Upload
others
View
2
Download
0
Embed Size (px)
Citation preview
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