1 /**************************************************************************
3 * Written by Durk Talsma. Originally started October 1997, for distribution
4 * with the FlightGear project. Version 2 was written in August and
5 * September 1998. This code is based upon algorithms and data kindly
6 * provided by Mr. Paul Schlyter. (pausch@saaf.se).
8 * This program is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU General Public License as
10 * published by the Free Software Foundation; either version 2 of the
11 * License, or (at your option) any later version.
13 * This program is distributed in the hope that it will be useful, but
14 * WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 * General Public License for more details.
18 * You should have received a copy of the GNU General Public License
19 * along with this program; if not, write to the Free Software
20 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
23 **************************************************************************/
26 #ifndef _CELESTIALBODY_H_
27 #define _CELESTIALBODY_H_
30 # error This library requires C++
34 #include <simgear/constants.h>
36 #include <Time/fg_time.hxx>
42 protected: // make the data protected, in order to give the inherited
43 // classes direct access to the data
44 double NFirst; /* longitude of the ascending node first part */
45 double NSec; /* longitude of the ascending node second part */
46 double iFirst; /* inclination to the ecliptic first part */
47 double iSec; /* inclination to the ecliptic second part */
48 double wFirst; /* first part of argument of perihelion */
49 double wSec; /* second part of argument of perihelion */
50 double aFirst; /* semimayor axis first part*/
51 double aSec; /* semimayor axis second part */
52 double eFirst; /* eccentricity first part */
53 double eSec; /* eccentricity second part */
54 double MFirst; /* Mean anomaly first part */
55 double MSec; /* Mean anomaly second part */
57 double N, i, w, a, e, M; /* the resulting orbital elements, obtained from the former */
59 double rightAscension, declination;
62 double lonEcl, latEcl;
64 double fgCalcEccAnom(double M, double e);
65 double fgCalcActTime(FGTime *t);
66 void updateOrbElements(FGTime *t);
69 CelestialBody(double Nf, double Ns,
74 double Mf, double Ms, FGTime *t);
75 void getPos(double *ra, double *dec);
76 void getPos(double *ra, double *dec, double *magnitude);
79 void updatePosition(FGTime *t, Star *ourSun);
82 /*****************************************************************************
83 * inline CelestialBody::CelestialBody
84 * public constructor for a generic celestialBody object.
85 * initializes the 6 primary orbital elements. The elements are:
86 * N: longitude of the ascending node
87 * i: inclination to the ecliptic
88 * w: argument of perihelion
89 * a: semi-major axis, or mean distance from the sun
92 * Each orbital element consists of a constant part and a variable part that
93 * gradually changes over time.
96 * the 13 arguments to the constructor constitute the first, constant
97 * ([NiwaeM]f) and the second variable ([NiwaeM]s) part of the orbital
98 * elements. The 13th argument is the current time. Note that the inclination
99 * is written with a capital (If, Is), because 'if' is a reserved word in the
100 * C/C++ programming language.
101 ***************************************************************************/
102 inline CelestialBody::CelestialBody(double Nf, double Ns,
103 double If, double Is,
104 double wf, double ws,
105 double af, double as,
106 double ef, double es,
107 double Mf, double Ms, FGTime *t)
109 NFirst = Nf; NSec = Ns;
110 iFirst = If; iSec = Is;
111 wFirst = wf; wSec = ws;
112 aFirst = af; aSec = as;
113 eFirst = ef; eSec = es;
114 MFirst = Mf; MSec = Ms;
115 updateOrbElements(t);
118 /****************************************************************************
119 * inline void CelestialBody::updateOrbElements(FGTime *t)
120 * given the current time, this private member calculates the actual
123 * Arguments: FGTime *t: the current time:
126 ***************************************************************************/
127 inline void CelestialBody::updateOrbElements(FGTime *t)
129 double actTime = fgCalcActTime(t);
130 M = DEG_TO_RAD * (MFirst + (MSec * actTime));
131 w = DEG_TO_RAD * (wFirst + (wSec * actTime));
132 N = DEG_TO_RAD * (NFirst + (NSec * actTime));
133 i = DEG_TO_RAD * (iFirst + (iSec * actTime));
134 e = eFirst + (eSec * actTime);
135 a = aFirst + (aSec * actTime);
137 /*****************************************************************************
138 * inline double CelestialBody::fgCalcActTime(FGTime *t)
139 * this private member function returns the offset in days from the epoch for
140 * wich the orbital elements are calculated (Jan, 1st, 2000).
142 * Argument: the current time
144 * return value: the (fractional) number of days until Jan 1, 2000.
145 ****************************************************************************/
146 inline double CelestialBody::fgCalcActTime(FGTime *t)
148 return (t->getMjd() - 36523.5);
151 /*****************************************************************************
152 * inline void CelestialBody::getPos(double* ra, double* dec)
153 * gives public access to Right Ascension and declination
155 ****************************************************************************/
156 inline void CelestialBody::getPos(double* ra, double* dec)
158 *ra = rightAscension;
162 /*****************************************************************************
163 * inline void CelestialBody::getPos(double* ra, double* dec, double* magnitude
164 * gives public acces to the current Right ascension, declination, and
166 ****************************************************************************/
167 inline void CelestialBody::getPos(double* ra, double* dec, double* magn)
169 *ra = rightAscension;
174 inline double CelestialBody::getLon()
179 inline double CelestialBody::getLat()
184 #endif // _CELESTIALBODY_H_