Cosmic Ray Energetics and Mass (CREAM) - 07.01.15
The Cosmic-Ray Energetics and Mass investigation, known as CREAM, places a highly successful balloon-borne instrument aboard the International Space Station where it gathers an order of magnitude (ten times) more data, which has lower background interference because Earth's atmosphere is no longer interfering. CREAM's instruments measure the charges of cosmic rays ranging from hydrogen up through iron nuclei, over a broad energy range. The modified balloon instrument is carried aloft on a Space X Dragon Lab cargo supply mission and placed on the Japanese Exposed Module for a period of at least three years. Science Results for Everyone
Information Pending Experiment Details
Eun-Suk Seo, Ph.D., University of Maryland, College Park, MD, United States
Sungkyukwan University, Dept. of Physics, Suwon
Universidad Nacional Autonoma de Mexico, Instituto de Fisica, Mexico City, Mexico
NASA Wallops Flight Facility, Wallops Island, VA, United States
Kyungpook National University, Daegu, South Korea
University of Maryland, Institute for Physical Science and Technology (IPST), College Park, MD, United States
Northern Kentucky University, Dept. of Physics and Geology, Highland Heights, KY, United States
NASA Goddard Space Flight Center, Greenbelt, MD, United States
Penn State University, Dept. of Physics, University Park, PA, United States
Laboratorire de Physique Subatomique et de Cosmologie, Grenoble, France
Sponsoring Space Agency
National Aeronautics and Space Administration (NASA)
Science Mission Directorate (SMD)
ISS Expedition Duration
Previous ISS Missions
The CREAM instrument has had 6 successful balloon flights over Antarctica during the local summer time from 2004 to 2010. For each flight, a gigantic 40 million cubic ft balloon carried the payload to the float altitude of ~130,000 ft (~40 km). After each flight the instrument was recovered and refurbished for subsequent flights. CREAM accumulated ~161 days of exposure, which is the longest known exposure for a single balloon-borne experiment.
- Cosmic rays reach Earth from far outside the solar system with enormous energies well beyond what man-made accelerators can achieve. Space-based direct measurements of high-energy cosmic rays are difficult because of low particle fluxes in the most interesting regions, and there are no data sets with elemental charge resolution and adequate statistics.
- CREAM has accumulated ~161 days of data during six successful balloon flights over Antarctica. This longest known exposure for a single balloon-borne experiment verified the instrument design and reliability. The key value in residing on the ISS is the long exposure above the atmosphere and orders of magnitude greater statistics without the secondary particle background inherent in balloon experiments.
- One of the key discoveries CREAM made with balloon flights is spectral hardening, which contradicts the traditional view that a simple power law can represent cosmic rays without deviations below the "knee", around 3x1015electron volts (eV), where the cosmic ray spectrum steepens. The current CREAM result provides important constraints on cosmic ray acceleration and propagation models, and it must be accounted for in explanations of the electron anomaly, which generated a lot of excitement in the science community, as well as the media, due to its possible dark matter explanation. CREAM on the ISS may greatly reduce the statistical uncertainties, and extend balloon-borne CREAM measurements, to energies beyond any reach possible with balloon flights, providing keys to understanding the origin, acceleration and propagation of cosmic rays.
The CREAM mission utilizes the proven science instrument designs of the balloon-borne CREAM project to develop an instrument to fly on the U.S. Share of the ISS Japanese Experiment Module Exposed Facility (JEM-EF) for a 3-year operation. 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. CREAM addresses, specifically, the science objectives of the Advanced Cosmic-ray Composition Experiment for the Space Station (ACCESS) prioritized in the Small Space-Based Initiative category of the 2001 Decadal Study Report "Astronomy and Astrophysics in the New Millennium".
Precise CREAM measurements of energy spectra of individual nuclei over the proton-to-iron elemental range, from 1012 eV to >1015 eV, addresses the long-standing fundamental science questions:
- Do supernovae really supply the bulk of cosmic rays?
- What is the history of cosmic rays in the Galaxy?
- Can the energy spectra of cosmic rays result from a single mechanism?
- What is the origin of the steepening (“knee”) around 3x1015 eV in the cosmic ray all-particle energy spectrum?
These questions have been difficult to answer because no space mission capable of measuring the low fluxes of particle at energies approaching the cosmic ray “knee” has yet been flown. The CREAM mission is the first experiment to have the statistics needed to pursue them effectively.
The CREAM instrument consists of complementary and redundant particle detectors. An ionization calorimeter determines the energy of the cosmic ray particles, provide tracking, and event trigger. 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.
The CREAM Insturment:
- Determines how the observed spectral differences of protons and heavier nuclei evolve at higher energies approaching the “knee”;
- Is capable of measuring potential changes in the spectra of secondary nuclei resulting from the interactions of primary cosmic rays with the interstellar medium;
- Conducts a sensitive search for spectral features, such as a bend in the proton spectrum.
