M. Lapolla

University of Milan, Milano, Lombardy, Italy

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Publications (15)12.12 Total impact

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    ABSTRACT: "This paper is part of the Prelaunch status LFI papers published on JINST: http://www.iop.org/EJ/journal/-page=extra.proc5/jinst" This paper describes the Planck Low Frequency Instrument tuning activities performed through the ground test campaigns, from Unit to Satellite Levels. Tuning is key to achieve the best possible instrument performance and tuning parameters strongly depend on thermal and electrical conditions. For this reason tuning has been repeated several times during ground tests and it has been repeated in flight before starting nominal operations. The paper discusses the tuning philosophy, the activities and the obtained results, highlighting developments and changes occurred during test campaigns. The paper concludes with an overview of tuning performed during the satellite cryogenic test campaign (Summer 2008) and of the plans for the just started in-flight calibration. Comment: This is an author-created, un-copyedited version of an article accepted for publication in JINST. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The definitive publisher authenticated version is available online at http://dx.doi.org/10.1088/1748-0221/4/12/T12013]
    01/2010;
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    ABSTRACT: This paper is part of the Prelaunch status LFI papers published on JINST: http://www.iop.org/EJ/journal/-page=extra.proc5/jinst . This paper describes the impact of the Planck Low Frequency Instrument front end physical temperature fluctuations on the output signal. The origin of thermal instabilities in the instrument are discussed, and an analytical model of their propagation and impact on the receivers signal is described. The experimental test setup dedicated to evaluate these effects during the instrument ground calibration is reported together with data analysis methods. Finally, main results obtained are discussed and compared to the requirements. Comment: This is an author-created, un-copyedited version of an article accepted for publication in Journal of Instrumentation. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The definitive publisher authenticated version is available online at 10.1088/1748-0221/4/12/T12012
    Journal of Instrumentation 01/2010; · 1.53 Impact Factor
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    ABSTRACT: The Low Frequency Instrument (LFI) is an array of cryogenically cooled radiometers on board the Planck satellite, designed to measure the temperature and polarization anisotropies of the cosmic microwave backgrond (CMB) at 30, 44 and 70 GHz. The thermal requirements of the LFI, and in particular the stringent limits to acceptable thermal fluctuations in the 20 K focal plane, are a critical element to achieve the instrument scientific performance. Thermal tests were carried out as part of the on-ground calibration campaign at various stages of instrument integration. In this paper we describe the results and analysis of the tests on the LFI flight model (FM) performed at Thales Laboratories in Milan (Italy) during 2006, with the purpose of experimentally sampling the thermal transfer functions and consequently validating the numerical thermal model describing the dynamic response of the LFI focal plane. This model has been used extensively to assess the ability of LFI to achieve its scientific goals: its validation is therefore extremely important in the context of the Planck mission. Our analysis shows that the measured thermal properties of the instrument show a thermal damping level better than predicted, therefore further reducing the expected systematic effect induced in the LFI maps. We then propose an explanation of the increased damping in terms of non-ideal thermal contacts. Comment: Planck LFI technical papers published by JINST: http://www.iop.org/EJ/journal/-page=extra.proc5/1748-0221
    Journal of Instrumentation 01/2010; · 1.53 Impact Factor
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    ABSTRACT: This paper is part of the Prelaunch status LFI papers published on JINST (http://www.iop.org/EJ/journal/-page=extra.proc5/1748-0221). Planck's Low Frequency Instrument is an array of 22 pseudo-correlation radiometers at 30, 44, and 70 GHz. Before integrating the overall array assembly, a first set of tests has been performed for each radiometer chain assembly (RCA), consisting of two radiometers. In this paper, we describe Rachel, a software application which has been purposely developed and used during the RCA test campaign to carry out both near-realtime on-line data analysis and data storage (in FITS format) of the raw output from the radiometric chains. Comment: This is an author-created, un-copyedited version of an article accepted for publication in JINST. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The definitive publisher authenticated version is available online at http://dx.doi.org/10.1088/1748-0221/4/12/T12017
    Journal of Instrumentation 01/2010; · 1.53 Impact Factor
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    ABSTRACT: The European Space Agency's Planck satellite, launched on 14 May 2009, is the third-generation space experiment in the field of cosmic microwave background (CMB) research. It will image the anisotropies of the CMB over the whole sky, with unprecedented sensitivity (Delta T/T similar to 2 x 10(-6)) and angular resolution (similar to 5 arcmin). Planck will provide a major source of information relevant to many fundamental cosmological problems and will test current theories of the early evolution of the Universe and the origin of structure. It will also address a wide range of areas of astrophysical research related to the Milky Way as well as external galaxies and clusters of galaxies. The ability of Planck to measure polarization across a wide frequency range (30-350 GHz), with high precision and accuracy, and over the whole sky, will provide unique insight, not only into specific cosmological questions, but also into the properties of the interstellar medium. This paper is part of a series which describes the technical capabilities of the Planck scientific payload. It is based on the knowledge gathered during the on-ground calibration campaigns of the major subsystems, principally its telescope and its two scientific instruments, and of tests at fully integrated satellite level. It represents the best estimate before launch of the technical performance that the satellite and its payload will achieve in flight. In this paper, we summarise the main elements of the payload performance, which is described in detail in the accompanying papers. In addition, we describe the satellite performance elements which are most relevant for science, and provide an overview of the plans for scientific operations and data analysis.
