Search results for "Remote sensing"

Software Timing Calibration of the ARGO-YBJ Detector

2009

The ARGO-YBJ experiment is mainly devoted to search for astronomical gamma sources. The arrival direction of air showers is reconstructed thanks to the times measured by the pixels of the detector. Therefore, the timing calibration of the detector pixels is crucial in order to get the best angular resolution and pointing accuracy. Because of the large number of pixels a hardware timing calibration is practically impossible. Therefore an off-line software calibration has been adopted. Here, the details of the procedure and the results are presented. (C) 2008 Elsevier B.V. All rights reserved.

On reference star recognition and identification

2014

The paper deals with a research in the area of automation of positional star observations. In order to fully employ recent progress in imaging technologies, star image recognition and reference star identification process should gain comparable level of automation. A software package for this purpose has been developed in the Institute of Geodesy of the University of Latvia. It is capable of near-real-time image processing, star identification and astrometric position determination.

The Joint SLR (Optical Range) and Radar-VLBI Satellite Observations using VIRAC Radio Telescope RT32, RT16 and SLR Station Riga

2020

Abstract Joint VLBI and SLR satellite tracking is a novel tracking approach to explore potential applications and to work out common procedures to coordinate observations between astronomical observatories in Latvia. Global Navigation Satellite System (GNSS) satellites equipped with laser retroreflectors have been chosen as test targets because they are accessible by both measuring techniques – satellite laser ranging (SLR) and Very Long Base Interferometry (VLBI). The first Joint SLR and VLBI observations of selected GNSS satellites using three of Latvian large-scale astronomical utilities – VIRAC radio telescopes RT32 and RT16 (Ventspils International Radio Astronomy Centre of Ventspils U…

Characterization of the global network of optical magnetometers to search for exotic physics (GNOME)

2018

The Global Network of Optical Magnetometers to search for Exotic physics (GNOME) is a network of geographically separated, time-synchronized, optically pumped atomic magnetometers that is being used to search for correlated transient signals heralding exotic physics. The GNOME is sensitive to nuclear- and electron-spin couplings to exotic fields from astrophysical sources such as compact dark-matter objects (for example, axion stars and domain walls). Properties of the GNOME sensors such as sensitivity, bandwidth, and noise characteristics are studied in the present work, and features of the network's operation (e.g., data acquisition, format, storage, and diagnostics) are described. Charac…

Simulations of Array Configurations for the Square Kilometre Array (SKA)

2010

The Square Kilometre Array (SKA) is a new generation radio telescope for the next decades, working at metre to centimetre wavelengths. The SKA will be operational at the same time than other new optical, X-ray and Gamma-ray telescopes. It is of extreme importance that the SKA becomes competitive and complementary to those instruments. An extensive study of technologies and possible configurations involved is needed to ensure the SKA will reach the design specifications. To compare imaging capabilities between different SKA configurations or between the SKA and other instruments, we have implemented figures of merit based on several characteristics of these instruments. In this work we are p…

Measurements of integrated direct, diffuse and global ultraviolet-B radiation

2015

Abstract We present the first multiyear set of simultaneous measurements of the global ultraviolet-B radiation and its two components: direct and diffuse. The measurements have been taken with four YES-UVB-1 radiometers: two radiometers to measure the diffuse radiation, one provided with a shadow band and the other with a shadow disk on a Sun tracker; a radiometer to measure the global horizontal radiation; and a Sun-tracking radiometer to measure the direct radiation with an especially designed radiance collimator. The diffuse minute-values measured with both instruments agree within a coefficient correlation of 1.00. The diffuse component represents at least 50% of the global UVB (ultravi…

2015

Advanced Astronomy for Heliophysics Plus (ADAHELI+) is a project concept for a small solar and space weather mission with a budget compatible with an European Space Agency (ESA) S-class mission, including launch, and a fast development cycle. ADAHELI+ was submitted to the European Space Agency by a European-wide consortium of solar physics research institutes in response to the "Call for a small mission opportunity for a launch in 2017," of March 9, 2012. The ADAHELI+ project builds on the heritage of the former ADAHELI mission, which had successfully completed its phase-A study under the Italian Space Agency 2007 Small Mission Programme, thus proving the soundness and feasibility of its in…

Linestrengths of the ν2 and ν4 bands of 12CH4 and 13CH4

1989

Absorption spectra recorded on the high-resolution Fourier transform spectrometer at Kitt Peak National Observatory/National Solar Observatory were used to measure individual line strengths of the nu(2) and nu(4) bands of (C-12)H4 and (C-13)H4. The measurements were used to obtain expressions that could be used to correctly predict individual line strengths through five orders of magnitude of absorption strength and high values of J-prime. Transition strengths were modeled using the dyad formalism of two interacting bands and a seven-term second-order dipole-moment expansion. The successful fitting of these data indicates that the method can be used to model measurements of 2- to 5-percent …

SphinX: The Solar Photometer in X-Rays

2012

Solar Photometer in X-rays (SphinX) was a spectrophotometer developed to observe the Sun in soft X-rays. The instrument observed in the energy range ≈ 1 – 15 keV with resolution ≈ 0.4 keV. SphinX was flown on the Russian CORONAS–PHOTON satellite placed inside the TESIS EUV and X telescope assembly. The spacecraft launch took place on 30 January 2009 at 13:30 UT at the Plesetsk Cosmodrome in Russia. The SphinX experiment mission began a couple of weeks later on 20 February 2009 when the first telemetry dumps were received. The mission ended nine months later on 29 November 2009 when data transmission was terminated. SphinX provided an excellent set of observations during very low solar activ…

Atmospheric turbulence in phase-referenced and wide-field interferometric images

2010

Phase referencing is a standard calibration procedure in radio interferometry. It allows us to detect weak sources by using quasisimultaneous observations of closeby sources acting as calibrators. However, atmospheric turbulence may introduce strong differences in the optical paths of the signals of the target and calibrator and affect, or even waste, phase referencing in cases of relatively large calibrator-to-target separations and/or bad weather. The situation is similar in wide-field interferometric observations. We present the results of a Monte Carlo study of the astrometric precision and sensitivity of an interferometric array (a realization of the Square Kilometre Array, SKA) in pha…