NOAA's Polar Orbiting Environmental Satellites (POES) and the EUMETSAT MetOp satellites carry a suite of instruments that measure the flux of energetic ions and electrons at the altitude of the satellites (at Low Earth Orbit - polar orbits). This charged particle environment varies as a result of solar and geomagnetic activity. The Space Weather suite of instruments is known as the Space Environment Monitor (SEM). The Space Environment Monitor-2 (SEM-2), which was first launched on the NOAA-15 satellite and flies on the MetOp-A, -B and -C, is an upgraded version of Space Environment Monitor-1 (SEM-1). As of November 28th 2023, the POES Constellation formally transitioned to Extended Life (EL) operations for all 3 operational satellites (NOAA 15, 18, and 19). See “Important Notices” tab for more information.
Additional Information about SEM processing and Archive workflow
The SEM processing and archive workflow was completely revised between SEM-1 and SEM-2. SEM-2 has a significantly different set of instruments than the earlier SEM-1. Additional upgrades include improved data quality control and the incorporation of up-to-date satellite orbit information and magnetic field models in various magnetic coordinate calculations.
Instruments
Total Energy Detector
The Total Energy Detector (TED) is designed to measure the energy flux that auroral particles — both positively charged ions (assumed here to be protons) and electrons with energies ranging from 0.05 keV to 20 keV — carry into the polar atmosphere. The magnitude and spatial extent of this energy flux are good measures of both the level of auroral activity and the atmospheric response to that energy input.
Medium Energy Proton and Electron Detector
The Medium Energy Proton and Electron Detector (MEPED) includes a set of solid-state energetic particle detectors that monitor the intensities of protons and electrons over a range extending from 30 keV to more than 200 MeV. Particles in that energy range include the radiation belt populations, solar particle events, and the lower energy galactic cosmic rays. When enhanced fluxes of these particles enter the atmosphere, they can produce significant and widespread degradation in short-wave radio propagation. They can even cause radio blackouts in extreme cases. Energetic particles also contribute to astronaut radiation exposure, especially on high inclination orbit missions during energetic solar particle events.
General Time Coverage by Satellite
- TIROS-N 1978-11–1981-02 (Introduction of SEM-1)
- NOAA-06 1979-07–1986-11
- NOAA-07 1981-08–1985-01
- NOAA-08 1983-05–1985-10
- NOAA-10 1986-10–1991-08
- NOAA-12 1991-06–2001-03
- NOAA-14 1994-01–2004-12
- NOAA-15 1998-07–2023-11-28 (Extended Life operations are planned to be continued through September 2025) (Introduction of SEM-2)
- NOAA-16 2001-01–2014-06
- NOAA-17 2002-07–2013-04
- NOAA-18 2005-06–2023-11-28 (Extended Life operations are planned to be continued through September 2025)
- METOP-02 (A) 2006-12–2021-11
- NOAA-19 2009-02–2023-11-28 (Extended Life operations are planned to be continued through September 2025)
- METOP-01 (B) 2012-10–present
- METOP-03 (C) 2019-01–present
See “Important Notices” tab for more information.
Access Methods
POES and Meteorological Operational Satellite (MetOp) SEM data and products are updated daily. You can access the same directory structure through https and File Transfer Protocol (FTP).
Until 2014, SWPC was responsible for POES/MetOp data files processing, creating the following data levels:
- Raw Level 0b Data (1978-2014 .bin files)
- Processed Level 2 Data (1998-2014 .txt and .cdf files)
After 2014, NCEI (formerly NGDC) took on the responsibility for POES/MetOp data files processing, creating the following data products:
- Raw Level 1a Data (2012 - present .nc files)
- Processed Level 1b Data (2012 - present .nc files)
- Radiation Belt Indices (2013 - present .txt files)
Note: Please review the “Important Notices” tab when using POES SEM software and archived data.
Binary Archive File Decoding Software
POES Processing Updates
In April 2013, NGDC began a new era of POES processing. The following documents describe those data:
SEM Channel Response Functions
The response functions of the SEM-1 and SEM-2 MEPED omnidirectional detectors have been simulated by Dr. T. E. Cayton. NCEI has made these response functions available to the public at the following links, along with documentation that is important for proper use of the functions::
(The response functions of the SEM-2 MEPED electron and proton telescopes have been simulated by Yando et al. DOI: 10.1029/2011JA016671).
