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META TOPICPARENT name="WebHome"

PACS instrument and calibration web pages

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Introduction

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  You can also consult the PACS NHSC homepage.
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Important message about drizzled cubes

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Temporary notes

Spectroscopy

 
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Due to an oversight in the pipeline scripts of HIPE 13, the drizzled cubes for chop-nod line scan observations created by "SPG 13" have incorrect fluxes. Therefore you should not use the drizzled cubes downloaded from the HSA if the Meta datum "creator" is "SPG 13.0", whether they are within the ObservationContext at Level 2, or part of a Standalone Browse Product download.

Drizzled cubes created for unchopped mode observations are unaffected, and for chop-nod range scan observations, drizzled cubes are not created by the SPG 13 pipeline.

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Due to an oversight in the pipeline scripts of HIPE 13, the drizzled cubes for chop-nod line scan observations created by "SPG 13" have incorrect fluxes. Therefore you should not use the drizzled cubes downloaded from the HSA if the Meta datum "creator" is "SPG 13.0", whether they are within the ObservationContext at Level 2, or part of a Standalone Browse Product download. Drizzled cubes created for unchopped mode observations are unaffected, and for chop-nod range scan observations, drizzled cubes are not created by the SPG 13 pipeline.
  This oversight has been corrected in HIPE/SPG 14. The drizzled cubes you get in an observation downloaded from the HSA with "creator" of "SPG 14.0" have correct fluxes. In HIPE 14 there is a dedicated script to produce these drizzled cubes. Therefore we recommend you use the SPG 14.0 products, or use the dedicated pipeline in HIPE 14 if you need your drizzled cubes before the SPG 14 products are available.
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Photometry

 
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FYI: Drizzled cubes can be found in an observation in the context called HPS3DD [R|B] (red and blue). They are also provided as standalone browse products in a context called HPS3DEQ [R|B] (red and blue, equidistant wavelength grid version of the drizzled cubes). On disk the FITS files for these cubes have the same set of letters in their name (but in lower case) and are at the Level 2 part of an observation.

For more information about the standard and the standalone browse cubes provided for PACS spectroscopy, see the PACS Products Explained HIPE help document, which is also available from the PACS documentation webpage and the HIPE download webpage, both off the Herschel Science Centre webpage.

Important message about Unimap maps

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Some Unimap maps produced by SPG 13 and using HIPE 13 scripts show overshooting effects around very bright sources that are surrounded by a diffuse and relatively faint background. See, as an example, the blue image of NGC253 (obsID: 1342221743). This effect is due to a non-optimised convergence of the GLS algorithm and it will be corrected in HIPE/SPG14.
 
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Some Unimap maps produced by SPG 13 and using HIPE 13 scripts show overshooting effects around very bright sources that are surrounded by a diffuse and relatively faint background. See, as an example, the blue image of NGC253 (obsID: 1342221743). This effect is due to a non-optimised convergence of the GLS algorithm and it will be corrected in HIPE/SPG14.

This has been corrected in HIPE 14, and products with "creator" of "SPG 14" have no overshooting effects.

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This has been corrected in HIPE 14, and products with "creator" of "SPG 14" have no overshooting effects.
 

Observing with PACS

  • The PACS Observer's Manual HTML PDF (11 Mb), version 2.3, 8-June-2011 : the first thing to read before applying for time with PACS (or even before working on PACS data for the first time), as it tells you how the instrument works. This includes:
    • A description of the layout and the components of the PACS photometer and spectrometer
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Photometer calibration in scan maps

