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

LAGEOS array. LARES 1:2 proto. Probing gravity in NEO with LARES, a high-accuracy laser-ranged test mass. Simone Dell’Agnello Laboratori Nazionali di Frascati (LNF) of INFN for the LARES Collaboration (I. Ciufolini PI).

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

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  1. LAGEOS array LARES 1:2 proto Probing gravity in NEO with LARES,a high-accuracy laser-ranged test mass Simone Dell’Agnello Laboratori Nazionali di Frascati (LNF) of INFN for the LARES Collaboration (I. Ciufolini PI) Int. School of Relativistic Astrophysics “J. A. Wheeler”, Erice, June 2006

  2. 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 Simone Dell’Agnello, INFN-LNF

  3. (stochastics errors, like seasonal variations of Earth grav. field, observation biases-range/spin) (From: I. Ciufolini talk at SpacePart, Beijing, April 06) Measurement of frame-dragging w/LAGEOS Focus of this talk

  4. 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 a in the l ~ 10000 Km range • Measure PPN parameters b, g with 10-3 accuracy, or better (measurement of the GR perigee precession @10-3) Simone Dell’Agnello, INFN-LNF

  5. Test of the very-weak field limit of GR (1/r2 law) and of new long range interactions (ie Yukawa-like potential Vyuk) a 10-12 107 l(m)

  6. 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: Df = 1.4 x 10-12rad/orbitDvali prediction sf= 2.4 x 10-12rad/orbit present accuracy 10-fold improvement expected w/APOLLO Simone Dell’Agnello, INFN-LNF

  7. New physics with perigee precession ? Dvali at al, PR D 68, 024012 (2003) Df = 1.9 x 10-11/year, same for Moon and LAGEOS • sf/(a Df)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 Simone Dell’Agnello, INFN-LNF

  8. 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, tCCR • 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 Simone Dell’Agnello, INFN-LNF

  9. IR A Space Climatic Facility at LNF • Characterization of LAGEOS and LARES prototypes in realistic space conditions. Great help by D. Currie (UMCP) in the design of the SCF • Asymmetric (Yarkovsky) thermal forces by CCRs are the largest NGPs on Lense-Thirring (~ 2 %) • NGPs driven by slow CCR thermal relaxation time, tCCR, never measured in space conditions • TECLIPSE ≤ 4300 sec, tCCR ~ 2000-7000 sec, TORBIT = 13300 sec • Measurement of tCCR mandatory for the success of LARES SolarYarkovsky effect Earth InfraredYarkovsky effect. Drag first understood by Dave Rubincam (NASA-GSFC) SUN Simone Dell’Agnello, INFN-LNF

  10. The Solar Yarkovsky effect on LAGEOS Spin pointing to sun Sunlit pole Victor J. Slabinski (USNO), Cel. Mech. Dyn. Astr. vol.66, 131-179 (1997) tCCR, CCR thermal relaxation time 1/3 1/3 2/3 aMAX = 10-10 m/sec2 ~ 1/9  the “PIONEER effect” 2/3 Simone Dell’Agnello, INFN-LNF

  11. Ø = 10 cm Ø = 30 cm T = 250 K Ø = 40 cm Testing the LAGEOS array at the SCF Service turret Thermal shield (Cu) Vac. shell LAGEOS matrix IR camera Ge window LNF SCF D = 15 cm Earth IR simulator Solar NEO simulator Quartz window Alodized back in photo Solar beam shroud Simone Dell’Agnello, INFN-LNF

  12. The LAGEOS CCR array built at LNF Picture in the Visible spectrum Picture in the InfraRed Simone Dell’Agnello, INFN-LNF

  13. An “old” LAGEOS I prototype at NASA-GSFC Simone Dell’Agnello, INFN-LNF

  14. Effects of thermal forces on node and perigee • The node long-term drift • Calculations of tCCR vary from 2000 sec to 7000 sec, 250%.This implies a 2 % error on frame-dragging (I. Ciufolini) • Our goal: measure tCCR with ≤ 10%accuracy. This will give a 0.08 % error on frame dragging ==> negligible ! • The perigee long-term drift • Measuring b and g to 0.1% requires an accuracy on the perigee rate of 3 mas/yr. The 250% uncertainty on tCCR gives a 19 mas/yr error on the perigee rate (I. Ciufolini) • Our goal: measure tCCR with≤ 10%accuracy. This will give a 0.76 mas/yr error on the perigee rate ==> OK Simone Dell’Agnello, INFN-LNF

