Difference: SpireCalibrationWeb (132 vs. 133)

Revision 1332015-12-01 - IvanV

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Spectrometer data reduction

 
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Spectrometer data reduction

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Spectrometer Overview

 
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Spectrometer Overview

 The best source of information for reducing SPIRE Spectrometer data is the SPIRE Data Reduction Guide available through the HIPE help. This runs through the User Pipeline scripts step by step, describes several other Useful Scripts, and offers advice for specific types of sources:
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  • Faint (<10 Jy) and medium (<100 Jy) strength sources
  • Bright sources (>500 Jy)
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  • Faint (<10 Jy) and medium (<100 Jy) strength sources
  • Bright sources (>500 Jy)
 
  • Semi-extended sources
  • Spectral mapping observations
  • Observations with few repetitions

For faint sources, the subtraction of instrument, telescope and background emission is particularly important. Optimum subtraction can be performed in several ways (read the SPIRE Data Reduction Guide for details):

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  1. Subtract the Dark Sky spectrum closest to your observation (use the "Background Subtraction" script in HIPE)
  2. Subtract the spectrum of surrounding detectors (use the "Background Subtraction" script in HIPE)
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  1. Subtract the Dark Sky spectrum closest to your observation (use the "Background Subtraction" script in HIPE)
  2. Subtract the spectrum of surrounding detectors (use the "Background Subtraction" script in HIPE)
  Dark Sky observations are observed on every SPIRE Spectrometer OD, and are all public in the Archive.
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A listing of the available Dark Sky observations can be found here.
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A listing of the available Dark Sky observations can be found here.
 
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Spectrometer Data Processing Issues

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Spectrometer Data Processing Issues

  The SPIRE Spectrometer DP known issues listed here.
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Photometer data reduction

 
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Photometer Overview

 
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Photometer data reduction

Photometer Overview

 The best source of information for reducing SPIRE Photometer data is the SPIRE Data Reduction Guide available as a standalone hyperlink document as well as through the HIPE help. This runs through the User Pipeline scripts step by step, describes several other Useful Scripts, and offers advice for specific issues that might be encountered.
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Photometer Data Processing Issues

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Photometer Data Processing Issues

  The SPIRE Photometer DP known issues listed here.
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Known Issues in ODs 1304 & 1305

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Known Issues in ODs 1304 & 1305

  For (yet) unknown reasons, the three detectors PSW-B5, PSW-E9 and PSW-F8 - that use to behave well during the entire mission - were noisy during the two operational days 1304 and 1305. The result are stripes visible in the final PSW map which the current (HIPE 11) pipeline is not able to correct. The solution is to mask and exclude these detectors from the analysis. This could be done in 2 ways:
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  1. You can use the SpireMaskEditor GUI as described in Sec. 8.4 of the SPIRE Data Reduction Guide: write-click on your observation context variable and then select Level1_SpireMaskEditor and set to Master all samples in all scans (listed as BBID) for the detectors mentioned above.
  2. Alternatively, you can use these lines of code
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  1. You can use the SpireMaskEditor GUI as described in Sec. 8.4 of the SPIRE Data Reduction Guide: write-click on your observation context variable and then select Level1_SpireMaskEditor and set to Master all samples in all scans (listed as BBID) for the detectors mentioned above.
  2. Alternatively, you can use these lines of code
 
  • After either of those cases, you must then re-run level 1 to 2 steps on the newly modified level1 product. If your observation has been already re-reduced with HIPE 11, original and new level1s are already destriped, so you can directly run the naive map-maker on the new level1. Otherwise, you must run the destriper step: check the pipeline script for details.
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Planck-HFI & Herschel-SPIRE cross calibration: absolute offset re-processing

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Planck-HFI & Herschel-SPIRE cross calibration: absolute offset re-processing

  As of HCSS 11, a new task named zeroPointCorrection is available to the users: this task calculates the absolute offset for a SPIRE map based on cross-calibration with HFI-545 and HFI-857 maps, colour-correcting HFI to SPIRE wavebands assuming a grey body function with fixed beta.
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 A detailed descirption of the algorithm used for the cross-calibration with Planck and implemented in the zeroPointCorrection is described in the HIPE 11 SPIRE Data Reduction Guide, sec. 4.10. -->
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Source Extraction and Photometry

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Source Extraction and Photometry

 
  • The current recommended method for photometry sourceExtractorTimeline task (formerly known as the Timeline Fitter) which works on the detector timelines. The Map based algorithm sourceExtractorSussex (SUSSEXtractor) providers good results and is useful on larger maps where the sourceExtractorTimeline will be significantly slower. sourceExtractorDaophot (DAOphot) also provides a reasonable estimate of the source flux but may require an aperture correction.

  • Photometry on single direction fast scan parallel mode maps:
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    • The photometry on single scan direction fast parallel mode results in higher photometric errors of up to 5 percent for aperture photometry compared to nominal speed and cross linked maps. The best results are obtained using the Timeline Fitter. Wherever possible orthogonal and nominal direction parallel scans should be merged.
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    • The photometry on single scan direction fast parallel mode results in higher photometric errors of up to 5 percent for aperture photometry compared to nominal speed and cross linked maps. The best results are obtained using the Timeline Fitter. Wherever possible orthogonal and nominal direction parallel scans should be merged.
 
    • Currently no astrometry correction is made during the merging process for parallel maps. For fast parallel mode an astrometry offset may be present which can in cases where there is a large offset, result in reduced photometers accuracy of the order of up to 25% compared to large cross-linked scan maps.
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  • In HIPE13 (and HIPE 11), the default PRF used by SUSSEXtractor has a size of 5x5 pixels. In HIPE 12, a PRF of size 13x13 was used to allow a more complete coverage of the PRF edges, but this lead to some secondary effects that negatively affected the measured flux densities. If you use HIPE v12 we advise you to change the input PRF size using this script, in order to obtain the same photometry as in HIPE v13.

 
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