National Aeronautics and Space Administration

A Researcher’s Guide to:

Fundamental Physics

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This International Space Station (ISS) Researcher’s Guide is published by 

the NASA ISS Program Science Office.

Authors: 

Inseob Hahn Jet Propulsion Laboratory, California Institute of Technology

Nan Yu Jet Propulsion Laboratory, California Institute of Technology

Ulf Israelsson Jet Propulsion Laboratory, California Institute of Technology

John Goree University of Iowa

Executive Editor: Amelia Rai

Technical Editor: Neesha Hosein

Designer: Cory Duke

Cover and back cover: 

a. Fundamental Physics Research on the ISS spans research from understanding the quantum nature 

at very small scales to understanding gravitation and its role in shaping the destiny of the universe, 

at extremely large scales. The balance on the front cover depicts an artists rendering of the key role 

fundamental physics on the ISS has to measure these extremes of nature. (Credit: JPL graphics 

department)

b. Computer Simulation of 3D structures in a liquid-like dusty plasma. The color indicates the height 

above the bottom plane. For clarity, the diameter of dust particle microspheres is exaggerated. 

(Image credit: B. Liu and J. Goree, Phys. Rev. E 89, 043107 (2014)

c. Artist rendering of Cold Atom Laboratory Magneto Optical Trap with atom chip shown at the stop. 

(Image credit: CAL Project Scientist Rob Thompson, JPL)

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Figure 1. The planned Cold Atom Laboratory payload in an ISS experimental rack. (Source: NASA’s Jet Propulsion Laboratory CAL project)

Soaring 250 miles above Earth, the International Space Station (ISS) is a 

modern wonder of the world, combining the efforts of 15 countries and 

thousands of scientists, engineers and technicians. The ISS is a magnificent 

platform for all kinds of research to improve life on Earth, enable future space 

exploration and understand the universe. This researcher’s guide mini-book 

is intended to help potential researchers plan experiments that would be 

exposed to the space environment, while externally attached to or deployed 

from the ISS. It covers all the pertinent aspects of the space environment, 

how to best translate ground research to flight results and lessons learned 

from previous experiments. It also details what power and data are available 

on the ISS in various external locations.

The Lab is Open

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1. Microgravity, or weightlessness, alters many observable phenomena 

within the physical and life sciences. Systems and processes affected by 

microgravity include surface wetting and interfacial tension, multiphase 

flow and heat transfer, multiphase system dynamics, solidification, and 

fire phenomena and combustion. Microgravity induces a vast array of 

changes in organisms ranging from bacteria to humans, including global 

alterations in gene expression and 3-D aggregation of cells into tissue-like 

architecture.

2. Extreme conditions in the ISS environment include exposure to extreme 

heat and cold cycling, ultra-vacuum, atomic oxygen, and high energy 

radiation. Testing and qualification of materials exposed to these extreme 

conditions have provided data to enable the manufacturing of longlife reliable components used on Earth as well as in the world’s most 

sophisticated satellite and spacecraft components.

3. Low Earth orbit at 51degrees inclination and at a 90-minute orbit 

affords ISS a unique vantage point with an altitude of approximately 240 

miles (400 kilometers) and an orbital path over 90 percent of the Earth’s 

population. 

This can provide improved spatial resolution and variable lighting 

conditions compared to the sun-synchronous orbits of typical Earth 

remote-sensing satellites.

Unique Features of the ISS 

Research Environment

1. Microgravity, or weightlessness, alters many observable phenomena 

within the physical and life sciences. Systems and processes affected by 

microgravity include surface wetting and interfacial tension, multiphase 

flow and heat transfer, multiphase system dynamics, solidification, and 

fire phenomena and combustion. Microgravity induces a vast array of 

changes in organisms ranging from bacteria to humans, including 

global alterations in gene expression and 3-D aggregation of cells into 

tissue-like architecture.

2. Extreme conditions in the ISS space environment include exposure to 

extreme heat and cold cycling, ultra-vacuum, atomic oxygen, and highenergy radiation. Testing and qualification of materials exposed to these 

extreme conditions have provided data to enable the manufacturing of 

long-life reliable components used on Earth as well as in the world’s most 

sophisticated satellite and spacecraft components.

