W002 - World Visions Orario 14.30 – 18.00 Sala 4 SPECIAL GALILEO/EGNOS & GNSS News and latest activities from the worldwide satellite navigation systems

1. October 15th, 2009
GALILEO / EGNOS & GNSS
Galileo & GNSS: Research, developments and applications
Time and Frequency Research at INRIM
for Applications to Satellite Systems
AUTHORS:
Elio Bava,
Istituto Nazionale di Ricerca Metrologica (INRIM) – Politecnico di Torino
and Time & Frequency INRIM Group
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2. TIME METROLOGY AND
NAVIGATION SYSTEMS
Time Metrology is fundamental for NAVIGATION and POSITIONING
GNSS use clocks (frequency
standards + counters) and
carry out measurements of
propagation time of EM
signals from a source to a
receiver for a distance
estimate.
E.g.: in spherical navigation
position is estimated by
measuring distances from 3
points having a known
position.
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3. THE METRE
SI unit of time (13th CGPM 1967):
the second is the duration of 9192631770 periods of the radiation
corresponding to the transition between the two hyperfine levels of the ground
state of the caesium 133 atom.
SI unit of length (17th CGPM 1983) took into account also the needs
linked to the navigation systems:
the metre is the length of the path travelled by light
in vacuum during the time interval of 1 / 299 792 458 of a second
∆l = c ∆t
By definition c = 299 792 458 m/s
Biases due to electromagnetic properties of the medium and
to gravitation are to be known and taken into account
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4. Length measurement depends on time measurement
therefore we need clocks (on Ground and in Space)
stable, accurate, space qualified, reliable,
small, light, low consuming
Clocks in Space, Control and User segments,
altough with different stability characteristics,
must be syncronized to the highest level of
accuracy.
Link to the Universal Time Coordinated (BIPM, Paris)
mandatory
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5. Main research activities
in time metrology at INRIM
clock mathematical
atomic comparison and modelling
clocks synchronization and algorithms
techniques
to realize and to contribute
disseminate to the
the Italian Standard Time International Atomic
UTC(IT) Time (TAI)
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6. Atomic clocks at INRIM
Primary Cs standard (fountain, room temperature, working)
Primary Cs standard (fountain, liquid nitrogen, preliminar
operation)
Cs beam, Rb cell and H maser standards to maintain UTC(IT)
Rb cell frequency standards for space applications
- Maser (Coherent Population Trapping), 2000 – 2003, ESA
- Pulsed Optically Pumped (μwave detection), 2003-2006, ASI
- Pulsed Optically Pumped (optical detection), 2008-2009, ESA
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7. PRIMARY STANDARD: CRYOGENIC CS FOUNTAIN
Ramsey signal
1 2
0.9 0.9
Transition Probability
Transition Probability
0.6 0.6
0.3 0.3
0.0
-90 0 90 -4 -3 -2 -1 0 1 2 3 4
Center frequency /Hz Center frequency /Hz
Accuracy
No evidence of characterization
unexpected biases at 10-16 level.
at 1x10-15 level.
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8. Rb STANDARD FOR SATELLITE APPLICATIONS
Allan deviation measurement
POP maser (ASI contract) : σy(τ) ≈ 1.2 × 10−12 τ - 1 / 2, 1 ≤ τ ≤ 50000 s.
