Fundamental Physics with Space Clocks:ACES and Perspectives

FundamentalFundamental PhysicsPhysics withwith SpaceSpace ClocksClocks::ACES and PerspectivesACES and Perspectives

1997

C. Salomon , ENSDüsseldorf, Cosmic Vision Workshop on Optical Clocks, March 8th 2007

OutlineOutlineOutline

ACES status

ACES Science Objectives update: Mission in 2013-2015

Perspectives

ACES atomicclocks

• A cold atom Cesium clock in space• Fundamental physics tests• Worldwide access

ACES instrumentsACES instrumentsACES instruments

The ACES experiment consists in 2 instruments plus “tools”:

1. Pharao: Cold atom clock ⇒ Laser cooled cesium clock designed for micro-gravity

LNE-SYRTE, LKB, CNES

2. Space Hydrogen Maser – SHM ON⇒ Reference clock and local oscillator for Pharao

3. Frequency Comparison and Distribution Package – FCDP⇒ Frequency comparison and processing

4. Micro-Wave Link – MWL⇒ Link for time-frequency transfer to the ground

ACES Ground Stations (January 07)ACES ACES GroundGround Stations (Stations (JanuaryJanuary 07)07)Australia: UWA, CSIRO(Sydney) Austria: Univ. Innsbruck Brazil: Univ. Sao CarlosCanada: NRCChina: Shanghai Obs, NIM, NTSCGermany: PTB, MPQ, Univ. Hannover, Univ. Düsseldorf,

TU Muenchen, Univ. ErlangenFrance: SYRTE, CNES, Obs. Besançon, OCA, LPL Italy: INRIM, Univ. FirenzeJapan: Tokyo Univ., NMIJ, CRLRussia: Vniftri, ILS NovosibirskSwiss: METAS, ONEngland: NPLUSA: JPL, NIST, JILA, Penn St. Univ., USNOTaiwan: Telecom research labInt. Agency: BIPM

Total : 35 institutes + theory groups > 280 researchers

ACES General ViewACES General ACES General ViewView

Earth

M = 227 kg P = 450 W

ACES ON COLUMBUS EXTERNAL PLATFORM

ACES ON COLUMBUS EXTERNAL ACES ON COLUMBUS EXTERNAL PLATFORMPLATFORM

Current launch date 2013Mission duration: 18 to 36 months

ACES

Launch of European Columbus Module : end 2007- early 2008 by US shuttleACES launch by Japan HTV

Cesiumreservoir

Cooling zoneRamseyInterrogation

State detection

Selection

Microwave cavity

Ion pump3 Magnetic shields and solenoids

PHARAO cold atom clockPHARAO cold atom clockPHARAO cold atom clock

Fountain : v = 4 m/s, T = 0.5 s ∆ν = 1 Hz

• PHARAO : v = 0.05 m/s, T = 5 s ∆ν = 0.1 Hz

-300 -200 -100 0 100 200 300

0,0

0,2

0,4

0,6

0,8

1,0

Prob

abili

té

Fréquence (Hz)Frequency

PHARAO Space Clock EMPHARAO Space Clock EM

Laser source

Cesium tube

Fringe width: 5.5 Hz

Tests ongoing in CNES Toulouse

Laser SourceLaser SourceLaser Source20.054 kg, 36W, 30 liters, Vacuum and Air operation, T=10-35 deg.

Main active components:4 ECDL4 DL6 AOM30 PZT11 motors6 photodiodes8 peltier coolers

Cesium TubeCesiumCesium TubeTubeL=900 mm, M= 45 kg, P= 5 W.

captureinterrogationDetection Ramsey cavityTested in fountain

PHARAO Frequency StabilityPHARAO PHARAO FrequencyFrequency StabilityStability

σ y (τ) = 4 10 −13 τ −1/2

σ y (τ) = 2.5 10 −13 τ −1/2

With ultra-stable QuartzLimited by gravity !

