Archival Legacy Investigations of Circumstellar Environments ("ALICE")

The HST NICMOS instrument has been used from 1997 to 2008 to perform coronagraphic observations of about 400 targets. Most of them were part of surveys looking for substellar companions or resolved circumstellar disks to young nearby stars, making the NICMOS coronagraphic archive a valuable database for exoplanets and disks studies. The ALICE program is an HST Legacy program aiming at revaluing the NICMOS coronagraphic archive with improved detection limits, achieved with modern post-processing methods. Several advanced post-processing algorithms have been developed since 2007, making use of a library of on-sky science images to optimize starlight subtraction from a given dataset. The input data of the ALICE program are the non-polarimetric NICMOS data re-calibrated with observed dark frames and contemporary flat-field frames by the LAPLACE program, which represent 73% of the whole NICMOS non-polarimetric archive. The team delivered products for most of these LAPLACE data (15% were either bad acquisitions with the star not centered on the occulter, or data that couldn't align properly with a library, in grey in this database). To facilitate combination of these products with other surveys, the team has developed a standard FITS file format which provides all the necessary information for high-level analysis of high-contrast imaging datasets, and which aims at being compatible with any type of data (ground-based and space-based instrument, imaging, polarimetric, IFU data).