TLE accuracy analysis and conjunction prediction

Two Lines Elements (TLE) were widely used for on-orbit conjunction prediction. The accuracy of TLE data had great impact on conjunction prediction results, and was one of the necessary parameters for collision probability calculation. Only if the predicted position accuracy of TLE data were calculated exactly, the value of collision probability is reliable. In the research, the TLE position accuracy was calculated based on two kinds of criterion data, including updated TLE data and Consolidated Prediction Format (CPF) data, whose predicted position was more accurate than TLE data. The TLE position accuracy based on CPF data was used for true TLE position accuracy. Besides, both CPF data and TLE data were used for calculating conjunctions of satellites. CPF data was used for validating the conjunction results calculated based on TLE. The results of the research showed that the position accuracy based on updated TLE data was a little smaller than the true value. So in general cases, the collision probabilities were a little higher, which could be one reason for why conjunction predictions based on TLE were contained of a lot of fake results. With TLE data position accuracy based on CPF instead of updated TLE data, the conjunction results calculated with TLE data might be more reasonable.