METIS, the Mid-IR instrument for the ELT will be operating an internal Single Conjugate Adaptive Optics System (SCAO), which will be the work horse AO system and mainly serve the science cases targeting exoplanets and disks around bright stars. In order to extend the sky coverage and brightness range of targets requiring AO correction to fainter stars, a Single Laser Adaptive Optics (SLAO) system is proposed. Although SLAO systems are currently in operation on 8-10 meter class (and smaller) telescopes, extending SLAO systems to the ELT increases the challenges associated with the cone effect and the spot elongation significantly. But since METIS will be operated at L-band, the requirements on required AO correction are fortunately reduced (with respect to other ELT instruments), making a SLAO system an attractive low-cost option for METIS. The METIS SLAO system will operate using an on-axis Laser Guide Star (LGS) and re-use the internal SCAO WFS for field stabilization and low-order correction (truth sensing), further reducing cost and complexity. In this paper we will present the current state of the design of the METIS SLAO system, and will address the challenges, like the impact of the cone effect, spot elongation and design constraints on the system. We will show that this system will likely provide a >60% SR in L-band over >50% of the sky, providing an attractive addition to the METIS SCAO system.

METIS is one the first three instruments on the E-ELT. Apart from diffraction limited imaging, METIS will provide coronagraphy and medium resolution slit spectroscopy over the 3 - 19μm range, as well as high resolution (R ∼ 100,000) integral field spectroscopy from 2.9 - 5.3μm, including a mode with extended instantaneous wavelength coverage. The unique combination of these observing capabilities, makes METIS the ideal instrument for the study of circumstellar disks and exoplanets, among many other science areas. In this paper we provide an update of the relevant science drivers, the METIS observing modes, the status of the simulator and the data analysis. We discuss the preliminary design of the optical system, which is driven by the need to calibrate observations at thermal IR wavelengths on a six-mirror ELT. We present the expected adaptive optics performance and the measures taken to enable high contrast imaging. We describe the opto-mechanical system, the location of METIS on the Nasmyth instrument platform, and conclude with an update on critical subsystem components, such as the immersed grating and the focal plane detectors. In summary, the work on METIS has taken off well and is on track for first light in 2025.