The fermi large area telescope on orbit: Event classification, instrument response functions, and calibration

M. Ackermann; M. Ajello; A. Albert; A. Allafort; W. B. Atwood; M. Axelsson; L. Baldini; J. Ballet; G. Barbiellini; D. Bastieri; K. Bechtol; R. Bellazzini; E. Bissaldi; R. D. Blandford; E. D. Bloom; J. R. Bogart; E. Bonamente; A. W. Borgland; E. Bottacini; A. Bouvier; T. J. Brandt; J. Bregeon; M. Brigida; P. Bruel; R. Buehler; T. H. Burnett; S. Buson; G. A. Caliandro; R. A. Cameron; P. A. Caraveo; J. M. Casandjian; E. Cavazzuti; C. Cecchi; Ö Çelik; E. Charles; R. C.G. Chaves; A. Chekhtman; C. C. Cheung; J. Chiang; S. Ciprini; R. Claus; J. Cohen-Tanugi; J. Conrad; R. Corbet; S. Cutini; F. D'Ammando; D. S. Davis; A. De Angelis; M. Deklotz; F. De Palma; C. D. Dermer; S. W. Digel; E. Do Couto E Silva; P. S. Drell; A. Drlica-Wagner; R. Dubois; C. Favuzzi; S. J. Fegan; E. C. Ferrara; W. B. Focke; P. Fortin; Y. Fukazawa; S. Funk; P. Fusco; F. Gargano; D. Gasparrini; N. Gehrels; B. Giebels; N. Giglietto; F. Giordano; M. Giroletti; T. Glanzman; G. Godfrey; I. A. Grenier; J. E. Grove; S. Guiriec; D. Hadasch; M. Hayashida; E. Hays; D. Horan; X. Hou; R. E. Hughes; M. S. Jackson; T. Jogler; G. Jóhannesson; R. P. Johnson; T. J. Johnson; W. N. Johnson; T. Kamae; H. Katagiri; J. Kataoka; M. Kerr; J. Knödlseder; M. Kuss; J. Lande; S. Larsson; L. Latronico; C. Lavalley; M. Lemoine-Goumard; F. Longo; F. Loparco; B. Lott; M. N. Lovellette; P. Lubrano; M. N. Mazziotta; W. McConville; J. E. McEnery; J. Mehault; P. F. Michelson; W. Mitthumsiri; T. Mizuno; A. A. Moiseev; C. Monte; M. E. Monzani; A. Morselli; I. V. Moskalenko; S. Murgia; M. Naumann-Godo; R. Nemmen; S. Nishino; J. P. Norris; E. Nuss; M. Ohno; T. Ohsugi; A. Okumura; N. Omodei; M. Orienti; E. Orlando; J. F. Ormes; D. Paneque; J. H. Panetta; J. S. Perkins; M. Pesce-Rollins; M. Pierbattista; F. Piron; G. Pivato; T. A. Porter; J. L. Racusin; S. Rainò; R. Rando; M. Razzano; S. Razzaque; A. Reimer; O. Reimer; T. Reposeur; L. C. Reyes; S. Ritz; L. S. Rochester; C. Romoli; M. Roth; H. F.W. Sadrozinski; D. A. Sanchez; P. M. Saz Parkinson; C. Sbarra; J. D. Scargle; C. Sgrò; J. Siegal-Gaskins; E. J. Siskind; G. Spandre; P. Spinelli; T. E. Stephens; D. J. Suson; H. Tajima; H. Takahashi; T. Tanaka; J. G. Thayer; J. B. Thayer; D. J. Thompson; L. Tibaldo; M. Tinivella; G. Tosti; E. Troja; T. L. Usher; J. Vandenbroucke; B. Van Klaveren; V. Vasileiou; G. Vianello; V. Vitale; A. P. Waite; E. Wallace; B. L. Winer; D. L. Wood; K. S. Wood; M. Wood; Z. Yang; S. Zimmer

doi:10.1088/0067-0049/203/1/4

The fermi large area telescope on orbit: Event classification, instrument response functions, and calibration

