IDS workshop Venice Italy 25 26 September 2012

IDS workshop, Venice, Italy, 25 -26 September 2012 Tropospheric parameters from DORIS in comparison to other techniques during CONT campaigns Johannes Böhm(1), Kamil Teke(1, 2), Pascal Willis(3, 4), Tobias Nilsson(1), Peter Steigenberger(5) (1) Vienna University of Technology, Institute of Geodesy and Geophysics, Vienna, Austria (2) Hacettepe University, Department of Geomatics Engineering, Ankara, Turkey (3) Institut Géographique National, Direction Technique, Saint-Mandé, France (4) Institut de Physique du Globe de Paris, PRES Sorbonne Paris Cité, Paris, France (5) Institut für Astronomische und Physikalische Geodäsie, Technische Universität München, Germany

The aims of our study are • Quantify agreement of troposphere estimates • Figure out site and technique specific irregularities

Very Long Baseline Interferometry k 0 • Group delay determined by correlator • Ionospheric corrections by S - and X-band observations • c = b WSNP k 0 c Earth orientation parameters (EOP) b

Troposphere delays S G Pressure, temperature, and humidity from numerical weather models

Troposphere delays DL(e) = Dz · m(e) = Dzh · mh(e) + Dzw · mw(e) + gradients Dz e DL

CONT Sessions CONT 02 16 -31 October 2002 CONT 05 12 -27 September 2005 CONT 08 12 -27 August 2008 CONT 11 15 -30 September 2011

Very Long Baseline Interferometry (VLBI) • Vienna VLBI Software (Vie. VS): - Software Vie. VS. - Fixed to ICRF 2. - NNT/NNR on ITRF 2008. - A priori ZHD from surface pressure. - No a priori gradients. - VMF 1, above 5°. - Gradient MF: Chen and Herring, 1997. - No elevation-dependent weighting. - Relative constraints for ZTDs are 1. 6 cm after 1 hour. - Relative constraints for gradients are 0. 12 mm after 6 hours. - 60 minutes for ZTDs, and 360 for gradients.

Global Positioning System (GPS) • Center for Orbit Determination in Europe (CODE) - Bernese GPS software. - NNR on IGS 05. - 120 minutes interval for ZTDs and 24 h for gradients. - VMF 1, 3° + elevation-dependent weighting. - No constraints for zenith delays and gradients.

Doppler Orbitography and Radio Positioning Integrated by Satellite (DORIS) • Institut Géographique National (IGN) - Software is GIPSY/Oasis. TRF is fixed to ign 09 d 02. VMF 1, 10°. DORIS reset at no regular interval. It is reset at start of pass and only if the previous reset is 20 minutes before or earlier. - ZTD epochs interpolated linearly from the irregular epochs to 60 minutes (epochs at UTC integer hours). - No interpolation between the data gaps (no estimates from DORIS between 6 hours) larger than 360 minutes. - Co-located sites are Ny-Ålesudn (spjb), Kokee Park (kolb), Hartebeesthoek (hbmb).

Water Vapor Radiometer (WVR) - Slant wet delays inferred from measurements of the sky brightness temperature at about 22 GHz and 31 GHz. - ZWDs and gradients obtained by a least-squares fit. 30 minutes estimation interval for ZWDs and 120 minutes estimation intervals for troposphere gradients. - ZHDs calculated from surface pressure measurements at the VLBI antenna. - Cut off 20°. - Data acquired during rain removed. - Co-located sites: Wettzell, Tsukuba, and Onsala.

