arXiv subjects

L. Terenzi

Publications and source records attributed to L. Terenzi.

At least 37 records · Page 2Linked to original sources

arXiv2020

Progress report on the Large Scale Polarization Explorer

The Large Scale Polarization Explorer (LSPE) is a cosmology program for the measurement of large scale curl-like features (B-modes) in the polarization of the Cosmic Microwave Background. Its goal is to constrain the background of inflationary gravity waves traveling through the universe at the time of matter-radiation decoupling. The two instruments of LSPE are meant to synergically operate by covering a large portion of the northern microwave sky. LSPE/STRIP is a coherent array of receivers planned to be operated from the Teide Observatory in Tenerife, for the control and characterization of the low-frequency polarized signals of galactic origin; LSPE/SWIPE is a balloon-borne bolometric polarimeter based on 330 large throughput multi-moded detectors, designed to measure the CMB polarization at 150 GHz and to monitor the polarized emission by galactic dust above 200 GHz. The combined performance and the expected level of systematics mitigation will allow LSPE to constrain primordial B-modes down to a tensor/scalar ratio of $10^{-2}$. We here report the status of the STRIP pre-commissioning phase and the progress in the characterization of the key subsystems of the SWIPE payload (namely the cryogenic polarization modulation unit and the multi-moded TES pixels) prior to receiver integration.

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arXiv2020

Wideband 67-116 GHz receiver development for ALMA Band 2

ALMA has been operating since 2011, but has not yet been populated with the full suite of intended frequency bands. In particular, ALMA Band 2 (67-90 GHz) is the final band in the original ALMA band definition to be approved for production. We aim to produce a wideband, tuneable, sideband-separating receiver with 28 GHz of instantaneous bandwidth per polarisation operating in the sky frequency range 67-116 GHz. Our design anticipates new ALMA requirements following the recommendations in the 2030 ALMA Development Roadmap. The cryogenic cartridge is designed to be compatible with the ALMA Band 2 cartridge slot, where the coldest components -- the feedhorns, orthomode transducers, and cryogenic low noise amplifiers -- operate at a temperature of 15 K. We use multiple simulation methods and tools to optimise our designs for both the passive optics and the active components. The cryogenic cartridge interfaces with a room temperature cartridge hosting the local oscillator (LO) and the downconverter module. This warm cartridge is largely based on GaAs semiconductor technology and is optimised to match the cryogenic receiver bandwidth with the required instantaneous LO tuning range. Our collaboration has designed, fabricated, and tested multiple technical solutions for each of the components, producing a state-of-the-art receiver covering the full ALMA Band 2 & 3 atmospheric window. The receiver is suitable for deployment on ALMA in the coming years, and is capable of dual-polarisation, sideband-separating observations in intermediate frequency bands spanning 4-18 GHz, for a total of 28 GHz on-sky bandwidth per polarisation channel. We conclude that the 67-116 GHz wideband implementation for ALMA Band 2 is now feasible, and this receiver is a compelling instrumental upgrade that will enhance observational capabilities and scientific reach.

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arXiv2018

The STRIP instrument of the Large Scale Polarization Explorer: microwave eyes to map the Galactic polarized foregrounds

In this paper we discuss the latest developments of the STRIP instrument of the "Large Scale Polarization Explorer" (LSPE) experiment. LSPE is a novel project that combines ground-based (STRIP) and balloon-borne (SWIPE) polarization measurements of the microwave sky on large angular scales to attempt a detection of the "B-modes" of the Cosmic Microwave Background polarization. STRIP will observe approximately 25% of the Northern sky from the "Observatorio del Teide" in Tenerife, using an array of forty-nine coherent polarimeters at 43 GHz, coupled to a 1.5 m fully rotating crossed-Dragone telescope. A second frequency channel with six-elements at 95 GHz will be exploited as an atmospheric monitor. At present, most of the hardware of the STRIP instrument has been developed and tested at sub-system level. System-level characterization, starting in July 2018, will lead STRIP to be shipped and installed at the observation site within the end of the year. The on-site verification and calibration of the whole instrument will prepare STRIP for a 2-years campaign for the observation of the CMB polarization.

