source: trunk/MagicSoft/slalib/pertel.c

Last change on this file was 731, checked in by tbretz, 24 years ago
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1#include "slalib.h"
2#include "slamac.h"
3void slaPertel (int jform, double date0, double date1,
4 double epoch0, double orbi0, double anode0,
5 double perih0, double aorq0, double e0, double am0,
6 double *epoch1, double *orbi1, double *anode1,
7 double *perih1, double *aorq1, double *e1, double *am1,
8 int *jstat )
9/*
10** - - - - - - - - - -
11** s l a P e r t e l
12** - - - - - - - - - -
13**
14** Update the osculating orbital elements of an asteroid or comet by
15** applying planetary perturbations.
16**
17** Given (format and dates):
18** jform int choice of element set (2 or 3; Note 1)
19** date0 double date of osculation (TT MJD) for the given elements
20** date1 double date of osculation (TT MJD) for the updated elements
21**
22** Given (the unperturbed elements):
23** epoch0 double epoch (TT MJD) of the given element set (Note 2)
24** orbi0 double inclination (radians)
25** anode0 double longitude of the ascending node (radians)
26** perih0 double argument of perihelion (radians)
27** aorq0 double mean distance or perihelion distance (AU)
28** e0 double eccentricity
29** am0 double mean anomaly (radians, jform=2 only)
30**
31** Returned (the updated elements):
32** epoch1 double* epoch (TT MJD) of the updated element set (Note 2)
33** orbi1 double* inclination (radians)
34** anode1 double* longitude of the ascending node (radians)
35** perih1 double* argument of perihelion (radians)
36** aorq1 double* mean distance or perihelion distance (AU)
37** e1 double* eccentricity
38** am1 double* mean anomaly (radians, jform=2 only)
39**
40** Returned (status flag):
41** jstat int* status: +102 = warning, distant epoch
42** +101 = warning, large timespan ( > 100 years)
43** +1 to +8 = coincident with major planet (Note 6)
44** 0 = OK
45** -1 = illegal jform
46** -2 = illegal e0
47** -3 = illegal aorq0
48** -4 = internal error
49** -5 = numerical error
50**
51** Notes:
52**
53** 1 Two different element-format options are available:
54**
55** Option jform=2, suitable for minor planets:
56**
57** epoch = epoch of elements (TT MJD)
58** orbi = inclination i (radians)
59** anode = longitude of the ascending node, big omega (radians)
60** perih = argument of perihelion, little omega (radians)
61** aorq = mean distance, a (AU)
62** e = eccentricity, e
63** am = mean anomaly M (radians)
64**
65** Option jform=3, suitable for comets:
66**
67** epoch = epoch of perihelion (TT MJD)
68** orbi = inclination i (radians)
69** anode = longitude of the ascending node, big omega (radians)
70** perih = argument of perihelion, little omega (radians)
71** aorq = perihelion distance, q (AU)
72** e = eccentricity, e
73**
74** 2 date0, date1, epoch0 and epoch1 are all instants of time in
75** the TT timescale (formerly Ephemeris Time, ET), expressed
76** as Modified Julian Dates (JD-2400000.5).
77**
78** date0 is the instant at which the given (i.e. unperturbed)
79** osculating elements are correct.
80**
81** date1 is the specified instant at which the updated osculating
82** elements are correct.
83**
84** epoch0 and epoch1 will be the same as date0 and date1
85** (respectively) for the jform=2 case, normally used for minor
86** planets. For the jform=3 case, the two epochs will refer to
87** perihelion passage and so will not, in general, be the same as
88** date0 and/or date1 though they may be similar to one another.
89**
90** 3 The elements are with respect to the J2000 ecliptic and equinox.
91**
92** 4 Unused elements (am0 and am1 for jform=3) are not accessed.
93**
94** 5 See the slaPertue routine for details of the algorithm used.
95**
96** 6 This routine is not intended to be used for major planets, which
97** is why jform=1 is not available and why there is no opportunity
98** to specify either the longitude of perihelion or the daily
99** motion. However, if jform=2 elements are somehow obtained for a
100** major planet and supplied to the routine, sensible results will,
101** in fact, be produced. This happens because the slaPertue routine
102** that is called to perform the calculations checks the separation
103** between the body and each of the planets and interprets a
104** suspiciously small value (1E-3 AU) as an attempt to apply it to
105** the planet concerned. If this condition is detected, the
106** contribution from that planet is ignored, and the status is set to
107** the planet number (Mercury=1,...,Neptune=8) as a warning.
108**
109** Reference:
110**
111** Sterne, Theodore E., "An Introduction to Celestial Mechanics",
112** Interscience Publishers Inc., 1960. Section 6.7, p199.
113**
114** Called: slaEl2ue, slaPertue, slaUe2el
115**
116** Last revision: 14 March 1999
117**
118** Copyright 1999 P.T.Wallace. All rights reserved.
119*/
120{
121 double u[13], dm;
122 int j, jf;
123
124
125/* Check that the elements are either minor-planet or comet format. */
126 if ( jform < 2 || jform > 3 ) {
127 *jstat = -1;
128 return;
129 }
130
131/* Transform the elements from conventional to universal form. */
132 slaEl2ue ( date0, jform, epoch0, orbi0, anode0, perih0,
133 aorq0, e0, am0, 0.0, u, &j );
134 if ( j ) {
135 *jstat = j;
136 return;
137 }
138
139/* Update the universal elements. */
140 slaPertue ( date1, u, &j );
141 if ( j > 0 ) {
142 *jstat = j;
143 } else if ( j < 0 ) {
144 *jstat = -5;
145 return;
146 }
147
148/* Transform from universal to conventional elements. */
149 slaUe2el ( u, 2,
150 &jf, epoch1, orbi1, anode1, perih1, aorq1, e1, am1, &dm, &j );
151 if ( jf != jform || j ) *jstat = -5;
152
153}
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