The Space Environment Monitor (SEM) instrument onboard the NOAA POES satellite series and MetOp satellite series measures the flux of energetic ions and electrons at the altitude of the satellite. This data is used to detect and monitor space weather activity that may disrupt radio communications and/or the proper operation of satellite systems. The NOAA Space Weather Prediction Center (SWPC) processes the particle counts received from SEM instruments and uses the data to monitor solar activity and the state of the Earth's near space environment. Observations are acquired by the SEM Total Energy Detector (TED) and the SEM Medium Energy Proton and Electron Detector (MEPED). SEM/TED measures the energy flux of auroral particles for both positively charged ions (assumed here to be protons) and electrons, into the polar atmosphere. SEM/MEPED monitors the intensities of protons and electrons over a range extending from 30 keV to more than 200 MeV. Particles having those energies include the radiation belt (Van Allen belt) populations, the particles in energetic solar particle events (solar proton events), and the low energy portion of the galactic cosmic ray population. This data collection includes Level 0b raw counts (operation data stream) acquired by the SEM-1 and SEM-2 instruments and the following derived products generated from SEM-2 instrument observations: Level 1a count rates, Level 1b flux, and Level 2 count rates. The Level 0b raw counts are produced operationally by the NOAA National Environmental Satellite Data, and Information Service and distributed by NOAA’s National Center for Environmental Information (NCEI) as orbital files or daily Tar files in NetCDF and binary formats. The derived L1a, L1b, and Level 2 products are produced by NCEI and distributed by NCEI as daily files or monthly Tar files in the NetCDF format. The temporal period of record extends from Nov 1978 to the present for the operational data stream; from Jan 2012 to the present for the L1a and L1b products; and from July 1998 to Dec 2014 for the L2 product.