LOTOS Models

The following models are available within LOTOS and can be selected by the user:

Environment

• Earth gravity field with zonal harmonics up to J6
• DE405 ephemeris library
• Analytic polynomial ephemerides for highest performance
• Atmospheric drag with Jacchia-Bowman 2008 or exponential atmosphere model
• Van-Allen belt integrated radiation flux
• Third body perturbation from Sun, Moon and planets
• Solar radiation pressure and solar wind

Attitude Controls

• Unit vector components in inertial or local orbit frame (RTN)
• Euler angles with throttle in inertial or local orbit frame (RTN)
• Euler angle rates in inertial or local orbit frame (RTN)
• Spacecraft body rates (6DoF)
• Fully automatic initial guess generation with analytic laws or from external file (either control history or trajectory)

Spacecraft

• Mass and moments of inertia
• Power model incl. battery
• Propulsion parameters (Isp, Thrust) as function of power
• Propulsion time schedule (e.g. inactive on weekends)
• Propulsion shut-off during eclipses
• Thruster firing limitations (e.g. min./max. duration)
• Thruster on-off mode (bang-bang control)
• Disturbances of thrust direction and magnitude for robustness analysis
• Attitude and slew rate limitations
• Wheel momentum and torque
• Star tracker with boresight direction and field of view
• Reference area, drag coefficient and reflectivity index

Dynamics

• Time or equinoctial element L as independent variable
• Normalized or un-normalized independent variable
• Equations of Motion based on equinoctial elements
• Additional states: battery capacity, dwell time radiation belt, radiation dose, spacecraft attitude
• Several ODE solvers:
  • Variable step-size solver Runge-Kutta 4/5
  • Variable step-size solver Runge-Kutta 7/8
  • Fixed step-size solver Runge-Kutte 4
  • Variable step-size solver MEBDFDAE