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
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Ho Jung Paik, Krishna Venkateswara, M. Vol Moody
Department of Physics, University of Maryland
Inseob Hahn, Talso Chui, and Konstantin Penanen
Jet Propulsion Laboratory
NASA ISS Workshop on Fundamental Physics
October 13-15, 2010, Dana Point, CA
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.
Smaller moments for 3
SMART test mass pairs
STEP test mass pair
Axis alignment 10-5 rad
with error compensation
Meander-pattern suspension coil for STEP
Orientations of the EP test masses with respect to the spacecraft spin axis (z)
Sliding mode Vertical mode
SMEX-ISS Concept Gate Review
(Standard Model And Relativity Test)
PI: Ho Jung Paik, U. Maryland
Co-I: M.V. Moody, U. Maryland
JPL Project Scientist: TB
To test EP and search for new interactions and particles beyond the Standard Model.
SMART supports NASA’s strategic goal:“Discover the origin, structure, evolution, and destiny of the universe.”
SMART will improve by 102 over Microscope mission, a factor of 10 short of STEP.
In orbit, Earth’s gravity is fully modulated,gaining 103 in signal,and accelerometers can achieve higher sensitivity (by 102-103).
SMART uses superconducting differential accelerometers, which are very similar to SGG, fully developed at UM.
ISLES was supported by Microgravity Program (MP) in 2002-06.
EP EP Accelerometer/ EP EP
Ti-PtPt-Nb Gradiometer Nb-TiNb-Nb
with CMRR = 109
ISS vibration noise spectra
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.
Launch Lock & Rotation
Payload Interface Unit (ISS/JEM-EF Interface)
HTV Carrier Interface
Management: Top-Level Schedule