Tests of the Accuracies of SGP4/SDP4 Model Predictions

We analyze increasing variations of errors in two typical versions of the SGP4/SDP4 model for different orbits by taking orbits precisely determined with SLR as references. The errors grow exponentially after a few orbital periods. Numerical results show that for the low-, medium-, and high-earth orbits the numbers of orbital periods without significant errors from predictions are 40(h≤300 km), 150(300 km≤h≤1 200 km), 300(1 200 km≤h≤10 000 km), 55(semi-synchronous orbit;19 000 km≤h≤22 000 km), and 10(geosynchronous orbit; 33 000 km≤h≤38 000 km).The plots about error variations in this paper give references for engineers for predicting satellite orbits with the TLE and SGP4/SDP4 models.