An array of → IACT telescopes for studying
cosmic → gamma rays in the 100 GeV to 100 TeV energy range.
The HESS observatory is located in Namibia, southern Africa, at an altitude of
1800 m, and the project is an international collaboration of more than 100 scientists
from nine countries. In its Phase I, HESS used four telescopes
each consisting of a light collector with a diameter of 13 m and a focal length of 15 m
placed at the corners of a square 120 m apart. Each telescope
is segmented into 380 round mirror facets of 60 cm diameter and uses
a camera consisting of 960 closely packed → photomultiplier
tubes. The first of the telescopes went into operation
in Summer 2002. Phase II includes a fifth
telescope, called Large Cherenkov Telescope (LCT), of 27 m diameter, located
in the centre of the initial array. This upgrade lowers the triggering
threshold of the HESS 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
(see, e.g., Bernlöhr et al. 2003, Astroparticle Physics 20, 111).
See also: H.E.S.S., short for High Energy Stereoscopic System, is also
intended to pay homage to Victor F. Hess (1883-1964), an Austrian-American physicist
who received the Nobel Prize in Physics in 1936 for his discovery of
→ cosmic rays.
