THE DMSP SPACE WEATHER SENSORS DATA ARCHIVE LISTING ( ) AND FILE FORMATS DESCRIPTIONS

Transcription

1 AFRL-RV-PS- TR AFRL-RV-PS- TR THE DMSP SPACE WEATHER SENSORS DATA ARCHIVE LISTING ( ) AND FILE FORMATS DESCRIPTIONS Daniel M. Ober, et al. 1 August 2014 Technical Report APPROVED FOR PUBLIC RELEASE; DISTRIBUTION IS UNLIMITED. AIR FORCE RESEARCH LABORATORY Space Vehicles Directorate 3550 Aberdeen Ave SE AIR FORCE MATERIEL COMMAND KIRTLAND AIR FORCE BASE, NM

2 DTIC COPY NOTICE AND SIGNATURE PAGE Using Government drawings, specifications, or other data included in this document for any purpose other than Government procurement does not in any way obligate the U.S. Government. The fact that the Government formulated or supplied the drawings, specifications, or other data does not license the holder or any other person or corporation; or convey any rights or permission to manufacture, use, or sell any patented invention that may relate to them. This report was cleared for public release by the 377 ABW Public Affairs Office and is available to the general public, including foreign nationals. Copies may be obtained from the Defense Technical Information Center (DTIC) ( AFRL-RV-PS-TR HAS BEEN REVIEWED AND IS APPROVED FOR PUBLICATION IN ACCORDANCE WITH ASSIGNED DISTRIBUTION STATEMENT. //SIGNED// //SIGNED// Dr. Gordon Wilson Glenn M. Vaughan, Colonel, USAF Project Manager, AFRL/RVBXP Chief, Battlespace Environment Division This report is published in the interest of scientific and technical information exchange, and its publication does not constitute the Government s approval or disapproval of its ideas or findings.

3 REPORT DOCUMENTATION PAGE Form Approved OMB No Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports ( ), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. 1. REPORT DATE (DD-MM-YYYY) 2. REPORT TYPE Technical Report 4. TITLE AND SUBTITLE The DMSP Space Weather Sensors Data Archive Listing ( ) and File Formats Descriptions 3. DATES COVERED (From - To) 1 Oct Aug a. CONTRACT NUMBER 5b. GRANT NUMBER 6. AUTHOR(S) Daniel M. Ober, Ernest Holeman 1, Frederick J. Rich 2, Louise C. Gentile, Gordon R. Wilson, and John S. Machuzak 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) Air Force Research Laboratory 1 Assurance Technology Corporation Space Vehicles Directorate 84 South Street 3550 Aberdeen Avenue SE Carlisle, MA Kirtland AFB, NM c. PROGRAM ELEMENT NUMBER 62601F 5d. PROJECT NUMBER e. TASK NUMBER PPM f. WORK UNIT NUMBER EF PERFORMING ORGANIZATION REPORT NUMBER AFRL-RV-PS-TR M.I.T. Lincoln Laboratory 244 Wood Street Lexington, MA SPONSORING / MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR S ACRONYM(S) AFRL/RVBXP 11. SPONSOR/MONITOR S REPORT NUMBER(S) 12. DISTRIBUTION / AVAILABILITY STATEMENT (377ABW dtd 27 Aug 14) 13. SUPPLEMENTARY NOTES 14. ABSTRACT The purpose of this document is to describe the file formats for the various file types in the Air Force Research Laboratory s (AFRL) Defense Meteorological Satellite Program (DMSP) space weather sensors data archive. While the file format descriptions of the various file types exist across a variety of sources, published and unpublished, no one publicly available document contains a comprehensive description of the file formats for all the various file types in the DMSP space weather sensors data archive. This document is intended to provide that resource. This document also contains a complete listing of all the files contained in the archive as of 1 Jan This document is not intended to provide detailed descriptions of the DMSP space weather sensors or comprehensive information on the quality of the data contained within the data files. Anyone who wishes to know more about the data that are available within AFRL s DMSP space weather sensors data archive and/or anyone who desires to write computer code for extracting information from those data files may find this document useful. 15. SUBJECT TERMS DMSP, SSJ, SSM, SSIES, File Format, Space Weather, Sensors 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT a. REPORT Unclassified b. ABSTRACT Unclassified 18. NUMBER OF PAGES c. THIS PAGE Unclassified Unlimited 72 19a. NAME OF RESPONSIBLE PERSON Dr. Gordon R. Wilson 19b. TELEPHONE NUMBER (include area code) Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std

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5 Table of Contents List of Figures. ii List of Tables. iii 1.0 Introduction Purpose of This Document Who Should Use This Document The Defense Meteorological Satellite Program Overview File Type Descriptions Overview of File Types and Contents The Ephemeris (EPH) Data Files The SSIES Driftmeter (DM) Data Files The SSIES Electron Langmuir Probe (EP) Data Files The SSIES Microprocessor (MP) Data Files The SSIES Ion Retarding Potential Analyzer (RPA) Data Files The SSIES Scintillation Meter (SM) Data Files The SSM Magnetometer Data Files The SSJ Data Files The SSIES Environmental Data Record (EDR) Data Files The SSM Magnetic Field Record (MFR) Data Files Big Endian versus Little Endian Encoding Further Reading 60 List of Symbols, Abbreviations, and Acronyms. 61 i

6 List of Figures Figure 1: DMSP geographic latitude versus local time and year in the northern hemisphere. 3 Figure 2: Local Time of DMSP ascending nodes by satellite and year 4 Figure 3: Local time of DMSP descending nodes by satellite and year 4 Figure 4: DMSP altitude by satellite and year. 5 Figure 5: Daily F10.7 index 5 Figure 6: Graphical display of available DMSP ephemeris data files 11 Figure 7: Graphical display of available DMSP SSIES driftmeter data files. 16 Figure 8: Graphical display of available DMSP SSIES electron Langmuir probe data files 21 Figure 9: Graphical display of available DMSP SSIES microprocessor data files. 25 Figure 10: Graphical display of available DMSP SSIES ion retarding potential analyzer data files. 30 Figure 11: Graphical display of available DMSP SSIES scintillation meter data files 34 Figure 12: Graphical display of available DMSP SSM magnetometer data files. 39 Figure 13: Graphical display of available DMSP SSJ data files 51 Figure 14: Graphical display of available DMSP SSIES EDR data files. 55 Figure 15: Graphical display of available DMSP SSM MFR data files 59 ii

