igs workshop 2008 the galileo ground mission segment performances francisco amarillo-fernandez,...
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IGS Workshop 2008
The Galileo Ground Mission Segment Performances
Francisco Amarillo-Fernandez, Massimo Crisci, Alexandre BallereauFrancisco Amarillo-Fernandez, Massimo Crisci, Alexandre BallereauJohn Dow, Martin Hollreiser, Joerg Hahn, Jean-Luc Gerner, John Dow, Martin Hollreiser, Joerg Hahn, Jean-Luc Gerner,
European Space AgencyEuropean Space Agency
IGS Workshop 2008
CONTEXTCONTEXT
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). Introduction (I). Galileo Ground Mission Galileo Ground Mission Segment. Functional OverviewSegment. 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
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Introduction (II). Introduction (II). DefinitionsDefinitions
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”
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Part I. Tracking Stations Part I. Tracking Stations PerformancePerformance
“Initial Reference” quality expectations“Current” quality
expectations
Code tracking error (excluding multipath)
E5a-Q : Between 6 and 23 cm Between 6 and 23 cm E5b-Q : Between 6 and 23 cm Between 6 and 23 cm E1-C : Between 15 and 41 cmBetween 15 and 41 cm
Assumptions:1- Minimum satellite EIRP2- No ionospheric scintillation 3- Maximum in band interference4- Error dependency on satellite elevation (from 5º to 90º)5- Tracking on pilot6- Root mean square value
E5a-Q : Between 9 and 31 cm Between 9 and 31 cm E5b-Q : Between 9 and 31 cm Between 9 and 31 cm E1-C : Between 13 and 41 cm Between 13 and 41 cm
Carrier tracking error (excluding multipath)
< 2.5 mm< 2.5 mm
Assumptions as indicated for the code tracking error (excluding multipath)
Between 2 and 4 mm Between 2 and 4 mm
Code tracking error due to multipath
Between 10 and 100 cmBetween 10 and 100 cm
Assumptions:1- Worst multipath delay2- Average multipath phase3- Range obeys to error dependency versus the D/U ratio. 4- Applicable to the following signals E5a-Q, E5b-Q, E1-C5- Tracking on pilot6- Root mean square value
Between 15 and 140 cmBetween 15 and 140 cm
Carrier tracking error due to multipath
Between 0.7 and 10 mmBetween 0.7 and 10 mm
Assumptions as indicated for the code tracking error (due to multipath)
Between 0.8 and 11 mmBetween 0.8 and 11 mm
IGS Workshop 2008
Part II. Orbit & Clock Determination Part II. Orbit & Clock Determination PerformancePerformance
“Initial Reference” quality expectations“Current” quality
expectations
Predicted Clock and Orbit
UERE
< 130 cm < 130 cm
Assumptions:1- 95% percentile2- End of navigation message applicability period (100 minutes)3- Worst satellite4- Worst user location (infinity velocity approach)5- Masking angle 0º6- Worldwide network 40 stations
Not in eclipse < 70 cm < 70 cm In eclipse < 78 cm< 78 cm
Predicted Clock and Orbit
First derivative of the
UERE
< 10 mm/s< 10 mm/s
Assumptions: as above
Not in eclipse < 4.1 mm/s< 4.1 mm/sIn eclipse < 4.3 mm/s< 4.3 mm/s
Restituted Orbit Error
< 10 cm < 10 cm
Assumptions: 1- 67% percentile2- Worst satellite3- Average over the arc duration4- Worldwide network 40 stations
< 12 cm< 12 cm
Restituted Clock Error
< 0.3 ns< 0.3 ns
Assumptions: 1- 67% percentile2- Worst satellite3- Average over the arc duration4- Worldwide network 40 stations
< 0.5 ns< 0.5 ns
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Part II (continuation-I) Part II (continuation-I) Ranging accuracy (95%) versus satellite and experimentation batch
DAY
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Part III. GTTO Offset Determination PerformancePart III. GTTO Offset Determination Performance
“Initial Reference” quality expectations “Current” quality expectations
SoL SISA Upper bound
< 85 cm< 85 cm
Assumptions:
1- 68% percentile (by definition)2- Any time within navigation message applicability period (100 min)2- Under-bounding probability: 1E-043- Upper-bound unavailability probability of: 1E-054- Worst satellite5- Galileo over-bounding6- Signal-In-Space in fault free7- After convergence8- Worldwide network: 40 stations
Not in eclipse < 46 cm< 46 cmIn eclipse < 54 * cm< 54 * cm
* Note: currently under detailed assessment for eclipse condition
Part II (continuation-III) Part II (continuation-III)
“Initial Reference” quality expectations “Current” quality expectations
Galileo to GPS Time
Offset
< 5 ns< 5 ns
Assumptions:
1- 95% percentile2- Average error over 24 hours
< 10.4 ns
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Part IV. Group Delay Determination Part IV. Group Delay Determination PerformancePerformance“Initial Reference” quality expectations “Current” experimentation
results
BroadcastGroup Delay
Error < 50 cm< 50 cm for L1-C/E5a-Q (OS)
Error < 50 cm< 50 cm for L1-C/E5b-Q (SoL)
Assumptions:
1- 95% percentile2- Sun Spot Number: 1503- Average error over a prediction time of 24 hours4- Worldwide network: DOC 4
Error < 37 cm< 37 cm for L1-C/E5a-Q
Error < 37 cm< 37 cm for L1-C/E5b-Q
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Part V. Integrity Determination PerformancePart V. Integrity Determination Performance“Initial Reference” quality expectations “Current” experimentation
results
SoL SISMA for Nominal
SoL GSS Network
Broadcast SISMA < 70 cm< 70 cm
Assumptions:
1- 68% percentile (by definition)2- Any time within integrity table applicability period 3- Under-bounding probability better than 1E-094- Unavailability probability better than 1E-055- Worst satellite footprint6- Sun Spot Number: 2507- Scintillation modeled8- Nominal network probability ~ 0.95
No scintillation: <70 cm <70 cm Very strong scintillation: <106 cm<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
Broadcast SISMA < 130 cm< 130 cm
Assumptions as above except:1- Degraded network probability ~ 0.9995
No scintillation: <100 cm<100 cm Very strong scintillation: <154 cm<154 cm
(Comment as above)(Comment as above)
SoL SISA Common
Undetected Failure
2.0E-8 in 150s 1.9E-8 in 150s
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Part V. (continuation-II) Part V. (continuation-II) Real-Time Monitoring accuracy (68%) vs satellite footprint. Degraded
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Part VI. ConclusionsPart 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
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Part VII. Additional ConsiderationsPart 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 YOUTHANK YOU
Email: Email: [email protected]: +31 71 565 3446Telephone: +31 71 565 3446