MIPSGAL: A Survey of the Inner Galactic Plane at 24 and 70 μm S. J. CAREY , 1 A. NORIEGA-CRESPO, 1 D. R. MIZUNO, 2 S. SHENOY , 1 R. P ALADINI, 1 K. E. KRAEMER, 3 S. D. PRICE, 3 N. FLAGEY , 1 E. RYAN, 1,4 J. G. INGALLS, 1 T. A. KUCHAR, 2 DANIELA PINHEIRO GONÇALVES, 5 R. INDEBETOUW, 6 N. BILLOT , 7 F. R. MARLEAU, 1,7 D. L. P ADGETT , 1 L. M. REBULL, 1 E. BRESSERT , 8 BABAR ALI, 7 S. MOLINARI, 9 P. G. MARTIN, 5 G. B. BERRIMAN, 7 F. BOULANGER, 10 W. B. LATTER, 7 M. A. MIVILLE-DESCHENES, 10 R. SHIPMAN, 11 AND L. TESTI 12 Received 2008 September 29; accepted 2008 November 26; published 2009 January 4 ABSTRACT. MIPSGAL is a 278 deg 2 survey of the inner Galactic plane using the Multiband Infrared Pho- tometer for Spitzer aboard the Spitzer Space Telescope. The survey field was imaged in two passbands, 24 and 70 μm with resolutions of 6″ and 18″, respectively. The survey was designed to provide a uniform, well-calibrated and well-characterized data set for general inquiry of the inner Galactic plane and as a longer-wavelength comple- ment to the shorter-wavelength Spitzer survey of the Galactic plane: Galactic Plane Infrared Mapping Survey Ex- traordinaire. The primary science drivers of the current survey are to identify all high-mass (M> 5 M ⊙ ) protostars in the inner Galactic disk and to probe the distribution, energetics, and properties of interstellar dust in the Galactic disk. The observations were planned to minimize data artifacts due to image latents at 24 μm and to provide full coverage at 70 μm. Observations at ecliptic latitudes within 15° of the ecliptic plane were taken at multiple epochs to help reject asteroids. The data for the survey were collected in three epochs, 2005 September–October, 2006 April, and 2006 October with all of the data available to the public. The estimated point-source sensitivities of the survey are 2 and 75 mJy (3 σ) at 24 and 70 μm, respectively. Additional data processing was needed to mitigate image artifacts due to bright sources at 24 μm and detector responsivity variations at 70 μm due to the large dynamic range of the Galactic plane. Enhanced data products including artifact-mitigated mosaics and point-source catalogs are being produced with the 24 μm mosaics already publicly available from the NASA/IPAC Infrared Science Archive. Some preliminary results using the enhanced data products are described. Online material: color figure 1. INTRODUCTION Unbiased, large-scale infrared surveys of the sky have pro- vided a wealth of information on astronomical phenomena arising from emission by interstellar dust and/or from objects that are either intrinsically cold or have such high extinction as to be invisible at shorter wavelengths. The early all-sky sur- veys characterized new or little-known components of the sky: the Two Micron Sky Survey (TMSS; Neugebauer & Leighton 1969) found a near-infrared sky populated by stars enshrouded in circumstellar dust; the Air Force Cambridge Research Laboratory/Geophysics Laboratory (AFCRL/AFGL) mid- infrared survey (Walker & Price 1975; Price & Walker 1976) found a colder population and several examples of post- asymptotic giant branch (post-AGB) stars and preplanetary nebulae sources, the Infrared Astronomical Satellite (IRAS; Neugebauer 1985) observed emission from interstellar dust, in- frared cirrus, and ultraluminous infrared galaxies, while the Two Micron All Sky Survey (2MASS; Skrutskie et al. 2006) results included defining the population of brown dwarfs. The Galactic plane has historically been well studied because it is rich in bright sources making it a prime target if observa- tional resources are limited. Thus, Hoffmann et al. (1971) sur- veyed a large portion of the plane at 100 μm from a balloon platform while the rocket-borne measurements of Houck et al. (1971) sampled the inner plane at wavelengths between 5 and 1 Spitzer Science Center, MS 220-6, California Institute of Technology, Pasadena, CA; carey@ipac.caltech.edu 2 Institute for Scientific Research, Boston College, Chestnut Hill, MA 3 Air Force Research Laboratory, AFRL/RVBYB, Hanscom AFB, MA 4 Department of Astronomy, University of Minnesota, Minneapolis, MN 5 CITA, University of Toronto, 60 St. George St., Toronto, ON, M5S 3H8, Canada 6 Department of Astronomy, P.O. Box 400325,University of Virginia, Char- lottesville, VA 7 Infrared Processing and Analysis Center, MS 100-22, California Institute of Technology, Pasadena, CA 8 Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 9 Isituto di Fisica dello Spazio Interplanetario, Via del Fosso del Cavaliere, 00133 Roma, Italy 10 Institut d’Astrophysique Spatiale, Batiment 121, Universite Paris-Sud, Orsay, 91405, France 11 SRON, Postbus 800, 9700 AV Groningen, The Netherlands 12 Arcetri Observatory, 5 L.go E. Fermi, 50125 Firenze Italy 76 PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE P ACIFIC, 121:76–97, 2009 January © 2009. The Astronomical Society of the Pacific. All rights reserved. Printed in U.S.A.