3. Low-Earth orbit at 51degrees inclination and at a 90-minute orbit 

affords ISS a unique vantage point with an altitude of approximately 240 

miles (400 kilometers) and an orbital path over 90 percent of the Earth’s 

population. This can provide improved spatial resolution and variable 

lighting conditions compared to the sun-synchronous orbits of typical 

Earth remote-sensing satellites.

Unique Features of the ISS 

Research Environment

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Why Use the International Space Station (ISS) as a Laboratory 8

Past Research Program 9

Complex Fluids and Soft Condensed Matter 9

Gradient Driven Fluctuations Experiment (GRADFLEX) 10

Plasma Kristall (PK-3+) 10

Fundamental Forces and Symmetries 11

Primary Atomic Reference Clock in Space (PARCS) Preliminary Design 11

Rubidium Atomic Clock Experiments (RACE) Concept Definition 12

Quantum Interferometer Test of Equivalence (QUITE) 13

Alpha Magnetic Spectrometer (AMS) 13

Other Fundamental Symmetry Experiments Studied for Flight on the ISS 14

Quantum Gases 14

Condensate Laboratory Aboard the ISS (CLASS) Concept Design 15

Matter Near Critical Phase Transitions 15

Lambda Point Experiment (LPE) 16

Critical Fluid Light-Scattering Experiment (ZENO) 16

Critical Viscosity Experiment (CVX) 17

Confined Helium Experiment (CHeX) 18

Low Temperature Microgravity Physics Facility (LTMPF)

Plans and Hardware Development 18

Opportunities for Research on ISS 20

Complex Fluids and Soft Condensed Matter 20

Plasma Kristall (PK-4) Development 20

PlasmaLab 21

Fundamental Forces and Symmetries 21

U.S. Participation in Atomic Clock Ensemble in Space (ACES) 22

Space Optical Clock (SOC) Collaboration 23

Quantum Weak Equivalence Principle (QWEP) Collaboration 24

Quantum Gases and Cold Atom Laboratory (CAL) 24

Matter Near Critical Phase Transitions 26

DEvice for the Study of Critical LIquids and Crystallization 27

Alice Like Insert (DECLIC-ALI)

Table of Contents

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Recommended Future Research Program 29

Complex Fluids and Soft Matter 29

Dusty Plasma Physics Facility (DPPF) 29

Fundamental Forces and Symmetries 30

Quantum Tests of Equivalence Principle and Space-Time (QTEST) 31

Microgravity Facility for Optical Reference Comb Experiments in Space

(Microg FORCES) 32

Space Optical Clock (SOC) NASA Sub-system 33

Quantum Weak Equivalence Principle (QWEP) NASA Sub-system 33

Relativistic Gravity Experiment At L2 (REGAL2) 33

Quantum Gases 34

Cold Atom Laboratory 2 (CAL2) 35

Macro Mechanical Quantum System Experiments 36

Matter Near Critical Phase Transitions 36

DECLIC-ALI-R and DECLIC ALI-2 37

Lessons Learned 38

ISS Facilities and How to use Them 39

U.S. Experiment Support Facilities 39

ESA and Japanese Aerospace Exploration Agency (JAXA) 

Research Support Facilities 40

Developing and Flying Research to ISS 42

Conducting an Experiment on the ISS: Review of the Unique Conditions of ISS 42

Environmental Conditions on the ISS: Microgravity 42

Environmental Conditions on the ISS: Vibration 43

Environment Conditions on the ISS: Radiation Environment 44

What Should Principal Investigators Know About 

Conducting Research on the ISS? 45

Citations 46

Acronyms 47

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Studies in fundamental physics address 

space, time, energy, and the building blocks 

of matter. The primary theories of modern 

physics are based upon Einstein’s theory of 

relativity and the standard model of particle 

physics. However, as scientists, we know that 

the picture painted by these theories remains 

incomplete. Einstein’s theory of gravitation 

remains unproved to be consistent with the 

theories that define other forces of nature 

in all length scales. Furthermore, recent 

astronomical observation and cosmological 

models strongly suggest that dark matter and 

dark energy, which are entities not directly 

observed and not at all understood, dominate 

these interactions at the largest scales. All these 

unexplained observations and inconsistencies point to the potential for discovery 

of new theories. The ISS provides a modern and well-equipped orbiting laboratory 

for long-term microgravity environment research. Routine and continued access to 

this environment allows for fundamental physics research to be performed from a 

completely different vantage point.

