Yang Zhao, SPACE Research Centre, School of Mathematical and Geospatial Sciences, RMIT University, Kefei Zhang, SPACE Research Centre, School of Mathematical and Geospatial Sciences, RMIT University, James Bennett, SPACE Research Centre, School of Mathematical and Geospatial Sciences, RMIT University / EOS Space Systems Pty Ltd, Mount Stromlo, Canberra, AUSTRALIA, Jizhang Sang, School of Geodesy and Geomatics, Wuhan University, Wuhan, CHINA, Suqin Wu, SPACE Research Centre, School of Mathematical and Geospatial Sciences, RMIT University
Keywords: Two-line Element Sets (TLEs), Outlier Detection, Consistency Check
Abstract:
As the most complete source of orbital element information available to the public, the NORAD two-line element sets (TLEs) are used in a wide variety of orbit propagation tasks. Unfortunately, there is no error information provided for TLEs and therefore no measure of the data quality. Due to orbit manoeuvres, errors introduced during the TLE generation and unmodeled perturbations, there are inevitable outliers in the TLEs, which have a large deteriorative impact on orbit determination and propagation. Most of the current methods identify outliers using the three-sigma rule or a Mahalanobis distance-based detection method. However, in these methods the different perturbation characteristics of space objects in different altitudes are not taken into account. This study presents an improved method for detecting outliers in the TLEs based on a consistency check on pairwise differential residuals of adjacent TLEs. A filter based on the principle of locally weighted regression is applied on the pairwise differential residuals to investigate their underlying structure. The detection threshold is then determined by the variance of the filtered residuals in the moving window. Satellites from different altitudes with known manoeuvre histories were selected to assess the effectiveness of this improved method. Our results show that this method can achieve reliable detection of the manoeuvre events. The difference between the characteristics of TLE outliers of satellites and debris objects is also analysed to facilitate the application of the satellite-based method to debris to identify erroneous TLEs. Finally, a set of criteria for TLE outlier detection are proposed based on the different characteristics of space objects according to their altitudes. It is expected that this improved method will contribute to more robust orbit propagation and conjunction analysis using TLEs.
Date of Conference: September 15-18, 2015
Track: Poster