Calern, September 23, 2008 Patrick Vrancken – Characterization of T2L2 & Micrometric Laser Ranging page 1 Characterization of T2L2 (Time Transfer by Laser Link) on the Jason 2 ocean altimetry satellite and Micrometric Laser Ranging Patrick Vrancken Thesis Presentation

Calern, September 23, 2008 Patrick Vrancken – Characterization of T2L2 & Micrometric Laser Ranging page 2 Part I: Micrometric Laser Ranging for ILIADE Part II: Characterization of T2L2 (Time Transfer by Laser Link) on the Jason 2 ocean altimetry satellite

Calern, September 23, 2008 Patrick Vrancken – Characterization of T2L2 & Micrometric Laser Ranging page 3 Part I – Towards Micrometric Laser Ranging for ILIADE Agenda: 1.The ILIADE project at OCA 2.Feasibility study experiments 3.Conclusion

Calern, September 23, 2008 Patrick Vrancken – Characterization of T2L2 & Micrometric Laser Ranging page 4 Part I – Towards Micrometric Laser Ranging for ILIADE Agenda: 1.The ILIADE project at OCA Motivation Principle ILIADE baseline experiment 2.Feasibility study experiments 3.Conclusion

Calern, September 23, 2008 Patrick Vrancken – Characterization of T2L2 & Micrometric Laser Ranging page 5 The ILIADE project at OCA Motivation Two groups with complementary competences at OCA oARTEMIS: –Development of ultra-precise laser interferometers, laser stabilization (VIRGO development) –Sub-wavelength precision (down to picometer); no absolute notion ( /2 ambiguity) oGEMINI / GéoSciences Azur: –Time-of-flight based laser ranging –Absolute distance measurement with mm precision ILIADE: combining both aspects in a common absolute distance measurement approach aiming for sub-micron precision Various applications in future space missions needing highly precise, absolute distance metrology oNG space telescopes, Earth gravity missions oFundamental physics missions

Calern, September 23, 2008 Patrick Vrancken – Characterization of T2L2 & Micrometric Laser Ranging page 6 The ILIADE project at OCA The ILIADE principle Unify complementary technologies in a single approach: oInterferometric measurement on the optical carrier oTime-of-flight measurement on the modulated optical carrier (laser pulses) Utilization of frequency combs (femtosecond lasers) These lasers make the link from the radiofrequency to the optical world Possibility to transfer the long term stability and accuracy of atomic clocks (RF or optical) of (e.g.) to the frequencies of this type of laser Absolute distance measurements on this scale, i.e. dl/l = (e.g. nanometric over a distance of 1000km) f t

Calern, September 23, 2008 Patrick Vrancken – Characterization of T2L2 & Micrometric Laser Ranging page 7 The ILIADE project at OCA The ILIADE baseline experiment Baseline: Michelson-type interferometer oFrequency comb oInterferometer (heterodyne) oTOF measurement Supercontin uum generation Frequency comb Cs-clock f-2f comparison f ceo f rep Reference arm Measurement arm Retroreflec tor Line filter nּf rep EOM Event timer Heterodyne detection Line filter (n+1)ּf rep Phase measurement Interferometric phase Absolute distance Beat note: f rep t tt Goal of TOF: Resolve wavelength scale  Link to interferometric measurement

Calern, September 23, 2008 Patrick Vrancken – Characterization of T2L2 & Micrometric Laser Ranging page 8 Part I – Towards Micrometric Laser Ranging for ILIADE Agenda: 1.The ILIADE project at OCA 2.Feasibility study experiments 3.Conclusion

Calern, September 23, 2008 Patrick Vrancken – Characterization of T2L2 & Micrometric Laser Ranging page 9 Feasibility study experiments Feasibility experiments for time-of-flight measurement (1) For TOF only possible with averaging over a large data set  Augment number of measurements, thus acquisition rate Precursor experiments with T2L2 test bed equipment: oSimplified setup (no Michelson) to evaluate detection system oModelocked 100 MHz (FWHM=17 ps), pulse pickers (EOM) at 2 kHz oOne single InGaAs PIN (BW = 3 GHz) oDassault event timer (precision 2 ps) 1.Laser synchronized to Cs clock → synchronous measurement 2.Laser cavity clock mode (to mitigate instability of laser sync. PLL)  Time stability of 100 fs after 1 s integration time (at 2 kHz) HighQ laser Event timer Event timer ÷10 division Pulse pickers Clock - Freq. ref.

