ASTROMETRY OBSERVATION OF SPACECRAFT WITH VERY LONG BASELINE INTERFEROMETRY A STEP OF VLBI APPLICATI

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ASTROMETRY OBSERVATION OF SPACECRAFT WITH VERY
LONGBASELINE INTERFEROMETRY---- A STEP OF VLBI
APPLICATION FOR SPACECRAFT NAVIGATION ----

• 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)

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Spacecraft Navigation with VLBI Motivation

• Requirments for increased accuracy of orbit
  control 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 a 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 delay mode for Finite distance radio source
• A New VLBI delay Model corresponding to the
  CONSENSUS model.
• Narrow band width of the 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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Finite-Infinite Delay Difference
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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.
• III. Computing O-C and least square parameter
  estimation

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Observable Phase Delay Group delay
2p n ambiguity
tgGroup Delay
Dtp 1/RF 1 pico second
Phase
Phase Delay
Dtg 1/BW 1 nano second
(Spacecraft)
Band width
0
Frequency
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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
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Estimated Coordinates
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Summary

• NOZOMI VLBI observations were performed with
  domestic and intercontinental baselines.
• Formula for Finite VLBI delay model was derived.
• An analysis software is developed with that
  delay model based on CALC9.
• Astrometric SC coordinates were obtained with
  Group/Phase delay observables.

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Summary

• Least square solution with Predicted orbit did
  not give consistent solution with determined
  orbit.
• gtProbably due to nonlinearity of observable.
• gtIterative solution will solve this problem.
• Next step
• SC Astrometry gt Orbit estimation

Thank you for attention.
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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

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