TSX : Trajectory Solver version 1.1

========
Authors:
Nima Traore (c) 2016
Contribution by Boris Segret
Origin of some methods by Jim Lin
Special thanks: Emmanuel Grolleau & LeeRoy Malac-Allain 
=======================================================

Trajectory Solver is an interplanetary trajectory propagator for nanosatellites.
The Software uses scientific library PyKEP which provides basic tools to perform 
research in interplanetary trajectory design. 

Trajectory Solver was implemented under Python 2.7.6 with Ubuntu distribution on
Linux. Users using upgrade Python versions (3++) need following python libraries
to run the program: - setuptools3, scipy and numpy. And install PykEP library in
the path.

Users have at their disposal the configuration file "config.py" to customize the
propagator parameters. The configuration file is the only file users may use for
the set up, the creation or the declaration of any global variable. Those varia-
bles are recovered by the module "instances.py" to pass parameters into the ins-
tances of different classes. After the configuration file's set up, user can run
the Software.

=====================
Executing the program
=====================

To execute the program, users open a terminal (a linux environnement) and change
the directory into the TSX folder:

--> $ cd --PATH--/TSX

Then execute the main program "trajectory_solver.py":

--> $ python trajectory_solver.py

If users use an upgrade version version of python, then:

--> python--version-- trajectory_solver.py

Example: python3 trajectory_solver.py

When the program is runed, users can recover the output reference trajectory and
the output reference ephemerides files in the desired path chose in "config.py".
  
==================
Configuration file
==================

As said above the configuration file is the only interface that users can set up
variables and choose input and/or ouptut directories of files. The default input
and ouput are in the same directory as the "config.py". But users can change the
input / output directory by providing the desired directory path. 

The host trajectory file in the input should have at least a line, including the
spacecraft coordinate's values separated by spaces. These values are describe as 
following: epoch (in Julian Day), position vector x, y, z in (km/s) and velocity
vector vx, vy, vz in (km/s). If the input file contains more than a line, so the 
last line is the one taken into account to propagate the trajectory. Additionaly
the input file should not contain any string (but only float values). 

The reference trajectories or the reference ephemerides output files headers are
given in the vts format and can be customized as well; all the outputs files are
labeled as follow:
--> Reference trajectories : "ref_traj_YYYY-MM-DD_HHMMSS.xyzv"
--> Reference ephemerides  : "body name_YYYY-MM-DD_HHMMSS.eph"

If users do not want to put vts headers in outfiles, so this must be done in the
"config.py" by declaring the appropriate variables as an empty list.

=============
To Developper
=============

Following modules are not implemented; so an other programmer can implement them
in the future as necessary. Modules are located in the "src" folder and the com-
ponent diagram in the technical note show their location.

------------------------

-- "aspr.py":            acceleration due to a given body asperical spahe.   

-- "drag.py":            acceleration due to aerodynamic drag 

-- "delta_v.py":         initial delta to start the propagation and so on

-- "magnetic.py":        acceleration due to magnetic field 

-- "plasma.py":          acceleration due to plasma

-- "sampler.py":         time step sampling if classical Runge-Kutta is used

-- "data_accuracy":      a package to perform data accuracy

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