Calern, September 23, 2008 Patrick Vrancken – Characterization of T2L2 & Micrometric Laser Ranging page 10 Feasibility study experiments Feasibility experiments for time-of-flight measurement (2) Precursor experiments with T2L2 test bed equipment: oSimplified setup (no Michelson) oModelocked 100 MHz (FWHM=17 ps) with electronic pulse picking at 2 kHz: no amplitude noise from pulse pickers o2 InGaAs PIN (BW=3GHz) oDassault event timer (precision 2 ps and 5 ps); measurement rate: 2 kHz 1.Laser locked to Cs clock, differential acquisition  Time stability of 20 fs after 40 s (at 2 kHz; 80,000 measurements) – micron scale! Clock - Freq. ref. HighQ laser Logic division Event timer Event timer Signal generator Logic division

Calern, September 23, 2008 Patrick Vrancken – Characterization of T2L2 & Micrometric Laser Ranging page 11 Part I – Towards Micrometric Laser Ranging for ILIADE Agenda: 1.The ILIADE project at OCA 2.Feasibility study experiments 3.Conclusion

Calern, September 23, 2008 Patrick Vrancken – Characterization of T2L2 & Micrometric Laser Ranging page 12 Conclusion Part I Basic concept for the unification of interferometry on the optical carrier and the TOF measurement on the modulated carrier has been developed oThis concept is under continuous evolution –Cooperation with ICB of University of Bourgogne –Supply of a high repetition rate laser source (20 GHz) oAbsolute distance metrology of importance for many future scientific space missions  > Three orders of magnitude of improvement in time of flight measurement Precursor experiments with T2L2 test bed equipment showed: oWavelength range (fs-level) comes into reach: Time stability of 20 fs (6  m) has already been demonstrated after some tens of seconds integration time (80,000 measurements) Needed tenfold improvement - two fronts that is worked on: oMinimize inherent (single-shot) precision (BW ↑), currently some picoseconds oMaximize measurement rate Challenge: Long term stability of measurement Design of adapted photodetection and event timer under preparation

Calern, September 23, 2008 Patrick Vrancken – Characterization of T2L2 & Micrometric Laser Ranging page 13 Part I – Towards Micrometric Laser Ranging for ILIADE Agenda: 1.The ILIADE project at OCA 2.Feasibility study experiments 3.Conclusion End of Part I

Calern, September 23, 2008 Patrick Vrancken – Characterization of T2L2 & Micrometric Laser Ranging page 14 Part II – The Time Transfer by Laser Link Experiment Agenda: 1.T2L2 on the Jason 2 satellite 2.Characterization of the T2L2 flight instrument 3.Error budget for the T2L2 time transfer system 4.Conclusion & Status

Calern, September 23, 2008 Patrick Vrancken – Characterization of T2L2 & Micrometric Laser Ranging page 15 Part II – The Time Transfer by Laser Link Experiment Agenda: 1.T2L2 on the Jason 2 satellite Time transfer with T2L2 T2L2 on the Jason 2 ocean altimetry satellite Goals of T2L2 on the Jason 2 satellite Design of T2L2 for the Jason 2 satellite 2.Characterization of the T2L2 flight instrument 3.Error budget for the T2L2 time transfer scheme 4.Conclusion & Status

Calern, September 23, 2008 Patrick Vrancken – Characterization of T2L2 & Micrometric Laser Ranging page 16 T2L2 on the Jason 2 satellite Time transfer by laser link: Comparing clocks T2L2 principle: oGround equipment: SLR station with event timer and clock oSatellite equipment: Clock, photo detector and event timer, reflector oTime tagging of laser pulses emitted from a laser station towards satellite –Start time at ground station t s (ground clock) –Return time at ground station t r (ground clock) –Arrival time at satellite t b (on-board clock) oTime transfer between ground clock and space clock –Triplet construction for each laser pulse {t s, t b, t r } –Computation of the time offset between the clocks A and B: Advantages of an optical system as compared to typical RF time transfer systems such as GPS and TWSTFT: oFrequency insensitive to ionosphere oCarrier permits higher modulation BW oMono-carrier, true two-way scheme

