Satellite Observers Workbench. NOT yet complete, just published for forum posters to \"cherry pick\" pieces of code as requiered as an example.
solar.c
00001 /* 00002 * Unit Solar 00003 * Author: Dr TS Kelso 00004 * Original Version: 1990 Jul 29 00005 * Current Revision: 1999 Nov 27 00006 * Version: 1.30 00007 * Copyright: 1990-1999, All Rights Reserved 00008 * 00009 * Ported to C by: Neoklis Kyriazis April 1 2001 00010 */ 00011 00012 #include "sgp4sdp4.h" 00013 00014 /* Calculates solar position vector */ 00015 void 00016 Calculate_Solar_Position(double _time, vector_t *solar_vector) 00017 { 00018 double mjd,year,T,M,L,e,C,O,Lsa,nu,R,eps; 00019 00020 mjd = _time - 2415020.0; 00021 year = 1900 + mjd/365.25; 00022 T = (mjd + Delta_ET(year)/secday)/36525.0; 00023 M = Radians(Modulus(358.47583 + Modulus(35999.04975*T,360.0) 00024 - (0.000150 + 0.0000033*T)*Sqr(T),360.0)); 00025 L = Radians(Modulus(279.69668 + Modulus(36000.76892*T,360.0) 00026 + 0.0003025*Sqr(T),360.0)); 00027 e = 0.01675104 - (0.0000418 + 0.000000126*T)*T; 00028 C = Radians((1.919460 - (0.004789 + 0.000014*T)*T)*sin(M) 00029 + (0.020094 - 0.000100*T)*sin(2*M) + 0.000293*sin(3*M)); 00030 O = Radians(Modulus(259.18 - 1934.142*T,360.0)); 00031 Lsa = Modulus(L + C - Radians(0.00569 - 0.00479*sin(O)),twopi); 00032 nu = Modulus(M + C,twopi); 00033 R = 1.0000002*(1 - Sqr(e))/(1 + e*cos(nu)); 00034 eps = Radians(23.452294 - (0.0130125 + (0.00000164 - 00035 0.000000503*T)*T)*T + 0.00256*cos(O)); 00036 R = SGPAU*R; 00037 solar_vector->x = R*cos(Lsa); 00038 solar_vector->y = R*sin(Lsa)*cos(eps); 00039 solar_vector->z = R*sin(Lsa)*sin(eps); 00040 solar_vector->w = R; 00041 } /*Procedure Calculate_Solar_Position*/ 00042 00043 /*------------------------------------------------------------------*/ 00044 00045 /* Calculates stellite's eclipse status and depth */ 00046 int 00047 Sat_Eclipsed(vector_t *pos, vector_t *sol, double *depth) 00048 { 00049 double sd_sun, sd_earth, delta; 00050 vector_t Rho, earth; 00051 00052 /* Determine partial eclipse */ 00053 sd_earth = ArcSin(xkmper/pos->w); 00054 Vec_Sub(sol,pos,&Rho); 00055 sd_sun = ArcSin(__sr__/Rho.w); 00056 Scalar_Multiply(-1,pos,&earth); 00057 delta = Angle(sol,&earth); 00058 *depth = sd_earth - sd_sun - delta; 00059 if( sd_earth < sd_sun ) 00060 return( 0 ); 00061 else 00062 if( *depth >= 0 ) 00063 return( 1 ); 00064 else 00065 return( 0 ); 00066 00067 } /*Function Sat_Eclipsed*/ 00068 00069 /*------------------------------------------------------------------*/
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