Fig. 1. Diagram of relative angles between satellites

Fig. 2. Schematic diagram for two types of panoramic system. (a) Traditional panoramic annular system; (b) proposed two-mirror system

Fig. 3. Schematic diagram of characteristic point acquisition

Fig. 4. Schematic of point-by-point aperture expansion

Fig. 5. Flowchart of feature point calculation

Fig. 6. Freeform surface point cloud diagram. (a) Primary mirror; (b) secondary mirror

Fig. 7. Surface fitting results. (a) Primary mirror; (b) secondary mirror

Fig. 8. Optical design of two panoramic annular systems.

Fig. 9. Optical design of rear mirror assembly

Fig. 10. Complete optical system after stitching. (a) Freeform surface system; (b) aspheric surface system

Fig. 11. MTF comparison. (a) Freeform surface system; (b) aspheric surface system

Fig. 12. Relay system design and spot diagrams. (a) Design result of relay system; (b) spot diagrams

Fig. 13. Collimation-coupling system and wavefront aberration. (a) Collimation-coupling system design result; (b) wavefront aberration

Fig. 14. Overall light path diagram of optical system

Fig. 15. Beam divergence angles of antenna systems with different fields of view. (a) Freeform optical system with 30° field of view; (b) freeform optical system with 70° field of view; (c) aspheric optical system with 30° field of view; (d) aspheric optical system with 70° field of view

Fig. 16. Physical picture of freeform mirror

Fig. 17. Physical setup diagram of experimental equipment

Fig. 18. Communication test layout diagram

Fig. 19. Bit error rate test results. (a) 30° field of view; (b) 70° field of view