FIFTH MEETING OF THE INTERNATIONAL COMMITTEEON GLOBAL NAVIGATION SATELLITE SYSTEMS (ICG)

Time metrology in navigation systems:Time metrology in navigation systems:

the experience of INRIM in the Galileo project

P t i iP t i i T llT llPatriziaPatrizia TavellaTavellaIstitutoIstituto NazionaleNazionale Ricerca Ricerca M t l iM t l iMetrologicaMetrologicaTorino, ItaliaTorino, Italia

i h i h l b ESA

1

with viewgraph courtesly by ESA

On 1st January 2006, the Istituto Elettrotecnico Nazionale "Galileo Ferraris" (IEN) and the Istituto di Metrologia "Gustavo Colonnetti" (IMGC) merged to establish the Istituto Nazionale di Ricerca Metrologica (I N RI M)the Istituto Nazionale di Ricerca Metrologica (I.N.RI.M). INRIM is the national public body with the task of carrying out and promoting scientific research in metrology.

Time metrology research activities includes:– atomic clocks– clock comparison and synchronisation techniques– mathematical modelling and algorithms

» to realise and disseminate the Italian Standard Time UTC(IT)» to realise and disseminate the Italian Standard Time UTC(IT)» to contribute to the Universal Time Coodinated UTC

We therefore need:

good clocks (on Ground and in Space)

good clock synchronisation systemgood clock synchronisation system

good reference time scalegood reference time scale

d l ith f l k l tigood algorithms for clock evaluation

3

To have the system working

All the clocks must be synchronised to the highest level of accuracylevel of accuracy

Shall they be synchronised to the internationalShall they be synchronised to the international reference time? UTC?

A navigation system is also a mean for

Topic Title

A t dNetwork synch

Network synchronization for telecomm (wireless /-line)

A study from the E

Network synch

Network synchronization for power generation / distribution

European Commission i th

Network synch

Network synchronization for digital broad-casting

in the year 2000

Network synch

Satellite monitoring / navigation (ground based) estimated

Time tagging

Maintenance of international time standards

thousands, even million

Time tagging

Frequency / time calibration services

Time Time tagging “general users”

users in Europe

tagginggg g g p

GNSS: where are the clocks and why

Clocks on board: navClocks on board: nav message, pseudorange

Time dissemination

Ground stations, pseudorangep g

Universal Time Coordinated

User clocks estimated as additional unknown

Control station, reference timeas additional unknown

All the clock have to be synchronised,S h i d h ? H d l i h lSynchonised to what? How to deal with leap second issue?

Is the clock stable enough?

How do we measure the degree of synchronization of the on board clock?y

How do we predict the clock error after synchronisation?

H d ti i t bilit ?How do we ensure time interoperability?

Galileo Programme PhasingGalileo Programme PhasingFull Operational Capability

+26 operational satellites

complete ground infrastructure

In-Orbit Validation

4 i l lli d

complete ground infrastructure

4 operational satellites andground infrastructure

Galileo System Testbed v2

GIOVE-A and -B Satellites

ground operations

Galileo System Testbed v1

Critical algorithms validation

ground operations

Critical algorithms validation

G lil S T B d V1 2002 2004GPS

GEO

Galileo System Test Bed V1: 2002-2004

Constellation GEO

Two-waytime transfer..

...

.

OSS12Experim.receiver

OSS12

bidi

Experim.receiver

UTC(k)

UTC(k)

Experim.receiverOrbitography

Processing

GSTBProcessingCentre

SensorStations

Rubidium

GPSreceiver

I

Rubidium clock

Rubidium clock

clocks

ExperimentalPrecise Timing Station

Rubidium clock

Internet ftp t

Integrity Processing

Complementary

PTB and NPL

g IEN, Turin,Italy Data Collection

FormattingArchiveMonitoring & Cntrl

transfer

ComplementarySensor StationsNetworks

Core Products DeliveryStation1 Stationn...

10

1 n...

D i 2004 2005 th IEN Ti d F l b t th E i t lDuring 2004-2005, the IEN Time and Frequency laboratory was the Experimental Galileo Time Station generating the Galileo System Time in agreement with UTC and compared with the German and English UTC(k) and the GPS time.

In collaboration with Agenzia Spaziale Europea, Alenia Spazio, Alcatel, …

11

Experimental PTS ArchitectureExperimental PTS ArchitectureLocal measurement systemLocal measurement system

Environment controlled room Dual mixer

multichannel phase comparator 10 MHz

Data Interfacewith the GSTB Processing

Local measurement systemLocal measurement system

Time signal Multiplexer Time interval

counter1pps STOP

1pps

1pps START

Industrial PCCenter, BIPM, UTC(k)

GPIBLAN

Internet

Operational Software

LAN

5MHz Frequency doubler

5 MHzGPIB

Time Stamping

UTC(IEN)GPIB

File Server

IRIG -B code reader (PC board)

IRIG B

AOG

Time scaleTime scalecalculationcalculationTime scaleTime scalecalculationcalculation

UTC(IEN)

H Maser

1pps

10MHz

1pps and frequency distribution amplifier

1pps (8 Ch) 10 MHz (8 Ch) Control & acquisition

Stamping

IRIG -B codegenerator

IRIG-Bcode (Serial line)10 MHz1pps

PPS generator

PPS distributor

1pps

Atomic clocks ensemble

Atomic clocks ensemble

Hardware realizationHardware realizationof Eof E--GSTGST

Hardware realizationHardware realizationof Eof E--GSTGST

10MHz1ppsE-GST

Frequency

10 MHz1pps

10 MHz10 MHzensembleensemble

GeodeticGPS ASHTECHtiming receiver

TWSTFT Meteosensor

GPS CV timing receiver

20 MHz

Geodetic GPS JAVADtiming receiver

doubler

12

Comparison with UTC Comparison with UTC laboratorylaboratory

Comparison with UTC Comparison with UTC laboratorylaboratorySensor StationSensor StationSensor StationSensor Station

