laser-astrodynamics, space tests of relativity, and gravitational wave astronomy 3 rd international...

Laser-Astrodynamics, Space Tests of Relativity, and Gravitational Wave Astronomy

3rd International ASTROD Symposium – Beijing, China – July 2006

TIME TRANSFER BY LASER LINKThe T2L2 experiment on Jason-2

CNRSO.C.A.

UMR GeminiEtienne SamainJonathan Weick

Patrick VranckenFranck ParaJocelyn ParisRobert DallaDominique

AlbaneseJean-Marie Torre

CNESPhilippe Guillemot

Isabelle PetitbonKarine Gasc

Time Transfer by Laser Link : The T2L2 experiment on Jason-2 - ASTROD 2006

T2L2 on Jason-2

Principle of T2L2

History

T2L2 on Jason-2

Mission’s objectives

Preliminary Performance Budgets

Current status

Conclusion


Principle of T2L2

InstrumentAtmosphereRelativitybrsA t 2

t t X

Time Tagging of laser pulses emitted from a laser station towards the satellite

Start Time at ground station ts (ground clock)

Arrival time at satellite tb (on-board clock)

Return Time at ground station tr (ground clock)

Satellite equipment: Clock, Photo detector and Event Timer, Reflector (CC)

Ground Equipment: Satellite Laser Ranging Station with

Event Timer and Clock

Time Transfer between Ground clock and space clock Triplet Construction for each laser pulse {ts, tb, tr} Computation of the time offset :


Historical Account

1972: Time transfer by laser link concept : LASSO (ESA, CNES)1992: Time transfer between McDonald, Texas and Grasse,

France with LASSO on Meteosat P2

1994: T2L2 Proposal (OCA)1996: T2L2 on MIR 99 (A Phase)1997: T2L2 on ISS with ACES (B Phase)2002: T2L2 on a Microsat Myriade CNES

2005 : T2L2 accepted on JASON 2 as a passenger instrument Phase B : September to December 2005 Phase C/D in progress Instrument delivery : End 2006 Jason-2 launch : Mid 2008


T2L2 on Jason 2

Native Instruments Altimeter: Poseïdon 3 Radiometer: AMS Positioning systems:

Doris – GPS – Laser ranging Passenger Instrument

Radiation Measurements: LPT & Carmen 2

Time Transfer: T2L2

Orbit Altitude 1336 km, i = 66°, P = 6800 s Max distance in common view: 6500 km Single pass: ~1000s Time interval between pass 2h < T < 14h 3 to 6 passes per day

T2L2(Optics)

T2L2(Electronics)


T2L2 Space Instrument Synoptic

Allocations Mass : 8.0 kg (Elec.) + 1.1 kg (Optic) Power : 40 W Volume : 270x280x150 mm3 (Elec.) and 160x116x102 mm3 (Optic - Ø 30x100 & Ø62x100)


Mission’s objectives

Technological validation of optical time transfer Validation of the experiment principle Checking of the accuracy and time stability Enhancement of laser ranging through target effects decorrelation Evaluation of one-way time transfer principle for futures experiments (TIPO)

Scientific applications T/F metrology Fundamental physics

Characterization of the DORIS oscillator through the irradiative environment Studying and measuring of the oscillator’s drift above the South Atlantic

Anomaly (SAA) Correlation with Carmen-2 irradiative measurements Enhancement of the DORIS positioning


Preliminary Performance Budget

Onboard instrument: Resolution: 1 ps Precision: 5 ps Stability:

Phase drift: Uncertainty of time interval measurement 0 lower than time stability x(0) of the clock (for clock with a stability y() = 10-13×-1/2)

Ground station (Tx)Ground station (Rx)AtmosphereGeometryRelativity (negligible)

sfs/6,12K

sps.6,12KτKτKτσ

2

122

1212L2T

2x

τστσ

τστσ4

τσ

4

τστσ

2Relativity

2Atmosphere.x

2Geom.x

2B.x

2R.x

2S.x2

GS.x

Ground to satellite time transfer:

0.1

1

10

100

1000

0 1 10 100 1 000 10 000 100 000 1 000 000 10 000 000 100 000 000

(s)

x() (ps)

AtmosphereGeometryDORIS USOTagging unit (Ground)Tagging unit (Ground - Return)T2L2 instrumentGround to Space Transfer


0.1

1

10

100

1000

0 1 10 100 1 000 10 000 100 000 1 000 000 10 000 000 100 000 000

(s)

x() (ps)

Cold Atoms ClockGround to Ground Transfer (Common view)Ground to Ground Transfer (Non Common view - 300s)Ground to Ground Transfer (Non Common view - 1 000s)Ground to Ground Transfer (Non Common view - 3 000s)TWSTFTGPS - Carrier Phase

Common View Stability:

< 2 ps @ 1000s < 10 ps @ 1 day

Accuracy: < 100 ps Cold atoms clocks

reached from 1000 s on

Non Common View Onboard clock

limitation (DORIS USO) Possibility to calibrate

RF links for > 1 day

Preliminary Performance Budget


Nd

:YA

G

HP5071A Space

HP5071A Ground

Detection Start

Event Timer Ground

Event Timer 2 Space

Detection Return

Detection Space

PPS

Com

mon

C

lock

2.5

km

Space Segment

Ground Segment

MEO Laser

Station

Event Timer 1 Space

0.1

1

10

100

1 10 100 1000 10000 100000

(s)

TV

AR

Sq.

roo

t (ps

)

Time stability Short term Phase white noise :

x (t) = 17×10-12×-1/2 @ 0 = 1 s

Long term Drift: < 5 ps/day

T2L2 Ground Experiment :Experimental Setup


T2L2 Breadboard

Detection Precision: 15 ps Stability (10 Hz, 0 = 0.1 s):

x() = 5×10-12×-1/2

= 0.1 to 300 s x() = 300×10-15×0

> 300 s Drift: < 12 ps / h

Event timer 100 MHz synthesis stability:

x() = 1.3×10-13×-1/2

= 0.01 to 100 s Precision:

2 ps (asynchronous) 1 ps (synchronous)

Stability (synchronous, 0 = 0.025 s): x() = 1.3×10-13×-1/2

= 0.01 to 100 s x() = 8×10-16×0

> 10 s Drift: < 1 ps / h


Current status

Start of the phases C/D

Development of tests models at OCA

Development of the EM & FM

EM tests of performances

FM tests

FM delivery

Integrated tests

Beginning 2006

Jan.-Apr. 2006

May 2006

July 2006

Dec. 2006

Beginning 2007

2007


Conclusion

T2L2 ground experiment Validation of T2L2 performances, time stability close to prediction

T2L2 instrument Breadboard : Results in very good accordance with expectations Engineering Model to be delivered in July for measurements Flight Model delivery scheduled for beginning of 2007

T2L2 offers : Time Transfer at the ps level

One or two orders of magnitude better than existing microwave links Merging of Laser Ranging and Time / Frequency communities

Possibility to link cold atoms clocks and laser station

Launch of Jason 2 scheduled in June 2008 Mission’s duration : 2 years (Jason : 5 yrs)

laser-astrodynamics, space tests of relativity, and gravitational wave astronomy 3 rd international...

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