Navigation Systems Clocks Technologies - SPS...Opticaly Pumped Cesium: BB (TEK SYS / 2002) The...

Atf2004/BeijingPascal RochatSSOM Engelberg 2007

Navigation Systems Clocks Navigation Systems Clocks TechnologiesTechnologies

P. Rochat, F. Droz, P. Mosset, G. Barmaverain, Q. Wang, D. BovingTemex Neuchâtel Time, Switzerland

L. Mattioni, Marco BelloniGalileo Avionic, Italy

Ulrich Schmidt, Timothy PikeAstrium/EADS, Germany

Francesco Emma, Pierre WallerESA-ESTEC, Netherlands

Pascal Rochat SSOM Engelberg 2007

Presentation OutlinePresentation Outline1. Development Steps , Performances and Status of

the Galileo Space Clocks 2. Evaluation of the accuracy of the Space Clocks

taking into account measurement noise induced by geodetic technique in measuring and predicting the Space Clocks

3. On board Galileo Time Keeping 4. On ground system clock generation5. Conclusions


Galileo program descriptionGalileo program description

Global Navigation Satellite System Jointed by EC & ESAConstellation

30 satellites 3 circular MEOsAltitude 23222kmInclination 56o

Mission life time of 12 yearsClock model update < 10’000 sec.(TBC)Metric/sub-metric navigation accuracy - 1 to 3 ns clock model error

Introduction 1Introduction 1


Onboard Clocks for Galileo Onboard Clocks for Galileo Development HistoryDevelopment History

Two baseline clock technologiesRubidium Atomic Frequency Standard(RAFS)Passive Hydrogen Maser (PHM)

Long heritage for both clocks in Switzerland since ’80sContinuous support from ESA & Swiss Space Office especially since set-up of the GNSS2 program



InIn--progress GSTBprogress GSTB--V2V2

Two experimental satellites due for launch end of 2005 & 2006 for:

Frequency FillingTest of critical technologies (like clocks)Experimentation on Galileo SignalsCharacterisation of MEO environment

Navigation Payload embarkingOne PHM unit and two RAFS units (GIOVE-B)Two RAFS unit (GIOVE-A)

First Flight Opportunity for Galileo Clocks Validation !



GIOVE SatellitesGIOVE Satellites


Development MilestonesDevelopment Milestones

-----------Three models delivered for Giove B in 2005 - 2006

6 models delivered for Giove A & Giove BSatellites in 2005

FMs or PFMs

-----------Qualifications in 2006Qual. Tests completedRad test (CNES) Q1/2003

QM

-----------Industrialisation and EQM Completed by Q4/2003 by GA&TNT

5 models in specs in 2002Lifetime still on-going

EQMs

Will start in Thales in 2006

Completed by Q2 / 2003 by ON&GA

Completed in 2000EM

< 3E-12*τ-1/2 on gnd Cs OP tube in 2002

Based on VREMYA design +ON/GA analysis (1999)

completed in 1995BB

OPCsSPHMRAFSSteps


RAFS for GIOVE_ARAFS for GIOVE_A

EPC

Cold base-plate

RAFS core

Power connector

TM/TC connector

RF connector


Oven including theRb spectral lampand the microwavecavity with Rb cell

Intermediatethermallyregulated base-plate

Cold base-plate

EPC

Volume allocatedto harness

Holes for externalconnectors

Stainless steel feet

RAFS internal constructionRAFS internal construction


1.0E-11

1.0E-10

1.0E-09

1.0E-08100 1000 10000 100000

Averaging Time, sec. Ti

me

Dev

., Si

gma

x (T

), se

c

1.0E-14

1.0E-13

1.0E-12100 1000 10000 100000

Averaging Time, sec.

Alla

n D

ev.,

Sigm

a y

(T)

Performance AchievedPerformance AchievedRAFS: Frequency & Time Stability RAFS: Frequency & Time Stability

Drift removed: 2E-13 / day

Temperature: +-1°C


GSTBGSTB--V2 RAFS2 Measurement ResultsV2 RAFS2 Measurement Results

1.0E-14

1.0E-13

1.0E-12

1.0E-111 10 100 1000 10000

Averaging time, T, in seconds

Alla

n de

viat

ion,

sig

ma

y (T

RAFS Spec.

