User-Created Atmospheric Drag File or ASCII JR File

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The CSSI Space Weather File is the recommended resource for atmospheric drag data for use with the Jacchia-Roberts or MSIS density models. However, for FreeFlyer users that wish to generate their own atmospheric drag data for these models, an ASCII form of the data file can be supplied. The ASCII formats of the file are collectively referred to as ASCII JR.

 

The data within the ASCII JR can be represented in several ways. Exospheric temperatures can be expressed directly as either exospheric temperature or as F10.7 values. Geomagnetic indices can be expressed as Kp on three hour centers or Ap on daily centers. All four possible combinations are supported. If the file provides F10.7 and/or Ap, the ingestion process will convert these values into exospheric temperature and Kp, respectively for use internally in the atmospheric density and drag computations. Since conversion of F10.7 to Exospheric temperature requires an 81 day average of F10.7 centered on the day in question, conversions for the first 40 days shall use the value given for the first day for all days prior, and likewise the value given for the last day for all days post. Note that when using an MSIS model, the provided file must contain F10.7 data.

 

The ASCII JR format requires two header lines. The first required line is the designation "JR File". The second required line begins with either the keyword "Temperature" or "F10.7", and following this will be either the keyword "Kp" or "Ap". Following the header lines are the data lines organized with a line per day. The data lines begin with a date followed by a set of floating point numbers. Fixed floating-point representation is supported with optional decimal point for whole numbers. All items must be delimited by white space (space or tab). The dates are represented as UTC calendar dates in the MMM DD YYYY format. Note the data within the file must be from first day to last day with every day specified. Breaks in the data will cause execution error when drag calculations need to be processed on or beyond the missing day. Following the date is the first floating point number that represents either the Exospheric Temperature or F10.7 value as specified in the header. If Kp values have been specified then the next eight floating point numbers specify the Kp values at 3-hour centers throughout the day starting at 00:00 UTC. If Ap values have been specified then the next single floating point number specifies the Ap value centered on the day.

 

Leading white space is permitted on all lines. Trailing characters following the required data are permitted on all lines and are ignored during the file ingest process. These are to accommodate trailing comments. Blank lines are permitted and ignored. Lines with the first non-white space character pattern of "//" are also ignored. These are to accommodate comment lines.

 

Two examples of the ASCII JR file are included with FreeFlyer and can be found in the FreeFlyer installation directory: solar_flux_ascii_sample_f107_kp.txt and solar_flux_ascii_sample_temp_ap.txt.

 

Example 1 (solar_flux_ascii_sample_f107_kp.txt):
 

// ----- beginning of file -----
// while data is given in neat columns, this is not required

// this is sample ASCII JR File only, it should not be considered historically accurate

// data is given as F10.7 flux and Kp

JR File

F10.7 Kp

      DEC 31 1999    151.540986991222980   5.666666666666667000   4.333333333333333000   3.666666666666666500   3.666666666666666500   4.000000000000000000   3.666666666666666500   4.666666666666667000   5.333333333333333000

      // one day should be given prior to first desired day of drag computations

      JAN 01 2000    151.299577877845280   5.333333333333333000   4.666666666666667000   4.000000000000000000   3.333333333333333500   4.333333333333333000   3.000000000000000000   4.333333333333333000   3.666666666666666500

      JAN 02 2000    152.337702998408560   3.000000000000000000   3.333333333333333500   3.333333333333333500   3.333333333333333500   2.666666666666666500   3.333333333333333500   3.333333333333333500   3.000000000000000000

      // comments lines can be inserted anywhere in the file

      JAN 03 2000    152.219833562403550   3.333333333333333500   3.000000000000000000   2.666666666666666500   2.666666666666666500   2.333333333333333500   2.333333333333333500   3.000000000000000000   1.666666666666666700

      JAN 04 2000    152.676994417920530   2.333333333333333500   2.333333333333333500   2.333333333333333500   3.000000000000000000   3.333333333333333500   2.666666666666666500   2.333333333333333500   3.666666666666666500

      JAN 05 2000    153.279471691743820   4.000000000000000000   3.333333333333333500   3.333333333333333500   3.333333333333333500   2.333333333333333500   3.000000000000000000   3.666666666666666500   4.000000000000000000

      JAN 06 2000    156.544664171006930   2.666666666666666500   3.333333333333333500   2.000000000000000000   3.333333333333333500   4.333333333333333000   4.333333333333333000   3.000000000000000000   3.333333333333333500

// ----- end of file -----

 

Example 2 (solar_flux_ascii_sample_temp_ap.txt):

 

Note: This file could not be used for MSIS modeling because it does not contain F10.7 data.
 

// ----- beginning of file -----

// while data is given in neat columns, this is not required

// this is sample ASCII JR File only, it should not be considered historically accurate

// data is given as exospheric Temp and Ap

JR File

Temperature Ap

      DEC 31 1999    879.694105918406190   32.381374467780276000

      // one day should be given prior to first desired day of drag computations

      JAN 01 2000    879.983400628290840   27.338249286499650000

      JAN 02 2000    881.899382577438700   16.370416223637342000

      // comments lines can be inserted anywhere in the file

      JAN 03 2000    882.260493469935800   12.050141838932149000

      JAN 04 2000    883.349895415082870   12.951670365243785000

      JAN 05 2000    884.629920037340300   18.372984552657904000

      JAN 06 2000    889.356168528624830   17.544789907821162000

// ----- end of file -----

 

Note: FreeFlyer uses 0th order interpolation (last defined value) when querying an epoch that is not contained in the file.