Laser-Astrodynamics, Space Tests of Relativity, and Gravitational Wave Astronomy 3 rd International ASTROD Symposium – Beijing, China – July 2006 TIME TRANSFER BY LASER LINK The T2L2 experiment on Jason-2 CNRS O.C.A. UMR Gemini Etienne Samain Jonathan Weick Patrick Vrancken Franck Para Jocelyn Paris Robert Dalla Dominique Albanese Jean-Marie Torre CNES Philippe Guillemot Isabelle Petitbon Karine 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

Time Transfer by Laser Link : The T2L2 experiment on Jason-2 - ASTROD 2006 Principle of T2L2  Time Tagging of laser pulses emitted from a laser station towards the satellite  Start Time at ground station t s (ground clock)  Arrival time at satellite t b (on-board clock)  Return Time at ground station t r (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 {t s, t b, t r }  Computation of the time offset :

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

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

Time Transfer by Laser Link : The T2L2 experiment on Jason-2 - ASTROD 2006 T2L2 Space Instrument Synoptic Allocations  Mass : 8.0 kg (Elec.) kg (Optic)  Power : 40 W  Volume : 270x280x150 mm 3 (Elec.) and 160x116x102 mm 3 (Optic - Ø 30x100 & Ø62x100)

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

Time Transfer by Laser Link : The T2L2 experiment on Jason-2 - ASTROD 2006 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 (  ) = ×  -1/2 )  Ground station (Tx)  Ground station (Rx)  Atmosphere  Geometry  Relativity (negligible) Ground to satellite time transfer:

Time Transfer by Laser Link : The T2L2 experiment on Jason-2 - ASTROD 2006 Common View  Stability:  < s  < 10 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

Time Transfer by Laser Link : The T2L2 experiment on Jason-2 - ASTROD 2006  Time stability  Short term Phase white noise :  x (t) = 17× ×   0 = 1 s  Long term Drift: < 5 ps/day T2L2 Ground Experiment : Experimental Setup

Time Transfer by Laser Link : The T2L2 experiment on Jason-2 - ASTROD 2006 T2L2 Breadboard  Detection  Precision: 15 ps  Stability (10 Hz,  0 = 0.1 s):   x (  ) = 5× ×  -1/2  = 0.1 to 300 s   x (  ) = 300× ×  0  > 300 s  Drift: < 12 ps / h  Event timer  100 MHz synthesis stability:   x (  ) = 1.3× ×  -1/2  = 0.01 to 100 s  Precision:  2 ps (asynchronous)  1 ps (synchronous)  Stability (synchronous,  0 = s):   x (  ) = 1.3× ×  -1/2  = 0.01 to 100 s   x (  ) = 8× ×  0  > 10 s  Drift: < 1 ps / h

Time Transfer by Laser Link : The T2L2 experiment on Jason-2 - ASTROD 2006 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 May 2006 July 2006 Dec Beginning

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