The International Space Station provides a unique space laboratory for a set of 

fundamental physics experiments with regimes and precision not achievable on the 

ground. Some of the advantages of the space environment for experiments include:

• Long-duration exposure to the orbital freefall environment.

• Ease of measurement of changes of 

gravitational potential and relative motions.

• Study of very small accelerations on 

celestial bodies. 

• Reduced atmospheric interference on the 

propagation of optical and radio signals.

• Ability to track and fit to theory very long 

time segments of body orbital motion.

Why use the ISS as 

a Laboratory 

Figure 2.1 Newton’s original thought experiment 

on the orbiting object around the Earth. (Source: 

Philosophie Naturalis Principia Mathematica, 1686)

Figure 2.2 Artist concept of the International Space 

Station as a laboratory for fundamental physics. 

(Source: NASA’s Jet Propulsion Laboratory) 

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In 2011, a decadal review commissioned by Congress was completed titled 

“Recapturing a Future for Space Exploration: Life and Physical Sciences Research for a 

New Era.” In the “Fundamental Physical Sciences in Space” section of the report, 

the highest priority recommendations are made in four research thrust areas:

• Research on Complex Fluids and Soft Matter.

• Research That Tests and Expands Understanding of the Fundamental Forces 

and Symmetries of Nature.

• Research Related to the Physics and Applications of Quantum Gases.

• Investigations of Matter in the Vicinity of Critical Points.

A vigorous NASA fundamental physics research program developed over, 

approximately, the last 20 years consisting of more than 100 ground-based 

investigations from institutions across the U.S. and 17 flight or flight definition 

experiments in the areas of: low temperature and condensed matter physics; laser 

cooling and atomic physics; and relativistic and gravitational physics. This section 

provides a summary of accomplishments to date from fundamental physics 

research performed on a non-crewed science satellite, the space shuttle and the ISS. 

In addition, this section identifies some of the initial design development activities 

performed during the same period of time. Initial experiments done on noncrewed satellites and the space shuttle demonstrated the benefits afforded by the 

microgravity space environment for performing research in these areas and led 

to the development of plans for advanced research on the ISS. In 2004, NASA 

elected to concentrate ISS research toward activities directly related to human 

exploration. U.S. investigations in the fundamental physics program were 

conducted on a lower priority basis. Recently, the U.S. fundamental physics 

program was expanded through an international agreement allowing U.S. 

researchers access to ISS European Space Agency (ESA) facilities to accomplish U.S. 

research investigations in the complex fluids, soft condensed matter physics, and 

atomic physics thrust areas.

Complex Fluids and Soft Condensed Matter

Research of complex fluids and soft condensed matter field is very rich and diverse. 

It includes colloids, emulsions, foams, liquid crystals, dusty plasmas, and granular 

material. Refined experiments in these topics can be used as models for a wide 

Past Research Program

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variety of the more complex physical phenomena witnessed in everyday life. Over 

the years, there have been a number of related investigations completed on noncrewed satellites, the space shuttle and the ISS. There have also been a few groundbased investigations completed in this sub-discipline.

Gradient Driven Fluctuations Experiment (GRADFLEX)

GRADFLEX was completed aboard a Russian 

Foton-M3 non-crewed science satellite in 2008. This 

ESA-led program was a collaborative effort of Italian 

and U.S. scientists. The U.S. principal investigator was 

University of California at Santa Barbara professor David 

Cannell. The objectives of the experiment were to study 

gradient-driven density and concentration fluctuations 

that are strongly enhanced in fluids by the absence of 

gravity and to achieve a quantitative understanding of 

gradient-driven fluctuations on Earth as well as in the 

Foton-M3 microgravity environment. The experiment 

used two samples, one a single-component fluid of 

a 3-mm-thick layer of carbon disulphide (singlecomponent), and the other a 1-mm-thick layer of 1.8-wt.-percent polystyrene 

(Molecular Weight 9,000) in toluene (mixture). These samples are representative of 

any single-component fluid or mixture. The samples were driven out of equilibrium 

by applying temperature differences across the layers, up to 30 Kelvin (K) for the 

single-component fluid and 20 K for the mixture. The experiment verified to a 

high level of accuracy the predicted gradient-driven fluctuations in fluid samples 

enhanced by the absence of gravity (Takacs, 2011; Vailati, 2011).

