179 research outputs found
Evaluation of night-time aerosols measurements and lunar irradiance models in the frame of the first multi-instrument nocturnal intercomparison campaign
The first multi-instrument nocturnal aerosol optical depth (AOD) intercom-parison campaign was held at the high-mountain Iza ̃na Observatory (Tener-ife, Spain) in June 2017, involving 2-minutes synchronous measurements fromtwo different types of lunar photometers (Cimel CE318-T and Moon Preci-sion Filter Radiometer, LunarPFR) and one stellar photometer. The Robotic Lunar Observatory (ROLO) model developed by the U.S. Geological Survey(USGS) was compared with the open-access ROLO Implementation for Moonphotometry Observation (RIMO) model. Results showed rather small differ-ences at Iza ̃na over a 2-month time period covering June and July, 2017(±0.01 in terms of AOD calculated by means of a day/night/day coherencetest analysis and±2 % in terms of lunar irradiance). The RIMO model hasbeen used in this field campaign to retrieve AOD from lunar photometricmeasurements. No evidence of significant differences with the Moon’s phase angle wasfound when comparing raw signals of the six Cimel photometers involved inthis field campaign.The raw signal comparison of the participating lunar photometers (Cimeland LunarPFR) performed at coincident wavelengths showed consistent mea-surements and AOD differences within their combined uncertainties at 870 nmand 675 nm. Slightly larger AOD deviations were observed at 500 nm, point-ing to some unexpected instrumental variations during the measurement pe-riod.Lunar irradiances retrieved using RIMO for phase angles varying between0◦and 75◦(full Moon to near quarter Moon) were compared to the irradi-ance variations retrieved by Cimel and LunarPFR photometers. Our resultsshowed a relative agreement within±3.5 % between the RIMO model andthe photometer-based lunar irradiances.The AOD retrieved by performing a Langley-plot calibration each nightshowed a remarkable agreement (better than 0.01) between the lunar pho-tometers. However, when applying the Lunar-Langley calibration using RIMO,AOD differences of up to 0.015 (0.040 for 500 nm) were found, with differ-ences increasing with the Moon’s phase angle. These differences are thoughtto be partly due to the uncertainties in the irradiance models, as well asinstrumental deficiencies yet to be fully understood.High AOD variability in stellar measurements was detected during thecampaign. Nevertheless, the observed AOD differences in the Cimel/stellarcomparison were within the expected combined uncertainties of these twophotometric techniques. Our results indicate that lunar photometry is amore reliable technique, especially for low aerosol loading conditions.The uncertainty analysis performed in this paper shows that the com-bined standard AOD uncertainty in lunar photometry is dependent on thecalibration technique (up to 0.014 for Langley-plot with illumination-basedcorrection, 0.012-0.022 for Lunar-Langley calibration, and up to 0.1 for the 2 Sun-Moon Gain Factor method). This analysis also corroborates that theuncertainty of the lunar irradiance model used for AOD calculation is withinthe 5-10 % expected range.This campaign has allowed us to quantify the important technical diffi-culties that still exist when routinely monitoring aerosol optical propertiesat night-time. The small AOD differences observed between the three typesof photometers involved in the campaign are only detectable under pristinesky conditions such as those found in this field campaign. Longer campaignsare necessary to understand the observed discrepancies between instrumentsas well as to provide more conclusive results about the uncertainty involvedin the lunar irradiance model
Sub-femto-g free fall for space-based gravitational wave observatories: LISA pathfinder results
We report the first results of the LISA Pathfinder in-flight experiment. The results demonstrate that two free-falling reference test masses, such as those needed for a space-based gravitational wave observatory like LISA, can be put in free fall with a relative acceleration noise with a square root of the power spectral density of 5.2 ± 0.1 fm s−2/√Hz or (0.54 ± 0.01) × 10−15 g/√Hz, with g the standard gravity, for frequencies between 0.7 and 20 mHz. This value is lower than the LISA Pathfinder requirement by more than a factor 5 and within a factor 1.25 of the requirement for the LISA mission, and is compatible with Brownian noise from viscous damping due to the residual gas surrounding the test masses. Above 60 mHz the acceleration noise is dominated by interferometer displacement readout noise at a level of (34.8 ± 0.3) fm/√Hz, about 2 orders of magnitude better than requirements. At f ≤ 0.5 mHz we observe a low-frequency tail that stays below 12 fm s−2/√Hz down to 0.1 mHz. This performance would allow for a space-based gravitational wave
observatory with a sensitivity close to what was originally foreseen for LISA
The Fluorescence Detector of the Pierre Auger Observatory
The Pierre Auger Observatory is a hybrid detector for ultra-high energy
cosmic rays. It combines a surface array to measure secondary particles at
ground level together with a fluorescence detector to measure the development
of air showers in the atmosphere above the array. The fluorescence detector
comprises 24 large telescopes specialized for measuring the nitrogen
fluorescence caused by charged particles of cosmic ray air showers. In this
paper we describe the components of the fluorescence detector including its
optical system, the design of the camera, the electronics, and the systems for
relative and absolute calibration. We also discuss the operation and the
monitoring of the detector. Finally, we evaluate the detector performance and
precision of shower reconstructions.Comment: 53 pages. Submitted to Nuclear Instruments and Methods in Physics
Research Section
Análise econômica da produção de Acacia mearnsii De Wild e carvão vegetal no Vale do Caí e Taquari, Rio Grande do Sul
Update on the correlation of the highest energy cosmic rays with nearby extragalactic matter
Data collected by the Pierre Auger Observatory through 31 August 2007 showed
evidence for anisotropy in the arrival directions of cosmic rays above the
Greisen-Zatsepin-Kuz'min energy threshold, \nobreak{eV}. The
anisotropy was measured by the fraction of arrival directions that are less
than from the position of an active galactic nucleus within 75 Mpc
(using the V\'eron-Cetty and V\'eron catalog). An updated
measurement of this fraction is reported here using the arrival directions of
cosmic rays recorded above the same energy threshold through 31 December 2009.
