IONCOR

----+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8
IONCOR                                                                        
----+----0----+----0----+----0----+----0----+----0----+----0----+----0----+----0
                                                                                
COLUMNS FORMAT         DESCRIPTION                         DEFAULT VALUE & UNITS

1-6     A6     IONCOR - Requests the application of the
               ionospheric correction based on the ionospheric
               model IR-95.  [Ref. 1]                  
                                                                                
 7      I1     Indicates the type of coefficients to be used in
               the model. [NOTE 1]                                  0  
               = 0 CCIR coefficients                                
               = 1 URSI coefficients                               
                                                                                
 8      I1     Indicates the type of interpolation to be used
               for electron density profiles.                       0
               = 0 linear interpolation                             
               = 1 logarithmic interpolation (not tested yet)                   

NOTE [1]: CCIR - model recommended by the International Radio Consultative
                 Committee (1967) (Ref. 1 p. 52).
          URSI - Model proposed by the International Union of Radio Science
                 (1989) (Ref. 1 p. 52).
          Both sets of coefficient files must be included in the 
          directory of the IIS execution. Files are located on geodesy2
          in  /geod4/sluo/ion95  and on charney in /u3/zms0l/ion95.
          There are 24 files, 12 files of each type, one for each month of
          the year.  The filenames are in the following format:  ccir*.asc
          and ursi*.asc where * is equal to the month plus ten.

NOTE [2]: Frequencies used in the computation of the correction are
          obtained in one of two ways: 

          Option 1 - Frequencies provided. Nominal center or average
                     (over forward and return) frequencies per link
                     are included on columns 25-44 on the OFFSET input
                     cards. In this case an OFFSET card must be 
                     included for each satellite in the run. Also
                     frequencies must be input on all the OFFSET cards
                     or option 2 will be invoked.
          Option 2 - Frequencies computed in GEODYN, invoked only when
                     one or more OFFSET cards do not provide frequencies,
                     or OFFSET cards are not included in the setup.

NOV 1996

9611.0

GLOBAL SET

IONCOR (cont)

NOTE [3]: The earth orientation and flux tables used with the IONCOR
          option are special tables which include ionospheric indices.
          The analyst must use these tables with GEODYN IIS. However at this
          point TDF has not been modified to interpret the new tables format.
          With TDF runs the analyst should use the default GEODYN tables.

 [Ref. 1] Dieter Bilitza, "International Reference Ionosphere 1990.",
	  Nov. 1990. NSSDC/WDC-A-R&S 90-92.

MAY 1995

9505.0

GLOBAL SET