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Advanced Composition Explorer Level 2 CRIS 27-Day Cosmic Ray Fluxes, HDF


Availability: At NSSDC, Ready for Offline Distribution (or Staging if Digital)

Time span: 1997-08-14 to 2001-03-28


This data collection contains 27-day Level 2 data in binary Hierarchical Data Format (HDF) format from the Cosmic Ray Isotope Spectrometer (CRIS) instrument on the Advanced Composition Explorer (ACE) spacecraft. Data records contain 27-day (solar rotation) time averages of fluxes in units of particles/(cm^2*sr*sec*Mev/nucleon) in seven energy bands within the overall range of 100 - 500 MeV/nucleon for the following elements: B, C, N, O, F, Ne, Na, Mg, Al, Si, P, S, Cl, Ar, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, and Ni. Isotopic data are not included. Energy bands for each element are different and are listed in the text file cris_energy_bands.txt. Time periods during which solar activity is high are not covered by CRIS, since the instrument was not designed to operate during such conditions. The data are for a detector acceptance angle of 30 degrees. A data value of -999.9 indicates bad or missing data for the given time period. The number of counts is also given from which the statistical uncertainties can be calculated. Statistical flux uncertainties are computed from flux/sqrt(N), where N is the number of counts or events during the averaging period. The CRIS team currently recommends adding an additional 10% to the statistical uncertainties of higher Z elements and 15% for lower Z elements to reflect the geometry factor and trajectory detector efficiency uncertainties. Current release notes on Level 2 processing are given in the text file cris_release_notes.txt.

This collection is available on-line at:

Alternate Names

  • CRIS Level-2 27-Day Fluxes, HDF


  • Space Physics: Heliospheric Studies


  • 97-045A-06E

Additional Information



Questions and comments about this data collection can be directed to: Dr. John F. Cooper



NameRoleOriginal AffiliationE-mail
Dr. Andrew J. DavisGeneral ContactCalifornia Institute of
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