Galileo Assembly, Integration and Verification Platform
(AIVP)
VEGA plays a key role in the development of Galileo, the new
European satellite navigation system, which is an alternative to
the American Global Positioning System (GPS).
Challenge
The Galileo Mission Segment (GMS) is the heart of the Galileo
satellite navigation system. It comprises a global network of
sensor stations to monitor the signals from the satellites, a chain
of Earth stations to uplink navigation data to the satellites,
parallel communications networks, and a complex sequence of
safety-critical processing elements. Collectively, these provide a
navigation service that is sufficiently accurate, reliable and
trustworthy that aircraft may use it for their final approach.
The Assembly, Integration and Verification (AIV) of these
elements into a complete working Mission Segment drives the
critical path for the whole Galileo programme. The European Space
Agency (ESA) and Galileo Industries ran a competition to find the
best approach to reduce the risk on this critical part of the
programme. VEGA's solution was chosen as the clear winner.
VEGA's solution
In order to provide the greatest flexibility to the GMS
development schedule, VEGA's solution provides an AIV Platform
which comprises a system of Element Emulators, each of which
represents one of the blocks in the complete GMS processing chain.
By adding the Raw Data Generator (RDG) from the Galileo System
Simulation Facility (GSSF), developed by VEGA under a separate
project, VEGA was uniquely able to offer an AIV Platform design
that could produce a complete 'closed-loop' simulation of the GMS,
much more rapidly and cost-effectively than any competitor.
Each Element Emulator provides a complete implementation of the
input and output interfaces of the element being simulated, along
with a 'behaviour model' that represents the simplified functions
of the real element, with enough fidelity that it can play its role
correctly in the processing chain.
As each real GMS element becomes available from its manufacturer,
the corresponding Emulator can be taken out of the loop and the
real element connected to the network. One by one, the Element
Emulators are replaced by the real processing components until
eventually the whole GMS has been integrated and validated. In this
way, the complete GMS can be integrated in the order in which
elements become available; the AIV process becomes robust against
delays in the development of individual components and the
interfaces between elements can be fully tested at the earliest
opportunity.
Implementation
The GMS AIVP comprises 14 discrete Element Emulators, each
running on a laptop or PC under the Linux operating system, along
with a Master Control and Analysis Toolset, and a 16 Tbyte data
storage system.
The Control and Analysis Toolset provides the ability to operate
and monitor the Element Emulators remotely. As well as providing
the operator's user interface, it is also responsible for tasks
such as data logging, configuration and control, and functions to
allow the user to modify specific parameters in the test
configuration, either in real-time or through scripts. It is
developed using ESA’s SIMSAT modelling infrastructure, whose
development and evolution has been led by VEGA over many
years.
The Analysis functions allow the operator to filter the huge
volumes of data produced by a typical scenario run on the platform,
and to produce meaningful representation of the behaviour of the
elements under test.
The Element Emulators are also based on SIMSAT, with the addition
of VEGA's own Interface and Behaviour Modelling Infrastructure,
which provides the ability for changes to be made to Element
Emulator behaviour and interface definitions relatively easily. In
particular, interface definitions are not fixed and sealed within
the Emulators, but are externally generated and readily updated.
This is a key aspect of the VEGA design, because the AIVP
development runs in parallel with the evolution of the interface
definitions for the GMS
components. The ability for interfaces to be "loaded, not coded"
provides the flexibility that the Galileo programme needs.
Our Involvement
VEGA is the Prime Contractor for the GMS AIVP development,
managing a contract worth €5.75m, with sub-contractors including
Nottingham Scientific Ltd and a consortium representing industry
from the Netherlands.
Value delivered
The GMS AIVP provides:
- A platform that greatly reduces schedule and development risk
for the Galileo Mission Segment programme
- A flexible approach to the validation of element interfaces,
which allows the AIV platform be developed in parallel with the
evolution of these interfaces
- An opportunity for the GMS team to get real experience of
operating the GMS, long before the complete Galileo system is
deployed and ready for service