Difference: PacsCalibrationWeb (135 vs. 136)

Revision 1362016-07-06 - ElenaPuga

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META TOPICPARENT name="WebHome"

PACS instrument and calibration web pages

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 You can also consult the PACS NHSC homepage.

Temporary notes

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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.

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.

Photometry

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Observing with PACS

 
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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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The relevant documentation to read before working on PACS data for the first time are the following:
 
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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:
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    • 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
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Although we are now in the post-operations phase of the mission, the PACS OM and the AOT release notes can still be useful to read for a background understanding on how PACS data were gathered
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Although we are now in the post-operations phase of the mission, the PACS OM and the AOT release notes can still be useful to read for a background understanding on how PACS data were gathered.
 
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The In-flight scientific capabilities of the PACS instrument are also given in this paper: The Photodetector Array Camera and Spectrometer (PACS) on the Herschel Space Observatory (1.5 Mb), Poglitsch et al., 2010, A&A, 518, L2
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PACS calibration and performance

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Data processing known issues of standard products for photometry and spectroscopy: Bulk-processed Level 2/2.5 products are provided in the Herschel Science Archive. This Data Processing Known Issues page describes typical problems and caveats the observer needs to be familiar when looking at the results of this "SPG" (standard product generation) processing. 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.
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Data processing known issues of standard products for photometry and spectroscopy:

The Herschel Science Archive provides bulk-processed Level 2/2.5 products. This Data Processing Known Issues page describes typical problems and caveats the observer needs to be familiar when looking at the results of this "SPG" (standard product generation) processing. 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.

 

Photometer calibration in scan maps

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Photometer map-makers

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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.
    • 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
    • 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
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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.
  • 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
  • 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
 Highpass filtering provides optimum sensitivity to point-sources while JScanam, Unimap and MadMap mappers all clean the dataset of systematic effects and remove the correlated 1/f noise, preserving at the same time the sky signal over large spatial scales. They are suited for analysing both point sources and extended emission.

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PACS calibration file versions

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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.
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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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  • 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.
 

Reducing PACS data

A brief introduction to reducing PACS data in HIPE. You can consult the PACS Data Reduction Guides (photometry and spectroscopy; available via HIPE) for more detail.

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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.
 
  • 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.
 

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 v14.0 It can be downloaded from: here. 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.
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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 v14.2 It can be downloaded from: here. In the CIB (continuous integration build) this version corresponds to Track 14, build 3595. 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.
 
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  • 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.
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  • The what's new in HIPE 14 page lists the changes in HIPE version 14.2 with respect to the 14.0 series, and provides a detailed list of updated functionalities, product changes, and calibration aspects.
 
 
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