Probing gravity in NEO with LARES, a high-accuracy laser-ranged test mass

Probing gravity in NEO with LARES,

a high-accuracy laser-ranged test

mass

Simone Dell’Agnello Laboratori Nazionali di

Frascati (LNF) of INFNfor the LARES Collaboration (I.

Ciufolini PI)Int. School of Relativistic Astrophysics “J. A. Wheeler”, Erice, June 2006

LAGEOS array

LARES 1:2 proto

J. A. WHEELER SCHOOL, Erice, June 06 Simone Dell’Agnello, INFN-LNF2

Outline

• Probing gravity in NEO with the LARES

mission

• Thermal Non Gravitational Perturbations

• The INFN-LNF Space Climatic Facility to

test LARES and LAGEOS prototypes

• “Deep-space” versions of LARES to study

the Pioneer Anomaly

(From: I. Ciufolini talk at SpacePart, Beijing, April 06)

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

Focus of this talk

Measurement of frame-dragging w/LAGEOS


The new LARES mission

• Proposed to INFN in 2004– Satellite cost, to be funded by INFN, ~1 Million €

• Main physics goals– Measure frame-dragging with ≤ 1% accuracy

• A 2nd generation, fully-characterized satellite is needed to beat thermal NGPs down below 1%

– Test very-weak field limit of GR (1/r2 law) and new long range interactions (Yukawa-like potential) 103 improvement on in the ~ 10000 Km range

– Measure PPN parameters , with 10-3 accuracy, or better (measurement of the GR perigee precession @10-3)

€

Vyuk = −αGMearth

re

−r

λ

m

10-12

107

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

Yukawa-like potential Vyuk)


New physics with perigee precession ?

• Test BRANE-WORLD model, which can explain DARK ENERGY and SN acceleration: Dvali at al, PR D 68, 024012 (2003)

• Additional perigee precession of Moon and laser-ranged satellites

• Lunar ranging: = 1.4 x 10-12rad/orbit Dvali prediction

= 2.4 x 10-12rad/orbit present accuracy

10-fold improvement expected w/APOLLO


New physics with perigee precession ?

Dvali at al, PR D 68, 024012 (2003)

= 1.9 x 10-11/year, same for Moon and LAGEOS

• /(a more favourable to the moon

• But with large eccentricity SLR can achieve a better statistical error than LLR

• To cope with SLR systematic errors:– i = 63.4o (Molnya value) null perigee shift due to J2

– Large mass (≥ 1 ton)

– Eccellent control of NGPs … we will do this

• Bottom line: it would take a much more expensive mission than LARES


LARES baseline design and test program

• LAGEOS: = 60 cm, M ~ 400 Kg, 426 CCRs• LARES: ~ 30 cm, M ~ 100 Kg, 102 CCRs (size scaling)• Area/M ≤ than LAGEOS, for Non Gravitational

Perturbation

• Full thermal characterization, NEVER done for LAGEOS– CCR thermal relaxation time, CCR– 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, ‘76 LAGEOS II,

‘92


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

space conditions. Great help by space conditions. Great help by D. Currie (UMCP)D. Currie (UMCP) in the in the design of the SCFdesign of the SCF

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

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

• Measurement of Measurement of CCRCCR mandatory for the success of LARES mandatory for the success of LARES

• Characterization of LAGEOS and LARES prototypes in realistic Characterization of LAGEOS and LARES prototypes in realistic space conditions. Great help by space conditions. Great help by D. Currie (UMCP)D. Currie (UMCP) in the in the design of the SCFdesign of the SCF

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

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

• Measurement of Measurement of CCRCCR mandatory for the success of LARES mandatory for the success of LARES

Earth Infrared Yarkovsky effect.Drag first understood by Dave Rubincam (NASA-GSFC)

IR

Solar Yarkovsky effect

SUN


The Solar Yarkovsky effect on LAGEOS

CCR, CCR thermal

relaxation time

Spin pointing to sun

Sunlit pole

Victor J. Slabinski (USNO),

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

1/3

aMAX = 10-10 m/sec2

~ 1/9 the “PIONEER effect”

