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Installation

Note

If you have previously installed REBOUND in your environment, make sure you upgrade it to the latest version.

It's easiest to install ASSIST into a python virtual environment. If you already have a virtual environment or do not want to use one, you can skip this step. Otherwise, run the following command in an empty directory. They will setup and activate a new virtual environment in a directory. 

python3 -m venv venv
source venv/bin/activate
Now we can install numpy, REBOUND, and ASSIST: 
pip install numpy
pip install rebound 
pip install assist

To use the C version of ASSIST, first clone the REBOUND and then the ASSIST repository. In an empty directory, run: 

git clone https://github.com/hannorein/rebound.git
git clone https://github.com/matthewholman/assist.git

Large file size

Some of the files are over 2 GB in size. The sb441-n373.bsp file below is over 14 GB.

To use ASSIST, you also need to download ephemeris data files. One file for planet ephemeris and another suplementary file for asteroid ephemeris. The following commands download these files with curl. You can also manually download them using your browser. You can store these files anywhere. If you're installing REBOUND from the repository, a good place to put them is in a new directory with the name data.

mkdir data
curl https://ssd.jpl.nasa.gov/ftp/eph/planets/Linux/de440/linux_p1550p2650.440 -o data/linux_p1550p2650.440
curl https://ssd.jpl.nasa.gov/ftp/eph/small_bodies/asteroids_de441/sb441-n16.bsp -o data/sb441-n16.bsp

For some of the examples, you will also need the planet ephemeris file with an extended coverage.

curl https://ssd.jpl.nasa.gov/ftp/eph/planets/Linux/de441/linux_m13000p17000.441 -o assist/data/linux_m13000p17000.441

Info

Support for the n373 file has been added recently. Compare your results to those obtained with the standard n16 file.

If you wish to carry out a calculation with 373 small bodies (instead of just the 16 most massive asteroids in the n16 file above) you will want to download the full asteroid file:

curl https://ssd.jpl.nasa.gov/ftp/eph/small_bodies/asteroids_de441/sb441-n373.bsp -o data/sb441-n373.bsp

You can now verify that your installation of assist works.

Start a python interpreter, or open a new notebook if you're planning to use Jupyter notebooks. 

python3
Then run the following code: 
import assist
ephem = assist.Ephem("data/linux_p1550p2650.440", "data/sb441-n16.bsp")
print(ephem.jd_ref)
ephem.get_particle("Earth", 0)
You should see the default reference Julian date (2451545.0) and the position of the Earth at that time printed on the screen.

Go to one of the example directories and compile the problem file. This will also trigger the installation of the REBOUND and ASSIST shared libraries.

cd assist/examples/plain_interface
make

Now, you're ready to run the example with:

./rebound

Windows

ASSIST has been tested on both linux and MacOS. You might be able to run it on Windows with the help of the Windows Subsystem for Linux (WSL).