probing gravity in neo with high-accuracy laser-ranged test masses · 2006. 9. 1. · probing...

Probing gravity in NEO with high-accuracylaser-ranged test masses

Simone Dell’Agnello, INFN-LNF, ITALYLaboratori Nazionali di Frascati (Rome) of INFN

for the LARES Collaboration (I. Ciufolini PI)

NASA Workshop “From Quantum to Cosmos: Fundamental Physics Research in Space”Warrenton, Virginia, May 2006

LAGEOS array

LARES 1:2 proto

Q2C: Fundamental Physics Research in Space, May 06 S. Dell’Agnello, INFN-LNF2

Outline

• Probing gravity in NEO with LAGEOS

• The new LARES mission and thermal NGPs

• The LNF Space climatic facility to test LAGEOSand LARES prototypes

• New collaborations– Climatic and optical test of retro-reflector arrays for

GNSS togeher with ILRS

– Design and test of laser-ranged test-masses for theDeep Space Gravity Probe (DSGP) mission

Probing gravity in NEO:measurement of frame-dragging w/LAGEOS

• Raw observed noderesiduals combined

• Raw residuals withsix periodic signalsremoved, estimatedrate is 47.9 mas/yr

• GR-predictedresiduals, rate:48.2 mas/yr

•• Raw observed nodeRaw observed noderesiduals combinedresiduals combined

•• Raw residuals withRaw residuals withsix periodic signalssix periodic signalsremoved, estimatedremoved, estimatedrate is 47.9 rate is 47.9 masmas/yr/yr

•• GR-predictedGR-predictedresiduals, rate:residuals, rate:48.2 48.2 masmas/yr/yr

Earth rotation J drags space-time around itThe node of LAGEOS satellites (a~12300 Km)is dragged by ~2 m/yr

Oct. 2004

EIGEN-GRACE02S 2004 data by GFZ1993-2003 LAGEOS I and LAGEOS II data

I.Ciufolini, E. C. Pavlis

2/3232 )1(

2

eac

GJTL

−=Ω −&

I. Ciufolini, SpacePart, Beijing, April 06

(stochastics errors, like seasonal variations ofEarth grav. field, observation biases-range/spin)

Thistalk

LAGEOS contribution to Space GeodesyInternational TerrestrialReference Frame (ITRF)

• Geocenter and Scale- few mm accuracy

• Axis orientation- VLBI + LAGEOS (changes)


The new LARES mission

• Proposed to INFN at the end of 2004– LNF-Frascati and Aerospace Eng.- Rome La Sapienza will

build and test LARES at LNF– Satellite cost, to be funded by INFN, ~ 1 Million €

• Main physics goals– Frame dragging (Lense-Thirring effect) with ≤ 1% accuracy

– Test very-weak field limit of GR (1/r2 law) and new longrange interactions (Yukawa-like potential)

• × 103 improvement on α in the λ ~ 10000 Km range

– PPN parameters β, γ with 10-3 accuracy, or better (bymeasurement of the GR perigee precession with 10-3

accuracy)

€

Vyuk = −αGMearth

re−rλ

Test of the very-weak field limit of GR (1/r2 law) and of new long range interactions (ie Yukawa-like potential Vyuk)

α

λ(m)

10-12

107


New physics with perigee precession ?

• Test theory based on a BRANE-WORLD model, whichcan explain DARK ENERGY and SN acceleration– Dvali at al, PR D 68, 024012 (2003)– Anomalous perigee precession– Lunar ranging: δφ = 1.4 x 10-12/orbit predicted

σφ = 2.4 x 10-12 present accuracy (10-fold improvement expected w/APOLLO)

– BUT: δφ = 1.9 x 10-11 rad/yr, same for Moon and LAGEOS

• For SLR this would require a very high altitude, largeeccentricity, i = 63.4o (Molnya value), much largermass. A much more expensive mission than LARESand a further improvement on controlling NGPs