PFM (GIOVE-B)

FM1 (GIOVE-B)

FM2 (Spare)

FM3 (Spare)

FM4 (GIOVE-A)

FM5 (GIOVE-A)

Frequency stability of GSTB-V2 RAFS (Q4 2005) drift removed


RAFS2 for GSTBRAFS2 for GSTB--V2 Performance V2 Performance AchievedAchieved

Frequency stability: < 4x10-14 @ 10’000 sec Flicker floor : < 3x10-14(drift removed) Thermal sensitivity: < 5x10 -14 /°CMagnetic sensitivity: < 1x10-13 / GaussMass and volume: 3.2 kg and 2.4 lt


GIOVEGIOVE--A Preliminary A Preliminary information (FM4 and FM5)information (FM4 and FM5)

Start: Several start sequences all 100% nominalRb Light TM: Nominal values and perfectly stableRb Signal TM: Nominal values and perfectly stableOperating Temp.:Nominal Power: Nominal

Ground segment measurements showing almost same stabilities values than on ground .


RAFS3 further improvementsRAFS3 further improvementsGoal < 1 EGoal < 1 E--14 / day 14 / day


Passive Hydrogen Maser for Passive Hydrogen Maser for GalileoGalileo

Complete clock delivered for Giove B sat


PHM/FM Performance ImprovementPHM/FM Performance Improvement

1.E-15

1.E-14

1.E-13

1.E-12

1.E-11

10 100 1000 10000 100000

Averaging time, τ, Seconds

Ove

rlapp

ing

Alla

n De

viat

ion

σy( τ

)

PFM, Apr.05FM1, January 06Spec

Significant improvements obtained between PFM and FM models by improving cavity quality factor

Drift: <5E-15/day


PHM for GSTBPHM for GSTB--V2 V2 Performance AchievedPerformance Achieved

Frequency stability: < 7x10-13 x t -1/2

(1s < t < 10'000s ) Flicker floor : < 6x10-15

Drift: < 5x10-15/ dayThermal sensitivity: < 3x10-14/°CMagnetic sensitivity: < 4x10-14/GaussMass and volume: 18 kg and 28 lt


PHM Life TimePHM Life Time

12 years orbit life + 1 year ground storageThe orbit life is limited by• Size of hydrogen container• Bulk getters mass (hydrogen sorption

capacity)• Ion pump sorption capacity (for

background gases)• Total dose of ionising radiation


HH22 Consumption testConsumption test

H2 container with the capacity of 25 bar.l is sufficient for 12-years life time, taking account of the margin.

Measurement of H2 Consumption, 02-07 June 2005TM2, at nominal flux (low pressure=0.1mbar)

y = -0.203x + 7821.539R2 = 0.996

4.8

5.0

5.2

5.4

5.6

5.8

6.0

6.2

02.06.05 03.06.05 04.06.05 05.06.05 06.06.05 07.06.05 08.06.05Date

H2 H

igh

Pres

sure

[bar

]

V=20.6cm3

Q=0.2029719*365*0.0206 =1.53 bar.liter/year

PHM Life Time Factor 1: PHM Life Time Factor 1: HH22 ContainerContainer


PHM getters & high vacuum PHM getters & high vacuum chamberchamber


HH22 Sorption Test on Getter CartridgeSorption Test on Getter Cartridge

Capable of sorbing the required amount of H2of 20 bar*l.Base pressure after sorption was in the low e-7 mbar range with only the getter cartridge pumping.

Sep. ’03 at SAES Getter S.p.A

PHM Life Time Factor 2: PHM Life Time Factor 2: Novel Custom Built Getter PumpNovel Custom Built Getter Pump


PHM for GSTBPHM for GSTB--V2 Qualification V2 Qualification StatusStatus

Vibration: Ok

Shock: Ok

EMC/EMI: Ok

Thermal Vacuum: Ok


Opticaly Pumped Cesium: BB (TEK SYS / 2002)Opticaly Pumped Cesium: BB (TEK SYS / 2002)

The compact optically pumped cesium beam clock developed by Tekelec Systemes with the scientific support of the SYRTE exhibits a frequency stability of 3.10-12τ-1/2 measured against a hydrogen maser as a reference in 2002.The sealed tube works under a low atomic flux consistent with lifetime of 8 years or more. It uses a 22 cm long Ramsey cavityThe compact 3 cm wide optical bench is rigidly fixed along the tube which length is 45 cm.