7 List of Tables Table 1: Listing of DMSP flight numbers, launch dates, and sensors. 2 Table 2: File types and contents. 6 Table 3: File format description for the ephemeris data files 9 Table 4: Listing of available DMSP ephemeris data files 11 Table 5: File format description for the SSIES driftmeter data files. 12 Table 6: Listing of available DMSP SSIES driftmeter data files 15 Table 7: File format description for the SSIES electron Langmuir probe data files 17 Table 8: Listing of available DMSP SSIES electron Langmuir probe Data Files. 20 Table 9: File format description for the SSIES microprocessor data files. 22 Table 10: Listing of available DMSP SSIES microprocessor data files. 24 Table 11: File format description for the SSIES ion retarding potential analyzer data files. 26 Table 12: Listing of available DMSP SSIES ion retarding potential data files 29 Table 13: File format description for the SSIES scintillation meter data files. 31 Table 14: SM filter frequency ranges 33 Table 15: Listing of available DMSP SSIES scintillation meter data files. 33 Table 16: File format description for the SSM magnetometer data files (F07) 35 Table 17: File format description for the SSM magnetometer data files (F12-F18). 37 Table 18: Listing of available DMSP SSM magnetometer data files. 38 Table 19: File format description for the SSJ data files. 40 Table 20: SSJ5 sensor status word 1 description 42 Table 21: SSJ5 sensor status word 2 description 42 Table 22: SSJ sensor values for the channel central energy (E i ) and channel spacing ( E i ) 44 Table 23: SSJ sensor values for the electron channels geometric factors (G i ) for F6 through F Table 24: SSJ sensor values for the electron channels geometric factors (G i ) for F11 through F Table 25: SSJ sensor values for the electron channels geometric factors (G i ) for F16 through F Table 26: SSJ sensor values for the ion channels geometric factors (G i ) for F6 through F Table 27: SSJ sensor values for the ion channels geometric factors (G i ) for F11 through F Table 28: SSJ sensor values for the ion channels geometric factors (G i ) for F16 through F Table 29: Listing of available DMSP SSJ data files. 50 Table 30: File format description for the SSIES EDR data files 52 Table 31: Listing of available DMSP SSIES EDR data files 55 Table 32: File format description for the SSM MFR data files 57 Table 33: Listing of DMSP 2-digit flight numbers and 4-digit spacecraft ID numbers 58 Table 34: Listing of available DMSP SSM MFR data files 58 iii

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9 1.0 Introduction 1.1 Purpose of This Document The purpose of this document is to describe the file formats for the various file types in the Air Force Research Laboratory s (AFRL) Defense Meteorological Satellite Program (DMSP) space weather sensors data archive. While the file format descriptions of the various file types exist across a variety of sources, published and unpublished, no one publicly available document contains a comprehensive description of the file formats for all the various file types in the DMSP space weather sensors data archive. This document is intended to provide that resource. This document also contains a complete listing of all the files contained in the archive as of 1 Jan This document is not intended to provide detailed descriptions of the DMSP space weather sensors or comprehensive information on the quality of the data contained within the data files. Additional information can be found in the Further Reading section at the end of this document. 1.2 Who Should Use This Document Anyone who wishes to know more about the data that are available within AFRL s DMSP space weather sensors data archive and/or anyone who desires to write computer code for extracting information from those data files may find this document useful. 1.3 The Defense Meteorological Satellite Program Overview DMSP is a series of polar orbiting spacecraft assigned to monitor the meteorological, oceanographic, and solar-terrestrial environments. The principal sensor systems on the DMSP spacecraft are for observing tropospheric weather but the DMSP spacecraft also carry space environment sensors including the auroral particle spectrometer (SSJ), the fluxgate magnetometer (SSM), the topside thermal plasma monitor (SSIES) instruments, the ultraviolet spectrographic imager (SSUSI), and the ultraviolet limb imager (SSULI). Data from these instruments are widely utilized to study a wide range of auroral and low-latitude processes. AFRL s DMSP space weather sensors data archive only includes data from the SSJ, SSIES, and SSM instruments. Typically there are 2-4 satellites in orbit at any given time. Table 1 lists the DMSP satellites, launch dates, and the on-board space environment sensors. Each DMSP satellite has a ~101 minute, near-polar 98.9 degree inclination orbit at an altitude of ~850 km above the mean surface of the earth. The DMSP orbits are all nearly circular except for F10 whose orbit was slightly elliptical. Orbit planes 1

10 precess ~360 degrees per year and thus are nearly fixed in local time, typically near either the LT or LT planes. Figure 1 shows the DMSP geographic latitude versus local time and year in the northern hemisphere. The magnetometers on F07 and F12-F14 were body mounted but for F15 forward the magnetometers are boom mounted. Figure 2 shows the local times of the DMSP satellites ascending nodes versus time and Figure 3 shows the local times of the DMSP satellites descending nodes versus time. Notice that F6 through F9 were launched with their ascending nodes on the morning side while F10 through F18 have their ascending nodes on the evening side. The local times of some DMSP orbit planes have remained relatively fixed (e.g., F6 through F9, and F13) while some have drifted significantly in local time over their lifetimes (e.g., F15 has drifted ~6 hours of local time since originally being placed in orbit). While the local times of the DMSP orbital planes are relatively stationary, the DMSP spacecraft do sample a wide range of magnetic local times at high latitudes each day due to the offset of the Earth s magnetic axis relative to the geographic axis. Figure 4 shows the mean altitude of the DMSP satellites versus time. The mean altitude of the DMSP spacecraft is relatively stable, decreasing only slightly during the intervals , , and during the solar maxima. The mean altitude of F10 is less than the other DMSP spacecraft and its eccentricity is greater due to the partial failure of the final boost rocket. Figure 5 shows the daily F10.7 index over the lifetime of the DMSP space weather sensors data archive. This figure highlights one of the unique features of this data set, which is that the data set spans nearly 3 full solar cycles of measurements from a common set of instruments and orbits. This makes the DMSP data set distinctively useful both for long term studies as well as event studies. Table 1: Listing of DMSP flight numbers, launch dates, and sensors Flight Launch Date Sensors F6 December 1982 SSJ4 F7 December 1983 SSJ4, SSM F8 June 1987 SSJ4, SSIES F9 February 1988 SSJ4, SSIES F10 December 1990 SSJ4, SSIES F11 November 1991 SSJ4, SSIES2 F12 August 1994 SSJ4, SSIES2, SSM F13 March 1995 SSJ4, SSIES2, SSM F14 April 1997 SSJ4, SSIES2, SSM F15 December 1999 SSJ4, SSIES2, SSM F16 October 2003 SSJ5, SSIES3, SSM, SSUSI, SSULI F17 November 2006 SSJ5, SSIES3, SSM, SSUSI, SSULI F18 October 2009 SSJ5, SSIES3, SSM, SSUSI, SSULI F19 TBD SSJ5, SSIES3, SSM, SSUSI, SSULI F20 TBD SSJ5, SSIES3, SSM, SSUSI, SSULI 2

