Orateur
Description
Significant progress has been made in the last decade in the
field of Ultra-High-Energy Cosmic Rays (UHECRs), thanks to the operation
of large ground-based detectors and to the renewed theoretical interest
that they triggered. While multi-messenger astronomy is rapidly developing
worldwide, the sources of the charged messengers, namely the cosmic rays,
are still to be determined, and the acceleration process to be understood.
Even at the highest energies, the particle deflections by intervening
magnetic fields appear to be too large to allow direct identification, at
least with the current statistics. Concentrating on the highest energies
has the advantage to reduce the number of sources, thanks to the so-called
GZK effect, and thus potentially reduce source confusion. However, the
very low flux of UHECRs in the GZK range requires huge detectors to be
deployed. Alternatively, a single instrument could be used to
significantly increase the current statistics if it could be operated from
space, looking down to the nadir to detect the fluorescence light of
UHECR-induced air showers over a huge volume of atmosphere. In addition,
such a space mission would cover the whole celestial sphere and allow to
draw the first complete map of UHECRs with essentially uniform coverage
and systematics. Such a program has been undertaken by the JEM-EUSO
Collaboration. In this talk, I will review the major steps taken along
this road to space, including ground-based experiments and
balloon flights. I will also present the future planned missions, on a
super-pressure balloon as well as in/on the ISS. Finally, I will discuss
the current efforts to extend the science case of such a mission to
high-energy neutrino astronomy, complementing the ground-based neutrino
detectors, and address the interesting issue of high-altitude UHECR
shower, which only a space mission could observe.