    Astronomy and Astrophysics. 01/2010;
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    ABSTRACT: This paper describes the Planck Low Frequency Instrument tuning activities performed through the ground test campaigns, from Unit to Satellite Levels. Tuning is key to achieve the best possible instrument performance and tuning parameters strongly depend on thermal and electrical conditions. For this reason tuning has been repeated several times during ground tests and it has been repeated in flight before starting nominal operations. The paper discusses the tuning philosophy, the activities and the obtained results, highlighting developments and changes occurred during test campaigns. The paper concludes with an overview of tuning performed during the satellite cryogenic test campaign (Summer 2008) and of the plans for the just started in-flight calibration.
    Journal of Instrumentation 12/2009; 4(12):T12013. · 1.53 Impact Factor
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    ABSTRACT: The Planck LFI Radiometer Chain Assemblies (RCAs) have been calibrated in two dedicated cryogenic facilities. In this paper the facilities and the related instrumentation are described. The main satellite thermal interfaces for the single chains have to be reproduced and stability requirements have to be satisfied. Setup design, problems occurred and improving solutions implemented are discussed. Performance of the cryogenic setup are reported.
    Journal of Instrumentation 12/2009; 4(12):T12015. · 1.53 Impact Factor
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    ABSTRACT: The ESA Planck mission is the third generation (after COBE and WMAP) space experiment dedicated to the measurement of the Cosmic Microwave Background (CMB) anisotropies. Two instruments will be integrated onboard: the High Fre-quency Instrument (HFI), an array of bolometers, and the Low Frequency Instrument (LFI), an array of pseudo-correlation HEMT radiometers.
    Proceedings of SPIE - The International Society for Optical Engineering 07/2006; · 0.20 Impact Factor
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    ABSTRACT: The ESA Planck mission is the third generation (after COBE and WMAP) space experiment dedicated to the measurement of the Cosmic Microwave Background (CMB) anisotropies. Planck will map the whole CMB sky using two instruments in the focal plane of a 1.5 m off-axis aplanatic telescope. The High Frequency Instrument (HFI) is an array of 52 bolometers in the frequency range 100-857 GHz, while the Low Frequency Instrument (LFI) is an array of 11 pseudo-correlation radiometric receivers which continuously compare the sky signal with the reference signal of a blackbody at ~ 4.5 K. The LFI has been tested and calibrated at different levels of integration, i.e. on the single units (feed-horns, OMTs, amplifiers, waveguides, etc.), on each integrated Radiometric Chain Assembly (RCA) and finally on the complete instrument, the Radiometric Array Assembly (RAA). In this paper we focus on some of the data analysis algorithms and methods that have been implemented to estimate the instrument performance and calibration parameters. The paper concludes with the discussion of a custom-designed software package (LIFE) that allows to access the complex data structure produced by the instrument and to estimate the instrument performance and calibration parameters via a fully graphical interface.
