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SUBROUTINE sla_PLANTE (DATE, ELONG, PHI, JFORM, EPOCH,
: ORBINC, ANODE, PERIH, AORQ, E,
: AORL, DM, RA, DEC, R, JSTAT)
*+
* - - - - - - -
* P L A N T E
* - - - - - - -
*
* Topocentric apparent RA,Dec of a Solar-System object whose
* heliocentric orbital elements are known.
*
* Given:
* DATE d MJD of observation (JD - 2400000.5, Notes 1,5)
* ELONG d observer's east longitude (radians, Note 2)
* PHI d observer's geodetic latitude (radians, Note 2)
* JFORM i choice of element set (1-3; Notes 3-6)
* EPOCH d epoch of elements (TT MJD, Note 5)
* ORBINC d inclination (radians)
* ANODE d longitude of the ascending node (radians)
* PERIH d longitude or argument of perihelion (radians)
* AORQ d mean distance or perihelion distance (AU)
* E d eccentricity
* AORL d mean anomaly or longitude (radians, JFORM=1,2 only)
* DM d daily motion (radians, JFORM=1 only )
*
* Returned:
* RA,DEC d RA, Dec (topocentric apparent, radians)
* R d distance from observer (AU)
* JSTAT i status: 0 = OK
* -1 = illegal JFORM
* -2 = illegal E
* -3 = illegal AORQ
* -4 = illegal DM
* -5 = numerical error
*
* Called: sla_EL2UE, sla_PLANTU
*
* Notes:
*
* 1 DATE is the instant for which the prediction is required. It is
* in the TT timescale (formerly Ephemeris Time, ET) and is a
* Modified Julian Date (JD-2400000.5).
*
* 2 The longitude and latitude allow correction for geocentric
* parallax. This is usually a small effect, but can become
* important for near-Earth asteroids. Geocentric positions can be
* generated by appropriate use of routines sla_EVP (or sla_EPV) and
* sla_PLANEL.
*
* 3 The elements are with respect to the J2000 ecliptic and equinox.
*
* 4 A choice of three different element-set options is available:
*
* Option JFORM = 1, suitable for the major planets:
*
* EPOCH = epoch of elements (TT MJD)
* ORBINC = inclination i (radians)
* ANODE = longitude of the ascending node, big omega (radians)
* PERIH = longitude of perihelion, curly pi (radians)
* AORQ = mean distance, a (AU)
* E = eccentricity, e (range 0 to <1)
* AORL = mean longitude L (radians)
* DM = daily motion (radians)
*
* Option JFORM = 2, suitable for minor planets:
*
* EPOCH = epoch of elements (TT MJD)
* ORBINC = inclination i (radians)
* ANODE = longitude of the ascending node, big omega (radians)
* PERIH = argument of perihelion, little omega (radians)
* AORQ = mean distance, a (AU)
* E = eccentricity, e (range 0 to <1)
* AORL = mean anomaly M (radians)
*
* Option JFORM = 3, suitable for comets:
*
* EPOCH = epoch of elements and perihelion (TT MJD)
* ORBINC = inclination i (radians)
* ANODE = longitude of the ascending node, big omega (radians)
* PERIH = argument of perihelion, little omega (radians)
* AORQ = perihelion distance, q (AU)
* E = eccentricity, e (range 0 to 10)
*
* Unused arguments (DM for JFORM=2, AORL and DM for JFORM=3) are not
* accessed.
*
* 5 Each of the three element sets defines an unperturbed heliocentric
* orbit. For a given epoch of observation, the position of the body
* in its orbit can be predicted from these elements, which are
* called "osculating elements", using standard two-body analytical
* solutions. However, due to planetary perturbations, a given set
* of osculating elements remains usable for only as long as the
* unperturbed orbit that it describes is an adequate approximation
* to reality. Attached to such a set of elements is a date called
* the "osculating epoch", at which the elements are, momentarily,
* a perfect representation of the instantaneous position and
* velocity of the body.
