Satrap satellite reentry analysis program

For near-earth satellites the principal nongravitational force is the aerodynamic drag. Drag is a nonconservative force that continuously takes energy away from the orbit, causing a gradual decrease of the semimajor axis. As a consequence of drag the satellite can no longer continue in orbit and it crashes into the earth or burns up due to friction during reentry. Since the beginning of the Space Age an average of about one satellite every 6 days, or one piece of artificial debris every day, experienced this fatal descent. The prediction of the time at which this occurs is especially important for those satellite components which may survive the reentry intact. For this reason, various reliable models of the upper-atmosphere density were developed and the science of low-earth orbit lifetime predictions has grown rapidly, since the launch of the first artificial satellite. In order to estimate the satellite lifetime with an acceptable level of accuracy, an orbital predictor including a successful atmospheric model had to be available. To meet this need the orbit propagator SATRAP (SATellite Reentry Analysis Program) has been developed and implemented at CNUCE.