1. ESWW3, 13-17 November, Brussels Folie 1 On developing space weather services for the end users of GNSS N. Jakowski German Aerospace Center (DLR), Institute of Communications and Navigation, Neustrelitz, Germany

2. ESWW3, 13-17 November 2006, Brussels Folie 2 OUTLINE Introduction Space weather impact on GNSS Monitoring the ionosphere for establishing a space weather service Ground based Space based Data processing & service provision Service data use Conclusions

3. ESWW3, 13-17 November 2006, Brussels Folie 3 Space Weather Environment Space weather impacts the functionality of Global Navigation Satellite Systems (GNSS) by damaging transmitting satellites and/or degrading the GNSS signals travelling through the ionized part of the Earth‘s atmosphere (ionosphere/plasmasphere) to the user. GNSS satellite

4. ESWW3, 13-17 November 2006, Brussels Folie 4 Plasma Environment Control Structure and dynamics of the ionosphere/plasmasphere are strongly controled by the solar radiation and the solar wind and coupled with other geo-spheres such as the magnetosphere, thermosphere, lower atmosphere, hydro- and lithosphere Electron density ¬ ¬ ¬ 0.5 1.0 1.5 10 12 m -3 nene

5. ESWW3, 13-17 November 2006, Brussels Folie 5 Ionospheric impact on navigation and positioning Ionospheric perturbations will also impact GALILEO

6. ESWW3, 13-17 November 2006, Brussels Folie 6 Storm on 29 October 2003 / Polar TEC Polar TEC on 29 October 2003 derived from IGS ground based measurements Map resolution  ime : 10 min Latitude: 2.5 deg Longitude: 7.5 deg

7. ESWW3, 13-17 November 2006, Brussels Folie 7 Space weather event on 29 October 2003 GPS-service outage 06 UT 09 UT 07 UT08 UT 10 UT 11 UT Polar TEC network performance The storm develops at high latitudes already before noon indicating the potential of forecasting UT Begin Tracked Processed Solved Jakowski, N., Stankov, S.M., Klaehn, D., Schlueter, S., Beniguel, Y., Rueffer, J. (2004): Operational service for monitoring and evaluating the space weather impact on precise positioning. Proc. European Navigation Conference GNSS-2004, 16-19 May 2004, Rotterdam, The Netherlands WAAS service interrupted in US; GPS receiver outages Finland, Netherlands Military communications impacted (HF/UHF SATCOM)/OTH Loran C station in Newfoundland had interference.

8. ESWW3, 13-17 November 2006, Brussels Folie 8 SW problem at user level Fixing time at user level to solve phase ambiguities may increase to hours, i.e. practically no high precision solution achieved within this time, i.e. correction information cannot be provided to users → user refuses to pay Measurement must be repeated → economical loss GNSS perturbation of precise positioning Local time / hrs Time to fix / sec Error range Ionosphere model Real signal User Reference station Ionosphere impact Phase ambiguity fixing is not possible if signal perturbation exceeds the error bounds → No solution at user level achieved Correction from GNSS service provider

9. ESWW3, 13-17 November 2006, Brussels Folie 9 Ionospheric scintillations Small scale ionospheric irregularities of plasma density (turbulences, bubbles) cause interfering rays This leads to a high variability of GNSS signal strength (radio scintillations) Severe scintillations cause problems in signal use or even loss of lock (no signal availability) Regions where scintillations most frequently occur: high latitudes low latitudes 0,00 0,10 0,20 0,30 0,40 0,50 2,893,32 3,72 4,12 4,52 4,92 5,325,726,12 6,526,94 Time (hour) s4 sigma phi PRN 24 Allsat GmbH reports about 25% loss of data due to ionospheric perturbations in Jemen 30/10/03

10. ESWW3, 13-17 November 2006, Brussels Folie 10 Space Weather Impact on Network Monitoring Integrity on 25 July 2004 Performance of the GPS Reference network of Allsat GmbH Hannover degrades during the ionospheric storm on 25 July 2004 Different effects in different network areas over Germany  Propagation of perturbation from high to mid-latitudes Provision of ionospheric now- and forecast information to users  Information to European users via the Space Weather European Network (SWENET) NW MW SW 19:00 UT MW 1X1 deg grid resolution SWACI product: TEC rate SW 16:30 UT NW

11. ESWW3, 13-17 November 2006, Brussels Folie 11 Solar flare effect on 28 October 2003 over Europe - TEC rel Strong solar flare on 28 October 2003 at 11:05 UT Total irradiance of the sun enhanced within a few minutes by 267 ppm TEC data processing indicates loss of data at numerous GPS links The number of usable GPS links for TEC processing was reduced rapidly from more than 30 to only 7

12. ESWW3, 13-17 November 2006, Brussels Folie 12 Latitudinal dependency of the flare induced TEC jump on 28 October 2003 Strong latitudinal dependency of the height of the TEC jump observed, up to 20 TECU or 3.2 m at L1 ! The CME associated with this flare is larger than the Sun itself causing strong perturbations after reaching the Earth on 29/30 October 2003 Jakowski N., B. Fichtelmann, and A. Jungstand, Solar activity control of ionospheric and thermospheric processes, J. Atmos. Terr. Phys., 53, 1125-1130, 1991

13. ESWW3, 13-17 November 2006, Brussels Folie 13 Correction of nonlinear refraction effects in precise positioning applications Ionospheric data service can provide input data for higher order corrections for precise positioning applications O Plasmasphere Ionosphere TXTX RXRX B measurement phase delay ray path error bending error True Range Linear error ~TEC 2 nd order error magnetoionic TEC map User

