An adaptive 2 M class telescope for a microlensing search from antarctica

We describe the scientific rationale and the preliminary optomechanical design for a 2 m class telescope designed to achieve ground layer correction over a ≈15arcmin Field of View (FoV) to be located at the Dome-C site. The proposed science case is the detection of microlensing events in and by globular clusters and nearby galaxies that, for a high probability of success, requires exceptional seeing (≈0.2 arcsec or better) and a large target density (the centre of a globular cluster with a corresponding telescope FoV of ≈15 arcmin). This approach can capitalise on some of the unique qualities already observed above the Dome-C site, namely that the atmospheric turbulence is largely limited to a ground layer of small thickness only, a relatively low Greenwood frequency and uniterrupted sky coverage during the winter months for objects such as the globular cluster 47-Tue. Further to the central science case of microlensing the telescope could provide a technological testbed for future telescopes and, given the unique atmospheric properties witnessed already during previous site testing compaigns, has the chance to provide a large amount of data (based on accurate and continuous light curves lasting several months) for fields of research outside that of microlensing. Details of the specific concepts of adaptive optics to be adopted for this telescope are outlined.