We propose to observe the compact but well-studied protostellar core L1251B with all Herschel instruments. L1251B harbors potentially the first XDR ever isolated (there are two strong candidates) and is the only low mass source that we have an existence of the detailed maps of ice evaporation. Therefore, we propose to observe L1251B in [N II] 205.4 micron and the ground state p-H2O lines with HIFI to study the effects by high energy photons produced through the accretion process in early evolutionary stages. This will be supplemented with PACS full SED and SPIRE FTS modes. This combined data set will confirm the potential presence of the first low mass XDR. They also will allow for the only source where Herschel can connect water vapor and water ice emission to Spitzer maps of water ice absorption on equivalent spatial scales.
Herschel was launched on 14 May 2009! It is the fourth 'cornerstone' mission in the ESA science programme. With a 3.5 m Cassegrain telescope it is the largest space telescope ever launched. It is performing photometry and spectroscopy in approximately the 55-671 µm range, bridging the gap between earlier infrared space missions and groundbased facilities.