By developing an enhanced precise orbit determination (POD) model, Australians will be able to accurately find their precise position anytime, anywhere.

The project will focus primarily on the development of an enhanced POD model of the major error sources that impact the orbit quality: the solar radiation pressure (SRP) and attitude regime of the BeiDou (BDS) constellations.  

Image 1 CSNO

Figure 1. The Orientation of the spacecraft body frame for BeiDou MEO/IGSO and GEO satellites

The BeiDou system is the only GNSS system that, when combined with GPS, can significantly increase the ambiguity resolution success rate of a user in Australia (Figure 2). 

Image 2 cuffoff

Figure 2. Ambiguity success rate for CUT0 (Curtin, WA) station from Odolinski and Odijk 2015

Additionally, the complexity of these constellations renders the integration of the BeiDou observations in the ACS a rather challenging research task. The project will deliver the models and source code needed to compute and deliver precise products to support the operational implementation of the BeiDou system in the ACS, and thereby become an intrinsic part of a future National Positioning Infrastructure (NPI).

What will be Achieved

The project addresses an identified gap in the NPI’s requirements for building an Australian GNSS analysis capability for delivering precise point positioning corrections to PPP-RTK users anywhere, anytime at the highest possible accuracy. Specifically it will develop a precise orbit determination & processing system for the three BDS constellations that will be integrated into the ACS network platform.

The main objectives of the project are:

  • To evaluate the fitness for purpose of existing conservative force modelling approaches and how could these be applied and tuned to the BDS constellations. In particular, emphasis will be given to analytical solar radiation pressure (SRP) models.
  • To understand the current attitude regime law (Figure 3) that governs the BDS satellite dynamics. The attitude control on the GNSS satellites is dictated by two requirements or constraints, namely the transmitting antenna always points toward the Earth and that the solar panel axis is perpendicular to the Sun direction. These requirements necessitate that the satellites constantly rotate along the antenna axis which point to the Earth.
Image 3 circles

Figure 3. Current Yaw Steering (left) and Yaw fixed (Orbit Normal – ON) modes in the BeiDou attitude law

  • To evaluate the performance of GNSS networks (Figure 4) tracking BDS satellites and their ability to determine a series of adjustable parameters that will improve the precise orbit determination by reconstructing the accelerations due to SRP. 
Image 4 BETS

Figure 4. Current BETS, MGEX and AuScope network tracking BeiDou in off-line and real-time

The project will construct a precise orbit determination system capable of compensating the SRP acting on the BDS satellites, which is assumed to be the major error source affecting the quality of orbits. By doing this a new SRP model and processing capability for the BDS constellations will be provided for final integration into the ACS platform.

Project Team

Stavros MelachroinosDr Stavros Melachroinos
Project Leader
Geoscience Australia

Suelynn Choy sqDr Suelynn Choy
School of Mathematical and Geospatial Sciences

Qile ZhaoProf Qile Zhao
GNSS Research Centre
Wuhan University

Robert OdolinskiDr Robert Odolinski
National School of Surveying
University of Otago