SWPC Processed Data Documentation (Nov 1978 - Dec 2012)
- Space Environment Monitor-1 (SEM-1) Documentation for TIROS-N through NOAA-14:
- Space Environment Monitor-2 (SEM-2) Documentation for NOAA-15 and later satellites:
- SEM-2 document version 1.2 November 2002
- SEM-2 document version 1.3 January 2004
- SEM-2 document version 1.4 January 2004
- SEM-2 document version 2.0 2006
- Appendix A: Archive record description
- Appendix B: Conversion table for MEPED and TED counts
- Appendix C: TED Sensor Data Grouped by Unit Serial Number, rev 2006
- Appendix D: C Language Program to Read an Archive Record
- Appendix E: FORTRAN Language Program To Read an Archive Record, rev 2009
- Appendix F: Procedures to recover energetic proton number fluxes from the Omni directional detector responses
- Appendix G:: Processing Problems, Instrument Problems, rev 2007
- Figures
- Errata for SEM2 Documentation version 2.0
- NOAA-KLM User Guide with N' Supplement.
- StatusJanuary 7, 2002 (NOAA-12, NOAA-14, NOAA-15, & NOAA-16)
Additional Documentation
- Column descriptions for the Level-2 16-sec averaged data in ASCII file. Please note that the time stamps are provided at the center of the 16-second interval.
- The NORAD orbital elements for NOAA and TIROS- N satellites are available from CelestraK.
- POES SEM-2 Used to Examine Radiation Belt
- Origin of Energetic Electron Precipitation (Appendix A: Removing Proton Contamination From the POES MEPED Electron Measurements)
- J.B.Blake and W.A.Kolasinski, Aerospace Corporation --Preliminary Evaluation of HEPAD Performance
- NOAA Technical Memorandum ERL SEL-75, The TIROS-N / NOAA A-J Space Environment Monitor Subsystem, R.A. Seale and R.H. Bushnell, April 1987, Part I,Part II
- Evans, D.S., 1994.A study of intense auroral electron precipitation events. In Proceedings of the Second Space Environment Center Users Conference, Boulder, CO.
- Leap Calendar
Static Displays of NOAA Data
- NOAA-11 anomalies plotted on a background of NOAA-10 electron fluxes. (GIF)
Stack plots showing the NOAA-12 > .3 MeV electrons at L4.5 - L4.8 and GOES-8 > 2 MeV electrons at L6.6. These plots show the effect of smoothing on the NOAA-12 data, an algorithm for detecting NOAA-12 event start and peak times, and an exponential decay model for those events. (PDF, 12/23/98)
Dynamic Displays of NOAA Data
Sample Movies 2003 Halloween Event
Sample Movie 2003 Halloween Event Table Particle Type Cylindrical Orthographic MEPED E1: electrons > 30 keV, Zenith (0°) MEPED E1 orth movie (0°) MEPED E3: electrons > 300 keV, Zenith (0°) MEPED E3 orth movie (0°) MEPED E1: electrons; 30 keV, Horizon (90°) MEPED E3: electrons > 300 keV, Horizon (90°) MEPED E3 orth movie (90°) MEPED P2: protons 80-240 keV, Zenith (0°) MEPED P2 orth movie (0°) MEPED P4: protons 800-2500 keV, Zenith (0°) MEPED P4 orth movie (0°) MEPED P6: protons > 6900 keV, Zenith (0°) MEPED P6 orth movie (0°) MEPED P2: protons 80 - 240 keV, Horizon (90°) MEPED P2 orth movie (90°) MEPED P4: protons 800 - 2500 keV, Horizon (90°) MEPED P4 orth movie (90°) MEPED P6: protons > 6900 keV, Horizon (90°) MEPED P6 orth movie (90°)
About Outages and Processing Issues
Review these alerts when using POES SEM software or archived data for more information about outages and processing issues.
2023-12-26
Summary and explanation of the availability of POES SEM-2 data from NOAA 15, 18 and 19 under Extended Life (EL) operations.
