METIS, the Mid-infrared E-ELT Imager and Spectrometer is foreseen to be the third instrument on the European
Extremely Large Telescope (E-ELT) and the only instrument to provide high sensitivity mid-IR imaging and
spectroscopy to the E-ELT.
In order to reach the maximum resolution and sensitivity, an adaptive optics system is required. Since the operational
wavelength of METIS is the longest of all E-ELT instruments and the field is relatively small, the complexity of the AO
system is significantly reduced, both in required speed as well as order of the AO system.
Adaptive Optics has been demonstrated to deliver consistently high performance for the current generation of 6-10 meter
class telescopes at mid-infrared wavelengths, and similar performance is expected for METIS on the E-ELT. But in order
to provide a reliable system on the E-ELT, several effects which have a minor impact on 6-8 meter class telescopes will
need to be investigated for their impact on METIS AO. These effects include refractivity, atmospheric composition
variations, but also the operation in a complex operational environment given by both METIS as well as the E-ELT. In
this paper we describe the scientific requirements on the METIS AO system, the specific issues related to Adaptive
Optics in the mid-IR and expected performance of the METIS AO system on the E-ELT.