@Arrowstar here is a simpler way compared to my last post to see something is going awry with the propagation in the latest release compared to earlier versions. Download this package. Open Alaba_5-19-20.mat Propagate to next Mun encounter (#39) and note time is Y4 D262 02:31:33 Copy initial orbital data Open Alaba Prediction 3-10-20.mat Advance script to Event 10 (Encounter 39) Paste the copied orbital data into initial state Get UT from end of Ev