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* Original Version: 1990 Jul 29
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* Current Revision: 1999 Nov 27
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* Copyright: 1990-1999, All Rights Reserved
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* Ported to C by: Neoklis Kyriazis April 1 2001
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/* Calculates solar position vector */
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Calculate_Solar_Position(double time, vector_t *solar_vector)
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double mjd,year,T,M,L,e,C,O,Lsa,nu,R,eps;
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mjd = time - 2415020.0;
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year = 1900 + mjd/365.25;
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T = (mjd + Delta_ET(year)/secday)/36525.0;
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M = Radians(Modulus(358.47583 + Modulus(35999.04975*T,360.0)
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- (0.000150 + 0.0000033*T)*Sqr(T),360.0));
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L = Radians(Modulus(279.69668 + Modulus(36000.76892*T,360.0)
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+ 0.0003025*Sqr(T),360.0));
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e = 0.01675104 - (0.0000418 + 0.000000126*T)*T;
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C = Radians((1.919460 - (0.004789 + 0.000014*T)*T)*sin(M)
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+ (0.020094 - 0.000100*T)*sin(2*M) + 0.000293*sin(3*M));
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O = Radians(Modulus(259.18 - 1934.142*T,360.0));
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Lsa = Modulus(L + C - Radians(0.00569 - 0.00479*sin(O)),twopi);
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nu = Modulus(M + C,twopi);
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R = 1.0000002*(1 - Sqr(e))/(1 + e*cos(nu));
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eps = Radians(23.452294 - (0.0130125 + (0.00000164 -
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0.000000503*T)*T)*T + 0.00256*cos(O));
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solar_vector->x = R*cos(Lsa);
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solar_vector->y = R*sin(Lsa)*cos(eps);
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solar_vector->z = R*sin(Lsa)*sin(eps);
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} /*Procedure Calculate_Solar_Position*/
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/*------------------------------------------------------------------*/
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/* Calculates stellite's eclipse status and depth */
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Sat_Eclipsed(vector_t *pos, vector_t *sol, double *depth)
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double sd_sun, sd_earth, delta;
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/* Determine partial eclipse */
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sd_earth = ArcSin(xkmper/pos->w);
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Vec_Sub(sol,pos,&Rho);
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sd_sun = ArcSin(sr/Rho.w);
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Scalar_Multiply(-1,pos,&earth);
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delta = Angle(sol,&earth);
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*depth = sd_earth - sd_sun - delta;
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if( sd_earth < sd_sun )
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} /*Function Sat_Eclipsed*/
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/*------------------------------------------------------------------*/