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Astrometric VLBI Observation of Spacecraft with Phase Delay

The National Institute of Information and Communications Technology. 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),

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Astrometric VLBI Observation of Spacecraft with Phase Delay

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  1. The National Institute of Information and Communications Technology 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)

  2. VLBI R&RR + R02 R01 SC Astrometry Spacecraft Navigation with VLBI: Motivation Requirments for increased accuracy of orbit control for future space missions: • For landing, orbiting, & saving energy

  3. Jun. Jan. Feb. Mar. Apr. May May 22, 24, 27 VLBI Observations June 4 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.

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

  5. 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. S B X Y RY0 RX0 K B X Y VLBI delay model for finite distance radio source Normal VLBI VLBI for finite distance radio source (Fukuhisma 1993 A&A)

  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. III. Computing O-C and least square parameter estimation 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 (tg, tp)(O) with software correlator.

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

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

  12. Observable: Phase Delay & Group delay 2p n ambiguity tg:Group Delay Dtp ~ 1/RF ~1 pico second Phase Phase Delay Dtg ~ 1/BW ~1 nano second (Spacecraft) Band width 0 Frequency

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

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

  15. Estimated CoordinatesComparison 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. Thank you for attention.

  18. Orbit of NOZOMI Jun. Jan. Feb. Mar. Apr. May Space

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

  20. 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. VLBI R&RR + R02 R01 Spacecraft Navigation

  22. Observation：IP-VLBI Sampler board K5VLBISystem • Sampling rate:40k-16MHz • Quantization bit: 1-8bit • 4ch/board • 10MHz,1PPS inputs

  23. Post Fit Delay Residual (sec) PredictedOrbit Determined Orbit Phase Delay Analysis 4 June 2003

  24. Predicted Orbit Determined Orbit Estimated CoordinatesComparison with R&RR measurement

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