The HERSCHEL/PACS Spectrometer Pipeline

ESA's Herschel Space Observatory, to be launched in 2009, is the first space observatory covering the full far-infrared and sub-millimeter wave- length range (60 - 670µm). The Photodetector Array Camera & Spectrometer (PACS) is one of the three science instruments. It employs two Ge:Ga photocon- ductor arrays and two bolometer arrays to perform integral field spectroscopy and imaging photometry in the 60 - 210µm wavelength band. The interactive PACS Spectrometer and Photometer (Wieprecht et al. 2009) Data Reduction Pipeline is integrated in the Herschel Data Processing System. The DP is im- plemented using Java technology and written in a common effort by the HER- SCHEL Science Center (HSC) and the three instrument teams. We overview the concept and status of the PACS Spectrometer Data Reduction Pipeline. Additionally, we address the instrument mode-dependent data processing and the definition of the products of the different processing levels. Finally, we show first results by applying the pipeline on flight model instrument level test data. 1. Short Description of the Instrument The PACS integral field spectrometer contains an image slicer that dissects the field of view (47 '' × 47 '' ) in the object plane into five pieces and rearranges them on a pseudo-slit which is dispersed by a grating and projected on two 25 × 16 pixel detector arrays. The result is a raw detector frame comprising 5 × 5 (25) spatial pixels (x-direction) and 16 spectral pixels (y-direction, see Figure 1). The different arrays are selected by a dichroic beam splitter for the blue (55-98µm) and red (102-210µm) wavelength range. The pixels are photoconductors that integrate on capacitors. The voltages are read out at 256Hz and produce so-called ramps. The slope of the ramps is a measure of the incoming flux. A chopper is used to get rid of the warm telescope background. See the PACS Observer's manual 5 for more detailed information.