1. The Galileo Precise Timing Facility
software architecture
Andrea Ferrato
(AleniaSIA S.p.A.,
Consorzio Torino Time)
ITN - Oct 15, 2009 - Turin | © 2009 AleniaSIA S.p.A. - tutti i diritti riservati 1

2. Outline
• AleniaSIA overview
• What is PTF
• PTF software tasks
• PTF software architecture
– Chosen software platform
– Implementation details
– Applied standards
• Closing remarks
ITN - Oct 15, 2009 - Turin | © 2009 AleniaSIA S.p.A. - tutti i diritti riservati 2

3. AleniaSIA overview
Shareholders:
60% 30%
10%
Aeronautical Avionic SW & M346 Master
systems
16% EuroFighter
Main programs
Flight
Market areas
Space management
Logistic UAVs
35%
support,
analysis IXV
and tools
Defense 16% ATR
C27-J
Test tools
Training tools AW139
Transport 16%
17%
Galileo
ITN - Oct 15, 2009 - Turin | © 2009 AleniaSIA S.p.A. - tutti i diritti riservati 3

4. What is PTF
• Part of Galileo Ground Mission Segment
• Generates Galileo System Time for
synchronization of the satellite
constellation and depending services
Sync()
Sync()
Sync()
Galileo
Ground
Mission
Segment
GACF PTF Rest of GMS
ITN - Oct 15, 2009 - Turin | © 2009 AleniaSIA S.p.A. - tutti i diritti riservati 4

5. What is PTF (2)
H-Maser pStepper
clocks Switching Distri-
Matrix butors GST
Caesium
Time acq.
clocks
Time
PTF Transfer
Time acq. Internal
LAN
PTF
PTF Control & Router
Control Computer Rest
Algorithms SW of GMS
PTF Data LAN
ITN - Oct 15, 2009 - Turin | © 2009 AleniaSIA S.p.A. - tutti i diritti riservati 5

6. PTF software tasks
• GST stabilization, via:
– Internally-run algorithms (prototyped by TAS-I, INRiM,
Politecnico di Torino)
– Comparison with Temps Atomique International,
NavStar timescale, PTF-2 timescale
• Monitoring & Control of internal hardware
• Interaction with the rest of GMS
– Status information to GACF
– Data exchange with other elements
⇒ many tasks & criticalities, one system
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7. PTF software architecture: chosen
platform
• LynuxWorks LynxOS-178:
– OS designed for safety-critical, multi-
process applications
– Based on open standards (POSIX, ARINC-
653)
– Federated architecture: each process is put
in a partition with a strictly time- and space-
constrained execution window
⇒ partition ≈ separate machine
ITN - Oct 15, 2009 - Turin | © 2009 AleniaSIA S.p.A. - tutti i diritti riservati 7

8. PTF software architecture:
implementation details
ARINC-653 API
Interpartition
comm. (ARINC
multicast)
p4 p3 p2 p1 p0
PTF
Steering System PTF External SNMP
Control & Manager Manager Handler I/F M&C
(DAL-C) (DAL-C) (DAL-C) (DAL-E) (DAL-E)
Algorithms SW
Lynx Certifiable Stack API (proxy-based approach)
LynxOS-178 kernel
Scalable /
Rest of File transfer Commanding
(FTP/TCP)
distributable and monitoring
GMS
(SNMP/UDP)
GACF
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9. PTF software architecture:
applied standards
• Galileo Software Standard (tailored on
RTCA DO-178B)
– Waterfall development model
– Highest criticality level: DAL-C
• Avionics-like Verification and
Validation process
– Low level (i.e. unit testing, coverage analysis)
– High level (i.e. integration, validation against
requirements)
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10. PTF software architecture:
applied standards (2)
Activity Adopted tools and methods
Memory profiling http://valgrind.org/,
LynuxWorks SpyKer
Code static analysis http://www.splint.org/
Functional unit- and IPL Cantata++
integration- testing
100% statement coverage IPL Cantata++
Validation against CI and [custom procedures]
software system
requirements
ITN - Oct 15, 2009 - Turin | © 2009 AleniaSIA S.p.A. - tutti i diritti riservati 10

11. Closing remarks
• Significant know-how acquisition
– Formal: management of high-level standards
(GSWS) and processes (GSWS Waterfall
DAL-C)
– Technical: on the design and implementation
of ARINC-653-based architectures (i.e. IMA
avionics)
– Contextual: probable involvement as
partners in the next Galileo PTF phase (“Full
Orbit Configuration”)
Thank you!
ITN - Oct 15, 2009 - Turin | © 2009 AleniaSIA S.p.A. - tutti i diritti riservati 11