M. Ackermann^*, M. Ajello, A. Albert, A. Allafort, W. B. Atwood, M. Axelsson, L. Baldini, J. Ballet, G. Barbiellini, D. Bastieri, K. Bechtol, R. Bellazzini, E. Bissaldi, R. D. Blandford, E. D. Bloom, J. R. Bogart, E. Bonamente, A. W. Borgland, E. Bottacini, A. BouvierT. J. Brandt, J. Bregeon, M. Brigida, P. Bruel, R. Buehler, T. H. Burnett, S. Buson, G. A. Caliandro, R. A. Cameron, P. A. Caraveo, J. M. Casandjian, E. Cavazzuti, C. Cecchi, Ö Çelik, E. Charles, R. C.G. Chaves, A. Chekhtman, C. C. Cheung, J. Chiang, S. Ciprini, R. Claus, J. Cohen-Tanugi, J. Conrad, R. Corbet, S. Cutini, F. D'Ammando, D. S. Davis, A. De Angelis, M. Deklotz, F. De Palma, C. D. Dermer, S. W. Digel, E. Do Couto E Silva, P. S. Drell, A. Drlica-Wagner, R. Dubois, C. Favuzzi, S. J. Fegan, E. C. Ferrara, W. B. Focke, P. Fortin, Y. Fukazawa, S. Funk, P. Fusco, F. Gargano, D. Gasparrini, N. Gehrels, B. Giebels, N. Giglietto, F. Giordano, M. Giroletti, T. Glanzman, G. Godfrey, I. A. Grenier, J. E. Grove, S. Guiriec, D. Hadasch, M. Hayashida, E. Hays, D. Horan, X. Hou, R. E. Hughes, M. S. Jackson, T. Jogler, G. Jóhannesson, R. P. Johnson, T. J. Johnson, W. N. Johnson, T. Kamae, H. Katagiri, J. Kataoka, M. Kerr, J. Knödlseder, M. Kuss, J. Lande, S. Larsson, L. Latronico, C. Lavalley, M. Lemoine-Goumard, F. Longo, F. Loparco, B. Lott, M. N. Lovellette, P. Lubrano, M. N. Mazziotta, W. McConville, J. E. McEnery, J. Mehault, P. F. Michelson, W. Mitthumsiri, T. Mizuno, A. A. Moiseev, C. Monte, M. E. Monzani, A. Morselli, I. V. Moskalenko, S. Murgia, M. Naumann-Godo, R. Nemmen, S. Nishino, J. P. Norris, E. Nuss, M. Ohno, T. Ohsugi, A. Okumura, N. Omodei, M. Orienti, E. Orlando, J. F. Ormes, D. Paneque, J. H. Panetta, J. S. Perkins, M. Pesce-Rollins, M. Pierbattista, F. Piron, G. Pivato, T. A. Porter, J. L. Racusin, S. Rainò, R. Rando, M. Razzano, S. Razzaque, A. Reimer, O. Reimer, T. Reposeur, L. C. Reyes, S. Ritz, L. S. Rochester, C. Romoli, M. Roth, H. F.W. Sadrozinski, D. A. Sanchez, P. M. Saz Parkinson, C. Sbarra, J. D. Scargle, C. Sgrò, J. Siegal-Gaskins, E. J. Siskind, G. Spandre, P. Spinelli, T. E. Stephens, D. J. Suson, H. Tajima, H. Takahashi, T. Tanaka, J. G. Thayer, J. B. Thayer, D. J. Thompson, L. Tibaldo, M. Tinivella, G. Tosti, E. Troja, T. L. Usher, J. Vandenbroucke, B. Van Klaveren, V. Vasileiou, G. Vianello, V. Vitale, A. P. Waite, E. Wallace, B. L. Winer, D. L. Wood, K. S. Wood, M. Wood, Z. Yang, S. Zimmer

^*Corresponding author for this work

School of Advanced Science and Engineering

Research output: Contribution to journal › Article › peer-review

414 Citations (Scopus)

Abstract

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 20MeV to more than 300GeV. 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.

