The Python Entry TRAjectory tool (PETra) is a tool for calculating the trajectories
of objects undergoing an uncontrolled (ballistic) atmospheric re-entry on Earth.

PETra is written in Python v3.5.2 and makes extensive use of the NumPy, SciPy, and 
Matplotlib packages and libraries.

The equations of motion are integrated with SciPy's odeint function, which actually
calls the LSODA integrator in the odepack Fortran library.

To use, create an input file named 'inputs.py' (use the template provided). For a complete list of possible inputs, see the user manual. To run, 
run the main.py file.

PETra uses Joshua Milas' Python port of the NRLMSISE-00 atmosphere model, released on
an MIT license, in order to calculate atmospheric quantities.