes from baffles and telescope support structures in the Atacama Cosmology Telescope

Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy IX, Aug 15, 2018

The Atacama Cosmology Telescope (ACT) is a 6 m telescope located in the Atacama Desert, designed ... more The Atacama Cosmology Telescope (ACT) is a 6 m telescope located in the Atacama Desert, designed to measure the cosmic microwave background (CMB) with arcminute resolution. ACT, with its third generation polarization sensitive array, Advanced ACTPol, is being used to measure the anisotropies of the CMB in five frequency bands in large areas of the sky (∼ 15, 000 deg 2). These measurements are designed to characterize the large scale structure of the universe, test cosmological models and constrain the sum of the neutrino masses. As the sensitivity of these wide surveys increases, the control and validation of the far sidelobe response becomes increasingly important and is particularly challenging as multiple reflections, spillover, diffraction and scattering become difficult to model and characterize at the required levels. In this work, we present a ray trace model of the ACT upper structure which is used to describe much of the observed far sidelobe pattern. This model combines secondary mirror spillover measurements with a 3D CAD model based on photogrammetry measurements to simulate the beam of the camera and the comoving ground shield. This simulation shows qualitative agreement with physical optics tools and features observed in far sidelobe measurements. We present this method as an efficient first-order calculation that, although it does not capture all diffraction effects, informs interactions between the structural components of the telescope and the optical path, which can then be combined with more computationally intensive physical optics calculations. This method can be used to predict sidelobe patterns in the design stage of future optical systems such as the Simons Observatory, CCAT-prime, and CMB Stage IV.

Research paper thumbnail of The Simons Observatory: science goals and forecasts

Journal of Cosmology and Astroparticle Physics

Research paper thumbnail of QUBIC: Exploring the Primordial Universe with the Q&U Bolometric Interferometer

Universe

In this paper, we describe QUBIC, an experiment that will observe the polarized microwave sky wit... more In this paper, we describe QUBIC, an experiment that will observe the polarized microwave sky with a novel approach, which combines the sensitivity of state-of-the-art bolometric detectors with the systematic effects control typical of interferometers. QUBIC’s unique features are the so-called “self-calibration”, a technique that allows us to clean the measured data from instrumental effects, and its spectral imaging power, i.e., the ability to separate the signal into various sub-bands within each frequency band. QUBIC will observe the sky in two main frequency bands: 150 GHz and 220 GHz. A technological demonstrator is currently under testing and will be deployed in Argentina during 2019, while the final instrument is expected to be installed during 2020.

Research paper thumbnail of CCAT-prime Collaboration: Science Goals and Forecasts with Prime-Cam on the Fred Young Submillimeter Telescope

The Astrophysical Journal Supplement Series

We present a detailed overview of the science goals and predictions for the Prime-Cam direct-dete... more We present a detailed overview of the science goals and predictions for the Prime-Cam direct-detection camera–spectrometer being constructed by the CCAT-prime collaboration for dedicated use on the Fred Young Submillimeter Telescope (FYST). The FYST is a wide-field, 6 m aperture submillimeter telescope being built (first light in late 2023) by an international consortium of institutions led by Cornell University and sited at more than 5600 m on Cerro Chajnantor in northern Chile. Prime-Cam is one of two instruments planned for FYST and will provide unprecedented spectroscopic and broadband measurement capabilities to address important astrophysical questions ranging from Big Bang cosmology through reionization and the formation of the first galaxies to star formation within our own Milky Way. Prime-Cam on the FYST will have a mapping speed that is over 10 times greater than existing and near-term facilities for high-redshift science and broadband polarimetric imaging at frequencies ...

Research paper thumbnail of The Atacama Cosmology Telescope: Map-Based Noise Simulations for DR6

arXiv (Cornell University), Mar 7, 2023

Research paper thumbnail of The Atacama Cosmology Telescope: Flux Upper Limits from a Targeted Search for Extragalactic Transients

arXiv (Cornell University), Jan 18, 2023

Research paper thumbnail of Simons Observatory: characterizing the Large Aperture Telescope Receiver with radio holography

Applied Optics

We present near-field radio holography measurements of the Simons Observatory Large Aperture Tele... more We present near-field radio holography measurements of the Simons Observatory Large Aperture Telescope Receiver optics. These measurements demonstrate that radio holography of complex millimeter-wave optical systems comprising cryogenic lenses, filters, and feed horns can provide detailed characterization of wave propagation before deployment. We used the measured amplitude and phase, at 4 K, of the receiver near-field beam pattern to predict two key performance parameters: 1) the amount of scattered light that will spill past the telescope to 300 K and 2) the beam pattern expected from the receiver when fielded on the telescope. These cryogenic measurements informed the removal of a filter, which led to improved optical efficiency and reduced sidelobes at the exit of the receiver. Holography measurements of this system suggest that the spilled power past the telescope mirrors will be less than 1%, and the main beam with its near sidelobes are consistent with the nominal telescope d...

