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Orbit determination routines for Python

Project description

This is orbdetpy, a Python and Java library for orbit determination. It is a thin Python wrapper for our Java estimation tools and Orekit.


The force model for orbit propagation can be configured to include:

  1. EGM96 gravity field up to degree and order 360.
  2. Earth solid tides due to the influence of the Sun and Moon.
  3. FES 2004 ocean tide model up to degree and order 100.
  4. The NRL MSISE-00 and simple exponential models for atmospheric drag.
  5. Solar radiation pressure.
  6. Third body perturbations from the Sun and Moon.

The measurement model supports range, range-rate, angles, and inertial Cartesian coordinates. Filtering is done with our Unscented Kalman Filter or Orekit's Extended Kalman Filter. Dynamic Model Compensation (DMC) can be used with either filter to estimate additional perturbing acclerations that result from unmodeled dynamics, maneuvers etc.


  1. Install the Java Development Kit 8 (1.8) from Set the JAVA_HOME environment variable to the JDK installation folder. The java executable must be added to the system path.

  2. Install Python 3.7.0 or higher and run pip install orbdetpy to install orbdetpy and other package dependencies.

  3. Update the astrodynamics data under orbdetpy/orekit-data periodically by running the following. You might need to be the root user on some systems.

    python -c "from orbdetpy.astro_data import update_data; update_data();"


  1. : Run OD with real angles measurements. Also demonstrates the Laplace IOD method for estimating an initial state vector.

  2. : Predict satellite passes for ground stations or geographic regions using TLEs. Current elements may be obtained from sites such as

  3. : Propagate TLEs given by command-line arguments.

  4. : Test reference frame and other conversion functions.

  5. : Demonstrates measurement simulation and orbit determination functions.

  6. : Interpolate state vectors.


  1. Developers will need Apache Maven 3+ to build the Java library. Build using the following from the orbdetpy/ sub-folder, where os_cpu_type is linux-x86_64, linux-x86_32, windows-x86_64, windows-x86_32, osx-x86_64, or osx-x86_32 depending on your CPU and OS:

    mvn -e -Dos.detected.classifier=os_cpu_type package

    The command-line is simpler on Intel/AMD 64-bit Linux:

    mvn -e package

  2. Download and extract under the orbdetpy/ sub-folder.

Known Issues

  1. You might receive warnings from the Windows Defender Firewall on Microsoft Windows. Grant orbdetpy network access permissions.

  2. If you use the multiprocessing Python package, imports and calls into orbdetpy must not span multiprocessing function calls. That is, orbdetpy can be used in the parent process or the spawned child processes, but not both. A workaround is to run the orbdetpy RPC server using orbdetpy/ in a separate terminal window before running your Python code.

Project details

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