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CVN in Chang’e-3 lunar exploration mission

CVN in Chang’e-3 lunar exploration mission. ZHENG Weimin Shanghai Astronomical Observatory, Chinese Academy of Sciences 3rd International VLBI Technology Workshop Nov 11, 2014, Groningen, Netherlands. Outline. Chang’E-3 overview CVN in Chang’E-3 mission Orbit and position determination

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CVN in Chang’e-3 lunar exploration mission

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  1. CVN in Chang’e-3 lunar exploration mission ZHENG Weimin Shanghai Astronomical Observatory, Chinese Academy of Sciences3rd International VLBI Technology Workshop Nov 11, 2014, Groningen, Netherlands

  2. Outline • Chang’E-3 overview • CVN in Chang’E-3 mission • Orbit and position determination • Summary

  3. The China’s Lunar Exploration Program (CLEP) 3 phases: Orbiting: Chang'e 1 (CE-1), 2007 CE-2, 2010 Landing: CE-3, CE-4 (2013~2016) Sample return: CE-5T1, CE-5, CE-6 2014-2020

  4. CE-1 established CVN Infrastructure CVN near real-time data flow in CE-1

  5. New Challenge of CE-3 mission A. Direct insertion of the 100km lunar orbit after braking CE-1 CE-2 CE-2 CE-1

  6. B. Powered descent procedure

  7. C. Lander and rover moon surface positioning

  8. Outline • Chang’E-3 overview • CVN in Chang’E-3 mission • Orbit and position determination • Summary

  9. New Requirements & techniques of CVN High accuracy Real time ability Accurate Moon surface positioning ( X band ΔDOR ) DOR – Differential of One-way Range ( e-VLBI + real time data process ) ( SBI ) SBI – Same Beam VLBI

  10. Mission Requirements on VLBI • Earth-Moon transfer orbit phase & Circumlunar phase • ΔDOR tracking group delay < 4ns (Actuality <0.5ns) • Orbit & angular determination and orbit prediction； • Data processing delay < 1minute (Actuality 15~40 seconds) • Lunar surface working phase • Lander & Rover tracking by SBI • Lander 3D position <1km (Actuality <100m ) • Rover relative position of the lander<500m (Actuality ~1m )

  11. CVN upgrade • New VLBI data center • Shanghai Tianma 65m radio telescope • New X-band receiver & digital terminal

  12. ΔDOR improves VLBI delay precision Five-minute scan sequence: Quasar-CE3-Quasar-CE3 Angular distance between CE-3 and Quasar < 10° Remove media & system errors Kroger et al

  13. CE-3 DOR Spectrum Frequency span = 38.4MHz, X band

  14. CVN data center structure

  15. Realtime VLBI Processing time distribution plan：

  16. Actual data turn around is 15~40 seconds

  17. Residual statistics • VLBI group delay residuals： ~ 1ns in trans-lunar orbit ~ 0.5ns in lunar orbit.

  18. Outline • Chang’E-3 overview • CVN in Chang’E-3 mission • Orbit and position determination • Summary

  19. Orbit determination results • 100×100km circumlunar orbit accuracy: 20m • 100×15km circumlunar orbit :30m • Descent trajectory: < 100m

  20. Position determination results • Get Lander position in 30 minutes after soft landing • 3D Lander position difference between by LRO (Lunar Reconnaissance Orbiter, NASA) and VLBI < 50m Lander Rover

  21. Rover positioning by same-beam VLBI • VLBI group delay, near real time • VLBI Same beam phase reference image, postprocess • VLBI phase delay, postprocess

  22. Null test by same beam phase reference image positioning Null test error: ~ 0.6 m

  23. E17 A B C D E Rover

  24. Rover position （4 ways）

  25. Outline • Chang’E-3 overview • CVN in Chang’E-3 mission • Orbit and position determination • Summary

  26. 4. Summary （1）Real-time and high accuracy VLBI has demonstrated it ability and played an important role in CE-3 Mission. （2）The lander position accuracy better than 100m. （3）The Yutu Rover relative position accuracy is ~ 1 m. （4）Fast ΔDOR and same beam VLBI hope to be used in the CE-5 rendezvous and docking and the Martian Lander / Rover tracking.

  27. Thank you for your attention!

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