C+
C NAME:
C	EARTH
C PURPOSE:
C	Returns the heliographic or ecliptic longitude (in degrees) of the
C	sub-Earth point
C CATEGORY:
C	Celestial mechanics
C CALLING SEQUENCE:
	function EARTH(iYrIn,Doy)
C INPUTS:
C	iYr	integer		year
C				(if iYr<0 then the ecliptic longitude is returned)
C	Doy	real		day of year, including fraction for time of day
C OUTPUTS:
C	EARTH	real		heliographic longitude (degrees, 0<=EARTH<360)
C CALLS:
C	SunNewcomb, ECLIPTIC_HELIOGRAPHIC
C SEE ALSO:
C	XMAP_SC_POS
C PROCEDURE:
C	Typically used as external function to e.g. href=XMAP_SC_POS
C MODIFICATION HISTORY:
C	JAN-1991, Paul Hick (UCSD/CASS)
C	JUL-1993, Paul Hick (UCSD/CASS; pphick@ucsd.edu), added option to return ecliptic longitude
C-
	    integer	iYrIn
	    real	Doy

	double precision rLng
	double precision rLat
	double precision rDist

	iYr = abs(iYrIn)

	call SunNewcomb(0,iYr,Doy,rLng,rLat,rDist)
	XLNG = mod(sngl(rLng)+180.0,360.0)

	if (iYrIn .ge. 0) then
	    XLAT = 0.0
	    call ECLIPTIC_HELIOGRAPHIC(0,iYr,Doy,XLNG,XLAT)
	end if
	EARTH = XLNG

	return
	end