14. ESWW3, 13-17 November 2006, Brussels Folie 14 Ground and space based monitoring by GNSS Monitoring of the Ionosphere by: - GNSS Ground stations DLR: over a full solar cycle since 1995 Europe North pole area South pole area - LEO Satellites carrying GNSS receivers onboard DLR: CHAMP (GRACE, TerraSAR-X) Radio occultation Topside reconstruction - Non-GNSS based techniques e.g. : vertical sounding network (DIAS), in situ measurements on spacecrafts 2 1 3 CHAMP 1 2 3

15. ESWW3, 13-17 November 2006, Brussels Folie 15 GPS sounding of the Ionosphere onboard CHAMP GPS Satellite CHAMP CHAMP Orbit Radio Signal

16. ESWW3, 13-17 November 2006, Brussels Folie 16 SWACI products – Space based measurements (CHAMP) Assimilation of GPS measurements into a model Operational reconstruction of the electron density in the plane of the CHAMP revolution (15-16 3D maps/day) Jakowski, N. Wehrenpfennig, A., Heise, S., Reigber, C. and Lühr, H., GPS Radio Occultation Measurements of the Ionosphere on CHAMP: Early Results, Geophysical Research Letters, 29, No. 10, 10.1029/2001GL014364, 2002b Ionospheric Radio occultation (IRO) Automatic retrieval of vertical electron density profiles (up to 150 profiles per day) Heise, S., Jakowski, N., Wehrenpfennig, A., Reigber, C., Lühr, H., Sounding of the Topside Ionosphere/Plasmasphere Based on GPS Measurements from CHAMP: Initial Results, Geophysical Research Letters, 29, No. 14, 10.1029/2002GL014738, 2002

17. ESWW3, 13-17 November 2006, Brussels Folie 17 Merging of local/regional information with global data sets needed for future services (external / internal) Global data sets provide optimal boundary conditions for local /regional reconstructions Local/regional reconstructions enable highest accuracy Global TEC Regional Local LBAS Global TEC map on 01/01/99 at 13:00 UT Global TEC map source: IGS, CODE, Bern transition region Reconstruction of regional AND global ionosphere needed for getting reliable information, data assimilation methods Local / regional / global monitoring of the ionosphere

18. ESWW3, 13-17 November 2006, Brussels Folie 18 DLR- infrastructure for SWACI- service development COSMIC-Empfänger EVNet NTrip: Javad / RTCM-RTK Data SWACI is supported by the state government of Mecklenburg- Vorpommern Follow-up project of the former ESA supported SDA SWIPPA IGS Ascos EUREF SAPOS SWACI GFZ IAP SEC GNSS data Non-GNSS data LEO http://w3swaci.dlr.de

19. ESWW3, 13-17 November 2006, Brussels Folie 19 SWACI - web portal ( http://w3swaci.dlr.de ) Different types of users Consortium partners Commercial Non-Commercial Public Ground based data update: 5 minutes Space based data update according to the data dumps from CHAMP

20. ESWW3, 13-17 November 2006, Brussels Folie 20 Space Weather service - GNSS user groups tourism aviation Space Weather Service Precise Positioning accuracy in (sub) cm range Standard service accuracy in m range Safety of Life Highest priority: system mut operate within system specification MOPS: 99.99999 % Science Highest accuracy of physical parameters requested machine control Ionospheric model, NRT Accurate reconstruction, post processing Ionospheric threats, NRT, forecasts Accurate TEC, NRT, forecasts

21. ESWW3, 13-17 November 2006, Brussels Folie 21 Detection / monitoring of ionospheric threats Definition of a proper perturbation index on international level (e.g. COST 296 task group has been established) Continuous computation of regional perturbation indices Provision of the index (indices) to users in near real time streaming mode The perturbation índex must be easy to handle for users and well suited for forecasting

22. ESWW3, 13-17 November 2006, Brussels Folie 22 Short Term Prediction of perturbations in the Regional / Local Ionosphere High latitude latitudinal gradient index is well correlated with the performance of GPS reference networks Systematic investigation of relationships with other space weather parameters required Development of a prediction model Transformation of predicted ionospheric parameters into user terms 60°N 40°N Delayed degradation of the ascos network Potential for prediction Network Monitoring Integrity Source: Allsat GmbH 7 November 2004 Geomagnetic Index Dst Perturbation index North-Germany

23. ESWW3, 13-17 November 2006, Brussels Folie 23 Probability of ionospheric perturbations (geomagnetically based) Strong coupling between geomagnetic and ionospheric storms Geomagnetic indices are choosen as a preliminary indicator Future: Ionospheric perturbation index should give a more accurate information for GNSS users Degree of perturbation KpNumber of events from 1994-2004 Meteorological phenomena moderate6507wind severe7183storm very strong841thunderstorm extreme94tornado

24. ESWW3, 13-17 November 2006, Brussels Folie 24 Conclusions Reliable now- and forecast services based on real-time ionosphere monitoring / modeling and related space weather observations (regional and global) are needed in the future, i.e. also for GALILEO. Precise Positioning SW services help to avoid useless efforts, e.g. repeating measurements, mid-term forecasts (24 ahead helpful for planning work) SW services helps to achieve high accuracy with less dense reference networks (WARTK) Accurate single point positioning possible by reducing the total error budget (among them ionospheric errors) Safety of Life (SoL) applications SW service focuses on detection of integrity threats (moving ionization fronts, bubbles) SW services require reliable short term forecasts of threats