Mid-IR spectro-imaging observations with the ISOCAM CVF:: Final reduction and archive

Mid-IR (5-17 mu m) Spectro-Imaging observations towards several hundred sky positions were obtained with the Infrared Space Observatory Camera (ISOCAM), and a Circular Variable Filter (CVF) that provided spectral resolution R = lambda/Delta lambda similar to 45 over a 3' x 3' field (for 6, and 12" pixels, proportionally smaller for the observations carried with the 3, and 1.5" pixels). The wavelength range includes dust bands - in particular several of the aromatic carbon bands - fine structure lines from ionized gas, and H-2 rotational lines. The observed fields comprise nearby and distant galaxies, Galactic and Extragalactic star forming regions, the Galactic diffuse emission, nearby molecular clouds, infrared cirrus, young stellar objects, evolved stars, and Solar System targets. We present the final data reduction procedure that improves on the standard pipeline reduction in several ways, mainly the subtraction of zodiacal light, that of stray light associated with the uniform, most often dominant, emission component and the correction of a pixel dependent wavelength shift. We also propose a correction of the largest astrometry errors introduced by the optics. We have processed most of the ISOCAM CVF observations and made the results available on the ISO archive for public use. The processed data may be routinely used over the full sensitivity range of the instrument down to a brightness as faint as a few % of the zodiacal emission. For extended emission, the CVF observations represent a data base with a lasting value which can serve many scientific goals and motivate follow-up observations in particular with the Spitzer Space Telescope spectrometer.