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Health Check monitor


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HealthCheck Monitor
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fibre stability (historical)
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GIRAFFE trending system: HEALTH CHECK plot
Last update: 2020-10-12T06:34:45 | last data from:
same group: Medusa1 Medusa2   IFU1 IFU2   Argus
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- png plot file
- png 2D display
- details per fibre
- measurements
2011-11-17 M1 washed, fibre pattern slightly changed
2011-12 FPS#27 back but then disabled again
This plot

NOTE: This set of plots has been maintained until 2020-3. It is NOT continued since then.

This is the trending plot for monitoring response and stability of the Giraffe fibres. Its purpose is to identify and monitor both fibre efficiency and stability. It helps identifying fibres with particularly low response, or unstable response. This may be useful e.g. for assigning sky fibres in the Medusa case.

Input data are the Health Check fibre flats taken approximately every third day for the Medusa slits, and once a week for the IFu and Argus slits. The pipeline extracts the fibre signals and calculates relative efficiencies per fibre (normalized). These are averaged in chromatic (Y) direction and stored in a binary table, as a single transmission, or response, value per fibre. This table is appended as extension #1 to the product files with pro.catg=FF_EXTSPECTRA.

Note that all of these files are robotic flats. Nasmyth flats are not included here because of their irregular acquisition, despite their better illumination pattern.

The transmission numbers (columns FPS = fibre position index, and TRANSMISSION) are collected for all HC flats of a given 3 month period. Contrary to traditional QC parameters, they form a QC vector: one set of 135 (Medusa) or 317 (IFU, Argus) QC values per measurement.

They are analyzed numerically to extract, per fibre, the following parameters:

  • mean efficiency
  • rms of the mean efficiency
  • an evaluation flag to mark broken fibres (no signal, coded as transmission -999), unstable fibres (the ones with an rms in excess of 3%), marginally unstable fibres (rms > 1%). SIMCAL fibres are excluded from the analysis.

Each transmission vector is normalized to give the same average transmission (excluding broken fibres), so that subtle normalization differences hopefully cancel out and the rms values indeed reflect fibre instabilities only.

The two plots on top display the following:

  • in the top plot, all mean efficiency vectors of the investigated period are plotted on top of each other. The abscissa is fibre index (FPS), the ordinate normalized efficiency. The SIMCAL fibres are marked red. For Medusa fibres, the broken blue lines indicate the fibre subslits. Broken fibres show efficiency 0.
  • Below are the rms values indicating the fluctuation per fibre. The green dots are within the 3% fluctuation limit, the red ones above. Values in excess of 5% are truncated.
  • The 2D plot shows again the mean efficiency vectors, now displayed in a 2D sequence with fibre index as X axis, time (increasing towards the top) as Y axis, and efficiency coded as greyscale. The SIMCAL fibres are marked by dots. Every fifth line is also marked by a tickmark. This plot helps to discover patterns (induced e.g. by illumination problems).

The 2D plot has ticks on the Y (time axis) to mark every fifth measurement, and on the X axis (fibre index) marking the SIMCAL fibres.

The stability evaluation can be downloaded under "details per fibre". The list of input measurements (with dates, file names etc.) is available under "measurements". It also includes the currently missing (broken) fibres (if any). For quick reference, the currently missing fibres are also displayed on the top plot.