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

Time metrology in navigation systems:

the experience of INRIM in the Galileo project

PtiiPatrizia TllTavella Istituto Nazionale Ricerca MtMetro logi ca Torino, Italia wit h v iewgrap h courtes ly by ESA

1 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). 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 contribute to the Universal Time Coodinated UTC We therefore need: good clocks (on Ground and in Space) good clock synchronisation system good reference time scale good algorith ms f or cl ock eval uati on

3 To have the system working

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

Shall they be synchronised to the international reference time? UTC? A navigation system is also a mean for Topic Title AtdA study Network Network synchronization for synch telecomm (wireless /-line) from the European Network Network synchronization for synch power generation / distribution Commission ithin the year Network Network synchronization for synch digital broad-casting 2000

Network Satellite monitoring / navigation synch (ground based) estimated Time Maintenance of international time thousands, tagging standards even million Time Frequency / time calibration tagging services users in

Time Time taggin g “ general users” Europe tagging GNSS: where are the clocks and why

Clocks on board: nav message, pseudorange Time dissemination

Ground stations, ppgseudorange Universal Time Coordinated

User clocks estimated Control station, as additional unknown reference time All the clock have to be synchronised, Shidh?HdlihlSynchonised 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?

How do we predict the clock error after synchronisation?

How do we ensure time in teropera bility ? Galileo Programme Phasing

Full Operational Capability +26 operational satellites complete ground infrastructure

In-Orbit Validation 4 operat iona l sate llites an d ground infrastructure

Galileo System Testbed v2 GIOVE-A and -B Satellites ground operations

Galileo System Testbed v1 Critical algorithms validation GlilGalileo S ystem T est BdBed V1: 2002 -2004

GPS Constellation GEO Two-way .. time transfer .. . .

GPS Sensor GSTB Experim. UTC(k) Experim. OSS12 Orbitography receiverExperim. StationsOSS12 receiver receiverreceiver Processing Processing

I Centre UTC(k) Rubidium ftp nternet Ru Rubidiumbidium clocks clockclock Integrity clock Processing PTB and NPL Experimental t Complementary ransfer Precise Timing Station Data Collection IEN, Turin,Italy Sensor Stations Formatting Networks Archive Monitoring & Cntrl Core Products Delivery Station1...Stationn

10 Dur ing 2004 -2005, the IEN Ti me and F requency l ab orat ory was th e E xperi ment al 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 Architecture

Local measurement system

Data Interface Environment controlled room 10 MHz Dual mixer with the multichannel phase comparator GSTB Processing Center, BIPM, LAN Industrial PC UTC(k) 1pps Time signal START Time interval Operational 1pps Multiplexer Software counter Internet 1pps STOP GPIB LAN

GPIB UTC(IEN) Time scale Frequency IRIG -B 5MHz doubler code reader calculation 5 MHz (PC board) AOG GPIB File Server Time Stamping PPS 1pps IRIG-B 10 MHz code (Serial line) distributor 1pps 1pps 1pps and frequency distribution Hardware realization IRIG -B code UTC(IEN) amplifier PPS generator of EE--GSTGST 1pps (8 Ch) 10 MHz (8 Ch) Control & Atomic clocks H Maser generator acquisition ensemble 10MHz 10 MHz 10 MHz E-GST 1pps

1pps 10 MHz

Frequency GPS CV timing Geodetic GPS JAVAD doubler TWSTFT Meteo receiver timing receiver sensor 20 MHz

GeodeticGPS ASHTECH timing receiver

Comparison with UTC Sensor Station laboratory 12 GSTB-V1 Performances

UTC - EGST

Robustness is the priority

Some problems occurred during on-on-lineline experimentation related to HW/SW

13 GSTB-V1 Performances: Comparison respect to UTC

UTC – UTC(k)

For comparison the behavior of some time scales UTC(k) versus UTC is also reported together with EGST it can be seen that remaining within ++--5050 ns is a demandinggg goal, es peciall y considerin g that the UTC (k ) timescales are generated in scientific, manned, laboratories

14 First two Galileo satellites in space GSTB V2 20052005--20102010

GIOVE B launched April 27, 2008 GIOVE A launched on Dec 28, 2005 – 13 stations THE GESS NETWORK – World-wide distribution – Dual GPS+Galileo receivers – GPS needed to synchronize all clocks with the master clock at any time (“common view ” ) – Two master clocks: • GIEN (prime) • GUSN (backup) GIEN INRiM, Turin Italy – GIOVE (and GPS) always in GKIR Kiruna Sweden GKOU Kourou French Guyana view of at least 2 stations (DOC-2) GLPG La Plata Argentina GMAL Malindi Kenya

GMIZ Mizusawa Japan GNNO New Norcia Australia GNOR ESA, Noordwijk The Netherlands

GOUS Dunedin New Zealand GTHT Tahiti French Polynesia GUSN USNO, Washington USA

GVES Vesleskarvet Antarctica GWUH Wuhan China ‰-

THE SENSOR STATION (GESS) • GESS main elements: – Wide-band antenna – GPS+Galileo receiver (GETR)

‰IEN – UPS + computer – Rubidium clock or connectivity 10 MHz frequency to an external signal 1PPS signal clock INRIM Time and Frequency Laboratory

‰Routine activities at INRIM

Free running PPS ‰IENINRIM Measurement Meas ‰PPS UTC(IT)‰UTC(IEN) active H maser Generator‰Generator System‰‰SystemSystem

Time offset [UTC(IT) – H maser ] sampling‰sampling rate: rate: 1 hour1 hour ‰Temperature‰‰-controlled chamber Galileo GSTB V2 Experimental Satellites • First European navigation satellitessatellites in MEO orbit. • Europe meets requirements for Galileo frequency filings. • The H-H-masermaser clock is the most stable clock ever flown in space. • On Board Clock and Sensor Station fully characterised

On ground a network of Sensor Station and an Orbit Determination & Time Synchronization processing similar to GSTB V1 with the addition of GIOVE tracking capabilities and Satellite Control Centers Passive H Maser (GIOVE-B) ‰GIOVE clocks

Rubidium (GIOVE A)

Dynam ic s ta bility

ESA archive http://www.giove.esa.int

Galileo Time Keeping System Setup

Time Service Provider UTC(k) TSP

UTC(k)

UTC(k)

PTF2 PTF1 UTC Precise Time Facility

ESA archive Currently in the

Development o f the Ground Segmentment::

2 Galileo Control Centers

2 Precise Time Facilit ies 1. Kayser Threde consortium

2. Consorzio Torino Time Time scale algorithms • INRIM • TiTorino Wi Wilreless • Finpiemonte • Politecnico di Torino • SEPA • 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 UTC

Galileo Time Service 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)

GNSS timing and new system stimulated good clklock synch roni sati on systemtiming research in time applications metrology good referenceand time involved scale UTC community in GNSS with mutual benefits good algorithms for clock evaluation

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