Plasma Kristall (PK-3+)

The “self-structuring in dusty plasma” project 

was carried out with the Plasma Kristall (PK-3+) 

instrument on the ISS. This investigation was a 

collaborative effort of Russian, German and U.S. 

scientists. Like its predecessor, PKE-Nefedov, PK3+ was a German-Russian-developed instrument. 

University of Iowa professor John Goree, the U.S. 

principal investigator, participated in the initial 

Figure 3.1.1 Long timescale 

fluctuations in microgravity and on 

Earth. (Source: A. Vailati et al, J. 

Phys: 327, 012023, 2011)

Figure 3.1.2 A Dusty Plasma in 

microgravity. (Source: J. Goree).

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design of the instrument and the data analysis. For this microgravity experiment, 

6.8 micron diameter polymer microspheres were injected into a symmetrically 

driven, radio frequency plasma discharge. The plasma was ignited from Neon inert 

gas at 120 mTorr and a 13 MHz Radio Frequency (rf) voltage of 44 Volts (V). The 

resonance frequency of a single layer of particles on the edge of a central void was 

measured by video microscopy allowing the determination of plasma parameters. 

The measured parameters included the particle charge and electron temperature. 

Ground-based measurement of the parameters is not possible. This experiment 

required the microgravity conditions available aboard the ISS. The absence of 

Earth’s gravity prevented severe sedimentation, which would have prohibited the 

formation of the 3-D particle suspension with its central void (Liu, 2009).

Fundamental Forces and Symmetries

Experiments related to fundamental forces and symmetries are performed to verify 

with high precision the underlying assumptions and the consequences of Einstein’s 

special and general theories of relativity as well as the standard model of physics. 

Gravitational interaction is the weakest of the four known fundamental forces of 

nature. Yet by virtue of its universal attraction, it is the dominant force at long 

ranges and plays a central role in forming the structure and governing the motion of 

planets, stars, galaxies, and exotic objects such as neutron stars and black holes. 

Over the years, NASA has sponsored about 32 researchers in this sub-discipline to 

perform ground-based research and develop plans for performing measurements on 

the ISS or using non-crewed science satellites. The research conducted to date has 

focused on: Einstein’s Equivalence Principle (EEP), Eddington’s gamma-parameter 

(the bending of light by a massive body), redshift tests of gravity, Lorentz symmetry, 

and the inverse square law (Turyshev, 2007).

Primary Atomic Reference Clock in Space 

(PARCS) Preliminary Design

Measurement tests of gravitational redshift, Lorentz 

symmetry and of EEP employ the use of a variety of 

high-precision clocks as a common technique. The 

Primary Atomic Reference Clock in Space (PARCS) 

was an ISS clock experiment that had the objectives 

of improving the current measurement precision 

Figure 3.2.1. Artist concept of Primary 

Atomic Reference Clock in Space. (Source: 

NASA’s Jet Propulsion Laboratory)

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capability of gravitational redshift, testing of local position invariance, and testing 

of the anisotropy of the speed of light. It also had the design goal to demonstrate 

global clock synchronization and comparison capability, leading to a better 

realization of the definition of the second. PARCS had completed its preliminary 

design prior to program termination. ESA has elected to develop the Atomic Clock 

Ensemble in Space (ACES), which is similar to PARCS and scheduled for ISS 

operation in the 2015.

