Title: VEGA Company Presentation
1Galileo System Simulation Facility
(GSSF) Validation Approach Frank Zimmermann,
Thomas Haak (VEGA) Chris Hill (University of
Nottingham)Henno Boomkamp, Rene Zandbergen
(ESA/ESOC)
2Overview
- Introduction
- GSSF Simulation Capabilities
- Modelling Assumptions
- System Level Validation of GSSF
- Independent Validation at ESOC
- Summary
Technical Excellence . Pragmatic Solutions .
Proven Delivery
3Introduction
- Galileo
- Independent, global, European satellitenavigation
system - For civilian applications interoperable with
GPS - GSSF
- Simulation environment that reproducesthe
functional and performance behaviour of
theGalileo system - Offers the necessary flexibility and functional
scopeto support Galileo system simulation needs
during the entire program life cycle. - Developed on behalf of ESA/ESTEC by an
international consortium VEGA (prime), Scisys
Space and Defence Ltd. (UK), Dataspazio S.p.A.
(Italy), CAE Inc. (Canada), SENER S.A. (Spain),
University of Nottingham (UK), IfEN GmbH
(Germany) and GMV S.A. (Spain) - Further upgrades currently being carried out by
VEGA, University of Nottingham, DEIMOS (Spain)
and TAITUS (Italy)
4GSSF Simulation Capabilities
- GSSF provides a single simulator that uses
alternative models depending upon the type of
analysis the end-user wishes to perform (more
flexibility than traditional simulators) - Service Volume Performance Analyses (navigation
and integrity performance over longer time
periods and over large geographical areas). - Raw Data Generation (Galileo and GPS raw data for
experimental purposes RINEX observation, IGS
SP3) - Simulation of the nominal system and its various
degraded modes (deterministic or probabilistic
manner)
5GSSF Model Components
- Space Segmentsatellite models
- Environmentmain perturbationson satellite
signal - User Segmentuser receivers andinternal
algorithms - Ground SegmentGS modelsfollowing
Galileobaseline
6Modelling Assumptions
- SVS
- Model fidelity satisfies required accuracy while
maintaining sufficient runtime performance. - Keplerian orbit prediction
- Environmental delays are derived from UERE
Budgets. - Optimised for simulation over large geographical
areas and long time periods - RDG
- High fidelity environmental modeling and orbit
prediction for accurate data provision - Ionosphere (NeQuick), Troposphere (Hopfield),
Gravity (JGM3 and third-body perturbations),
Solar Radiation Pressure, Multipath, Noise,
7GSSF User Interface
- Integrated graphicalelements are used to
- control the simulation
- provide access tosimulation parameters
- process the results
- Developed onWindows (.NET)
- Models platformindependent (C)
- No run-time dependenceon commercial products
8SVS Simulation Example (1)
- Nominal SISMAfor Galileo on aGSS network
- Representslevel of accuracyin
monitoringsatellite positions
9SVS Simulation Example (2)
- Nominal SISMAfor Galileo on aGSS network
- Subject to twostation failuresover North
America - SISMA degradesaccordingly
10GSSF System Level Validation
- SVS Validation
- Against simulated data from trusted sources
- RDG Validation against real data
- RINEX files from Kourou were extracted from the
GSTB-V1 test data set together with IGS ephemeris
and clock files. - Code, carrier and Doppler measurements as
simulated by GSSF RDG were compared with those
obtained from the real Kourou data. - The RDG Validation process adopted an incremental
approach, where stepwise, external data files
were replaced by GSSF models.
