TWiki> Public Web>PacsCalibrationWeb (revision 102)EditAttach

PACS instrument and calibration web pages


This page provides up-to-date information about using the PACS instrument: from preparing observations to reducing your data. This includes information on the PACS instrument, PACS data, reducing PACS data in HIPE, and post-pipeline processing, and links to tutorials and scripts that you can run in HIPE. The calibration accuracies and technical information about the spectrometer and photometer of PACS are also provided here, as well as 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 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
    • A description of the scientific capabilities of the instrument: spectral response functions, sensitivity values, point spread functions, astrometric accuracy, flux calibration information
    • A description of the standard observing templates used to set up PACS observations; here you can also find the various acronyms that are used in the PACS data reduction guides
    • A brief description of PACS data products (although much more detail is provided in the appendices of the PACS data reduction guides)

  • AOT Release Notes: dedicated release notes per AOT (the astronomer's observing template, i.e. the observing time planning).
    • Information about how the various standard observing blocks work
    • Summaries of transmission functions, sensitivity, etc. for use in your observing planning (similar to what you will find in the Observer's Manual)
    • Here you can also find the various acronyms that are used in the PACS data reduction guides
    • 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

A summary of the PACS instrument for an astronomer

Here we provide a summary of instrumental and calibration details that a data-reducing astronomer often wants know. The summary provides a set of links or information about where to find the information.


  • Wavelength ranges and limits, band names
    • The blue bands are B2A (blue, second order) and B2B (green, second order), and B3A (blue, third order), and in the red we have R1 (first order)
    • The wavelength ranges and resolutions can be found in Table 4.1 of the PACS Observer's Manual (here for the HTML version)
  • The footprint of the integral field unit: text and figures showing the footprint of the PACS IFU, and how that compares to the beam, can be found in the PACS Spectrometer Calibration Document v2.4 (16-June-2011) (sec. 3) where you will also find information about the beam maps (at high spatial resolution and for various wavelengths), beam efficiencies, and the point source loss corrections. This is mentioned again in the 'PACS spectrometer calibration' section below. The same information can be found in the PACS Observer's Manual (sec. 4.6)
  • The spatial FWHM of a point source: this information can be found in fig. 4.12 of the PACS Observer's Manual and again in the PACS Spectrometer Calibration Document
  • Spectral leaks: there is order leakage in our filters that affects the ends of the blue and red bands. These are documented as figures in sec. 4.1 of the PACS Spectrometer Calibration Document and again in sec. 4.8 of the PACS Observer's Manual . Dealing with this leakage by reducing the data with a particular calibration file is documented in the PACS spectrometer data reduction guide (in the pipeline chapters where the flatfielding task is discussed, and sec. 8.3)
  • Ghosts: see sec. 4.2 of the PACS Spectrometer Calibration Document to learn about ghosts - echos of spectral lines from one wavelength to another from one spaxel to another. This is also documented in sec. 4.9 of the PACS Observer's Manual
  • Skews for off-centred sources: point sources that are not centrally located in a spaxel will show a skew to their spectral lines (although if the lines are faint this may not be obvious). Some calibration of this has been done and this can be found in sec. 4.7.2 and 4.7.3 of the PACS Observer's Manual and sec. 5.2 of the PACS Spectrometer Calibration Document. Some more information concerning how to tell whether your source's offset should lead to a skew can be found in the PACS spectrometer data reduction guide, sec. 7.5
  • Calibration certainties: these are all documented in the beginning of the PACS Spectrometer Calibration Document
  • Names of the AOTs and what they mean: can be found in the AOT Release Notes
  • Expected signal-to-noise ratios and line sensitivity: this depends on the AOT, this information is also provided in the AOT Release Notes


  • Filters and bands
    • The blue and green bands are not observed simultaneously, the red is observed simultaneously with each. Transmission functions can be found in the PACS Observer's Manual sec. 3.2.
  • PSF and beams: the beams maps as FITS files, and information about then can be found below in the section 'Photometer calibration in scan maps'
  • Point source photometry
    • Colour corrections: these are provided below in the section 'Photometer calibration in scan maps'
    • Aperture corrections/eefs (encircled energy fractions) are provided in sec. 8 of the PACS Photometer Point Spread function document
  • Effects of nonlinearity, saturation, stray light, crosstalk and ghosts: can be found in sec. 6 of the PACS Photometer Point Spread function document
  • Calibration certainty: is discussed below in the section 'Photometer calibration in scan maps' (item 'Point-source photometry'), with links there to two publications. You can also read sec 3.3 of the PACS Observer's Manual
  • Names of the AOTs and what they mean: can be found in the AOT Release Notes
  • Sensitivity: this depends on the AOT, this information is also provided in the AOT Release Notes

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.
  • 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 (e.g. mapping or single pointing for spectroscopy). 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), meaning that they are processed with a tailored version of the latest pipeline scripts from the User Release. For example, 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.
  • These SPG scripts are a copy of one flavour of interactive pipeline scripts, differing only on the AOT type. The SPG scripts include all the stable pipeline tasks with settings that correspond to the most common type of science target for each AOT. But some pipeline tasks can only be run via the interactive pipeline scripts, and to modify the important parameter settings for pipeline tasks also requires you re-run the pipeline. The Launch Pads (see below) include a guide to understanding the pipeline scripts and how to decide which to run.
  • 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.

