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PACS instrument and calibration web pages

Introduction

This page provides up-to-date information about using the PACS instrument: from preparing observations to reducing your data. We include information summaries, technical reports, information about and links to HIPE--the data processing environment for Herschel data--and the PACS data reduction guides, and cookbooks and scripts that you can use in HIPE when working with PACS data. This page also provides you with the latest calibration accuracies and known PACS calibration issues, and information about what future calibration and processing improvements can be expected.

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 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
    • A description of the scientific capabilities of the instrument: spectral response functions, sensitivity values, point spread functions, astrometric accuracy; these can also be found in the AOT release notes
    • A description of the standard observing templates that were used to set up PACS observations; here you can also learn the lingo that is used in the PACS data reduction guides (DRGs)
    • A brief description of PACS data products; though much more detail on this is provided in the PACS DRGs

  • AOT Release Notes: dedicated release notes per AOT (the astronomer's observing template, i.e. planning your observing time).
    • Information about how the various standard observing blocks work
    • Summaries of transmission functions, sensitivity, etc. for use in your observing planning
    • We are now at the end of the mission. But these release notes can still be useful to read for a background understanding on how PACS data were gathered--this dictates what you will see as you look at your PACS data while pipeline processing them
    • You can also learn here the lingo that is used in the PACS DRGs when describing the data reduction pipeline scripts

Reducing PACS data

Brief explanation

A brief introduction to reducing PACS data in HIPE. You can consult the PACS Data Reduction Guides (photometry and spectroscopy) for more detail.
  • The data you get from the the HSA will have been processed by the "SPG" (Standard Product Generator), which is another way of saying that it is processed with a tailored version of the latest pipeline scripts from the User Release. So, when HIPE User Release 11.0 is released, soon after all the Herschel data are processed with the SPG pipeline scripts of version 11.0, and so on for each User Release.
  • For PACS these SPG scripts are a copy of one flavour of interactive pipeline scripts. The SPG scripts include all the stable pipeline tasks with settings that correspond to the most common type of science target and observing plan (AOT). But some pipeline tasks can only be run via the interactive scripts. The Launch Pads (see below) of the data reduction guides brings you up-to-date on this matter.
  • This makes the SPG results a good starting point to look at your PACS data, but in most cases you can improve the results at least somewhat by reducing the data yourself.
  • For photometry and spectroscopy both there is more than one flavour of pipeline script, tailored to different types of science target or observing plan. These "interactive" pipeline scripts are provided in HIPE and explained in the data reduction guides.

HIPE and data reduction documentation

  • 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 v11.1 It can be downloaded from: http://herschel.esac.esa.int/HIPE_download.shtml. In the CIB (continuous integration build) this version corresponds to Track 11, build 3010. (The CIB is the continuously bug-fixed/upgraded/improved version of HIPE, which every X months becomes a stable User Release. The CIB has the latest software in it, but it will not be bug-free.)

  • The documentation-set provided via HIPE includes the following:
    • The PACS(and HIFI and SPIRE) DRGs. The main function of the "PDRGs" is to take you through reducing your data with the interactive pipelines. They also show you how to quick-look at the already-reduced data you get from the HSA, what to consider before and after reducing your data, and explain what is contained in the PACS data products you get from the HSA.
    • A guide to using HIPE itself (i.e. HIPE as a GUI rather than a scientific tool).
    • A Data Reduction Guide, which is about working with all Herschel (or any other) data in HIPE: the various data analysis tools and data viewers are explained here
    • A Scripting Guide: the language of HIPE is "HIPE's version of jython", and it is intended to be a full scripting environment in which you can manipulate data, do mathematics, and view data in various ways. The "SG" is a guide to scripting in HIPE, although you should be comfortable with scripting yourself (preferably with python, jython, or JAVA) before embarking on scripting in HIPE.
    • Reference manuals, for most of the tasks that you can find in HIPE, and to all the product classes that you can find in HIPE (these tell you e.g. how to manipulate spectra and images directly by querying on the product, rather than using a pre-provided task).

  • The what's new in HIPE 11 page lists the changes in HIPE version 11.1 with respect to the 10.x series, provides a detailed lists of updated functionalities and calibration aspects.

