Transcript VLBI Observation for Spacecraft Navigation (NOZOMI) – Data

Astrometry Observation of
Spacecraft with Phase delay
M.Sekido, R.Ichikawa, H.Osaki,
T.Kondo, Y.Koyama(NICT)
M.Yoshikawa, T.Ohnishi(ISAS),
W.Cannon, A.Novikov (SGL),
M.Berube(NRCan), NOZOMI VLBI group
(NICT,ISAS,NAOJ,GSI,Gifu Univ., Yamaguchi
Univ., Hokkaido Univ.)
Spacecraft Navigation
with VLBI: Motivation
Precise orbit determination is requested for
precise landing, orbiting, & saving energy in
maneuver :
VLBI
R&RR
+
R01
R02
SC Astrometry
NOZOMI’s Earth Swing-by
• Japanese first Mars mission NOZOMI was
observed during the period between two earth
swing-bys.
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)
Kagoshima(ISAS)
(uplink)
Kashima
(CRL)
VLBI delay model for finite
distance radio source
Normal VLBI
B  X-Y
VLBI for finite distance
radio source
BK

c
BS

c
S
RX0
B
X
Y
R 0X  R 0Y
K
R0 X  R0Y
RX0
K
X
(Fukuhisma 1993 A&A)
B
Y
Relativistic VLBI delay model for
finite distance radio source
CONSENSUS MODEL (M.Eubanks 1991)








2
K0 b 
Ve  2Ve  w 2  Ve  b 
K 0  Ve

t g 
1  (1  γ)U 

2
2
1 
c
2c
2
c
c





τ 2  τ1 

K 0  (Ve  w 2 )
1
c




Finite Distance VLBI MODEL (Sekido & Fukushima 2004)

 
 
 

 

2




Ve  2Ve  w 2
Ve  b
V2 K  Ve  2w 2
K b
1  R 02 
t g 

1  (1  γ)U 

2
2

c 
c
2c
2c
c


τ 2  τ1 
  2



V2  K  B(  2   022 ) 
1  R 02 
1 
2 


c
2
R
(
1


)
02
02






Analysis Procedure
• C: Compute a priori (delay) and
partials
– We modified CALC9 for our
use(finite VLBI).
(Thanks to NASA/GSFC group)
• O:Extracting Observable (p)
with software correlator.
• O-C: least square parameter
estimation
True Orbit

x
Apiori Orbit
y  O  C


y 
 x
x
Group Delay(Post-fit Residual)
~100 nano sec.
Signal type from Spacecraft
quasor
(frq.)
~1MHz
Phase delay
Closure phase delay
Tomakomai
Yamaguchi
Gifu
As result of phase connection,
Very precise delay observable
was obtained over 24 hours.
(June 4th experiments)
Phase delay solution’s track
by adding baselines (June 4th)
Origin is
determine
d orbit with
R&RR
6/4
Tobs
Nstn
Nbase
26 h
7
21
Including Algonquin
Baseline
Summary
• VLBI observations of spacecraft were performed
with domestic and intercontinental baselines.
• Relativistic Finite VLBI delay model and analysis
software were developed and implemented based
on CALC9.
• Phase delay was derived in precision of 20 pico sec
for long time span.
• SC coordinates estimated by VLBI agreed with that
of R&RR when Determined (R&RR) orbit was used
as a priori.
• Next problem is SC coordinates started from
Predicted orbit.