VLBI Observation for Spacecraft Navigation (NOZOMI) – Data Processing and Analysis Status Repot

1. VLBI Observation for Spacecraft Navigation (NOZOMI) – Data Processing and Analysis Status Repot M.Sekido, R.Ichikawa,H.Osaki, T.Kondo,Y.Koyama(CRL) M.Yoshikawa,T.Ohnishi(ISAS), W.Cannon, A.Novikov (SGL), M.Berube(NRCan), NOZOMI VLBI group(CRL,ISAS,NAOJ,GSI,…)

2. VLBI R&RR + R02 R01 SC Astrometry Spacecraft Navigation with VLBI: Motivation Required for increased accuracy 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 some 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. For astrometry of S.C.Tasks to be done are • VLBI for Finite distance radio source • A New VLBI delay Model corresponding to the CONSENSUS model. • Narrow band width signal • Group delay or Phase delay • Delay Resolution: (nano/pico seconds) • Ambiguity problem • Data Processing and Analysis software • IP-sampler boards recording to HD • Software correlation & Analysis software

6. S B X Y RX0 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. VLBI delay model for finite distance radio source CONSENSUS MODEL (M.Eubanks 1991) Finite Distance VLBI MODEL (Sekido & Fukushima 2003)

8. Analysis Procedure • Compute a priori (delay, rate) (C) and partials • We modified CALC9for our use(finite VLBI). (Thanks to NASA/GSFC group for permission to use) • Extracting Observable (tg, dtg/dt,tp)(O) with software correlator. • Computing O-C and least square parameter estimation

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

10. Group Delay(Domestic Baselines) 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.

11. Closure of Phase delay (Kashima-Usuda-Tsukuba) Kashima-Usuda-Tsukuba Phase delay

12. Phase Delay Analysis 4 June 2003 Post Fit Delay Residual (sec)

13. Comparison with a priori dt/dt computed from XYZ(OD) seems to be correct, since (9000km) DS ~ 6 arc sec The OD(ISAS) is correct? True delay rate is obtainable from Doppler data. Then, is XYZ(OD) really correct? Or remaining bugs in our analysis ?.

14. Summary • NOZOMI VLBI observations were performed with domestic and intercontinental baselines. • Finite VLBI delay model was derived. • An analysis software is developed with that delay model based on CALC9. • Preliminary astrometric SC coordinates were obtained with Group/Phase delay observables. • Problem of inconsistency in the coordinates need to be solved. • Solution with full baselines have to be obtained. • Next step:SC Astrometry-> Orbit estimation

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

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

17. 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

18. VLBI R&RR + R02 R01 Spacecraft Navigation

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