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1.
Background modelling for LEO satellites with high orbital inclination is not an easy task. The diffuse background component is dominated by the background coming from strong interactions with Earth magnetosphere trapped particles. Magnetic shielding is variable along the orbits and crosses through the SAA induce high radioactivity decay counting ratios. The aim of this paper is to present a model for the background total counting ratio of the 17 operative CdZnTe detectors on LEGRI in the short time scales and for observing periods outside crosses through SAA having enough time to cool LEGRI after the last SAA transit. Fluxes measured have been modelled in terms of the McIlwain parameter L using polynomial fits and exponential laws in terms of the geomagnetic cut-off rigidity used on COMPTEL background modelling. A discussion of the results is also included. 相似文献
2.
Julia Suso Pere Blay Almudena Robert Victor Reglero Chris J. Eyles 《Astrophysics and Space Science》2001,276(1):299-309
LEGRI has been operating successfully on MINISAT-01 since its switch-on the 22nd of May 1997. HouseKeeping (HK) data have been continuously receivedfor nearly two years by LEGRI SOC in Valencia, and subsequently checked on adaily basis and then stored for long term monitoring analysis.LEGRI HouseKeeping data include three critical operating parameters:temperature, power and polarisation voltages. Six temperature sensors arespread over the different LEGRI units: Detector Unit, Data Processing Unit,High Voltage Unit and Star Sensor. Voltages are measured at eight differentpoints. Detector Unit temperature and polarisation voltage are thecritical parameters for LEGRI operation. Solid state detectors aresensitive to changes not only in polarisation but also in temperature.Around one and a half million of measurements for each of the HK fourteen parameters have been recorded and analysed. The data show a very remarkablestability, within the expected margins, and the averages are very close to theoptimal design values. Special attention has been paid to the detectorpolarisation voltages analysis with a mean value of 286 ± 2 V when the detectors are operating. Thermal control over all the LEGRI units shows a remarkable stability in their temperatures.On the detector plane a mean value of T
det = 13 ± 2 °C has been found.We can therefore conclude that LEGRI as a system has been operating withinits optimal design conditions. We also want to point out the excellentperformance of the MINISAT-01 thermal control system. 相似文献
3.
Trapped protons are responsible for the main component of LEGRIbackground. Detailed theoretical model has demonstrated that theproton-induced counting rate is two orders of magnitude larger thanthe counting rate of the diffuse gamma-ray flux. The continuous passesof LEGRI through the SAA (7 times everyday) makes very difficult thebackground modelling. Long and short lived isotopes contribute in verydifferent time scales to the proton-induced background component.The goal of this paper is to present a comparison between the long-livedbackground noise theoretical predictions and the experimental data. Theresults show an unexpected good agreement between the predicted and theobserved counting rates. 相似文献
4.
C. Budtz-Jørgensen I. Kuvvetli N.J. Westergaard P. Jonasson V. Reglero C. Eyles T. Neubert 《Astrophysics and Space Science》2001,276(1):281-289
DSRI has initiated a development program of CZT X-ray and gamma raydetectors employing strip readout techniques. A dramatic improvement ofthe energy response was found operating the detectors as so-called driftdetectors. For the electronic readout, modern ASIC chips wereinvestigated. Modular design and the low power electronics will make largearea detectors using the drift strip method feasible. The performance of aprototype CZT system will be presented and discussed. One such detector system has been proposed for future space missions: TheX-Ray Imager (XRI) on the Atmospheric X-ray Observatory (AXO), whichis a mission proposed to the Danish Small Satellite Program and is dedicatedto observations of X-ray generating processes in the Earth's atmosphere. Ofspecial interest will be simultaneous optical and X-ray observations of spritesthat are flashes appearing directly above an active thunderstorm system.Additional objective is a detailed mapping of the auroral X-ray and opticalemission. XRI comprises a coded mask and a 20 cm × 40 cm CZTdetector array covering an energy range from 5 to 200 keV. 相似文献
5.
Gianpiero Tagliaferri A. Hornstrup J. Huovelin V. Reglero S. Romaine A. Rozanska A. Santangelo G. Stewart 《Experimental Astronomy》2012,34(2):463-488
Exploration of the X-ray sky has established X-ray astronomy as a fundamental astrophysical discipline. While our knowledge of the sky below 10?keV has increased dramatically (??8 orders of magnitude) by use of grazing incidence optics, we still await a similar improvement above 10?keV, where to date only collimated instruments have been used. Also ripe for exploration is the field of X-ray polarimetry, an unused fundamental tool to understand the physics and morphology of X-ray sources. Here we present a novel mission, the New Hard X-ray Mission (NHXM) that brings together for the first time simultaneous high-sensitivity, hard-X-ray imaging, broadband spectroscopy and polarimetry. NHXM will perform groundbreaking science in key scientific areas, including: black hole cosmic evolution, census and accretion physics; acceleration mechanism and non-thermal emission; physics of matter under extreme conditions. NHXM is designed specifically to address these topics via: broad 0.5?C80 (120) keV band for imaging and spectroscopy; 20?arcsec (15 goal) Half Energy Width (HEW) angular resolution at 30?keV; sensitivity limits more than 3 orders of magnitude better than those available in present day instruments; broadband (2?C35?keV) imaging polarimetry. In addition, NHXM has the ability to locate and actively monitor sources in different states of activity and to repoint within 1 to 2?h. This mission has been proposed to ESA in response to the Cosmic Vision M3 call. Its satellite configuration and payload subsystems were studied as part of previous national efforts permitting us to design a mature configuration that is compatible with a VEGA launch already by 2020. 相似文献
6.
