code: def gmst(utc_time):
      
      ut1 = jdays2000(utc_time) / 36525.0
      theta = 67310.54841 + ut1 * (876600 * 3600 + 8640184.812866 + ut1 *
                                   (0.093104 - ut1 * 6.2 * 10e-6))
      return np.deg2rad(theta / 240.0) % (2 * np.pi)
docs: Greenwich mean sidereal utc_time, in radians.
  
      As defined in the AIAA 2006 implementation:
      http://www.celestrak.com/publications/AIAA/2006-6753/