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PACS photometer pipeline overview. Maynooth, September 2010. Bruno Altieri (ESA/HSC). Two pipelines : photProject: High-pass filter + projection MADmap Common pipeline from L0 to L1 with branching to L2. HCSS 2.0: MADmap removed from HSC pipeline

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pacs photometer pipeline overview

PACS photometer pipeline overview

Maynooth, September 2010

Bruno Altieri (ESA/HSC)

pipelines current status
Two pipelines:

photProject: High-pass filter + projection


Common pipeline from L0 to L1 with branching to L2.

HCSS 2.0: MADmap removed from HSC pipeline

Too low quality maps (as cross scan not handled)

Memory problems

Plan: re-introduce in HCSS 5.0 once HCSS-9361 is implemented to handle cross-scans.

pipelines current status
photproject scan map pipeline
photProject scan map pipeline

Sequence to apply to PACS photo data cube (frames)

  • Flag bad pixels
  • Flag saturated pixels
  • Convert ADUs to Volts
  • Cross-talk correction
  • Pixel timeline deglitching (multi-median resolution)
  • Flat-field and responsitivity correction: Jy/pixel
  • Compute ra/dec for virtual aperture (centre)
    • Scan leg re-centering
  • Run high-pass filter, to filter 1/f noise
    • In two or more passes to mask out (bright) sources for high-pass
  • Project cube onto a grid to get WCS map
    • Computes the ra/dec for each pixel corners on the fly

Level 0 to 1

Level 1 to 2

photProject ?
  • High-pass + phoProject is more sensitive for point-sources.
  • Running MadMap over very large and deep PACS scan maps (e.g. cosmological surveys) prevented by serious memory problems
  • MadMap has still problems of residuals for bright point sources
  • PhotProject takes ~ 10 minutes for 1.5 h AOR with reasonable memory use
  • However iteration is needed to optimize results

axy geometrical weights

  • wxy error based weigths
  • drop size also customizable (75%, 50%, 25%, 12.5% of the input pixel size)
  • still error propagation not trustable
new photometer pipeline in hcss 4 1
New photometer pipeline in HCSS 4.1
  • A two-stage masked high-pass filtering pipeline proposed for HCSS 4.0:
    • A compromise to get reasonable maps on all fields.
    • PACS-2801, implemented by Ekki Wieprecht.
    • Simple principle :
      • Sources above a certain threshold are masked for the highpass filter
      • MMT deglitching disabled on sources
      • Larger filter width in the second pass to preserve extended emission up to a few arcmin.
  • To be used for the HSC bulk reprocessing (HCSS 4.1)
    • good photometry within 5-10% on all cal stars
    • no holes in the coverage map (deglitching)
    • no negative artifact around bright sources.
    • relative good point-source sensitivity.
    • preserve a significant fraction of extended emission.
what is madmap
What is MADmap?

Map-making technique which will produce maximum likelihood sky maps from time ordered instrument data.

MADmap uses the data model:

d = A(p,t) * S(p) + n(t),


d = detector readout, A=pointing matrix, p=sky pixel, S=signal, n=noise and t is time (or index).

For all readouts, all detectors, the set of linear equations is too large to invert; thus, conjugate gradient method is used to find the best least-squares fit to the data, given a noise model n(t).

implementation for pacs dp
Implementation for PACS DP

Cal. Files

Level 1 Processing*

2nd level deglitching

Pixel-to-pixel, module to module and global drift corrections.




Generate TOD



Naive Map

Optimal Map

* But see caveat about deglitching.

scan cross scan mandatory for madmap
Scan+cross-scan mandatory for MADmap

MADmap with Scan+x-scan

MADmap with Single scan

On-going work with HCSS-9361 to handle multiple scans

a new pipeline for the longer term
A new pipeline for the longer term
  • Scanamorphos is an IDL software to build maps from scan observations made with bolometer arrays, in particular with the PACS and SPIRE photometers
  • Scanamorphos is designed to remove the low-frequency noise, both thermal and non-thermal, causing additive brightness drifts. To this end, it makes use of the redundancy built in the observations (each portion of the sky with nominal coverage is sampled by multiple bolometers at multiple times) to derive the brightness drifts directly from the data themselves. This means that Scanamorphos does not depend on any noise model, and is thus immune to mismatches between models and reality, that may occur because the noise is not perfectly calibrated, or does not satisfy the model assumptions, or varies in time, or is altered by the pre-processing (from level 0 to level).
  • Scanamorphos is flux-conserving and restores sources on all spatial scales, ranging from point sources to extended structures with scales just below the map size.