Research paper thumbnail of The Atacama Cosmology Telescope: Measurement and Analysis of 1D Beams for DR4

We describe the measurement and treatment of the telescope beams for the Atacama Cosmology Telesc... more We describe the measurement and treatment of the telescope beams for the Atacama Cosmology Telescope’s fourth data release, DR4. Observations of Uranus are used to measure the central portion (< 12′) of the beams to roughly −40 dB of the peak. Such planet maps in intensity are used to construct azimuthally averaged beam profiles, which are fit with a physically motivated model before being transformed into Fourier space. We investigate and quantify a number of percent-level corrections to the beams, all of which are important for precision cosmology. Uranus maps in polarization are used to measure the temperature-to-polarization leakage in the main part of the beams, which is . 1% (2.5%) at 150 GHz (98 GHz). The beams also have polarized sidelobes, which are measured with observations of Saturn and deprojected from the ACT time-ordered data. Notable changes relative to past ACT beam analyses include an improved subtraction of the atmospheric effects from Uranus calibration maps, ...

Research paper thumbnail of The Simons Observatory: Science goals and forecasts

The Simons Observatory (SO) is a new cosmic microwave background experiment being built on Cerro ... more The Simons Observatory (SO) is a new cosmic microwave background experiment being built on Cerro Toco in Chile, due to begin observations in the early 2020s. We describe the scientific goals of the experiment, motivate the design, and forecast its performance. SO will measure the temperature and polarization anisotropy of the cosmic microwave background in six frequency bands: 27, 39, 93, 145, 225 and 280 GHz. The initial configuration of SO will have three small-aperture 0.5-m telescopes (SATs) and one large-aperture 6-m telescope (LAT), with a total of 60,000 cryogenic bolometers. Our key science goals are to characterize the primordial perturbations, measure the number of relativistic species and the mass of neutrinos, test for deviations from a cosmological constant, improve our understanding of galaxy evolution, and constrain the duration of reionization. The SATs will target the largest angular scales observable from Chile, mapping 10 level of 2 μK-arcmin in combined 93 and 14...

Research paper thumbnail of Simulations and performance of the QUBIC optical beam combiner

Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy IX

Research paper thumbnail of Detection chain and electronic readout of the QUBIC instrument

The Q and U Bolometric Interferometer for Cosmology (QUBIC) Technical Demonstrator (TD) aiming to... more The Q and U Bolometric Interferometer for Cosmology (QUBIC) Technical Demonstrator (TD) aiming to shows the feasibility of the combination of interferometry and bolometric detection. The electronic readout system is based on an array of 128 NbSi Transition Edge Sensors cooled at 350mK readout with 128 SQUIDs at 1K controlled and amplified by an Application Specific Integrated Circuit at 40K. This readout design allows a 128:1 Time Domain Multiplexing. We report the design and the performance of the detection chain in this paper. The technological demonstrator unwent a campaign of test in the lab. Evaluation of the QUBIC bolometers and readout electronics includes the measurement of I-V curves, time constant and the Noise Equivalent Power. Currently the mean Noise Equivalent Power is ~ 2 x 10-16W= p √Hz

Research paper thumbnail of QUBIC Technological Design Report

QUBIC is an instrument aiming at measuring the B mode polarisation anisotropies at medium scales ... more QUBIC is an instrument aiming at measuring the B mode polarisation anisotropies at medium scales angular scales (30-200 multipoles). The search for the primordial CMB B-mode polarization signal is challenging, because of many difficulties: smallness of the expected signal, instrumental systematics that could possibly induce polarization leakage from the large E signal into B, brighter than anticipated polarized foregrounds (dust) reducing to zero the initial hope of finding sky regions clean enough to have a direct primordial B-modes observation. The QUBIC instrument is designed to address all aspects of this challenge with a novel kind of instrument, a Bolometric Interferometer, combining the background-limited sensitivity of Transition-Edge-Sensors and the control of systematics allowed by the observation of interference fringe patterns, while operating at two frequencies to disentangle polarized foregrounds from primordial B mode polarization. Its characteristics are described in...

