Orbit and Clock Determination of QZS-1
Based on the CONGO Network
Peter Steigenberger, Carlos Rodriguez-Solano,
Urs Hugentobler
Technische Universität München
André Hauschild, Oliver Montenbruck
Deutsches Zentrum für Luft- und Raumfahrt, Oberpfaffenhofen
ION International Technical Meeting, Newport Beach, 30 January – 01 February 2012
Introduction
•
•
QZS-1, the first satellite of the Japanese Quasi Zenith Satellite
System (QZSS) was launched in September 2010 and declared
healthy in July 2011
Five stations of the Cooperative Network for GIOVE Observation
(CONGO) provide QZSS tracking capability
Outline
• CONGO tracking network
• GNSS processing
• Orbit determination
• Code biases
• Clock determination
JAXA
ION International Technical Meeting, Newport Beach, 30 January – 01 February 2012
CONGO Tracking Network
ION International Technical Meeting, Newport Beach, 30 January – 01 February 2012
GNSS Hardware
Javad Triumph
•
•
•
•
Leica AR25 (Rev. 3)
Trimble Zephyr 2
Prototype firmware for QZSS tracking, now integrated in
standard firmware
GPS: L1, L2, L5
QZSS: L1, L2, L5, L1 SAIF
Real-time data streaming via ntrip protocol
ION International Technical Meeting, Newport Beach, 30 January – 01 February 2012
Processing Strategy
•
•
Time period: 22 July – 7 September 2011 (day of year 173 – 250/2011)
Modified version of the Bernese GPS Software 5.0
GPS-only
QZSS orbit and clock
Precise Point Positioning
determination
Station positions
Orbit parameters
Troposphere parameters
Satellite clocks
Receiver clocks
Differential code biases
ION International Technical Meeting, Newport Beach, 30 January – 01 February 2012
Orbit Modeling
XEF, YEF, ZEF Earth-fixed system
6 Keplerian Elements
Ω
Right ascension of the
ascending node
u
argument of latitude
i
Inclination
3, 5, or 9 radiation pressure parameters
D
Satellite - Sun
Y
Along solar panel axis
X
YxD
Beutler et al. 1994
ION International Technical Meeting, Newport Beach, 30 January – 01 February 2012
Sun
Satellite
Radiation Pressure Modeling
3 parameters
5 parameters
9 parameters
ION International Technical Meeting, Newport Beach, 30 January – 01 February 2012
Orbit Quality Measures
00:00
Day boundary discontinuities
•
3D position difference between
consecutive days at midnight
2-day orbit fit RMS
•
•
Day 0
Day +1
2-day orbit fitted through positions
of 2 consecutive days
3D RMS of 2-day arc w.r.t. original
orbits
Satellite Laser Ranging residuals
•
•
independent optic technique
observed vs. computed range
between satellite and SLR stations
ION International Technical Meeting, Newport Beach, 30 January – 01 February 2012
JAXA
Orbit Validation Results
Arc
No.
DBD
Orbit Fits
Length
RPR
[cm]
[cm]
STD [cm]
Offset [cm]
3
3
24.3
3.2
36.4
-1.8
5
16.4
3.1
32.5
-1.7
9
35.3
7.6
61.9
-1.7
3
18.3
2.4
34.3
-0.4
5
16.7
3.0
33.1
+0.4
9
17.3
4.0
50.1
+34.2
3
12.7
1.5
34.2
-0.6
5
16.3
2.6
34.7
+3.4
9
10.9
2.3
39.7
+18.2
5
7
SLR Validation
ION International Technical Meeting, Newport Beach, 30 January – 01 February 2012
Orbit Validation Results
Arc
No.
DBD
Orbit Fits
Length
RPR
[cm]
[cm]
STD [cm]
Offset [cm]
3
3
24.3
3.2
36.4
-1.8
5
16.4
3.1
32.5
-1.7
9
35.3
7.6
61.9
-1.7
3
18.3
2.4
34.3
-0.4
5
16.7
3.0
33.1
+0.4
9
17.3
4.0
50.1
+34.2
3
12.7
1.5
34.2
-0.6
5
16.3
2.6
34.7
+3.4
9
10.9
2.3
39.7
+18.2
5
7
SLR Validation
ION International Technical Meeting, Newport Beach, 30 January – 01 February 2012
Orbit Validation Results
Arc
No.
