SGP4 Orbit Determination

In 2006, an updated version of SGP4 was presented for general use. The propagation routine relies on Two-Line Element (TLE) set data provided by the U.S. Government for several decades. Many independent organizations have access to observations, or ephemerides developed with other programs. Because the TLE is a compact means to obtain modestly accurate and fast calculations, it is desirable to have an orbit determination package that is compatible with the aforementioned code. This paper presents the code, test cases, and discussion of computer code to produce TLE data from an externally derived ephemeris. Initial code is also developed for processing raw observations.