2/3

1/3

2/3


Testing the LAGEOS array at the SCF

Quartz window

IR camera Ge window

Earth IRsimulator

Thermal shield (Cu)

Vac. shell

Service turret

Solar beam shroud

Ø = 40 cm

LAGEOS matrixD = 15 cm

Solar NEO simulator

Ø = 10 cm

Ø = 30 cmT = 250 K

Alodized back in photo


The LAGEOS CCR array built at LNF

Picture in the Visible spectrum

Picture in the InfraRed


An “old” LAGEOS I prototype at NASA-GSFC


Effects of thermal forces on node and perigee

• The node long-term drift– Calculations of CCR vary from 2000 sec to 7000 sec, 250%. This implies a 2 % error on frame-dragging (I. Ciufolini)

– Our goal: measure CCR with ≤ 10% accuracy. This will give a 0.08 % error on frame dragging ==> negligible !

• The perigee long-term drift– Measuring and to 0.1% requires an accuracy on the perigee rate of 3 mas/yr. The 250% uncertainty on CCR gives a 19 mas/yr error on the perigee rate (I. Ciufolini)

– Our goal: measure CCR with ≤ 10% accuracy. This will give a 0.76 mas/yr error on the perigee rate ==> OK


CCR: results from full thermal simulation

Goal: measure CCR at ≤10% accuracy. With a 0.5 K accuracy on temperature this is well within statistical reach

SUN=on, IR=offCCR = 2400 ± 40 sec (2% error)(T) = 0.5 K

CCR T(K)

t(sec)

T = 278 K

T = 276 K

FEM model(250 nodes)at t = 2800 sec

http://www.thermaldesktop.com/index.html


Thermal simulation results on CCR

CCR 1/T3

Different Sun and IR conditions, incidence angle and temperature of the Al satellite body

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 room temperature to measure IR(x) and IR(x), where x = Al or CCR

• Qcamera = Qemission + Qreflected

• T4camera= IR T4

x + IR T4bkg

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

temperature = 10 oC or 50oC

IR(CCR) ~ 0.82IR(CCR) ~ 0.18IR(Al) ~ 0.15IR(Al) ~ 0.85

NEXT: outdoors, solar (x) and (x)

IR pictures of the LAGEOS array

Ø = 10 cm

LAGEOS array

Black disk

At 10 or 50 oC


Thermal model to be tuned to SCF data

Different cases for suprasil optical properties

258

268

278

288

04008001200160020002400280032003600400044004800520056006000640068007200760080008400880092009600100001040010800112001160012000

time [s]

Temperature [K]

Slabinsky Corner

Slabinsky Center

Case a Corner

Case a Center

Case a&e Corner

Case a&e Center

SOLAR= 0.15IR = 0.81

SOLAR= 0.015, IR = 0.81

SOLAR= 0.015, IR = 0.20

Different suprasil (CCR) thermo-optical properties( = absorptivity, = emissivity)

Time (sec)

CCR Temperature (K)


Simulation result on ageing of Al (LAGEOS CCR array)

Temperature shifts, but shape stays about the same: CCR insensitive, at 10%, to this large

variation of (Al)

CCR temperature with different values of Aluminum emissivity from = 0.05 ( ) LAGEOS II to = 0.2 ( ) LAGEOS to = 0.8

225

235

245

255

265

275

285

295

0400 900 14001900240029003400390044004900540059006400690074007900840089009400990010400109001140011900124001290013400139001440014900154001590016400

[ ]time s

[ ]CCR Temperature K

0.2CCR

0.3CCR

0.5CCR

0.05CCR

0.8CCR


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


Retro-reflectors are back-mounted

Al retainer ring will be inside

and thus will not give any thermal

force


LARES prototype built at LNF

LARES1:2 scale prototype


LARES prototype built at LNF

InfraRed images


FE model and thermal simulation of LARES

295.6 K

295.3 K

287 K

263 K

15000 nodes. Model 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 camera Ge window