Research paper thumbnail of Thermal architecture for the QUBIC cryogenic receiver

Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy IX

Research paper thumbnail of Astro 2020 APC White

Co-authors: Felix J. Lockman (GBO), Paul Goldsmith (JPL), Andrew I. Harris (Univ. of Maryland), K... more Co-authors: Felix J. Lockman (GBO), Paul Goldsmith (JPL), Andrew I. Harris (Univ. of Maryland), Kieran A. Cleary (Caltech), Joshua O. Gundersen (Univ. of Miami), Laura Jensen (GBO), Alvaro Hacar (Leiden University), Che-Yu Chen (Univ. of Virginia), Will Armentrout (GBO), Natalie Butterfield (GBO), Larry Morgan (GBO), Amanda Kepley (NRAO), Jialu Li (Univ. of Maryland), Ian Stephens (CfA/SAO), Sarah Sadavoy (CfA/SAO), Kevin Harrington (Univ. of Bonn, AIfA), Jaime Pineda (Max-Planck), Zhi-Yun Li (Univ. of Virginia), Anthony Readhead (Caltech), Sarah Church (Stanford), Steven White (GBO), Randy McCullough (GBO), Galen Watts (GBO), Dennis Egan (GBO), Martin Bloss (GBO)

Research paper thumbnail of QUBIC: the Q and U bolometric interferometer for cosmology

QUBIC, the Q & U Bolometric Interferometer for Cosmology, is a novel ground-based instrument that... more QUBIC, the Q & U Bolometric Interferometer for Cosmology, is a novel ground-based instrument that has been designed to measure the extremely faint B-mode polarisation anisotropy of the cosmic microwave background at intermediate angular scales (multipoles of 𝑙 = 30 − 200). Primordial B-modes are a key prediction of Inflation as they can only be produced by gravitational waves in the very early universe. To achieve this goal, QUBIC will use bolometric interferometry, a technique that combines the sensitivity of an imager with the systematic error control of an interferometer. It will directly observe the sky through an array of 400 back-to-back entry horns whose signals will be superimposed using a quasi-optical beam combiner. The resulting interference fringes will be imaged at 150 and 220 GHz on two focal planes, each tiled with NbSi Transition Edge Sensors, cooled to 320 mK and read out with time-domain multiplexing. A dichroic filter placed between the optical combiner and the fo...

Research paper thumbnail of The Simons Observatory: Astro2020 Decadal Project Whitepaper

arXiv: Instrumentation and Methods for Astrophysics, 2019

The Simons Observatory (SO) is a ground-based cosmic microwave background (CMB) experiment sited ... more The Simons Observatory (SO) is a ground-based cosmic microwave background (CMB) experiment sited on Cerro Toco in the Atacama Desert in Chile that promises to provide breakthrough discoveries in fundamental physics, cosmology, and astrophysics. Supported by the Simons Foundation, the Heising-Simons Foundation, and with contributions from collaborating institutions, SO will see first light in 2021 and start a five year survey in 2022. SO has 287 collaborators from 12 countries and 53 institutions, including 85 students and 90 postdocs. The SO experiment in its currently funded form ('SO-Nominal') consists of three 0.4 m Small Aperture Telescopes (SATs) and one 6 m Large Aperture Telescope (LAT). Optimized for minimizing systematic errors in polarization measurements at large angular scales, the SATs will perform a deep, degree-scale survey of 10% of the sky to search for the signature of primordial gravitational waves. The LAT will survey 40% of the sky with arc-minute resolu...

Research paper thumbnail of The CCAT-Prime Submillimeter Observatory

The Cerro Chajnantor Atacama Telescope-prime (CCAT-prime) is a new 6-m, off-axis, low-emissivity,... more The Cerro Chajnantor Atacama Telescope-prime (CCAT-prime) is a new 6-m, off-axis, low-emissivity, large field-of-view submillimeter telescope scheduled for first light in the last quarter of 2021. In summary, (a) CCAT-prime uniquely combines a large field-of-view (up to 8-deg), low emissivity telescope (< 2%) and excellent atmospheric transmission (5600-m site) to achieve unprecedented survey capability in the submillimeter. (b) Over five years, CCAT-prime first generation science will address the physics of star formation, galaxy evolution, and galaxy cluster formation; probe the re-ionization of the Universe; improve constraints on new particle species; and provide for improved removal of dust foregrounds to aid the search for primordial gravitational waves. (c) The Observatory is being built with non-federal funds (~ \$40M in private and international investments). Public funding is needed for instrumentation (~ \$8M) and operations (\$1-2M/yr). In return, the community will b...