LARES baseline design and tests• LAGEOS: ∅ = 60 cm, m ~ 400 Kg, 426 CCRs• LARES: ∅ = 30 cm, 100 Kg, 102 CCRs (size scaling)• Area/Mass ≤ than LAGEOS, for Non Gravitational Perturbations• Full thermal characterization, NEVER done for LAGEOS

– CCR thermal relaxation time, τCCR

– Solar and IR emissivity and reflectivity of CCRs and Al– Evaluation of thermal forces (simulation, IR camera)

• Removal of Al retainer rings responsible of ~1/3 of thermal forces• Optical characterization in space climate

LAGEOS I, ‘76LAGEOS II, ‘92


The LAGEOS CCR array

Picture in the Visible

Picture in the InfraRed


A Space Climatic Facility at LNF• Characterization of LAGEOS and LARES prototypes in realistic space

conditions– Great help by Doug Currie (UMCP) in the design of the SCF

• Asymmetric thermal forces by CCRs are the largest NGPs on Lense-Thirring (~2 %)– Effect driven by slow CCR thermal relaxation time, τCCR, never

measured in space conditions– TECLIPSE ≤ 4300 sec, τCCR ~ 2000-7000 sec, TORBIT = 13300 sec

• Measurement of τCCR mandatory for the success of LARES

•• Characterization of LAGEOS and LARES prototypes in realistic spaceCharacterization of LAGEOS and LARES prototypes in realistic spaceconditionsconditions–– Great help by Great help by Doug CurrieDoug Currie (UMCP) in the design of the SCF (UMCP) in the design of the SCF

•• Asymmetric thermal forces by Asymmetric thermal forces by CCRs CCRs are theare the largest largest NGPs NGPs on on Lense-Lense-Thirring Thirring (~2 %)(~2 %)–– Effect driven by slow CCR thermal relaxation time, Effect driven by slow CCR thermal relaxation time, ττCCRCCR, , nevernever

measuredmeasured in space conditions in space conditions–– TTECLIPSEECLIPSE ≤≤ 4300 sec, 4300 sec, ττCCRCCR ~ 2000-7000 sec, T~ 2000-7000 sec, TORBITORBIT = 13300 sec = 13300 sec

•• Measurement of Measurement of ττCCRCCR mandatory for the success of LARESmandatory for the success of LARES

Earth InfraredYarkovskyeffect.Drag firstunderstood byDave Rubincam(NASA-GSFC)

IR

Solar Yarkovsky effect

SUN


Testing the LAGEOS array at the SCF

Quartz window

IR cameraGe window

Earth IRsimulator

Thermal shield (Cu)Vac. shellService turret

Solar beamshroud

Ø = 40 cm

LAGEOSmatrix

D = 15 cm

Solar NEOsimulator

Ø = 10 cm

Ø = 30 cmT = 250 K

Alodized back inphoto


The Solar Yarkovsky effect on LAGEOS

τCCR, CCR thermalrelaxation time

Spin pointing to sun

Sunlit pole

Figures and calculationsby Victor J. Slabinski,

Cel. Mech. Dyn. Astr.vol.66, 131-179 (1997)

2/3

1/3

aMAX = 10-10 m/sec2

~ 1/10 x theanomalous PIONEER

deceleration


Effects of thermal forces on node and perigee

• The node long-term drift– Calculations of τCCR vary from 2000 sec to 7000 sec, 250%.

This implies a 2 % error on frame-dragging (I. Ciufolini)– Our goal: measure τCCR with ≤ 10% accuracy. This will give a

0.08 % error on frame dragging ==> negligible !

