Ray Detector Delivered to Space Station

In addition to ferrying tons of food, water and supplies to the International Space Station,

 a Japanese cargo ship that arrived on Monday (Aug. 23) carried an astrophysics telescope that will join the flagship Alpha Magnetic Spectrometer in hunting for cosmic rays.

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The Calorimetric Electron Telescope, or CALET, was due to be mounted on a platform outside Japan's Kibo laboratory on Tuesday (Aug. 24), joining the$2 billion AMS particle detector, which was attached to the station in 2011.

Once operational, CALET will precisely measure cosmic rays, at even higher energies than AMS.

"Cosmic rays come at you from all directions and all the time … Every time one of these high-energy cosmic rays comes at us and starts triggering the instrument, we record it," astrophysicist John Wefel, with Louisiana State University, said in a NASA TV interview.

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Ground-based instruments can indirectly detect cosmic rays by measuring secondary particles that are created when the rays strike the atmosphere. By studying the cosmic rays directly in space, scientists hope to develop a better understanding of where they come from, what they are made of and how they come to have so much energy.

The cosmic rays also may shed light on so-called "dark matter," which unlike regular matter does not emit detectable electromagnetic radiation. Dark matter, which comprises about 27 percent of the universe, can be indirectly detected by studying how its gravity influences nearby objects.

Regular matter adds up to less than 5 percent of the universe. The rest of the universe, roughly 68 percent, is filled with a mysterious anti-gravity force known as dark energy.

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While AMS can detect electrons, protons, nuclei and antimatter at a range of energy levels, CALET is focused on high-energy electrons.

"CALET addresses many outstanding high-energy astrophysics questions such as the origin of cosmic rays, how cosmic ray accelerate and travel across the galaxy; and the existence of dark matter and nearby cosmic-ray sources," NASA said in a summary of the program.

The telescope, which will be mounted outside the station, is expected to operate for up to five years. A third astrophysics observatory, known as Cosmic Ray Energetics and Mass for the International Space Station, or ISS-CREAM, is due to launch next year.