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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)
The National Institute of Information and Communications Technology
Spacecraft Navigation with VLBI: Motivation
Requirments for increased accuracy of orbit control for future space missions: – For landing, orbiting, & saving energy
R&RR
R01
R02
VLBI
+
SC Astrometry
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.
VLB
I Observations Apr. MayMar.Jan. Feb. Jun.
May 22, 24, 27
June 4
Mizusawa(NAO)
Kashima(CRL)
Koganei(CRL)
Usuda(ISAS)
Yamaguchi(Yamaguchi Univ.)
Gifu(Gifu Univ.)
Kagoshima(ISAS)(uplink)
Tomakomai(Hokkaido Univ.)
Tsukuba(GSI)
AlgonquinSGL & NRCan
Japanese and Canadian VLBI Stations participated in NOZOMI VLBI observations.
ISAS,CRL,NAOJ, GSI,Gifu Univ, Yamaguchi Univ. Hokkaido Univ.SGL, NRCan supported.
The National Institute of Information and Communications Technology
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 CONS
ENSUS 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
VLBI delay model for finite distance radio source
VLBI for finite distance radio source
Normal VLBI
c
SB
Y-XB
BB
XX YY
SS
c
KB
YX RR 00
0Y0X RRK
(Fukuhisma 1993 A&A)
BB
XX YY
RX0
RY0
KK
VLBI delay model for finite distance radio source
c
cccc
VUγ
ct
ττ
eeeeg
202
220222
22
12
1
2
21
2
2)1(1
VR
wVKVR
bVwVbK
c
ccc
VUγ
ct
ττe
eeeeg
)(1
21
2
2)1(1
20
022
22
0
12wVK
VKbVwVbK
CONSENSUS MODEL (M.Eubanks 1991)
Finite Distance VLBI MODEL (Sekido & Fukushima 2003)
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
xx
y
y
CO
The National Institute of Information and Communications Technology
Observable: Phase Delay & Group delay
Frequency
Ph
ase
Band width
g:Group Delay
Phase Delay
0
g ~ 1/BW ~1 nano second (Spacecraft)
p ~ 1/RF ~1 pico second
2 n ambiguity
Orbit motion
Group Delay(Domestic Baselines)
6/4(VLBI)
6/4(R&RR)
May 27
June 4
Origin is Orbit on May 27, which was Determined by ISAS with R&RROrigin is Orbit on June 4.
Phase Delay Analysis
4 June 2003
Predicted Orbit
Pos
t F
it D
elay
Res
idu
al (
sec)
DeterminedOrbit
Summary• NOZOMI VLBI observations were perform
ed 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.
Summary• Least square solution with Predicted orbit
did not give consistent solution with determined orbit.=>Probably due to nonlinearity of observable.
=>Iterative solution will solve this problem.
• Next step:SC Astrometry => Orbit estimation
Thank you for attention.
The National Institute of Information and Communications Technology
SpaceOrbit of
NOZOMI
Apr. MayMar.Jan. Feb. Jun.
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
The National Institute of Information and Communications Technology
Spacecraft Navigation
R&RR
R01
R02
VLBI
+
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