Over a quarter century ago, the United States Department of Defense (DoD) released the equations and source code used to predict satellite positions through SpaceTrack Report Number 3 (STR#3). Because the DoD's two-line element sets (TLEs) were the only source of orbital data, widely available through NASA, this code became commonplace among users needing accurate results. However, end users made code changes to correct the implementation of the equations and to handle rare cases encountered in operations. These changes migrated into numerous new versions and compiled programs outside the DoD. Changes made to the original STR#3 code have not been released in a comprehensive form to the public, so the code available to the public no longer matches the code used by DoD to produce the TLEs. Fortunately, independent efforts, technical papers, and source code enabled us to synthesize a non-proprietary version which we believe is up-to-date and accurate. This paper provides source code, test cases, results, and analysis of a version of SGP4 theory designed to be highly compatible with recent DoD versions.

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A retrospective review was conducted of 112 active-duty military patients receiving anterior cruciate ligament reconstruction between 1985 and 1987. Mean age of these patients was 26.4 years, average follow-up was 2.35 years, and the average interval from time of injury to reconstruction was 13.6 months. The three most commonly employed surgical techniques were the Andrews' iliotibial band tenodesis, mid-third patellar tendon autograft, and a combined Andrews' and mid-third patellar tendon reconstruction. Seventy-eight patients (69.6%) returned to full duty and the ultimate disposition was not affected by the reconstructive procedure performed, chronicity of injury, or sex. A statistically higher percentage of patients over 30 years old returned to full unrestricted military service than did patients under 30. Associated posterior cruciate injury and degenerative joint disease resulted in poorer results. Our results demonstrate that functional restoration, based on the occupational criteria of return to full unrestricted duty, is likely following anterior cruciate ligament reconstruction.

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