OPASKEP (Optimisation of NS, EW Station-Keeping Manoeuvres for GEO Satellites using Electric Propulsion)


The project objective is to develop optimal guidance laws for full electric propulsion station-keeping of GEO satellites with their corresponding thrusters accommodation architectures and a design environment to develop such an optimal configuration.


During the last decade electric propulsion has become a good alternative to traditional chemical satellite propulsion, also for large and small GEO platforms. Two of the most promising technologies are Ion Gridded Engines and Hall Effect Thrusters due to their high specific impulse compared to chemical thrusters.

This project provides elements to analyse the existing technologies from any point of view and provides a tool in order to optimize them considering usual missions constraints and thrusters configurations. Case of regular station keeping, transfer from parking orbit and station changes are considered.


To develop a tool for analysis, verification and validation of proposed strategies in the so-called “analysis, verification, and validation development environment” or AVVDE.

To raise the Technology Readiness Level (TRL) of this optimal guidance law technology from 2-3 to 4-5. Where third level means "Component and/or breadboard validation in relevant environment".

To serve as a stepping stone for future projects that may acquire TRL 7-8 with little effort. Where eighth level means “Actual system completed and “flight qualified” through test and demonstration (Ground or Flight)”. To enhance current station keeping models for GEO satellites using EP. This will allow them to save mass consumption and therefore to enlarge satellites usable lifetime.


The main features of the projects include:

  1. A review and assessment of EP Technology and Techniques
  2. Define an early prototype identifying the system drivers and potential Station Keeping strategies.
  3. Develop and Test of the optimal Station Keeping strategy in the so-called “analysis, verification, and validation development environment” or AVVDE.
  4. Analysis of Optimal Station Keeping Strategies and Operations.
  5. Produce a report with the conclusions and recommendations of this study.


The project is organised in 5 steps:

  1. Initially, a review and assessment of techniques and technology shall be conducted that provides an overview of state-of-the-art EP technology available, EP thrusters, and those that are expected to become available within the next decade, geostationary platform types and earlier use of EP for partial station-keeping activities. The length of this phase is approximately 1 month.
  2. In the second step, based on the previous review, the elaboration of the main system drivers (platforms geometry, plume impact on solar arrays, available power, potential thruster configurations, etc) shall take place. The Contractor shall define preliminary SK strategies for electric propulsion systems. Early prototyping and early implementation shall take place at this stage. The length of this phase is approximately 4 months.
  3. Next, an advanced methodology shall be presented as part of a full development environment (AVVDE) for optimization of the strategies. Because of the complexity of the problem, the contractor shall make use of state-of-the-art Non-Linear Programming environment (NLP-solver), to find optimal solutions. The length of this phase is approximately 6 months.
  4. As a following step, the guidance laws shall be optimized under full consideration of relevant constraints and conditions using the proposed development environment. These optimized guidance law solutions shall be applicable to real operational environments, relevant for industrial needs. The length of this phase is approximately 4 months.
  5. The obtained optimal solutions need to be converted into parametric guidance laws. Optimality shall then be demonstrated and further analyzed in a simulation environment that shall be part of the AVVDE. See also Figure 3 as a reference for the study logic. The length of this phase is approximately 2 months.

Current status

The first major milestone of the project has been held. During the Baseline Design Review (BDR), the preliminary version of the AVVDE design has been reviewed. The following set of activities have been performed:

  • A deep review and assessment on the existing techniques and technologies based in EP.
  • Analysis of the state-of-the-art of the station keeping strategies based in EP.
  • A comparison between GEO satellites controlled using Chemical Propulsion and those using EP.
  • The main platform and station keeping drivers have been identified and their impact on the software has been analysed.
  • The mathematical model of the station keeping problem has been produced to cover the different drivers.
  • A preliminary version of the AVVDE tool has been produced for their review on the BDR. In addition the initial version of the software development documentation has been produced.
  • The results achieved with the preliminary implementation of the AVVDE have been already documented and are being revised.


Status date

Thursday, October 9, 2008 - 17:13