Completing the OH ladder for HH 46

First results from PACS observations towards the lowmass protostar HH 46 showsurprisingly bright OH lines. The hydroxyl radical OH plays important roles inthe water and oxygen chemistry of starforming regions and their cooling.Furthermore, the hydroxyltowater line ratios are interesting tracers forionizing radiation.We propose a nearly complete observation of the OH ladder in lowmass star formationfor the first time. Four OH transitions in the class I object HH 46 were detected byPACS. We propose complementary observations towards the source in PACS line spectroscopy mode at 53, 56, 65,71, 96, 115 and 135 micron. We gain insight in the origin and formation of OH fromthe PACS spatial information. The completeness of the OH ladder allows a reliabledetermination of the OH abundance and thus constrains water chemistry and coolingcontribution more precisely.In addition, we propose HIFI observations of the OH transition at 163.4 micron to resolve the three hyperfine components for the first time.This will allow to determine optical depths of OH and test the hypothesis ofasymmetries between the two closely spaced triplets, as the second triplet will beobserved within the HIFI priority science program.Note: This proposal is submitted under the Swiss part of the HIFI guaranteedtime program; HIFI PI: Frank Helmich, HIFI Swiss Lead CoI: Arnold O. Benz truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]