Conclusions

This paper has re-examined the Spacetrack Report Number 3 formulation of analytical propagation. By incorporating changes posted over the last quarter century, a unified and improved version is presented for general use. Structural changes to the code have been completed permitting the ability to process multiple satellites at one time. We chose to omit the Lyddane choice change for certain inclinations to maintain as close a performance to what we believe AFSPC is doing today. However, we also included comments in the source code to facilitate location of any updates now, or at a future time. Test cases are included to demonstrate verification of operation with the branches in the code, for difficult orbits, as well as cases encountered throughout the years. The results show that continued use of the STR#3 version, and to a lesser extent some of the more recent versions, can result in potentially large errors when producing ephemerides. We also noted the difficulty with aligning a particular version of SGP4 with a particular TLE as the data formats and processing have changed throughout the years. Finally, we hope this form of documentation will motivate similar efforts for additional analytical theories in a similar fashion, along with satellite data to use with each theory. Any questions, comments, additions, etc. may be addressed to David Vallado at dvallado@centerforspace.com.

Acknowledgements

Many people were involved with this project in addition to the co-authors listed. I am very grateful for all the help, and support I received during this long project. Felix Hoots provided significant insight and details of the original development and John Seago provided suggestions for a more concise description of the time and coordinate systems. A special thank you is due to Jeff Beck who provided the MATLAB version based on the C++ code. Joe Coughlin and Egemen Imre provided JAVA code.

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Appendices

Appendix	Page
A. Organizational Nomenclature	29
B. Two-Line Element Set Format	30
C. TEME Coordinate System	32
D. Computer Code Listing	35
E. Test Case Listing	37
F. Test Case Results Listing	47

Footnotes

* Senior Research Astrodynamicist, Center for Space Standards and Innovation, 7150 Campus Dr, Suite 260, dvallado@centerforspace.com, AIAA Associate Fellow. † Principal Engineer, 25 Blackness Avenue, pcrawford@dundee0.demon.co.uk. ‡ Orbit Determination Lead Engineer, 220 Valley Creek Blvd, rhujsak@agi.com. § Senior Research Astrodynamicist, Center for Space Standards and Innovation, 7150 Campus Dr, Suite 260, tskelso@centerforspace.com, AIAA Associate Fellow.