    Proceedings of SPIE - The International Society for Optical Engineering 07/2006; · 0.20 Impact Factor
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    ABSTRACT: The ESA Planck satellite is designed to achieve precision imaging of the Cosmic Microwave Background with an unprecedented combination of angular resolution, sensitivity, spectral range and sky coverage. The Low Frequency Instrument is one of two complementary instruments, and covers 30, 44, and 70 GHz with an array of wideband pseudo-correlation, cryogenic radiometers. Advanced qualification models of the radiometer chains and of the instrument electronics have been manufactured, tested and integrated into the LFI Qualification Model. The main radiometer calibration, RF tuning and performance characterization is carried out at a single radiometer chain level, and then verified at instrument integrated level in dedicated cryofacilities. Here we describe the main requirements and instrument design, and we summarize the radiometer calibration strategy optimised during the qualification activity in view of the LFI Flight Model campaign.
    08/2005; -1:189-195.
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    ABSTRACT: Construction of the first stage of the Pierre Auger Observatory has begun. The aim of the Observatory is to collect unprecedented information about cosmic rays above . The first phase of the project, the construction and operation of a prototype system, known as the engineering array, has now been completed. It has allowed all of the sub-systems that will be used in the full instrument to be tested under field conditions. In this paper, the properties and performance of these sub-systems are described and their success illustrated with descriptions of some of the events recorded thus far.
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 05/2004; · 1.32 Impact Factor
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    ABSTRACT: The fluorescence detector of the Pierre Auger Cosmic Ray Observatory will provide a measurement of the parameters of extended air showers in the range from 10<sup>19</sup> to 10<sup>21</sup> eV. An array of 20×22 photomultiplier tubes (PMTs) is placed at the focal surface of a large-aperture telescope thus forming one of the 30 detector modules. The shape of the signal generated by each PMT is variable, depending mostly on the geometry of the air shower as seen by the detector; after analog processing the waveforms will be sampled at a rate of 10 MHz with 12 bit resolution. We have developed an analog signal processor to achieve the best compromise between energy and time resolution, low noise, and low cost. The head electronics provides an active bias network for the PMTs, which keeps the gain constant even in the presence of large dc background light from the night sky. This dc level is measured by means of a built-in optocoupled linear circuit. The pulse signal is sent through a twisted pair to the analog front-end board. At this stage a compression of the 15-bit dynamic range of the signal into the 12-bit range of the FADC is performed. Antialiasing is provided by a Bessel filter
    IEEE Transactions on Nuclear Science 07/2001; · 1.46 Impact Factor
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    ABSTRACT: The Auger Fluorescence Detector will allow to determine the longitudinal development of atmospheric showers in the range 1019–. A detector module comprises an array of 20×22 PMTs at the focal surface of a large-aperture telescope. Thirty such modules will be used. The PMTs pixel signal is variable in shape depending on the shower-eye geometry. The sky background light (BL) is also variable. We have developed an analog signal processor to obtain best energy and timing resolution despite those constrains. The Head Electronics (HE) bias the PMTs and keeps its pulse-gain constant even for large BL. This is measured using a current-monitor of novel design. Both the signal pulse and the BL DC level are sent via a single twisted pair to the Analog Board (AB). The AB performs the compression of the 15–16 bit signal dynamic range into 12 bits of the FADC which follows the AB. A three-pole Bessel filter was adopted for antialiasing. The AB includes 16 bit sigma-delta chips to readout the BL DC level, and a test-pulse distribution system.
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 09/2000; · 1.32 Impact Factor
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    ABSTRACT: The fluorescence detector of the Pierre Auger Cosmic Ray Observatory will provide a measurement of the parameters of extended air showers in the range from 10<sup>19</sup> eV to 10<sup>21</sup> eV. An array of 20×22 PMT's is placed at the focal surface of a large-aperture telescope thus forming one of the 30 detector modules. The shape of the signal generated by each PMT is variable, depending mostly on the geometry of the air shower as seen by the detector; after analog processing the waveforms will be sampled at a rate of 10 MHz with 12 bit resolution. We have developed an analog signal processor to achieve best energy and time resolution, low noise and low cost. The head electronics provides an active bias network for the PMT's, which keeps the gain constant even in presence of large DC background light from the night sky: this DC level is measured by means of a built-in optocoupled linear circuit
    Nuclear Science Symposium Conference Record, 2000 IEEE; 02/2000
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    http://dx.doi.org/10.1051/0004-6361/200912983.