Imagine the Universe!

What Else Makes Observing Cosmic Rays Hard?

About 90% of the cosmic ray nuclei are hydrogen (protons), about 9% are helium (alpha particles), and all of the rest of the elements make up only 1%. Even in this one percent there are very rare elements and isotopes. These require large detectors to collect enough particles to say something meaningful about the "fingerprint" of their source. The HEAO 3 Heavy Nuclei Experiment, launched in 1979, collected only about 100 cosmic rays with charges between 75 and 87 in almost a year and a half of flight, and it was much bigger than most scientific instruments flown by NASA currently. To make better measurements requires an even larger instrument, and the bigger the instrument, the greater the cost.

Imagine the Universe is a service of the High Energy Astrophysics Science Archive Research Center (HEASARC), Dr. Alan Smale (Director), within the Astrophysics Science Division (ASD) at NASA's Goddard Space Flight Center.

The Imagine Team
Acting Project Leader: Dr. Barbara Mattson
All material on this site has been created and updated between 1997-2012.

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