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arXiv2018

Wideband 67-116 GHz cryogenic receiver development for ALMA Band 2

The Atacama Large Millimeter/sub-millimeter Array (ALMA) is already revolutionising our understanding of the Universe. However, ALMA is not yet equipped with all of its originally planned receiver bands, which will allow it to observe over the full range of frequencies from 35-950 GHz accessible through the Earth's atmosphere. In particular Band 2 (67-90 GHz) has not yet been approved for construction. Recent technological developments in cryogenic monolithic microwave integrated circuit (MMIC) high electron mobility transistor (HEMT) amplifier and orthomode transducer (OMT) design provide an opportunity to extend the originally planned on-sky bandwidth, combining ALMA Bands 2 and 3 into one receiver cartridge covering 67-116 GHz. The IF band definition for the ALMA project took place two decades ago, when 8 GHz of on-sky bandwidth per polarisation channel was an ambitious goal. The new receiver design we present here allows the opportunity to expand ALMA's wideband capabilities, anticipating future upgrades across the entire observatory. Expanding ALMA's instantaneous bandwidth is a high priority, and provides a number of observational advantages, including lower noise in continuum observations, the ability to probe larger portions of an astronomical spectrum for, e.g., widely spaced molecular transitions, and the ability to scan efficiently in frequency space to perform surveys where the redshift or chemical complexity of the object is not known a priori. Wider IF bandwidth also reduces uncertainties in calibration and continuum subtraction that might otherwise compromise science objectives. Here we provide an overview of the component development and overall design for this wideband 67-116 GHz cryogenic receiver cartridge, designed to operate from the Band 2 receiver cartridge slot in the current ALMA front end receiver cryostat.

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arXiv2018

In-flight measurement of Planck telescope emissivity

The Planck satellite in orbit mission ended in October 2013. Between the end of Low Frequency Instrument (LFI) routine mission operations and the satellite decommissioning, a dedicated test was also performed to measure the Planck telescope emissivity. The scope of the test was twofold: (i) to provide, for the first time in flight, a direct measure of the telescope emissivity; and (ii) to evaluate the possible degradation of the emissivity by comparing data taken in flight at the end of mission with those taken during the ground telescope characterization. The emissivity was determined by heating the Planck telescope and disentangling the system temperature excess measured by the LFI radiometers. Results show End of Life (EOL) performance in good agreement with the results from the ground optical tests and from in-flight indirect estimations measured during the Commissioning and Performance Verification (CPV) phase. Methods and results are presented and discussed.

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arXiv2012

The Large-Scale Polarization Explorer (LSPE)

The LSPE is a balloon-borne mission aimed at measuring the polarization of the Cosmic Microwave Background (CMB) at large angular scales, and in particular to constrain the curl component of CMB polarization (B-modes) produced by tensor perturbations generated during cosmic inflation, in the very early universe. Its primary target is to improve the limit on the ratio of tensor to scalar perturbations amplitudes down to r = 0.03, at 99.7% confidence. A second target is to produce wide maps of foreground polarization generated in our Galaxy by synchrotron emission and interstellar dust emission. These will be important to map Galactic magnetic fields and to study the properties of ionized gas and of diffuse interstellar dust in our Galaxy. The mission is optimized for large angular scales, with coarse angular resolution (around 1.5 degrees FWHM), and wide sky coverage (25% of the sky). The payload will fly in a circumpolar long duration balloon mission during the polar night. Using the Earth as a giant solar shield, the instrument will spin in azimuth, observing a large fraction of the northern sky. The payload will host two instruments. An array of coherent polarimeters using cryogenic HEMT amplifiers will survey the sky at 43 and 90 GHz. An array of bolometric polarimeters, using large throughput multi-mode bolometers and rotating Half Wave Plates (HWP), will survey the same sky region in three bands at 95, 145 and 245 GHz. The wide frequency coverage will allow optimal control of the polarized foregrounds, with comparable angular resolution at all frequencies.

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arXiv2012

A coherent polarimeter array for the Large Scale Polarization Explorer balloon experiment

We discuss the design and expected performance of STRIP (STRatospheric Italian Polarimeter), an array of coherent receivers designed to fly on board the LSPE (Large Scale Polarization Explorer) balloon experiment. The STRIP focal plane array comprises 49 elements in Q band and 7 elements in W-band using cryogenic HEMT low noise amplifiers and high performance waveguide components. In operation, the array will be cooled to 20 K and placed in the focal plane of a $\sim 0.6$ meter telescope providing an angular resolution of $\sim1.5$ degrees. The LSPE experiment aims at large scale, high sensitivity measurements of CMB polarization, with multi-frequency deep measurements to optimize component separation. The STRIP Q-band channel is crucial to accurately measure and remove the synchrotron polarized component, while the W-band channel, together with a bolometric channel at the same frequency, provides a crucial cross-check for systematic effects.

