Speaker
Dr
Jizhang Sang
(Wuhan University)
Description
A TLE-based Representation of Precise Orbit Prediction Results
Jizhang Sang, Bin Li
School of Geodesy and Geomatics, Wuhan University
Openly accessible TLEs are widely used to predict orbit positions of space objects. The computing efficiency of the analytic SGP4 algorithm is particularly attractive in applications where orbit positions of thousands of objects are needed. On the other hand, the accuracy of the TLE-computed positions is far less satisfactory than that of orbit predictions using more rigorous orbit determination and prediction methods. The delivery of the accurate orbit determination and prediction results is usually in the form of evenly spaced position and velocity, that would need a data file with size of hundreds of KB. This would require large computer storage for hundreds of thousands of space objects, and the use of these orbit data files in the space conjunction analysis would also require large computing storage.
This paper presents an algorithm using TLE/SGP4 to represent the accurate orbit prediction results. First, the accurately predicted positions are used as observations to determine a set of TLE employing the SGP4 algorithm. Then, the differences between the accurate positions and TLE-computed positions are fitted with a series of sinusoid terms. In this way, the accurately predicted position is computed as the sum of the position computed using TLE and the correction computed using the series of sinusoid.
The algorithm is experimented for a prediction time of 30 days for 4 satellites at altitudes of 690km, 820km, 1500km and 5800km. The accurate orbit predictions are obtained after the orbit determination using laser tracking data. 100 simulation runs are performed for each satellite. The maximum errors representing the accurately predicted positions over the 30-day prediction period are about 220m, 85m, 76m and 34m for the four test satellites, respectively. The representation accuracy clearly has dependency on the orbit altitude.
Experiment results show that the predicted orbits over a period as long as 30 days can be represented in the proposed algorithm in accuracy at 200m for satellite at altitude of 700km, and 30m for satellite at altitude of 5840km. The algorithm is purely analytic, so it is computationally very efficient. Also, it uses TLE and a short series of sinusoid, only a data file of 1 KB is needed to represent the predicted orbit. Therefore, the algorithm could find application in the future space conjunction analysis involving hundreds of thousands of debris objects.
| Applicant type | First author |
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Primary author
Dr
Jizhang Sang
(Wuhan University)
Co-author
Mr
Bin Li
(Wuhan University)
