GASPS - a Herschel survey of gas and dust in Protoplanetary Disks: Survey Description and Early Results. submitted

We describe a large-scale far-infrared line and continuum survey of protoplanetary disk through to young debris disk systems carried out using the PACS instrument on the Herschel Space Observatory. This Open Time Key Program, known as GASPS (Gas Survey of Protoplan-etary Systems), targeted ∼250 young stars in narrow wavelength regions covering the [OI] fine structure line at 63µm, the brightest far-infrared line in such objects. A subset of the bright-est targets were also surveyed in [OI] 145µm, [CII] at 157µm, as well as several transitions of H2O and high-excitation CO lines at selected wavelengths between 78 and 180µm. Additionally, GASPS included continuum photometry at 70, 100 and 160µm, around the peak of the dust emission. The targets were SED Class II-III T Tauri stars and debris disks from 7 nearby young associations, along with a comparable sample of isolated Herbig AeBe stars. The aim was to study the global gas and dust content in a wide sample of circumstellar disks, combining the results with models in a systematic way. In this overview paper we review the scientific aims, target selection and observing strategy. We summarise some of the initial results, showing line identifications, listing the detections, and giving a first statistical study of line detectability