Function calceph_scompute 

pub unsafe extern "C" fn calceph_scompute(
    JD0: f64,
    time: f64,
    target: c_int,
    center: c_int,
    PV: *mut f64,
) -> c_int

compute the position <x,y,z> and velocity <xdot,ydot,zdot> for a given target and center