• The perigee long-term drift– Measuring β and γ to 0.1% requires an accuracy on the

perigee rate of 3 mas/yr. The 250% uncertainty on τCCRgives a 19 mas/yr error on the perigee rate (I. Ciufolini)

– Our goal: measure τCCR with ≤ 10% accuracy. This will give a0.76 mas/yr error on the perigee rate ==> OK


τCCR: results from full thermal simulation

Goal: measure τCCR at ≤10%accuracy. With a 0.5 Kaccuracy on temperature thisis well within statistical reach SUN=on, IR=off

τCCR = 2400 ± 40 sec (2% error)σ(T) = 0.5 K

T(K)

t(sec)

T = 278 K

T = 276 K

FEMmodel250 nodes


Thermal simulation results on τCCR

τCCR ∝ 1/T3

Different Sun andIR conditions,incidence angleand temperatureof the Al satellitebody

TAl=280 KSun ONIR OFF

TAl=280 KSun ONIR ON

TAl=300 KSun OFFIR ON

TAl=300 KSun ONIR OFF45 deg


TAl=300 KSun OFFIR ON

TAl=300 KSun ONIR ON



Preliminary measurement with IR camera

• Indoor, in-air test at roomtemperature to measure εIR(x) andρIR(x), where x = Al or CCR

• Qcamera = Qemission + Qreflected• T4

camera= εIR T4x + ρIR T4

bkg• εIR(x) + ρIR(x) = 1• Tx w/thermocouple• Tbkg: black disk with controlled

temperature = 10 oC or 50oC

εIR(CCR) ~ 0.82ρIR(CCR) ~ 0.18εIR(Al) ~ 0.15ρIR(Al) ~ 0.85

NEXT: outdoors, solar ε(x) and ρ(x)

IR pictures of the LAGEOS array

Ø = 10 cm

LAGEOS array

Black diskAt 10 or 50 oC


Thermal model to be tuned to SCF dataDifferent cases for suprasil optical properties

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Slabinsky Center

Case a Corner

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Case a&e Center

αSOLAR= 0.15εIR = 0.81

αSOLAR= 0.015, εIR = 0.81

αSOLAR= 0.015, εIR = 0.20

Different suprasil (CCR) thermo-optical properties

Time (sec)

Tem

pera

ture

(K)


Beyond the baseline LARES mechanical design

• Outer shell halves. CCRs back-mounted, ie no retainer rings• Baseline: recreate the LAGEOS internal geometry and closed

CCR cavities• Beyond the baseline: “shell over the core” design

– CCRs in radiative contact in a vacuum gap– Expect better CCR T uniformity and smaller thermal forces


FE model and thermal simulation of LARES

295.6 K

295.3 K

287 K

263 K

15000 nodes. Still being optimized and fully debugged

Steady steady with LARES in front of a solar lamp CCRs, front view Core, side view


Testing LARES at the SCF

Quartz window

IR cameraGe window

Earth IRsimulator

(Z306 paint)


Solar beamshroud

Ø = 40 cm

LARES proto

Ø = 30 cm

Solar NEOsimulator

Ø = 10 cm

Ø = 30 cmT = 250 K

Alodized back inphoto


Status of the SCF• All equipment delivered except

Solar simulator• Solar simulator acceptance test

at TS-Space (UK) done May 29• Now: outgassing, TL installation

VIS

BEAMSPLITTER

6kW METALHALIDE LAMP

10kW QUARTZHALOGEN LAMP

RADIATION LOSS~ 10%

UV

IR SUNAM0 SPECTRUM1366.1 W/m2

The Sun Simulator QH: uniformity±3%

HMI: uniformity±3%

Measured !

300 ÷ 2400 nm

Wavelength (nm)

Rela

tive

Inte

nsity

Our spectrum will be an AMO standard from400 nm to 3500 nm

Each lamp is calibrated with a Solarimeter(accurate and stable over ten years to 1%)

HV adjusted to compensate for lamp ageingwith feedback PIN diode


LARES prototype built at LNF

LARES new design1:2 scale proto

InfraRed image


Expected optical performance of baseline LARES

Simulation by Dave Arnold(LAGEOS optical designer)

LAGEOS has ~4 times as many cubes:ranging better by ~ 2.

LARES is about half the size:range variations smaller by ~ 2 if therewere the same number of cubes.

