Function	IRCO_SUNLONG
 
 Purpose    calculate approximate ecliptic longitude of the sun from satcal
 
 Author	850927 A.R.W.de Jonge

 Category	IRAS, WORLD COORDINATES

 File		irco.shl
 
 Use doubleprecision function IRCO_SUNLONG( 
	satcal )	I	integer

 	satcal  	satcal clock time in ticks
 
 Description
	The routine calculates the approximate ecliptic longitude
       of the sun from the time given in IRAS satellite clock ticks.
 
       The ecliptic longitude of the sun is in radian with reference 
       to the ecliptic of date
 
       The accuracy is to about 30 arcsec.
 
 Update	DK adapted for Gipsy; satcal is now an integer