Satellite-based tests of Special and General Relativity

Transcription

1 OPTIS Satellite-based tests of Special and General Relativity S. Schiller and the OPTIS Team HYPER Symposium Paris, Nov. 4-6, 2002

2 The OPTIS team OPTIS Heinrich-Heine- ZARM, Univ. Bremen Universität Düsseldorf Humboldt-Univ. Berlin (formerly Konstanz) P. Antonini H. Dittus H. Müller C. Lämmerzahl S. Theil S. Herrmann S. Schiller S. Winkler A. Peters Sponsored by 2/20

3 Contents Scope of the current study Work in progress Laser stabilization Atomic clock - cavity comparison Satellite thermal analysis Future work Terrestrial Michelson-Morley-Test

4 Experimental payload Cavities Cavity-cavity frequency comparison Frequency comparison with atomic cloc Frequency comb Lasers atomic clock

5 Technologies Required techniques are also to be used in scheduled and planned fundamental physics and astrophysics missions Technique Lasers, optics Optical cavities Thermal stabilization Frequency comb Atomic clocks FEEPs Inertial sensor Drag-free Required for OPTIS Ongoing developments SMART-2, Bosch, Astrium, Hannover, HYPER SMART-2, HYPER ASI Obs. Neuchatel, JPL Seibersdorf research MICROSCOPE, SMART-2 MICROSCOPE, ZARM

6 Feasibility study asks of the first feasiblity study ( mid until end ) Lock error analysis and elimination strategies Digital laser-to-cavity lock system development Demonstrate measurement of optical cavity frequency with respect to atomic clock Orbit analysis Basic thermal modeling

7 Laser lock to cavity

8 Short-term stability Allan Variance of Beat between 2 cavitie Two independent cavities No drift removed RelativeRoot Allan Variance lative Root Allan Variance f Lock relative to cavity: Averaging time [s]

9 Long-term stability: Reduction of Lock errors FM detection at f vs. 3 f (f = 0.6 MHz) Reduces Lock errors due to residual amplitude modulation Detection at f 100 Hz Detection at 3 f 20 Hz

10 0 Frequency of carrier or sideband relative to cavity TIS Active Offset Compensation - Principle Reduces Lock errors due to electronic offsets, etalons Lock of carrier to resonance 0 Error signal Small lock point shift Lock of sideband to resonance 0 Large lock point shift

11 Active Offset Compensation - Results Active compensation of lock errors by locking a laser sideband to the cavity every 15 s with compensation Relative Root Allan Varian Between two cavities: 5. τ = 14 h without compensation

12 Digital Lock Electronics Digital error signal generation (14 bit 10 Msamples/s) Effective maximum modulation frequency: 2 MHz Digital feedback signal generation Fast feedback channel: 14 bit 10 Msamples/s Slow feedback channel: 16 bit 100 ksamples/s Operation demonstrated in dry run

13 Cavities & Lasers Using fused silica and sapphire cavities; ULE later Reducing size of optics hardware Fiber coupling of laser to cavity Using standard diode-laser pumped Nd:YAG lasers Space-qualified Nd:YAG lasers exist and are suitable

14 The optical frequency comb Development of a frequency comb Installed H - Maser

15 Thermal modeling of satellite Heat inputs: sun & earth (vary along orbit) satellite bus (170 W) experimental payload (90 W) Simplest model: payload is shielded by a number of superinsulation layers Software used: ESATAN, ESARAD Solar panel Satellite bus components 90 cm Experimental payload compartment (shown closed)

16 Results Hot solar cell surface (120 deg C), cold backside (-100 deg C) cylinder surface has time-varying temperature 4 superinsulation shields lower payload temperature to ~ 50 deg C temperature variation during orbit: 1.2 K Obtain reasonable shield mass and emissivity Temperature change during orbit [K] Satellite bus components

17 Planned work Goal: laboratory demonstrator Compact optical system Thermally stabilized crossed cavities Laser, Maser, Frequency comb and electronics: conventional Fabrication of resonators Materials: ULE, Silicon High finesse mirrors Monolithic double-cavity Laser system with appropriate specifications Power stability Phase modulation Amplitude modulation

18 Planned work Continue thermal modeling Characterize components and their interdependence Set up end-to-end-simulation system

19 Michelson-Morely Test using cryogenic resonators H. Müller et al. (Univ. Konstanz)

20 Michelson-Morely Test using cryogenic resonators H. Müller et al. (Univ. Konstanz) c(θ,v) v

21 Michelson-Morely Test using cryogenic resonators H. Müller et al. (Univ. Konstanz) c(θ,v) v c c = A v 2 c 2 + B v 2 c 2 sin2 θ

22 Setup Comparison of two cavities sensitivity doubled Uses earth rotation, violation signal: 12 h period Temperature sensitivity of beat: /K Beam alignmen control

23 Data analysis: Example Hz 0692 t D t D t D t D Sin Frequency deviation [Hz] -150 D z n o i t a-170 i v e d y-180 c n e u q e-190 r f Dec. 5, 2001 Fit with model; violation amplitude 3.5 ± 2.5 Hz days after 82002, 1, 1, 0, 0, 0< Time [days after Jan. 1, 2002]

24 Results Amplitude: ( -0.6 ± 0.5 ) Hz B = (-1.4 ± 1.3). 10-9

25 Interpretation of MM - test within dynamical test theory Lorentz & CPT-violating extension of Standard Model: Colladay & Kostelecky (1999) electromagnetic Lagrangian: L = 1 4 F F µν µν 1 ( 4 k ) F µνρσ F µν F ρσ 19 parameters; astrophysical observations set stringent limits to 10 parameters MM-experiments can access remaining 9 parameters; in our experiment: 7, due to orientation of cavities (κ e- ) xy = (2.3 ± 1.1) (κ e- ) xx - (κ e- ) yy = (3.7 ± 2.4) (κ e- ) yz = (-1.8 ± 2.4) (κ e- ) xz = (-1.2 ± 1.9) (κ o+ ) yz = (-0.07 ± 1.1) (κ o+ ) xz = (-2.6 ± 2.3) (κ o+ ) xy = (-2.9 ± 3.6)

26 Summary Feasibility studies for OPTIS mission: hardware and modeling Lock stability meets OPTIS specifications; digital lock electronics developed and ready for testing Cavity to maser frequency comparison under construction Completed basic satellite thermal modeling Review panel has recently recommended continued support with high priority Terrestrial Michelson-Morley Test: 3 -fold improvement of upper limit for a possible anisotropy of light propagation Determined 7 new coeffcients of dynamical test theory