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The Fermi Large Area Telescope on Orbit: Event Classification, Instrument Response Functions, and Calibration

Ackermann, M. and Siegal-Gaskins, J. (2012) The Fermi Large Area Telescope on Orbit: Event Classification, Instrument Response Functions, and Calibration. Astrophysical Journal Supplement Series, 203 (1). Art. No. 4. ISSN 0067-0049. doi:10.1088/0067-0049/203/1/4.

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The Fermi Large Area Telescope (Fermi-LAT, hereafter LAT), the primary instrument on the Fermi Gamma-ray Space Telescope (Fermi) mission, is an imaging, wide field-of-view, high-energy γ-ray telescope, covering the energy range from 20 MeV to more than 300 GeV. During the first years of the mission, the LAT team has gained considerable insight into the in-flight performance of the instrument. Accordingly, we have updated the analysis used to reduce LAT data for public release as well as the instrument response functions (IRFs), the description of the instrument performance provided for data analysis. In this paper, we describe the effects that motivated these updates. Furthermore, we discuss how we originally derived IRFs from Monte Carlo simulations and later corrected those IRFs for discrepancies observed between flight and simulated data. We also give details of the validations performed using flight data and quantify the residual uncertainties in the IRFs. Finally, we describe techniques the LAT team has developed to propagate those uncertainties into estimates of the systematic errors on common measurements such as fluxes and spectra of astrophysical sources.

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Additional Information:© 2012 American Astronomical Society. Received 2012 June 8; accepted 2012 August 16; published 2012 October 12. The Fermi-LAT Collaboration acknowledges generous ongoing support from a number of agencies and institutes that have supported both the development and the operation of the LAT as well as scientific data analysis. These include the National Aeronautics and Space Administration and the Department of Energy in the United States, the Commissariat à l’Energie Atomique and the Centre National de la Recherche Scientifique/Institut National de Physique Nucléaire et de Physique des Particules in France, the Agenzia Spaziale Italiana and the Istituto Nazionale di Fisica Nucleare in Italy, the Ministry of Education, Culture, Sports, Science and Technology (MEXT), High Energy Accelerator Research Organization (KEK) and Japan Aerospace Exploration Agency (JAXA) in Japan, and the K. A. Wallenberg Foundation, the Swedish Research Council and the Swedish National Space Board in Sweden. Additional support for science analysis during the operations phase is gratefully acknowledged from the Istituto Nazionale di Astrofisica in Italy and the Centre National d’Études Spatiales in France. The Parkes radio telescope is part of the Australia Telescope, which is funded by the Commonwealth Government for operation as a National Facility managed by CSIRO. We thank our colleagues for their assistance with the radio timing observations.
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Commonwealth Scientific and Research Organization (CSIRO)UNSPECIFIED
Istituto Nazionale di Astrofisica (INAF)UNSPECIFIED
Centre National d'Études Spatiales (CNES)UNSPECIFIED
Knut and Alice Wallenberg FoundationUNSPECIFIED
Subject Keywords:instrumentation: detectors; instrumentation: miscellaneous; methods: data analysis; methods: observational; telescopes
Issue or Number:1
Record Number:CaltechAUTHORS:20130109-105136191
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Official Citation:The Fermi Large Area Telescope on Orbit: Event Classification, Instrument Response Functions, and Calibration M. Ackermann et al. 2012 ApJS 203 4
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:36271
Deposited On:09 Jan 2013 19:16
Last Modified:09 Nov 2021 23:21

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