Overview

The goal of the Fortran Astrodynamics Toolkit is to produce a comprehensive library, written in modern Fortran (Fortran 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
  • [x] 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
  • [x] solar eclipsing
  • [ ] targeting and optimization
  • [ ] spacecraft engine models

Examples

<a href="https://github.com/jacobwilliams/Fortran-Astrodynamics-Toolkit/tree/master/tests/crtbp"><img src="https://github.com/jacobwilliams/Fortran-Astrodynamics-Toolkit/blob/master/tests/crtbp/crtbp_test.png" align="center" height="300"></a> <a href="https://github.com/jacobwilliams/Fortran-Astrodynamics-Toolkit/tree/master/tests/gravity"><img src="https://github.com/jacobwilliams/Fortran-Astrodynamics-Toolkit/blob/master/tests/gravity/trajectory.png" align="center" height="400"></a> <a href="https://github.com/jacobwilliams/Fortran-Astrodynamics-Toolkit/tree/master/tests/dro"><img src="https://github.com/jacobwilliams/Fortran-Astrodynamics-Toolkit/blob/master/tests/dro/dros.png" align="center" height="400"></a>

Building

The Fortran Astrodynamics Toolkit and the test programs will build with any modern Fortran compiler. A Fortran Package Manager manifest file (fpm.toml) is included, so that the library and tests cases can be compiled with FPM. For example:

fpm build --profile release
fpm test --profile release

To use Fortran-Astrodynamics-Toolkit within your fpm project, add the following to your fpm.toml file:

[dependencies]
fortran-astrodynamics-toolkit = { git="https://github.com/jacobwilliams/Fortran-Astrodynamics-Toolkit.git" }

or, to use a specific version:

[dependencies]
fortran-astrodynamics-toolkit = { git="https://github.com/jacobwilliams/Fortran-Astrodynamics-Toolkit.git", tag = "0.3" }

To generate the documentation using ford, run: ford ford.md

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. When compiling with FPM, this will automatically be downloaded and compiled.

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 http://download.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

Documentation

The documentation for the latest code in master can be found here.

See also

• SPICE
• NOVAS
• SOFA
• astro-fortran
• LLEA
• poliastro