*
* Therefore, for any given problem there are up to three different
* epochs in play, and it is vital to distinguish clearly between
* them:
*
* . The epoch of observation: the moment in time for which the
* position of the body is to be predicted.
*
* . The epoch defining the position of the body: the moment in time
* at which, in the absence of purturbations, the specified
* position (mean longitude, mean anomaly, or perihelion) is
* reached.
*
* . The osculating epoch: the moment in time at which the given
* elements are correct.
*
* For the major-planet and minor-planet cases it is usual to make
* the epoch that defines the position of the body the same as the
* epoch of osculation. Thus, only two different epochs are
* involved: the epoch of the elements and the epoch of observation.
*
* For comets, the epoch of perihelion fixes the position in the
* orbit and in general a different epoch of osculation will be
* chosen. Thus, all three types of epoch are involved.
*
* For the present routine:
*
* . The epoch of observation is the argument DATE.
*
* . The epoch defining the position of the body is the argument
* EPOCH.
*
* . The osculating epoch is not used and is assumed to be close
* enough to the epoch of observation to deliver adequate accuracy.
* If not, a preliminary call to sla_PERTEL may be used to update
* the element-set (and its associated osculating epoch) by
* applying planetary perturbations.
*
* 6 Two important sources for orbital elements are Horizons, operated
* by the Jet Propulsion Laboratory, Pasadena, and the Minor Planet
* Center, operated by the Center for Astrophysics, Harvard.
*
* The JPL Horizons elements (heliocentric, J2000 ecliptic and
* equinox) correspond to SLALIB arguments as follows.
*
* Major planets:
*
* JFORM = 1
* EPOCH = JDCT-2400000.5D0
* ORBINC = IN (in radians)
* ANODE = OM (in radians)
* PERIH = OM+W (in radians)
* AORQ = A
* E = EC
* AORL = MA+OM+W (in radians)
* DM = N (in radians)
*
* Epoch of osculation = JDCT-2400000.5D0
*
* Minor planets:
*
* JFORM = 2
* EPOCH = JDCT-2400000.5D0
* ORBINC = IN (in radians)
* ANODE = OM (in radians)
* PERIH = W (in radians)
* AORQ = A
* E = EC
* AORL = MA (in radians)
*
* Epoch of osculation = JDCT-2400000.5D0
*
* Comets:
*
* JFORM = 3
* EPOCH = Tp-2400000.5D0
* ORBINC = IN (in radians)
* ANODE = OM (in radians)
* PERIH = W (in radians)
* AORQ = QR
* E = EC
*
* Epoch of osculation = JDCT-2400000.5D0
*
* The MPC elements correspond to SLALIB arguments as follows.
*
* Minor planets:
*
* JFORM = 2
* EPOCH = Epoch-2400000.5D0
* ORBINC = Incl. (in radians)
* ANODE = Node (in radians)
* PERIH = Perih. (in radians)
* AORQ = a
* E = e
* AORL = M (in radians)
*
* Epoch of osculation = Epoch-2400000.5D0
*
* Comets:
*
* JFORM = 3
* EPOCH = T-2400000.5D0
* ORBINC = Incl. (in radians)
* ANODE = Node. (in radians)
* PERIH = Perih. (in radians)
* AORQ = q
* E = e
*
* Epoch of osculation = Epoch-2400000.5D0
*
* This revision: 19 June 2004
*
* Copyright (C) 2004 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
DOUBLE PRECISION DATE,ELONG,PHI
INTEGER JFORM
DOUBLE PRECISION EPOCH,ORBINC,ANODE,PERIH,AORQ,E,
: AORL,DM,RA,DEC,R
INTEGER JSTAT
DOUBLE PRECISION U(13)
* Transform conventional elements to universal elements.
CALL sla_EL2UE(DATE,
: JFORM,EPOCH,ORBINC,ANODE,PERIH,AORQ,E,AORL,DM,
: U,JSTAT)
* If successful, make the prediction.
IF (JSTAT.EQ.0) CALL sla_PLANTU(DATE,ELONG,PHI,U,RA,DEC,R,JSTAT)
END