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ISAAC Quality Control:
Spectroscopic flats

CAL | HC | refs | QC
Trending & QC1
Data Packages
Data Management
QC links:
lamp intensity | product frame statistics
lamp intensity
off-lamp parameters
window means
window stdev
QC1 database (advanced users): browse | plot
   Click on CURRENT to see the current trending (Health Check).
   Click on HISTORY to see the historical evolution of the trending.

Spectroscopic flats are taken for two gratings (LR and MR) and two arms (SW and LW). You will find the following abbreviations:

  • SSFL short wavelength spectroscopic flat using the LR grating
  • SSFM short wavelength spectroscopic flat using the MR grating
  • LSFL long wavelength spectroscopic flat using the LR grating
  • LSFM long wavelength spectroscopic flat using the MR grating

The isaac spectroscopic flat recipe takes 6 flat frames, consisting of three lamp=off frames and three lamp=on frames. The median of the lamp=off is subtracted from the median of the lamp=on frames and is normalized.
top lamp intensity

Two lamp intensities are monitored: the lamp=on intensity and the lamp=off intensity.

QC1 parameters

parameter QC1 database: table, name procedure
lamp intensity isaac_spflat, qc_specflat_ncounts

- The intensity of the halogen lamp as measured by the detector at a fixed DIT depends on the lamp amplifier and on the spectroscopic setting and the alignment of optical elements in the ray path. The lamp=off frame is subtracted from the lamp=on frame and the net flux as calculated by the isaac_spc_flat recipe is monitored. Day-time spectroscopic flat calibrations come in three pairs of lam=on/off frames. Night time calibrations (attached calibrations) come as one pair. The plots show the lamp flux per grating and per wavlength band, the different slits are marked by different symbols.

residual (thermal) light isaac_spflat, flux_off, flux_on

- The off-lamp frames register thermal radiation in the optical path in the wavelength band specific for the used filter. The QC parameter is simply the median of the off-lamp frames within x1,y1=412,412 x2,y2=612,612 . This parameter is sensitive to light leaks in the spectroscopic mode. There is a difference between a dark and an off-lamp frame: The off-lamp frames have a broad band filter in the path, the dark frame two narrow band filters mutually excluding in wavelength range.

  isaac_spflat, stat_off, stat_on - Statistical noise in the raw off-lamp and on-lamp frames is registered and ingested in the QC1 database but not trended. The stdev is used.


top product frame statistical parameters

QC1 parameters

parameter QC1 database: table, name procedure
mean values per quadrant window isaac_spflat, mean_UL, mean_UR, mean_LL, mean_LR

- The mean intensity is measured in quadrant window of the MASTER_SP_FLAT product. The mean values are extracted using the eclipse command stcube using the following command line option:
UL : --zone '256 512 512 768'
UR : --zone '512 512 768 768'
LL : --zone '256 256512 512'
LR : --zone '512 256 768 512'
Meaning the window in the upper left quadrant expands from x1,y1=256,512 to x2,y, = 512 768. The windows have been chosen such that they match the illuminated region also in the case of intermediate wavelength range filters like the SZ filter. All four values are close to 1 in the normalized product flat. Contrary trends in the Left versus Right values indicate changes in the spectrum slope.

stdev values per quadrant window isaac_spflat, std_UL, std_UR, std_LL, std_LL

- The standard deviation is derived from the same samples as for the mean_UL etc values. The non-robust QC parameter is sensitive to debris.



  • 2007-08-08 Hawaii: debris at @590,@800