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: 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 full documentation-set provided via HIPE includes the following:
    • The PACS (HIFI and SPIRE) DRGs. The main function of the PACS DRGs (photometry and spectroscopy) is to take you through reducing your data with the interactive pipeline, explaining the steps and the individual tasks in more detail and showing you how to inspect your results. This makes them rather long documents, and they should be read along with the pipeline scripts rather than on their own. They also show you how to quick-look at the SPG products 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).
    • The 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.
    • The Scripting Guide: the language of HIPE is 'HIPE's version of jython', and it is 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. It is not necessary, but it does help, if you are already comfortable with scripting before embarking on scripting in HIPE.
    • Reference manuals. For most of the tasks that you can run in HIPE the description of what they do and listings of all the parameters can be found in the 'User's Reference Manual'. To learn more about the various HIPE product classes you can read the JAVA docs (APIs) a.k.a. the 'Developer's Reference Manual'. 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 various pipeline scripts PACS photometry and spectroscopy provide can be seen as cookbooks, since they take you through each pipeline, task by task (on the command-line), 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 PACS Launch Pad from June 2013 for photometry is provided here. The PACS Launch Pad from July 2013 for spectroscopy is provided here. These are taken from the first chapter of the respective PDRG 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 post-pipeline processing tasks are you can, or must, do

Tutorials and scripts

  • 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

  • Data processing known issues of standard products for photometry and spectroscopy: Browse quality Level 2/2.5 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).

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 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. (Please note, this document refers to the calibration status and performance of pipeline version v8.0. An update compatible with HIPE v12.0 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
    • wavelength calibration, including information on a skew our native line profile develops as a point source moves off the centre of a spaxel
    • table of the point source correction factors for different wavelengths
  • The calibration of the spectrometer is based on repeated measurements of planets, asteroids, and stars. The RMS scatter of these measurements are just over 10% within any spectral band, about the same when comparing different spaxels, and similar (but higher in the red) when looking for broad-band features within any band. These calibration certainties are independent, and should be combined when quoting errors in science papers. Read the above-mentioned document for the most up-to-date information.

  • 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 wavelength 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 indices (y and z) and the last dimension is the module number (=spaxel number).

  • Point source observations. We provide a task at the end of the pipeline scripts to extract the spectrum of point sources, corrected for flux losses due to the PSF being larger than the spaxel size, and including a correction for flux losses due to small pointing offsets from the centre of the the central spaxel and pointing jitter. This task (extractCentralSpectrum) is used on cubes of a single pointing (i.e. not those created from combine several raster pointings) and must be run in order to correctly extract the spectrum of point sources. This task uses the beams we refer to above. The pros and cons and how and when to use the task are documented in the spectrometer PDRG (in the pipeline chapters and again in chap. 7).

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.
    • Improved correction for systematics affecting the spectral shape of sources and detectability of unresolved lines.

Interest Groups and Scripts


Topic attachments
I AttachmentSorted ascending History Action Size Date Who Comment
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 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 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_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_mapmaking_report_ex_sum_v3.pdf r1 manage 9781.5 K 2013-11-04 - 23:49 BrunoAltieri mapmaking report
PDFpdf pacs_phot_June2013.pdf r1 manage 5138.2 K 2013-07-29 - 09:25 BrunoAltieri PACS photometer PDRG Hipe 11
PDFpdf pacs_phot.pdf r1 manage 4670.2 K 2013-01-22 - 15:13 BrunoAltieri PACS photometer PDRG Hipe 10
PDFpdf PACS_Spec_DRG_0613b.pdf r1 manage 3112.5 K 2013-09-30 - 10:25 KatrinaExter PACS spec DRG track 11
PDFpdf pacs_spec.pdf r1 manage 2864.4 K 2013-01-22 - 15:13 BrunoAltieri pacs sepctrometer PDRG Hipe 10
PDFpdf PACSPSF_PICC-ME-TN-029_v2.0.pdf r1 manage 3171.5 K 2010-11-05 - 16:28 BrunoAltieri  
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
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 PhotMiniScan_ReleaseNote_20101112.pdf r1 manage 1988.8 K 2011-06-06 - 17:05 BrunoAltieri  
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 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
Edit | Attach | Watch | Print version | History: r162 | r104 < r103 < r102 < r101 | Backlinks | Raw View | Raw edit | More topic actions...
Topic revision: r102 - 2013-12-11 - KatrinaExter
This site is powered by the TWiki collaboration platform Powered by Perl