Fortran Astrodynamics Toolkit

Overview

The goal is to produce a comprehensive library, written in modern Fortran (Fortran 2003/2008), of all the standard orbital mechanics algorithms. This is a work in progress. Currently-implemented and proposed capabilities include:

• Lambert solvers

• [x] Gooding
• [x] Izzo
• [x] Arora

• Kepler propagators

• [x] Gooding
• [x] Shepperd
• [x] Goodyear

• ODE solvers (with event-finding)

• [x] Runge-Kutta
• [ ] Nystrom
• [ ] Adams

• Force models

• [ ] point mass gravity field
• [x] geopotential gravity
• [ ] solar radiation pressure
• [ ] atmospheric drag
• [ ] relativistic effects

• Reference frames

• [x] IAU_EARTH
• [x] IAU_MOON

• Celestial Body Ephemerides

• [x] JPLEPH
• [x] SPICE
• [x] Analytical Moon w.r.t Earth
• [x] Analytical solar system primary bodies

• Alternate equations of motion

• [x] Circular restricted three-body problem
• [x] Clohessy-Wiltshire
• [x] Modified equinoctial elements

• Misc

• [x] orbital element conversions
• [x] halo orbits
• [ ] targeting and optimization
• [ ] spacecraft engine models

Examples

Building

A FoBiS configuration file (fortran-astrodynamics-toolkit.fobis) is provided that can build the library and examples. Use the mode flag to indicate what to build. For example:

• To build all the examples using gfortran: FoBiS.py build -f fortran-astrodynamics-toolkit.fobis -mode tests-gnu
• To build all the examples using ifort: FoBiS.py build -f fortran-astrodynamics-toolkit.fobis -mode tests-intel
• To build a static library using gfortran: FoBiS.py build -f fortran-astrodynamics-toolkit.fobis -mode static-gnu
• To build a static library using ifort: FoBiS.py build -f fortran-astrodynamics-toolkit.fobis -mode static-intel

The full set of modes are:

• static-gnu
• static-gnu-debug
• static-intel
• static-intel-debug
• shared-gnu
• shared-gnu-debug
• shared-intel
• shared-intel-debug
• tests-gnu
• tests-gnu-debug
• tests-intel
• tests-intel-debug

To generate the documentation using ford, run:

FoBis.py rule --execute makedoc -f fortran-astrodynamics-toolkit.fobis

Third-Party Requirements

A script get_third_party.sh is included to download and build the third-party dependencies on unix-like operating systems.

Pyplot-Fortran

The plots generated by the examples are done using the pyplot-fortran module. The git repo includes pyplot-fortran as a submodule, and it will automatically be included when building with FoBiS.

Ephemeris files

To use the ephemeris_module, a copy of one of the JPL binary ephemeris files must be present in the eph directory. This can be built from the instructions at: ftp://ssd.jpl.nasa.gov/pub/eph/planets/fortran/userguide.txt. For example (on Linux):

wget ftp://ssd.jpl.nasa.gov/pub/eph/planets/fortran/*
wget ftp://ssd.jpl.nasa.gov/pub/eph/planets/ascii/de405/*
#edit asc2eph.f file to set NRECL = 4:
sed -i '_original' '/^C.*PARAMETER ( NRECL = 4 )/s/^C//' asc2eph.f
gfortran asc2eph.f -o asc2eph
cat header.405 ascp*.405 | ./asc2eph
mkdir Fortran-Astrodynamics-Toolkit/eph
mv JPLEPH Fortran-Astrodynamics-Toolkit/eph/JPLEPH.405

Geopotential files

To use the geopotential_module, you need a geopotential model file (for example GGM03C.GEO from ftp://ftp.csr.utexas.edu/pub/grace/GGM03/GGM03_Archive.zip). This should be placed in the grav directory. For example:

wget ftp://ftp.csr.utexas.edu/pub/grace/GGM03/GGM03_Archive.zip
unzip GGM03_Archive.zip
mkdir Fortran-Astrodynamics-Toolkit/grav
cp GGM03_Archive/GGM03C.GEO Fortran-Astrodynamics-Toolkit/grav

See also

• SPICE
• NOVAS
• SOFA
• LLEA