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T ime T ransfert by L aser L ink T2L2 On Jason 2

T ime T ransfert by L aser L ink T2L2 On Jason 2. OCA –UMR Gemini Grasse – FRANCE Email : etienne.samain@obs-azur.fr E. Samain – Principal Investigator D. Albanese : Optique P. Exertier: Gemini Director M. Furia : Electronic J.F. Mangin : Laser J. Paris : Software F. Pierron: FTLRS

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T ime T ransfert by L aser L ink T2L2 On Jason 2

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  1. Time TransfertbyLaser LinkT2L2 On Jason 2 OCA –UMR Gemini Grasse – FRANCE Email : etienne.samain@obs-azur.fr E. Samain – Principal Investigator D. Albanese : Optique P. Exertier: Gemini Director M. Furia : Electronic J.F. Mangin : Laser J. Paris : Software F. Pierron: FTLRS J.M. Torre: Laser Station - ILRS P. Vrancken : Optical tests J. Weick : error - link Budget - computation CNES Toulouse – France Email : phillipe.Guillemot@cnes.fr P. Guillemot: System Engineer I. Petitbon: Project Manager

  2. Principle • Time Tagging of laser pulses emitted from a laser station in the satellite direction • Start Time at ground Station td (ground clock) • Arrival time at satellite tb (space clock) • Return Time at ground station tr (ground clock) • Time Transfer between Ground clock and Space clock • Triplet Construction for each laser pulse( td, tb, tr) • Computation of the time offset : detector Retro- reflectors clock

  3. Historical account • 1972: Time transfer by laser link concept :LASSO(ESA, CNES) • 1992: time transfer between McDonald and Grasse with LASSO • 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 board JASON 2

  4. Jason 2 • Ocean altimetry at the centimeter level • Native Instruments • Altimeter: Poseïdon 3 • Radiometer • Positioning systems: Doris – GPSP- Laser ranging • Passenger Instrument • Radiation Measurements: LPT & Carmen 2 • Time Transfer : T2L2 • Orbit • Altitude 1336 km, i = 66°, P = 6800 s • Max distance in a common view mode : 6500 km • Time interval between pass 2h < T < 14h • 3 to 6 passes per day

  5. T2L2 Payload • T2L2 Instrument • Event Timer • 2 optical channels: Linear – Geiger • Equipment available on Jason2 • LRA : Laser Ranging Array • DORIS Ultra Stable Oscillator

  6. T2L2 Space Instrument Synoptic

  7. T2L2 Space Instrument

  8. Jason 2Global View

  9. T2L2 Field of view • From Space: +/- 55° for both T2L2 detection and LRA)

  10. Ground StationPerformance Specifications • Event Timer: • Start Time • Return Time • Time stability requirement : below 1 ps over 1000s • Long term time stability: below 100 ps

  11. Laser StationSpecifications • Wavelength 532 nm +/- 0.5 nm • Pulse Width: 20 to 200 ps @ FWHM • Minimum Energy per pulse : 10 mJ ; Nominal Energy: 50 mJ • Maximum  rate: above 1 kHz – Nominal rate: 10 Hz • Elevation range: 5° to 90° • No time synchronisation required

  12. Ground stationEvent timer Status Kit T2L2

  13. OCA Equipment • Time Transfer • TwoWay • GPS mono and multi channels • Clocks • 2 Cesium 5071A • 1 Hydrogen maser • Laser Stations • FTLRS • MeO Station (LLR)

  14. Scientific Objectives Time and Frequency metrology • Optical Laser Link validation • pour t > 10000 s • Uncertainty < 100 ps • Ground clock Synchronization • Compatible with the best clocks available in world • Time scale participation • BIPM/CCD recommandation

  15. Scientific Objectives Time transfer Inter comparison • TWSTFT et GPS calibration • Common view: amelioration : 2 order of magnitude • Possibility to work on very wide bases: synchronization via intermediate ground stations • Possibility to perform a direct GPS time transfer from the GPS satellites to ground via T2L2: direct time tagging of the GPS PPS by the T2L2 space event timer-> GPS time transfer with out atmosphere perturbation • Validation & inter comparison of the ACES MWL

  16. Scientific Objectives Fundamental Physics • Speed of light Anisotropy • Equivalent to the actual measurement: 2,7.10-9 (Oscillator limitation) • Drift of the fine structure constant a • Frequency comparison at the 5 10-17 level over 10 days • Measurement limited by the actual ground clocks performances

  17. Scientific Objectives One way laser ranging validation • Demonstrator of an interplanetary one way laser ranging based on clocks • One way Planetary (or moon) laser ranging

  18. Scientific Objectives Observation & VLBI • Atmosphere • Light level measurement : far field Speckle characterization • VLBI • integration time improvement • Antenna position

  19. Jason-2 objectivesOrbitography • DORIS Oscillator characterization • Radiation and frequency drift correlation with CARMEN-2 & LPT • Laser ranging improvement • One way laser ranging :Arrival time onboard Jason2 can be used to reconstruct echoes • Direct evaluation of the LRA signature by comparison between one way laser ranging and classical laser ranging

  20. Development plan • B Phase: start 09/2005 ; end 01/2006 • CD phases : start 01/2006 ; end 11/06 • Jason2 integration : 01/2007 • T2L2 working group constitution 2006 • T2L2 Ground instrumentation 01/2007 • Laser ranging station upgrade : 2008 • Jason2 Launch : 06/2008 • End of exploitation : 2013

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