With Cryo. Oscillator

Will enable 7 10-14 τ-1/2

in space

Maser Frequency StabilityMaser Maser FrequencyFrequency StabilityStabilitySHM EM Physics package +ON electronics

Frequency stabilityContributions from ON reference and

measurement system BW (=3Hz) included in spec.Stable temperature // Base plate TVC regulation switched OFF

1.00E-16

1.00E-15

1.00E-14

1.00E-13

1.00E-12

1 10 100 1000 10000

Tau [s]

Alla

n de

viat

ion

SpecACT ONACT OFF

Same result with PEM with EBB2 from Contraves

Technical assessment by ESA, December 22, 2006Feasibility demonstration of SHM is done: EM to be completed

FCDP, MWL and Payload DesignFCDP, MWL and FCDP, MWL and PayloadPayload DesignDesign

FCDPFCDP EM successfully tested in Toulouse with H- Maser, cryogenic oscillator and PHARAO 9 GHz frequency source

MicroWave Link: MWLSee W. Schaefer talkDM tests: measured noise of DLL at Ku band: 160 femtoseconds at 1 sFlight and Ground Antennas design: doneFlight antenna tests: phase distribution contributes 20% of MWL noise budget

MWL EM flight segment: March 2007

Payload design complete

A Prediction of General RelativityA A PredictionPrediction of General of General RelativityRelativity

U1U2

⎟⎠⎞

⎜⎝⎛ −

−= 212

1

2 1cUU

νν

Redshift : +4.59 10-11

With 10-16 clocksACES: 3 10-6

U2

Do fundamental physicalconstants vary with time ?Do Do fundamentalfundamental physicalphysical

constants constants varyvary withwith time ?time ?G, αelm, αstrong, me/ mp…Principle : Compare two or several clocks of

different nature as a function of time

ex:

Microwave clock/Microwave clock

rubidium and cesium

Microwave/Optical clock

Optical Clock/Optical clock

ACES

Cs, Rb, Ca, Yb+, Sr

Cs, Yb+, Yb+,

Cs, Rb, Sr, HgH, In+, Mg, Ag

Cs,Hg+

Al+, Sr,Ca, Yb

Cs, Rb, Sr+, Yb+Cs,Rb

ACES : a link between different clocks at 10-16-10-17

ACES : ACES : a a linklink betweenbetween differentdifferent clocksclocks atat 1010--1616--1010--1717

• Transition or oscillator• solid resonator: Ry /α• electronic transition: Ry

• fine structure transition: α2 Ry

• hyperfine transition: gp (me/mp) α2 Ry

With Ry = α2 mec2/2h

Femtosecond laser system for frequency comparisons

2005 Nobel prize for physics

J. HallT. Hänsch

ACES Scientific Objectivesin 2013-2015

ACES ACES ScientificScientific ObjectivesObjectivesin 2013in 2013--2015 2015

ACES selection: 1997Question: Relevance of ACES Science Objectivesduring flight in 2013-2015 ?

Evolution of scientific context:Optical ClocksOptical Frequency measurementTime transfer methods

Primary ObjectivesPrimaryPrimary ObjectivesObjectives

1) HIGH PERFORMANCE OF SPACE CLOCKS AND T&F LINK#PO1.- It is a primary objective of the ACES mission to explore and demonstrate the highperformance of a new generation of atomic clocks in the space environment and todemonstrate the ability to achieve high stability on Time and Frequency transfer.

ACES and SHM will be in 2013-15 the best clocks in spaceby one to two orders of magnitude

#PO1.1- Cold Atom PhysicsThe ACES Mission will study the cooling and manipulation of atoms with laser lightin a microgravity environment.

PHARAO: First instrument using cold atoms and microgravity environmentPioneering activity for inertial sensors, (accelerometers, gyros, clocks, gravimeters); ICE, Quantus, ESA programs, optical clocks and interferometersTowards ultracold atoms with BEC and atom lasers #PO1.2- PHARAO Stability and AccuracyX10 better than current Rb, Cs, passive masers in GPS, GALILEO X 100 in accuracy: best clock in space but not best clock in all categoriesOptical Clocks have shown: 3 10-15 at 1second and 3 10-17 at 20 000 s

Science objectivesScience objectivesScience objectives#PO1.3- Space Hydrogen Maser short term stabilityThe ACES Mission will demonstrate that SHM frequency stability (Allan deviationσy(t)) is better than (see Figure 1):σy(t = 1 s)SHM = 1.5 10-13

σy(t = 10 s)SHM = 2.1 10-14

σy(t = 100 s)SHM = 5.1 10-15

σy(t = 1 000 s)SHM = 2.1 10-15

σy(t = 10 000 s)SHM = 1.5 10-15

Figure 1 - PHARAO and SHM Expected Performances in Allan Deviation

Optical Clocks: competitor or benefit for ACES ?

Optical Optical ClocksClocks: : competitorcompetitor or or benefitbenefit for ACES ?for ACES ?

Ground Optical Clocks will:

- Assess performance of PHARAO in space at 10-16

- Improve ACES Science Objectives (See below)

- Is it feasible to fly optical clocks in a time frame close to ACES flight ?

