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H. Oleak 《Astronomische Nachrichten》1979,300(4):220-221
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The High Energy Stereoscopic System (H.E.S.S.) is a system of Imaging Atmospheric Cherenkov Telescopes (IACTs) located in the Khomas Highland in Namibia. It measures cosmic gamma rays of very high energies (VHE; >100 GeV) using the Earth’s atmosphere as a calorimeter. The H.E.S.S. Array entered Phase II in September 2012 with the inauguration of a fifth telescope that is larger and more complex than the other four. This paper will give an overview of the current H.E.S.S. central data acquisition (DAQ) system with particular emphasis on the upgrades made to integrate the fifth telescope into the array. At first, the various requirements for the central DAQ are discussed then the general design principles employed to fulfil these requirements are described. Finally, the performance, stability and reliability of the H.E.S.S. central DAQ are presented. One of the major accomplishments is that less than 0.8% of observation time has been lost due to central DAQ problems since 2009. 相似文献
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A new method of total ozone retrieval from i.r. satellite data(NOAA6) is presented. It uses ozone transmittance as a predictor of total ozone. Ozone transmittance at 9.6 μm(TR) is deduced from radiance at 9.6 μm(R9), surface temperature (TS) measured at 11 μm, and ozone mean temperature (TE) estimated from several channels (among them 9.6 μm) by the radiative transfer equation : R9 = B(TS) × TR + (1?TR) × B(TE) where B is the Planck function.A statistical analysis of the retrieved ozone field and a comparison with ground based measurements show that the S.E. is less than 5% for the considered data set. 相似文献
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Mathieu de Naurois 《Astrophysics and Space Science》2007,309(1-4):277-284
Recent observations of the binary system LS 5039 with the High Energy Stereoscopic System (H.E.S.S.) revealed that its Very
High Energy (VHE) γ-ray emission is modulated at the 3.9 days orbital period of the system. The bulk of the emission is largely confined to half
of the orbit, peaking around the inferior conjunction epoch of the compact object. The flux modulation provides the first
indication of γ-ray absorption by pair production on the intense stellar photon field. This implies that the production region size must
be not significantly greater than the gamma-gamma photosphere size (∼1 AU), thus excluding the large scale collimated outflows
or jets (extending out to ∼1000 AU). A hardening of the spectrum is also observed at the same epoch between 0.2 and a few
TeV which is unexpected under a pure absorption scenario and could rather arise from variation with phase in the maximum electron
energy and/or the dominant VHE γ-ray production mechanism. This first-time observation of modulated γ-ray emission allows precise tests of the acceleration and emission models in binary systems.
Mathieu de Naurois for the H.E.S.S. Collaboration. 相似文献
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