1. Astrometric VLBI Observation of Spacecraft with Phase Delay M.Sekido, R.Ichikawa,H.Osaki, T.Kondo,Y.Koyama (National Institute of Information and Communications Technology :NICT,Japan) M.Yoshikawa,T.Ohnishi(ISAS,Japan), W.Cannon, A.Novikov (SGL,Canada), M.Berube (NRCan,Canada), and NOZOMI VLBI group(NICT,ISAS,NAOJ,GSI,Gifu Univ. Yamaguchi Univ., Hokkaido Univ., Japan) The National Institute of Information and Communications Technology

2. Spacecraft Navigation with VLBI: Motivation Requirments for increased accuracy of orbit control for future space missions: –For landing, orbiting, & saving energy R&RR R 01 R 02 VLBI + SC Astrometry

3. The National Institute of Information and Communications Technology NOZOMI’s Earth Swing-by NOZOMI was launched in July 1998. Due to some troubles, new orbit plan with Earth swing-by was proposed. R&RR observations were difficult in a period. VLBI Observations Apr.MayMar.Jan.Feb. Jun. May 22, 24, 27 June 4

4. Mizusawa (NAO) Kashima (CRL) Koganei (CRL) Usuda (ISAS) Yamaguchi (Yamaguchi Univ.) Gifu (Gifu Univ.) Kagoshima(ISAS) (uplink) Tomakomai (Hokkaido Univ.) Tsukuba (GSI) Algonquin SGL & NRCan Japanese and Canadian VLBI Stations participated in NOZOMI VLBI observations. ISAS,CRL,NAOJ, GSI,Gifu Univ, Yamaguchi Univ. Hokkaido Univ. SGL, NRCan supported.

5. The National Institute of Information and Communications Technology Tasks to be done for S.C.astrometry are Constructing VLBI delay mode for Finite distance radio source –Including relativity and curvature of wavefront Writing Data Processing and Analysis software –Observation with IP-sampler boards recording to HD –Software correlator Narrow band signal –Analysis software Group delay or Phase delay –Delay Resolution: (nano/pico seconds) –Ambiguity problem

6. VLBI delay model for finite distance radio source VLBI for finite distance radio source Normal VLBI B XY S (Fukuhisma 1993 A&A) B XY R X0 R Y0 K

7. Relativistic VLBI delay model for finite distance radio source CONSENSUS MODEL (M.Eubanks 1991) Finite Distance VLBI MODEL (Sekido & Fukushima 2003)

8. Finite-Infinite : Delay Difference

9. The National Institute of Information and Communications Technology Analysis Procedure for SC Astometory I. Compute a priori (delay, rate) (C) and partials –We modified “CALC9” for our use(finite VLBI). ( Thanks to GSFC/ NASA group for permission to use) II. Extracting Observable (  g,  p )(O) with software correlator. III. Computing O-C and least square parameter estimation

10. Group Delay (Post-fit Residual) Rate residual Delay Residual

11. Orbit motion Estimated Coordinates (Group Delay) 6/4(VLBI ) 6/4(R&RR) May 27 June 4 Origin is Orbit on May 27, which was Determined by ISAS with R&RR Origin is Orbit on June 4.

12. The National Institute of Information and Communications Technology Observable: Phase Delay & Group delay Frequency Phase Band width  g:Group Delay Phase Delay 0  g ~ 1/BW ~1 nano second (Spacecraft)  p ~ 1/RF ~1 pico second 2  n ambiguity

13. Phase delay A C B Closure of Phase delay (Kashima-Usuda-Tsukuba) Kashima-Usuda-Tsukuba

14. Phase Delay Post fit residual Post Fit Delay Residual (sec)

15. Estimated Coordinates Comparison with R&RR measurement

16. Summary VLBI observations for spacecraft were performed with domestic and intercontinental baselines. Formula for Finite VLBI delay model and analysis software was developed by using CALC9. Astrometric SC coordinates were obtained with Group/Phase delay observables by absolute astrometry. Nest step: –Improve coordinates accuracy by using differential VLBI technique.

17. The National Institute of Information and Communications Technology Thank you for attention.

18. The National Institute of Information and Communications Technology Space Orbit of NOZOMI Apr.MayMar.Jan.Feb. Jun.

19. Group Delay (Range signal) Closure Observation mode = 2MHz, 2bit

20. The National Institute of Information and Communications Technology Spacecraft Navigation with VLBI : Motivation Required for increased accuracy for future space missions: –For landing, orbiting, & saving energy JPL/NASA has been employed –Japanese Space Agency ( ISAS+NASDA=JAXA ) NOZOMI(Japanese Mars Explorer) –Needs to support orbit determination with VLBI. Mission as our own Project

21. The National Institute of Information and Communications Technology Spacecraft Navigation R&RR R 01 R 02 VLBI +

22. The National Institute of Information and Communications Technology Observation ： IP-VLBI Sampler board Sampling rate:40k-16MHz Quantization bit: 1-8bit 4ch/board 10MHz,1PPS inputs K5 VLBI System

23. The National Institute of Information and Communications Technology

25. Phase Delay Analysis 4 June 2003 Predicted Orbit Post Fit Delay Residual (sec) Determined Orbit

26. Estimated Coordinates Comparison with R&RR measurement Determined Orbit Predicted Orbit