As of November 28th 2023, the POES Constellation formally transitioned to EL operations for all 3 operational satellites which now utilize a commercial ground service. Operational statuses and or messages will only be provided via OSPO pages. POES Science Data will continue to flow through the existing NOAA NESDIS pipelines, though data gaps or delays may exist as POES now operates as a best effort, 'data of opportunity' mission. In response to any items noticed by mission partners during EL Operations, data outage reporting or questions can be sent to ESPCOperations@noaa.gov / (301) 817-3880.
What does 'best effort' mean? Is it 8x5?
POES Operations is now only staffed 8x5 of which limits the ability to quickly respond to any known data outages and issues, though there is still limited overnight monitoring of the satellites for health and safety purposes. There is no guarantee that all 3 of the satellites will remain fully operational in the EL period, which at this time is planned to be continued through September 2025.
What are the contractual requirements for data availability?
All data from the satellites under EL operations are considered 'data of opportunity.' There are no performance or data delivery latency requirements levied on the POES Constellation during EL Operations. Science data will continue to flow through the existing NOAA NESDIS pipelines. Retransmission and playback of missed data are neither required nor guaranteed, thus creating potential data gaps in observations. Recovery actions in response to science processing anomalies are performed during normal business hours. No near real-time notifications regarding POES outages will be provided; notifications following a data disruption issue will be provided to the community on a best effort basis.
How long are the EL operations funded / planned?
NOAA-15, -18 and -19 have all transitioned to EL operations as of November 28th 2023. Presently, EL operations are planned to be continued through September 2025.
2013-05-24
NOAA’s Space Weather Prediction Center (SWPC) resumed processing.
2013-04-31
A new directory structure was phased in for all POES data.
2013-01-01 -- POES/METOP Data Discontinued
Note: SWPC resumed processing POES data in May of 2013
NOAA's Space Weather Prediction Center (SWPC) has discontinued processing of the POES data files. SWPC says that production may resume at a later date, but nothing is definite at this time. NGDC is working to assume the processing of these data in the future, the current projection is for the new processing to begin in March of 2013.
2012-03-12 -- POES/METOP Data Resumed
SWPC has resumed processing of the POES data files, NOAA data resume 3/8, MetOp data 3/9.
2012-02-29 POES/METOP Data Discontinued
NOAA's Space Weather Prediction Center (SWPC) has discontinued processing of the POES data files. SWPC says that production may resume at some later time but that nothing is definite at this time.
2011-07-11 POES/METOP Files Truncated
We have satellite data coming from 5 POES satellites and 1 MetOp satellite to NOAA/NWS/SWPC (Space Weather Prediction Center). There was a problem that the MetOp data was being truncated by as much as eight hours each day starting on 9 June 2011 as seen on the NGDC quality control plots. The problem was resolved and plots reflect this starting on July 5, 2011.
2011-04-25 POES Files Truncated
These POES files don't have an integral number of records.
- PoesSummary says this file is incomplete poes_m02_20070308.bin (doy:067) size is 4956160 bytes, 448 leftOver bytes
- PoesSummary says this file is incomplete poes_m02_20080221.bin (doy:052) size is 2686976 bytes, 512 leftOver bytes
- PoesSummary says this file is incomplete poes_m02_20080912.bin (doy:256) size is 2678784 bytes, 2496 leftOver bytes
- PoesSummary says this file is incomplete poes_m02_20081016.bin (doy:290) size is 4481024 bytes, 1040 leftOver bytes
- PoesSummary says this file is incomplete poes_m02_20090204.bin (doy:035) size is 708608 bytes, 1376 leftOver bytes
NGDC has complete data files in RAW format, however, no access to the conversion software.
2009-04-24 Fortran Error Corrected in Unpacking Routine
A minor error has been uncovered in the FORTRAN version of the SEM-2 archive file unpacking routine (subroutine readArcSub) that is detailed in Appendix E of the SEM-2 Instrument Descriptions and Archive Data Documentation. About 20 lines from the end of this FORTRAN subroutine code the statement: if(mdf(2,3).eq.1) tedback(2,3) = -999. should be replaced with if(mdf(26,j).eq.1) tedback(2,3) = -999. A revised Appendix E (Appendix E_rev1.pdf) is available and the code file has been revised.
