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LOTOS

Low-Thrust Orbit Transfer Trajectory Optimization Software

Orbit transfers using electric propulsion and therefore low-thrust accelerations present an interesting field for trajectory optimization. One typical application is the transfer trajectory optimization of a telecommunication satellite from the launcher injection orbit to the geosynchronous equatorial orbit (GEO), where the injection orbit could be geostationary transfer orbit (GTO) or low Earth orbit (LEO). Since 2003 Astos Solutions provides trajectory optimization and mission analysis for this application worldwide – both to space agencies and to companies – but only after the recent increased interest for this topic the way for the creation of a COTS solution was paved.

LOTOS is an advanced tool for trajectory optimization and analysis of electric orbit-raising scenarios and hybrid transfers, where the chemical orbit-raising is followed by an electric orbit-raising. It allows simulation, optimization, verification and analysis of orbit transfer trajectories with electric (low-thrust) propulsion. For preparation and support of the spacecraft operations during the orbit transfer, LOTOS features the re-optimization of pre-computed attitude histories and optimal trajectories which has to be performed after an update of the spacecraft state by means of orbit determination. Since initial and final orbit are user defined, the tool is not just limited to typical GTO-GEO transfers of telecommunication satellites but offers a wide range of possible applications for low-thrust transfers such as constellation deployment and graveyarding. LOTOS facilitates:

  • Optimization of reference trajectories
  • Re-optimization of updated trajectories for spacecraft operations and autonomous transfers
  • Hybrid transfers
  • Verification of trajectories
  • Full 6DoF attitude control
  • Slew rate optimization
  • Graphical User Interface for full control of user customizable scenarios
  • Analyses related to transfer performance and spacecraft subsystem aspects
  • Automatic mission analysis reports
  • Built-in batch-processing
  • Command line interface for use at control centres
Possible optimization scenarios with user defined initial and final orbit include:
  • Time and fuel optimal transfers
  • Avoidance of GEO ring crossings
  • Thruster shutdown during eclipses
  • Slew rate limitations
The required high performance is provided by the state-of-the-art solver SOS for fast optimization (in the order of a few minutes).

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