DBD
Orbit Fits
Length
RPR
[cm]
[cm]
STD [cm]
Offset [cm]
3
3
24.3
3.2
36.4
-1.8
5
16.4
3.1
32.5
-1.7
9
35.3
7.6
61.9
-1.7
3
18.3
2.4
34.3
-0.4
5
16.7
3.0
33.1
+0.4
9
17.3
4.0
50.1
+34.2
3
12.7
1.5
34.2
-0.6
5
16.3
2.6
34.7
+3.4
9
10.9
2.3
39.7
+18.2
5
7
SLR Validation
ION International Technical Meeting, Newport Beach, 30 January – 01 February 2012
Inter-frequency and Inter-system Biases
Inter-frequency Bias: IFB
Inter-system Bias: ISB
Ionosphere-free Linear Combination: LC
Code delays
GPS/QZSS ISB
GPS
IFB
QZSS
IFB
C1W
Code delays for:
LC
C2W
GPS signals
C1C
LC
C2X
C5X
QZSS signals
Differential Code Bias (DCB) estimation for all stations but one (Chofu)
ION International Technical Meeting, Newport Beach, 30 January – 01 February 2012
Receiver change
Sydney
Code Bias [ns]
Maui
Code Bias [ns]
Code Bias [ns]
Code Bias [ns]
QZS-1 Differential L1/L5 Code Biases
Day of year 2011
Singapore
Tahiti
Day of year 2011
ION International Technical Meeting, Newport Beach, 30 January – 01 February 2012
Impact of Different Frequencies on Orbits
Differences between orbits computed from:
1. Ionosphere-free linear combination of L1 and L2
2. Ionosphere-free linear combination of L1 and L5
Mean: +3 cm
Mean: -3 cm
Mean: 15 cm
STD: 3 cm
STD: 12 cm
STD: 7 cm
ION International Technical Meeting, Newport Beach, 30 January – 01 February 2012
QZS-1 Satellite Clock Parameters
Orbit and clock determination
•
30 s clock estimates
3-way carrier phase approach
•
Transfer of H-maser clock
information via GPS satellite
to QZSS-capable receiver
H-Maser
GPS receiver
GPS+QZSS receiver
ION International Technical Meeting, Newport Beach, 30 January – 01 February 2012
Short-term Clock Variations
Time Interval
Period
Higher-order polynomial removed
173/2011 196/2011
15.1 min
Present in L1/L2 as well as L1/L5
clock estimates
205/2011 215/2011
15.5 min
217/2011 250/2011
13.6 min
•
30 s clock estimates of 4 Sep. 2011
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•
ION International Technical Meeting, Newport Beach, 30 January – 01 February 2012
QZS-1 3-way Carrier Phase Analysis
1 Hz data of IGS station TIDB (Tidbinbilla, Australia) and
CONGO station UNX2 (Sydney, Australia)
ION International Technical Meeting, Newport Beach, 30 January – 01 February 2012
Allan Deviations of Different Orbit/Clock Solutions
Legend
Arc
No.
Length RPR
3
3
5
9
5
3
5
9
7
3
5
9
Specification
GPS SVN62
ION International Technical Meeting, Newport Beach, 30 January – 01 February 2012
Summary and Conclusions
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QZS-1 orbits can be determined with sub-meter accuracy from
a network of 5 stations only
•
An arc length of 3 days and estimation of 5 RPR parameters
gives the best orbit and clock performance
•
GPS/QZSS differential code biases are on the few ns level
with a stability of better than 1 ns
•
Short-term variations with an amplitude of 4 cm and periods
between 13.6 and 15.5 minutes in the QZS-1 clock estimates
•
Below specifications, not relevant for most applications
•
High precision applications involving clock constraining or
predictions have to consider these variations
ION International Technical Meeting, Newport Beach, 30 January – 01 February 2012
Chofu, Singapore, Sydney
Tahiti, Maui
ION International Technical Meeting, Newport Beach, 30 January – 01 February 2012