HESS II HEGRA HESS I Personal view Stimulate

HESS II HEGRA HESS I Personal view Stimulate a discussion 10 m 2 108 m 2 2 600 m

HEGRA

HEGRA Air shower experiment > 6 different detector types (particles and gammas) Partly combined Very good for evaluation of different techniques Imaging air Cherenkov telescopes seemed finally to be the most promising detectors From first telescope (6 m 2, 19 pixel) Stereoscopic system with 5 identical telescopes (10 m 2, 271 pixel)

HESS HEGRA

HESS I Dedicated experiment on γ-ray-astronomy in the energy range of Te. V Stereoscopy with 4 identical telescopes Wide field of view Southern hemisphere

HEGRA => HESS I Dedicated site under our control (including all the infrastructure) Large site => flexibility No interference with other experiments in the region Political problems successfully solved for Namibia Local crew Constant maintenance and fast repair Well prepared campaigns Clear and precise specifications Good balance in performance of telescope components Optimum on performance for money Precise specifications save a lot of money Better monitoring of internal conditions (bending, pointing…) and external conditions (weather…)

Available and reliable technology = focus on physics Minimize need for human intervention Simple maintenance, little adjustment work Professional help on engineering eers n i g n l do e r design? l e w hei How t d n a st under 1. Concrete foundation 2. Steel work (cut and welds) 3. Mechanical engineering (bearings, drives, safety) Experience in industry with antennas up to ~60 m Ø dishes with better precision than is needed for Cherenkov telescopes Why reinvent the wheel, even if it might be fun A stiff and robust dish

Our approach to HESS I (and now HESS II) Industry Responsibility on the realisation stays with the collaboration Design studies (realization of our wishes, feasibility, cost estimate, steps in size which costs) Engineers prepare tender on a structure (mount + concentrator) b mechanical engineering Collaboration Engineers help in the approval of technical components and their assembly Tracking Design of mirrors and adjustment mechanics + quality control + installation + adjustment

HESS II HESS I

HESS I => HESS II No principle change in the approach The current design was chosen from two studies Different company for engineering Tracking and safety concept by industry (only an adaptation of a standard industry product) Improvements in some details Drive system (biased, tooth wheels in elevation) Mirror adjustment (closer to dish)

HESS I Schlaich Bergermann & Partner Solar dish technology Improve by x 10 HESS II MT-Aerospace (former MAN technology) Radio telescopes technology Relax by x 10 DRIVES! (biased, gear box)

Structure (mount, concentrator) Steel (Precisely defined Well controlled by engineers Fabrication with local companies) Mechanical engineering Bearings Standard items Drives HESS I has friction drive HESS II has tooth wheels Mirrors Aluminium as reflecting material Aging? ? (~3%/a, dependent on the manufacturer) Coating? ? thickness of aluminium, quartz? Cleaning? ? quartz coating is fragile Mirror adjustments Stiff dish, adjust rarely

Conclusions Dedicated large site Local crew Engineering for engineers Rely on available technology Be ready for new technology Do physics

Assembly of first telescope

Assembly of first telescope

Die H. E. S. S. Teleskope (2003)