11 Figure 1: DMSP geographic latitude versus local time and year in the northern hemisphere 3

12 Figure 2: Local Time of DMSP ascending nodes by satellite and year Figure 3: Local time of DMSP descending nodes by satellite and year 4

13 Figure 4: DMSP altitude by satellite and year Figure 5: Daily F10.7 index 5

14 2.0 File Type Descriptions 2.1 Overview of File Types and Contents AFRL s DMSP space weather sensors data archive includes data from the SSJ, SSIES, and SSM instruments that is stored in 11 different file types. Table 2 below lists the different file types and their contents. Table 2: File types and contents File Type Ephemeris Data (Binary Files) SSIES Driftmeter Data (Binary Files) SSIES Electron Langmuir Probe Data (Binary Files) Data Quantities 1. Date, time, and spacecraft ID 2. Geodetic latitude, longitude, and altitude 3. Geographic latitude and longitude at 110 km altitude 4. Corrected geomagnetic latitude and longitude at 110 km altitude 5. Geomagnetic latitude and longitude 6. Geographic latitude and longitude of sub-solar point 7. Invariant latitude 8. Magnetic local time 9. Geographic x, y, and z components of satellite position unit vector 10. North, east, and down components of model magnetic field 11. Sath angle 1. Date, time, and spacecraft ID 2. Geodetic latitude, longitude, and altitude 3. Geographic latitude and longitude of sub-satellite point 4. Geographic latitude and longitude of sub-solar point 5. Geographic latitude and longitude at 110 km altitude 6. Corrected geomagnetic latitude and longitude at 110 km altitude 7. Invariant latitude 8. Magnetic local time 9. Geographic x, y, and z components of satellite position unit vector 10. North, east, and down components of model magnetic field 11. Vertical and horizontal drift speeds (6 samples per second) 1. Date, time, and spacecraft ID 2. Geodetic latitude, longitude, and altitude 3. Geographic latitude and longitude of sub-satellite point 4. Geographic latitude and longitude of sub-solar point 6

15 5. Geographic latitude and longitude at 110 km altitude 6. Corrected geomagnetic latitude and longitude at 110 km altitude 7. Invariant latitude 8. Magnetic local time 9. Geographic x, y, and z components of satellite position unit vector 10. North, east, and down components of model magnetic field 11. Electron density and temperature 12. Spacecraft potential SSIES Microprocessor Data (Binary Files) 1. Date, time, and spacecraft ID 2. Geodetic latitude, longitude, and altitude 3. Geographic latitude and longitude of sub-satellite point 4. Geographic latitude and longitude of sub-solar point 5. Geographic latitude and longitude at 110 km altitude 6. Corrected geomagnetic latitude and longitude at 110 km altitude 7. Invariant latitude 8. Magnetic local time 9. Geographic x, y, and z components of satellite position unit vector 10. North, east, and down components of model magnetic field 11. Ram ion drift speed 12. H + and O + density and temperature 13. Plasma potential relative to ground 14. Electron density and temperature SSIES Ion Retarding Potential Analyzer Data (Binary Files) SSIES Scintillation Meter Data (Binary Files) 1. Date, time, and spacecraft ID 2. Geodetic latitude, longitude, and altitude 3. Geographic latitude and longitude of sub-satellite point 4. Geographic latitude and longitude of sub-solar point 5. Geographic latitude and longitude at 110 km altitude 6. Corrected geomagnetic latitude and longitude at 110 km altitude 7. Invariant latitude 8. Magnetic local time 9. Geographic x, y, and z components of satellite position unit vector 10. North, east, and down components of model magnetic field 11. Ion density by species 12. Ion temperature 13. Ram ion drift speed 14. Spacecraft potential relative to plasma 1. Date, time, and spacecraft ID 7

16 2. Geodetic latitude, longitude, and altitude 3. Geographic latitude and longitude of sub-satellite point 4. Geographic latitude and longitude of sub-solar point 5. Geographic latitude and longitude at 110 km altitude 6. Corrected geomagnetic latitude and longitude at 110 km altitude 7. Invariant latitude 8. Magnetic local time 9. Geographic x, y, and z components of satellite position unit vector 10. North, east, and down components of model magnetic field 11. Ion density 12. Filter data SSM Magnetometer Data (ASCII Files) 1. Date and Time 2. Geodetic latitude, longitude, and altitude 3. Geomagnetic latitude and longitude 4. Magnetic local time 5. Spacecraft x, y, and z components of model magnetic field 6. Spacecraft x, y, and z components of measured minus model magnetic field SSM Magnetometer Data (Binary Files) 1. Date and time 2. Geodetic latitude, longitude, and altitude 3. Spacecraft x, y, and z components of measured minus model magnetic field SSJ Data (Binary Files) 1. Date and time 2. Geodetic latitude, longitude, and altitude 3. Geographic latitude and longitude at 110 km altitude 4. Corrected geomagnetic latitude and longitude at 110 km altitude 5. MLT 6. Ion and electron counts in 19 energy channels (30 ev to 30 kev) every second 7. Sensor status information (J5 only) SSIES Environmental Data Record (EDR) Data (ASCII Files) 1. Date, time, and spacecraft ID 2. Geographic latitude, longitude and altitude 3. Apex latitude, longitude, and local time 4. Total ion density 5. Spacecraft potential 6. Vertical and horizontal drift speeds 7. Electron density and temperature 8. Ion density by species 9. Ion temperature 10. Ram ion drift speed 11. Ion density filter data 8

