Search results for "Astrophysics - Instrumentation and Methods"
showing 10 items of 215 documents
Techniques for measuring aerosol attenuation using the Central Laser Facility at the Pierre Auger Observatory
2013
The Pierre Auger Observatory in Malargue, Argentina, is designed to study the properties of ultra-high energy cosmic rays with energies above 10(18) eV. It is a hybrid facility that employs a Fluorescence Detector to perform nearly calorimetric measurements of Extensive Air Shower energies. To obtain reliable calorimetric information from the FD, the atmospheric conditions at the observatory need to be continuously monitored during data acquisition. In particular, light attenuation due to aerosols is an important atmospheric correction. The aerosol concentration is highly variable, so that the aerosol attenuation needs to be evaluated hourly. We use light from the Central Laser Facility, lo…
The FRAM robotic telescope for atmospheric monitoring at the Pierre Auger Observatory
2021
FRAM (F/Photometric Robotic Atmospheric Monitor) is a robotic telescope operated at the Pierre Auger Observatory in Argentina for the purposes of atmospheric monitoring using stellar photometry. As a passive system which does not produce any light that could interfere with the observations of the fluorescence telescopes of the observatory, it complements the active monitoring systems that use lasers. We discuss the applications of stellar photometry for atmospheric monitoring at optical observatories in general and the particular modes of operation employed by the Auger FRAM. We describe in detail the technical aspects of FRAM, the hardware and software requirements for a successful operati…
Performance Analysis of the SO/PHI Software Framework for On-board Data Reduction
2019
The Polarimetric and Helioseismic Imager (PHI) is the first deep-space solar spectropolarimeter, on-board the Solar Orbiter (SO) space mission. It faces: stringent requirements on science data accuracy, a dynamic environment, and severe limitations on telemetry volume. SO/PHI overcomes these restrictions through on-board instrument calibration and science data reduction, using dedicated firmware in FPGAs. This contribution analyses the accuracy of a data processing pipeline by comparing the results obtained with SO/PHI hardware to a reference from a ground computer. The results show that for the analyzed pipeline the error introduced by the firmware implementation is well below the requirem…
Structure of Small Magnetic Elements in the Solar Atmosphere
2012
High resolution images at different wavelengths, spectrograms and magnetograms, representing different levels of the solar atmosphere obtained with Hinode have been combined to study the 3-dimensional structure of the small magnetic elements in relation to their radiance. A small magnetic element is described as example of the study.
Observations of vortex motion in the solar photosphere using HINODE-SP data
2012
In this work, we focus in the magnetic evolution of a small region as seen by Hinode-SP during the time interval of about one hour. High-cadence LOS magnetograms and velocity maps were derived, allowing the study of different small-scale processes such as the formation/disappearance of bright points accompanying the evolution of an observed convective vortical motion.
High magnetic fields for fundamental physics
2018
Various fundamental-physics experiments such as measurement of the birefringence of the vacuum, searches for ultralight dark matter (e.g., axions), and precision spectroscopy of complex systems (including exotic atoms containing antimatter constituents) are enabled by high-field magnets. We give an overview of current and future experiments and discuss the state-of-the-art DC- and pulsed-magnet technologies and prospects for future developments.
Atmospheric turbulence in phase-referenced and wide-field interferometric images: Application to the SKA
2010
Phase referencing is a standard calibration procedure in radio interferometry. It allows to detect weak sources by using quasi-simultaneous observations of closeby sources acting as calibrators. Therefore, it is assumed that, for each antenna, the optical paths of the signals from both sources are similar. However, atmospheric turbulence may introduce strong differences in the optical paths of the signals and affect, or even waste, phase referencing for cases of relatively large calibrator-to-target separations and/or bad weather. The situation is similar in wide-field observations, since the random deformations of the images, mostly caused by atmospheric turbulence, have essentially the sa…
On the coherence loss in phase-referenced VLBI observations
2010
Context: Phase referencing is a standard calibration technique in radio interferometry, particularly suited for the detection of weak sources close to the sensitivity limits of the interferometers. However, effects from a changing atmosphere and inaccuracies in the correlator model may affect the phase-referenced images, leading to wrong estimates of source flux densities and positions. A systematic observational study of signal decoherence in phase referencing, and its effects in the image plane, has not been performed yet. Aims: We systematically studied how the signal coherence in Very-Long-Baseline-Interferometry (VLBI) observations is affected by a phase-reference calibration at differ…
Origin of atmospheric aerosols at the Pierre Auger Observatory using studies of air mass trajectories in South America
2014
The Pierre Auger Observatory is making significant contributions towards understanding the nature and origin of ultra-high energy cosmic rays. One of its main challenges is the monitoring of the atmosphere, both in terms of its state variables and its optical properties. The aim of this work is to analyze aerosol optical depth $\tau_{\rm a}(z)$ values measured from 2004 to 2012 at the observatory, which is located in a remote and relatively unstudied area of the Pampa Amarilla, Argentina. The aerosol optical depth is in average quite low - annual mean $\tau_{\rm a}(3.5~{\rm km})\sim 0.04$ - and shows a seasonal trend with a winter minimum - $\tau_{\rm a}(3.5~{\rm km})\sim 0.03$ -, and a sum…
A Precise Photometric Ratio via Laser Excitation of the Sodium Layer II: Two-photon Excitation Using Lasers Detuned from 589.16 nm and 819.71 nm Reso…
2020
This article is the second in a pair of articles on the topic of the generation of a two-color artificial star (which we term a "laser photometric ratio star," or LPRS) of de-excitation light from neutral sodium atoms in the mesosphere, for use in precision telescopic measurements in astronomy and atmospheric physics, and more specifically for the calibration of measurements of dark energy using type Ia supernovae. The two techniques respectively described in both this and the previous article would each generate an LPRS with a precisely 1:1 ratio of yellow (589/590 nm) photons to near-infrared (819/820 nm) photons produced in the mesosphere. Both techniques would provide novel mechanisms f…