Cookbooks and interactive pipeline scripts

  • The pipeline scripts can be seen as cookbooks since they take you through each pipeline flavour, 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.
  • The PDRGs explain in more detail what each pipeline task does and how to work your way through the more critical stages of the pipeline. The PDRGs also explain how to decide which pipeline flavour(s) to run on your data.
  • The PACS Launch Pad from June 2013 for photometry are provided here for photometry. This is taken from the first chapter of the PDRGs and is a useful quick-start guide to loading your data into HIPE, and then what to know and do before you begin reprocessing your data with one of the pipelines.
  • The PACS Launch Pad from July 2013 for spectroscopy (for Track 11) are provided here for spectroscopy. This is taken from the first chapter of the PDRGs and is a useful quick-start guide to loading your data into HIPE, and then what to know and do before you begin reprocessing your data with one of the pipelines. In addition, we take you through all the things you need to think about before reprocessing your PACS spectroscopy through the pipeline yourself:
    • why we recommend you do re-pipeline your data
    • what you need to pay attention to for different types of astronomical source
    • what the post-pipeline processing tasks are you can, or must, do
  Tutorials and scripts:
  • See the various walkthroughs on the NHSC PACS page.
  • HIPE Academy on YouTube: here you can find recordings of various seminars and webinars that the HSC have given on working in HIPE, reducing Herschel data, using various tools to visualise and manipulate data in HIPE, and etc.
  • In HIPE there is a Scripts menu in which you can find various "useful scripts" for working with PACS data in HIPE. For example, for spectroscopy there is a script showing how to fit the spectra in cubes and make integrated flux images from them; for photometry we show how to do point source aperture photometry. These are written as scripts which you can open in HIPE and run on a test dataset, and in most cases you can replace the test dataset with your own and take it from there. Please do note that these scripts do not explain how to use the GUI version of the tasks--for this you need to read the PDRGs or the general Data Reduction Guide.

PACS calibration file versions

  • When starting HIPE, you will be informed if new calibration files are available. Clicking on 'show details' will show you the release note of the new calibration set, with details about the changes. This is further explained in the PDRGs (chap. 2). Clicking on 'Install' will install the latest calibration files.
  • The history of the calibration files that have been released to the community is provided here: PACS Calibration File History
  • You can inspect the release notes for the calibration sets installed on your machine from within HIPE. Open the Calibration Sets View from the menu Window -> Show Views -> Workbench.
  • When reducing your data in HIPE you will normally use the latest version of the calibration tree that you have on disk (this happens by default), but you can chose to use a previous version instead. How to do this is explained in the PDRGs.

PACS calibration and performance

Photometer calibration in scan maps

  • 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

Photometer map-makers

Three fundamentally different map-makers are offered in Hipe 11 with ipipe scripts, starting from level 1 on pairs of obsids :

  • highpass filtering branch, where the bolometer timelines are highpass filtered to remove the 1/f noise at the expense of extended emission. It provides optimum sensitivity to point-sources.
  • MADmap, a GLS (generalized least square) map-maker, that allows to preserve extended emission at all scale.
  • JyScanam, a Java-version of the IDL Scanamorphos map-maker.

Another two public map-makers, also starting from level 1, widely used and both very easy to use are :

  • Scanamorphos, an IDL map-maker from Hélène Roussel (IAP) with an advanced and powerful destriper for PACS maps.
  • Unimap a light (memory wise) GLS map-maker from Lorenzo Piazzo ('La Sapienza' University of Rome ) under a free Matlab runtime environment, with an advanced pre-processing (drift correction, jump detection) and post-processing stages (bright sources).

A report of the map-making working group compiled by Roberta Paladini is available: PACS map-making tools: analysis and benchmarking, 1 Nov. 2013.

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. New issues of this document will be released with new versions of the pipeline and new versions of the calibration tree provided in the Herschel interactive data analysis system. Please note, the above linked document refers to the calibration status and performance of pipeline version v8.0. An update compatible with HIPE v9.0 release will be provided soon.

  • Data processing known issues of standard products: Browse quality Level 2 products are provided in the Herschel Science Archive. This summary page describes typical problems and caveats the observer needs to be familiar when looking at these preview products. Aspects of product quality which can be further optimised by interactive processing are also summarised here. The document refers to the version of data processing pipeline currently being used for processing of incoming Herschel data (version number provided therein).