17 SSM Magnetic Field Record (MFR) Data (ASCII Files) 1. Date, time, and spacecraft ID 2. Geographic latitude, longitude and altitude 3. Spacecraft x, y, and z components of measured magnetic field 4. Spacecraft x, y, and z components of measured minus model magnetic field 2.2 The Ephemeris (EPH) Data Files The ephemeris data files use the following naming convention: ephfnnyyddd where the bold characters are variable and the other (not bold) characters remain fixed. The bold characters have the following meaning: NN = 2 digit spacecraft flight number (06 through 20) YY = 2 digit year ddd = 3 digit day of year For example, the data file ephf would be the ephemeris data for F13 for 18 July The ephemeris data files are binary data files with the data stored as a series of 32-bit signed integers, and 8- bit bytes representing ASCII characters. The data files were written using big endian encoding. Table 3 below gives 1) a description of each variable contained in the file including the type of variable, expected range of the variable, and the variable units, 2) any conversion if necessary to convert the stored value to scientific units, and 3) the number of bytes used to store each data word. Table 3: File format description for the ephemeris data files Word Variable Description, Range, Units Conversion Bytes 1 Day of year, 001 to 366, days 4 2 Second of day, 0 to 86400, seconds 4 3 Integer year, 1987 to 2049, years 4 4 Geodetic latitude, to 90.0, degrees float(i)/ Geographic longitude, 0.0 to 360.0, degrees float(i)/ Altitude, 400 to 500, nautical miles float(i)/ Geographic latitude at 110 km altitude and float(i)/ on the same magnetic field line as the DMSP spacecraft, to 90.0, degrees 8 Geographic longitude at 110 km altitude float(i)/ and on the same magnetic field line as the DMSP spacecraft, 0.0 to 360.0, degrees 9 Corrected geomagnetic latitude at 110 km float(i)/ altitude, to 90.0, degrees 10 Corrected geomagnetic longitude at 110 km float(i)/

18 altitude, 0.0 to 360.0, degrees 11 Geomagnetic latitude, to 90.0, float(i)/ degrees 12 Geomagnetic longitude, 0.0 to 360.0, float(i)/ degrees 13 Geographic latitude of sub-solar point, float(i)/ to 90.0, degrees 14 Geographic longitude of sub-solar point, 0.0 float(i)/ to 360.0, degrees 15 Invariant latitude, 0.0 to 90.0, degrees float(i)/ Magnetic local time, 0.0 to 24.0, hours float(i)/ Geographic x-component of satellite float(i)/ position unit vector, 0.0 to 1.0, unitless 18 Geographic y-component of satellite float(i)/ position unit vector, 0.0 to 1.0, unitless 19 Geographic z-component of satellite float(i)/ position unit vector, 0.0 to 1.0, unitless 20 Northward component of model magnetic float(i)/ field at satellite, to , nt 21 Eastward component of model magnetic float(i)/ field at satellite, to , nt 22 Downward component of model magnetic float(i)/ field at satellite, to , nt 23 Sath angle, 0 to 2π, radians float(i)/ Spacecraft flight number, 6-20, unitless Magnetic field model used (e.g. IGRF95 ) Each 8 bit byte represents one 8 character using ASCII code (i.e. where 20 Hex represents a blank space, 30 to 39 Hex represents characters 0 to 9, and 41 to 5A Hex represents characters A to Z). 27 Zero fill Repeat of words 1-27 for next minute of 108 data Repeat of words 1-27 for next minute of 108 data Table 4 below is a listing of the currently available (as of 1 Jan 2014) DMSP ephemeris data files listed by spacecraft with the total number of available data files shown in parentheses. The data base contains a total of ephemeris data files for spacecraft F8 through F18 spanning from June 1987 through the present. Figure 6 below shows the same information graphically. 10

19 Table 4: Listing of available DMSP ephemeris data files Flight Number Dates F18 10/21/ /01/2014 (1534) F17 11/08/ /01/2014 (2612) F16 10/25/ /01/2014 (3722) F15 12/17/ /01/2014 (5130) F14 04/28/ /23/2008 (4136) F13 03/29/ /29/1996, 07/01/ /18/2009 (5348) F12 09/03/ /02/1995, 03/08/ /31/1995, 10/01/ /12/1997, 05/20/1997, 05/22/ /10/1997, 08/13/ /23/1997, 08/28/ /28/2002, 01/30/ /28/2002, 03/02/ /01/2002, 04/04/ /24/2002, 04/26/ /23/2002, 05/25/ /10/2002, 06/12/ /23/2002, 06/25/ /28/2002, 06/30/ /01/2002, 07/03/ /12/2002, 07/14/2002, 07/16/ /18/2002, 07/20/ /27/2002 (2823) F11 12/03/ /16/1991, 12/18/ /02/1995, 03/08/ /24/1995, 12/24/ /19/1998, 01/30/ /06/1998, 02/09/ /04/1998, 04/06/ /04/1998, 05/06/ /08/1998, 05/11/ /30/1999, 09/01/ /16/2000 (2030) F10 12/07/ /08/1990, 12/19/ /23/1991, 02/25/ /15/1991, 07/01/ /19/1991, 10/21/ /26/1994 (1363) F09 02/08/ /17/1988, 02/19/ /20/1990, 01/22/ /30/1990, 04/01/ /19/1991, 10/21/ /27/1992, 02/29/ /01/1992, 04/03/ /04/1992 (1512) F08 06/25/ /16/1987, 08/27/ /05/1987, 11/07/ /19/1991, 10/21/ /27/1993, 07/15/ /28/1994, 05/01/ /01/1994 (2474) Figure 6: Graphical display of available DMSP ephemeris data files 11

20 Additional information about the sensors or the meaning of the values contained within the files can be found in the Further Reading section at the end of this document. 2.3 The SSIES Driftmeter (DM) Data Files The SSIES driftmeter data files use the following naming convention: fnndmyymmmdd.dat where the bold characters are variable and the other (not bold) characters remain fixed. The bold characters have the following meaning: NN = 2 digit spacecraft flight number (06 through 20) YY = 2 digit year mmm = 3 character month (jan, feb, mar, apr, etc.) DD = 2 digit day of month For example, the data file f13dm09jul18.dat would be the driftmeter data for F13 for 18 July The data files are binary files with the data stored as a series of 8 bit (1 byte), 16 bit (2 bytes), 24 bit (3 bytes), or 32 bit (4 bytes) unsigned integers. The data files were written using big endian encoding. Variables not within the expected range have each byte set to 255. Missing data are zero filled. Table 5 below gives 1) a description of each variable contained in the file including the type of variable, expected range of the variable, and the variable units, 2) any conversion if necessary to convert the stored value to scientific units, and 3) the number of bytes used to store each data word. Table 5: File format description for the SSIES driftmeter data files Word Variable Description, Range, Units Conversion Bytes 1 Spacecraft ID ( F08 through F15 ) Each 8 bit byte represents one 5 character using ASCII code (i.e. where 20 Hex represents a blank space, 30 to 39 Hex represents characters 0 to 9, and 41 to 5A Hex represents characters A to Z). 2 Data file ID ( DM ) Each 8 bit byte represents one 6 character using ASCII code. 3 Integer year, 1987 to 2049, years i Day of year, 1 to 366, days 2 5 Hour of day, 0 to 24, hours 1 6 Minute of hour, 0 to 59, minutes 1 12