Many ACES technologies will be key to the next generation spaceclocks: step-wise program

Primary objectivesPrimaryPrimary objectivesobjectives

#PO1.4- Space-Ground Time and Frequency TransferThe ACES Mission will demonstrate the capability to perform phase/frequency comparison between space and ground clocks with a resolution at the level of 0.3 psover one ISS pass (300 s), 7 ps over 1 day and 23 ps over 10 days.

Ground Clock Frequency ComparisonGroundGround ClockClock FrequencyFrequency ComparisonComparison

2) GROUND CLOCK FREQUENCY COMPARISON#PO2.- It is a primary objective of the ACES Mission to demonstrate the capability tocompare ground clocks at high accuracy level on a world-wide basis.

Ø #PO2.1- Common View Ground Clock Frequency ComparisonThe ACES Mission will demonstrate the capability to compare ground clocks in common view with a resolution better than 1 ps.

Competitors: Space methodsGPSTWSTFTT2L2

Ground methods:Fiber optics links: regional

Visibility and Common ViewVisibilityVisibility and Common and Common ViewView

ACES versus GPSACES versus GPSACES versus GPS

10 2 1 03 10 4 1 05 106 10 7 1 08

1 0-19

1 0-18

1 0-17

1x1 0-16

1 0-15

1x1 0-14

FR

EQ

UE

NC

Y R

ES

OL

UT

ION AC ES M iss ion

du ration

1 yea r1 m on th

1 we ek1 da y1 orb it

Pro jec ted du ratio n o f g ro u nd clo ck co n tin u ou s o p era tio n

1 pa ss

A CE S Inte rc on t.

A CE S C om m on vie w

G P SCP

T IM E (second s)

Note: Allan Deviation

Time Transfer (2)Time Transfer (2)Time Transfer (2)

#PO2.2- Non-Common View Ground Clock Frequency ComparisonThe ACES Mission will demonstrate the capability to compare ground clocksin noncommon view with a resolution better than 10-13 x ∆t+½ for ∆t > 1000s.That is, 3 ps and 10 ps for space-ground comparisons separated by 1000 s and 10000 s respectively.

This takes full advantage of ultrastable SHM-PHARAO onboard Timescale

Recovering some global common view: GPS/GALILEO

Onboard GPS geodetic receiver brings GPSas an interesting continuous monotoringof ACES and GPS/GALILEO space clocks withperhaps 10-16 capability at one week averaging

Space-Space T&F transfer at 10-16: better GPS/GALILEO satellite trackingas well as IGS clocks monitoring. See Svehla talk

Non Common ViewNon Common Non Common ViewView

2 ps

The flight time scale accumulates only 2 ps error over 3000 si.e. half an orbital period. Excellent performance in non common view provided relativisticcorrections are known sufficiently well.

ACES versus GPSACES versus GPSACES versus GPS

10 2 1 03 10 4 1 05 106 10 7 1 08

1 0-19

1 0-18

1 0-17

1x1 0-16

1 0-15

1x1 0-14

FR

EQ

UE

NC

Y R

ES

OL

UT

ION AC ES M iss ion

du ration

1 yea r1 m on th

1 we ek1 da y1 orb it

Pro jec ted du ratio n o f g ro u nd clo ck co n tin u ou s o p era tio n

1 pa ss

A CE S Inte rc on t.

A CE S C om m on vie w

G P SCP

T IM E (second s)

Non Common View: Paris - PerthNon Common Non Common ViewView: Paris : Paris -- PerthPerth

Most distant stations: Paris-PerthBetween 1 and 2 non common views per day within less than 3000 secondsSeveral NC Views within 10 000 seconds, Overall: less than 10 ps at half day, ie 2 10-16

Fundamental Physics experimentsFundamentalFundamental PhysicsPhysics experimentsexperiments#PO3.- It is a primary objective of the ACES Mission to perform fundamental physics testswith large improvements in measurement precision.These tests concern general relativity (as the gravitational red-shift measurements and the searchfor possible time variations of fundamental physical constants) as well as special relativity(as the search for a possible anisotropy of the speed of light).

Ø #PO3.1- Gravitational Red-shift:The ACES Mission will measure the gravitational frequency red shift with a relative uncertainty of 3 10-6 (improvement by a factor 25 over Gravity Probe A).

Competitors: space missions: nothing in the pipe for 2013-15

Ground Clocks: much better clocks withreduced height differenceExample:10-18 with 3 kms (Chamonix- Aiguille duMidi) or balloon flight (40kms)

Requires knowledge of local potential at 1 cm ! Factor 10 beyond current gravimetry mappingNew field of relativistic geodesy which will be demonstrated by ACES

Chamonix

Drift of fundamental constantsDrift of Drift of fundamentalfundamental constantsconstants

#PO3.2- Drift of Fine Structure Constant

The ACES Mission will measure the possible drift of fine structure constant alpha at the level of (dα /dt) / α ~ 10-16 per year.