Calern, September 23, 2008 Patrick Vrancken – Characterization of T2L2 & Micrometric Laser Ranging page 17 T2L2 on the Jason 2 satellite T2L2 on the Jason 2 ocean altimetry satellite 2005: T2L2 accepted on JASON 2 as a passenger instrument oSpecific design for Jason 2: Instrument development (phase B) started in Sept oPreliminary Design Review (PDR) in December 2005 oManufactured by EREMS and SESO oCritical Design Review (CDR) in May 2006 oDelivery of T2L2 flight model in February 2007 Native Instruments oAltimeter: Poseïdon 3 oRadiometer: AMS oPositioning systems: –Doris, GPS, Laser ranging Passenger Instruments oRadiation Measurements: –LPT –Carmen 2 oTime Transfer: T2L2

Calern, September 23, 2008 Patrick Vrancken – Characterization of T2L2 & Micrometric Laser Ranging page 18 T2L2 on the Jason 2 satellite Goals of T2L2 on Jason 2 Validation of T2L2 scheme oFunctional validation of T2L2 oValidation of one-way laser ranging Scientific objectives oComparison of ground clocks oCalibration of other time transfer systems oContribution to international time scales oFundamental physics Jason 2 mission related objectives oCharacterization of DORIS USO oJason 2 altimetry

Calern, September 23, 2008 Patrick Vrancken – Characterization of T2L2 & Micrometric Laser Ranging page 19 T2L2 on the Jason 2 satellite Design of T2L2 on Jason 2 (1 - Optics) T2L2 optical subsystem with two optics: oImage FOV ( ±55° ) on photodetector –Spectral filter (noise reduction) –Neutral density filter with radial distribution for laser pulse energy adjustment oNon-linear channel: precise timing –APD Geiger mode: Voltage above breakdown –Features photon-number dependent time walk oLinear channel: –System trigger: Arming of non-linear channel –Laser pulse level measurement (time walk correction) –Measurement of continuous background radiation + LRA (provided by Jason 2 mission)

Calern, September 23, 2008 Patrick Vrancken – Characterization of T2L2 & Micrometric Laser Ranging page 20 T2L2 on the Jason 2 satellite Design of T2L2 on Jason 2 (2 - Electronics) T2L2 electronic subsystem: oDetection Electronics: –Cw background noise measurement –Laser pulse amplitude measurement –Triggering of Geiger APD –Detection threshold oEvent timer: –Counter for rough timing (FPGA) –Double vernier for precise timing (res.: 1.4 ps) oOther: control, TM/TC, power supply + DORIS USO (provided by Jason 2)

Calern, September 23, 2008 Patrick Vrancken – Characterization of T2L2 & Micrometric Laser Ranging page 21 Part II – The Time Transfer by Laser Link Experiment Agenda: 1.T2L2 on the Jason 2 satellite 2.Characterization of the T2L2 flight instrument Metrological test bed Performed tests and analyzed data: Calibration and performance data 3.Error budget for the T2L2 time transfer scheme 4.Conclusion & Status

Calern, September 23, 2008 Patrick Vrancken – Characterization of T2L2 & Micrometric Laser Ranging page 22 Characterization of the T2L2 instrument Motivation / goals: oInstrument has to be thoroughly calibrated in order to: –Employ it at the best (i.e. for metrological performance) operation point –Dispose of calibration data for the reduction/correction of the raw data oInstrument’s performance has to be rigorously examined in order to: –Verify the fulfillment of the specifications –Be able to establish a thorough error budget as a comparative value during exploitation  Characterization of the flight model is of vital importance for attaining mission goals Methods / tools: oDevelopment of metrological test bed for the T2L2 instrument oExecution of test campaigns on the T2L2 flight model –March/April 2007 CNES, Toulouse: T2L2 flight model stand-alone tests –June/July 2007 Thales Alenia Space, Cannes: T2L2 + DORIS during integration oAnalysis of the gained data oEstablishment of an error budget for the whole time transfer scheme  These work packages are integral part of the present thesis