This error affected only the background readout from the 30-degree, 1-20 keV proton analyzer in the TED instrument complement. This single data point is the tedback (2,3) entry in the tedback array returned from the unpacking routine. The error arises only in cases when that data point was lost in the processing of the data received from the satellite and a default pad value was inserted in its place. In those instances the unpacking routine did not access the missing data flag correctly and returned a value of 1998848.0 for that tedback entry rather than the correct value of –999.0 for missing data. This particular error occurred on the average of 1 or 2 times a day and did not affect any other data point in the SEM-2 archive data. Finally, this error was not present in the C version of the SEM-2 archive data unpacking routine.
2008-04-22 MetOp Orbital Maneuvers
It has come to our attention that during instances when the MetOp satellite exercises orbital maneuvers the entire SEM-2 instrument is turned off. Unfortunately the data processing software does not recognize when the SEM-2 data processing unit (DPU) has been turned off and so assumes that the data received from the TED and MEPED detectors, that had been turned off, are valid in spite of the fact those data are zero-fill during these periods. The TED and MEPED instrument ON-OFF flags in the daily archive files are not properly set to OFF at these times.
Those periods of time during which the SEM-2 instrument on MetOp were turned off are:
- April 19, 2007 between 0819:58 and 1616:14 UTC
- April 24, 2007 between 0000:00 and 1359:27 UTC
- July 12, 2007 between 0922:22 and 1538:22 UTC
- Sept. 18, 2007 between 1454:10 and 2400:00 UTC
- Sept. 19, 2007 between 0000:00 and 1402:58 UTC
- Jan. 31, 2008 between 0921:30 and 1538:33 UTC
- April 8, 2008 between 0732:23 and 2400:00 UTC
- April 9, 2008 between 0000:00 and 0437:58 UTC
The TED and MEPED ON-OFF flags in the MetOp archive files for these days have been corrected and the corrected files are available.
2008-01-07 Revised NOAA-16 file for day 2007-07-09
It was discovered that orbital data contained in the NOAA-16 archive file for July 9, 2007 (day 190) was incorrect for times after 2035:11 UT. A revised NOAA-16 archive file for that day has been produced that eliminated records with incorrect orbital information.
2007-03-23 Revised NOAA-18 archive files
Revisions to NOAA-18 archive data files for July 23-24, 2005 and for the entire period July 11, 2006 through December 26, 2006 were necessary because incorrect calibration data for the TED instrument were used. These revisions impacted only the TED auroral particle energy flux values and many of the data quality flags. All of the MEPED data in the original archive data files were correct.
Users of TED data for these periods are advised to download the revised archive data files for NOAA-18.
2005-08-16 ERRATA: Software errors in unpackSem2.c since 2000
It has been brought to our attention by a user of POES SEM-2 data that the C language archive unpacking routine returns anomalous sensor values during periods where there are data missing as flagged by 999. We have examined that code and uncovered two significant errors in the C version of the code that have existed since 2000.
Both errors involve the way the C unpacker implements missing data flags. The first error centered around the fact that missing data flags associated with sensor data from the second half of the 32-second archive record were being improperly unpacked from the binary archive record. The consequences of that error were that TED and MEPED sensor values during periods when data were missing were often improperly flagged with valid data being set to -999. indicating missing data, while entries that should have been flagged as missing data were given count values of 19988488, the highest count value possible.
The second error also involved the implementation of missing data flags and impacted P8 and P9 omni-directional detector data throughout an entire 32-second archive record. The P8 and P9 data share the same data word in the TIROS data format and readouts alternate between the two. In the archive record the data listing for P8 alternates between valid data readouts and values set to 0 in the archive format while the P9 data alternates in the same fashion but with valid readouts when the P8 value is zero. The existing documentation explains this and a user is expected to extract only the appropriate entries when using P8 and P9 data. During instances when data were missing, the C unpacker assigned the missing data flag (-999.), in both the P8 and P9 data, to the entry appropriate to 'no data' while the entries appropriate to valid data were given count values of 19988488. This count value is unphysical for P8 and P9 data.
Both these errors would have impacted upon any analysis that had not recognized these unphysical sensor counts.
The FORTRAN version of the archive record unpacker did not have either of these problems.
Corrected software (unpackSem2_v2.c) is now available for distribution.
