Automating the assessment of orbit predictions and estimations for building and maintaining a new catalogue

One of the primary aims of the Space Environment Research Centre (SERC) is to build and maintain its own catalogue of objects in near-Earth orbits. This will provide accurate ephemeris data for object acquisition in both passive and active tracking, covariance matrices for sensor schedule tasking and observation correlation, state and uncertainty propagation for conjunction assessments, and help facilitate the remote maneuver of debris using high powered lasers delivered from ground stations, which is the primary objective of SERC. The catalogue comprises objects which pose a threat of colliding with Optus satellites identified in conjunction assessments, potential candidates for the laser maneuver, and other objects of interest for ongoing research including Envisat, Topex, small cubesats, and HAMR debris. In this paper, we will present methods to automate the assessment of orbit predictions and estimations to maintain and build a new catalogue of space assets and debris. The process begins by running an orbit determination seeded by parameters stored in a catalogue and/or publicly available. The characteristics of an object of interest determined during the orbit estimation, such as the ballistic coefficient or radiation coefficient, are assessed as to whether they are within physical limits and are also compared against historic estimated values to test validity. In the event of a new object where no historic data is available, ballistic/radiation coefficients are stored and not used until a sufficient number is available to achieve statistical confidence in the stored values. Alternatively, a ballistic coefficient estimation method for low objects and an equivalent method for higher orbits can be used. The observation residuals generated from the orbit determination (OD) process are assessed as to whether they are within a given threshold based on the nominal noise of each sensor within our network. Comparisons of observations with highly accurate external ephemeris data from the International Laser Ranging Service (ILRS) are presented to show the level of sensor noise. If the RMS of an observation arc is above a threshold, which is set based on the observation weighting factor, the pass is automatically weighted weaker thus increasing the threshold for that pass. At this point, the OD process runs iteratively until all observation arcs stay within their respective thresholds. This ensures that outliers are tagged and kept quarantined in the catalog. The next step is to assess the prediction accuracy of the generated ephemeris data. The generated state from the OD process is propagated backwards and compared against observation arcs before the OD starting epoch. Regression models based on historic data from the catalog are used to set the threshold limits for predictions lengths dictated by varies orbital regimes. If a pass falls outside the predication threshold, the ephemeris data is quarantined and assessed manually for accuracy and reliability. Results are demonstrated here for the different orbital regimes considered.