The MICADO first light imager for ELT: its astrometric performance

TL;DR

This paper discusses the efforts to achieve high-precision astrometric measurements with the MICADO NIR imager on the ELT, emphasizing the challenges and requirements for calibration and system performance.

Contribution

It presents an analysis of the expected astrometric performance of MICADO, highlighting the necessary calibration efforts for optimal accuracy across its field of view.

Findings

Centroiding error can reach a few 10 microarcseconds with the ELT's capabilities.

Achieving uniform astrometric performance across the full field requires significant calibration.

Systematic calibration is crucial for realizing the instrument's potential in high-precision astrometry.

Abstract

We report on our ongoing efforts to ensure that the MICADO NIR imager reaches differential absolute (often abbreviated: relative) astrometric performance limited by the SNR of typical observations. The exceptional 39m diameter collecting area in combination with a powerful multi-conjugate adaptive optics system (called MAORY) brings the nominal centroiding error, which scales as FWHM/SNR, down to a few 10 uas. Here we show that an exceptional effort is needed to provide a system which delivers adequate and calibrateable astrometric performance over the full field of view (up to 53 arcsec diameter).