The number of arrival directions has increased from 27 to 69, allowing a more
precise measurement. The correlating fraction is , compared
with expected for isotropic cosmic rays. This is down from the early
estimate of . The enlarged set of arrival directions is
examined also in relation to other populations of nearby extragalactic objects:
galaxies in the 2 Microns All Sky Survey and active galactic nuclei detected in
hard X-rays by the Swift Burst Alert Telescope. A celestial region around the
position of the radiogalaxy Cen A has the largest excess of arrival directions
relative to isotropic expectations. The 2-point autocorrelation function is
shown for the enlarged set of arrival directions and compared to the isotropic
expectation.Comment: Accepted for publication in Astroparticle Physics on 31 August 201
Advanced functionality for radio analysis in the Offline software framework of the Pierre Auger Observatory
The advent of the Auger Engineering Radio Array (AERA) necessitates the
development of a powerful framework for the analysis of radio measurements of
cosmic ray air showers. As AERA performs "radio-hybrid" measurements of air
shower radio emission in coincidence with the surface particle detectors and
fluorescence telescopes of the Pierre Auger Observatory, the radio analysis
functionality had to be incorporated in the existing hybrid analysis solutions
for fluoresence and surface detector data. This goal has been achieved in a
natural way by extending the existing Auger Offline software framework with
radio functionality. In this article, we lay out the design, highlights and
features of the radio extension implemented in the Auger Offline framework. Its
functionality has achieved a high degree of sophistication and offers advanced
features such as vectorial reconstruction of the electric field, advanced
signal processing algorithms, a transparent and efficient handling of FFTs, a
very detailed simulation of detector effects, and the read-in of multiple data
formats including data from various radio simulation codes. The source code of
this radio functionality can be made available to interested parties on
request.Comment: accepted for publication in NIM A, 13 pages, minor corrections to
author list and references in v
Evidence for a mixed mass composition at the `ankle' in the cosmic-ray spectrum
We report a first measurement for ultra-high energy cosmic rays of the
correlation between the depth of shower maximum and the signal in the water
Cherenkov stations of air-showers registered simultaneously by the fluorescence
and the surface detectors of the Pierre Auger Observatory. Such a correlation
measurement is a unique feature of a hybrid air-shower observatory with
sensitivity to both the electromagnetic and muonic components. It allows an
accurate determination of the spread of primary masses in the cosmic-ray flux.
Up till now, constraints on the spread of primary masses have been dominated by
systematic uncertainties. The present correlation measurement is not affected
by systematics in the measurement of the depth of shower maximum or the signal
in the water Cherenkov stations. The analysis relies on general characteristics
of air showers and is thus robust also with respect to uncertainties in
hadronic event generators. The observed correlation in the energy range around
the `ankle' at differs significantly from
expectations for pure primary cosmic-ray compositions. A light composition made
up of proton and helium only is equally inconsistent with observations. The
data are explained well by a mixed composition including nuclei with mass . Scenarios such as the proton dip model, with almost pure compositions, are
thus disfavoured as the sole explanation of the ultrahigh-energy cosmic-ray
flux at Earth.Comment: Published version. Added journal reference and DOI. Added Report
Numbe
Search for First Harmonic Modulation in the Right Ascension Distribution of Cosmic Rays Detected at the Pierre Auger Observatory
We present the results of searches for dipolar-type anisotropies in different
energy ranges above eV with the surface detector array of
the Pierre Auger Observatory, reporting on both the phase and the amplitude
measurements of the first harmonic modulation in the right-ascension
distribution. Upper limits on the amplitudes are obtained, which provide the
most stringent bounds at present, being below 2% at 99% for EeV
energies. We also compare our results to those of previous experiments as well
as with some theoretical expectations.Comment: 28 pages, 11 figure
The rapid atmospheric monitoring system of the Pierre Auger Observatory
The Pierre Auger Observatory is a facility built to detect air showers produced by cosmic rays above 10(17) eV. During clear nights with a low illuminated moon fraction, the UV fluorescence light produced by air showers is recorded by optical telescopes at the Observatory. To correct the observations for variations in atmospheric conditions, atmospheric monitoring is performed at regular intervals ranging from several minutes (for cloud identification) to several hours (for aerosol conditions) to several days (for vertical profiles of temperature, pressure, and humidity). In 2009, the monitoring program was upgraded to allow for additional targeted measurements of atmospheric conditions shortly after the detection of air showers of special interest, e. g., showers produced by very high-energy cosmic rays or showers with atypical longitudinal profiles. The former events are of particular importance for the determination of the energy scale of the Observatory, and the latter are characteristic of unusual air shower physics or exotic primary particle types. The purpose of targeted (or 'rapid') monitoring is to improve the resolution of the atmospheric measurements for such events. In this paper, we report on the implementation of the rapid monitoring program and its current status. The rapid monitoring data have been analyzed and applied to the reconstruction of air showers of high interest, and indicate that the air fluorescence measurements affected by clouds and aerosols are effectively corrected using measurements from the regular atmospheric monitoring program. We find that the rapid monitoring program has potential for supporting dedicated physics analyses beyond the standard event reconstruction
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