Rubidium Atomic Clock Experiments (RACE) Concept Definition

RACE represents an advanced clock experiment to complement and extend the 

goals of science and technology established by its ISS predecessors. There are three 

primary goals envisioned for the RACE investigation:

• Advanced atomic clock science and techniques to enable measurements with 

accuracies of 1 part in 1017

• Significantly improve the classic clock test of general relativity

• Distribute the highest achievable time and frequency stability from the ISS

The RACE investigations are designed 

to extend the understanding of physical 

effects on atomic clocks to a fractional 

accuracy of 1017 and vastly improve the 

classic clock test of general relativity. 

A laser-cooled atomic clock based on 

the ground state hyperfine splitting in 

87Rb will be flown aboard the ISS and 

compared to a laser-cooled rubidium clock 

on the ground, as well as other clocks 

worldwide. The long atom interrogation 

time allowed by the microgravity environment makes it possible to achieve greater 

accuracy for laser-cooled clocks with high, short-term stability as compared to their 

earthbound counterparts. The use of 87Rb reduces the collision shift by a factor of 

30 over a similar cesium instrument, allowing greater stability and accuracy. 

Figure 3.2.2 Schematic for juggling microgravity 

Rubidium Atomic Clock Experiments. (Source: NASA’s 

Jet Propulsion Laboratory)

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Quantum Interferometer Test of Equivalence (QUITE)

The EEP is at the very foundation of modern physics and 

underpins Einstein’s general theory of relativity. Many 

theories beyond general relativity and the standard model 

predict a violation of EEP at various levels. Different 

techniques were explored for improving the test of EEP 

in space including the use of superconducting detection 

of the differential motion of freely-flying test masses in 

low-Earth orbit; free-fall test masses in a high-altitude 

balloon; and use of cold atoms and atom interferometry. 

The QUITE experiment definition was initiated to 

employ the use of cold atoms and atom interferometry. 

The concept design developed would measure the 

differential acceleration of two different atomic species, 

laser cooled first to close to zero temperature in the 

atom interferometer configuration. In this experiment, the quantum wave nature 

of atomic particles is utilized; therefore, QUITE would also probe for connections 

between quantum-mechanical properties and gravity.

Alpha Magnetic Spectrometer (AMS)

The Alpha Magnetic Spectrometer is a state-ofthe-art particle physics detector. The purpose of 

the AMS is to study the universe and its origin 

by searching for antimatter and dark matter 

while performing precision measurements of 

cosmic rays composition and flux. The AMS 

was built, tested and is being operated by an 

international collaboration of 56 institutions 

from 16 countries and is sponsored by the 

United States Department of Energy. The experiment is located externally on the 

ISS and attached to the upper Payload Attached Point (S3) on the main truss. The 

core of the spectrometer is a large magnet and precision spectrometer to measure 

the sign of the charge of each particle traversing the instrument. The spectrometer 

is designed to collect data continuously producing a data stream of 10 gigabits per 

second, which, after processing, is reduced to approximately 13 megabits per second 

average of downlink bandwidth. As of July 2013, the AMS has measured over 35 

billion particles. 

a87 a85

Figure 3.2.3 Freely falling clouds of 

atoms of different atomic number. 

(Source: NASA’s Jet Propulsion 

Laboratory)

Figure 3.2.4. The Alpha Magnetic Spectrometer 

Research Facility. (Source: NASA)

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Other Fundamental Symmetry Experiments Studied for Flight on the ISS

NASA also sponsored the definition of five other flight experiments before the 

reprioritization of ISS program objectives in 2004. They are listed below.

• Satellite Test of the Equivalence Principle, F. Everitt, Stanford University.

• Superconducting Microwave Oscillator Experiment, J. Lipa, Stanford 

University.

• Inverse Square Law Experiment in Space, H. Paik, University of Maryland.

• Test of Equivalence Principle in an Einstein Elevator, I. Shapiro, Harvard 

University.

Quantum Gases 

One of the exceptional achievements in 

science and technology in the last two 

decades is in the research area of cold 

atoms. The invention and development of 

laser cooling of neutral atoms to extremely 

low temperatures was recognized with a 

physics Nobel Prize to two U.S. scientists, 

S. Chu and W. D. Phillips, and a French 

researcher, Claude Cohen-Tannoudji, 

in 1997. Further cooling of the atoms 

resulted in generation of a Bose-Einstein 

condensate (BEC), a new dilute gas 

quantum state that was predicted 

by Einstein but only arguably observed in confined liquid helium before. The 

generation of dilute gas quantum degenerate states for both bosons and fermions 

opened up an entirely new frontier in quantum and material science research. 