Original language	English
Article number	4
Journal	Astrophysical Journal, Supplement Series
Volume	203
Issue number	1
DOIs	https://doi.org/10.1088/0067-0049/203/1/4
Publication status	Published - 2012 Nov

Keywords

Instrumentation: detectors
Instrumentation: miscellaneous
Methods: data analysis
Methods: observational
Telescopes

ASJC Scopus subject areas

Astronomy and Astrophysics
Space and Planetary Science

Access to Document

10.1088/0067-0049/203/1/4

Cite this

Ackermann, M., Ajello, M., Albert, A., Allafort, A., Atwood, W. B., Axelsson, M., Baldini, L., Ballet, J., Barbiellini, G., Bastieri, D., Bechtol, K., Bellazzini, R., Bissaldi, E., Blandford, R. D., Bloom, E. D., Bogart, J. R., Bonamente, E., Borgland, A. W., Bottacini, E., ... Zimmer, S. (2012). The fermi large area telescope on orbit: Event classification, instrument response functions, and calibration. Astrophysical Journal, Supplement Series, 203(1), [4]. https://doi.org/10.1088/0067-0049/203/1/4

Ackermann, M, Ajello, M, Albert, A, Allafort, A, Atwood, WB, Axelsson, M, Baldini, L, Ballet, J, Barbiellini, G, Bastieri, D, Bechtol, K, Bellazzini, R, Bissaldi, E, Blandford, RD, Bloom, ED, Bogart, JR, Bonamente, E, Borgland, AW, Bottacini, E, Bouvier, A, Brandt, TJ, Bregeon, J, Brigida, M, Bruel, P, Buehler, R, Burnett, TH, Buson, S, Caliandro, GA, Cameron, RA, Caraveo, PA, Casandjian, JM, Cavazzuti, E, Cecchi, C, Çelik, Ö, Charles, E, Chaves, RCG, Chekhtman, A, Cheung, CC, Chiang, J, Ciprini, S, Claus, R, Cohen-Tanugi, J, Conrad, J, Corbet, R, Cutini, S, D'Ammando, F, Davis, DS, De Angelis, A, Deklotz, M, De Palma, F, Dermer, CD, Digel, SW, Do Couto E Silva, E, Drell, PS, Drlica-Wagner, A, Dubois, R, Favuzzi, C, Fegan, SJ, Ferrara, EC, Focke, WB, Fortin, P, Fukazawa, Y, Funk, S, Fusco, P, Gargano, F, Gasparrini, D, Gehrels, N, Giebels, B, Giglietto, N, Giordano, F, Giroletti, M, Glanzman, T, Godfrey, G, Grenier, IA, Grove, JE, Guiriec, S, Hadasch, D, Hayashida, M, Hays, E, Horan, D, Hou, X, Hughes, RE, Jackson, MS, Jogler, T, Jóhannesson, G, Johnson, RP, Johnson, TJ, Johnson, WN, Kamae, T, Katagiri, H, Kataoka, J, Kerr, M, Knödlseder, J, Kuss, M, Lande, J, Larsson, S, Latronico, L, Lavalley, C, Lemoine-Goumard, M, Longo, F, Loparco, F, Lott, B, Lovellette, MN, Lubrano, P, Mazziotta, MN, McConville, W, McEnery, JE, Mehault, J, Michelson, PF, Mitthumsiri, W, Mizuno, T, Moiseev, AA, Monte, C, Monzani, ME, Morselli, A, Moskalenko, IV, Murgia, S, Naumann-Godo, M, Nemmen, R, Nishino, S, Norris, JP, Nuss, E, Ohno, M, Ohsugi, T, Okumura, A, Omodei, N, Orienti, M, Orlando, E, Ormes, JF, Paneque, D, Panetta, JH, Perkins, JS, Pesce-Rollins, M, Pierbattista, M, Piron, F, Pivato, G, Porter, TA, Racusin, JL, Rainò, S, Rando, R, Razzano, M, Razzaque, S, Reimer, A, Reimer, O, Reposeur, T, Reyes, LC, Ritz, S, Rochester, LS, Romoli, C, Roth, M, Sadrozinski, HFW, Sanchez, DA, Saz Parkinson, PM, Sbarra, C, Scargle, JD, Sgrò, C, Siegal-Gaskins, J, Siskind, EJ, Spandre, G, Spinelli, P, Stephens, TE, Suson, DJ, Tajima, H, Takahashi, H, Tanaka, T, Thayer, JG, Thayer, JB, Thompson, DJ, Tibaldo, L, Tinivella, M, Tosti, G, Troja, E, Usher, TL, Vandenbroucke, J, Van Klaveren, B, Vasileiou, V, Vianello, G, Vitale, V, Waite, AP, Wallace, E, Winer, BL, Wood, DL, Wood, KS, Wood, M, Yang, Z & Zimmer, S 2012, 'The fermi large area telescope on orbit: Event classification, instrument response functions, and calibration', Astrophysical Journal, Supplement Series, vol. 203, no. 1, 4. https://doi.org/10.1088/0067-0049/203/1/4