  • Point Spread Function/Encircled Energy Fraction : PACS Photometer Point Spread function (10 Mb), version 2.2, 16 November 2015. A detailed document of the in-flight observed PSF and of the derivation of the EEF curves. The accompanying TAR file can be downloaded here (79 MB). It contains the Vesta PSFs FITS files and the EEF tables for all the scanning modes.
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  • Herschel/PACS modelled point spread functions (3.1 Mb) is a related document presenting Zemax modelled point spread functions for both an `ideal' and an 'as built' Herschel telescope model. Tarballs with corresponding broad-band and monochromatic PSFs for these two cases are at http://pacs.ster.kuleuven.ac.be/pubtool/PSF. These are useful in addition to the observed PSFs but cannot replace them, since the models do not capture all effects found in the observed PSFs.
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  • Herschel/PACS modelled point spread functions (3.1 Mb) is a related document presenting Zemax modelled point spread functions for both an `ideal' and an 'as built' Herschel telescope model. Tarballs with corresponding broad-band and monochromatic PSFs for these two cases are at http://pacs.ster.kuleuven.ac.be/pubtool/PSF. These are useful in addition to the observed PSFs but cannot replace them, since the models do not capture all effects found in the observed PSFs.
 
  • Point-source photometry: PACS uses 5 stars as primary calibrators with fluxes ranging from 0.6 to 15 Jy, plus fainter stars and asteroids as secondary calibrators. The absolute flux scale accuracy is dominated by the model uncertainties and amounts to 5% in the 3 filter bands. At the same time, the reproducibility for a given non-variable point source is better than 2% for all PACS bands. The flux calibration is described in detail in Balog et al, 2013, Experimental Astronomy and confirmed with asteroids in Müller et al., 2013, Experimental Astronomy.
  • Point-source photometry in deep PACS maps/surveys: The e ffect of the high-pass fi lter data reduction technique on the PACS Photometer PSF, point-source photometry, and noise has been investigated in depth in this technical note.
  • Colour corrections:
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Photometer map-makers

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  • Four fundamentally different map-makers are offered in HIPE 13 with interactive pipeline scripts, starting from Level 1. These map-makers are used in different ways to generate standard products ("SPG" product) provided by the Herschel Science Archive. High-pass filtering is applied to generate Level2 products, while Level2.5 products are generated by combining pairs of observations acquired in the scan plus cross-scan mode, using the Unimap, JScanam, and High-pass filtering mappers. Level3 products are mosaics of Unimap and Jscanam Level2.5 products that belong to the same sky field and to the same observing program.

    JScanam, Unimap and MadMap mappers all clean the dataset of systematic effects and remove the correlated 1/f noise while preserving the sky signal over large spatial scales. They are suited for analysing both point sources and extended emission.

    • Highpass filtering branch, where the bolometer timelines are high-pass filtered to remove the 1/f noise, but at the expense of extended emission. It provides optimum sensitivity for point-sources
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  • Four fundamentally different map-makers are offered in HIPE 14 with interactive pipeline scripts, starting from Level 1. These map-makers are used in different ways to generate standard products ("SPG" product) provided by the Herschel Science Archive. High-pass filtering is applied to generate Level2 products, while Level2.5 products are generated by combining pairs of observations acquired in the scan plus cross-scan mode, using the Unimap, JScanam, and High-pass filtering mappers. Level3 products are mosaics of Unimap and Jscanam Level2.5 products that belong to the same sky field and to the same observing program.
    • Highpass filtering branch, where the bolometer timelines are high-pass filtered to remove the 1/f noise, but at the expense of extended emission. It provides optimum sensitivity to point-sources
  • JScanam, Unimap and MadMap mappers all clean the dataset of systematic effects and remove the correlated 1/f noise while preserving the sky signal over large spatial scales. They are suited for analysing both point sources and extended emission.
 
    • JScanam, a Java-version of the IDL Scanamorphos map-maker, an IDL map-maker from Hélène Roussel (IAP), with an advanced and powerful destriper for PACS maps
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    • Unimap, a light (memory-wise) GLS (generalised least square) map-maker from Lorenzo Piazzo ('La Sapienza' University of Rome) running under a free Matlab runtime environment, with advanced pre-processing (drift correction, jump detection) and post-processing stages (bright sources). The runUnimap task is used to invoke the Unimap Matlab routine on the users's computer
    • MADmap, a GLS (generalised least square) map-maker, a GLS map-maker that is not used anymore in the SPG processing, but it is still available as an interactive script
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    • Unimap, a GLS (generalised least square) map-maker from Lorenzo Piazzo ('La Sapienza' University of Rome) running under a free Matlab runtime environment, with advanced pre-processing (drift correction, jump detection) and post-processing stages (bright sources). The runUnimap task is used to invoke the Unimap Matlab routine on the users's computer
    • MADmap, a GLS (generalised least square) map-maker, a GLS map-maker that is not used anymore in the SPG processing, but it is still available as an interactive script
 
  • A report of the map-making working group compiled by Roberta Paladini is available: PACS map-making tools: analysis and benchmarking, 1 Nov. 2013.
  • An updated version of that report, concentrating on JScanam, MADmap and Unimap in their latest versions is available: PACS map-making tools: analysis and benchmarking, 30 March 2014.
  • If you are using data with SPG v 12 or lower, or reducing data with HIPE 12 or lower, remember that the optical field distortion in not applied at level 1. As a result, external map-makers starting from level 1 have a systematic flux overestimate of 6-7% in the red channel and a lower underestimate (~2%) in the blue channel of the flux scale. From HIPE 13/SPG 13 onwards, this has been corrected.
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PACS spectrometer calibration

 
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PACS spectrometer calibration

  • PACS Spectrometer performance and calibration: The PACS Spectrometer Calibration Document v2.4 (16-June-2011) provides details on the calibration accuracy and the necessary information to optimally interpret PACS spectroscopy observations. (Please note, this document refers to the calibration status and performance of pipeline version v8.0. An update compatible with HIPE v13 release will be provided soon.) This includes:
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  • PACS Spectrometer performance and calibration: The PACS Spectrometer Calibration Document v2.4 (16-June-2011) provides details on the calibration accuracy and the necessary information to optimally interpret PACS spectroscopy observations. (Please note, this document refers to the calibration status and performance of pipeline version v8.0. An update compatible with HIPE v14 release will be provided soon.) This includes:
 
    • flux calibration accuracies for chop nod and unchopped observations
    • the beam efficiencies and the PACS integral field footprint
    • spectral leakages and ghosts
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  • PACS data are reduced with pipeline scripts which are a set of command-line tasks that process the data from Level 0 (raw) to Level 2/2.5 (science-ready). There is more than one flavour of pipeline script, tailored to different types of science target, AOT, and observing plan. These 'interactive' pipeline scripts are provided in HIPE and explained in the data reduction guides.
  • The data you get from the the HSA will have been processed by the 'SPG' (Standard Product Generator) using one pipeline script flavour per AOT. Which script is used is documented in the PDRG.
  • The SPG scripts include all the stable pipeline tasks within those scripts, with task settings that correspond to the most common type of science target for each AOT. But some pipeline tasks still can only be run via the interactive pipeline scripts, and to modify the parameter settings for the important pipeline tasks also requires you re-process the data. The Launch Pads (see below) include a guide to understanding the pipeline scripts and how to decide whether to reprocess your data and if so, with which script.
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  • For a explanation of PACS products, i.e. what you get when you download a complete or part of an observation from the HSA, see the PACS Products Explained, which can also be found on the HIPE help pages.
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  • For a explanation of PACS products, i.e. what you get when you download a complete or part of an observation from the HSA, see the PACS Products Explained, which can also be found on the HIPE help pages.
 