Three U.S. scientists, W. Ketterle, C. E. Wieman, and E. A. Cornell, were awarded 

a physics Nobel Prize in 2001 for their contribution to the first demonstration of 

BEC generation. Three of these Nobel laureates were NASA fundamental physics 

program sponsored investigators.

Over the years, NASA has sponsored about 23 researchers in this sub-discipline to 

perform ground-based research and develop plans for performing measurements on 

the ISS.

Figure 3.2.5. Emergence of a Bose-Einstein condensate. 

(Source: Eric Cornell, Joint Institute for Laboratory 

Astrophysics, Univ. of Colorado)

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Condensate Laboratory Aboard the ISS (CLASS) Concept Design

At the temperature of BEC, gravity can play a significant role in the cooling, 

trapping and dynamics of the ultra-cold atoms. Recognizing the potential benefits 

that microgravity research in this science area aboard the ISS might yield, the 

concept design of the CLASS was developed. CLASS was intended to provide 

researchers the capability to explore interactions in Bose Einstein Condensates 

of atoms at lower temperatures than achievable on the ground. The principal 

investigator for this experiment was Nobel laureate W. Phillips from the National 

Institute of Standards and Technology (NIST) in Gaithersburg, Maryland.

Matter Near Critical Phase Transitions 

The condensed phase of simple gases 

provides a unique test bed for the predictions 

of fundamental theories. For a certain 

combination of temperature and pressure, 

determined by the molecular properties of 

the gas, the differences between the liquid 

and the vapor phases disappear. This state 

of the system is the critical point, in the 

neighborhood of which the fluid system 

exhibits the unusual properties of universality 

and scaling. Universality implies that 

the same parameters (critical exponents) 

characterize the system under many different 

conditions; scaling implies that the equations 

describing the system’s behavior do not 

change their form when the length scale is altered. Critical points are found in 

many different materials including fluids, solids, alloys, fluid mixtures and magnets.

The physics of matter near critical points have been explored in detail in groundbased experiments. Fundamental theories have been developed to explain the 

unusual behavior of universality and scaling for matter near critical points. 

The special interest in this phenomenon is because the theoretical explanation, 

renormalization group (RG) theory, has implications for many diverse fundamental 

and applied research areas including weather modeling, metallurgy, oil field 

recovery, elementary particle physics, and cosmology. The region very close to the 

critical transition, where correction terms are small compared to critical anomalies, 

Figure 3.3.1. Heat capacity of superfluid helium in 

microgravity conditions. (Source: J. Nissen)

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provides the best tests of RG theory. The ISS microgravity environment provides 

advantages for the study of matter near critical points since the density nonuniformity caused by Earth’s gravity broadens the transition and limits how closely 

the critical point can be approached (Barmatz, 2007). 

In total, about 80 investigators were supported in a period of over a decade for 

various studies in the critical phenomena area through 2004. Four experiments in 

this research area were successfully completed aboard the space shuttle, and a major 

low-temperature facility was developed to the near completeness. The four shuttlebased experiments are discussed in the following paragraphs.

Lambda Point Experiment (LPE)

LPE performed a very high-resolution measurement of the heat capacity of a golf 

ball-sized sample of liquid helium to within 2 nanokelvin (nK) of the critical 

point under microgravity conditions on the space shuttle in 1996. The principal 

investigator was Stanford University Professor John Lipa. The LPE verified that the 

critical point remains sharp down to the 1 nK level, demonstrated unambiguously 

that gravitational smearing could be removed by conducting the experiment in a 

microgravity environment and that very complex measurements can be performed 

in a space environment. The optimum value for the critical exponent characterizing 

the divergence of the heat capacity below the transition was found to be -0.01285, 

giving improved support for the RG theory of phase transitions. Additional 

information was also obtained related 

to the temperature dependence of the 

thermal conductivity just above the 

transition (Lipa, 1996). 

