Working Group on Performance Simulations and Architectural Trade-offs (Plato)

Joint with GGOS Networks and Communications Bureau

Chair: D. Thaller (Germany)

Vice-Chair: B. Männel (Germany)

Link to the WG website at GGOS


Terms of Reference

The terrestrial reference frame (TRF) is the foundation for virtually all space-based and ground-based Earth observations. Positions of objects are determined within an underlying TRF and the accuracy with which objects can be positioned ultimately depends on the accuracy of the reference frame. The most accurate and stable global TRFs currently available are the “International Terrestrial Reference Frames (ITRFs)” produced under the auspices of the “International Earth Rotation and Reference Systems Service (IERS)” in cooperation with its technique-specific services IDS, IGS, ILRS and IVS. In order to meet the anticipated future needs of science and society, GGOS has determined that by 2020 the accuracy and stability of the ITRF needs to be better than 1mm and 0.1mm/y, respectively. The current ITRF is at least an order of magnitude less accurate and stable than these goals.

The ITRF is currently determined and maintained by a subset of ground-based observations acquired by the space-geodetic measurement techniques of VLBI, SLR, GNSS, and DORIS. Further improvements of the ITRF are thought to be achieved by:

  • Developing next generation space-geodetic stations with improved technology and system performance;
  • Improving the ground network configuration in view of global coverage and co-locations;
  • Improving the number and accuracy of surveys between co-located stations;
  • Deploying, improving and optimizing space-based co-locations.

This joint working group aids these activities and helps to evaluate the impact on the accuracy and stability of future ITRFs.



Several aspects related to design of ground- and space-based architectures and their impact on TRF accuracy and stability are investigated:

  • Study different ground station architectures and possible evolutions (different techniques, mix of legacy and next generation stations, co-located sites, data improvements/ degradations, etc.);
  • Develop optimal methods of deploying next generation stations for TRF computation;
  • Study requirements on site ties and space ties, including trade-offs between co-locating techniques on ground and/or in space;
  • Study different space-based architectures, including laser ranging to GNSS or LEO satellites, VLBI observations to GNSS satellites;
  • Study new concepts for space-based architectures (including inter-satellite links, specially designed co-location satellites, VLBI transmitter on the moon, etc.);
  • Study evolution of space-based architectures (including degradation of laser ranging targets, additional targets, new satellites / constellations, etc.);
  • Study trade-offs in space-geodetic data, e.g., between number of stations vs. accuracy of observations, and co-locating techniques at all sites vs. co-locating some techniques at some sites, and number of co-located satellites vs. amount of observations per space co-location.

These and other related aspects will be addressed by two types of approaches:

  • Develop improved analysis methods using all existing data and co-locations;
  • Carry out simulations for future improvements and optimization of ground network, space segment and observation scenario.