Fig. 1. Schematic diagram of the Risley grating tracking system. (a) Structure principle; (b) Diffraction angle

Fig. 2. Main error sources of the system

Fig. 3. Risley grating tracking system error model

Fig. 4. ZEMAX error verification model and coordinate system diagram

Fig. 5. Simulation comparison between polar angle θ₁ and azimuth angle φ₁. (a) Polar angle θ₁ comparison; (b) Azimuth angle φ₁ comparison

Fig. 6. Simulation comparison between polar angle θ₂′ and azimuth angle φ₂′. (a) Polar angle θ₂′ comparison; (b) Azimuth angle φ₂′ comparison

Fig. 7. Simulation comparison between grating axis and grating tilt. (a) Comparison of polar angle θ₃ ; (b) Comparison of azimuth angle φ₃ ;(c) Maximum polar angle difference change; (d) Maximum azimuth angle difference change

Fig. 8. Tilt direction of the light source tilt error

Fig. 9. Pointing error caused by the light source tilt error. (a) Pointing error at HL=0.1°; (b) Pointing error at VL=0.1°; (c) Maximum pointing error varies with γ_L; (d) Maximum pointing error varies with the tilt error of the light source

Fig. 10. Pointing error caused by grating axis tilt error. (a) Pointing error at HR₁=0.1°; (b) Pointing error at VR₁=0.1°; (c) Pointing error at HR₂=0.1°; (d) Pointing error at VR₂=0.1°; (e) Maximum pointing error varies with γ_R1; (f) Maximum pointing error varies with γ_R2; (g) Change of the maximum pointing error with the tilt error of the grating axis

Fig. 11. Pointing error caused by grating angle error. (a) Pointing error at δ_ψ1=0.1°; (b) Pointing error at δ_ψ2=0.1°; (c) Change of the maximum pointing error with the angle error of the grating

Fig. 12. Schematic diagram of double grating turntable and installation test. (a) Double grating turntable; (b) Double grating turntable installation; (c) Test site installation test site

Fig. 13. Experimental test process

Fig. 14. Double grating turntable pointing error test site

Fig. 15. Experimental data of pointing error