satellite system optis – a platform for precision experiments hansjörg dittus, c.lämmerzahl, s....
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Satellite system OPTIS – A platform for precision experiments
Hansjörg Dittus, C.Lämmerzahl, S. Scheithauer ZARM, University of Bremen, Germany,
Achim Peters,
Humboldt University , Berlin, Germany
Stephan Schiller, Andreas Wicht Institute of Experimental Physics, Heinrich-Heine- University, Düsseldorf, Germany
OPTIS
ASTROD-Symp, Beijing, 14.7.2006
OPTISMotivation
Iso trop y o f c In d epen den ce o f c fromve lo c ity o f labo ra to ry
Tim e d ila tion
Special R elativity
Test of SR implies • Probing the structure of space-time• Test of Maxwell equations• Test of quantum gravity theories: Prediction of modified
Maxwell equations
W eak E qu iva len ceP rinc ip le
U n iversa lity ofG ravita tio na l R ed S h ift
S p ec ia l R e la tivity
G eneral R elativ ity G ravito m agn etice ffec ts
OPTISSTEP, MICROSCOPE
Test of GR implies• Test of quantum gravity theories• Tests of predicted violation of Weak Equivalence Principle• Tests of predicted violation of Universality of Gravitational Red Shift
ASTROD-Symp, Beijing, 14.7.2006
OPTISScientific objectives
Isotropy of light propagation
Independence of velocity of light from velocity of laboratory
Universality of Gravitational Redshift
- comparison of clocks:
optical resonator – atomic clock – optical clock
Test of Lense-Thirring effect
Absolute gravitational redshift
Doppler effect
Perigee advance
Newtonian potential (Yukawa-like terms)
OPTIS: Improved Optical Tests for the Isotropy of Space
Improved experimental tests of:
ASTROD-Symp, Beijing, 14.7.2006
OPTISExperimental goals
TestPresent Accuracy
OPTIS goal
Michelson- Morley1,5 · 10-9 10-12
Kennedy-Thorndike7 · 10-7 10-8
Time dilation / Doppler effect2 · 10-7 10-9
Universality Gravitational redshift 1cavity – clock comparison 1,7 · 10-2 10-4
Universality Gravitational redshift 2clock-clock comparison 2,5 · 10-5 10-7
Lense-Thirring effectvia laser tracking 3 · 10-1 10-8
Absolute gravitational redshifttime transfer 1,4 · 10--4 10-3
Perigee advancevia laser tracking 3 · 10--3 10-4
Newton potentialvia laser tracking 1 · 10-5 10-12
ASTROD-Symp, Beijing, 14.7.2006
OPTIS
Mission Outline 1 (Baseline scenario)
to sunapogee 40000 km
perigee 10000 kmlaser
cavityfrequencycomparison
frequencycomparison
atomicclock(s)
frequencycomb
• Michelson-Morleylaser
cavityfrequencycomparison
• Univ. grav. red-shift
1( )U x
2( )U x
laser
cavity
frequencycomparison
atomicclock(s)
frequencycomb
• Kennedy-Thorndike
1
2
ASTROD-Symp, Beijing, 14.7.2006
ASTROD-Symp, Beijing, 14.7.2006
OPTISMission Outline 2
Lense-Thirring effect (orbit precession) Perigee shift Test of Yukawa part in Newtonian potential
High precision tracking by laser rangingin combination with drag free AOCS
ASTROD-Symp, Beijing, 14.7.2006
OPTISMission main characteristics
Space conditions:
Long integration time Large velocity changes Large potential differences
Noise reduction:
Drag-free AOCS ( < 10-13 m/s2 @ 10-2 Hz)First time: combination of drag-free AOCS and laser rangingMonolithic resonatorSystematic elimination of distortions
New technologies in space:
Ultrastable lasersOptical frequency combResonators with narrow linewidthMicro-Propulsion systems (e.g. FEEPs, Colloidal thruster)Laser Link PlatformUltrastable atomic clocks
ASTROD-Symp, Beijing, 14.7.2006
OPTISBasic principle to measure the isotropy of c
Usual 2nd-order approximation:
2
20
2
20
2
0 sinA1c
vB
c
vc,vc
ASTROD-Symp, Beijing, 14.7.2006
OPTISMichelson-Morley (MM) experiment
Phase shift measurement
Brillet and Hall (1976)
Best measurement on Earth:
9105 B
laser
cavityfrequencycomparison
220
2
00
cos211
2Δ
c
vB
c
cc
f
ff
ASTROD-Symp, Beijing, 14.7.2006
OPTISKennedey-Thorndike (KT) experiment
v
v
v
v
v0
vc
vA
f
f 202
Frequency change measurement:
Braxmaier, Müller, Pradl, Mlynek,Peters, and Schiller (2002)
Best measurement on Earth:
5101291 ..A
laser
cavity
frequencycomparison
atomicclock(s)
frequencycomb
ASTROD-Symp, Beijing, 14.7.2006
OPTISTest of Universality of Gravitational Red Shift (2)
U1(r)
U2(r)
2
Δ
c
U
f
f
f
f
atomclockcavity
atomclock
atomclock
cavity
cavity
Frequency difference measurement:
Best measurements:
51012Δ .2102Δ
for H-maser Cs-clock
Cs-clockfor cavity
Bauch and Weyers (2002))
Turneaure and Stein (1987)
Signal signature of Red Shift violation differs from that of SRT violation due to velocity indepence !!!
