Status and performance of the Gemini Planet Imager adaptive optics system

TL;DR

This paper evaluates the performance of the Gemini Planet Imager's adaptive optics system over 1.5 years, demonstrating high-contrast imaging capabilities and identifying key factors limiting contrast, with suggestions for future improvements.

Contribution

It provides a comprehensive analysis of GPI AO system performance using real data, highlighting the main limitations and potential avenues for enhancement.

Findings

GPI achieves a 5σ raw contrast of 10^{-4} at 0.4" in 60 sec exposures.

Final contrasts are over 10 times better than raw contrasts after 1 hour.

Contrast is primarily limited by bandwidth wavefront error.

Abstract

The Gemini Planet Imager is a high-contrast near-infrared instrument specifically designed to image exoplanets and circumstellar disks over a narrow field of view. We use science data and AO telemetry taken during the first 1.5 yr of the GPI Exoplanet Survey to quantify the performance of the AO system. In a typical 60 sec H-band exposure, GPI achieves a 5$\sigma$ raw contrast of 10$^{-4}$ at 0.4"; typical final 5$\sigma$ contrasts for full 1 hr sequences are more than 10 times better than raw contrasts. We find that contrast is limited by bandwidth wavefront error over much of the PSF. Preliminary exploratory factor analysis can explain 60-70% of the variance in raw contrasts with combinations of seeing and wavefront error metrics. We also examine the effect of higher loop gains on contrast by comparing wavefront error maps reconstructed from AO telemetry to concurrent IFS images. These results point to several ways that GPI performance could be improved in software or hardware.