H.E.S.S.

	The High Energy Stereoscopic System (H.E.S.S.) is an array of Imaging Atmospheric Čerenkov Telescopes (IACTs) that is used to do high energy gamma-ray Astronomy. With high energy we mean photon energies in the range from 100 GeV to 100 TeV. The name of the H.E.S.S. Experiment refers to these high energies as well as the stereoscopic technique that it employs. In addition, the name is intended to honour the Austrian-American Physicist Victor F. Hess who discovered the exitence of Cosmic Rays during the years 1911—13. A discovery for which he received the Nobel prize in 1936.

H.E.S.S. Phase I

Phase I of the H.E.S.S. project consists of four identical telescopes placed at the corners of a square 120 m apart. Each of these units consist of a light collector with a diameter of 13 m and a focal length of 15 m. Each light collector is a spherical geometry tessellated mirror consisting of 380 60 cm diameter circular mirrors giving a total reflective area of 107 m². At the focus of each telescope is a ‘camera’ consisting of 960 photomutiplier tubes (PMTs) connected to very fast electronics that captures ‘images’ of gamma-ray induced air showers in the upper atmosphere. The square array of telescopes allows the observation of these gamma-ray induced air showers from different locations to obtain information in three dimensions about individual air shower events. This in turn allows the calculation of several things including the energy of the initiation gamma-ray photon as well as the direction whence it came. In a nutshell, continuous observation over time of these air showers, allows the gradual build-up of information of gamma-ray sources in interstellar and intergalactic space. In this way the H.E.S.S. telescope array can be used to do gamma-ray Astronomy between the photon energies of 100 GeV up to 100 TeV, hence the reference to “High Energy”. For more information you can visit the official About H.E.S.S. Telesopes information page that details the telescopes as well as the Atmospheric Čerenkov technique. The telescopes’ space-frames were manufactured by NEC Stahl in Okahandja and the electronics, drives and mirrors were designed and manufactured in Europe.

The H.E.S.S. Project is run by the H.E.S.S. Collaboration that consists of over 150 researchers (academics, post-doctorals, and graduate students) spread over 28 institutions spread over 10 countries. Among these are the Max-Planck Institute for Nuclear Physics, several German and French universities, the Northwest University on South Africa and the University of Namibia. For a full list of institutions an researchers, see the official HESS Collaboration institutions page. For the organizational structure of the HESS Collaboration, see the official H.E.S.S. organization page.

Thus far, the H.E.S.S. Phase I project has been phenomenally successful, with the Collaboration discovering many new gamma-ray sources in space (see the official H.E.S.S. Source Catalogue) and publishing hundreds of papers (see the official H.E.S.S. Publication List).

If you are interested in the type of Astrophysics that is done within the HESS Collaboration, see the official Astrophysics with H.E.S.S. page.

H.E.S.S. Phase II

Following the success of H.E.S.S. Phase I, the HESS Collaboration embarked upon an extension of the capabilities of the H.E.S.S. Telescope Array with the addition of the Large Čerenkov Telescope (LCT), a fifth 27 m diameter IACT in the centre of the present array. This telescope will have a parabolic tesselated mirror consisting of 1006 90 cm diamater hexagonal mirrors to produce a light collecting area of 600 m². The new 'camera' have an 'eye' of 2048 PMT 'pixels'. This upgrade will lower the triggering threshold of the H.E.S.S. array to about 20 GeV, thus broadening the energy window in which gamma-ray astronomy can be done, opening up more opportunities in Astrophysical research. The space-frame of this telescope was manufactured at Kraatz Marine in Walfish Bay Namibia with the electronics being designed and manufactured in Europe. At the time of this writing (June 2009) the telescope space-frame is being assembled on site. Much of the details of this telescope is confidential at this stage. Here’s a photo montage of what the Phase II telescope should look like after it is completed:

Location

The H.E.S.S. telescopes are located in the Khomas Highland on the Farm Göllschau, about 100 km south-west of Windhoek. The exact location is 23o16'18'' S, 16o30'00'' E at 1800 m above sea level.

Facilities on site include a control building, a residence building, power generators, and a microwave link to transmit data to Windhoek.

Access to the site is restricted and tours are by arrangement only. More information on to how visit the H.E.S.S. site can be found in the official contact section.

The UNAM HESS Group consists of

• Dr Riaan Steenkamp (Group Leader)
• Mr Isak D. Davids, Department of Physics, Lecturer and PhD student in Astrophysics
• Mr Eben Tjingaete, H.E.S.S. Technician
• Mr Maveipi Kandjii, H.E.S.S. Technician