  15. CCR T(K) SUN=on, IR=off tCCR = 2400 ± 40 sec (2% error) s(T) = 0.5 K t(sec) T = 276 K FEM model (250 nodes) at t = 2800 sec T = 278 K tCCR: results from full thermal simulation Goal: measure tCCR at ≤10%accuracy. With a 0.5 K accuracy on temperature this is well within statistical reach Simone Dell’Agnello, INFN-LNF

  16. TAl=300 K Sun ON IR OFF TAl=300 K Sun ON IR OFF 45 deg TAl=300 K Sun ON IR ON TAl=280 K Sun ON IR ON TAl=300 K Sun OFF IR ON TAl=280 K Sun ON IR OFF TAl=300 K Sun OFF IR ON TAl=320 K Sun ON IR OFF Thermal simulation results on tCCR tCCR 1/T3Different Sun and IR conditions, incidence angle and temperature of the Al satellite body Simone Dell’Agnello, INFN-LNF

  17. Preliminary measurement with IR camera IR pictures of the LAGEOS array • Indoor, in-air test at room temperature to measure eIR(x) and rIR(x), where x = Al or CCR • Qcamera = Qemission + Qreflected • T4camera= eIR T4x +rIR T4bkg • eIR(x) + rIR(x) = 1 • Tx w/thermocouple • Tbkg: black disk with controlled temperature = 10 oC or 50oC eIR(CCR) ~ 0.82 rIR(CCR) ~ 0.18 eIR(Al) ~ 0.15 rIR(Al) ~ 0.85 NEXT: outdoors, solar e(x) and r(x) Black disk At 10 or 50 oC Ø = 10 cm LAGEOS array Simone Dell’Agnello, INFN-LNF

  18. Different suprasil (CCR) thermo-optical properties (a = absorptivity,e= emissivity) aSOLAR= 0.15 eIR = 0.81 aSOLAR= 0.015, eIR = 0.20 CCR Temperature (K) aSOLAR= 0.015, eIR = 0.81 Time (sec) Thermal model to be tuned to SCF data Simone Dell’Agnello, INFN-LNF

  19. Simulation result on ageing of Al (LAGEOS CCR array) Temperature shifts, but shape stays about the same: tCCR insensitive, at 10%, to this large variation of e(Al) Simone Dell’Agnello, INFN-LNF

  20. 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 Simone Dell’Agnello, INFN-LNF

  21. Retro-reflectors are back-mounted Al retainer ring will be inside and thus will not give any thermal force Simone Dell’Agnello, INFN-LNF

  22. LARES prototype built at LNF LARES1:2 scale prototype Simone Dell’Agnello, INFN-LNF

  23. LARES prototype built at LNF InfraRed images Simone Dell’Agnello, INFN-LNF

  24. 295.6 K 287 K 295.3 K 263 K FE model and thermal simulation of LARES 15000 nodes. Model being optimized and fully debugged Steady steady with LARES in front of a solar lamp CCRs, front view Core, side view Simone Dell’Agnello, INFN-LNF

  25. Ø = 10 cm Ø = 30 cm T = 250 K Ø = 40 cm Testing LARES at the SCF Service turret Thermal shield (Cu) Vac. shell LARES proto IR camera Ge window LNF SCF Ø = 30 cm Earth IR simulator (Z306 paint) Solar NEO simulator Quartz window Alodized back in photo Solar beam shroud Simone Dell’Agnello, INFN-LNF

  26. BEAM SPLITTER RADIATION LOSS ~ 10% AM0 SPECTRUM 1366.1 W/m2 IR SUN 10kW QUARTZ HALOGEN LAMP VIS 6kW METAL HALIDE LAMP UV Status of the SCF • All equipment delivered except Solar simulator • Solar simulator acceptance test at TS-Space (UK) complete • Now: outgassing, TL installation Simone Dell’Agnello, INFN-LNF

