source: branches/FACT++_lidctrl_usb/pal/palPlanel.c@ 18728

Last change on this file since 18728 was 18347, checked in by tbretz, 10 years ago
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1/*
2*+
3* Name:
4* palPlanel
5
6* Purpose:
7* Transform conventional elements into position and velocity
8
9* Language:
10* Starlink ANSI C
11
12* Type of Module:
13* Library routine
14
15* Invocation:
16* void palPlanel ( double date, int jform, double epoch, double orbinc,
17* double anode, double perih, double aorq, double e,
18* double aorl, double dm, double pv[6], int *jstat );
19
20* Arguments:
21* date = double (Given)
22* Epoch (TT MJD) of osculation (Note 1)
23* jform = int (Given)
24* Element set actually returned (1-3; Note 3)
25* epoch = double (Given)
26* Epoch of elements (TT MJD) (Note 4)
27* orbinc = double (Given)
28* inclination (radians)
29* anode = double (Given)
30* longitude of the ascending node (radians)
31* perih = double (Given)
32* longitude or argument of perihelion (radians)
33* aorq = double (Given)
34* mean distance or perihelion distance (AU)
35* e = double (Given)
36* eccentricity
37* aorl = double (Given)
38* mean anomaly or longitude (radians, JFORM=1,2 only)
39* dm = double (Given)
40* daily motion (radians, JFORM=1 only)
41* u = double [13] (Returned)
42* Universal orbital elements (Note 1)
43* (0) combined mass (M+m)
44* (1) total energy of the orbit (alpha)
45* (2) reference (osculating) epoch (t0)
46* (3-5) position at reference epoch (r0)
47* (6-8) velocity at reference epoch (v0)
48* (9) heliocentric distance at reference epoch
49* (10) r0.v0
50* (11) date (t)
51* (12) universal eccentric anomaly (psi) of date, approx
52* jstat = int * (Returned)
53* status: 0 = OK
54* - -1 = illegal JFORM
55* - -2 = illegal E
56* - -3 = illegal AORQ
57* - -4 = illegal DM
58* - -5 = numerical error
59
60* Description:
61* Heliocentric position and velocity of a planet, asteroid or comet,
62* starting from orbital elements.
63
64* Authors:
65* PTW: Pat Wallace (STFC)
66* TIMJ: Tim Jenness (JAC, Hawaii)
67* {enter_new_authors_here}
68
69* Notes:
70* - DATE is the instant for which the prediction is required. It is
71* in the TT timescale (formerly Ephemeris Time, ET) and is a
72* Modified Julian Date (JD-2400000.5).
73* - The elements are with respect to the J2000 ecliptic and equinox.
74* - A choice of three different element-set options is available:
75*
76* Option JFORM = 1, suitable for the major planets:
77*
78* EPOCH = epoch of elements (TT MJD)
79* ORBINC = inclination i (radians)
80* ANODE = longitude of the ascending node, big omega (radians)
81* PERIH = longitude of perihelion, curly pi (radians)
82* AORQ = mean distance, a (AU)
83* E = eccentricity, e (range 0 to <1)
84* AORL = mean longitude L (radians)
85* DM = daily motion (radians)
86*
87* Option JFORM = 2, suitable for minor planets:
88*
89* EPOCH = epoch of elements (TT MJD)
90* ORBINC = inclination i (radians)
91* ANODE = longitude of the ascending node, big omega (radians)
92* PERIH = argument of perihelion, little omega (radians)
93* AORQ = mean distance, a (AU)
94* E = eccentricity, e (range 0 to <1)
95* AORL = mean anomaly M (radians)
96*
97* Option JFORM = 3, suitable for comets:
98*
99* EPOCH = epoch of elements and perihelion (TT MJD)
100* ORBINC = inclination i (radians)
101* ANODE = longitude of the ascending node, big omega (radians)
102* PERIH = argument of perihelion, little omega (radians)
103* AORQ = perihelion distance, q (AU)
104* E = eccentricity, e (range 0 to 10)
105*
106* Unused arguments (DM for JFORM=2, AORL and DM for JFORM=3) are not
107* accessed.
