GeMS, the Gemini Multi-Conjugate Adaptive Optics (MCAO) System, is the first multi-sodium based Laser Guide Star (LGS) Adaptive Optics (AO) system used for astronomy. It uses five LGSs distributed on a 1 arcmin constellation to measure and compensate for atmospheric distortions and delivers a uniform, close to diffraction-limited Near-Infrared (NIR) image over an extended FoV of 2arcmin. GeMS first light occurred in December 2011. The first compensated images demonstrate H-band Strehl Ratios (SR) in excess of 35% and Full-Width Half Maximum (FWHM) of or below 50 mas, in good seeing condition, averaged over a field of view of 85x85 arcsec.

In this paper we report on these early results, analyzing image quality in term of FWHM, SR, and field uniformity thereof. The PSF shape is analyzed, and the factor limiting performance are discussed. Finally, we present a first astrometric analysis, demonstrating astrometric errors as low as 420 microarcsecond for the first data acquired on-sky.