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arXiv2012

Simultaneous Planck, Swift, and Fermi observations of X-ray and gamma-ray selected blazars

We present simultaneous Planck, Swift, Fermi, and ground-based data for 105 blazars belonging to three samples with flux limits in the soft X-ray, hard X-ray, and gamma-ray bands. Our unique data set has allowed us to demonstrate that the selection method strongly influences the results, producing biases that cannot be ignored. Almost all the BL Lac objects have been detected by Fermi-LAT, whereas ~40% of the flat-spectrum radio quasars (FSRQs) in the radio, soft X-ray, and hard X-ray selected samples are still below the gamma-ray detection limit even after integrating 27 months of Fermi-LAT data. The radio to sub-mm spectral slope of blazars is quite flat up to ~70GHz, above which it steepens to <α>~-0.65. BL Lacs have significantly flatter spectra than FSRQs at higher frequencies. The distribution of the rest-frame synchrotron peak frequency (\nupS) in the SED of FSRQs is the same in all the blazar samples with <\nupS>=10^13.1 Hz, while the mean inverse-Compton peak frequency, <\nupIC>, ranges from 10^21 to 10^22 Hz. The distributions of \nupS and of \nupIC of BL Lacs are much broader and are shifted to higher energies than those of FSRQs and strongly depend on the selection method. The Compton dominance of blazars ranges from ~0.2 to ~100, with only FSRQs reaching values >3. Its distribution is broad and depends strongly on the selection method, with gamma-ray selected blazars peaking at ~7 or more, and radio-selected blazars at values ~1, thus implying that the assumption that the blazar power is dominated by high-energy emission is a selection effect. Simple SSC models cannot explain the SEDs of most of the gamma-ray detected blazars in all samples. The SED of the blazars that were not detected by Fermi-LAT may instead be consistent with SSC emission. Our data challenge the correlation between bolometric luminosity and \nupS predicted by the blazar sequence.

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arXiv2011

Planck early results. III. First assessment of the Low Frequency Instrument in-flight performance

The scientific performance of the Planck Low Frequency Instrument (LFI) after one year of in-orbit operation is presented. We describe the main optical parameters and discuss photometric calibration, white noise sensitivity, and noise properties. A preliminary evaluation of the impact of the main systematic effects is presented. For each of the performance parameters, we outline the methods used to obtain them from the flight data and provide a comparison with pre-launch ground assessments, which are essentially confirmed in flight.

astro-ph.CO↗

arXiv2011

Planck Early Results. V. The Low Frequency Instrument data processing

We describe the processing of data from the Low Frequency Instrument (LFI) used in production of the Planck Early Release Compact Source Catalogue (ERCSC). In particular, we discuss the steps involved in reducing the data from telemetry packets to cleaned, calibrated, time-ordered data (TOD) and frequency maps. Data are continuously calibrated using the modulation of the temperature of the cosmic microwave background radiation induced by the motion of the spacecraft. Noise properties are estimated from TOD from which the sky signal has been removed using a generalized least square map-making algorithm. Measured 1/f noise knee-frequencies range from 100mHz at 30GHz to a few tens of mHz at 70GHz. A destriping code (Madam) is employed to combine radiometric data and pointing information into sky maps, minimizing the variance of correlated noise. Noise covariance matrices required to compute statistical uncertainties on LFI and Planck products are also produced. Main beams are estimated down to the approx -10dB level using Jupiter transits, which are also used for geometrical calibration of the focal plane.

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arXiv2011

The Simultaneous Medicina-Planck Experiment (SiMPlE): data acquisition, reduction and first results

The Simultaneous Medicina-{\it Planck} Experiment (SiMPlE) is aimed at observing a selected sample of 263 extragalactic and Galactic sources with the Medicina 32-m single dish radio telescope in the same epoch as the Planck satellite observations. The data acquired with a frequency coverage down to 5 GHz, also combined with Planck at frequencies above 30 GHz, will constitute a useful reference catalogue of bright sources over the whole Northern hemisphere. Furthermore, source observations performed in different epochs and comparison with other catalogues allow the investigation of source variabilities on different timescales. In this work, we describe the sample selection, the on-going data acquisition campaign, the data reduction procedures, the developed tools, and the comparison with other data-sets. We present the data at 5 and 8.3 GHz for the SiMPlE Northern Sample consisting of 79 sources with $δ\geq 45^\circ$ selected in our catalogue and observed during the first 6 months of the project. A first analysis of their spectral behaviour and long-term variability is also presented.

astro-ph.CO↗

arXiv2011

Effect of Fourier filters in removing periodic systematic effects from CMB data

We consider the application of high-pass Fourier filters to remove periodic systematic fluctuations from full-sky survey CMB datasets. We compare the filter performance with destriping codes commonly used to remove the effect of residual 1/f noise from timelines. As a realistic working case, we use simulations of the typical Planck scanning strategy and Planck Low Frequency Instrument noise performance, with spurious periodic fluctuations that mimic a typical thermal disturbance. We show that the application of Fourier high-pass filters in chunks always requires subsequent normalisation of induced offsets by means of destriping. For a complex signal containing all the astrophysical and instrumental components, the result obtained by applying filter and destriping in series is comparable to the result obtained by destriping only, which makes the usefulness of Fourier filters questionable for removing this kind of effects.

astro-ph.CO↗

arXiv2010

Planck pre-launch status: calibration of the Low Frequency Instrument flight model radiometers

