238 research outputs found
Optimization of Planck/LFI on--board data handling
To asses stability against 1/f noise, the Low Frequency Instrument (LFI)
onboard the Planck mission will acquire data at a rate much higher than the
data rate allowed by its telemetry bandwith of 35.5 kbps. The data are
processed by an onboard pipeline, followed onground by a reversing step. This
paper illustrates the LFI scientific onboard processing to fit the allowed
datarate. This is a lossy process tuned by using a set of 5 parameters Naver,
r1, r2, q, O for each of the 44 LFI detectors. The paper quantifies the level
of distortion introduced by the onboard processing, EpsilonQ, as a function of
these parameters. It describes the method of optimizing the onboard processing
chain. The tuning procedure is based on a optimization algorithm applied to
unprocessed and uncompressed raw data provided either by simulations, prelaunch
tests or data taken from LFI operating in diagnostic mode. All the needed
optimization steps are performed by an automated tool, OCA2, which ends with
optimized parameters and produces a set of statistical indicators, among them
the compression rate Cr and EpsilonQ. For Planck/LFI the requirements are Cr =
2.4 and EpsilonQ <= 10% of the rms of the instrumental white noise. To speedup
the process an analytical model is developed that is able to extract most of
the relevant information on EpsilonQ and Cr as a function of the signal
statistics and the processing parameters. This model will be of interest for
the instrument data analysis. The method was applied during ground tests when
the instrument was operating in conditions representative of flight. Optimized
parameters were obtained and the performance has been verified, the required
data rate of 35.5 Kbps has been achieved while keeping EpsilonQ at a level of
3.8% of white noise rms well within the requirements.Comment: 51 pages, 13 fig.s, 3 tables, pdflatex, needs JINST.csl, graphicx,
txfonts, rotating; Issue 1.0 10 nov 2009; Sub. to JINST 23Jun09, Accepted
10Nov09, Pub.: 29Dec09; This is a preprint, not the final versio
Thermal susceptibility of the Planck-LFI receivers
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/T1201
La paratubercolosi negli ovini e caprini I: prolegomeni allo studio delle cause predisponenti a questa malattia
La paratubercolosi, o enterite paratubercolare (conosciuta anche come malattia di Johne), è una patologia infettiva ad andamento cronico sostenuta da Mycobacterium avium subsp. paratuberculosis (MAP). È diffusa ovunque si pratichi l’allevamento ovino e caprino, rappresentando una delle malattie infettive più importanti per i danni arrecati agli allevamenti. Alla diffusione del MAP hanno contribuito specifici fattori gestionali, ma soprattutto la commercializzazione incontrollata di animali, con conseguente aumento dell’incidenza della malattia e prevalenza di allevamenti infetti ormai variabile tra il 7 ed il 60% su scala mondiale. In questo quadro si colloca il progetto PON “EpiSud-Programma per lo sviluppo di metodologie per l’identificazione ed il controllo di infezioni micobatteriche animali”, che vede il Parco Tecnologico Padano come proponente e l’Istituto Zooprofilattico della Sicilia nonché l’Università degli Studi di Bari Aldo Moro (DETO-Sez. Cliniche veterinarie e Produzioni Animali) in qualità di partner. L’Università di Bari, in particolare, sta conducendo un’indagine epidemiologica in Puglia su allevamenti estensivi ovini e caprini al fine di studiare la prevalenza della malattia ed i fattori di rischio scatenanti l’infezione in relazione alle pratiche gestionali adottate dagli allevatori. L’indagine è ancora in fieri ed è prematuro trarre conclusioni circa i dati epidemiologici; è tuttavia possibile, ancorché su dati parziali, avanzare ipotesi circa i fattori di rischio. Data la natura complessa di detti fattori, per l’analisi è stato scelto un approccio multivariato, cosicché nel presente lavoro si riportano i risultati dei primi dati raccolti mediante la somministrazione agli allevatori di un’apposita scheda aziendale, redatta al fine di reperire una serie di informazioni di carattere strutturale, igienico-sanitario e gestionale
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.Comment: this paper is part of the Prelaunch status LFI papers published on
JINST: http://www.iop.org/EJ/journal/-page=extra.proc5/jinst; 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
10.1088/1748-0221/4/12/T12011
Planck-LFI radiometers tuning
"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
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.Comment: 15 pages, 18 figures. Accepted for publication in Astronomy and
Astrophysic
Planck pre-launch status: Low Frequency Instrument calibration and expected scientific performance
We give the calibration and scientific performance parameters of the Planck
Low Frequency Instrument (LFI) measured during the ground cryogenic test
campaign. These parameters characterise the instrument response and constitute
our best pre-launch knowledge of the LFI scientific performance. The LFI shows
excellent stability and rejection of instrumental systematic effects;
measured noise performance shows that LFI is the most sensitive instrument of
its kind. The set of measured calibration parameters will be updated during
flight operations through the end of the mission.Comment: Accepted for publications in Astronomy and Astrophysics. Astronomy &
Astrophysics, 2010 (acceptance date: 12 Jan 2010
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