Research paper thumbnail of The Simons Observatory: modeling optical systematics in the Large Aperture Telescope

Applied Optics

We present geometrical and physical optics simulation results for the Simons Observatory Large Ap... more We present geometrical and physical optics simulation results for the Simons Observatory Large Aperture Telescope. This work was developed as part of the general design process for the telescope; allowing us to evaluate the impact of various design choices on performance metrics and potential systematic effects. The primary goal of the simulations was to evaluate the final design of the reflectors and the cold optics which are now being built. We describe non-sequential ray tracing used to inform the design of the cold optics, including absorbers internal to each optics tube. We discuss ray tracing simulations of the telescope structure that allow us to determine geometries that minimize detector loading and mitigate spurious near-field effects that have not been resolved by the internal baffling. We also describe physical optics simulations, performed over a range of frequencies and field locations, that produce estimates of monochromatic far field beam patterns which in turn are used to gauge general optical performance. Finally, we describe simulations that shed light on beam sidelobes from panel gap diffraction.

Research paper thumbnail of QUBIC: Observing the Polarized Microwave Sky over the Puna

Science Reviews - from the end of the world

QUBIC (Q&U Bolometric Interferometer for Cosmology) is an experiment designed to measure the pola... more QUBIC (Q&U Bolometric Interferometer for Cosmology) is an experiment designed to measure the polarization of the cosmic microwave background (CMB), the relic radiation from the Big- Bang. Detailed measurements of tiny temperature anisotropies in the CMB shaped our understanding of the early Universe. Accurate measurements of its polarization may reveal even earlier features, in particular the presence of gravitational waves with primordial origin. Such measurements can probe inflationary cosmological models, which postulate that quantum effects during an accelerated expansion at the earliest stages after the Big-Bang produced gravitational waves along with the density fluctuations that later seeded galaxy formation. QUBIC will join other international efforts currently pursuing this goal using a novel approach, which combines the sensitivity of bolometric detectors with the control of systematic effects provided by interferometry. After its current calibration phase is completed a t...

Research paper thumbnail of Performance of NbSi transition-edge sensors readout with a 128 MUX factor for the QUBIC experiment

Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy IX, Jul 9, 2018

Research paper thumbnail of Far sidelobes from baffles and telescope support structures in the Atacama Cosmology Telescope

Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy IX, Aug 15, 2018

The Atacama Cosmology Telescope (ACT) is a 6 m telescope located in the Atacama Desert, designed ... more The Atacama Cosmology Telescope (ACT) is a 6 m telescope located in the Atacama Desert, designed to measure the cosmic microwave background (CMB) with arcminute resolution. ACT, with its third generation polarization sensitive array, Advanced ACTPol, is being used to measure the anisotropies of the CMB in five frequency bands in large areas of the sky (∼ 15, 000 deg 2). These measurements are designed to characterize the large scale structure of the universe, test cosmological models and constrain the sum of the neutrino masses. As the sensitivity of these wide surveys increases, the control and validation of the far sidelobe response becomes increasingly important and is particularly challenging as multiple reflections, spillover, diffraction and scattering become difficult to model and characterize at the required levels. In this work, we present a ray trace model of the ACT upper structure which is used to describe much of the observed far sidelobe pattern. This model combines secondary mirror spillover measurements with a 3D CAD model based on photogrammetry measurements to simulate the beam of the camera and the comoving ground shield. This simulation shows qualitative agreement with physical optics tools and features observed in far sidelobe measurements. We present this method as an efficient first-order calculation that, although it does not capture all diffraction effects, informs interactions between the structural components of the telescope and the optical path, which can then be combined with more computationally intensive physical optics calculations. This method can be used to predict sidelobe patterns in the design stage of future optical systems such as the Simons Observatory, CCAT-prime, and CMB Stage IV.

Research paper thumbnail of The Simons Observatory: science goals and forecasts

Journal of Cosmology and Astroparticle Physics

Research paper thumbnail of QUBIC: Exploring the Primordial Universe with the Q&U Bolometric Interferometer

Universe

In this paper, we describe QUBIC, an experiment that will observe the polarized microwave sky wit... more In this paper, we describe QUBIC, an experiment that will observe the polarized microwave sky with a novel approach, which combines the sensitivity of state-of-the-art bolometric detectors with the systematic effects control typical of interferometers. QUBIC’s unique features are the so-called “self-calibration”, a technique that allows us to clean the measured data from instrumental effects, and its spectral imaging power, i.e., the ability to separate the signal into various sub-bands within each frequency band. QUBIC will observe the sky in two main frequency bands: 150 GHz and 220 GHz. A technological demonstrator is currently under testing and will be deployed in Argentina during 2019, while the final instrument is expected to be installed during 2020.