laser
cavity
frequencycomparison
atomicclock(s)
frequencycomb
ASTROD-Symp, Beijing, 14.7.2006
OPTISEffects measured by precise tracking
Lense-Thirring effect:Precession rates of knots
23
23223
232 1
6
1
2Ω
eac
)i(Jω,
eac
J
cosG
G
Perigee shift
223 122
eac
M
a
Mβγαω EE
GG
Test of the Newtonian potential
λ/rαr
MrU e
G1
ASTROD-Symp, Beijing, 14.7.2006
OPTISMission Requirements
Variable spin rates(elimination of systematic errors) TSpin = 100 to 1,000 s
Cavity length variation requirement:δc/c < 10-18 σΔL (TSpin) / L < 10-18
Laser frequency lock instability: δc/c < 10-18 σlock(TSpin) / f < 10-18
Temperature stability for cavities: ΔTrandom < 200 µK,
ΔT (7 h) < 10 µK Independent clock reference for KT- experiment
reason for Gravitational Red shift experiment Comb generator must be used for comparison between atomic clock and cavity
δf/f < 10-15
Residual acceleration on board spacecraft δa < 10-13 m/s2 @ 10-2 Hz
Laser ranging δr < 1mm
ASTROD-Symp, Beijing, 14.7.2006
OPTISKey technology: Optical cavity
single cavity: fused silica•Cavities: length ~ 5 cm (finesse ~ 100,000); effective length ~ 5000 m; better than interferometers: ~ 10 m
•Material: fused silica
• Length stability:ΔL = 10-16 m
• Temperature stability: ΔT < 10-8 K / √Hz but: for MM common mode rejection due to monolithic design: ΔT < 10-6 K / √Hz
•Residual accelerations
•Gravity gradient:10-13 m/(s2 · Hz)
ASTROD-Symp, Beijing, 14.7.2006
OPTISResonator model
01
21
1
Urr
Elastic deformations under tidal forces
analytical solution by S. Scheithauer and C. Lämmerzahl
r Δr/R z Δz/L
R 6.2 · 10-15 L 1.6 · 10-13
R 6.5 · 10-14 0 0
Displacements for a 7000 km orbit
ASTROD-Symp, Beijing, 14.7.2006
OPTISOPTIS resonator (FEM analysis)
calculated for a 7,000 km orbit
ASTROD-Symp, Beijing, 14.7.2006
OPTISMirror displacements during orbit
relative displacement between 2 opposing mirrors
displacements at mirror midpoints
ASTROD-Symp, Beijing, 14.7.2006
OPTISResonators and spin
Relative mirror displacements dx on x-axisOrbital rotation around y-axisSpin around z-axis
ASTROD-Symp, Beijing, 14.7.2006
OPTISThermal gradients
Thermal gradient along z- axis: 10-9 K/L
ASTROD-Symp, Beijing, 14.7.2006
OPTISKey technology: Lasers and electronicsLasers: langth, energy levels -> frequency
Diode-pumped Nd:YAG laser (1064 nm)
-Narrow linewidth
-High intensity stability
-High frequency stability
Ultrastable frequency lock on long time scales to cavities (Ruoso et al 1997, Braxmaier et al. 2002)
Also used for Earth-based GW interferometers
Lasers already space-qualified (Bosch)
Will be used for LISA-Pathfinder
RAV: 3·10-15 @ 100 s
10-5 of cavity linewidth
ASTROD-Symp, Beijing, 14.7.2006
OPTISClocks
Frequency [GHz] Stability Operation in space
H-maser 1.420 405 751 10-15 GP-A, ACES, PHARAO, Galileo
Ion clock 40.507 347 996 5 . 10-16 GPS, SPACETIME
Cs atomic clock 9.192 613 770 10-13
Rb atomic clock 6.834 682 613 10-12 GPS, Galileo
Allan variance
Integration timeOPTIS requirement
ASTROD-Symp, Beijing, 14.7.2006
OPTISKey technology: Frequency comb
( )t
Purpose: comparison of atomic clock frequency: 1010 Hz with optical frequency: 1015 Hz Accuracy: 10-15 Hz
1010 Hz1510 Hz
1510
ASTROD-Symp, Beijing, 14.7.2006
OPTIS
Spacecraft and orbit (baseline scenario)
Mass 250 kgMass 250 kg
Power 250 WPower 250 W
High elliptic orbitPeriod: 14 hInclination 63°Shadow:
5 months without shadow 1 month with periodsSun rad. press. 4.4 μN/m2
Earth albedo rad. press. 1.2 μN/m2
Laser ranging platform
GTO
HEO
Apogee motorfor orbit transfer
FEEPs (???):ΔF = ± 0.1 μNFmax = 100 μN
+ Reference sensor δa=10-14 m/(s2·√ Hz)
In(Cs) Reservoir
ONERA
Cold gas thrusterfor coarse attitude control
ASTROD-Symp, Beijing, 14.7.2006
OPTISOPTIS Summary
• Improved tests of isotropy and velocity-independence of c, universality of red shift, and gravitomagnetic tests
up to 1,000 times more accurate
Use of state-of-the-art technology
Ultrastable optical cavities Lasers Optical frequency comb Electronics and stabilization Micro-propulsion system Laser ranging High precision atomic clocks
• Optimal use of space conditions
Drag-free satellite control Long integration time High velocity Large gravitational potential changes
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