Since 1960, the National Oceanic and Atmospheric Administration (NOAA) and the NASA have jointly operated a series of polar orbiting satellites that are collectively referred to as NPOES or POES. These satellites were primarily intended to measure meteorological data but some carried space weather sensors. The first of these satellites to carry space weather sensors was TIROS-N which stands for Television Infrared Observation Satellite and N for ‘Next generation’. TIROS-N collected data from November 1978-1981. It was followed by NOAA-A and NOAA-C which were later renamed after launch to be NOAA-6 and NOAA-7. In 1983 the NOAA-E or NOAA-8 satellite was launched, beginning a new series of satellites that were physically larger and had more power to accommodate a larger payload. A subset of the new series carried space weather sensors; NOAA-10 (or NOAA-G), NOAA-12 (or NOAA-H), NOAA-14 (or NOAA-J), NOAA-15 (or NOAA-K), NOAA-16 (or NOAA-L), NOAA-17 (or NOAA-M), NOAA-18 (or NOAA-N). The space weather sensors were updated beginning with NOAA-15. The latest in the series of satellites called MetOp-A (renamed after launch to be MetOp-2) is a joint NASA, NOAA, European Space Agency (ESA) project. The next polar satellite to be launched is NOAA-N’ in 2009 and MetOp-B in 2011. The follow on series of satellites is known as NPOESS and will carry an entirely new sensor suite as a joint NOAA, NASA and DoD project.
For more information about the NPOES mission, see
The NPOES satellites carry a number of environmental instruments including one instrument suite, called the Space Environment Monitor (SEM), which is designed to monitor the radiation environment of the earth's magnetosphere. This instrument suite consists of two instruments; the total electron detector (TED), which measures the energy flux of low energy protons and electrons (~60 eV to ~16 keV), and the Medium Energy Proton and Electron Detector (MEPED) measures the flux of higher energy particles (~30 keV to ~140 MeV). The instruments measure particles in two directions, approximately parallel and perpendicular to the local magnetic field direction. Two slightly different versions of the SEM instruments have been flown throughout the POES satellite era which has lasted several decades and is expected to continue until 2010. Satellites prior to NOAA-15, which was launched in 1998, carried the SEM-1 suite while NOAA 15 and later satellites carried the upgraded SEM-2 suite. A number of SEM-2 instruments have been procured and it is anticipated that the SEM-2 instruments will continue to be included on the NOAA/POES satellites until the POES program is replaced by the new NPOESS satellite program. The new program will include substantial improvements to the particle instruments.
- Instrument: SEM-1
The MEPED SEM-2 system measures electrons in 3 integral channels in two look directions. The electron measurements are sensitive to protons between 135 keV and 1 MeV. The system measures protons in 5 differential energy bands and 3 integral dome detector channels. The proton telescope detectors are sensitive to > 1 MeV electrons. All energies and look directions are not measured every second. First the 0 degree particles are measured and accumulated for 1 second and then the 90 degree particles are measured and accumulated for 1 second. The omnidirectional protons are measured once every every 2 seconds and accumulated for 2 seconds. All times correspond the end of the accumulation period.
For more information on the SEM-2 instrument, see SEM2v2.0.pdf and http://satdat.ngdc.noaa.gov/sem/poes/docs/sem2_docs
For instrument status information and notes about instrument changes, see 
ViRBO has processed the raw binary files for NOAA-15 onward. The data include the 2-second-resolution parameters in the raw binary files along with the corrected parameters described in Processing.
Daily CDF files are available at
There should be a one-to-one match between the content of these CDF files and the .bin files at http://satdat.ngdc.noaa.gov/sem/poes/data/full/ (except for the additional variables placed in the CDF file as described in the Processing). Some lower-resolution averages of the variables in binary files are also available in various formats (see http://satdat.ngdc.noaa.gov/sem/poes/data/readme.txt).
4.2.1. TED and SEM-1 on NOAA-14-
At http://cdaweb.gsfc.nasa.gov: NOAA 5/6/7/8/10/12/14 (MEPED SEM) 1-minute resolution count rates for 0 Deg. telescopes, 5 proton and 3 electron energy bands (counts_0dg), Count Rates for 81/83 Deg. telescopes, 5 proton and 3 electron energy bands (counts_90dg), Count Rates for omnidirectional proton telescope, 3 energy bands ounts_omni), calculated perpendicular proton flux, 5 energy bands (Jperp_p), calculated perpendicular electron flux, 3 energy bands (Jperp_e), calculated omnidirectional proton flux, 5 energy bands from 0/81 and 3 from omni telescopes, calculated omnidirectional electron flux, 3 energy bands from 0/83.
Source code for converting the NOAA-14- raw binary files to an ASCII table are available at http://virbo.org/svn/virbo/poes/noaa14-.
4.2.2. TED and SEM-2 on NOAA-15+
J. Green (NOAA/NSWPC) has computed corrected electron and proton parameters. The E1 detector is contaminated by 210-2700 keV protons. The E2 detector is contaminated by 280-2700 keV protons. And the E3 detector is contaminated by 440-2700 keV protons. These energy levels do not fall exactly on the proton energies that are measured. So for example, to calculate the counts that should be subtracted from the E3 detector you need to know what fraction of the counts in the P3 detector correspond to only those protons with energies greater than 440 keV. The answer depends very much on the energy spectrum of protons entering into the detector. And of course that changes with time. The ideal method for computing the corrections uses a generalized non-linear least-squares inversion of all the data. However, because of processing time constraints, an approach that used only data from a given day were used. A few more details about this are mentioned at .
The corrected proton parameters are derived via a change of units from #/cm^2-s-str to #/cm^2-s-str-keV using a bowtie method to find the energy width and center energy. The algorithm used is in http://virbo.org/svn/virbo/poes/noaa15+/unpack_sem2.f. You may check out this code by executing
and following the instructions in http://virbo.org/svn/virbo/poes/noaa15+/README