/* *+ * Name: * palPlanel * Purpose: * Transform conventional elements into position and velocity * Language: * Starlink ANSI C * Type of Module: * Library routine * Invocation: * void palPlanel ( double date, int jform, double epoch, double orbinc, * double anode, double perih, double aorq, double e, * double aorl, double dm, double pv[6], int *jstat ); * Arguments: * date = double (Given) * Epoch (TT MJD) of osculation (Note 1) * jform = int (Given) * Element set actually returned (1-3; Note 3) * epoch = double (Given) * Epoch of elements (TT MJD) (Note 4) * orbinc = double (Given) * inclination (radians) * anode = double (Given) * longitude of the ascending node (radians) * perih = double (Given) * longitude or argument of perihelion (radians) * aorq = double (Given) * mean distance or perihelion distance (AU) * e = double (Given) * eccentricity * aorl = double (Given) * mean anomaly or longitude (radians, JFORM=1,2 only) * dm = double (Given) * daily motion (radians, JFORM=1 only) * u = double [13] (Returned) * Universal orbital elements (Note 1) * (0) combined mass (M+m) * (1) total energy of the orbit (alpha) * (2) reference (osculating) epoch (t0) * (3-5) position at reference epoch (r0) * (6-8) velocity at reference epoch (v0) * (9) heliocentric distance at reference epoch * (10) r0.v0 * (11) date (t) * (12) universal eccentric anomaly (psi) of date, approx * jstat = int * (Returned) * status: 0 = OK * - -1 = illegal JFORM * - -2 = illegal E * - -3 = illegal AORQ * - -4 = illegal DM * - -5 = numerical error * Description: * Heliocentric position and velocity of a planet, asteroid or comet, * starting from orbital elements. * Authors: * PTW: Pat Wallace (STFC) * TIMJ: Tim Jenness (JAC, Hawaii) * {enter_new_authors_here} * Notes: * - 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). * - The elements are with respect to the J2000 ecliptic and equinox. * - 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. * - 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 palPertel may be used to update * the element-set (and its associated osculating epoch) by * applying planetary perturbations. * - The reference frame for the result is with respect to the mean * equator and equinox of epoch J2000. * - The algorithm was originally adapted from the EPHSLA program of * D.H.P.Jones (private communication, 1996). The method is based * on Stumpff's Universal Variables. * See Also: * Everhart, E. & Pitkin, E.T., Am.J.Phys. 51, 712, 1983. * History: * 2012-03-12 (TIMJ): * Initial version taken directly from SLA/F. * Adapted with permission from the Fortran SLALIB library. * {enter_further_changes_here} * Copyright: * Copyright (C) 2002 Rutherford Appleton Laboratory * Copyright (C) 2012 Science and Technology Facilities Council. * All Rights Reserved. * Licence: * 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 3 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; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, * MA 02110-1301, USA. * Bugs: * {note_any_bugs_here} *- */ #include "pal.h" void palPlanel ( double date, int jform, double epoch, double orbinc, double anode, double perih, double aorq, double e, double aorl, double dm, double pv[6], int *jstat ) { int j; double u[13]; /* Validate elements and convert to "universal variables" parameters. */ palEl2ue( date, jform, epoch, orbinc, anode, perih, aorq, e, aorl, dm, u, &j ); /* Determine the position and velocity */ if (j == 0) { palUe2pv( date, u, pv, &j); if (j != 0) j = -5; } /* Wrap up */ *jstat = j; }