T2L2 and beyond next generation time transfer schemes

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Letitia Underwood
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1 T2L2 and beyond next generation time transfer schemes Etienne Samain Patrick Vrancken Optical Clocks Workshop for ESA Cosmic Vision, Uni Düsseldorf, March 9, 2007 Toulouse, 13 avril 2006 Patrick Vrancken Banc de Test Métrologique 1

2 Agenda 1. Overview T2L2 2. Upgraded version (T2L2) 2 3. post-t2l2: next generation optical time transfer 4. Other 5. Résumé Toulouse, 13 avril 2006 Patrick Vrancken Banc de Test Métrologique 2

Time Transfer by Laser Link (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

3 Time Transfer by Laser Link (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 : X A = t s + t 2 r t b + τ Relativity + τ Atmosphere + τ Instrument Toulouse, 13 avril 2006 Patrick Vrancken Banc de Test Métrologique 3

(Electronics) Orbit Altitude 1336 km, i = 66, P = 6800 s Max distance in common view: 6500 km Single pass: ~1000s

4 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 T2L2 (Optics) T2L2 (Electronics) 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 Toulouse, 13 avril 2006 Patrick Vrancken Banc de Test Métrologique 4

5 T2L2 Space Instrument Synoptic Allocations Masse : 8.0 kg (Elec.) kg (Optic) Power : 40 W Volume : 270x280x150 mm 3 (Elec.) and 160x116x102 mm 3 (Optic - Ø 30x100 & Ø62x100) Toulouse, 13 avril 2006 Patrick Vrancken Banc de Test Métrologique 5

T2L2 Ground Segment: Laser Station Laser station: pulsed laser (mostly doubled Nd:YAG/YO 4, 532nm, pulsewidth 20 to 300ps, 10Hz to 1kHz reprate) Event timer with associated clock

6 T2L2 Ground Segment: Laser Station Laser station: pulsed laser (mostly doubled Nd:YAG/YO 4, 532nm, pulsewidth 20 to 300ps, 10Hz to 1kHz reprate) Event timer with associated clock (Cs, Rubidium+GPS, H-Maser) Laser pulse transmission detector for Tx date Laser pulse receive detector for Rx date: Toulouse, 13 avril 2006 Patrick Vrancken Banc de Test Métrologique 6

Laser Station MeO and FTLRS MeO rejuvenated Laser Lune : faster and more

operational laser ranging dedicated labs/space for experiments (w/ access

Transportable Laser Ranging Station world s first and smallest mobile

7 Laser Station MeO and FTLRS MeO rejuvenated Laser Lune : faster and more precise telescope motorization ameliorated laser system dedicated lab for operational laser ranging dedicated labs/space for experiments (w/ access to telescope) ready in summer 2008 MéO, Grasse FTLRS: French Transportable Laser Ranging Station world s first and smallest mobile laser ranging station Toulouse, 13 avril 2006 Patrick Vrancken Banc de Test Métrologique 7

8 Ground Segment - Network Participating stations in the ILRS network: sufficient equipment: event timer & clock Toulouse, 13 avril 2006 Patrick Vrancken Banc de Test Métrologique 8

9 T2L2 expected performance Ground to satellite time transfer time stability: pour τ 0 = 0.1 s E-01 1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06 1.E+07 Toulouse, 13 avril 2006 Patrick Vrancken Banc de Test Métrologique 9

10 T2L2 expected performance - 2 Ground to ground time transfer time stability common view: two laser stations A and B firing simultaneously towards T2L2: Non Common View σ x (τ) (ps) Onboard clock limitation (DORIS USO) non-common view: consecutive passes over two ground Possibility stations to A calibrate and BRF links (with dead time τ AB ): for τ > 1 day Common View Stability: < s < 10 1 day Accuracy: < 100 ps Cold atoms clocks from > 1000 s Cold Atoms Clock Ground to Ground Transfer (Common view) Ground to Ground Transfer (Non Common view - 300s) Ground to Ground Transfer (Non Common view s) Ground to Ground Transfer (Non Common view s) TWSTFT GPS - Carrier Phase τ (s) Toulouse, 13 avril 2006 Patrick Vrancken Banc de Test Métrologique 10

room at CNES, Toulouse April to June 07: Integration into satellite June 07: Performance