OPCs :BB Stability (TEK SYS/ dec 2002)OPCs :BB Stability (TEK SYS/ dec 2002)


Clock model & prediction time error:Clock model & prediction time error:

predictive system : error will be the difference between the predictive system : error will be the difference between the clock phaseclock phase--time & the establish clock model from previews time & the establish clock model from previews

collected data.collected data.

0 2 0 0 0 0 4 0 0 0 0 6 0 0 0 0 8 0 0 0 0 1 0 0 0 0 0

- 1 x 1 0 - 9

0

1 x 1 0 - 9

2 x 1 0 - 9

3 x 1 0 - 9

4 x 1 0 - 9

5 x 1 0 - 9

6 x 1 0 - 9

Clock phase

Clock model

Error


Prediction Time error for S_PHM: Prediction Time error for S_PHM: G-S-PHM

Tm=8h, Tp=6h

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

0.0E+00 1.0E+05 2.0E+05 3.0E+05 4.0E+05 5.0E+05 6.0E+05Time / sec

Pred

ictio

n tim

e er

ror /

ns

Linear Quadratic

dTRMS(Tp)=0.226 dTRMS(Tp)=0.454 dTRMS(0-Tp)=0.151 dTRMS(0-Tp)=0.271

Tm = Measurement Time

Tp = Prediction TimeComputed by Q. Wang

Method: Curve fitting during Tm

Plot: Diff. Between fit and meas. data


Prediction Time error for S_PHM: Prediction Time error for S_PHM: G-S-PHM

Tm=24h, Tp=12h

-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

2.5

0.0E+00 1.0E+05 2.0E+05 3.0E+05 4.0E+05 5.0E+05 6.0E+05Time / sec

Pred

ictio

n tim

e er

ror /

nsLinear Quadratic


Computed by Q. Wang


Prediction Time error for RAFS:Prediction Time error for RAFS:RAFS

Tm=8h, Tp=6h

-6

-4

-2

0

2

4

6

0.0E+00 1.0E+05 2.0E+05 3.0E+05 4.0E+05 5.0E+05 6.0E+05Time / sec

Pred

ictio

n tim

e er

ror /

ns

Linear Quadratic


Computed by : Q. Wang


Prediction Time error for RAFSPrediction Time error for RAFSRAFS

Tm=24h, Tp=12h

-6

-4

-2

0

2

4

6

0.0E+00 5.0E+04 1.0E+05 1.5E+05 2.0E+05 2.5E+05 3.0E+05 3.5E+05 4.0E+05 4.5E+05 5.0E+05

Time / sec

Pred

ictio

n tim

e er

ror /

ns

Linear Quadratic


Computed by : Q. Wang


Prediction Time error for OPCsPrediction Time error for OPCsOP-G-Cs

Tm=8h, Tp=6h

-5

-4

-3

-2

-1

0

1

2

3

4

0.0E+00 2.0E+05 4.0E+05 6.0E+05 8.0E+05 1.0E+06 1.2E+06Time / sec

Pred

ictio

n tim

e er

ror /

ns

Linear Quadratic


Data collected by TEKELEC SYSTEME on OPCs BB model


Prediction Time error for OPCsPrediction Time error for OPCs

Data collected by TEKELEC SYSTEME on OPCs BB

OP-G-CsTm=24h, Tp=12h

-6

-4

-2

0

2

4

6

0.0E+00 2.0E+05 4.0E+05 6.0E+05 8.0E+05 1.0E+06 1.2E+06

Time / sec

Pred

ictio

n tim

e er

ror /

nsLinear Quadratic



RMS of Prediction Time Error:RMS of Prediction Time Error:Tm=8h

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

0 1 2 3 4 5 6

Prediction time Tp /h

RM

S of

pre

dict

ion

time

erro

r /ns

G-S-PHMOP-G-CsRAFS

Linear model

Method : RMS calculation of all error values after Tp

Tm=24h

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

0 2 4 6 8 10 12


RM

S of

pre

dict

ion

time

erro

r /ns

G-S-PHM, LinearOP-G-Cs, LinearRAFS, Quadratic


RMS of Prediction Time Error Tm=8h

Tm=8h

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

0 1 2 3 4 5 6


RM

S of

pre

dict

ion

time

erro

r /ns

G-S-PHMOP-G-CsRAFS

Linear model


Computed by : Q. Wang / G. Busca

Without geodetic measurement noise

Tm=8h, including the present measurement noise

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

0 1 2 3 4 5 6


RM

S of

pre

dict

ion

time

erro

r /ns

G-PHMOP-G-CsRAFS

Linear model

With present geodetic measurement noise


RMS of Prediction Time Error Tm=24h


Tm=24h