A century-old mystery in astrophysics is the origin of cosmic rays, which are naked atomic nuclei accelerated in deep space that can damage electronics and humans alike. CREAM, which has been highly successful in several long-duration balloon flights, observes features in the energy spectra and populations of cosmic rays and helps establish limits on their acceleration by supernovae.
The origins of cosmic rays and the mechanisms that accelerate them to high speeds are among the oldest questions in modern astrophysics. Results from CREAM bring the science community closer to answering those questions, and build a stronger understanding of the fundamental structure of the universe.
The CREAM instrument requires zenith viewing for optimal science results. The payload interface to JEM EF via the PIU and utilizes the standard ISS resources via JEM EF. There are no scientific samples that require preservation. The product of this payload is digital data. CREAM does not have a gimbal system and does not require off-nominal ISS attitudes. The payload should be notified if the ISS attitude is changed from the nominal XVV attitude. There is no crew display associated with this payload. The payload will be operated continuously after initial check-out and on-orbit commissioning. The CREAM Investigation team continuously monitors payload health, status, and science telemetry. Crew training is not required for CREAM since there is no crew involvement for on-orbit operations. The nominal CREAM data rate is ~350 kbps. There are no safety critical on-orbit operations associated with this payload. There is no deployed payload equipment. There is no rotating equipment.
The CREAM nominal flight operations are conducted after the payload is installed on JEM-EF. The flight operations are conducted and supported by three ground-based organizations (1) CREAM Project Science Operations Center (SOC) at the University of Maryland, (2) The Payload Operations and Integration Center (POIC) at NASA/MSFC and (3) The JAXA SSIPC. There is no on-orbit crew involvement for CREAM nominal operations. The crew may be involved in Education and Public Outreach (EPO) events related to CREAM, but, that is to be determined in future payload planning sessions, and is not confirmed at this time.
The data interface is Ethernet and 1553. CREAM uses Software Toolkit for Ethernet Lab-Like Architecture (STELLA) to comply with the Consultative Committee for Space Data Systems (CCSDS) protocol requirements as specified in the documents Space Station Program (SSP) 52050 and CCSDS-102.0-B-5. The CREAM software is designed to interface with the Huntsville Operations Support Center Software (HOSC) to retrieve the data from the payload and send commands in real-time.
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Ground Based Results Publications
Ahn HS, Allison P, Bagliesi MG, Beatty JJ, Bigongiari G, Childers JT, Conklin NB, Coutu S, DuVernois MA, Ganel O, Han JH, Jeon JA, Kim KC, Lee MH, Lutz L, Maestro P, Malinin A, Marrocchesi PS, Minnick SA, Mognet SI, Nam J, Nam SW, Nutter SL, Park IH, Park NH, Seo E, Sina R, Wu J, Yang J, Yoon YS, Zei R, Zinn SY. Discrepant Hardening Observed in Cosmic-Ray Elemental Spectra. The Astrophysical Journal. 2010 May 1; 714(1): L89-L93. DOI: 10.1088/2041-8205/714/1/L89.
Seo E. Direct measurements of cosmic rays using balloon borne experiments. Astroparticle Physics . 2012 December; 39-40: 76-87. DOI: 10.1016/j.astropartphys.2012.04.002.
Ptuskin V, Zirakashvili V, Seo E. Spectrum of Galactic Cosmic Rays Accelerated in Supernova Remnants. The Astrophysical Journal. 2010 July 20; 718(1): 31-36. DOI: 10.1088/0004-637X/718/1/31.
Ahn HS, Allison P, Bagliesi MG, Beatty JJ, Bigongiari G, Boyle P, Childers JT, Conklin NB, Coutu S, DuVernois MA, Ganel O, Han JH, Jeon JA, Kim KC, Lee JK, Lee MH, Lutz L, Maestro P, Malinin A, Marrocchesi PS, Minnick SA, Mognet SI, Nam SW, Nutter SL, Park IH, Park NH, Seo E, Sina R, Swordy JP, Wakely SP, Wu J, Yang J, Yoon YS, Zei R, Zinn SY. The Cosmic Ray Energetics And Mass (CREAM) instrument. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. 2007 September; 579(3): 1034-1053. DOI: 10.1016/j.nima.2007.05.203.
Chang J, Adams, Jr. JH, Ahn HS, Bashindzhagyan GL, Christl M, Ganel O, Guzik TG, Isbert J, Kim KC, Kuznetsov EN, Panasyuk MI, Panov AD, Schmidt WK, Seo E, Sokolskaya NV, Watts JW, Wefel JP, Wu J, Zatsepin VI. An excess of cosmic ray electrons at energies of 300–800 GeV. Nature. 2008 November 20; 456(7220): 362-365. DOI: 10.1038/nature07477.
The Cosmic Ray Energetics and Mass (CREAM)
CREAM payload drawing.
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Existing CREAM hardware used for balloon flights.
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Students participating in assembly, integration and test of the CREAM instrument at the University of Maryland.
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