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EUSO - The Extreme Universe Space Observatory
The Earth is being continuously bombarded by high-energy particles known as cosmic rays. While moderate energy cosmic rays almost certainly originate from comparatively well understood objects in our own Galaxy, such as the expanding shocks of exploded stars, understanding the origin of the highest energy cosmic rays is one of the great challenges in astrophysics. Although these extreme energy cosmic rays (EECR) are very rare (only around 1 per square kilometre per century!) they are the most energetic particles known in the Universe. Because they are so rare, only a few dozen such events have been detected using different ground based air shower detectors in the past 30 years. There has been no convincing identification of any of these events with a likely astronomical source.
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EUSO is the cylindrical structure attached to the left side of ESA's Columbus External Payload Facility. The docking port for the Space Shuttle and the Japanese module can be seen to the right of the Columbus module. |
EUSO is an ambituous proposal, under study by ESA's Human Spaceflight and Science Directorates, to investigate EECR from space by using the Earth's atmosphere as a giant cosmic ray detector. The Principal Investigator is Prof. L. Scarsi from IASF, Palermo. EUSO will observe the flash of fluorescence light and the reflected Cerenkov light produced when an EECR interacts with the Earth's atmosphere. Imaging of the light track will allow the sky position and energy of the event to be reconstructed. By looking down from the International Space Station with a 60 degree field of view, EUSO will detect around 1000 events per year allowing a sensitive search for the objects producing EECR.
The phase A study was formally completed and EUSO was declared
technically ready to proceed to phase B at the Phase A review board
meeting of 15 July 2004. The Astronomy Working Group (AWG) and the
Fundamental Physics Advisory Group (FPAG) reviewed the scientific case
of EUSO at a joint session in May 2004. They concluded that the project
was not at the top of their priorities and were unable to recommend its
continuation into phase B. This conclusion was later endorsed by the
Space Science Advisory Committee (SSAC) at its meeting of May 26, 2004. |
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