- Last Updated: 17 October 2016
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Building on the success of the Cosmic Ray Energetics And Mass (CREAM) balloon flights, the instrument has been transformed for accommodation on the International Space Station (ISS), specifically, NASA’s share of the Japanese Experiment Module Exposed Facility (JEM-EF). The CREAM on the ISS, ISS-CREAM, mission completed its system level qualification tests at NASA Goddard Space Flight Center in August 2015. The payload was delivered to NASA Kennedy Space Center for launch on SpaceX-12, which is currently scheduled to launch in April 2017. The goal is to extend the energy reach of direct measurements of cosmic rays to the highest energy possible to probe their origin, acceleration and propagation. Its long exposure above the atmosphere offers orders of magnitude greater statistics without the secondary particle background inherent in balloon experiments investigating the origin of cosmic rays. The ISS-CREAM instrument consists of complementary and redundant particle detectors to measure elemental spectra of Z = 1–26 nuclei over the energy range 1012 to >1015 eV. An ionization calorimeter determines the energy of cosmic ray particles, provides tracking, and the event trigger. The four-layer Silicon charge detectors provide precise charge measurements. Top/bottom counting detectors provide shower profiles for electron/hadron separation. The boronated scintillator detector provides additional electron/hadron discrimination using thermal neutrons produced by particles that interact within the calorimeter. ISS-CREAM will (1) determine how the observed spectral differences of protons and heavier nuclei evolve at higher energies approaching the knee; (2) be capable of measuring potential changes in the spectra of secondary nuclei resulting from interactions of primary cosmic rays with the interstellar medium; (3) conduct a sensitive search for spectral features, such as a bend in proton and helium spectra; and (4) measure electrons with sufficient accuracy and statistics to determine whether or not a nearby cosmic-ray source exists. It will also contribute indirectly to the dark matter search by measuring electrons in addition to nuclei at energies beyond where current direct measurements exist.