IGS Workshop 2008 The Galileo Ground Mission Segment Performances Francisco Amarillo-Fernandez, Massimo Crisci, Alexandre Ballereau John Dow, Martin Hollreiser, Joerg Hahn, Jean-Luc Gerner, European Space Agency

IGS Workshop 2008 CONTEXT  Presented performance:  Refer to the Galileo Mission Segment (range domain)  Are the result of the Segment Critical Design Review (CDR) experimentation process  Are derived from an experimental platform hosting replicas of the operational algorithms for both the Navigation and Integrity Functions  Are derived in synthetic scenarios based on conservative assumptions  Are confirmed in real scenarios for the Navigation Function

IGS Workshop 2008 Introduction (I). Galileo Ground Mission Segment. Functional Overview  Determines and uplinks the navigation data for each Galileo satellite:  Orbit description, via 15 orbital parameters  OS on-board clock description, via 3 parameters  SoL on-board clock description, via 3 parameters  TEC global model input parameters  Differential group delay between the two OS pilot signals  Differential group delay between the two SoL pilot signals  Galileo to GPS time offset  SoL Signal-In-Space- Accuracy (SISA)  Determines and uplinks the integrity data for the Galileo constellation:  Integrity table including the Signal-In-Space-Monitoring-Accuracy (SISMA)  Integrity alarms

IGS Workshop 2008 Introduction (II). Definitions  Signal-in-Space Accuracy (SISA) “SISA is a prediction of the minimum standard deviation (1-sigma) of the unbiased Gaussian distribution which overbounds the signal-in-space error (SISE) predictable distribution for all possible user locations within the satellite coverage area”  Signal-in-Space Monitoring Accuracy (SISMA) “SISMA shall be a prediction of the minimum standard deviation (1- sigma) of the unbiased Gaussian distribution which overbounds the error of the estimation of SISE as determined by the integrity monitoring system”

IGS Workshop 2008 Part I. Tracking Stations Performance “Initial Reference” quality expectations “Current” quality expectations Code tracking error (excluding multipath) Between 6 and 23 cm E5a-Q : Between 6 and 23 cm Between 6 and 23 cm E5b-Q : Between 6 and 23 cm Between 15 and 41 cm E1-C : Between 15 and 41 cm Assumptions: 1- Minimum satellite EIRP 2- No ionospheric scintillation 3- Maximum in band interference 4- Error dependency on satellite elevation (from 5º to 90º) 5- Tracking on pilot 6- Root mean square value Between 9 and 31 cm E5a-Q : Between 9 and 31 cm Between 9 and 31 cm E5b-Q : Between 9 and 31 cm Between 13 and 41 cm E1-C : Between 13 and 41 cm Carrier tracking error (excluding multipath) < 2.5 mm Assumptions as indicated for the code tracking error (excluding multipath) Between 2 and 4 mm Code tracking error due to multipath Between 10 and 100 cm Assumptions: 1- Worst multipath delay 2- Average multipath phase 3- Range obeys to error dependency versus the D/U ratio. 4- Applicable to the following signals E5a-Q, E5b-Q, E1-C 5- Tracking on pilot 6- Root mean square value Between 15 and 140 cm Carrier tracking error due to multipath Between 0.7 and 10 mm Assumptions as indicated for the code tracking error (due to multipath) Between 0.8 and 11 mm

IGS Workshop 2008 Part II. Orbit & Clock Determination Performance “Initial Reference” quality expectations “Current” quality expectations Predicted Clock and Orbit UERE < 130 cm Assumptions: 1- 95% percentile 2- End of navigation message applicability period (100 minutes) 3- Worst satellite 4- Worst user location (infinity velocity approach) 5- Masking angle 0º 6- Worldwide network 40 stations < 70 cm Not in eclipse < 70 cm < 78 cm In eclipse < 78 cm Predicted Clock and Orbit First derivative of the UERE < 10 mm/s Assumptions: as above < 4.1 mm/s Not in eclipse < 4.1 mm/s < 4.3 mm/s In eclipse < 4.3 mm/s Restituted Orbit Error < 10 cm Assumptions: 1- 67% percentile 2- Worst satellite 3- Average over the arc duration 4- Worldwide network 40 stations < 12 cm Restituted Clock Error < 0.3 ns Assumptions: 1- 67% percentile 2- Worst satellite 3- Average over the arc duration 4- Worldwide network 40 stations < 0.5 ns