  • PACS spectrometer beams, version 3,can be downloaded here: PCalSpectrometer_Beam_v3.tar.gz. These beams are based on measurements of a raster with step size 2.5" around Neptune. These beams are useful to compare the flux seen in the different IFU spaxels with with a point source, or a certain brightness distribution in the sky. Version 3 has the beam effiencies for all IFU spaxels, and has a drastic improvement wrt version 2 since the spacecraft pointing was reconstructed more accurately. This resulted in a non-equidistant sampling of the beam efficiency in the sky. The beam products offered are equidistantly sampled on a grid of 0.5 arcseconds. The central part of the beam is the Gaussian fit to the measured beam efficiencies. This has been verified to be a very good description on the different raster observations we have of the central spaxels for wavelengths longer than 80 micron. Below 80 micron, the actual beam shows the square detector footprint, and the Gaussian approximation in the beam products v3 overpredicts the real beam efficiency by 1.5 to 2 percent. The outer part of the beams contains the interpolated values of the irregularly sampled measurements. Thanks to the improved data reduction quality, version 3 of the spectrometer beams are sharper than version 2, and shows the ghosts (see also the PACS spectrometer calibration document) more clearly, as well as the three-lobe structure of the Herschel telescope PSF. Each beam is normalised to the fitted peak value of the central spaxel. The WCS associated with the beam is in sky coordinates for position angle 0.
  • The raw data from which the PACS spectrometer beams above have been derived, is also made available to the users in tables (y, z offset - signal):
    • SpecSpatial_BeamEfficiency_central_spaxel_tables_v1.tar.gz: Raw measurements PACS beams - central spaxel only. This contains a fits file for each wavelenght measured for the CENTRAL SPAXEL only. Raw data of the coarse and fine rasters are combined. The array dimension of the fits file is [3,npoints] where the first column gives the y raster position, the 2nd column the z raster position and the 3rd column the normalised flux measured at this raster position.
    • SpecSpatial_BeamEfficiency_tables_v1.tar.gz: Raw measurements PACS beams - all spaxels, coarse raster measurements only: each fits files corresponds to one wavelength. Each file contains the data for all spaxels of the coarse raster measurement only. Each fits file holds an array of 3x25x25x25 where: (0,25,25,25) : y raster position (1,25,25,25): z raster position (2,25,25,25): flux normalized to the central spaxel. The second and third dimensions are the raster position indexes (y and z) and the last dimension is the module number (=spaxel).

Planned processing and calibration improvements

  • The PACS ICC and the HSC calibration scientist teams are currently working on making the following processing and calibration improvements available to the users:
    • Making spectrometer convolution kernels available. These products will be useful to estimate line-ratios in oversampled spectral maps.
    • Improved a-posteriori pointing reconstruction based on guide star positions used for the observation and the gyroscope raw output.
    • Point source flux correction for observations not perfectly centered on the central spaxel.
    • Improved correction for systematics affecting the spectral shape of sources and detectability of unresolved lines.

Interest Groups and Scripts

Links

Topic attachments
I Attachment History Action Size Date Who Comment
PDFpdf ExpAstr_PrimeAsteroids_revision1.pdf r1 manage 928.3 K 2013-11-04 - 23:51 BrunoAltieri Mueller exp. astr. paper 2013
PDFpdf ExtSrcPhotom.pdf r1 manage 3303.5 K 2011-04-12 - 18:26 BrunoAltieri  
PDFpdf PACSPSF_PICC-ME-TN-029_v2.0.pdf r1 manage 3171.5 K 2010-11-05 - 16:28 BrunoAltieri  
PDFpdf PACS_LaunchPads_Dec2011.pdf r1 manage 116.3 K 2011-12-06 - 09:05 KatrinaExter PACS launch pads from PDRG of Nov 11
PDFpdf PACS_LaunchPads_Jun2013_S.pdf r1 manage 169.8 K 2013-06-07 - 13:12 KatrinaExter pacs spec launch page jun 2013
PDFpdf PACS_LaunchPads_May2012_P.pdf r1 manage 111.0 K 2012-05-25 - 14:28 KatrinaExter Photometry
PDFpdf PACS_LaunchPads_May2012_S.pdf r1 manage 137.7 K 2012-05-25 - 14:28 KatrinaExter Spectroscopy
PDFpdf PACS_Spec_DRG_0613b.pdf r1 manage 3112.5 K 2013-09-30 - 10:25 KatrinaExter PACS spec DRG track 11
Unknown file formatgz PCalSpectrometer_Beam_v1.tar.gz r1 manage 85.7 K 2011-07-14 - 23:08 BartVandenbussche PACS Spectrometer beams
Unknown file formatgz PCalSpectrometer_Beam_v2.tar.gz r1 manage 930.7 K 2012-01-16 - 12:49 BartVandenbussche PACS spectrometer beam effiencies, version 2
Unknown file formatgz PCalSpectrometer_Beam_v3.tar.gz r1 manage 17278.3 K 2013-03-05 - 15:06 BartVandenbussche PACS spectrometer beam efficiencies v3
PDFpdf PDRG_Dec2011.pdf r1 manage 6655.5 K 2011-12-07 - 10:05 KatrinaExter PDRG Track 8.0 RC6
PDFpdf PDRG_Jun2011.pdf r1 manage 5346.0 K 2011-06-07 - 22:27 KatrinaExter PDRG Jun 2011
PDFpdf PDRG_Phot_May12.pdf r1 manage 471.2 K 2012-05-25 - 14:24 KatrinaExter PDRG Photometry for May 2012
PDFpdf PDRG_Spec_May12.pdf r1 manage 2494.9 K 2012-05-25 - 14:10 KatrinaExter PDRG Spectroscopy from May 2012
PDFpdf PICC-CR-TN-044.pdf r1 manage 294.2 K 2013-05-09 - 15:01 BrunoAltieri The bandwidth of the PACS photometric system
PDFpdf PICC-NHSC-TN-029.pdf r1 manage 975.7 K 2011-04-12 - 18:30 BrunoAltieri  
PDFpdf PPR_Jun2011.pdf r1 manage 4338.0 K 2011-06-07 - 22:33 KatrinaExter PPR Jun 2011
PDFpdf PacsSpectroscopyPerformanceAndCalibration_31May2011.pdf r1 manage 2329.4 K 2011-06-02 - 13:28 JeanMatagne  
PDFpdf PacsSpectroscopyPerformanceAndCalibration_v2_4.pdf r1 manage 2056.7 K 2011-06-17 - 10:27 BartVandenbussche PACS spectrometer performance and calibration document, v2.4
PDFpdf PhotMiniScan_ReleaseNote_20101112.pdf r1 manage 1988.8 K 2011-06-06 - 17:05 BrunoAltieri  
PDFpdf SimulPSP_v1.0.pdf r1 manage 5323.7 K 2010-11-15 - 11:16 BrunoAltieri  
Unknown file formatgz SpecSpatial_BeamEfficiency_central_spaxel_tables_v1.tar.gz r1 manage 120.9 K 2013-03-08 - 17:41 BartVandenbussche Raw measurements PACS beams - central spaxel only
Unknown file formatgz SpecSpatial_BeamEfficiency_tables_v1.tar.gz r1 manage 2742.3 K 2013-03-08 - 17:43 BartVandenbussche Raw measurements PACS beams - all spaxels
PDFpdf aa14535-10.pdf r1 manage 1571.0 K 2010-11-04 - 16:23 BrunoAltieri  
PDFpdf balog_PACS_Phot_ADS.pdf r1 manage 432.5 K 2013-11-04 - 23:50 BrunoAltieri Balog exp. astr. paper 2013
PDFpdf bolopsf_20.pdf r1 manage 9635.3 K 2012-04-10 - 16:40 BrunoAltieri PACS photometer point spread function, v2.0
PDFpdf bolopsfv1.01.pdf r1 manage 5658.9 K 2010-11-05 - 16:27 BrunoAltieri  
PDFpdf cc_report_v1.pdf r1 manage 2578.7 K 2011-04-12 - 18:30 BrunoAltieri  
PDFpdf hpf_psf_tn_final.pdf r2 r1 manage 6492.6 K 2012-11-14 - 18:06 BrunoAltieri Effect of high-pass filtering
PDFpdf pacs_bolo_fluxcal_report_v1.pdf r1 manage 3122.3 K 2011-04-12 - 19:40 BrunoAltieri  
PDFpdf pacs_mapmaking_report_ex_sum_v3.pdf r1 manage 9781.5 K 2013-11-04 - 23:49 BrunoAltieri mapmaking report
PDFpdf pacs_phot.pdf r1 manage 4670.2 K 2013-01-22 - 15:13 BrunoAltieri PACS photometer PDRG Hipe 10
PDFpdf pacs_phot_June2013.pdf r1 manage 5138.2 K 2013-07-29 - 09:25 BrunoAltieri PACS photometer PDRG Hipe 11
PDFpdf pacs_spec.pdf r1 manage 2864.4 K 2013-01-22 - 15:13 BrunoAltieri pacs sepctrometer PDRG Hipe 10
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