Quality Assessment of the Fabry-Pérot Wavelength Calibration for CRIRES+ : Student Project Report

Sammanfattning: The data reduction software of CRIRES+, a new high-resolution spectrometer installed at VLT, features a calibration routine that uses data from a Fabry-Pérot étalon. The quality of this calibration mode is assessed in this project report. Two investigations are carried out: From a diagnostics data set, the physical spacing between the three detector chips is reconstructed, as well as the étalon gap size as a function of Fabry-Pérot order. Both provide a measure of internal coherence of the calibration solution. The reconstructed detector spacing values are irreconcilable with the actual measured values, hinting at a fault in the calibration routine. The reconstructed gap curve shows unphysical discontinuities. Further investigation shows that each detector chip’s calibration solution seems to be consistent across it, while the three chips’ solutions are inconsistent with each other at several hundred meters per second. Due to ESO’s top-level requirements, this does not pose a technical fault. Yet, it still indicates significant room for improvement of the calibration routine.