Orbit Determination and Predicting the Behaviour of Space Objects

Project lead: RMIT University

Researchers: Robert Norman, Emma Kerr, Brett Carter, Julie Currie, Ronald Maj, Toshihiro Kubo-oka

Participants: RMIT University, National Institute of Information and Communications Technology (Japan)

A new advanced real-time POD software platform that incorporates attitude modelling of ‘controlled’ satellites orbiting at a range of altitudes has been developed as well as new atmospheric mass density and drag models. The improved estimation of orbit parameters allows for improved collision assessments for RP3.

Precise Orbit Determination (POD)

The newly developed GNSS POD software platform has the capability to process GPS two-frequency (L1/ L2) pseudo-range and carrier phase measurements for Precise Orbit Determination of low Earth orbit (LEO) satellites. The software provides accurate (>10 cm) ephemeris data for LEO satellites having GNSS receivers on-board. This software is also being used to validate the new and improved atmospheric mass density and drag model in terms of orbit prediction.

Atmospheric Mass Density (AMD)

The new AMD model includes models for both the neutral and ion densities in the low earth orbit atmosphere. The ion (predominately O+) density and complex dynamics have been included in the model and drag equation. Above altitudes of 500 km the ion contribution to the overall atmospheric mass density becomes significant and at heights of 1,000 km can be as much as 30% of the total mass density. 

Ray Tracing based on Geometrical optics

The 3-D ray tracing software is designed to simulate the laser signal traversing the atmosphere to the target location. This new ray tracing technique simulates a flux tube having the characteristics and dimensions of the laser beam. The signal strength and cross section shape of the laser signal at the target (satellite/debris) can be determined. A new homing-algorithm was developed which accurately predicts the simulated laser signal direction to hit the desired target location.

Project lead: RMIT University

Researchers: Yang Yang, Tetsuharu Fuse 

Participants: RMIT University, National Institute of Information and Communications Technology (Japan)

This program has developed an advanced ROD platform for ‘uncontrolled’ space objects and a new semi-analytic orbit propagator for fast and accurate orbit information for RP3.

Reliable Orbit Determination (ROD)

The ROD software platform comprises versatile orbit determination algorithms that employ data from a variety of different sources; e.g. satellite laser ranging (SLR) and angular observation processing. The ROD software was tested and validated using Mt Stromlo datasets as well as RMIT’s Optical Observatory (ROO) telescope datasets. 

The ROD software contains the following Batch Least Squares (BLS) filter when dealing with sparse observational data as well as following sequential filters:

• Unscented Karlman Filter (UKF)
• Augmented Unscented Karlman Filter (AUKF)
• Gaussian Mixture Unscented Karlman Filter (GMUKF)

The ROD software estimates the latency of the telescope error for calibration of time stamps attached to optical observations for GEO and LEO objects.

Semi-analytic Satellite Theory (SST)

This new innovative SST uses the Heterogeneous Multi-scale Method (HMM) to deal with the problem of having multiple scales. The introduction of the HMM introduces a kernel function that approximates the small variations in the finite timescale leading to more accurate outcomes in the integration step of the longer timescales. The new technique is suited for short and longer arc computations. The performance of this new technique has been compared against the performance of current orbit propagators and has consistently been found to be computationally quicker and more accurate.