Difference: PacsCalibrationWeb (150 vs. 151)

Revision 1512017-01-10 - KatrinaExter

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META TOPICPARENT name="WebHome"

PACS instrument and calibration web pages

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 NEW NEW NEW Latest and Coming Updates (10-Jan-2017)

  • HIPE 14.2.1 has been released
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  • SPG 14.2.2 products will soon be processed. Most of the PACS archive will not be reprocessed as the pipelines and calibration have not changed. Only a subset of observations require a reprocessing:
    • The Level 2.5 for all spectroscopy unchopped range scans: previously the Level 2.5 were created incorrectly
    • The Level 3 for all spectroscopy chop-nod pointed range scans: this is being done to have a correct "ObservationSummary" included in the observation dataset, however the data themselves will be no different as the processing has not changed
    • A few isolated spectroscopy observations (1342247513, 1342246558,1342225987, 1342225145, 1342225789, 1342247790)
  • Due to a bug fixed in the 6.4.4 Unimap release within 14.2.1, the values of some Unimap parameters have been modified for a small set of observations.

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  • Due to a bug fixed in the 6.4.4 Unimap release within 14.2.1, the values of some Unimap parameters were modified for a small set of observations in the SPG 14.2.1 processing.
  • SPG 14.2.2 products will soon run. This will be the final bulk processing of PACS data, however only a subset of PACS spectroscopy observations need to be processed with 14.2.2 to correct errors in the previous processing:
    • the Level 2.5 for all unchopped range scans: previously the Level 2.5 were created incorrectly
    • the Level 3 for all chop-nod pointed range scans: this is being done to have a correct "ObservationSummary" included in the observation dataset, however the data themselves will be no different as the has not changed
    • a few isolated spectroscopy observations (1342247513, 1342246558,1342225987, 1342225145, 1342225789, 1342247790)
  • HIPE 15 will soon be released. There are almost no differences in the data reduction software compared to HIPE 14.2:
    • for the spectroscopy interactive pipeline scripts, one task has been added which changes the values of two meta data: centreRaDecMetaData, which sets the "ra" and "dec" meta data to the centre of the cube's field for each cube created, independently; it does not change the data or coordinates of the cubes.
    • the calibration file dealing with the EEFs (encircled energy fractions, for photometry) has an additional set of entries
  • The forward modelling tool (FMT). This tool is to be used with PACS spectroscopy observations of objects which are extended but not flat over the observed field. It is to be used to estimate the correction to the fluxes necessary to account for the uneven illumination of the FoV by the PACS integral field unit (i.e. the gaps between the spaxels). See the Data Reduction section for more information.

 

Observing with PACS

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  • 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. Clicking on Install will install the latest calibration files.
  • 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.
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  • The history of the calibration files that have been released to the community is provided here: PACS Calibration File History. With the release of HIPE 15 (early 2017) and the final SPG processing of 14.2 (earlier 2017), no more changes to the calibration tree will be made.
 

Reducing PACS data

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FMT (forward modelling tool). Some information about this is provided in the spectroscopy PACS Data Reduction Guide. A quick summary is:
  • the FoV of the PACS integral field unit is not uniformly illuminated, which leads to some loss of light between the spaxels
  • for point sources and flat sources this does not matter -- the corrections applied by the pipeline (the point source corrections in extractCentralSpectrum, for example, and the extended source correction applied to all observations by the pipeline) account for this
  • for sources that are between a point and fully extended, for crowded fields, and for off-centred point sources, however, the fluxes in the final cubes of the pipeline will be incorrect

The FMT has been developed in HIPE 15 to estimate the degree to which the fluxes are incorrect for any observation. As this differs for each observation -- it depends on the surface brightness distribution of the source and the pointing pattern of the observation (pointed, Nyquist mapping, oversampled mapping, tiling...) -- the correction is unique to each observation. To use the FMT it will be necessary to run HIPE. The most important input is a model of the surface brightness distribution of your source at the wavelength(s) of the observation. With this input, the surface brightness distribution that would have been observed with a completely uniform illumination is estimated by running the pipeline on the model. This output can be compared to your data.

The FMT is fully incorporated in HIPE 15, however it has not yet been tested on general users, and for this reason we recommend you to contact the Herschel helpdesk to ask for advice on running the code. In exchange for some one-on-one help, we would appreciate feedback on the scripts and the documentation provided in the FMT package.

 

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.
  • The PACS Launch Pads 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. These can be gotten via HIPE itself or the links here (these are to the HIPE 15 versions, which are the same as the HIPE 14 versions)
 
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