Satellite Tracking Software

T.S. Kelso

  • SGP4 Pascal Library Version 2.65, 102,352 bytes, 2000-Jan-22

      This Turbo Pascal source code implements the NORAD SGP4/SDP4 orbital models for use with the standard two-line orbital element sets to determine earth-centered inertial (ECI) coordinates of earth-orbiting objects. This code implements both the near-earth and deep-space portions of the NORAD SGP4 orbital model. This version has routines for calculations of spacecraft subpoint and topocentric circumstances such as azimuth, elevation, range, and range rate or right ascension and declination—and even takes atmospheric refraction into account. NOW calculates visibility conditions, making it perfect for predicting visible passes of Mir or the US space shuttle.

      Unit SGP_TIME.PAS (routines Julian_Date_of_Epoch and ThetaG) modified to correctly interpret epoch year in the two-line element sets beyond the Year 2000 (through 2056).

      A C++ version of this code, developed by Varol Okan, is available from

      A C++/C# version of this code, developed by Michael Henry, is available from

      A Java version of the SGP4 portion of this code, developed by Pedro J. Fernandez, is available online in

      A complete rework of the SGP4 code found in Spacetrack Report Number 3, developed by David A. Vallado, Paul Crawford, Richard Hujsak, and T.S. Kelso, is available online in "Revisiting Spacetrack Report #3. Source code is available in C++, FORTRAN, MATLAB, and Pascal. Highly recommended.

  • TrakStar Version 2.65, 128,993 bytes, 2000-Jan-22

      For those who want highly-accurate ephemerides providing Earth-centered inertial (ECI) coordinates, satellite subpoint (latitude, longitude, and altitude for nonspherical earth), look angles (azimuth, elevation, range, and range rate), and right ascension and declination. Supports determination of visibility conditions for specified observer(s). Even atmospheric refraction is accounted for. Whether you want this program for its analytical value or for an example of how to implement the routines in the SGP4 Pascal Library (, this program is a MUST!

      Executable (TRAKSTAR.EXE) recompiled with new SGP_TIME.PAS to correctly interpret epoch year in the two-line element sets beyond the Year 2000 (through 2056). Also recompiled to fix the problem with Runtime Error 200 on faster computers.

  • Pass Update, 27,649 bytes, 2000-Jan-16

      Version 2.50b of the program used with Pass Scheduler. Program permits fully automatic processing of all of your .TLE files without prompting. Updated to fix the problem with Runtime Error 200 on faster computers.

  • Pass Scheduler 1.50, 38,038 bytes, 1999-Nov-30

      Pass Scheduler is a program which will allow the you to automatically generate schedules of satellite passes from a set of pre-selected files of observation sites and NORAD two-line orbital element sets. The schedule generated is listed in order of increasing rise time and provides:

      • Satellite name
      • Rise date
      • Rise time, azimuth, and elevation
      • Time of culmination (maximum elevation), azimuth, and elevation
      • Set time, azimuth, and elevation
      • Visibility code

      Version 1.50 will now correctly interpret epoch years in the NORAD two-line element sets beyond the Year 2000 (through 2056). It also fixes the problem with Runtime Error 200 on faster computers.

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Dr. T.S. Kelso []
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Last updated: 2018 Jun 27 02:21:55 UTC
Accessed 353,545 times since 2000 December 16
Current system time: 2019 Dec 05 18:12:26 UTC