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GIRAFFE Quality Control:
calibration lamps

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QUALITY CONTROL
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GIRAFFE QC
Trending & QC1
   lamp stability
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GIRAFFE ...
QC links:
sim. lamp | FF lamp | Nasmyth flat lamp | ARC lamp
 
QC PLOTS
  CURRENT HISTORY
sim. arclamp:
QC1 database (advanced users): browse | plot
FF lamp stability:
Nasmyth FF lamp:
ARC lamp:
   Click on CURRENT to see the current trending (Health Check).
   Click on HISTORY to see the historical evolution of the trending.


These calibration lamps are monitored presently:

  • the arclamp of the simultaneous calibration unit
  • the flat field lamp on the fibre positioner calibration unit ("robotic flat")
  • the arc lamp on the fibre positioner calibration unit
  • the nasmyth lamp ("nasmyth flat")

Their efficiency is monitored to discover aging effects, as well as filter degradation or problems with the gripper.

top Simultaneous arclamp

An exposure (about 120 sec integration time) with the arclamp of the simultaneous calibration unit is daily taken, for each of the five fibre systems. These data are used to monitor the grating stability and also the lamp stability. Find a description of the calibration files here.

One emission line in one of the simultaneous calibration fibres is selected. Its flux is integrated (in counts per sec) and monitored over time. This is done for each slit separately.

QC1 parameters

parameter QC1 database: table, name procedure
lamp flux giraffe_simlamp..flux flux = mean_signal/exptime [ADU/sec]
exposure time giraffe_simlamp..exptime in sec

Trending

The trending plot has two panels, one with the fluxes from the five HR settings, one with the fluxes from the Medusa1 LR setting (all are taken as daily health checks).

Plots 1-5: Upper panel, fluxes of the simultaneous calibration arclamp in the five HR settings.

Panel 1 shows the lamp flux (in counts per sec) as measured in each slit system with the HR setting (H525.8B). It shows the lamp performance modulated by the fibre efficiencies. The flux difference between the Medusa and the IFU/Argus systems is due to the different fibre diameter (1.2 arcs versus 0.5 arcs).

Plot 6: Lower panel, the same for Medusa1 L543.1

The second panel shows the fluxes for the Medusa1 LR grating.

If a certain trend effect is visible in *all* slits, it is likely to be caused by the lamp. If it shows up in one fibre system only, it originates in that particular fibre system.

History

The total lamp flux usually slowly increases with time. It is dimmed electronically when it exceeds a certain threshold, to avoid saturation. This happened in 2004-02 and again in 2007-03. In 2005-07 ... 2005-09, the lamp faded and needed to be stabilized.

top Flat field lamp (robotic)

The performance of the robotic flat-field lamp is measured in a pattern involving the L543.1 setup in every slit system. A single flat frame is measured. The mean exposure level of the raw file is measured and normalized by the exposure time, the result comes in ADU/sec.

The lightpath between the lamp and the detector also includes interference filters. Hence any effect observed in the efficiency trending could be due to either the lamp or the filter.

QC1 parameters

parameter QC1 database: table, name procedure
lamp efficiency giraffe_flat..flux flux = mean_raw/exptime [ADU/sec]
mean signal giraffe_flat..mean_raw measured across whole frame
exposure time giraffe_flat..exptime  
type of flat giraffe_flat..flattype here: always ROB = robotic

Trending

Panels of the trending plot:
Boxes 1-5: FF lamp efficiency. Data are from HC calibrations in the L543 setup, for all five fibre systems

The lower panel shows the same data, plotted together, to reveal any slit-specific effects.

Box 6: Same data as above, all fibre systems plotted together. In this plot, "coherent" changes in the signal can be best seen, indicative of a lamp problem, as opposed to changes in a single fibre system indicating a problem with that fibre system.

Plots of spectrally resolved relative fibre transmission can be found here.

History

date event
around 2007-10-01 flux strongly decreased due to gripper problem; adjusted properly afterwards
around 2008-01-14 Low flux observed, due to bad positioning of the calibration mirror located inside of the OzPoz calibration unit

topNasmyth flat lamp

Argus nasmyth flats (flattype=NAS) are acquired everytime the standard star efficiency monitoring is executed (every 1-2 months). Furthermore it may also be triggered by an Argus SCIENCE OB and a standard star exposure. These flats provide a better relative illumination than the robotic flats, so that the relative fibre signal level is more evenly distributed.

The average flux is obtained by dividing the average signal in the first raw file by the EXPTIME.

Nasmyth flats also exist for IFU1 and IFU2 but are so sparsely distributed over time and settings that a trending is impossible.

QC1 parameters

Same as for robotic flats:

parameter QC1 database: table, name procedure
lamp efficiency giraffe_flat..flux flux = mean_raw/exptime [ADU/sec]
mean signal giraffe_flat..mean_raw measured across whole frame
exposure time giraffe_flat..exptime in sec
type of flat giraffe_flat..flattype here: always NAS = nasmyth

Trending

Box 1: Nasmyth lamp efficiency (Argus, L543.1).

Box 1 of the trending plot displays the Argus L543.1 values. This setup is used by the Argus STD efficiency monitoring, and also complies with the setup used for the robotic flat lamp monitoring.

Box 4: Nasmyth lamp efficiency (all settings). Blue marks
the L543.1values, green the HR settings, red the LR settings.

Box 4 in the trending report collects all existing nasmyth lamp data for Argus, to give an indication about the wavelength dependency of the lamp efficiency. 

date event
around 2007-02 flux in the L543.1 setting increased, to provide better statistics

top ARC lamp

The performance of the robotic arc lamp is measured in a pattern involving two settings: the high-resolution H525.8B setup, and the low-resolution L543.1 setup. The former is measured in every slit system, the latter only in the two Medusa's. The pattern repeats every week. The mean exposure level of all emission lines in the raw file is measured and normalized by the exposure time, the result comes in ADU/sec. Note that the signal from the SIMCAL fibres affects the average value as delivered by the pipeline. Therefore the final QC1 value is currently calculated using fibres #2...#10 only. This fibre range is free from SIMCAL signal.

QC1 parameters

parameter QC1 database: table, name procedure
lamp efficiency giraffe_wave..lamp_effic lamp_effic = mean_raw/exptime [ADU/sec]
mean signal giraffe_wave..mean_raw measured across whole frame
exposure time giraffe_wave..exptime  

Trending

Panels of the trending plot:

Fig. 1-5: ARC-lamp efficiency, high-resolution grating (H525.8B), all fibre systems
Fig. 6,7: low-resolution grating (L543.1), Medusa1 and Medusa2

Boxes 1-5: ARC-lamp efficiency (high-resolution setting H525.8B).

The lower panel shows the low-resolution Health Check setting, L543.1, for Medusa1 and Medusa2.

Boxes 6, 7: ARC-lamp efficiency (low-resolution setting L543.1).

History

date event
2006-06-01 ARC-LAMP flux re-adjusted to smaller values
around 2007-10-01 ARC-LAMP flux strongly decreased due to gripper problem; adjusted properly afterwards ; during that time the quality of the dispersion solution was reduced
around 2008-01-14 Low flux observed, due to bad positioning of the calibration mirror located inside of the OzPoz calibration unit

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