Critical Fluid Light-Scattering 

Equipment (ZENO)

The ZENO experiment flew as a 

payload on the space shuttle in 1994 

and in 1996. The ZENO experiment 

provided new data, impossible to 

achieve through ground-based research, 

about the decay rates of critical-density 

fluctuations in a simple fluid (xenon) 

very near its liquid-vapor critical point. 

Figure 3.3.2 The chart shows ground-based and microgravity 

measurements of the viscosity of xenon near the critical 

point. In microgravity, the increase of viscosity is measured 

100 times closer to the critical temperature (Tc) and much 

more accurately than on Earth. The asymptotic power law 

characterizes the universal behavior of viscosity in all pure 

fluids near the critical point. (Source: NASA’s Glenn Research 

Center)

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The experiment employed laser light scattering and photon correlation spectroscopy 

to achieve its research objectives (Boukari, 1995). Related experiments are severely 

limited on Earth because of the presence of gravity. Gravity-related accelerations 

will cause large density gradients in the experiment sample, which is highly 

compressible near the critical point. ZENO’s principal investigator was University 

of Maryland Professor Robert Gammon.

Critical Viscosity Experiment (CVX)

The Critical Viscosity Experiment (CVX) successfully flew on the space shuttle 

in 1997, 1999 and 2003. For the initial flight the instrument contained a novel 

viscometer built around a small nickel screen. An oscillating electric field made 

the screen oscillate between pairs of electrodes. Viscosity, which dampens the 

oscillations, can be calculated by measuring the screen motion and the force 

applied to the screen. The screen oscillations were set to be slow and small to ensure 

the fluid’s delicate state near the critical point would not be disrupted. The data 

demonstrated that the viscosity increases as the critical point is approached and 

that it agrees with the theoretical prediction (Berg, 2009). CVX also measured lowfrequency viscoelasticity in a pure fluid for the first time. Viscoelasticity is a partly 

elastic response to shear stress. It is common in polymers, foams, and other complex 

fluids, but has never been observed in a simple fluid such as xenon.

Because of the great success of CVX, 

the instrument was upgraded to allow 

measurements of the shear thinning 

of viscosity near the critical point of 

xenon for its second and third flights. 

CVX was the first experiment to 

measure shear thinning in a simple 

fluid (Berg, 2007). The quantitative 

understanding of shear thinning 

near the critical point achieved 

through CVX will lead to a better 

understanding of shear thinning 

in more complex fluids, such as 

polymers and emulsions, and may 

have broad applications in science 

and industry. Figure 3.3.3. Confined Helium Experiment data show deviations 

from bulk values (dashed lines) as the critical point is approached. 

(Source: J. Nissen).

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Confined Helium Experiment (CHeX)

The CHeX flew on the space shuttle in 1998. This experiment studied the 

confinement of a thin layer of liquid helium confined to a thin sheet. The principal 

investigator was Stanford University Professor John Lipa. CHeX studied the 

influence of boundaries on matter with particular focus on how finite size effects 

emerge as the sample size evaluated becomes comparable with the size over which 

the sample is correlated. By operating near the critical point of liquid helium in 

space, a macroscopic sample size of 57 microns could be used thereby reducing 

surface effects while magnifying the finite size effect. The results from CHeX were 

in good agreement with theoretical predictions and allowed an extension by several 

orders of magnitude in size compared to what had been accomplished through prior 

ground-based investigations (Lipa, 2000).

Low Temperature Microgravity Physics Facility (LTMPF) Plans and 

Hardware Development

Plans were developed for an ISS 

LTMPF to allow future related 

investigations following the 

successful shuttle experiments. 

The LTMPF would provide a 2 

K environment for two separate 

instruments for a six-month 

duration as an ISS external 

payload mounted on the Japanese 

Experiment Module - Exposed 

Facility (JEM-EF). Many of the 

hardware elements were delivered 

and are in storage awaiting 

potential future use. A list of 

the planned investigations with 

this facility and their respective 

Figure 3.3.4. LTMPF dewar system vacuum shell hardware. investigators is shown below.