Earth IR simulator

(Z306 paint)

Thermal shield (Cu)

Vac. shell

Service turret

Solar beam shroud

Ø = 40 cm

LARES proto

Ø = 30 cm

Solar NEO

simulator

Ø = 10 cm

Ø = 30 cmT = 250 K

Alodized back in photo


Status of the SCF

• All equipment delivered except Solar simulator

• Solar simulator acceptance test at TS-Space (UK) complete

• Now: outgassing, TL installation

VIS

BEAMSPLITTER

6kW METAL HALIDE LAMP

10kW QUARTZHALOGEN LAMP

RADIATION LOSS ~ 10%

UV

IR SUNAM0 SPECTRUM1366.1 W/m2


Measured Solar Simulator spectrum

“AM0 standard” spectrum from 400 nm to 3500 nm

Each lamp is calibrated with an Epply.com Solarimeter(accurate and stable over ten years to 1%)

HV adjusted to compensate for lamp ageing with feedback PIN diode

Wavelength (300-1800 nm)

Relative Intensity

AM0Measurementsbefore puttinganti-reflectivecoating on theQ-window

ACCEPTANCE TEST MAY 29, 2006


Measured Solar Simulator uniformity

(Max-Min)/(Max+Min)= 3%

ACCEPTANCE TEST MAY 29, 2006


LAGEOS range correction~ /2

0.250

0.248

0.246

0.244

0.242

0.240

Range correction (m)

350300250200150100500

Rotation 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

0.248

0.246

0.244

0.242

Range correction (meters)

350300250200150100500

Rotation angle (deg)

laser “viewing” equator

laser “viewing” pole

RANGE CORRECTION

(m)

ROTATION ANGLE (deg)

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


Optical characterization: FFDP

Test 1: Far-Field Diffraction Pattern (FFDP)

• “Optical FLAT” for absolute cross section measurement

• CCDs as laser beam profilers

Repeat test inside the SCFThanks to John Degnan (SC), Dave Arnold, Jan McGarry (GSFC) for advise and to Doug Currie (in photo) for help on 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 or Streak Camera (stop time)

• Mirror to expand the laser beam

Repeat test inside the SCF


Applications of the SCF

• Laser-ranged CCR arrays and spherical test

masses

• NEO : LAGEOS, LARES and arrays for GNSS constellations

• DEEP SPACE: new analysis and mission to study the Pioneer

effect

– Deep Space Gravity Probe (DSGP); proposed to ESA, for

the “Cosmic Vision” program, and to NASA

– Slava Turyshev, from NASA-JPL, is the PI

SCFSCF SCFSCF

Measurement Concept: Formation-flyingA MISSION TO EXPLORE THE PIONEER ANOMALYA MISSION TO EXPLORE THE PIONEER ANOMALY

Active spacecraft and passive test-mass Objective: accurate tracking of the test-mass 2-step tracking: common-mode noise rejection

– Radio: Earth spacecraft

– Laser: spacecraft test-mass

Flexible formation: distance may vary The test mass is at an environmentally quiet

distance from the craft, > 250 m Occasional maneuvers to maintain formation

Courtesy ofS. Turyshev (JPL)

SLR inDeep Space


The Pioneer Anomaly

• In the outer SS the probes with the most accurate and robust navigation capabilities are the PIONEERS– VOYAGERS: Deep Space, but factor 50 “less accurate”– GALILEO: inaccurate, up to Jupiter only– CASSINI: being studied, but still, only up to Saturn– Outer planet motions ? Saturn ?

• Doppler data (1987-1998, 40-70.5 AU) provide clear anomalous deceleration. Pioneer Explorer Collaboration.

aPIO = (8.74 1.33) 10-10 m/s2

– ~9 times the largest LAGEOS thermal forces

• Effect of asymmetric thermal forces due to forward-backward asymmetric thermo-optical parameters ? RTGs ?