@article{d760086c4ede4c2fb54af80b48d5a127,

title = "The fermi large area telescope on orbit: Event classification, instrument response functions, and calibration",

abstract = "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 20MeV to more than 300GeV. 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.",

keywords = "Instrumentation: detectors, Instrumentation: miscellaneous, Methods: data analysis, Methods: observational, Telescopes",

author = "M. Ackermann and M. Ajello and A. Albert and A. Allafort and Atwood, {W. B.} and M. Axelsson and L. Baldini and J. Ballet and G. Barbiellini and D. Bastieri and K. Bechtol and R. Bellazzini and E. Bissaldi and Blandford, {R. D.} and Bloom, {E. D.} and Bogart, {J. R.} and E. Bonamente and Borgland, {A. W.} and E. Bottacini and A. Bouvier and Brandt, {T. J.} and J. Bregeon and M. Brigida and P. Bruel and R. Buehler and Burnett, {T. H.} and S. Buson and Caliandro, {G. A.} and Cameron, {R. A.} and Caraveo, {P. A.} and Casandjian, {J. M.} and E. Cavazzuti and C. Cecchi and {\"O} {\c C}elik and E. Charles and Chaves, {R. C.G.} and A. Chekhtman and Cheung, {C. C.} and J. Chiang and S. Ciprini and R. Claus and J. Cohen-Tanugi and J. Conrad and R. Corbet and S. Cutini and F. D'Ammando and Davis, {D. S.} and {De Angelis}, A. and M. Deklotz and {De Palma}, F. and Dermer, {C. D.} and Digel, {S. W.} and {Do Couto E Silva}, E. and Drell, {P. S.} and A. Drlica-Wagner and R. Dubois and C. Favuzzi and Fegan, {S. J.} and Ferrara, {E. C.} and Focke, {W. B.} and P. Fortin and Y. Fukazawa and S. Funk and P. Fusco and F. Gargano and D. Gasparrini and N. Gehrels and B. Giebels and N. Giglietto and F. Giordano and M. Giroletti and T. Glanzman and G. Godfrey and Grenier, {I. A.} and Grove, {J. E.} and S. Guiriec and D. Hadasch and M. Hayashida and E. Hays and D. Horan and X. Hou and Hughes, {R. E.} and Jackson, {M. S.} and T. Jogler and G. J{\'o}hannesson and Johnson, {R. P.} and Johnson, {T. J.} and Johnson, {W. N.} and T. Kamae and H. Katagiri and J. Kataoka and M. Kerr and J. Kn{\"o}dlseder and M. Kuss and J. Lande and S. Larsson and L. Latronico and C. Lavalley and M. Lemoine-Goumard and F. Longo and F. Loparco and B. Lott and Lovellette, {M. N.} and P. Lubrano and Mazziotta, {M. N.} and W. McConville and McEnery, {J. E.} and J. Mehault and Michelson, {P. F.} and W. Mitthumsiri and T. Mizuno and Moiseev, {A. A.} and C. Monte and Monzani, {M. E.} and A. Morselli and Moskalenko, {I. V.} and S. Murgia and M. Naumann-Godo and R. Nemmen and S. Nishino and Norris, {J. P.} and E. Nuss and M. Ohno and T. Ohsugi and A. Okumura and N. Omodei and M. Orienti and E. Orlando and Ormes, {J. F.} and D. Paneque and Panetta, {J. H.} and Perkins, {J. S.} and M. Pesce-Rollins and M. Pierbattista and F. Piron and G. Pivato and Porter, {T. A.} and Racusin, {J. L.} and S. Rain{\`o} and R. Rando and M. Razzano and S. Razzaque and A. Reimer and O. Reimer and T. Reposeur and Reyes, {L. C.} and S. Ritz and Rochester, {L. S.} and C. Romoli and M. Roth and Sadrozinski, {H. F.W.} and Sanchez, {D. A.} and {Saz Parkinson}, {P. M.} and C. Sbarra and Scargle, {J. D.} and C. Sgr{\`o} and J. Siegal-Gaskins and Siskind, {E. J.} and G. Spandre and P. Spinelli and Stephens, {T. E.} and Suson, {D. J.} and H. Tajima and H. Takahashi and T. Tanaka and Thayer, {J. G.} and Thayer, {J. B.} and Thompson, {D. J.} and L. Tibaldo and M. Tinivella and G. Tosti and E. Troja and Usher, {T. L.} and J. Vandenbroucke and {Van Klaveren}, B. and V. Vasileiou and G. Vianello and V. Vitale and Waite, {A. P.} and E. Wallace and Winer, {B. L.} and Wood, {D. L.} and Wood, {K. S.} and M. Wood and Z. Yang and S. Zimmer",

