The calibration and data products of GALEX

Patrick Morrissey, Tim Conrow, Tom A. Barlow, Todd Small, Mark Seibert, Ted K. Wyder, Tamás Budavári, Stephane Arnouts, Peter G. Friedman, Karl Forster, D. Christopher Martin, Susan G. Neff, David Schiminovich, Luciana Bianchi, José Donas, Timothy M. Heckman, Young Wook Lee, Barry F. Madore, Bruno Milliard, R. Michael RichAlex S. Szalay, Barry Y. Welsh, Sukyoung K. Yi

Research output: Contribution to journalArticlepeer-review

558 Citations (Scopus)


We describe the calibration status and data products pertaining to the GR2 and GR3 data releases of the Galaxy Evolution Explorer (GALEX). These releases have identical pipeline calibrations that are significantly improved over the GRl data release. GALEX continues to survey the sky in the far-ultraviolet (FUV, ∼ 154 nm) and near-ultraviolet (NUV, ∼232 nm) bands, providing simultaneous imaging with a pair of photon-counting, microchannel plate, delay line readout detectors. These 1.25° field of view detectors are well suited to ultraviolet observations because of their excellent red rejection and negligible background. A dithered mode of observing and photon list output pose complex requirements on the data processing pipeline, entangling detector calibrations, and aspect reconstruction algorithms. Recent improvements have achieved photometric repeatability of 0.05 and 0.03 mAB in the FUV and NUV, respectively. We have detected a long-term drift of order 1% FUV and 6% NUV over the mission. Astrometric precision is of order 0.5″ rms in both bands. In this paper we provide the GALEX user with a broad overview of the calibration issues likely to be confronted in the current release. Improvements are likely as the GALEX mission continues into an extended phase with a healthy instrument, no consumables, and increased opportunities for guest investigations.

Original languageEnglish
Pages (from-to)682-697
Number of pages16
JournalAstrophysical Journal, Supplement Series
Issue number2
Publication statusPublished - 2007 Dec

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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