• New physics ?


Status of the analysis

Courtesy of S. Turyshev (JPL)June 2006 issue of New Scientist


Status of the analysis

Courtesy of S. Turyshev (JPL). June 2006 issue of New Scientist


DSGP laser-ranged test masses

• Study of the Pioneer anomaly with ≥ 2 “lighter LARES”• Different masses/materials to test EP• Planet flybys for planetary science• Thermal NGPS; here we can contribute

– Solar constants beyond Saturn ≤ 10-2 NEO-AM0. Dedicated solar simulator ?

– IR radiation by planets. Disks with varying and T– Measure thermal properties in SCF, then use orbital

simular and thermal sw for full 10-80 AU orbit

• LAGEOS thermal forces ≤ 1/9 aPIO ! Our high-accuracy characterization of LARES will be extremely useful for DSGP

• The LARES mass and thermal model will be a mass, thermal and optical model for DSGP: for ~ 1 Km ranging, no need of expensive CCRs w/non-zero dihedral angle offsets

Testing DSGP laser-ranged masses at the SCF

Quartz window

IR camera Ge window

IR simulator for planet

encounters

Thermal shield (Cu)

Vac. shell

Service turret

Solar beam shroud

Ø = 40 cm

DSGP test mass

Deep Space Solar

simulator

Ø = 10 cm

Ø = ? cmT = ? K

Black Aeroglaze on one side; alodized on side shown by photo


Conclusions

• LARES will not be a mere LAGEOS III• Building on the 30-year experience of LAGEOS, we are designing a high-accuracy, 2nd generation test mass and a Space Climatic Facility to achieve (frame-dragging) ≤ 1%– Optimized and compact design to minimize thermal

forces and €’s– Full climatic and optical pre-launch characterization

• Application of expertise acquired on LARES to the DSGP mission– Submitted to ASI for the 2006-2008 study, as part of the “Physics of Gravitation” WP, led by I. Ciufolini

INFN Workshop at LNF, 21-23 March 2006

Measurement of frame-dragging w/LAGEOS

• Raw observed node Raw observed node residuals residuals combinedcombined

• Raw residuals Raw residuals with six periodic with six periodic signals removed, signals removed, estimated rate is estimated rate is 47.9 mas/yr47.9 mas/yr

• GR-predicted GR-predicted residuals, rate: residuals, rate: 48.2 mas/yr48.2 mas/yr

• Raw observed node Raw observed node residuals residuals combinedcombined

• Raw residuals Raw residuals with six periodic with six periodic signals removed, signals removed, estimated rate is estimated rate is 47.9 mas/yr47.9 mas/yr

• GR-predicted GR-predicted residuals, rate: residuals, rate: 48.2 mas/yr48.2 mas/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 −&

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

LAGEOS contribution to Space Geodesy

International Terrestrial Reference Frame (ITRF)

• Geocenter (100% LAGEOS) and Scale (60% LAGEOS)

- few mm accuracy• Axis orientation

- VLBI + LAGEOS (changes)


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

S. Turyshev, GREX05

47

A MISSION TO EXPLORE THE PIONEER ANOMALYA MISSION TO EXPLORE THE PIONEER ANOMALY

Need for a New Mission

We need a new experiment A “win-win” situation – standard and new physics, both important:

– If interpreted within STANDARD physics – important for solar system physics, astrophysics, also for advanced high-accuracy navigation;

– Discovering NEW physics …

Recent (2004-05) mission studies identified two options:– Experiment on a major mission to deep space

● Major impact on spacecraft & mission designs with questionable improvement over Pioneer

– A dedicated mission to explore the Pioneer Anomaly● Full characterization of the anomaly

Further advantages of a dedicated concept:– Demonstration of new technologies and capabilities

● Low disturbance craft, advanced thermal design, formation-flying, accurate navigation and attitude control, etc.

