A CNES stratospheric balloon carrying the Claire
instrument was launched at 8.15 a.m. on Thursday 14 June 2001 from
the Gap Tallard aerodrome in the French Alps. After a
two-and-a-quarter-hour ascent, the 600,000-cubic-metre balloon reached
an altitude of over 41 kilometres, which it maintained for five and a
half hours. The flight ended and the gondola separated from the balloon
in the Bergerac area of southwest France at around 5.30 p.m. The
flight went according to plan with perfect gondola stabilization and
pointing, giving scientists three hours of observation in ideal
conditions. This was the second flight for this new type of telescope
that concentrates gamma rays using a special lens composed of 600
germanium crystals.

The prototype gamma-ray lens instrument observed a
reference source well known to astronomers, the Crab Nebula, to validate
the telescope’s design concept. The Crab Nebula and its central pulsar
observed today by the Claire gamma-ray telescope are the remnant of a
supernova explosion first recorded in 1054 by the Chinese. The pulsar is
around 15 kilometres in diameter and rotates and flashes like a
lighthouse 30 times a second.

The gamma-ray observation gondola was flown as part
of a cooperative project involving the Institut f¸r Kristallz¸chtung
in Berlin, the Argonne National Laboratories in Chicago, the University
of Birmingham, the Institut díestudis Espacials de Catalunya in
Barcelona, the Geneva Observatory, and CNES, who provided the gondola
pointing system and operated the balloon. The principal investigator for
the Claire project is Peter Von Ballmoos of the French space radiation
research centre CESR in Toulouse.

The project is part of a broader research effort to
develop new observation instruments for gamma astrophysics. After the
resounding success of Sigma and the development of Integral, Claire can
be seen as a third step offering enhanced sensitivity and unrivalled
energetic and angular resolution. From the outset, stratospheric
balloons have played a critical role in developing new gamma astronomy
instruments. Today, testing out prototypes in real astrophysical
observation conditions is a vital step in the design of any future
orbital telescope.

The future instrument using this technology could be
optimized to observe 511 kilo electron volt gamma photons resulting from
the annihilation of an electron and a positron (the antimatter
counterpart of an electron), a key phenomenon showing the presence of
antimatter in the universe. Gamma-lens telescopes will also allow us to
observe the radiation produced by a supernovaóthe spectacular
explosion marking the end of a star’s lifeóand will help us to gain a
closer insight into the origins of the chemical elements of which we are

Press contact: Eliane Moreaux 
phone +33 (0)6 08 87 45 41