function ABCt_vec = SphericalToCartesian(phi_theta)
d = 0.0001;
c = 299792.458;
rho = 20500;

A = rho*cos(phi_theta(1))*cos(phi_theta(2));
B = rho*cos(phi_theta(1))*sin(phi_theta(2));
C = rho*sin(phi_theta(1));
R = sqrt(A^2 + B^2 + (C-6370)^2);
t = d + (R/c);

ABCt_vec = [A;B;C;t];

