HEGRAHESS I

HESS II

10m2

108m2

600m2

Personal view

Stimulate a discussion

HEGRA

HEGRAAir shower experiment

> 6 different detector types (particles and gammas)

Imaging air Cherenkov telescopes seemed finally to be the most promising detectors

Partly combined

Very good for evaluation of different techniques

From first telescope (6m2, 19pixel)

Stereoscopic system with 5 identical telescopes (10m2, 271pixel)

HEGRA

HESS

HESS I Dedicated experiment on γ-ray-astronomy in the energy range of TeV

Wide field of view

Southern hemisphere

Stereoscopy with 4 identical telescopes

HEGRA => HESS I

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

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

Better monitoring of internal conditions (bending, pointing…) and external conditions (weather…)

Professional help on engineering

Experience in industry with antennas up to ~60m Ø dishes with better precision than is needed for Cherenkov telescopes

Why reinvent the wheel, even if it might be fun

Available and reliable technology = focus on physics

1. Concrete foundation

2. Steel work (cut and welds)

3. Mechanical engineering (bearings, drives, safety)

Minimize need for human intervention

A stiff and robust dish

Simple maintenance, little adjustment work

How well do engineers

understand their design?

Our approach to HESS I (and now HESS II)

Design studies (realization of our wishes, feasibility, cost estimate, steps in size which costs)

Engineers prepare tender ona structure (mount + concentrator)b mechanical engineering

Engineers help in the approval of technical components and their assembly

Tracking

Design of mirrors and adjustment mechanics+ quality control+ installation+ adjustment

Col

labo

rati

on

Indu

str

yResponsibility on the realisation stays with the collaboration

HESS I

HESS II

HESS I => HESS II

Improvements in some details

Different company for engineering

Tracking and safety concept by industry (only an adaptation of a standard industry product)

No principle change in the approach

Drive system (biased, tooth wheels in elevation)

Mirror adjustment (closer to dish)

The current design was chosen from two studies

HESS I

Schlaich Bergermann & Partner

Solar dish technology

Improve by x10

HESS II

MT-Aerospace (former MAN technology)

Radio telescopes technology

Relax by x10

DRIVES!(biased,gear box)

Structure (mount, concentrator)

Mechanical engineering

Mirrors

Mirror adjustments

Steel

Bearings

Drives

Stiff dish, adjust rarely

Aluminium as reflecting material

Coating?? thickness of aluminium, quartz?

Cleaning?? quartz coating is fragile

Aging?? (~3%/a, dependent on the manufacturer)

HESS I has friction driveHESS II has tooth wheels

Standard items

(Precisely definedWell controlled by engineersFabrication with local companies)

ConclusionsDedicated 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)