215 research outputs found
Software Technologies:12th International Joint Conference, ICSOFT 2017, Madrid, Spain, July 24-26, 2017, Revised Selected Papers
Euclid space mission: a cosmological challenge for the next 15 years
Euclid is the next ESA mission devoted to cosmology. It aims at observing
most of the extragalactic sky, studying both gravitational lensing and
clustering over 15,000 square degrees. The mission is expected to be
launched in year 2020 and to last six years. The sheer amount of data of
different kinds, the variety of (un)known systematic effects and the complexity
of measures require efforts both in sophisticated simulations and techniques of
data analysis. We review the mission main characteristics, some aspects of the
the survey and highlight some of the areas of interest to this meetingComment: to appear in Proceedings IAU Symposium No. 306, 2014, "Statistical
Challenges in 21st Century Cosmology", A.F. Heavens, J.-L. Starck & A.
Krone-Martins, ed
In-flight calibration and verification of the Planck-LFI instrument
In this paper we discuss the Planck-LFI in-flight calibration campaign. After
a brief overview of the ground test campaigns, we describe in detail the
calibration and performance verification (CPV) phase, carried out in space
during and just after the cool-down of LFI. We discuss in detail the
functionality verification, the tuning of the front-end and warm electronics,
the preliminary performance assessment and the thermal susceptibility tests.
The logic, sequence, goals and results of the in-flight tests are discussed.
All the calibration activities were successfully carried out and the instrument
response was comparable to the one observed on ground. For some channels the
in-flight tuning activity allowed us to improve significantly the noise
performance.Comment: Long technical paper on Planck LFI in flight calibration campaign:
109 pages in this (not final) version, 100 page in the final JINST versio
A conceptual modeling methodology based on niches and granularity
This paper presents a methodology for conceptual modeling which is based on a new modeling primitive, the niche, and associated constructs granularity and reconciliation. A niche is an environment where entities interact for a specific purpose, playing specific roles, and according to the norms and constraints of that environment. Granularity refers to the relative level of power or influence of an entity within a niche. Reconciliation is a relationship from N entities onto one reconciled entity, and represents explicitly a situation where two or more different perspectives of the same entity have been reconciled, by negotiation, into a single consensus view. The methodology we propose provides a systematic method of designing conceptual models along with a process for normalising inappropriate relationships. Normalising is a prescriptive process for identifying and remedying inconsistencies within a model based on granularities. Drawing on a number of case studies, we show how niches and granularity make complexity easier to manage, highlight inaccuracies in a model, identify opportunities for achieving project goals, and reduce semantic heterogeneity
Planck early results: first assessment of the High Frequency Instrument in-flight performance
The Planck High Frequency Instrument (HFI) is designed to measure the
temperature and polarization anisotropies of the Cosmic Microwave Background
and galactic foregrounds in six wide bands centered at 100, 143, 217, 353, 545
and 857 GHz at an angular resolution of 10' (100 GHz), 7' (143 GHz), and 5'
(217 GHz and higher). HFI has been operating flawlessly since launch on 14 May
2009. The bolometers cooled to 100 mK as planned. The settings of the readout
electronics, such as the bolometer bias current, that optimize HFI's noise
performance on orbit are nearly the same as the ones chosen during ground
testing. Observations of Mars, Jupiter, and Saturn verified both the optical
system and the time response of the detection chains. The optical beams are
close to predictions from physical optics modeling. The time response of the
detection chains is close to pre-launch measurements. The detectors suffer from
an unexpected high flux of cosmic rays related to low solar activity. Due to
the redundancy of Planck's observations strategy, the removal of a few percent
of data contaminated by glitches does not affect significantly the sensitivity.
The cosmic rays heat up significantly the bolometer plate and the modulation on
periods of days to months of the heat load creates a common drift of all
bolometer signals which do not affect the scientific capabilities. Only the
high energy cosmic rays showers induce inhomogeneous heating which is a
probable source of low frequency noise.Comment: Submitted to A&A. 22 pages, 6 tables, 21 figures. One of a set of
simultaneous papers for the Planck Missio
Concept design of low frequency telescope for CMB B-mode polarization satellite LiteBIRD
LiteBIRD has been selected as JAXAâs strategic large mission in the 2020s, to observe the cosmic microwave background (CMB) B-mode polarization over the full sky at large angular scales. The challenges of LiteBIRD are the wide field-of-view (FoV) and broadband capabilities of millimeter-wave polarization measurements, which are derived from the system requirements. The possible paths of stray light increase with a wider FoV and the far sidelobe knowledge of -56 dB is a challenging optical requirement. A crossed-Dragone configuration was chosen for the low frequency telescope (LFT : 34â161 GHz), one of LiteBIRDâs onboard telescopes. It has a wide field-of-view (18° x 9°) with an aperture of 400 mm in diameter, corresponding to an angular resolution of about 30 arcminutes around 100 GHz. The focal ratio f/3.0 and the crossing angle of the optical axes of 90⊠are chosen after an extensive study of the stray light. The primary and secondary reflectors have rectangular shapes with serrations to reduce the diffraction pattern from the edges of the mirrors. The reflectors and structure are made of aluminum to proportionally contract from warm down to the operating temperature at 5 K. A 1/4 scaled model of the LFT has been developed to validate the wide field-of-view design and to demonstrate the reduced far sidelobes. A polarization modulation unit (PMU), realized with a half-wave plate (HWP) is placed in front of the aperture stop, the entrance pupil of this system. A large focal plane with approximately 1000 AlMn TES detectors and frequency multiplexing SQUID amplifiers is cooled to 100 mK. The lens and sinuous antennas have broadband capability. Performance specifications of the LFT and an outline of the proposed verification plan are presented
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Planck early results II : The thermal performance of Planck
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