The Low Frequency Instrument (LFI) on-board the ESA Planck satellite carries eleven radiometer subsystems, called Radiometer Chain Assemblies (RCAs), each composed of a pair of pseudo-correlation receivers. We describe the on-ground calibration campaign performed to qualify the flight model RCAs and to measure their pre-launch performances. Each RCA was calibrated in a dedicated flight-like cryogenic environment with the radiometer front-end cooled to 20K and the back-end at 300K, and with an external input load cooled to 4K. A matched load simulating a blackbody at different temperatures was placed in front of the sky horn to derive basic radiometer properties such as noise temperature, gain, and noise performance, e.g. 1/f noise. The spectral response of each detector was measured as was their susceptibility to thermal variation. All eleven LFI RCAs were calibrated. Instrumental parameters measured in these tests, such as noise temperature, bandwidth, radiometer isolation, and linearity, provide essential inputs to the Planck-LFI data analysis.

astro-ph.IM↗

arXiv2010

A systematic approach to the Planck LFI end-to-end test and its application to the DPC Level 1 pipeline

The Level 1 of the Planck LFI Data Processing Centre (DPC) is devoted to the handling of the scientific and housekeeping telemetry. It is a critical component of the Planck ground segment which has to strictly commit to the project schedule to be ready for the launch and flight operations. In order to guarantee the quality necessary to achieve the objectives of the Planck mission, the design and development of the Level 1 software has followed the ESA Software Engineering Standards. A fundamental step in the software life cycle is the Verification and Validation of the software. The purpose of this work is to show an example of procedures, test development and analysis successfully applied to a key software project of an ESA mission. We present the end-to-end validation tests performed on the Level 1 of the LFI-DPC, by detailing the methods used and the results obtained. Different approaches have been used to test the scientific and housekeeping data processing. Scientific data processing has been tested by injecting signals with known properties directly into the acquisition electronics, in order to generate a test dataset of real telemetry data and reproduce as much as possible nominal conditions. For the HK telemetry processing, validation software have been developed to inject known parameter values into a set of real housekeeping packets and perform a comparison with the corresponding timelines generated by the Level 1. With the proposed validation and verification procedure, where the on-board and ground processing are viewed as a single pipeline, we demonstrated that the scientific and housekeeping processing of the Planck-LFI raw data is correct and meets the project requirements.

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arXiv2010

Design, development, and verification of the Planck Low Frequency Instrument 70 GHz Front-End and Back-End Modules

70 GHz radiometer front-end and back-end modules for the Low Frequency Instrument of the European Space Agencys Planck Mission were built and tested. The operating principles and the design details of the mechanical structures are described along with the key InP MMIC low noise amplifiers and phase switches of the units. The units were tested in specially designed cryogenic vacuum chambers capable of producing the operating conditions required for Planck radiometers, specifically, a physical temperature of 20 K for the front-end modules, 300 K for the back-end modules and 4 K for the reference signal sources. Test results of the low noise amplifiers and phase switches, the front and back-end modules, and the combined results of both modules are discussed. At 70 GHz frequency, the system noise temperature of the front and back end is 28 K; the effective bandwidth 16 GHz, and the 1/f spectrum knee frequency is 38 mHz. The test results indicate state-of-the-art performance at 70 GHz frequency and fulfil the Planck performance requirements.

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arXiv2010

Noise Properties of the Planck-LFI Receivers

The Planck Low Frequency Instrument (LFI) radiometers have been tested extensively during several dedicated campaigns. The present paper reports the principal noise properties of the LFI radiometers.

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arXiv2010

The linearity response of the Planck-LFI flight model receivers

In this paper we discuss the linearity response of the Planck-LFI receivers, with particular reference to signal compression measured on the 30 and 44 GHz channels. In the article we discuss the various sources of compression and present a model that accurately describes data measured during tests performed with individual radiomeric chains. After discussing test results we present the best parameter set representing the receiver response and discuss the impact of non linearity on in-flight calibration, which is shown to be negligible.

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arXiv2010

Advanced modelling of the Planck-LFI radiometers

The Low Frequency Instrument (LFI) is a radiometer array covering the 30-70 GHz spectral range on-board the ESA Planck satellite, launched on May 14th, 2009 to observe the cosmic microwave background (CMB) with unprecedented precision. In this paper we describe the development and validation of a software model of the LFI pseudo-correlation receivers which enables to reproduce and predict all the main system parameters of interest as measured at each of the 44 LFI detectors. These include system total gain, noise temperature, band-pass response, non-linear response. The LFI Advanced RF Model (LARFM) has been constructed by using commercial software tools and data of each radiometer component as measured at single unit level. The LARFM has been successfully used to reproduce the LFI behavior observed during the LFI ground-test campaign. The model is an essential element in the database of LFI data processing center and will be available for any detailed study of radiometer behaviour during the survey.

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