GSTB-V1 Performances

UTC - EGST

Robustness is theRobustness is the priority

Some problems occurred during onSome problems occurred during on--line experimentation related to HW/SWline experimentation related to HW/SW

13

GSTB-V1 Performances: ComparisonComparison respectrespect toto UTCUTCUTC – UTC(k)UTC UTC(k)

For comparison the behavior of some time scales UTC(k) versus UTC is also reported together with EGSTFor comparison the behavior of some time scales UTC(k) versus UTC is also reported together with EGST

it can be seen that remaining within +it can be seen that remaining within +--50 ns is a demanding goal, especially considering that the UTC(k) 50 ns is a demanding goal, especially considering that the UTC(k)

14

gg g g , p y g ( )g g , p y g ( )timescales are generated in scientific, manned, laboratoriestimescales are generated in scientific, manned, laboratories

First First twotwo Galileo Galileo satellitessatellites in in spacespace

GSTB V2GSTB V2GSTB V2 GSTB V2 20052005--20102010

GIOVE B launched April

GIOVE A launched on Dec 28, 2005 27, 2008

THE GESS NETWORKTHE GESS NETWORK– 13 stations– World-wide distribution– Dual GPS+Galileo receiversDual GPS Galileo receivers– GPS needed to synchronize all

clocks with the master clock at any time (“common view”)any time ( common view )

– Two master clocks: • GIEN (prime)

GIEN INRiM, Turin ItalyGKIR Kiruna SwedenGKOU Kourou French Guyana

• GUSN (backup)– GIOVE (and GPS) always in

view of at least 2 stations GKOU Kourou French Guyana

GLPG La Plata ArgentinaGMAL Malindi Kenya

G i

(DOC-2)

GMIZ Mizusawa JapanGNNO New Norcia AustraliaGNOR ESA, Noordwijk The Netherlands

GOUS Dunedin New ZealandGTHT Tahiti French

PolynesiaGUSN USNO, Washington USAGUSN USNO, Washington USA

GVES Vesleskarvet AntarcticaGWUH Wuhan China

THE SENSOR STATION (GESS)THE SENSOR STATION (GESS)--

• GESS main elements:– Wide-band

antenna– GPS+Galileo

receiver (GETR)(GETR)

– UPS + computerRubidium clock

IEN

– Rubidium clock or connectivity to an external clock1PPS signal

10 MHz frequency signal clock1PPS signalsignal

Laboratory

Routine activities at INRIM

INRIM Time and Frequency

Free running

active H maser UTC(IEN)UTC(IT)IEN MeasurementSystem

INRIM MeasSystemSystem

PPSGeneratorPPS

Generator

TemperatureTemperature --controlled chambercontrolled chamber

Time offset [UTC(IT) – H maser ] sampling rate: 1 hoursampling rate: 1 hour

Galileo GSTB V2 Experimental

•• First First European European navigation satellitenavigation satellitess in MEO orbit.in MEO orbit.Satellites

•• Europe Europe meets meets requirements for Galileo frequency requirements for Galileo frequency filings.filings.

•• The HThe H--maser maser clock is the most clock is the most stable clock ever stable clock ever flown in space.flown in space.

•• On On BoardBoard Clock and Clock and SensorSensor Station Station fullyfullycharacterisedcharacterised

On ground a network of Sensor Station and an Orbit Determination & Time Synchronization processing similar to GSTB V1 with the addition of GIOVEsimilar to GSTB V1 with the addition of GIOVE tracking capabilities and Satellite Control Centers

Passive H Maser (GIOVE-B)

GIOVE clocksGIOVE clocks

Rubidium (GIOVE A)Rubidium (GIOVE A)

D i t bilitDynamic stability

ESA archive

http://www.giove.esa.inthttp://www.giove.esa.int

Galileo Time Keeping System SetupGalileo Time Keeping System Setup

UTC(k)

TSPTime Service Provider

UTC(k)

TSP

UTC(k)

UTCPTF1PTF2Precise Time FacilitPrecise Time Facility

ESA archive

CurrentlyCurrently in thein the

DevelopmentDevelopment ofof the Ground the Ground SegmentSegment: : pp ff gg

2 Galileo 2 Galileo ControlControl CentersCenters

2 Precise 2 Precise TimeTime FacilitiesFacilities ec se ec se ee ac t esac t es1. Kayser Threde consortium

2. Consorzio Torino Time• INRIM

T i Wi l

Time scale algorithms

• Torino Wireless• Finpiemonte• Politecnico di Torino• SEPASEPA• SIA• Thales Alenia Space• ISMB

FIDELITY (2005-2009)

Delivering the Prototype of the Galileo Time Service Provider (GTSP)

To maintain the Galileo System Time

in close agreement with the International UTCin close agreement with the International UTC

Galileo Galileo TimeTime Service ProviderService Provider

24

Now preparing for the In Orbit Validation:

the Time and Geodetic Validation Facility TGVF 2010-2012

25

A visit to INRIM tonight

good clocks (on Ground and in Space)

d l k h i iGNSS timing

system stimulated and new good clock synchronisation systemsystem stimulated

research in time metrology

timing applications

good reference time scale

gy

and involved UTCgood reference time scaleand involved UTC community in GNSS with

mutual benefits

good algorithms for clock evaluation

27