HIPE, data reduction documentation, and useful links for data issues

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  • HIPE (Herschel Interactive Processing Environment) is the tool used to inspect, reduce, and analyse Herschel data. The latest User Release HCSS (Herschel common science system) version that you should use for reducing PACS data is HIPE v13.0 It can be downloaded from: http://herschel.esac.esa.int/HIPE_download.shtml. In the CIB (continuous integration build) this version corresponds to Track 13, build 5130. The CIB is the continuously bug-fixed/upgraded/improved version of HIPE, which every few months (in the beginning of the mission) or yearly (in the post-operations phase) becomes a stable User Release.
  • Within HIPE you can access all the PACS data reduction documentation and the general HCSS and HIPE user documentation for Track 13 here. The documentation provided via HIPE opens in a web browser, but for those of you who prefer PDF, we include the PACS Data Reduction Guides as PDF files here (note that within the standalone pdf versions, external links will not work):
  • The what's new in HIPE 13 page lists the changes in HIPE version 13.x with respect to the 12.x series, and provides a detailed list of updated functionalities, product changes, and calibration aspects.
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  • HIPE (Herschel Interactive Processing Environment) is the tool used to inspect, reduce, and analyse Herschel data. The latest User Release HCSS (Herschel common science system) version that you should use for reducing PACS data is HIPE v14.0 It can be downloaded from: http://herschel.esac.esa.int/HIPE_download.shtml. In the CIB (continuous integration build) this version corresponds to Track 14, build 3341. The CIB is the continuously bug-fixed/upgraded/improved version of HIPE, which every few months (in the beginning of the mission) or yearly (in the post-operations phase) becomes a stable User Release.
  • Within HIPE you can access all the PACS data reduction documentation and the general HCSS and HIPE user documentation for Track 14 here. The documentation provided via HIPE opens in a web browser, but for those of you who prefer PDF, we include the PACS Data Reduction Guides as PDF files here (note that within the standalone pdf versions, external links will not work):
  • The what's new in HIPE 14 page lists the changes in HIPE version 14.x with respect to the 13.x series, and provides a detailed list of updated functionalities, product changes, and calibration aspects.
 
  • The Data products known issues page details issues about the pipelines or the data products that are known about and offers advice for dealing with them. Consult this if you encounter problems with your data to see if it has already been addressed.
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  • Link to the General HCSS Public Twiki page (with general framework information and updates): http://herschel.esac.esa.int/twiki/bin/view/Public/WebHome
 

Cookbooks and interactive pipeline scripts

  • The various interactive pipeline scripts PACS photometry and spectroscopy provide in HIPE can be seen as cookbooks, since they take you through each pipeline, task by task, explaining briefly what each task does, commenting on the more crucial pipeline tasks, and showing you how to plot, image, visualise and inspect your data as you work through the pipeline. An example public observation is included with each so you can test it out before using it on your data. These data reduction scripts are available in HIPE under the menu: Pipeline --> PACS --> Photometer/Spectrometer.
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  • The PACS Launch Pad from HIPE 13 for photometry is provided here. The PACS Launch Pad from HIPE 13 for spectroscopy is provided here. These are taken from the first chapters of the respective PDRGs and are a useful quick-start guide to loading your data into HIPE, looking at them, and then what to know and do before you begin reprocessing your data with one of the pipelines. Also included is
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  • The PACS Launch Pad from HIPE 14 for photometry is provided here. The PACS Launch Pad from HIPE 14 for spectroscopy is provided here. These are taken from the first chapters of the respective PDRGs and are a useful quick-start guide to loading your data into HIPE, looking at them, and then what to know and do before you begin reprocessing your data with one of the pipelines. Also included is
 
    • why we recommend you do re-pipeline your data
    • what you need to pay attention to for different types of astronomical source
    • what the crucial pipeline tasks are
    • what the post-pipeline processing tasks that we provide are

Tutorials and scripts

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  • The Scripts menu in HIPE takes you to a set of PACS photometry and spectroscopy useful scripts. In HIPE 13 these are:
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  • The Scripts menu in HIPE takes you to a set of PACS photometry and spectroscopy useful scripts. In HIPE 14 these are:
 
    • Point source aperture photometry
    • Multiple point source aperture photometry
    • Image convolution (photometry)
 
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