Hubble Space Telescope Advanced Camera for Surveys mosaic of the prototypical starburst galaxy M82

In 2006 March, the Hubble Heritage Team obtained a large, four-filter ( B, V, I, and Ha), 6 point mosaic data set of the prototypical starburst galaxy NGC 3034 ( M82) with the Advanced Camera for Surveys on board the Hubble Space Telescope (HST). The resulting color composite Heritage image was released in 2006 April to celebrate HST's 16th anniversary. Cycle 15 HST proposers were encouraged to submit General Observer and Archival Research proposals to complement and/or analyze this unique data set. Since our M82 mosaics represent a significant investment of expert processing beyond the standard archival products, we also released our drizzle-combined FITS data as a High- Level Science Product via the Multimission Archive at STScI in 2006 December. This paper documents the key aspects of the observing program and image processing: calibration, image registration and combination ( drizzling), and the rejection of cosmic rays and detector artifacts.