Current limits: 1-3 10-16/year Fortier et al., PRL 07

ACES has potential of 10-17 /year: and 3 10-18 over Mission durationImportance of Relative Time Stability of two MWL channels

Global coverageVariety of clocks: microwave and optical domain

Independent constraints on alpha, strong, and weak interaction constants

Primary Objectives (3)PrimaryPrimary Objectives (3)Objectives (3)

#PO3.3- Anisotropy of speed of light.The ACES Mission will test the validity of special relativity by detecting the possible anisotropy of light velocity at the level of δc / c < 10-10.

Factor 10 gain over 2007 state of the art, Saathof et al.,PRL 2003

Secondary Objectives have also been reviewed and maintain their interest

SHM long term caracterizationContribution to TAIGround Clock synchronization at 100 ps

SummarySummarySummary

In 2015, we should have:• Operation of a cold atom microwave clock in space at 10-16 accuracy

• Gravitational redshift at 2 10-6

• Limits on variations of fundamental constants at 10-17 /year,perhaps 3 10-18 if ground clocks are accurate at this level

• Demonstration of Relativistic Geodesy via ACES at 10 cm perhaps betterdepending on Ground clock development and ACES MWL.

• GPS/GALILEO satellites monitoring, global synchronization at 100 ps

Each of these ACES Objectives brings: Factor 10 to 100 gain over State of the Art, or with luck, a major discovery !

Join the ACES Science Team to contribute to this Science !

New Science with Optical ClocksNew Science New Science withwith Optical Optical ClocksClocksMost ACES objectives can be improved by several orders of magnitude with dedicated space clock mission

Additional Science:Shapiro delay at 10-8 in solar occultation

Relativistic geodesy at 1 cm level. Sea level, Volcano and Earthquake monitoring, oil monitoring,…..Determination of the Earth geoid and time varying potentials

Improved GPS/GALILEO navigation systemsOptical clocks have excellent short term stability:30-100ms is light travel time between satellite and receiver10-15 is equivalent to 1 fs or 0.3 micron positioning noise over 1s

Towards a new high accuracy inertial reference system in space

Space experiments with optical clocksSpaceSpace experimentsexperiments withwith opticaloptical clocksclocksAssumptions:

Clocks with stability 10-15 at 1 s and 3 10-18 at one dayChoice of ion and /or atom, ultra-stable lasers,…

Frequency comboptical to optical comparisons and connection with microwave domain

Time and Frequency transfer:Space-space optical linkupgrade of demonstrated fiber link, and T2L2

Microwave link (upgrade of ACES MWL) and optical link to ground

Relativistic equations for Time and Frequency transfer at 10-18.

Orbit determination at 1cm level

Challenges Challenges Challenges

A lot of technologies to qualify for space:Lasers, optronics, fibers, temperature, launch loads, radiations,…ACES/PHARAO technologies is availableICE, Quantus, ESA optical clocks, interferometers,LISA path finder programsCold atoms in space: step-wise approach for sensors and clocks

Cosmic Vision M or L ? Time frame 2017Cosmic Vision M or L ? Time frame 2017

What are the most fundamental questions ?Search for new physics, beyond Standard ModelA gravity explorer missionSee S. Schiller et al., A possible scenario: Three clocks, ion, atom, molecule,Optical frequency comb,microwave and optical linksGeodetic GPS receiversIn 20 000 kms GPS type drag free orbitFor a 250 kg payload (minisatellite)

More Ambitious:Can clocks contribute to Pioneer Anomaly investigation ?Clocks in solar systemEnigma and SAGAS: see coming presentations by U. Johan and P. LemondeOther ideas ?

Electronic Package (EP)

Physics Package (PP)

RF Unit

Control Unit

PS Unit

HVS Unit

Ion Pumps

MCSAMicrowave Cavity

and Shields Assembly

External Structure

HDAHydrogen Distribution

Assembly

LNA

HDO

SHM instrument: 39 kg, 68 WSHM instrument: 39 kg, 68 WSHM instrument: 39 kg, 68 W

Obs Neuchâtel

SHM: Sapphire loaded cavitySHM: SHM: Sapphire loaded cavity

Titanium cylindrical cavity

(without annular cover)

Sapphire teflonized

Integrated microwave cavity

Q factor: 2 109 since 500 days

Obs Neuchâtel