IGS Workshop 2008 Part II (continuation-I) Ranging accuracy (95%) versus satellite and experimentation batch DAY

IGS Workshop 2008 Part III. GTTO Offset Determination Performance “Initial Reference” quality expectations “Current” quality expectations SoL SISA Upper bound < 85 cm Assumptions: 1- 68% percentile (by definition) 2- Any time within navigation message applicability period (100 min) 2- Under-bounding probability: 1E Upper-bound unavailability probability of: 1E Worst satellite 5- Galileo over-bounding 6- Signal-In-Space in fault free 7- After convergence 8- Worldwide network: 40 stations < 46 cm Not in eclipse < 46 cm < 54 * cm In eclipse < 54 * cm * Note: currently under detailed assessment for eclipse condition Part II (continuation-III) “Initial Reference” quality expectations “Current” quality expectations Galileo to GPS Time Offset < 5 ns Assumptions: 1- 95% percentile 2- Average error over 24 hours < 10.4 ns

IGS Workshop 2008 Part IV. Group Delay Determination Performance “Initial Reference” quality expectations“Current” experimentation results Broadcast Group Delay < 50 cm Error < 50 cm for L1-C/E5a-Q (OS) < 50 cm Error < 50 cm for L1-C/E5b-Q (SoL) Assumptions: 1- 95% percentile 2- Sun Spot Number: Average error over a prediction time of 24 hours 4- Worldwide network: DOC 4 < 37 cm Error < 37 cm for L1-C/E5a-Q < 37 cm Error < 37 cm for L1-C/E5b-Q

IGS Workshop 2008 Part V. Integrity Determination Performance “Initial Reference” quality expectations“Current” experimentation results SoL SISMA for Nominal SoL GSS Network < 70 cm Broadcast SISMA < 70 cm Assumptions: 1- 68% percentile (by definition) 2- Any time within integrity table applicability period 3- Under-bounding probability better than 1E Unavailability probability better than 1E Worst satellite footprint 6- Sun Spot Number: Scintillation modeled 8- Nominal network probability ~ 0.95 <70 cm No scintillation: <70 cm <106 cm Very strong scintillation: <106 cm “Current” experimentation results are in line with the “Initial Reference” quality expectations. Nevertheless it is possible to have a sub-set of satellites with degraded monitoring under strong scintillation conditions SoL SISMA for Degraded SoL GSS Network < 130 cm Broadcast SISMA < 130 cm Assumptions as above except: 1- Degraded network probability ~ <100 cm No scintillation: <100 cm <154 cm Very strong scintillation: <154 cm (Comment as above) SoL SISA Common Undetected Failure 2.0E-8 in 150s1.9E-8 in 150s

IGS Workshop 2008 Part V. (continuation-II) Real-Time Monitoring accuracy (68%) vs satellite footprint. Degraded

IGS Workshop 2008 Part VI. Conclusions  Exhaustive performance analysis have been carried out on all the Ground Mission Segment (GMS) key performance figures  The GMS key algorithms typical performance expectations surpass generally the initial performance expectations  At this stage it is considered likely that the performance of the GMS Navigation Determination/Integrity Determination Functions will be overall compatible with the system availability needs  The GMS Navigation Determination Function & especially the GMS Integrity Determination Function algorithms will provide level of performance which had never been achieved before by any existing core GNSS System

IGS Workshop 2008 Part VII. Additional Considerations  Improvements, which are not required to satisfy the System requirements, are possible. ESA is already working hard on the preparation of the technology for “Galileo+”.  Nevertheless the performances evaluation cannot be entirely conclusive at this stage, besides the fact of the enormous sophistication of the evaluation process, due to limitations on a number of key physical and engineering models. Re-evaluation is required and of course planned at IOV

IGS Workshop 2008 THANK YOU Telephone: