185 lines
6.4 KiB
C++
185 lines
6.4 KiB
C++
/**************************************************************************
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* celestialBody.hxx
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* Written by Durk Talsma. Originally started October 1997, for distribution
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* with the FlightGear project. Version 2 was written in August and
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* September 1998. This code is based upon algorithms and data kindly
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* provided by Mr. Paul Schlyter. (pausch@saaf.se).
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 2 of the
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* License, or (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, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* 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; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*
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* $Id$
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* (Log is kept at end of this file)
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**************************************************************************/
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#ifndef _CELESTIALBODY_H_
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#define _CELESTIALBODY_H_
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#ifndef __cplusplus
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# error This library requires C++
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#endif
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#include <Time/fg_time.hxx>
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#include <Include/fg_constants.h>
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class Star;
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class CelestialBody
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{
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protected: // make the data protected, in order to give the inherited
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// classes direct access to the data
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double NFirst; /* longitude of the ascending node first part */
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double NSec; /* longitude of the ascending node second part */
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double iFirst; /* inclination to the ecliptic first part */
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double iSec; /* inclination to the ecliptic second part */
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double wFirst; /* first part of argument of perihelion */
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double wSec; /* second part of argument of perihelion */
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double aFirst; /* semimayor axis first part*/
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double aSec; /* semimayor axis second part */
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double eFirst; /* eccentricity first part */
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double eSec; /* eccentricity second part */
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double MFirst; /* Mean anomaly first part */
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double MSec; /* Mean anomaly second part */
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double N, i, w, a, e, M; /* the resulting orbital elements, obtained from the former */
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double rightAscension, declination;
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double r, R, s, FV;
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double magnitude;
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double fgCalcEccAnom(double M, double e);
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double fgCalcActTime(fgTIME *t);
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void updateOrbElements(fgTIME *t);
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public:
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CelestialBody(double Nf, double Ns,
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double If, double Is,
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double wf, double ws,
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double af, double as,
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double ef, double es,
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double Mf, double Ms, fgTIME *t);
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void getPos(double *ra, double *dec);
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void getPos(double *ra, double *dec, double *magnitude);
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void updatePosition(fgTIME *t, Star *ourSun);
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};
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/*****************************************************************************
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* inline CelestialBody::CelestialBody
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* public constructor for a generic celestialBody object.
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* initializes the 6 primary orbital elements. The elements are:
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* N: longitude of the ascending node
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* i: inclination to the ecliptic
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* w: argument of perihelion
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* a: semi-major axis, or mean distance from the sun
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* e: eccenticity
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* M: mean anomaly
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* Each orbital element consists of a constant part and a variable part that
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* gradually changes over time.
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*
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* Argumetns:
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* the 13 arguments to the constructor constitute the first, constant
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* ([NiwaeM]f) and the second variable ([NiwaeM]s) part of the orbital
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* elements. The 13th argument is the current time. Note that the inclination
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* is written with a capital (If, Is), because 'if' is a reserved word in the
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* C/C++ programming language.
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***************************************************************************/
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inline CelestialBody::CelestialBody(double Nf, double Ns,
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double If, double Is,
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double wf, double ws,
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double af, double as,
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double ef, double es,
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double Mf, double Ms, fgTIME *t)
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{
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NFirst = Nf; NSec = Ns;
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iFirst = If; iSec = Is;
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wFirst = wf; wSec = ws;
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aFirst = af; aSec = as;
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eFirst = ef; eSec = es;
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MFirst = Mf; MSec = Ms;
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updateOrbElements(t);
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};
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/****************************************************************************
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* inline void CelestialBody::updateOrbElements(fgTIME *t)
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* given the current time, this private member calculates the actual
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* orbital elements
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*
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* Arguments: fgTIME *t: the current time:
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*
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* return value: none
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***************************************************************************/
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inline void CelestialBody::updateOrbElements(fgTIME *t)
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{
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double actTime = fgCalcActTime(t);
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M = DEG_TO_RAD * (MFirst + (MSec * actTime));
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w = DEG_TO_RAD * (wFirst + (wSec * actTime));
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N = DEG_TO_RAD * (NFirst + (NSec * actTime));
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i = DEG_TO_RAD * (iFirst + (iSec * actTime));
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e = eFirst + (eSec * actTime);
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a = aFirst + (aSec * actTime);
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}
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/*****************************************************************************
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* inline double CelestialBody::fgCalcActTime(fgTIME *t)
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* this private member function returns the offset in days from the epoch for
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* wich the orbital elements are calculated (Jan, 1st, 2000).
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*
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* Argument: the current time
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*
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* return value: the (fractional) number of days until Jan 1, 2000.
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****************************************************************************/
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inline double CelestialBody::fgCalcActTime(fgTIME *t)
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{
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return (t->mjd - 36523.5);
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}
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/*****************************************************************************
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* inline void CelestialBody::getPos(double* ra, double* dec)
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* gives public access to Right Ascension and declination
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*
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****************************************************************************/
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inline void CelestialBody::getPos(double* ra, double* dec)
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{
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*ra = rightAscension;
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*dec = declination;
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}
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/*****************************************************************************
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* inline void CelestialBody::getPos(double* ra, double* dec, double* magnitude
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* gives public acces to the current Right ascension, declination, and
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* magnitude
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****************************************************************************/
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inline void CelestialBody::getPos(double* ra, double* dec, double* magn)
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{
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*ra = rightAscension;
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*dec = declination;
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*magn = magnitude;
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}
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#endif // _CELESTIALBODY_H_
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