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SUBROUTINE sla_ECOR (RM, DM, IY, ID, FD, RV, TL)
*+
* - - - - -
* E C O R
* - - - - -
*
* Component of Earth orbit velocity and heliocentric
* light time in a given direction (single precision)
*
* Given:
* RM,DM real mean RA, Dec of date (radians)
* IY int year
* ID int day in year (1 = Jan 1st)
* FD real fraction of day
*
* Returned:
* RV real component of Earth orbital velocity (km/sec)
* TL real component of heliocentric light time (sec)
*
* Notes:
*
* 1 The date and time is TDB (loosely ET) in a Julian calendar
* which has been aligned to the ordinary Gregorian
* calendar for the interval 1900 March 1 to 2100 February 28.
* The year and day can be obtained by calling sla_CALYD or
* sla_CLYD.
*
* 2 Sign convention:
*
* The velocity component is +ve when the Earth is receding from
* the given point on the sky. The light time component is +ve
* when the Earth lies between the Sun and the given point on
* the sky.
*
* 3 Accuracy:
*
* The velocity component is usually within 0.004 km/s of the
* correct value and is never in error by more than 0.007 km/s.
* The error in light time correction is about 0.03s at worst,
* but is usually better than 0.01s. For applications requiring
* higher accuracy, see the sla_EVP and sla_EPV routines.
*
* Called: sla_EARTH, sla_CS2C, sla_VDV
*
* Last revision: 5 April 2005
*
* Copyright P.T.Wallace. All rights reserved.
*
* License:
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program (see SLA_CONDITIONS); if not, write to the
* Free Software Foundation, Inc., 59 Temple Place, Suite 330,
* Boston, MA 02111-1307 USA
*
*-
IMPLICIT NONE
REAL RM,DM
INTEGER IY,ID
REAL FD,RV,TL
REAL sla_VDV
REAL PV(6),V(3),AUKM,AUSEC
* AU to km and light sec (1985 Almanac)
PARAMETER (AUKM=1.4959787066E8,
: AUSEC=499.0047837)
* Sun:Earth position & velocity vector
CALL sla_EARTH(IY,ID,FD,PV)
* Star position vector
CALL sla_CS2C(RM,DM,V)
* Velocity component
RV=-AUKM*sla_VDV(PV(4),V)
* Light time component
TL=AUSEC*sla_VDV(PV(1),V)
END