year = "2012",

month = nov,

doi = "10.1088/0067-0049/203/1/4",

language = "English",

volume = "203",

journal = "Astrophysical Journal, Supplement Series",

issn = "0067-0049",

publisher = "IOP Publishing Ltd.",

number = "1",

}

TY - JOUR

T1 - The fermi large area telescope on orbit

T2 - Event classification, instrument response functions, and calibration

AU - Ackermann, M.

AU - Ajello, M.

AU - Albert, A.

AU - Allafort, A.

AU - Atwood, W. B.

AU - Axelsson, M.

AU - Baldini, L.

AU - Ballet, J.

AU - Barbiellini, G.

AU - Bastieri, D.

AU - Bechtol, K.

AU - Bellazzini, R.

AU - Bissaldi, E.

AU - Blandford, R. D.

AU - Bloom, E. D.

AU - Bogart, J. R.

AU - Bonamente, E.

AU - Borgland, A. W.

AU - Bottacini, E.

AU - Bouvier, A.

AU - Brandt, T. J.

AU - Bregeon, J.

AU - Brigida, M.

AU - Bruel, P.

AU - Buehler, R.

AU - Burnett, T. H.

AU - Buson, S.

AU - Caliandro, G. A.

AU - Cameron, R. A.

AU - Caraveo, P. A.

AU - Casandjian, J. M.

AU - Cavazzuti, E.

AU - Cecchi, C.

AU - Çelik, Ö

AU - Charles, E.

AU - Chaves, R. C.G.

AU - Chekhtman, A.

AU - Cheung, C. C.

AU - Chiang, J.

AU - Ciprini, S.

AU - Claus, R.

AU - Cohen-Tanugi, J.

AU - Conrad, J.

AU - Corbet, R.

AU - Cutini, S.

AU - D'Ammando, F.

AU - Davis, D. S.

AU - De Angelis, A.

AU - Deklotz, M.

AU - De Palma, F.

AU - Dermer, C. D.

AU - Digel, S. W.

AU - Do Couto E Silva, E.

AU - Drell, P. S.

AU - Drlica-Wagner, A.

AU - Dubois, R.

AU - Favuzzi, C.

AU - Fegan, S. J.

AU - Ferrara, E. C.

AU - Focke, W. B.

AU - Fortin, P.

AU - Fukazawa, Y.

AU - Funk, S.

AU - Fusco, P.

AU - Gargano, F.

AU - Gasparrini, D.

AU - Gehrels, N.

AU - Giebels, B.

AU - Giglietto, N.

AU - Giordano, F.

AU - Giroletti, M.

AU - Glanzman, T.

AU - Godfrey, G.

AU - Grenier, I. A.

AU - Grove, J. E.

AU - Guiriec, S.

AU - Hadasch, D.

AU - Hayashida, M.

AU - Hays, E.

