摘要：The knowledge of the point spread function (PSF) of imaging instruments represents a fundamental requirement for astronomical observations. The Herschel PACS PSFs delivered by the instrument control centre are obtained from observations of the Vesta asteroid, which provides a characterisation of the central part and, therefore, excludes fainter features. In many cases, however, information on both the core and wings of the PSFs is needed. With this aim, we combine Vesta and Mars dedicated observations and obtain PACS PSFs with an unprecedented dynamic range (~106) at slow and fast scan speeds for the three photometric bands.