– Synergy with other science:● Solar system [plasma, dust…], Kuiper belt, GWs, heliopause.

A dedicated mission is both scientifically and technologically attractive

Courtesy of S. Turyshev

48


A Mission to Explore the Pioneer Anomaly

Scientific Objectives: – Investigate the source of the PA with a factor of a 1000 improvement;

– Improve spatial, temporal, and directional resolution;

– Identify and measure all possible disturbing and competing effects;

– Test Newtonian gravitational potential at large distances;

– Discriminate among candidate theories to explain the Anomaly;

– Study the deep-space environment in the outer solar system;

– Improve limits on the extremely low-frequency gravitational radiation.

Technological Goals:– Develop methods for precise spacecraft navigation & attitude control

(needed for all future interplanetary missions);

– Develop drag-free technologies operating at extremely low-frequencies (needed for next generation of GW missions);

– Develop fast orbit transfer scenarios for deep-space access, namely propulsion concepts (including solar sails) and power management at large heliocentric distances (including the use of RTGs);

– Develop advanced environmental sensors.

The mission will benefit many areas of the ESA Cosmic Vision 2020


Requirements for a New Mission

Navigation and Attitude Control – Spin-stabilized spacecraft; – 3-D acceleration sensitivity 10-12 m/s2, vlf/DC; – Propulsion system with precisely calibrated thrusters,

propellant lines & fuel gauges with real-time control;– X- and Ka-band with significant dual-band tracking; – Data types: Doppler, range, DOR, and VLBI.

Thermal design:– Entire spacecraft is heat-balanced & heat-symmetric;– Active control of all heat dissipation within & outward;– Knowledge of 3D vector of thermal recoil force;– Optical surfaces with understood ageing properties.

On-board power – RTGs:– Must provide thermal and inertial balance & stability.

Mission Design:– Hyperbolic escape trajectory beyond 15 AU; – Fast orbit transfer with a velocity of > 5 AU / year.

Most of the technology is readily available


Courtesy ofS. Turyshev

Experimental ConceptCandidate explanations: directional signatures

Central forces from the Sun: – Cosmological influence– Modified gravity, “fifth force”

Sun-pointing

Other Central forces–e.g. Galactic centre

Pointing towards the object

Blue shifting of light: –Varying speed of light,

cosmology

Along Earth-s/c vector

Drag: –Conventional, i.e. dust, gas; –Other, coupling to dark matter

Along velocity vector of dragging material

Modification of inertiaAlong velocity vector? Sun-pointing?

On-board systematics (heat, leaks) Along spin axis

DSN hard- and software: –Clock drift (varying constants?) –Ephemeris, Earth Orientation

Along Earth-s/c vector ?

This is a drag-free system with the test mass being outside the spacecraft


Common-mode noise rejection


The Sun Simulator QH: uniformity±3%

HMI: uniformity±3%

Measured !

300 ÷ 2400 nm

Wavelength (nm)

Relative Intensity

Our spectrum will be an AMO standard from 400 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 ageing

with feedback PIN diode


Beyond the baseline LARES optical design

• LAGEOS-geometry, BUT no dihedral angle offset and half 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


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 ccr 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)


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 be proven 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 = 54GPS-36 Number of CCR’s: 32GPS-36 Number of CCR’s: 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 CCRs) GIOVE-B (67 CCRs) GIOVE-A (76 CCRs) GIOVE-B (67 CCRs)

The hollow CCR could also be integrated The hollow CCR could also be integrated intointo

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

Beryllium Hollow CCR for GPS3

Courtesy of GSFC,Jan McGarry et al


RADIOASTRON

Moon

Approved mission Launch in 2008

Earth

MILLIMETRON (approved mission)

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

Bolometric sensitivity

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

Space-ALMA VLBI sensitivity 10-4 Jy ()

( =0.5 mm, 300 s int.), fringe size up to nanoarcseconds

@Lagrangian point L2

Documents

Probing gravity in NEO with LARES, a high-accuracy laser-ranged test mass