Calern, September 23, 2008 Patrick Vrancken – Characterization of T2L2 & Micrometric Laser Ranging page 23 Characterization of the T2L2 instrument The metrological test bed (1) Optical bench: Supply well-defined laser pulses to T2L2 optics oNd:YVO 4 mode locked laser: Generation of a 100 MHz pulse train of IR (1064 nm) laser pulses (FWHM 20 ps) oPulse picking system: selectable repetition rate (1 Hz to 5 MHz) oFrequency doubling of IR pulses to 532 nm oControl of pulse energy oBeam distribution: Generation of two parallel, displaceable beams > T2L2 optics oTwo-axis motorized mount for attitude simulation

Calern, September 23, 2008 Patrick Vrancken – Characterization of T2L2 & Micrometric Laser Ranging page 24 Characterization of the T2L2 instrument The metrological test bed (2) Optical bench: oDeparture and return detectors: Timing reference oDetectors for beam power and beam profile measurement oBackground noise simulation: White LED grid and cw green diode laser Time Frequency and Control Electronics: oDifferent clocks: Cs-Std, H-Maser, Rubidium, DORIS supplying reference signal to T2L2 oEvent timer (Dassault): Reference timing oElectronic signals (ECL pulses) for pure electronic operation oControl PC and electronics + software

Calern, September 23, 2008 Patrick Vrancken – Characterization of T2L2 & Micrometric Laser Ranging page 25 Characterization of the T2L2 instrument The metrological test bed (3) Test bed version for CNES campaign Test bed version for Thales Alenia Space campaign (during integration)

Calern, September 23, 2008 Patrick Vrancken – Characterization of T2L2 & Micrometric Laser Ranging page 26 Characterization of the T2L2 instrument Performed tests: Calibration of time-walk correction Calibration of non-linear channel signal propagation time (time walk) Calibration of laser pulse energy measurement (linear channel)

Calern, September 23, 2008 Patrick Vrancken – Characterization of T2L2 & Micrometric Laser Ranging page 27 Characterization of the T2L2 instrument Performed tests: Precision of timing (non-linear detection) Timing precision over photon number: o30 ps in single-photon mode (as compared to 20 ps on the Engineering Model) o3 to 5 ps in multi-photon mode Coupling of the non-linear channel optics: Less sensitive (factor 4.7) than specified: Deterioration of link budget  Non-linear detector misalignment Coupling of the linear channel optics according to specification

Calern, September 23, 2008 Patrick Vrancken – Characterization of T2L2 & Micrometric Laser Ranging page 28 Characterization of the T2L2 instrument Performed tests: Precision and time stability Event timer precision/stability in external electronic signal (ECL) mode Optical timing: Precision/stability for laser pulses (here single photon mode)

Calern, September 23, 2008 Patrick Vrancken – Characterization of T2L2 & Micrometric Laser Ranging page 29 Characterization of the T2L2 instrument Performed tests: Attitude - Characterization of optics Characterization of optics’ response Linear channel Non-linear channel  Determination of differential transmission between linear and non-linear channel

Calern, September 23, 2008 Patrick Vrancken – Characterization of T2L2 & Micrometric Laser Ranging page 30 Characterization of the T2L2 instrument Performed tests: Characterization of DORIS oscillators Experiment during integration of DORIS and T2L2 in Jason 2 Oscillator frequency (USO PMA and PMB) oFrequency accuracy : |df/f| < oFrequency drift oFrequency drift deceleration (oscillator warm-up phase) Time variance: Phase data correction with polynomial

Calern, September 23, 2008 Patrick Vrancken – Characterization of T2L2 & Micrometric Laser Ranging page 31 Part II – The Time Transfer by Laser Link Experiment Agenda: 1.T2L2 on the Jason 2 satellite 2.Characterization of the T2L2 flight instrument 3.Error budget for the T2L2 time transfer system Involved contributors to error budget Error budget 4.Conclusion & Status

Calern, September 23, 2008 Patrick Vrancken – Characterization of T2L2 & Micrometric Laser Ranging page 32 Error budget for the T2L2 time transfer Contributors to error budget Instrument on Jason 2: oT2L2 instrument oDORIS USO oLRA retro-reflector oGeometry Laser stations: oStart detection oReturn detection oTimer oSLR calibration oCalibration between clock and SLR system Other: oRelativity oAtmosphere

