mirror sites: PL (internal link) HQ     [?]

Quality Control and
Data Processing

CAL | HC | refs | QC
Trending & QC1
   IFS spectrum position
QC links:
SPHERE: IFS spectra positions
number of spectra, scale, format offset YJ
number of spectra, scale, format offset YJH
QC1 database (advanced users): browse | plot

IFS spectra position raw frame is acquired in IFU mode and shows broad band lamp spectra (an IFU flat field) to determine the identification and position of the spectra. The recipe generates one product with different extensions. Further recipes of the calibration cascade essentially append more and more extensions to this product with additional information

IFS spectral position raw frame.

IFS spectral position raw frame. Zoomed version

Zoom into extension "PDT.WAVELENGTH" of the IFS spectral position product, showing position of the spectra and the initial wavelength range.

IFS spectra positions


FITS key QC1 database: table, name definition class* HC_plot** more docu
QC.NUMBER.SPECTRA sphere_ifs_specpos..qc_number_spectra number of spectra HC [docuSys coming]
QC.SCALE.MEASURED sphere_ifs_specpos..qc_scale_measured measured scale HC [docuSys coming]
DRS.OFFSETX.MEASURED sphere_ifs_specpos..qc_offset_x measured offset HC [docuSys coming]
DRS.OFFSETY.MEASURED sphere_ifs_specpos..qc_offset_y measured offset HC [docuSys coming]
*Class: KPI - instrument performance; HC - instrument health; CAL - calibration quality; ENG - engineering parameter
**There might be more than one.


Both plots for YJ and for YJH show:

  1. The number of found slitlet spectra
  2. correcting scale to fit the lenslet model and the SPOS calibration slitlet center point pattern.
  3. The pixel offsets as a function of the optical bench temperature. The solid lines are empirical non-linear relations. The dashed line is the empirical relation before the earth quake in 2015-11 and shows the shift by 0.6 pixel introduced by this event.
  4. The pixel offset in x between the SPHERE IFS spectra positions of the raw input frame and the lenselet model.
  5. The pixel offset in y between the SPHERE IFS spectra positions of the raw input frame and the lenselet model.
  6. The pixel offsets in the XY-plane

Scoring&thresholds IFS spectra positions

All QC parameters are scored with very relaxed thresholds.


  • 2015-11-27:

    There was a 6.2 mag earth quake on 2015-11-27, which caused a shift of the OFFSET_X values by 0.6 pixel. The non-linear relation between the offset and the optical bench temperature before the EQ event is shown as a dashed line, the post EQ empirical relations are shown as solid lines and are:

    • YJ: OFFSET_X(Tbench) = 4.007 + 0.111 * Tbench - 0.00848 * Tbench * Tbench
    • YJ: OFFSET_Y(Tbench) = -4.369 + 0.010 * Tbench - 0.00837 * Tbench * Tbench

    • YJH: OFFSET_X(Tbench) = 7.159 + 0.0948 * Tbench - 0.00755 * Tbench * Tbench
    • YJH: OFFSET_Y(Tbench) = -1.022 + 0.0372 * Tbench - 0.00726 * Tbench * Tbench

  • 2017-04-05: The processing strategy was modified. SPOS calibrations are no longer processed using a IFS master dark. As a consequence the pipeline reports a different number of found spectra.
  • 2018-10-26T12: 'NO RISK' earthquake at 2018-10-26T12:31:07 introduced a huge offset in the spos values.
  • 2018-10-28: The IFS-arm is re-aligned

Algorithm IFS spectra positions

The differences between the lenselet model and the observed positions of the slitlets is obtained.

Send comments to <qc_sphere@eso.org> powered by QC [webCMS v1.0.1]