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)
Q2C: Fundamental Physics Research in Space, May 06 S. Dell’Agnello, INFN-LNF6
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
Q2C: Fundamental Physics Research in Space, May 06 S. Dell’Agnello, INFN-LNF8
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
Q2C: Fundamental Physics Research in Space, May 06 S. Dell’Agnello, INFN-LNF9
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
Q2C: Fundamental Physics Research in Space, May 06 S. Dell’Agnello, INFN-LNF10
The LAGEOS CCR array
Picture in the Visible
Picture in the InfraRed
Q2C: Fundamental Physics Research in Space, May 06 S. Dell’Agnello, INFN-LNF11
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
Q2C: Fundamental Physics Research in Space, May 06 S. Dell’Agnello, INFN-LNF12
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
Q2C: Fundamental Physics Research in Space, May 06 S. Dell’Agnello, INFN-LNF13
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
Q2C: Fundamental Physics Research in Space, May 06 S. Dell’Agnello, INFN-LNF14
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
Q2C: Fundamental Physics Research in Space, May 06 S. Dell’Agnello, INFN-LNF15
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
Q2C: Fundamental Physics Research in Space, May 06 S. Dell’Agnello, INFN-LNF16
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=320 KSun ONIR OFF
TAl=300 KSun OFFIR ON
TAl=300 KSun ONIR ON
TAl=300 KSun ONIR OFF
Q2C: Fundamental Physics Research in Space, May 06 S. Dell’Agnello, INFN-LNF17
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
Q2C: Fundamental Physics Research in Space, May 06 S. Dell’Agnello, INFN-LNF18
Thermal model to be tuned to SCF dataDifferent cases for suprasil optical properties
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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)
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pera
ture
(K)
Q2C: Fundamental Physics Research in Space, May 06 S. Dell’Agnello, INFN-LNF19
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
Q2C: Fundamental Physics Research in Space, May 06 S. Dell’Agnello, INFN-LNF20
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
Q2C: Fundamental Physics Research in Space, May 06 S. Dell’Agnello, INFN-LNF21
Testing LARES at the SCF
Quartz window
IR cameraGe window
Earth IRsimulator
(Z306 paint)
Thermal shield (Cu)Vac. shellService turret
Solar beamshroud
Ø = 40 cm
LARES proto
Ø = 30 cm
Solar NEOsimulator
Ø = 10 cm
Ø = 30 cmT = 250 K
Alodized back inphoto
Q2C: Fundamental Physics Research in Space, May 06 S. Dell’Agnello, INFN-LNF22
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
Q2C: Fundamental Physics Research in Space, May 06 S. Dell’Agnello, INFN-LNF24
LARES prototype built at LNF
LARES new design1:2 scale proto
InfraRed image
Q2C: Fundamental Physics Research in Space, May 06 S. Dell’Agnello, INFN-LNF25
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
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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.
0.250
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rrec
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laser “viewing” equator
laser “viewing” pole
RA
NGE
CO
RREC
TIO
N (
m)
ROTATION ANGLE (deg)
Q2C: Fundamental Physics Research in Space, May 06 S. Dell’Agnello, INFN-LNF26
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
Q2C: Fundamental Physics Research in Space, May 06 S. Dell’Agnello, INFN-LNF27
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
Q2C: Fundamental Physics Research in Space, May 06 S. Dell’Agnello, INFN-LNF28
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
Q2C: Fundamental Physics Research in Space, May 06 S. Dell’Agnello, INFN-LNF29
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
Q2C: Fundamental Physics Research in Space, May 06 S. Dell’Agnello, INFN-LNF31
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
Thermal shield (Cu)Vac. shellService turret
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
Q2C: Fundamental Physics Research in Space, May 06 S. Dell’Agnello, INFN-LNF33
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)
Q2C: Fundamental Physics Research in Space, May 06 S. Dell’Agnello, INFN-LNF35
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
Q2C: Fundamental Physics Research in Space, May 06 S. Dell’Agnello, INFN-LNF36
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
Q2C: Fundamental Physics Research in Space, May 06 S. Dell’Agnello, INFN-LNF38
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
Q2C: Fundamental Physics Research in Space, May 06 S. Dell’Agnello, INFN-LNF40
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