Since LARES has fewer cubes the twoeffects cancel each other so that thevariation in the range correction isabout the same as LAGEOS

LAGEOS range correction~ ∅/2

0.250

0.248

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Rang

e co

rrec

tion

(m)

350300250200150100500Rotation angle (deg)

The top curve (green) in each plot is the half-max range correction.The bottom curve (red) is the centroid range correction.

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e co

rrec

tion

(met

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350300250200150100500Rotation angle (deg)

laser “viewing” equator

laser “viewing” pole

RA

NGE

CO

RREC

TIO

N (

m)

ROTATION ANGLE (deg)


Beyond the baseline LARES optical design

• LAGEOS-geometry, BUT no dihedral angle offset andhalf the size– Sinergism with the DSGP mission; since d = O(Km) ==> no velocity

aberration

• Hollow CCRs (Be or Al)– Sinergism with IRLS and GSFC, because these are candidates for

GPS-3

• Russian CCRs (fused silica, smaller and metal coated)– Used by GLONASS, GPS-35, GPS-36. 3rd GPS array at UMCP (C.

Alley, D. Currie). Wil be used by the RADIOASTRON mission


Optical characterization: FFDP

Test 1: Far-Field DiffractionPattern (FFDP)

• “Optical FLAT” for absolutecross sectionmeasurement

• CCDs as laser beamprofilers

Repeat test inside the SCF

Thanks to John Degnan (σSC), DaveArnold, Jan McGarry (GSFC) for adviseand to Doug Currie (in photo) for helpon setting up the optical tests at LNF


Optical characterization: the range correction

Test 2: Ranging testCollaboration w/ILRS, GSFC, ASI-MLRO

• Laser timing unit (start time)

• Microchannel Plate Photomultiplier orStreak Camera (stop time)

• Mirror to expand the laser beam

Repeat test inside the SCF


Not just for LAGEOS/LARES …

• Laser-ranged CCR arrays and spherical test masses

• NEO : LAGEOS, LARES and arrays for GNSS constellations

• DEEP SPACE: test masses to study the Pioneer effect (DSGP)

SCFSCF SCFSCF

DSGP: SLR in deep space


DSGP laser-ranged test masses• Solar constants beyond Saturn ≤ 10-2 x NEO-AM0

– Dedicated solar simutor ?• Planet flybys for planetary science ==>planet(s) IR radiation

– Measure thermal properties in SCF at select planet distances– Tune thermal sw to data– Use orbital simular in thermal sw for the full 10-80 AU outbound

orbit• Largest LAGEOS thermal acceleration is ~ 1/10 x aPIO ! Our

high-accuracy characterization of LARES will be very useful forDSGP

• The LARES mass and thermal model will be a mass, thermal andoptical model for DSGP: for ~1 Km ranging, no need ofexpensive CCRs w/dihedral angle offsets

Testing DSGP laser-ranged masses at the SCF

Quartz window

IR cameraGe window

IR simulator forplanet encounters


Solar beamshroud

Ø = 40 cm

DSGP testmass

Deep SpaceSolar

simulator

Ø = 10 cm

Ø = ? cmT = ? K

Black Aeroglaze on one side;alodized on side shown byphoto


Conclusions• LARES will not be a mere LAGEOS III• Building upon the 30-year experience of LAGEOS, with the help

of very experienced people, we are designing a 2nd generationtest mass and an SCF to improve on the weaknesses ofLAGEOS:– New, compact design to minimize thermal forces and … €’s– Full climatic and optical pre-launch characterization

• Collaboration with ILRS to test CCR arrays for GNSSconstellations

• Proposed collaboration to design and characterization of laser-ranged test masses for the DSGP mission– Submitted to ASI for 2006-2008 study, as part of the

“Gravitational Physics” macro-packages led by I. Ciufolini

Progress on LT measurement (I.C., SpacePart06)