  27. AM0 Relative Intensity Wavelength (300-1800 nm) 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 Measurements before putting anti-reflective coating on the Q-window ACCEPTANCE TEST MAY 29, 2006 Simone Dell’Agnello, INFN-LNF

  28. Measured Solar Simulator uniformity (Max-Min)/(Max+Min) = 3% ACCEPTANCE TEST MAY 29, 2006 Simone Dell’Agnello, INFN-LNF

  29. LAGEOS range correction~ /2 laser “viewing” equator RANGE CORRECTION (m) laser “viewing” pole 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 there were the same number of cubes. Since LARES has fewer cubes the two effects cancel each other so that the variation in the range correction is about the same as LAGEOS Simone Dell’Agnello, INFN-LNF

  30. 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 SCF Thanks to John Degnan (sSC), Dave Arnold, Jan McGarry (GSFC) for advise and to Doug Currie (in photo) for help on setting up the optical tests at LNF Simone Dell’Agnello, INFN-LNF

  31. Optical characterization: the range correction • Test 2: Ranging test • Collaboration 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 Simone Dell’Agnello, INFN-LNF

  32. SCF 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 Simone Dell’Agnello, INFN-LNF

  33. A MISSION TO EXPLORE THE PIONEER ANOMALY Measurement Concept: Formation-flying Courtesy of S. Turyshev (JPL) • 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 SLR in Deep Space

  34. 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 ? Simone Dell’Agnello, INFN-LNF

  35. Status of the analysis Courtesy of S. Turyshev (JPL) June 2006 issue of New Scientist Simone Dell’Agnello, INFN-LNF

  36. Status of the analysis Courtesy of S. Turyshev (JPL). June 2006 issue of New Scientist Simone Dell’Agnello, INFN-LNF

  37. DSGP laser-ranged test masses • Study of the Pioneer anomaly with ≥ 2 “lighter LARES” • Different masses/materials to test EP • Planet flybysfor 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 Simone Dell’Agnello, INFN-LNF

  38. Ø = 10 cm Ø = ? cm T = ? K Ø = 40 cm Testing DSGP laser-ranged masses at the SCF Service turret Thermal shield (Cu) Vac. shell DSGP test mass IR camera Ge window LNF SCF IR simulator for planet encounters Deep Space Solar simulator Quartz window Black Aeroglaze on one side; alodized on side shown by photo Solar beam shroud

  39. 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 s(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 Simone Dell’Agnello, INFN-LNF

  40. INFN Workshop at LNF, 21-23 March 2006

  41. µ = 99 % GR 5 to 10 % error Measurement of frame-dragging w/LAGEOS Earth rotation J drags space-time around it The node of LAGEOS satellites (a~12300 Km) is dragged by ~2 m/yr • Raw observed node residuals combined • Raw residuals with six periodic signals removed, estimated rate is 47.9 mas/yr • GR-predicted residuals, rate: 48.2 mas/yr Oct. 2004 EIGEN-GRACE02S 2004 data by GFZ 1993-2003 LAGEOS I and LAGEOS II data I.Ciufolini, E. C. Pavlis

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

  43. 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)

  44. Density (kg/m3) Thermal Conductance (W/mK) Al alloy 200 Cu alloy 391 W alloy 137 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 -3m2/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 Al alloy 2700 Cu alloy 8900 W alloy 16900÷18500 Simone Dell’Agnello, INFN-LNF

  45. S. Turyshev, GREX05

  46. Need for a New Mission Courtesy of S. Turyshev • 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

  47. A Mission to Explore the Pioneer Anomaly Courtesy of S. Turyshev • 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

  48. A MISSION TO EXPLORE THE PIONEER ANOMALY Requirements for a New Mission Courtesy of S. Turyshev • 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

  49. A MISSION TO EXPLORE THE PIONEER ANOMALY Experimental Concept Courtesy of S. Turyshev Common-mode noise rejection Candidate explanations: directional signatures This is a drag-free system with the test mass being outside the spacecraft

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