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Global GPS-VLBI Hybrid Observation
Younghee Kwak
Classical VLBI vs. Space Craft Tracking
5th VieVS User Workshop
• plane wave front
• stable sources
• curved wave front
• fast moving sources
Plank(2013)
2/20
Space craft tracking by VieVS2tie
5th VieVS User Workshop
SPACECRAFT VLBI
• curved wave front
• fast moving sources
Plank(2013)
In VieVS, we implemented • Selene same beam data processing • Chang‘e-1 VLBI tracking data processing • Glonass GNSS observations
3/20
GPS(or GNSS)-VLBI Hybrid Observation for Geodesy
5th VieVS User Workshop 4/20
Pros & Cons of GV Hybrid System see all of satellites at one time (many data to various directions no need to slew an antenna identical clock for different techniques same signal chain cheaper
- still need local tie - multipath - additional down converter and calibrator for GPS signal into
VLBI backend - only possible for radio signal
5th VieVS User Workshop 5/20
IERS Combination
5th VieVS User Workshop
IVS ACs IGS ACs ILRS ACs IDS ACs
IVS Combination
IGS Combination
ILRS Combination
IDS Combination
ITRF & EOP & ICRF
IGS : International GNSS Service ILRS : International Laser Ranging Service IDS : International DORIS Service
ITRF : International Terrestrial Reference Frame EOP : Earth Orientation Parameters ICRF : International Celestial Reference Frame
6/20
A Pilot 24-h Experiment: Single & Short Baseline
5th VieVS User Workshop
Baseline ~ 109km
Kashima
Koganei
For more detail, Kwak Y et al. (2010) VLBI Type Experimental Observation of GPS, JASS Kwak Y et al. (2011) Validation Experiment of the GV hybrid system, In Proceedings of the 20th EVGA Meeting
7/20
5th VieVS User Workshop
A Pilot 24-h Experiment: Single & Short Baseline
Estimating EOP, satellite coordinates and CRF was impossible
8/20
5th VieVS User Workshop
Global Network: CONT11 sites using the same clock for both VLBI and GPS
9/20
Making Fake GPS Delays
5th VieVS User Workshop
• No more simulated data with only clock, zwd and white noise
• Test data based on real observation • P1, P2 range measurement by T. Hobiger (well corrected data ,O-ambiguity-antenna effect) tau = (P2 – P1)/c
10/20
Let’s regard them as correlated data
Baselines of Global network
5th VieVS User Workshop
0 2000 4000 6000 8000 10000 12000
ONSA-WTZZ
ONSA-WES2
KOKB-TSKB
WES2-WTZZ
KOKB-WES2
HRAO-WTZZ
ONSA-TSKB
CONZ-WES2
CONZ-HRAO
TSKB-WTZZ
HRAO-ONSA
TSKB-WES2
CONZ-KOKB
KOKB-ONSA
KOKB-WTZZ
HRAO-WES2
CONZ-WTZZ
CONZ-ONSA
HRAO-TSKB
Baseline Length [km]
• No data between CONZ – TSKB • No data between HRAO – KOKB • Data on 19 baselines 11/20
ONSA-WTZZ 919.7km
5th VieVS User Workshop 12/20
HRAO-TSKB 11158.56km
5th VieVS User Workshop 13/20
VieVS for GV Hybrid Observation
• VIRGO was used to analyze previous GV hybrid data • VIRGO supports only a single baseline data • Most of models are same in VIRGO and VieVS • VieVS is more stable • Especially, VieVS2tie has processed the data of space
crafts VieVS will be used for processing GV hybrid data
5th VieVS User Workshop 14/20
5th VieVS User Workshop
NGS (VLBI)
vie_init/ read_ngs
vie_init/ read_ngs_tie
vie_mod vie_mod_tie
vie_lsm vie_lsm_tie
Previous VieVS2tie
Based on VieVS 2.0
solutions: source(quasars) coordinates, station coordinates, EOP, atmospheric parameters clock parameters
solutions: station coordinates, EOP?, atmospheric parameters clock parameters
Selene same beam Chang‘e-1 VLBI tracking data Glonass GNSS observations Simulated data
15/20
5th VieVS User Workshop
… + GPS delays
for multiple satellites
NGS (VLBI)
vie_init/ read_ngs
vie_init/ read_ngs_tie
vie_mod vie_mod_tie
vie_lsm vie_lsm_tie
Current VieVS2tie
Based on VieVS 2.0
solutions: source(quasars) coordinates, station coordinates, EOP, atmospheric parameters clock parameters
solutions: station coordinates, EOP?, atmospheric parameters clock parameters
16/20
5th VieVS User Workshop
GPS delays of the first day (11SEP15) during CONT11
Number of
scans 55095
stations 7
sources 32
observations 137567 17/20
Post-fit Residuals
5th VieVS User Workshop
chi-squared: 50296.4 wrms: 223.9cm (7467.9ps)
18/20
Parameterization
VIE_MOD
Satellite position Final orbits
Tidal effects Solid tide Pole tide
EOP 08C04
Antenna position
Hobiger provided
Troposphere VMF No gradient GPT
Other settings follow VieVS basic settings
5th VieVS User Workshop
VIE_LSM interval No.
Clocks Pwl offset, Clock rate, quadratic term
1hr 150 6 6
ZWD 30min 343
Grad. 6hr 35*2
EOP X-&Y-pol, dUT1, No nutation
24hr 6
Station coordinate
NNR, NNT 1 / session
7*3
source satellite position fixed to final orbits
- -
total 602
Estimation options Modeling
19/20
5th VieVS User Workshop
NGS (GPS delays)
NGS VLBI
vie_init
vie_mod + vie_mod_tie
vie_lsm + vie_lsm_tie
Future development of VieVS2tie
will support NGS file format
solutions: source(quasars and satellite) coordinates, station coordinates, EOP, and common parameters, i.e. atmosphere and clock
Local tie
20/20
