;+
; NAME:
;	BZero
; PURPOSE:
;
; CALLING SEQUENCE:
	FUNCTION BZero, T, degrees=degrees, lzero=L0
; INPUTS:
;	T		array; type: standard time structure
;				times where B0 angle is requested
; OPTIONAL INPUT PARAMETERS:
;	/degrees	if set, output angles BZero and L0 are in degrees
;			(default: radians)
; OUTPUTS:
;	Result	heliographic latitude of the sub-Earth point (center
;			of the disk)
; OPTIONAL OUTPUT PARAMETERS:
;	L0		heliographic longitude of the sub-Earth point
; INCLUDE:
	@compile_opt.pro			; On error, return to caller
; CALLS:
;	big_eph, jpl_body, SyncDims
; PROCEDURE:
; >	For time T the heliocentric ecliptic longitude of the sub-Earth
;	point is L=180+(geocentric ecliptic longitude Sun); the
;	heliocentric latitude is D=-(geocentric latitude).
;	The heliographic latitude of the sub-Earth point follows by
;	converting L,D at time T.
;
;	1971, doy 1.0 : B0 = -3.00629,  L0 = 129.631
;			B0 = -3.01   ,  L0 = 129.62  (Nautical Almanac)
;
; > 	using the /Precision keyword in NewcombSun produces worse results
; MODIFICATION HISTORY:
;	JUN-1993, Paul Hick (UCSD/CASS)
;	FEB-1998, Paul Hick (UCSD/CASS)
;		Replaced /radians keyword by /degrees keyword
;	OCT-2006, Paul Hick (UCSD/.CASS; pphick@ucsd.edu)
;		Replaced NewcombSun by big_eph call
;-

L0 = big_eph( T, $
		body = jpl_body(/earth,/string) , $
		/to_heliographic, $
		/to_sphere		, $
		/precess		, $
		degrees=degrees , $
		/onebody		, $
		/silent 		)

B0 = float(L0[1,*])			; Heliographic latitude
L0 = float(L0[0,*])			; Heliographic longitude

SyncDims, B0, sizeinfo=size(T)
SyncDims, L0, sizeinfo=size(T)

RETURN, B0  &  END