21 7 Geodetic latitude, to 90.0, degrees (float(i)/10.0) Geographic longitude, 0.0 to 360.0, degrees float(i)/ Geomagnetic latitude at sub-satellite point, (float(i)/10.0) to 90.0, degrees 10 Magnetic local time at 110 km field line float(i)/ intercept, 0.0 to 24.0, hours 11 Geomagnetic longitude at sub-satellite float(i)/ point, 0.0 to 360.0, degrees 12 Geographic latitude of sub-solar point, (float(i)/10.0) to 90.0, degrees 13 Geographic longitude of sub-solar point, 0.0 float(i)/ to 360.0, degrees 14 Geographic latitude at 110 km altitude and (float(i)/10.0) on the same magnetic field line as the DMSP spacecraft, to 90.0, degrees 15 Geographic longitude at 110 km altitude float(i)/ and on the same magnetic field line as the DMSP spacecraft, 0.0 to 360.0, degrees 16 Corrected geomagnetic latitude at 110 km (float(i)/10.0) altitude, to 90.0, degrees 17 Corrected geomagnetic longitude at 110 km float(i)/ altitude, 0.0 to 360.0, degrees 18 Invariant latitude, 0.0 to 90.0, degrees float(i)/ Altitude at the start of the minute, 400 to float(i) 2 500, nautical miles 20 Altitude at the end of the minute, 400 to float(i) 2 500, nautical miles 21 Northward component of model magnetic (float(i)/10.0) field at satellite, to , nt 22 Eastward component of model magnetic (float(i)/10.0) field at satellite, to , nt 23 Downward component of model magnetic (float(i)/10.0) field at satellite, to , nt 24 Geographic x-component of satellite (float(i)/ ) position unit vector, 0.0 to 1.0, unitless 25 Geographic y-component of satellite (float(i)/ ) position unit vector, 0.0 to 1.0, unitless 26 Geographic z-component of satellite (float(i)/ ) position unit vector, 0.0 to 1.0, unitless 27 Potential control model flag, 0 for vbias or 1 1 for senpot 28 Potential difference between spacecraft i-10 1 and electron probe ground, -3 to 28, volts 29 Potential difference between ion array and i-3 1 electron probe ground, -3 to 0, volts 30 Drift meter repeller grid functions, 0 to 16, unitless 1 13

22 31 Scintillation meter filter range commands, 0 1 to 16, unitless 32 No. of seconds of data for this minute, 1 to 1 60, unitless 33 Second of minute, 0 to 59, seconds 1 34 Vertical speed, 1 st sample of sec,-3000 to (10.0*float(i)) , meters/second 35 Vertical speed, 2 nd sample of sec,-3000 to (10.0*float(i)) , meters/second; or 1 st sample of raw data if H + mode 36 Vertical speed, 3 rd sample of sec,-3000 to (10.0*float(i)) , meters/second; or 2 nd sample of raw data if H + mode 37 Vertical speed, 4 th sample of sec,-3000 to (10.0*float(i)) , meters/second; or 3 rd sample of raw data if H + mode 38 Vertical speed, 5 th sample of sec (f,-3000 to (10.0*float(i)) , meters/second; or 4 th sample of raw data if H + mode 39 Vertical speed, 6 th sample of sec,-3000 to (10.0*float(i)) , meters/second; or 5 th sample of raw data if H + mode 40 Horizontal speed, 1 st sample of sec,-3000 to (10.0*float(i)) , meters/second 41 Horizontal speed, 2 nd sample of sec,-3000 to (10.0*float(i)) , meters/second; or 6 th sample of raw data if H + mode 42 Horizontal speed, 3 rd sample of sec,-3000 to (10.0*float(i)) , meters/second; or 7 th sample of raw data if H + mode 43 Horizontal speed, 4 th sample of sec,-3000 to (10.0*float(i)) , meters/second; or 8 th sample of raw data if H + mode 44 Horizontal speed, 5 th sample of sec,-3000 to (10.0*float(i)) , meters/second; or 9 th sample of raw data if H + mode 45 Horizontal speed, 6 th sample of sec,-3000 to (10.0*float(i)) , meters/second; or 10 th sample of raw data if H + mode 46 Ratio of LLA/LLB or indicates H + mode if 2 equal to Measured aperture potential, volts (float(i)/100.0) Zero fill Repeat of words for the next second 37 of minute Repeat of words for the next second of minute 37 14

23 Repeat of words for the last second of minute 993- Repeat of words for the next minute 1984 of data Repeat of words for the next minute 2977 of data Table 6 below is a listing of the currently available (as of 1 Jan 2014) DMSP SSIES driftmeter data files listed by spacecraft with the total number of available data files shown in parentheses. The data base contains a total of SSIES driftmeter data files for spacecraft F8 through F15 spanning from June 1987 through the present. Figure 7 below shows the same information graphically. Table 6: Listing of available DMSP SSIES driftmeter data files F15 12/16/ /03/2012, 07/05/ /08/2013, 04/13/ /01/2014 (5126) F14 04/28/ /23/2008 (4136) F13 03/29/ /14/1997, 12/16/ /18/2009 (5348) F12 09/03/ /02/1995, 03/08/ /12/1997, 05/20/1997, 05/22/ /10/1997, 08/13/ /23/1997, 08/28/ /30/2002, 02/01/ /03/2002, 02/05/ /07/2002, 02/09/ /19/2002, 02/21/ /26/2002, 02/28/2002, 03/02/ /03/2002, 03/05/ /01/2002, 04/03/2002, 04/05/ /13/2002, 04/15/2002, 04/17/2002, 04/19/ /23/2002, 04/25/2002, 04/27/ /10/2002, 05/13/ /25/2002, 05/28/ /30/2002, 06/02/ /10/2002, 06/12/2002, 06/14/ /22/2002, 06/25/ /28/2002, 06/30/ /01/2002, 07/03/ /12/2002, 07/14/ /18/2002, 07/20/ /27/2002 (2838) F11 12/03/ /16/1991, 12/18/ /02/1995, 03/08/ /24/1995, 12/24/ /27/1997, 01/01/ /19/1998, 01/30/ /06/1998, 02/09/ /04/1998, 04/06/ /04/1998, 05/06/ /08/1998, 05/11/ /10/1999, 01/13/ /16/2000 (1872) F10 12/07/ /08/1990, 12/19/ /23/1991, 02/25/ /19/1991, 10/21/ /26/1994 (1378) F09 02/08/ /17/1988, 02/19/ /30/1988, 04/01/ /20/1990, 01/22/ /30/1990, 04/01/ /27/1992, 02/29/ /31/1992 (1509) F08 06/25/ /10/1987, 08/27/ /05/1987, 11/07/ /27/1993, 07/15/ /01/1994 (2530) 15