11 Status July 2006: Tests on the Engineering Model Nov 06 to Feb 07: Qualification tests Delivery of flight model March/April 07: Calibration and performance tests with dedicated test bench in clean room at CNES, Toulouse April to June 07: Integration into satellite June 07: Performance verification tests Launch scheduled for mid-2008 Toulouse, 13 avril 2006 Patrick Vrancken Banc de Test Métrologique 11

detection equivalent point of reflection better spectral filter possible improvements on: detector: higher bandwidth

12 Improvements for a (T2L2) 2 what we would first improve on T2L2 (space instrument): of course. the clock! (but that doesn t matter here) Retro-reflector: Mono-Corner-Cube instead of pyramid of CCs: Geometry: Equivalent point of detection equivalent point of reflection better spectral filter possible improvements on: detector: higher bandwidth timer: higher resolution (vernier at higher frequencies), shorter dead time Toulouse, 13 avril 2006 Patrick Vrancken Banc de Test Métrologique 12

Improvements for a (T2L2) 2 cont d and what we would further do (on the laser) if we had some extra : Higher repetition rate faster acquisition Two color telemetry: lower white noise on measured

13 Improvements for a (T2L2) 2 cont d and what we would further do (on the laser) if we had some extra : Higher repetition rate faster acquisition Two color telemetry: lower white noise on measured distance shorter pulse width higher precision drawback: below ~20 ps the pulses will suffer atmospheric dispersion need for atmospheric pre-compensation by negative-chirp control in order to arrive chirp-free (i.e. transform limited) on T2L2 detector Toulouse, 13 avril 2006 Patrick Vrancken Banc de Test Métrologique 13

14 Future: Laser station w/ f-comb Replacement of Nd:YAG by high-power femto-second laser Dispersion control short pulses implicate large spectral bandwidth Æ magnification of receiving noise when adapting spectral filters to pulse BW Æ SNR take advantage of frequency combs: Toulouse, 13 avril 2006 Patrick Vrancken Banc de Test Métrologique 14

15 Other Transponders (see talk Ulrich Schreiber) One-way telemetry: TIPO: Differential time/distance measurement based on the exactitude & stability of an embarked clock Based on the timing of laser pulses in different temporal reference frames: transmitting laser stations receiver on satellite Issued from classical lunar/satellite laser ranging but with link budget ~ d² LLR/SLR max distance: Moon One-way max distance: Solar system Linear Photo- Detection Spectral Filter Laser pulse Telemetry Coarse Timing (FPGA) Res = 100 ns Calculator Clock Temporal Filter (x pseudo random code) Fine Timing (Vernier) Res = 10 ps Toulouse, 13 avril 2006 Patrick Vrancken Banc de Test Métrologique 15 Frequency Synthesis

16 pour résumer Advantages of optical link (like in T2L2): mono-carrier two-way scheme optical carrier permits very high frequency modulation geometry of optical systems allows for very precise spatial reference points not sensitive to ionosphere T2L2 will be available in 2008 is already able to read cold atom clocks is easily upgradeable Toulouse, 13 avril 2006 Patrick Vrancken Banc de Test Métrologique 16

T2L2 ON JASON-2: FIRST EVALUATION OF THE FLYING MODEL

T2L2 ON JASON-2: FIRST EVALUATION OF THE FLYING MODEL Ph. Guillemot, I. Petitbon Microwave & Time-Frequency Department CNES French Space Agency Toulouse, France E. Samain, P. Vrancken, J. Weick, D. Albanese,