108* - Each of the three element sets defines an unperturbed heliocentric
109* orbit. For a given epoch of observation, the position of the body
110* in its orbit can be predicted from these elements, which are
111* called "osculating elements", using standard two-body analytical
112* solutions. However, due to planetary perturbations, a given set
113* of osculating elements remains usable for only as long as the
114* unperturbed orbit that it describes is an adequate approximation
115* to reality. Attached to such a set of elements is a date called
116* the "osculating epoch", at which the elements are, momentarily,
117* a perfect representation of the instantaneous position and
118* velocity of the body.
119*
120* Therefore, for any given problem there are up to three different
121* epochs in play, and it is vital to distinguish clearly between
122* them:
123*
124* . The epoch of observation: the moment in time for which the
125* position of the body is to be predicted.
126*
127* . The epoch defining the position of the body: the moment in time
128* at which, in the absence of purturbations, the specified
129* position (mean longitude, mean anomaly, or perihelion) is
130* reached.
131*
132* . The osculating epoch: the moment in time at which the given
133* elements are correct.
134*
135* For the major-planet and minor-planet cases it is usual to make
136* the epoch that defines the position of the body the same as the
137* epoch of osculation. Thus, only two different epochs are
138* involved: the epoch of the elements and the epoch of observation.
139*
140* For comets, the epoch of perihelion fixes the position in the
141* orbit and in general a different epoch of osculation will be
142* chosen. Thus, all three types of epoch are involved.
143*
144* For the present routine:
145*
146* . The epoch of observation is the argument DATE.
147*
148* . The epoch defining the position of the body is the argument
149* EPOCH.
150*
151* . The osculating epoch is not used and is assumed to be close
152* enough to the epoch of observation to deliver adequate accuracy.
153* If not, a preliminary call to palPertel may be used to update
154* the element-set (and its associated osculating epoch) by
155* applying planetary perturbations.
156* - The reference frame for the result is with respect to the mean
157* equator and equinox of epoch J2000.
158* - The algorithm was originally adapted from the EPHSLA program of
159* D.H.P.Jones (private communication, 1996). The method is based
160* on Stumpff's Universal Variables.
161
162* See Also:
163* Everhart, E. & Pitkin, E.T., Am.J.Phys. 51, 712, 1983.
164
165* History:
166* 2012-03-12 (TIMJ):
167* Initial version taken directly from SLA/F.
168* Adapted with permission from the Fortran SLALIB library.
169* {enter_further_changes_here}
170
171* Copyright:
172* Copyright (C) 2002 Rutherford Appleton Laboratory
173* Copyright (C) 2012 Science and Technology Facilities Council.
174* All Rights Reserved.
175
176* Licence:
177* This program is free software; you can redistribute it and/or
178* modify it under the terms of the GNU General Public License as
179* published by the Free Software Foundation; either version 3 of
180* the License, or (at your option) any later version.
181*
182* This program is distributed in the hope that it will be
183* useful, but WITHOUT ANY WARRANTY; without even the implied
184* warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
185* PURPOSE. See the GNU General Public License for more details.
186*
187* You should have received a copy of the GNU General Public License
188* along with this program; if not, write to the Free Software
189* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
190* MA 02110-1301, USA.
191
192* Bugs:
193* {note_any_bugs_here}
194*-
195*/
196
197#include "pal.h"
198
199
200void palPlanel ( double date, int jform, double epoch, double orbinc,
201 double anode, double perih, double aorq, double e,
202 double aorl, double dm, double pv[6], int *jstat ) {
203
204 int j;
205 double u[13];
206
207 /* Validate elements and convert to "universal variables" parameters. */
208 palEl2ue( date, jform, epoch, orbinc, anode, perih, aorq, e, aorl,
209 dm, u, &j );
210
211 /* Determine the position and velocity */
212 if (j == 0) {
213 palUe2pv( date, u, pv, &j);
214 if (j != 0) j = -5;
215 }
216
217 /* Wrap up */
218 *jstat = j;
219
220}
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