AMBER on the VLTI: data processing and calibration issues

TL;DR

This paper evaluates the current performance of the AMBER instrument on VLTI, highlighting its strengths in certain modes and the limitations caused by vibrations, data reduction issues, and electromagnetic interference, with suggestions for improvements.

Contribution

It provides a comprehensive assessment of AMBER/VLTI performance, identifying key limitations and proposing potential solutions for calibration and data processing challenges.

Findings

High spectral resolution modes achieve specified precision for bright objects.

Vibrations limit the accuracy of absolute observables.

Electromagnetic interference affects measurements for faint objects.

Abstract

We present here the current performances of the AMBER / VLTI instrument for standard use and compare these with the offered modes of the instrument. We show that the instrument is able to reach its specified precision only for medium and high spectral resolution modes, differential observables and bright objects. For absolute observables, the current achievable accuracy is strongly limited by the vibrations of the Unit Telescopes, and also by the observing procedure which does not take into account the night-long transfer function monitoring. For low-resolution mode, the current limitation is more in the data reduction side, since several effects negligible at medium spectral resolution are not taken into account in the current pipeline. Finally, for faint objects (SNR around 1 per spectral channel), electromagnetic interferences in the VLTI interferometric laboratory with the detector electronics prevents currently to get unbiased measurements. Ideas are under study to correct in the data processing side this effect, but a hardware fix should be investigated seriously since it limits seriously the effective limiting magnitude of the instrument.