AU - Horan, D.

AU - Hou, X.

AU - Hughes, R. E.

AU - Jackson, M. S.

AU - Jogler, T.

AU - Jóhannesson, G.

AU - Johnson, R. P.

AU - Johnson, T. J.

AU - Johnson, W. N.

AU - Kamae, T.

AU - Katagiri, H.

AU - Kataoka, J.

AU - Kerr, M.

AU - Knödlseder, J.

AU - Kuss, M.

AU - Lande, J.

AU - Larsson, S.

AU - Latronico, L.

AU - Lavalley, C.

AU - Lemoine-Goumard, M.

AU - Longo, F.

AU - Loparco, F.

AU - Lott, B.

AU - Lovellette, M. N.

AU - Lubrano, P.

AU - Mazziotta, M. N.

AU - McConville, W.

AU - McEnery, J. E.

AU - Mehault, J.

AU - Michelson, P. F.

AU - Mitthumsiri, W.

AU - Mizuno, T.

AU - Moiseev, A. A.

AU - Monte, C.

AU - Monzani, M. E.

AU - Morselli, A.

AU - Moskalenko, I. V.

AU - Murgia, S.

AU - Naumann-Godo, M.

AU - Nemmen, R.

AU - Nishino, S.

AU - Norris, J. P.

AU - Nuss, E.

AU - Ohno, M.

AU - Ohsugi, T.

AU - Okumura, A.

AU - Omodei, N.

AU - Orienti, M.

AU - Orlando, E.

AU - Ormes, J. F.

AU - Paneque, D.

AU - Panetta, J. H.

AU - Perkins, J. S.

AU - Pesce-Rollins, M.

AU - Pierbattista, M.

AU - Piron, F.

AU - Pivato, G.

AU - Porter, T. A.

AU - Racusin, J. L.

AU - Rainò, S.

AU - Rando, R.

AU - Razzano, M.

AU - Razzaque, S.

AU - Reimer, A.

AU - Reimer, O.

AU - Reposeur, T.

AU - Reyes, L. C.

AU - Ritz, S.

AU - Rochester, L. S.

AU - Romoli, C.

AU - Roth, M.

AU - Sadrozinski, H. F.W.

AU - Sanchez, D. A.

AU - Saz Parkinson, P. M.

AU - Sbarra, C.

AU - Scargle, J. D.

AU - Sgrò, C.

AU - Siegal-Gaskins, J.

AU - Siskind, E. J.

AU - Spandre, G.

AU - Spinelli, P.

AU - Stephens, T. E.

AU - Suson, D. J.

AU - Tajima, H.

AU - Takahashi, H.

AU - Tanaka, T.

AU - Thayer, J. G.

AU - Thayer, J. B.

AU - Thompson, D. J.

AU - Tibaldo, L.

AU - Tinivella, M.

AU - Tosti, G.

AU - Troja, E.

AU - Usher, T. L.

AU - Vandenbroucke, J.

AU - Van Klaveren, B.

AU - Vasileiou, V.

AU - Vianello, G.

AU - Vitale, V.

AU - Waite, A. P.

AU - Wallace, E.

AU - Winer, B. L.

AU - Wood, D. L.

AU - Wood, K. S.

AU - Wood, M.

AU - Yang, Z.

AU - Zimmer, S.

PY - 2012/11

Y1 - 2012/11

N2 - 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 20MeV to more than 300GeV. 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.

AB - 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 20MeV to more than 300GeV. 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.

KW - Instrumentation: detectors

KW - Instrumentation: miscellaneous

KW - Methods: data analysis

KW - Methods: observational

KW - Telescopes

UR - http://www.scopus.com/inward/record.url?scp=84867658690&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84867658690&partnerID=8YFLogxK

U2 - 10.1088/0067-0049/203/1/4

DO - 10.1088/0067-0049/203/1/4

M3 - Article

AN - SCOPUS:84867658690

VL - 203

JO - Astrophysical Journal, Supplement Series

JF - Astrophysical Journal, Supplement Series

SN - 0067-0049

IS - 1

M1 - 4

ER -

The fermi large area telescope on orbit: Event classification, instrument response functions, and calibration

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