SimGear: saturn.cxx Source File

00001 /**************************************************************************
00002  * saturn.cxx
00003  * Written by Durk Talsma. Originally started October 1997, for distribution  
00004  * with the FlightGear project. Version 2 was written in August and 
00005  * September 1998. This code is based upon algorithms and data kindly 
00006  * provided by Mr. Paul Schlyter. (pausch@saaf.se). 
00007  *
00008  * This library is free software; you can redistribute it and/or
00009  * modify it under the terms of the GNU Library General Public
00010  * License as published by the Free Software Foundation; either
00011  * version 2 of the License, or (at your option) any later version.
00012  *
00013  * This library is distributed in the hope that it will be useful,
00014  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00015  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00016  * Library General Public License for more details.
00017  *
00018  * You should have received a copy of the GNU General Public License
00019  * along with this program; if not, write to the Free Software
00020  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
00021  *
00022  * $Id: saturn_8cxx_source.html,v 1.3 2010/02/23 22:10:16 curt Exp $
00023  **************************************************************************/
00024 
00025 #include <math.h>
00026 
00027 #include "saturn.hxx"
00028 
00029 /*************************************************************************
00030  * Saturn::Saturn(double mjd)
00031  * Public constructor for class Saturn
00032  * Argument: The current time.
00033  * the hard coded orbital elements for Saturn are passed to 
00034  * CelestialBody::CelestialBody();
00035  ************************************************************************/
00036 Saturn::Saturn(double mjd) :
00037   CelestialBody(113.6634,   2.3898000E-5,
00038                 2.4886,    -1.081E-7,
00039                 339.3939,   2.9766100E-5,
00040                 9.5547500,  0.000000,
00041                 0.055546,  -9.499E-9,
00042                 316.9670,   0.03344422820, mjd)
00043 {
00044 }
00045 Saturn::Saturn() :
00046   CelestialBody(113.6634,   2.3898000E-5,
00047                 2.4886,    -1.081E-7,
00048                 339.3939,   2.9766100E-5,
00049                 9.5547500,  0.000000,
00050                 0.055546,  -9.499E-9,
00051                 316.9670,   0.03344422820)
00052 {
00053 }
00054 
00055 /*************************************************************************
00056  * void Saturn::updatePosition(double mjd, Star *ourSun)
00057  * 
00058  * calculates the current position of Saturn, by calling the base class,
00059  * CelestialBody::updatePosition(); The current magnitude is calculated using 
00060  * a Saturn specific equation
00061  *************************************************************************/
00062 void Saturn::updatePosition(double mjd, Star *ourSun)
00063 {
00064   CelestialBody::updatePosition(mjd, ourSun);
00065   
00066   double actTime = sgCalcActTime(mjd);
00067   double ir = 0.4897394;
00068   double Nr = 2.9585076 + 6.6672E-7*actTime;
00069   double B = asin (sin(declination) * cos(ir) - 
00070                    cos(declination) * sin(ir) *
00071                    sin(rightAscension - Nr));
00072   double ring_magn = -2.6 * sin(fabs(B)) + 1.2 * pow(sin(B), 2);
00073   magnitude = -9.0 + 5*log10(r*R) + 0.044 * FV + ring_magn;
00074 }
00075