I am trying to find Optimum data interval algorithm for orbit determination. Because in Leo, Geo orbit updates the measurement data can be different so that I want to implement an optimum data interval algorithm for Orbit determination. I found one thing for that LUPI algorithm but haven't still found more details about LUPI algorithm. Which kind of algorithm can use in Geo, MEO, Low orbit? Because Atmospheric drag and solar radiation are really important sometimes not need to update frequently the measurements. LUPI algorithm is mentioned in 'Conjunction Assessment Risk Analysis M.D. Hejduk NASA CARA Collision Avoidance “Short Course” Part I: Theory'