One example of LARES mechanical specs• Outer diameter: 320 mm• Mass: ~ 123 kg *• S/M: ~ 2.6 x 10 -3 m2/kg * (LAGEOS ~ 2.8 x 10 -3 m2/kg)• Jz/Jx: ~1.03 *• Jz: ~ 0.886 kg · m2 *• CCR mounting:

from inside• Design: “shell over the core”• Outer shelll: Al alloy (Cu alloy)• Inner core: W alloy• CCRs rings: KEL-F• Structural screws: Stainless Steel (Ergal)

* adjustable parameters

Density(kg/m3)

Al alloy 2700Cu alloy 8900W alloy 16900÷18500

Thermal Conductance(W/mK)

Al alloy 200Cu alloy 391W alloy 137


Beyond the baseline LARES optical design

• Same geometry, but no dihedral angle offset and half the size– Pro: FFDP more uniform; better systematics– Pro: x4 more CCRs; better statisticals (~x2)– Pro: CCRs less expensive– Pro: good for the DSGP mission (d = O(Km))– Con: expect τccr shorter by ~x2

• Hollow CCRs (Be or Al)– Con: no long term experience in space; structural stability under study at

GSFC;– Pro: sinergism with IRLS and GSFC, candidates for GPS-3; thermal and

optical tests at LNF SCF– Pro: overall better thermal conductivity, ie much lower TTs

• Russian CCRs (smaller, solid, metal coated)– Con: radiation absorption by coating and mounting components– Con: sinergy with ILRS, GSFC, IPIE, UMCP– Used by GLONASS, GPS-35, GPS-36. 3rd array at UMCP (C. Alley, D. Currie)

3rd INFN Workshop on Physics in Space, LNF, March ‘06


RADIOASTRON

Moon

Approved mission Launch in 2008

Earth

MILLIMETRON (approved mission)

12 m cryogenic mirror. λ = 0,01-20 mm.

Bolometric sensitivity

5*10-9 Jy (σ)(λ =0.3 mm, 1 hour int.).

Space-ALMA VLBIsensitivity 10-4 Jy (σ)

(λ =0.5 mm, 300 s int.),fringe size up tonanoarcseconds

@Lagrangian point L2


GNSS observation with laser ranging• GPS-35/36, GLONASS, GALILEO test satellites have russian CCRs• GALILEO will have 100 CCRs on each of the 30 satellites• ILRS proposed CCRs for all block-III GPS

– HOLLOW Be to save weight and space. Stability and performance to beproven in space environment

– Structural analysis by GSFC, climatic test by LNF– SLR will provide GNSS with long term absolute calibration and

stability. The best of both worlds to map the NEO space-time !

Calculations by D. Arnold, ILRS meetign at EGU, April 06, ViennaSimulations at Galileo altitude for Effective Cross Section

of 100 million sq. meters.

Design # of cubes Diam.(inch)

Approx. Areaof the cornercubes

(sq cm)

Approx Mass ofthe cornercubes

(gm)uncoated 50 1.3 428 1000

coated 400 0.5 508 460hollow 400 0.5 508 201hollow 36 1.4 356 400

Present GPS cubes 160 1.06 1008 1760

GNSS RETROREFLECTOR arraysGNSS RETROREFLECTOR arrays

GPS-35 Orbit: h = 20200 km, i = 54GPS-35 Orbit: h = 20200 km, i = 54°GPS-36 Number of GPS-36 Number of CCRCCR’’ss: 32: 32

V. Vasiliev, IPIE-Moscow; talk at FPS-06, Frascati, March 06

GALILEO TEST satellitesGALILEO TEST satellitesOrbit: h = 23200 km, i = 56Orbit: h = 23200 km, i = 56°

GIOVE-A (76 GIOVE-A (76 CCRsCCRs) GIOVE-B (67 ) GIOVE-B (67 CCRsCCRs))

The hollow CCR could also be integrated intoThe hollow CCR could also be integrated into

the LARES the LARES ““shell over the coreshell over the core”” design design

Beryllium Hollow CCR for GPS3

Courtesy of GSFC,Jan McGarry et al

probing gravity in neo with high-accuracy laser-ranged test masses · 2006. 9. 1. · probing...

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