Techniques for the manufacturing of stiff and lightweight optical mirror panels based on slumping of glass sheets: concepts and results R. Canestrari* a,b , M. Ghigo a , G. Pareschi a , S. Basso a , G. Motta a,c , M. Doro d , E. Giro e , L. Lessio e a INAF-Osservatorio Astronomico di Brera - Via Bianchi, 46 23807 Merate (Lc) Italy b Università degli Studi dell’Insubria - Via Valleggio, 11 22100 Como (Co) Italy c Università degli Studi di Milano-Bicocca – Piazzale dell’Ateneo Nuovo, 1 20126 Milano Italy d INFN-Padova - Via Marzolo 8 35131 Padova e INAF-Osservatorio Astronomico di Padova - Vicolo Osservatorio 5 35122 Padova Italy ABSTRACT In the last decade Very High Energy (VHE) gamma-ray astronomy has improved rapidly opening a new window for ground-based astronomy with surprising implications in the theoretical models. Nowadays, it is possible to make imaging, photometry and spectroscopy of sources with good sensitivity and angular resolution using new facilities as MAGIC, HESS and VERITAS. The latest results of astronomy in the TeV band obtained using such facilities demonstrate the essential role of this window for high energy astrophysics. For this reason new projects (e.g. CTA and AGIS) have been started with the aim to increase the sensitivity and expand the energy band coverage. For such telescopes arrays probably tens of thousands of optical mirror panels must be manufactured with an adequate industrial process, then tested and mounted into the telescopes. Because of the high number of mirrors it is mandatory to perform feasibility studies to test various techniques to meet the technical and cost-effectiveness requirements for the next generation TeV telescopes as CTA and AGIS. In this context at the Astronomical Observatory of Brera (INAF-OAB) we have started the investigation of different techniques for the manufacturing of stiff and lightweight optical glass mirror panels. These panels show a sandwich-like structure with two thin glass skins on both sides, the reflective one being optically shaped using an ad-hoc slumping procedure. The technologies here presented can be addressed both for primary or secondary mirrors for the next generation of Cherenkov telescopes. In this paper we present and discuss the different techniques we are investigating with some preliminary results obtained from test panels realized. Keywords: Segmented Optics, Glass Slumping, lightweight optics, Cherenkov telescopes, CTA, AGIS 1. INTRODUCTION The astronomy in the TeV band has achieved exceptional results since the discovery of TeV emission from the Crab Nebula by Whipple in 1989 to the most recent sources (about 100) detected thanks to the high sensitivity of the present days Cherenkov telescopes. Both galactic and extragalactic sources has been detected using very large mirror areas such for the two MAGIC telescopes in La Palma (Canary Islands) and the high performance of the telescope arrays such as H.E.S.S. in Namibia or VERITAS in Arizona (USA). The international communities working in the TeV astronomy both in Europe and USA are now involved in the study of huge arrays of Cherenkov telescopes such as the Cherenkov Telescope Array (CTA) [1] and the Advanced Gamma-ray Imaging System (AGIS) [2]. The ambitious goal is to reach sensitivity above one order of magnitude greater than the current instruments in the very wide energy range from 10 GeV to more than 100 TeV. These new, complex and very large facilities need, among other things, a substantial technological development of many telescope subsystems. From the installation, operational and maintenance procedures of each single telescope to the efficient coordination of the complete array in a structure organized as an observatory, from the data handling and archiving to the huge power supply need and management. Optics for EUV, X-Ray, and Gamma-Ray Astronomy IV, edited by Stephen L. O'Dell, Giovanni Pareschi, Proc. of SPIE Vol. 7437, 743711 · © 2009 SPIE CCC code: 0277-786X/09/$18 · doi: 10.1117/12.826145 Proc. of SPIE Vol. 7437 743711-1