Calern, September 23, 2008 Patrick Vrancken – Characterization of T2L2 & Micrometric Laser Ranging page 33 Error budget for the T2L2 time transfer Time stability budget for clock to clock time transfer Ground to ground time transfer in common view – time stability  x oSumming the two ground to space time transfers: Non-common view: Include time prediction error of DORIS USO: Some hundred picoseconds oUse of intermediate ground stations in order to reduce dead time oMonitoring of USO

Calern, September 23, 2008 Patrick Vrancken – Characterization of T2L2 & Micrometric Laser Ranging page 34 Error budget for the T2L2 time transfer Time transfer uncertainty Uncertainty governed by systematics oJason 2 instrumentation: –Timer & DORIS negligible –Photodetection – timing error due to time walk correction: 1.5 to 7 ps (depending on photon level) –Geometry (mechanical uncertainty): 3 ps oGeneral relativity and atmosphere negligible oGround station instrumentation: –SLR system internal calibration measurement uncertainty about the distance d Cal : 15 ps –Calibration between SLR system (its four-dimensional reference point) and its counterpart in the time/frequency laboratory (or simply a clock): 25 ps (OCA plans dedicated calibration campaign) Combined uncertainty sums up to: less than 50 ps for ground to ground time transfer in common view  Nearly two orders of magnitude better than for RF systems

Calern, September 23, 2008 Patrick Vrancken – Characterization of T2L2 & Micrometric Laser Ranging page 35 Part II – The Time Transfer by Laser Link Experiment Agenda: 1.T2L2 on the Jason 2 satellite 2.Characterization of the T2L2 flight instrument 3.Error budget for the T2L2 time transfer scheme 4.Conclusion & Status

Calern, September 23, 2008 Patrick Vrancken – Characterization of T2L2 & Micrometric Laser Ranging page 36 Conclusion Conclusion of the characterization of T2L2 Calibration of the instrument oGeneration of a comprehensive set of high-quality data for establishing data reduction algorithms (realized by the CMS of OCA) Performance of the instrument: oIdentification of some (minor) issues: –Coupling of non-linear detector: misalignment  Loss in sensitivity & precision (single h ) –Generation of event timer calibration pulses oFlight model reaches the expected (and specified) level of performance –Event timer intrinsic precision of < 2 ps, minimum time stability of 50 fs over 1,500 s –Optical timing: Precision of 30 ps in single-photon mode; 3 ps for 1,000 photons –Detection and timing over five orders of magnitude of optical power Performance of the time transfer with T2L2: oTime stability of some ps over some hundred seconds integration time in common view  Time transfer of today’s most advanced clocks oNon-common view mode deteriorated by USO: Precision of some hundred ps – Workaround: Employing intermediate SLR stations oUncertainty of time transfer: 50 ps allows for calibration of other time transfer systems

Calern, September 23, 2008 Patrick Vrancken – Characterization of T2L2 & Micrometric Laser Ranging page 37 Status Status of the T2L2 experiment (1) Jason 2: oIntegration on Jason 2 finished in July 2007 oSatellite level tests performed from July 2007 to January 2008 oLaunch on June 20, 2008 T2L2: oSwitched ON on June 25 oOptical timing mode first activated on June 30 oCMS is currently adjusting triplet identification algorithms

Calern, September 23, 2008 Patrick Vrancken – Characterization of T2L2 & Micrometric Laser Ranging page 38 Status Status of the T2L2 experiment (2) Data sample: Laser energies from different laser stations:

Calern, September 23, 2008 Patrick Vrancken – Characterization of T2L2 & Micrometric Laser Ranging page 39 Status Status of the T2L2 experiment (3) Data sample (CMS): Onboard time – ground time (for six laser stations) Data sample (CMS): Zoom on FTLRS

Calern, September 23, 2008 Patrick Vrancken – Characterization of T2L2 & Micrometric Laser Ranging page 40 Part II – The Time Transfer by Laser Link Experiment Agenda: 1.T2L2 on the Jason 2 satellite 2.Characterization of the T2L2 flight instrument 3.Error budget for the T2L2 time transfer scheme 4.Conclusion & Status End of Part II

Calern, September 23, 2008 Patrick Vrancken – Characterization of T2L2 & Micrometric Laser Ranging page 41 Part I: Micrometric Laser Ranging for ILIADE Part II: Characterization of T2L2 (Time Transfer by Laser Link) on the Jason 2 ocean altimetry satellite Patrick Vrancken Thesis Presentation - End