11RDG Validation Stepwise Approach
- Step 1 - Baseline scenario Replace the GSSF
models with data sources which represent the
prevailing conditions in the measured data from
the TDS - ? minimise the differences between the measured
and simulated data - Step 2 - Incremental tests Incrementally replace
these real data sources with the corresponding
GSSF models. At each step, the increasing
differences between the real data and the
simulated data are assessed. - ? characterisation of the level of fidelity that
can be expected from GSSF - Step 3 - Load test Repeat test for full network
of Galileo sensor stations - ? check performance 48 hours, 1 second
time-step, 28 GPS spacecrafts, 23 Ground
Stations,1 Channel L1C/A, Observables C1, L1,
D1, S1 (10 h 30 min)
12Independent Validation by ESOC (1)
- ESA/ESOC have carried out an independent
validation of GSSF with the following prime
objectives - Characterise the GSSF orbits in terms of model
fidelity and validity of implementation - Process Raw Data (RINEX and SP3) produced by GSSF
as it was real measurement data using the
standard IGS processing software at ESOC
13Independent Validation by ESOC (2)
- Rationale and Test Case Definition
- (1) System-level test for propagated orbits and
Earth rotation model - (2) System-level test for simulated GPS tracking
data (code phase)
GSSF propagated orbits forming Earth-fixed XYZ
observations
Different combinations of perturbation models
allow validation of individual GSSF force models
ESOC POD software fits internal orbit models to
external XYZ data
Solution characteristics as similar as feasible
to GPS processing at ESOC for routine IGS
products
GSSF simulated GPS tracking data for 25 ground
stations
ESOC POD performs routine IGS-like POD process on
GPS data
14Independent Validation by ESOC (3)
- ESOC orbit models vs. GSSF models 64 mm RMS fit
over 24 hrs - Tracking data fit post-solution tracking
residuals are 20 cm RMS for code data and 3 cm
RMS for phase data
15Independent Validation by ESOC (4)
- Conclusion
- ESOC was able to fit the GSSF orbits with high
accuracy. - The GSSF Raw Data is a valid representation of
realmeasurement data. - Independent validation will remain integral part
of project during ongoing upgrade activities.
16Summary
- GSSF provides a single simulator that uses
alternative models depending upon the type of
analysis the end-user wishes to perform. - GSSF provides Raw Data Generation for GPS and
Galileo - Functional TDS is already available and was
validated with GPS data. - Calibration with real GSTB V2 data will allow
production of Galileo TDS with proven
representative performance - Software tools used within the Galileo program
can be rigorously tested also for off-nominal
conditions. - SVS Capability meant primarily for definition can
be applied to teaching and outreach.
17www.gssf.info www.vega-group.com frank.zimmermann_at_
vega.de
Consulting and Technology Technical Excellence .
Pragmatic Solutions . Proven Delivery
18www.gssf.info
19GSSF RDG Upgrades
- The following RDG upgrade activities are
currently ongoing - Ionosphere Modelling (higher order terms and
residual errors) - Troposphere Modelling (SINEX Import)
- Antenna Phase Centre Offset
- Code Tracking Error Variance
- HW Biases and Receiver Cycle Slips
- Earth Solid Tides
- Solar Radiation Pressure Model (Galileo-specific)
- RDG Model Calibration against real GSTB V2
satellite data - Production of Galileo Test Data Set with
representative performance
20RDG Validation Example Result
- Penultimate step of the incremental tests - all
the external data sources, apart from the SP3
ephemeris, were replaced with their equivalent
GSSF models - ? Majority of the measurements agree to better
than 2 m. - ? GSSF is capable of reproducing raw data that is
very similar to real data.
21GSSF External Interfaces
- GSSF provides internal andexternal Interfaces
that allow - Exchange of algorithmsand external
dataingestion - ConstellationInitialisation
- EnvironmentalModels
- Ingest data produced byGSSF into other tools
forfurther analysis
22GSSF Data File Format
- Text-based file format
- Human readable
- Used for input and output
- Used internally in GSSF but accessible
- Used for all recorded simulation data
- Input/output for analyses and post processing
- Input for visualisation
- Simplifies data exchange with external tools
23SVS Modelling Assumptions
- Model fidelity satisfies required accuracy while
maintaining sufficient runtime performance. - Keplerian orbit prediction
- Environmental delays are derived from UERE
Budgets. - Optimised for simulation over large geographical
areas and long time periods
24RDG Modelling Assumptions
- 3 major blocks represent real Galileo Segments.
- (User Segment is modelled by means of user
receiver locations and internal algorithms but
not relevant for RDG.) - High fidelity environmental modelling for
accurate data provision