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

0 2 4 6 8 10 12


RM

S of

pre

dict

ion

time

erro

r /ns

G-S-PHM, LinearOP-G-Cs, LinearRAFS, Quadratic

Without geodetic measurement noise

Tm=24h, including the present measurement system noise

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

0 2 4 6 8 10 12


RM

S of

pre

dict

ion

time

erro

r /ns

G-PHM, LinearOP-G-Cs, LinearRAFS, Quadratic

With present geodetic measurement noise


Conclusions: Conclusions: With the present S_Clocks measurement system noise, and prediction time up to 6 hours , the S_RAFS is adequate.

For future measurement system noise which are expected to improve by factor of 3 , the S_PHM will be the more adequate clock for prediction time up to 24 hours.

Navigation accuracy less than 1 m can be achieved with up to 6 hours autonomy with RAFS and up to several days with passive Maser

Cesium clock degrading accuracy while not improving autonomy


Galileo OnGalileo On--Board Clocks ensemble Board Clocks ensemble

SWITCH MATRIX 2:4

DDS synthesiser

DDS synthesiser

Controller

Phasemeter

I/F

Select and adjust frequency

Phase discrimination

10.23 MHz

FGU

UDC/DC

CMCU

10.23 MHz

10.23 MHz

10 MHz

10 MHz

10 MHz

10 MHz

To S/S

RTU BUS

S-RAFS 1

TM/TC

S-PHM 2

TM/TC

S-RAFS 2

TM/TC

S-PHM 1

TM/TC

Power

Mis

sion

SAR

TT&

C

SWITCH


Navigation System Time reference Navigation System Time reference generation (ground segment) shall meet generation (ground segment) shall meet

following requirementsfollowing requirements

Be linked to UTC time or other navigation system (s) for inter-operability purposesBe equipped with booth long term & short term stability clocksAutonomous switching of redundant master clocksBe linked to system by physical generation of time signal to at least one geodetic ground observation station.System time shall be generated within 1 ns stability for weeks in order to guarantee proper on board clocks stabilities and set-up on board clocks modelling.


Time stability

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

1.E+01

1.E+02

1.E+03

1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06

Observation time [s]

σX(τ)

[n

s]

S-RAFS Drift removedS-PHM Drift removedG-AHM Drift removedG-CSTWSTFT noise floor

Space and Ground Clocks Time Stability


Exemple ofSystem Time generation Architecture

G-CS3

G-CS2

G-CS1

Precisephase timecomparator

G-AHM1

G-AHM1

Time IntervalCounter

Phase St.

Phase St.

Logic

Ampl PPS

Ampl 10MHz

TWSTFT

GeodeticGalileo

Receiver

Meteo sensor

Computer

Interface toOSPF

Interface to externalservice provider

Interface toMCF

OOL

OOL

OOL

OOL

OOL

10MHz

10MHz

10MHz

10MHz

10MHz

PPS

PPS

PPS

PPS

PPS

PPS

PPS

PTF


ConclusionsConclusionsQualified clocks technologies Qualified clocks technologies

Offering:Offering:1. Metric / sub metric navigation accuracy2. Up to one week autonomy capability with on board Maser

technology3. Cold + Hot Redondancy on board of each satellite4. Clocks lifetime expectation of 14 years or more 5. Simple & Mature Technologies offering room for

improvements in term of mass & performances6. Existing groung maser clocks offering better stability than

Cesium for inter-operable navigation system linked with precise time transfert equipments


Thank you very Thank you very much for your much for your

attention attention

[email protected]@temextime.comOr Or

[email protected]@t4science.com

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