Numerical Weather Model (NWM) • European Centre for Medium-Range Weather Forecasts (ECMWF). NWM ECMWF The regions for which the models provide data Spatial resolution Time Resolution (hours) Number of levels at each profile Troposphere gradients estimated ? Global 0. 25° 6 21 YES

Summary of the data used for the comparisons Technique Zenith wet/total delay VLBI-Vie. VS ZWD, ZTD DORIS-IGN ZTD GPS-CODE ZTD ECMWF ZWD, ZTD WVR ZWD Estimation interval of gradients of zenith delay 1 hour 6 hours (total gradients) per satellite pass 1 day (total gradients) 1 hour (total gradients) 6 hours (total gradients) 1 hour 6 hours (wet gradients)

Ny-Ålesund co-located site (Vertical troposphere between antennas) VLBI antenna reference point REFERENCE HEIGHT (87. 79 m) Atmosphere DORIS, SPJB height (53. 06 m) Δh = 34. 73 m Earth Troposphere ties calculated based on 6 -hourly ECMWF!

Total (in red) and hydrostatic (in black) troposphere ties at NY-Ålesund (Δh=35 m) CONT 08 CONT 11

Total (in red) and hydrostatic (in black) troposphere ties at Hartebeesthoek (Δh=144 m) CONT 08 CONT 11

Troposphere ZTD of the co-located site Hartebeesthoek during CONT 02

Troposphere ZTD of the co-located site Hartebeesthoek during CONT 05

Troposphere ZTD of the co-located site Hartebeesthoek during CONT 08

Troposphere ZTD of the co-located site Hartebeesthoek during CONT 11 Median formal errors at Hartebeesthoek: DORIS: 5. 1 mm VLBI: 4. 2 mm GNSS: 1. 3 mm

Troposphere ZTD of the co-located site Kokee during CONT 02

Troposphere ZTD of the co-located site Kokee during CONT 05

Troposphere ZTD of the co-located site Kokee during CONT 08

Troposphere ZTD of the co-located site Kokee during CONT 11

Troposphere ZTD of the co-located site Ny-Ålesund during CONT 02

Troposphere ZTD of the co-located site Ny-Ålesund during CONT 05

Troposphere ZTD of the co-located site Ny-Ålesund during CONT 08

Troposphere ZTD of the co-located site Ny-Ålesund during CONT 11

Hartebeesthoek ZTD std. dev. and biases w. r. t. VLBI and GNSS

41 mm 37 mm Kokee ZTD std. dev. and biases w. r. t. VLBI and GNSS

Ny-Ålesund ZTD std. dev. and biases w. r. t. VLBI and GNSS

Troposphere east gradients of the co-located site Ny-Ålesund during CONT 11 Median formal errors at Ny-Ålesund : DORIS: 0. 15 mm VLBI: 0. 20 mm GNSS: 0. 09 mm

Ny-Ålesund east gradients std. dev. and biases w. r. t. VLBI and GNSS

Troposphere north gradients of the co-located site Ny-Ålesund during CONT 11 Median formal errors at Ny-Ålesund : DORIS: 0. 13 mm VLBI: 0. 23 mm GNSS: 0. 09 mm

Ny-Ålesund north gradients std. dev. and biases w. r. t. VLBI and GNSSS

Troposphere east gradients of the co-located site Kokee during CONT 11

Troposphere north gradients of the co-located site Kokee during CONT 11

Troposphere east gradients of the co-located site Hartebeesthoek during CONT 11

Troposphere north gradients of the co-located site Hartebeesthoek during CONT 11

ZTD mean std. dev. and biases w. r. t. VLBI during CONT 11 Total number of common epochs with VLBI during CONT 11 GNSS: 3193 DORIS: 1095 ECMWF: 644 CRe. SS: 114

ZTD mean std. dev. and biases w. r. t. VLBI during CONT 02, 05, 08, and 11 21. 3 mm CONT 02 HBKB : 202 KOKA : 200 SPIB : 296 total: 698 HBKB : 40 KOLB : 87 SPJB : 243 total: 370 CONT 08 CONT 11 20. 6 mm HBMB : 171 KOLB : 152 SPJB : 238 total: 561 Number of common epochs with VLBI during CONT 05 HBMB : 254 KOLB : 278 BADB : 282 SPJB : 281 total: 1095

Conclusions

Thanks for your attention.