POP with optical detection in progress (ESA contract) :
fundamental limit ⇒ σy(τ) ≈1×10−13 τ - 1 / 2
CAUTION:
laser and microwave noises may overcome this limit (3-6×10−13 τ - 1 / 2)
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9. Progetto Ente Anni Scopo CapoCommessa
Autonomous Ephemerids Determination ESA 1998 Possibi le architettura GNSS 2 DLR D
Comparative System Study ESA 1999 Confronto diversi sistemi GNSS ALENIA Spazio
GEMINUS CE 2000 Definizione dei servizi RACAL UK
GALA CE 2000 Valutazione Sistema Galileo ALCATEL F
GALILEOSAT ESA 2000 Architettura del sistema ALENIA Spazio
New methods and systems for time and ESA 2000 Nuovo sistema di sincronizzazione da e per Gavazzi Space Milano
frequency distribution via satellite satelliti
GalileoSat Time Interface Working Group ESA 2000-2001
From 1998 till the end 2009
Gruppo di lavoro Istituti Me trologia per Galileo ESA
GALILEO Phase B2 ESA 2002
18 European collaborations Alenia
Definizione architettura del sistema Galileo Industries
GALILEO Phase B2 Consolidation 2002 ESA 2002 Definizione architettura del sistema Galileo Industries, Alenia
Galileo System Test Bed V1 ESA 2002-2005 Prove sperimentali a Terra degli algoritmi di Galileo Industries, Alenia
Galileo
Galileo Phase C0 ESA 2003-04 Progettazione sistema Galileo Industries, Alenia
Galileo Time Service Provider (TSP) GJU 2004-2005 Definizione ruolo e requisiti Time Service FDC F NPL UK
Provider
Galileo System Test Bed V2 ESA 2005-2007 Prove tecniche con 2 satelliti ed orologi Galileo Galileo Industries
Galileo Time Service Provider (TSP) GJU 2005-2008 Progettare e realizzare prototipo TSP Helios UK
Precise Timing Facility (PTF) ESA 2005-2008 Sviluppo, installazione e prova PTF Consorzio Torino Time
PROGENY GJU 2005-2007 Esperti a sostegno della GJU FDC F
Galileo Phase CDE1 System Verification ESA 2005-2007 Sviluppo del sistema fino alla IOV Offerto da GAIN, Alenia
Galileo Phase CDE Ground Segment ESA 2005-2007 Sviluppo del Segmento di Terra Offerto da Alcatel F
Giove Mission ESA 2008-2010 Caratterizzazione orologio a bordo di Giove Thales - I - Fr
Advent ESA 2008-2009 Algoritmi per rilevazione anomalia orologio CMV Madrid
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10. Galileo System Test Bed V1: 2002-2004
GPS
Constellation GEO
Two-way
.. time transfer
.. .
.
UTC(k)
Experim. Sensor
GPS OSS12
OSS12 Orbitography
GSTB Experim.
receiver Stations Processing
Experim.
receiver receiver
receiver Processing
Rubidium
Centre UTC(k)
Internet ftp transfer
Rubidium
Rubidium clocks
clock
clock Integrity
clock Processing PTB and NPL
Experimental
Complementary Data Collection
Precise Timing Station
Sensor Stations
IEN, Turin,Italy
Formatting
Networks Archive
... Monitoring & Cntrl Core Products Delivery
Station1 Stationn
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11. Galileo Precise Time Facility
Development of the ground segment
2 Galileo Control Centers
2 Precise Time Facilities (PTF)
Kayser Threde consortium
Torino Time Consortium (CTT)
with INRIM, Torino Wireless, Finpiemonte,
Politecnico di Torino,
SEPA, SIA, Alenia Spazio,
Istituto Superiore Mario Boella (ISMB)
INRIM is developing the time scale algorithm supporting calibrations
Fidelity (2005-2009)
UTC(k) labs
• provide clock measurements
• realise a composite time scale
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• ensure synchronisation to UTC
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12. Current timing activity of INRIM
H maser
Rb clock
GIOVE A GIOVE B
INRIM is responsible of the characterisation of the
on board clocks and provides the on ground
reference clock (Active H Maser) connected to a GPS
Galileo Sensor Station.
In collaboration with ESA,
Thales Alenia Space,
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GMV, Indra…
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13. Timekeeping in 21st century : what to do
• Clocks and (optical) frequency standards
• Remote clock comparison systems:
GNSS receivers, calibration issues and noise reduction
multisystem solution (GPS + GALILEO + GLONASS)
• Algorithms: clock monitoring for integrity
• Time Scale realisation: robustness is the issue
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14. THANKS!
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