VLBI Observation for Spacecraft Navigation (NOZOMI)

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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,G
  SI,)

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Spacecraft Navigation with VLBI Motivation

• Required for increased accuracy for future space
  missions
• For landing, orbiting, saving energy

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NOZOMIs Earth Swing-by

• NOZOMI was launched in July 1998.
• Due to some troubles, new orbit plan with Earth
  swing-by was proposed.
• RRR observations were difficult in some period

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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)
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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

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VLBI delay model for finite distance radio source
VLBI for finite distance radio source
Normal VLBI
(Fukuhisma 1993 AA)
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VLBI delay model for finite distance radio source
CONSENSUS MODEL (M.Eubanks 1991)
Finite Distance VLBI MODEL (Sekido Fukushima
2003)
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Analysis Procedure

• Compute a priori (delay, rate) (C) and partials
• We modified CALC9 for 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

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Group Delay(Post-fit Residual)
Rate residual
Delay Residual
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Group Delay(Domestic Baselines)
6/4(RRR)
6/4(VLBI)
June 4
Orbit motion
May 27
Origin is Orbit on May 27, which was Determined
by ISAS with RRR
Origin is Orbit on June 4.
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Phase delay
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Phase Delay Analysis
4 June 2003
Post Fit Delay Residual (sec)
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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 ?.
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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 stepSC Astrometry-gt Orbit estimation

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Space
Orbit of NOZOMI
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Group Delay(Range signal)
Closure
Observation mode 2MHz, 2bit
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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 (ISASNASDAJAXA)
• NOZOMI(Japanese Mars Explorer)
• Needs to support orbit determination with VLBI.
• Mission as our own Project

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Spacecraft Navigation
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ObservationIP-VLBI Sampler board
K5 VLBI System

• Sampling rate40k-16MHz
• Quantization bit 1-8bit
• 4ch/board
• 10MHz,1PPS inputs