24 Figure 7: Graphical display of available DMSP SSIES driftmeter data files Additional information about the sensors or the meaning of the values contained within the files can be found in the Further Reading section at the end of this document. 2.4 The SSIES Electron Langmuir Probe (EP) Data Files The SSIES electron Langmuir probe data files use the following naming convention: fnnepyymmmdd.dat where the bold characters are variable and the other (not bold) characters remain fixed. The bold characters have the following meaning: NN = 2 digit spacecraft flight number (06 through 20) YY = 2 digit year mmm = 3 character month (jan, feb, mar, apr, etc.) DD = 2 digit day of month For example, the file f13ep09jul18.dat would be the electron Langmuir probe data for F13 for 18 July The data files are binary files with the data stored as a series of 8 bit (1 byte), 16 bit (2 bytes), 24 bit (3 bytes), or 32 bit (4 bytes) unsigned integers. The data files were written using big endian encoding. Variables not within the expected range have each byte set to 255. Missing data are zero filled. 16

25 Table 7 below gives 1) a description of each variable contained in the file including the type of variable, expected range of the variable, and the variable units, 2) any conversion if necessary to convert the stored value to scientific units, and 3) the number of bytes used to store each data word. Table 7: File format description for the SSIES electron Langmuir probe data files Word Variable Description, Range, Units Conversion Bytes 1 Spacecraft ID ( F08 through F15 ) Each 8 bit byte represents one 5 character using ASCII code (i.e. where 20 Hex represents a blank space, 30 to 39 Hex represents characters 0 to 9, and 41 to 5A Hex represents characters A to Z). 2 Data file ID ( ELEC ) Each 8 bit byte represents one 6 character using ASCII code. 3 Integer year, 1987 to 2049, years i Day of year, 1 to 366, days 2 5 Hour of day, 0 to 24, hours 1 6 Minute of hour, 0 to 59, minutes 1 7 Geodetic latitude, to 90.0, degrees (float(i)/10.0) Geographic longitude, 0.0 to 360.0, degrees float(i)/ Geomagnetic latitude at sub-satellite point, (float(i)/10.0) to 90.0, degrees 10 Magnetic local time at 110 km field line float(i)/ intercept, 0.0 to 24.0, hours 11 Geomagnetic longitude at sub-satellite float(i)/ point, 0.0 to 360.0, degrees 12 Geographic latitude of sub-solar point, (float(i)/10.0) to 90.0, degrees 13 Geographic longitude of sub-solar point, 0.0 float(i)/ to 360.0, degrees 14 Geographic latitude at 110 km altitude and (float(i)/10.0) on the same magnetic field line as the DMSP spacecraft, to 90.0, degrees 15 Geographic longitude at 110 km altitude float(i)/ and on the same magnetic field line as the DMSP spacecraft, 0.0 to 360.0, degrees 16 Corrected geomagnetic latitude at 110 km (float(i)/10.0) altitude, to 90.0, degrees 17 Corrected geomagnetic longitude at 110 km float(i)/ altitude, 0.0 to 360.0, degrees 18 Invariant latitude, 0.0 to 90.0, degrees float(i)/ Altitude at the start of the minute, 400 to float(i) 2 500, nautical miles 20 Altitude at the end of the minute, 400 to float(i) 2 500, nautical miles 21 Northward component of model magnetic (float(i)/10.0)

26 field at satellite, to , nt 22 Eastward component of model magnetic (float(i)/10.0) field at satellite, to , nt 23 Downward component of model magnetic (float(i)/10.0) field at satellite, to , nt 24 Geographic x-component of satellite (float(i)/ ) position unit vector, 0.0 to 1.0, unitless 25 Geographic y-component of satellite (float(i)/ ) position unit vector, 0.0 to 1.0, unitless 26 Geographic z-component of satellite (float(i)/ ) position unit vector, 0.0 to 1.0, unitless 27 Potential control model flag, 0 for vbias or 1 1 for senpot 28 Potential difference between spacecraft i-10 1 and electron probe ground, -3 to 28, volts 29 Potential difference between ion array and i-3 1 electron probe ground, -3 to 0, volts 30 Drift meter repeller grid functions, 0 to 16, 1 unitless 31 Scintillation meter filter range commands, 0 1 to 16, unitless 32 No. of sets of data for this minute, 1 to 30, 1 unitless 33 Output type for 1 st set of data ( B for bias, ASCII code (i.e. where 41 to 5A 1 D for dwell, and S for sweep) Hex represents characters A to Z). 34 Repeat of word 33 for 2 nd set of data 1 35 Repeat of word 33 for 3 rd set of data 1 62 Repeat of word 33 for last set of data 1 If output type is B or S then 63 Second of minute for 1 st set of data, 0 to 59, 1 seconds 64 Langmuir probe mode for 1 st set of data, A ASCII code (i.e. where 41 to 5A 1 to E Hex represents characters A to Z). 65 Electron density, #/cm 3 10^(float(i)/100.0) 2 66 Spacecraft potential, Volts (float(i)/10.0) Electron Temperature, Kelvin 10^(float(i)/100.0) 2 68 Zero fill 1 If output type is D then 63 Second of minute for 1 st set of data, 0 to 59, 1 seconds 64 Langmuir probe mode for 1 st set of data, A ASCII code (i.e. where 41 to 5A 1 to E Hex represents characters A to Z). 65 Mean electron density for 1 st 4-seconds of 10^(float(i)/100.0) 2 18

