H.e.s.s. Observatory Celebrates 20 Year Anniversary

21 Oct 2022

Namibia, with its clear skies, is a popular spot for stargazers, amateur astronomers and scientists. The country hosts the largest array of telescopes, to explore cosmic gamma rays, worldwide since 2002. The scientific fraternity celebrated the array’s twentieth anniversary on 18 October 2022.

The High Energy Stereoscopic System (H.E.S.S.) observatory is operated by a collaboration of more than 240 scientists from 36 scientific institutions in 12 different countries, including Namibia.


CT5 observing the night sky with the new camera of the large, 28m diameter telescope fitted 2 years ago.
Image Credit: Christian Föhr (MPIK)


“We are looking back on 20 outstanding years of exceptional physics,” said Prof. Gérard Fontaine, Representative of the French National Centre for Scientific Research (CNRS), who had travelled to Namibia for the celebration. “The international collaboration is of great significance.”

Namibia is proud that the country is the location for the H.E.S.S. telescopes and that it is part of the research projects. “We are very proud that the University of Namibia (Unam) is an integral part of it,” said Namibia’s Minister of International Relations, Netumbo Nandi-Ndaitwah in a speech read on her behalf.

The telescope array has definitely put Namibia on the international map among physicists and other scientists over the past twenty years.

To date, the H.E.S.S. collaboration has published over 250 articles in internationally renowned scientific journals; the collaboration and its members have been awarded many prestigious prizes.

It is operated by research institutions and most of the participating scientists are young post-graduate researchers studying for a PhD as well as those who have already obtained it. By 2022, some 1,000 thesis projects contributed significantly to the successful education and professional training in all the participating institutions, including the University of Namibia.

Opening a window to the universe

In 2002, the first of now five telescopes of the High Energy Stereoscopic System (H.E.S.S.) was inaugurated in the Khomas Hochland mountains some 120km west of Windhoek on Farm Göllschau. The dark matter and so-called black holes are also part of the research programme of the world's largest reflector telescope system for gamma rays.

Twenty years ago, the Max Planck Society in Germany and the Federal Ministry of Research jointly spent six million Euros on the project, contributing more than 75 percent of the total cost of 7.6 million Euros.

The abbreviation H.E.S.S. stands for "High Energy Stereoscopic System" and the acronym simultaneously honors the Austrian discoverer of gamma rays, Victor Franz Hess (1883-1964).

Shortly after the first mirror telescope was erected in 2002, three identical telescopes followed. They are 12m wide and form the four corners of a square and can be rotated. The H.E.S.S. array opened a new “window to the universe”.

For the first time, true images of cosmic sources were obtained of gamma rays with the highest energies that had ever been recorded from astronomical objects. In the past twenty years, exciting observations were made in outer space.

The array of five H.E.S.S. telescopes on a farm some 120km west of Windhoek.
Photo: HESS observatory


The mirrors of the telescopes are each composed of 382 round mirror facets of 60 cm diameter. The total amount of 1 528 mirrors of the four telescopes together cover an area of 432 square metres.

Gamma rays are 'made visible' by blue light to the cameras of the telescopes - with the help of the Cherenkov flashes. These bluish flashes have been named after their discoverer, the Russian scientist Pavel Alexeyevich Cherenkov (1904-1990).

In 2012 for the tenth anniversary of the H.E.S.S. observatory in Namibia, a fifth telescope was added. The fifth H.E.S.S telescope is currently the world's largest reflecting telescope. It is situated in the middle of the square, is almost 40 m high and towers over the four other telescopes. It has a diameter of 28m. Its mirror has 875 hexagonal mirror facets of 90 cm in diameter. The total mirror surface is 614 m². The colossal total weight is 600 tons.

All five telescopes have been constructed in Namibia by Namibian companies – a proud achievement indeed.

The H.E.S.S. observatory will run until the second half of 2024 and then a decision on the way forward will be taken.

Brigitte Weidlich

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