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T IME T RANSFER BY L ASER L INK 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. T IME T RANSFER BY L ASER L INK The T2L2 experiment on Jason-2.

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T IME T RANSFER BY L ASER L INK The T2L2 experiment on Jason-2

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  1. 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 LINKThe T2L2 experiment on Jason-2

  2. T2L2 on Jason-2 • Principle of T2L2 • History • T2L2 on Jason-2 • Mission’s objectives • Preliminary Performance Budgets • Current status • Conclusion

  3. Principle of T2L2 • 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 withEvent 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 :

  4. 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

  5. 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)

  6. 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)

  7. 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

  8. Preliminary Performance Budget • Onboard instrument: • Resolution: 1 ps • Precision: 5 ps • Stability: • Phase drift: Uncertainty of time interval measurement t0 lower than time stability sx(t0) of the clock (for clock with a stability sy(t) = 10-13×t-1/2) • Ground station (Tx) • Ground station (Rx) • Atmosphere • Geometry • Relativity (negligible) Ground to satellite time transfer:

  9. Preliminary Performance Budget 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 t > 1 day

  10. T2L2 Ground Experiment :Experimental Setup • Time stability • Short term Phase white noise : sx (t) = 17×10-12×t-1/2 @ t0 = 1 s • Long term Drift: < 5 ps/day

  11. T2L2 Breadboard • Detection • Precision: 15 ps • Stability (10 Hz, t0 = 0.1 s): • sx(t) = 5×10-12×t-1/2 t = 0.1 to 300 s • sx(t) = 300×10-15×t0 t > 300 s • Drift: < 12 ps / h • Event timer • 100 MHz synthesis stability: • sx(t) = 1.3×10-13×t-1/2 t = 0.01 to 100 s • Precision: • 2 ps (asynchronous) • 1 ps (synchronous) • Stability (synchronous, t0 = 0.025 s): • sx(t) = 1.3×10-13×t-1/2t = 0.01 to 100 s • sx(t) = 8×10-16×t0 t > 10 s • Drift: < 1 ps / h

  12. Current status Beginning 2006 Jan.-Apr. 2006 May 2006 July 2006 Dec. 2006 Beginning 2007 2007 • 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

  13. 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)

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