27 10^(float(i)/100.0) 2 dwell, #/cm 3 66 Standard deviation of electron density for 1 st 4-seconds of dwell, #/cm 3 67 Zero fill 2 68 Zero fill Repeat of words for 2 nd set of data Repeat of words for 3 rd set of data Repeat of words for last set of data Repeat of words for the next minute 372 of data Repeat of words for the next minute 372 of data For F11 through F15, the raw SSIES EP data and the raw SSIES RPA data shared the same telemetry allocation. Only one of these two data sets could be in the telemetry at any given time. The raw RPA data was given priority over the raw EP data. Table 8 below is a listing of the currently available (as of 1 Jan 2014) DMSP SSIES electron Langmuir probe data files listed by spacecraft with the total number of available data files shown in parentheses. The data base contains a total of 5728 SSIES electron Langmuir probe data files for spacecraft F8 through F15 spanning from June 1987 through December Figure 8 below shows the same information graphically. 19

28 Table 8: Listing of available DMSP SSIES electron Langmuir probe Data Files F15 12/18/ /19/1999, 11/06/ /20/2001, 02/21/ /22/2002, 11/14/ /25/2002, 10/26/2008, 11/19/2008, 12/04/2008, 12/21/2008 (35) F14 11/10/ /01/1997, 11/10/ /01/1998, 11/05/ /01/1999, 03/14/ /16/2000, 11/06/ /20/2001, 03/26/2002, 11/14/ /25/2002 (102) F13 03/31/1995, 11/10/ /01/1997, 09/20/1998, 11/10/ /01/1998, 11/04/ /01/1999, 11/06/ /20/2001, 08/26/2002, 11/14/ /25/2002, 07/12/2006 (103) F12 09/04/ /05/1994, 09/08/1994, 09/23/1994, 11/10/ /01/1997, 11/10/ /01/1998, 12/05/ /06/1998, 11/05/ /01/1999, 03/18/2000, 05/12/2000, 06/07/2000, 08/19/2000, 08/24/2000, 09/08/2000, 09/16/2000, 09/18/2000, 10/10/2000, 11/05/2000, 03/03/2001, 11/06/ /20/2001, 11/30/2001, 12/17/ /19/2001, 12/27/ /28/2001, 01/04/2002, 02/10/2002, 02/18/2002, 03/08/2002, 03/11/2002, 05/17/2002 (115) F11 12/05/1991, 01/01/ /29/1992, 05/07/ /08/1992, 09/23/ /24/1993, 07/15/1994, 05/20/1998, 11/10/ /01/1998, 12/14/1998, 04/08/1999, 01/13/2000, 01/20/2000, 01/27/2000, 02/09/2000, 02/17/2000, 02/19/2000, 02/23/2000, 02/26/2000, 03/02/2000, 03/08/2000, 03/10/2000, 03/25/2000, 04/02/2000, 04/05/2000, 04/08/2000, 04/11/ /12/2000, 04/15/2000, 04/17/2000, 04/19/2000, 04/22/ /25/2000, 04/30/ /02/2000, 05/05/2000, 05/08/2000, 05/10/2000, 05/12/2000, 05/15/2000 (123) F10 12/07/ /08/1990, 12/19/ /23/1991, 02/25/ /19/1991, 10/21/ /26/1994 (1378) F09 02/08/ /17/1988, 02/19/ /30/1988, 04/01/ /20/1990, 01/22/ /30/1990, 04/01/ /27/1992, 02/29/ /31/1992 (1509) F08 06/25/ /10/1987, 08/27/ /05/1987, 11/07/ /15/1991, 03/01/ /27/1993, 07/15/ /28/1994 (2363) 20

29 Figure 8: Graphical display of available DMSP SSIES electron Langmuir probe data files Additional information about the sensors or the meaning of the values contained within the files can be found in the Further Reading section at the end of this document. 2.5 The SSIES Microprocessor (MP) Data Files The SSIES microprocessor data files use the following naming convention: fnnmpyymmmdd.dat where the bold characters are variable and the other (not bold) characters remain fixed. The bold characters have the following meaning: NN = 2 digit spacecraft flight number (06 through 20) YY = 2 digit year mmm = 3 character month (jan, feb, mar, apr, etc.) DD = 2 digit day of month For example, the data file f13mp09jul18.dat would be the microprocessor data for F13 for 18 July The data files are binary data files with the data stored as a series of 8 bit (1 byte), 16 bit (2 bytes), 24 bit (3 bytes), or 32 bit (4 bytes) unsigned integers. The data files were written using big endian encoding. Variables not within the expected range have each byte set to 255. Missing data are zero filled. The microprocessor file contains the results of onboard analysis of raw data by a microprocessor which uses algorithms which are less complex than the algorithms used in processing the raw data on the ground. Table 9 below gives 1) a description of each variable contained in the file including the type of 21

30 variable, expected range of the variable, and the variable units, 2) any conversion if necessary to convert the stored value to scientific units, and 3) the number of bytes used to store each data word. Table 9: File format description for the SSIES microprocessor data files Word Variable Description, Range, Units Conversion Bytes 1 Spacecraft ID ( F08 through F15 ) Each 8 bit byte represents one 5 character using ASCII code (i.e. where 20 Hex represents a blank space, 30 to 39 Hex represents characters 0 to 9, and 41 to 5A Hex represents characters A to Z). 2 Data file ID ( MICRO ) Each 8 bit byte represents one 6 character using ASCII code. 3 Integer year, 1987 to 2049, years i Day of year, 1 to 366, days 2 5 Hour of day, 0 to 24, hours 1 6 Minute of hour, 0 to 59, minutes 1 7 Geodetic latitude, to 90.0, degrees (float(i)/10.0) Geographic longitude, 0.0 to 360.0, degrees float(i)/ Geomagnetic latitude at sub-satellite point, (float(i)/10.0) to 90.0, degrees 10 Magnetic local time at 110 km field line float(i)/ intercept, 0.0 to 24.0, hours 11 Geomagnetic longitude at sub-satellite float(i)/ point, 0.0 to 360.0, degrees 12 Geographic latitude of sub-solar point, (float(i)/10.0) to 90.0, degrees 13 Geographic longitude of sub-solar point, 0.0 float(i)/ to 360.0, degrees 14 Geographic latitude at 110 km altitude and (float(i)/10.0) on the same magnetic field line as the DMSP spacecraft, to 90.0, degrees 15 Geographic longitude at 110 km altitude float(i)/ and on the same magnetic field line as the DMSP spacecraft, 0.0 to 360.0, degrees 16 Corrected geomagnetic latitude at 110 km (float(i)/10.0) altitude, to 90.0, degrees 17 Corrected geomagnetic longitude at 110 km float(i)/ altitude, 0.0 to 360.0, degrees 18 Invariant latitude, 0.0 to 90.0, degrees float(i)/ Altitude at the start of the minute, 400 to float(i) 2 500, nautical miles 20 Altitude at the end of the minute, 400 to float(i) 2 500, nautical miles 21 Northward component of model magnetic field at satellite, to , nt (float(i)/10.0)

