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1. Test of the Equivalence Principle on ISS Ho Jung Paik, Krishna Venkateswara, M. Vol Moody Department of Physics, University of Maryland Collaborators: Inseob Hahn, Talso Chui, and Konstantin Penanen Jet Propulsion Laboratory NASA ISS Workshop on Fundamental Physics October 13-15, 2010, Dana Point, CA Paik-1

2. Scientific Value of EP Tests In string theory, the 10-D tensor gravitational field G has two partners: scalar field  (dilaton) and antisymmetric tensor field B. They are coupled to the other fields in ways generally violating the EP. Many scalar and pseudo-scalar partners of the graviton may survive as massless particles in the four-dimensional low energy world (dilatons, axions, moduli fields, etc.). The observed accelerating expansion of the universe is consistent with a cosmological constant , which is 120 orders of magnitude smaller than the quantum corrections to the vacuum-energy density. It is important to test the founding principles of GR, such as the EP, to the highest possible precision because the failure to quantize gravity and the  problem may be partly due to incompleteness of GR. Paik-2

3. Spherical Outer Test Mass • A spherical shell approximates a point mass more closely.  Smaller moments for  3 • Closure conditions satisfied: SMART test mass pairs (Example) STEP test mass pair Paik-3

4. Suspension and Alignment • Suspension and alignment by current along asingle tube  Axis alignment 10-5 rad  CMRR 108 with error compensation • Centering by currents on 4 auxiliary tubes Meander-pattern suspension coil for STEP Paik-4

5. Accelerometer Orientation x z y Orientations of the EP test masses with respect to the spacecraft spin axis (z) Paik-5

6. Technology Heritage • Superconducting Gravity Gradiometer (SGG) • Wire-based S/C technology • SGG for airborne gravity • Diff angular acc. • CMRR = 109 • SGG for 1-m 1/r2 law test • Diff linear accelerometer • CMRR  107 • 41013g Hz1/2 noise • Best resolution (104) of 1/r2 law at 1 m • SGG for submillimeter 1/r2 law test • Differential linear accelerometer • Search for extra dimensions to 20 m Paik-6

7. Levitation on a Single Tube • This critical technology has been demonstrated. Test setup • Measured frequency squared versus current squared: Sliding mode Vertical mode Screeningcurrent Wire S/C tube

8. P.I.: Ho Jung PaikJPL Contact: Inseob HahnJanuary 11, 2008 SMEX-ISS Concept Gate Review SMART (Standard Model And Relativity Test)

9. SMART: H.J. Paik, University of Maryland • Exp. module: JEM-EF, Site #9 preferred. • Goalminimum temperature: 2 K. • Science cold instrument mass: 10 kg. • Instrument power consumption:100 W. • Pointing:Rotation at 0.01 Hz about the ISS pitch (or roll) axis is required. • Science objectives: To test EP to 1017 at range  104 km. Most quantum gravity theories involve EP-violating forces. SMART tests GR and other theories beyond Einstein, and searches for new interactions and particles beyond the Standard Model. • Science team members: PI: Ho Jung Paik, U. Maryland Co-I: M.V. Moody, U. Maryland JPL Project Scientist: TB • JPL roles:Project management/ system engineering, support science instrument team, flight engineering, I&T, ATLO, CTM

10. Science Objectives • Science goals and objectives: To test EP and search for new interactions and particles beyond the Standard Model. • Relationship to the astronomy program objectives in NASA science plan: SMART supports NASA’s strategic goal:“Discover the origin, structure, evolution, and destiny of the universe.” • Relationship to other investigations: SMART will improve by 102 over Microscope mission, a factor of 10 short of STEP. • Justification for space: In orbit, Earth’s gravity is fully modulated,gaining 103 in signal,and accelerometers can achieve higher sensitivity (by 102-103).

11. Instrument • The current state of instrumentdevelopment: SMART uses superconducting differential accelerometers, which are very similar to SGG, fully developed at UM. • Diagrams of the instrument: • Mass and power:The instrument weighs 10 kg, and requires 100 W. • Limits to the sensitivity:ISS dynamic and gravity noise will be dominant. • Heritage:GP-B, which utilizes similar technologies, has flown. ISLES was supported by Microgravity Program (MP) in 2002-06. • Under NSF support, a ground ISL experiment is being performed. Detection circuit EP EP Accelerometer/ EP EP Ti-PtPt-Nb Gradiometer Nb-TiNb-Nb

12. Science Traceability: Baseline Investigation Airborne SGG with CMRR = 109 ISS vibration noise spectra

13. Mission Design • Level of microgravity required: 10–5g. • Temperature required: 2 K with stability to better than 0.1 K. • Servicing required after installation:None. • Uplink and downlink bandwidth required:<< 0.01 Mbps, 0.2 Mbps (ref: LTMPF PIA). • ISS payload accommodation location required: The dewar needs to be rolled about the pitch or roll axis at ~10–2 Hz. Site #9 of JEM-EF is a natural site that allows this rotation. However, SMART can be accommodated at any other sites, as long as it is rotatable. • Mission time:Minimum 3-month space operation. Launch Lock & Rotation System Grapple Fixture Radiator Electronics x Payload Interface Unit (ISS/JEM-EF Interface) HTV Carrier Interface Site #9

14. Management: Top-Level Schedule • Science instrument • 1.5 year for Phase A/B • 0.5 year between CDR and Del to system I&T • 0.5 year system I&T at JPL • 4 month ATLO • 4 month operation in space • 6 month data analysis • JEM-EF site #9 availability is a big assumption. • But we can occupy another site with more engineering and less science. Launch EOM Start PDR SRR CDR SIR Ph F PhC PhD PhE Ph A/B Yr #4 Yr #1 Yr #2 Yr #3