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182 lines
6.7 KiB
Fortran
182 lines
6.7 KiB
Fortran
SUBROUTINE sla_PERTEL (JFORM, DATE0, DATE1,
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: EPOCH0, ORBI0, ANODE0, PERIH0, AORQ0, E0, AM0,
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: EPOCH1, ORBI1, ANODE1, PERIH1, AORQ1, E1, AM1,
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: JSTAT)
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*+
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* - - - - - - -
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* P E R T E L
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* - - - - - - -
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*
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* Update the osculating orbital elements of an asteroid or comet by
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* applying planetary perturbations.
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*
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* Given (format and dates):
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* JFORM i choice of element set (2 or 3; Note 1)
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* DATE0 d date of osculation (TT MJD) for the given elements
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* DATE1 d date of osculation (TT MJD) for the updated elements
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*
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* Given (the unperturbed elements):
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* EPOCH0 d epoch (TT MJD) of the given element set (Note 2)
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* ORBI0 d inclination (radians)
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* ANODE0 d longitude of the ascending node (radians)
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* PERIH0 d argument of perihelion (radians)
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* AORQ0 d mean distance or perihelion distance (AU)
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* E0 d eccentricity
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* AM0 d mean anomaly (radians, JFORM=2 only)
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*
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* Returned (the updated elements):
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* EPOCH1 d epoch (TT MJD) of the updated element set (Note 2)
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* ORBI1 d inclination (radians)
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* ANODE1 d longitude of the ascending node (radians)
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* PERIH1 d argument of perihelion (radians)
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* AORQ1 d mean distance or perihelion distance (AU)
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* E1 d eccentricity
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* AM1 d mean anomaly (radians, JFORM=2 only)
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*
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* Returned (status flag):
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* JSTAT i status: +102 = warning, distant epoch
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* +101 = warning, large timespan ( > 100 years)
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* +1 to +10 = coincident with planet (Note 6)
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* 0 = OK
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* -1 = illegal JFORM
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* -2 = illegal E0
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* -3 = illegal AORQ0
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* -4 = internal error
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* -5 = numerical error
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*
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* Notes:
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*
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* 1 Two different element-format options are available:
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*
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* Option JFORM=2, suitable for minor planets:
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*
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* EPOCH = epoch of elements (TT MJD)
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* ORBI = inclination i (radians)
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* ANODE = longitude of the ascending node, big omega (radians)
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* PERIH = argument of perihelion, little omega (radians)
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* AORQ = mean distance, a (AU)
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* E = eccentricity, e
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* AM = mean anomaly M (radians)
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*
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* Option JFORM=3, suitable for comets:
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*
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* EPOCH = epoch of perihelion (TT MJD)
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* ORBI = inclination i (radians)
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* ANODE = longitude of the ascending node, big omega (radians)
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* PERIH = argument of perihelion, little omega (radians)
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* AORQ = perihelion distance, q (AU)
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* E = eccentricity, e
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*
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* 2 DATE0, DATE1, EPOCH0 and EPOCH1 are all instants of time in
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* the TT timescale (formerly Ephemeris Time, ET), expressed
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* as Modified Julian Dates (JD-2400000.5).
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*
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* DATE0 is the instant at which the given (i.e. unperturbed)
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* osculating elements are correct.
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*
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* DATE1 is the specified instant at which the updated osculating
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* elements are correct.
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*
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* EPOCH0 and EPOCH1 will be the same as DATE0 and DATE1
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* (respectively) for the JFORM=2 case, normally used for minor
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* planets. For the JFORM=3 case, the two epochs will refer to
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* perihelion passage and so will not, in general, be the same as
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* DATE0 and/or DATE1 though they may be similar to one another.
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*
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* 3 The elements are with respect to the J2000 ecliptic and equinox.
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*
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* 4 Unused elements (AM0 and AM1 for JFORM=3) are not accessed.
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*
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* 5 See the sla_PERTUE routine for details of the algorithm used.
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*
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* 6 This routine is not intended to be used for major planets, which
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* is why JFORM=1 is not available and why there is no opportunity
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* to specify either the longitude of perihelion or the daily
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* motion. However, if JFORM=2 elements are somehow obtained for a
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* major planet and supplied to the routine, sensible results will,
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* in fact, be produced. This happens because the sla_PERTUE routine
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* that is called to perform the calculations checks the separation
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* between the body and each of the planets and interprets a
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* suspiciously small value (0.001 AU) as an attempt to apply it to
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* the planet concerned. If this condition is detected, the
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* contribution from that planet is ignored, and the status is set to
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* the planet number (1-10 = Mercury, Venus, EMB, Mars, Jupiter,
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* Saturn, Uranus, Neptune, Earth, Moon) as a warning.
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*
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* Reference:
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*
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* Sterne, Theodore E., "An Introduction to Celestial Mechanics",
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* Interscience Publishers Inc., 1960. Section 6.7, p199.
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*
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* Called: sla_EL2UE, sla_PERTUE, sla_UE2EL
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*
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* This revision: 19 June 2004
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*
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* Copyright (C) 2004 P.T.Wallace. All rights reserved.
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*
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* License:
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program (see SLA_CONDITIONS); if not, write to the
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* Free Software Foundation, Inc., 59 Temple Place, Suite 330,
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* Boston, MA 02111-1307 USA
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*
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*-
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IMPLICIT NONE
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INTEGER JFORM
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DOUBLE PRECISION DATE0,DATE1,
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: EPOCH0,ORBI0,ANODE0,PERIH0,AORQ0,E0,AM0,
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: EPOCH1,ORBI1,ANODE1,PERIH1,AORQ1,E1,AM1
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INTEGER JSTAT
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DOUBLE PRECISION U(13),DM
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INTEGER J,JF
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* Check that the elements are either minor-planet or comet format.
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IF (JFORM.LT.2.OR.JFORM.GT.3) THEN
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JSTAT = -1
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GO TO 9999
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ELSE
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* Provisionally set the status to OK.
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JSTAT = 0
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END IF
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* Transform the elements from conventional to universal form.
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CALL sla_EL2UE(DATE0,JFORM,EPOCH0,ORBI0,ANODE0,PERIH0,
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: AORQ0,E0,AM0,0D0,U,J)
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IF (J.NE.0) THEN
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JSTAT = J
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GO TO 9999
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END IF
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* Update the universal elements.
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CALL sla_PERTUE(DATE1,U,J)
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IF (J.GT.0) THEN
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JSTAT = J
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ELSE IF (J.LT.0) THEN
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JSTAT = -5
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GO TO 9999
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END IF
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* Transform from universal to conventional elements.
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CALL sla_UE2EL(U,JFORM,
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: JF, EPOCH1, ORBI1, ANODE1, PERIH1,
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: AORQ1, E1, AM1, DM, J)
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IF (JF.NE.JFORM.OR.J.NE.0) JSTAT=-5
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9999 CONTINUE
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END
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