31 22 Eastward component of model magnetic (float(i)/10.0) field at satellite, to , nt 23 Downward component of model magnetic (float(i)/10.0) field at satellite, to , nt 24 Geographic x-component of satellite (float(i)/ ) position unit vector, 0.0 to 1.0, unitless 25 Geographic y-component of satellite (float(i)/ ) position unit vector, 0.0 to 1.0, unitless 26 Geographic z-component of satellite (float(i)/ ) position unit vector, 0.0 to 1.0, unitless 27 Potential control model flag, 0 for vbias or 1 1 for senpot 28 Potential difference between spacecraft i-10 1 and electron probe ground, -3 to 28, volts 29 Potential difference between ion array and i-3 1 electron probe ground, -3 to 0, volts 30 Drift meter repeller grid functions, 0 to 16, 1 unitless 31 Scintillation meter filter range commands, 0 1 to 16, unitless 32 No. of sets of microprocessor outputs for 1 this minute, 1 to 15, unitless 33 Second of minute for 1 st set of data, 0 to 59, 1 seconds 34 Ram ion drift speed,-3000 to 3000, (10.0*float(i)) meters/second 35 O + ion temperature, Kelvin 10.0*float(i) 2 36 H + ion temperature, Kelvin 10.0*float(i) 2 37 O + ion density, #/cm 3 10^(float(i)/100.0) 2 38 H + ion density, #/cm 3 10^(float(i)/100.0) 2 39 Plasma potential relative to RPA ground, (float(i)/100.0) Volts 40 1 st electron temperature, Kelvin 10.0*float(i) st electron density, #/cm 3 10^(float(i)/100.0) st Plasma potential relative to spacecraft (float(i)/10.0) 2 ground, Volts 43 2 nd electron temperature, Kelvin 10.0*float(i) nd electron density, #/cm 3 10^(float(i)/100.0) nd Plasma potential relative to spacecraft (float(i)/10.0) 2 ground, Volts 46 Zero fill Repeat of words for 2 nd set of data Repeat of words for 3 rd set of data Repeat of words for last set of data Repeat of words for the next minute

32 of data Repeat of words for the next minute of data 492 Table 10 below is a listing of the currently available (as of 1 Jan 2014) DMSP SSIES microprocessor data files listed by spacecraft with the total number of available data files shown in parentheses. The data base contains a total of SSIES microprocessor data files for spacecraft F8 through F15 spanning from June 1987 through the present. Figure 9 below shows the same information graphically. Table 10: Listing of available DMSP SSIES microprocessor data files F15 12/16/ /03/2012, 07/05/ /24/2013, 03/26/ /08/2013, 04/13/ /01/2014 (5097) F14 04/28/ /23/2008 (4136) F13 03/29/ /18/2009 (5349) F12 09/03/ /02/1995, 03/08/ /12/1997, 05/20/1997, 05/22/ /10/1997, 08/13/ /23/1997, 08/28/ /30/2002, 02/01/ /03/2002, 02/05/ /07/2002, 02/09/ /19/2002, 02/21/ /26/2002, 02/28/2002, 03/02/ /03/2002, 03/05/ /01/2002, 04/03/2002, 04/05/ /13/2002, 04/15/2002, 04/17/2002, 04/19/ /23/2002, 04/25/2002, 04/27/ /10/2002, 05/13/ /25/2002, 05/28/ /30/2002, 06/02/ /10/2002, 06/12/2002, 06/14/ /22/2002, 06/25/ /28/2002, 06/30/ /01/2002, 07/03/ /12/2002, 07/14/ /18/2002, 07/20/ /27/2002 (2838) F11 12/03/ /16/1991, 12/18/ /02/1995, 03/08/ /24/1995, 12/24/ /27/1997, 01/01/ /19/1998, 01/30/ /06/1998, 02/09/ /04/1998, 04/06/ /04/1998, 05/06/ /08/1998, 05/11/ /10/1999, 01/13/ /16/2000 (1872) F10 12/07/ /08/1990, 12/19/ /23/1991, 02/25/ /19/1991, 10/21/ /26/1994 (1378) F09 02/08/ /17/1988, 02/19/ /30/1988, 04/01/ /20/1990, 01/22/ /30/1990, 04/01/ /27/1992, 02/29/ /31/1992 (1509) F08 06/25/ /10/1987, 08/27/ /05/1987, 11/07/ /27/1993, 07/15/ /01/1994 (2530) 24

33 Figure 9: Graphical display of available DMSP SSIES microprocessor data files Additional information about the sensors or the meaning of the values contained within the files can be found in the Further Reading section at the end of this document. 2.6 The SSIES Ion Retarding Potential Analyzer (RPA) Data Files The SSIES RPA data files use the following naming convention: fnnrpyymmmdd.dat where the bold characters are variable and the other (not bold) characters remain fixed. The bold characters have the following meaning: NN = 2 digit spacecraft flight number (06 through 20) YY = 2 digit year mmm = 3 character month (jan, feb, mar, apr, etc.) DD = 2 digit day of month For example, the data file f13rp09jul18.dat would be the RPA data for F13 for 18 July The data files are binary files with the data stored as a series of 8 bit (1 byte), 16 bit (2 bytes), 24 bit (3 bytes), or 32 bit (4 bytes) unsigned integers. The data files were written using big endian encoding. Variables not within the expected range have each byte set to 255. Missing data are zero filled. Table 11 below gives 1) a description of each variable contained in the file including the type of variable, expected range of the variable, and the variable units, 2) any conversion if necessary to convert the stored value to scientific units, and 3) the number of bytes used to store each data word. 25