Schatten Solar Flux Files

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The Schatten-predicted Jacchia-Roberts files can be used as the predictor file for FreeFlyer's Jacchia-Roberts Density Model. These files provide predicted monthly mean smoothed estimates of future solar radiation along with weighted planetary geomagnetic index (Ap) to produce atmospheric density values which can be used in the calculation of drag on a spacecraft. The Ap index shows a large natural variability associated with geomagnetic storms which the user should be aware of.

 

The Schatten files are generally recommended for long term analysis. For short-term, high fidelity studies, the CSSI Space Weather file is recommended.

 

The Schatten files provide three cycle timing predictions - Nominal, Early, and Late. For each cycle there is a mean and estimated "+2 sigma" (plus) and "-2 sigma" (minus) error bounds, for a total of nine files. The "2 sigma" bounds are defined by the solar flux prediction team at NASA Goddard Spaceflight Center.

 

Plot showing the relative characteristics of the nine Schatten files

Plot showing the relative characteristics of the nine Schatten files

 

The input data is provided by Dr. Kenneth Schatten formally of Code 926 at Goddard Spaceflight Center (GSFC) who provides updates approximately every 3 to 6 months. This data can be downloaded at https://iswa.gsfc.nasa.gov/iswa_data_tree/model/solar/FDF/SchattenSolarFluxPrediction/.

 

The Schatten file format converts the smoothed solar flux to unsmoothed solar flux, converts the Ap to Kp, and interpolates the monthly values to daily values to fit the Jacchia-Roberts format and to coincide with the NOAA JR data. The files below are binary files in PC (little-endian) format.

 

The nine Schatten files are as follows:

 

Description

File Name

Nominal Mean

Meannom.dat

Nominal +2 sigma

Plusnom.dat

Nominal -2 sigma

Minusnom.dat

Early Mean

Meanearl.dat

Early +2 sigma

Plusearl.dat

Early -2 sigma

Minuearl.dat

Late Mean

Meanlate.dat

Late +2 sigma

Pluslate.dat

Late -2 sigma

Minulate.dat

 

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

 

 

Schatten JR File Format


The format of the Schatten JR files is noted below.

 

Schatten JR Atmospheric Density (Jacchia) File Layout
Record 1  (Header)          Size=252
-------------------------------------------------------------------------
Byte    |  Description
-------------------------------------------------------------------------
1-4     | IDAYS:   MJD of first data on file
5-8     | IDAYE:   MJD of last data on file
9-12    | NREC:    Number of records (=500)
13-16   | IDAYEM:  MJD of last measured data on file
17-20   | IFLAG:   Last maintenance operation indicator
       |  =1, create
       |  =2, add
       |  =3, modify
       |  =4, delete
21-28   | YMDHMS:  Date of last maintenance operation
29-252  | spare
-------------------------------------------------------------------------
Records 2-500                Size=252
-------------------------------------------------------------------------
Byte   |  Description
-------------------------------------------------------------------------
1-4    | IST:      MJD of first day in record
5-172  | KP(I,J):  I=1,21  J=1,4  (I*2)
      |   21 sets of packed geomagnetic indexes (x10), beginning with
      |   day IST-1. Geomagnetic indexes are packed 2 per J index
      |   (8 per day)
173-252| TC(I):    I=1,20  (R*4)
      |  20 exospheric temperatures (1 per day)
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