Pere Blay Julia Suso Almudena Robert Jose Luis Requena Jorge Alamo Victor Reglero Chris J. Eyles 《Astrophysics and Space Science》2001,276(1):311-323
The LEGRI Science Operation Center (SOC) is the single contact pointbetween the MINISAT-01 Centro de Operaciones Científicas (COC)located at Villafranca del Castillo (Madrid) and the LEGRI Consortium.Its architecture, operational procedures and associated software hasbeen developed at the Universities of Valencia and Birmingham on thescope to define a integrated Data Analysis System, able to perform thedaily follow-up of the instrument health, raw data files decompressionand archiving activities (on-line and historical). Pointing and telecommandfiles generation is also a SOC responsibility.The aim of this paper is to report the SOC activities during the two yearsof LEGRI operations. Conclusions about the SOC architecture and proceduresevolution on how to handle the operations for space-borne instrumentation,are also presented.Special attention has been paid to the operative evaluation of the pointingreconstruction solutions from the MINISAT-01 Attitude Control System bycomparing them with those obtained with the LEGRI Star Sensor. The analysisof one year of observations shows the good agreement between both sets ofdata. No systematic deviations have been found with an averaged standarddeviation of 1 degree in alpha and delta coordinates. For most of the timethe MINISAT pointing system is working slightly better than expected andwithin specifications. 相似文献
7.
uvby
photometry has been done for early-type stars in the surroundings of the shell star Ori. The reddening maps show the presence of irregularly distributed absorbing material.Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain. 相似文献
8.
If we follow recent work and in order to extend theuvby photometric calibrations to spectral types later than G0, we present an attempt to use the combineduvby and systems for stars in the range G5-K7 and luminosity classes V to III.The behaviour in the MK-, (b–y)– and cl– diagrams of the 200 stars, only good spectroscopic data being considered, suggests the usefulness of the index as an independent parameter for late-type Main-Sequence stars, following in a natural way the general trend defined by Crawford for F- and G-type stars.Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain 相似文献
9.
J. M. Trigo-Rodríguez A. J. Castro-Tirado J. Llorca J. Fabregat V. J. Martínez V. Reglero M. Jelínek P. Kubánek T. Mateo A. de Ugarte Postigo 《Earth, Moon, and Planets》2004,95(1-4):553-567
We have developed an all-sky charge coupled devices (CCD) automatic system for detecting meteors and fireballs that will be
operative in four stations in Spain during 2005. The cameras were developed following the BOOTES-1 prototype installed at
the El Arenosillo Observatory in 2002, which is based on a CCD detector of 4096 × 4096 pixels with a fish-eye lens that provides
an all-sky image with enough resolution to make accurate astrometric measurements. Since late 2004, a couple of cameras at
two of the four stations operate for 30 s in alternate exposures, allowing 100% time coverage. The stellar limiting magnitude
of the images is +10 in the zenith, and +8 below ~ 65° of zenithal angle. As a result, the images provide enough comparison
stars to make astrometric measurements of faint meteors and fireballs with an accuracy of ~ 2°arcminutes. Using this prototype,
four automatic all-sky CCD stations have been developed, two in Andalusia and two in the Valencian Community, to start full
operation of the Spanish Fireball Network. In addition to all-sky coverage, we are developing a fireball spectroscopy program
using medium field lenses with additional CCD cameras. Here we present the first images obtained from the El Arenosillo and
La Mayora stations in Andalusia during their first months of activity. The detection of the Jan 27, 2003 superbolide of ±
17 ± 1 absolute magnitude that overflew Algeria and Morocco is an example of the detection capability of our prototype. 相似文献
10.
Herbert W. Schnopper Eric Silver Stephen Murray Suzanne Romaine Simon Bandler Christine Jones William Forman Norman Madden Jeffery Beeman Eugene Haller Finn Christensen Niels Westergaard Juan Fabregat Victor Reglero Alvaro Gimenez Noah Brosch Elia Liebowitz Hagai Netzer Marco Barbera Alfonso Collura Salvatore Sciortino 《Astrophysics and Space Science》2001,276(1):49-65
The X-Ray Spectroscopic Explorer (XRASE) has a unique combination of features that will make it possible to address many of NASA's scientific goals. These include how galaxy clusters form, the physics and chemistry of the ISM, the heating of stellar coronae, the amount and content of intergalactic baryonic matter, the mass of black holes and the formation of disks and jets in AGN and galactic binaries. XRASE has a thin foil, multilayered telescope with a large collecting area up to 10 keV, especially in the Fe K region (1100 cm2). Its microcalorimeter array combines high energy resolution (7 eV at 6 keV) and efficiency with a field-of-view of 26 arcmin2 . A deep orbit allows for long, continuous observations. Monitoring instruments in the optical (WOM-X), UV (TAUVEX) and hard X-RAY (GRAM) bands will offer exceptional opportunities to make simultaneous multi-wavelength observations. 相似文献