Health Check monitor

This is the instrument performance plot for the system efficiency of GIRAFFE. It is based on measurements of a flux standard star with the Argus IFU under photometric conditions. There are three settings taken with the low-resolution grating (L427.2, L543.1, L881.7) and three more with the high-resolution grating (H447.1A, H651.5B, H875.7). These data are taken approximately every month.

They are calibrated with the robotic lamp flats. The flats are used only for the localization solution (required for the extraction). Contrary to the usual reduction, the extracted flat-field is not divided into the standard star spectrum, in order not to corrupt the efficiency calculation.

We display the QC1 parameter mean_effic which is the ratio of detected photons and the incident photons. The signal from all fibres (excluding SKY and SIMCAL) is combined and averaged.

For comparison we also plot the current ETC values at the central wavelength of the setting. Check out the ETC for more.

The reference values are defined as best-performance values. The efficiency is expected to degrade over time, mainly because of the degrading coating of the gratings. The HR grating has been recoated in 2011-06, the effect is visible in plots #1 and #2. Efficiency drops by about -0.0033 per year in H447.1A and in H651.5B. We felt unable to determine a reference value for the two red settings in plots #3 and #6, where the measurement method is particularly bad presumably due to insufficient sky subtraction in the data.