Fig. 1. Schematic of observation geometry

Fig. 2. Low-orbit objects observation. (a) Track of subsatellite point; (b) observation geometry of different windows varies with time

Fig. 3. OCS curves of space objects at different observation geometry. (a) Three-axis stabilization; (b) spinning

Fig. 4. Schematic of the forward direction of nodes in a warping path

Fig. 5. Schematic of space object with normal working status

Fig. 6. Schematic of space object with abnormal working status. (a) Offset of 30°; (b) offset of 90°; (c) offset of 130°; (d) spinning about body Z; (e) sun alignment with nadir constraint

Fig. 7. Three space object models. (a) Fengyun; (b) GPS; (c) Tiangong

Fig. 8. DTW distance between phase angle curves of similar access

Fig. 9. Typical examples of phase angle variation in similar access

Fig. 10. DTW distance between OCS curves of similar access

Fig. 11. Typical OCS variation of similar access

Fig. 12. Abnormal working status detection of Fengyun. (a) Abnormal pointing; (b) abnormal rotation

Fig. 13. Abnormal working status detection of GPS. (a) Abnormal pointing; (b) abnormal rotation

Fig. 14. Abnormal working status detection of Tiangong. (a) Abnormal pointing; (b) abnormal rotation