Global GPS-VLBI Hybrid Observation Younghee Kwak
Classical VLBI vs. Space Craft Tracking plane wave front stable sources curved wave front fast moving sources Plank(2013) 2/20
Space craft tracking by VieVS2tie In VieVS, we implemented Selene same beam data processing Chang e-1 VLBI tracking data processing Glonass GNSS observations SPACECRAFT VLBI curved wave front fast moving sources Plank(2013) 3/20
GPS(or GNSS)-VLBI Hybrid Observation for Geodesy 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 5/20
IERS Combination 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 5th EOP VieVS : Earth User Orientation Workshop Parameters ICRF : International Celestial Reference Frame 6/20
A Pilot 24-h Experiment: Single & Short Baseline Baseline ~ 109km Kashima Koganei For more detail, Kwak Y et al. (2010) VLBI Type Experimental Observation 5th of GPS, VieVS JASS User Workshop 7/20 Kwak Y et al. (2011) Validation Experiment of the GV hybrid system, In Proceedings of the 20th EVGA Meeting
A Pilot 24-h Experiment: Single & Short Baseline Estimating EOP, satellite coordinates and CRF was impossible 8/20
Global Network: CONT11 sites using the same clock for both VLBI and GPS 9/20
Making Fake GPS Delays 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 Let s regard them as correlated data 10/20
Baselines of Global network HRAO-TSKB CONZ-ONSA CONZ-WTZZ HRAO-WES2 KOKB-WTZZ KOKB-ONSA CONZ-KOKB TSKB-WES2 HRAO-ONSA TSKB-WTZZ CONZ-HRAO CONZ-WES2 ONSA-TSKB HRAO-WTZZ KOKB-WES2 WES2-WTZZ KOKB-TSKB ONSA-WES2 ONSA-WTZZ 0 2000 4000 6000 8000 10000 12000 No data between CONZ TSKB No data between HRAO KOKB Baseline Length [km] Data on 19 baselines 11/20
ONSA-WTZZ 919.7km 12/20
HRAO-TSKB 11158.56km 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 14/20
Previous VieVS2tie NGS (VLBI) vie_init/ read_ngs vie_mod vie_lsm Selene same beam Chang e-1 VLBI tracking data Glonass GNSS observations Simulated data vie_init/ read_ngs_tie vie_mod_tie vie_lsm_tie Based on VieVS 2.0 solutions: source(quasars) coordinates, station coordinates, EOP, atmospheric parameters clock parameters solutions: station coordinates, EOP?, atmospheric parameters clock parameters 15/20
Current VieVS2tie NGS (VLBI) vie_init/ read_ngs vie_mod vie_lsm + GPS delays for multiple satellites vie_init/ read_ngs_tie vie_mod_tie vie_lsm_tie 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
GPS delays of the first day (11SEP15) during CONT11 Number of scans 55095 stations 7 sources 32 observations 137567 17/20
Post-fit Residuals chi-squared: 50296.4 wrms: 223.9cm (7467.9ps) 18/20
Parameterization Modeling VIE_MOD Satellite position Tidal effects EOP Final orbits Solid tide Pole tide 08C04 Estimation options VIE_LSM interval No. Clocks Pwl offset, Clock rate, quadratic term 1hr 150 6 6 ZWD 30min 343 Grad. 6hr 35*2 Antenna position Troposphere Hobiger provided VMF No gradient GPT Other settings follow VieVS basic settings EOP Station coordinate source X-&Y-pol, dut1, No nutation 24hr 6 NNR, NNT 1 / session satellite position fixed to final orbits - - 7*3 total 602 19/20
Future development of VieVS2tie NGS VLBI NGS (GPS delays) vie_init will support NGS file format vie_mod + vie_mod_tie vie_lsm + vie_lsm_tie Local tie solutions: source(quasars and satellite) coordinates, station coordinates, EOP, and common parameters, i.e. atmosphere and clock 20/20