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• Critical Dynamics in Microgravity, R. Duncan, University of Missouri.

• Microgravity Scaling Theory Experiment, M. Barmatz, NASA’s Jet Propulsion 

Laboratory (JPL).

• Boundary Effects on the Superfluid Transition, G. Ahlers, UCSB.

• Superfluid Universality Experiment, J. Lipa, Stanford University.

• Coexistence Boundary Experiment, Inseob Hahn, JPL.

• Enhanced Heat Capacity of Superfluid Helium in a Heat Flux, 

D. Goodstein, Caltech.

• Experiments Along Coexistence near Tricriticality, M. Larson, JPL.

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A series of ISS flight experiments have been initiated in the fundamental 

physics/physical sciences discipline. Recent investigations are a part of bartering 

arrangements with foreign space agencies to optimize use of research facilities and 

instruments on the ISS. Also as a part of the ISS 2014 initiative, NASA began 

development of the ISS experiment Cold Atom Laboratory (CAL) facility.

Complex Fluids and Soft Condensed Matter

A number of Complex Fluids and Soft Condensed 

Matter related investigations utilizing the Fluid 

Integrated Rack (FIR) facility are ongoing. Many of 

these activities were described as part of the Complex 

Fluids discipline discussion earlier. A current focus 

is the research of “dusty plasmas”. A dusty plasma 

occurs when micro-sized particles of solid matter are 

added to an ionized gas (plasma). Plasmas exhibit 

a rich variety of collective behavior because the 

electrons and ions are all electrically charged and 

apply forces upon one another resulting in collective 

interaction. As a result, plasmas exhibit processes like 

nonlinear waves, hydrodynamic flow instabilities, 

anomalous transport, and statistical fluctuations. All 

these phenomena become more pronounced when 

the micron-size particles of solid matter, called dust, are added to the mix. The dust 

particles accumulate a large, negative electric charge, about 10,000 electrons on a 

5-micron sphere, by absorbing electrons from the surrounding plasma. Because they 

have large, negative charges, dust particles repel one another strongly, and they tend 

to arrange themselves spatially as do atoms in a crystal. By using video microscopy, 

experimenters can track the motion of individual particles and study phenomena 

such as phase transitions, viscoelasticity and the interaction of beams with matter.

Plasma Kristall (PK-4) Development

The PK-4 instrument is an ESA project that is scheduled to fly on the ISS in 

2014. In contrast to previous rf instruments, PK-4 will use a dc-voltage to power 

a plasma discharge in a glass tube. Combined with laser manipulation and highspeed cameras, the instrument will allow the microscopic observation of motion in 

liquid-like structures. Experiments planned in PK-4 include measurement of nonOpportunities for 

Research on ISS 

Figure 4.1. A 2004 Journal cover 

highlighting Dusty Plasma. (Source: 

Physics Today)

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Gaussian statistics of particle motion, diffusion, viscosity, and beam motion in a 

liquid. U.S. principal investigator Professor John Goree at the University of Iowa is 

a member of ESA’s Facility Science Team.

PlasmaLab

PlasmaLab is an ESA ISS experiment that 

will employ a dodecahedral-shaped chamber 

to enable study of a 3-D dusty plasma. 

Central objectives of this investigation 

are to develop an understanding of selforganization, study equilibrium and 

non-equilibrium phase transitions, phase 

separation, cooperative phenomena, and 

to extend the understanding of the plasma 

state of soft matter. U.S. principal investigators on the scientific team are University 

of Iowa professor John Goree, Auburn University professor Edward Thomas, Jr., 

and University of California at San Diego Dr. Marlene Rosenberg. Prototypes of 

the experiment hardware are under development in Germany to support a planned 

launch date of 2017. 

Fundamental Forces and Symmetries

Experiments associated with fundamental forces and symmetries are designed to test 

our understanding of Einstein’s general theory of relativity. Such experiments may 

also discover any additional weakly coupled, long-range interactions in physical law. 

The “classic” tests of Einstein’s theory of gravity were astronomical in nature. The 

theory explained the anomalous precession of the perihelion of Mercury’s orbit about 

the sun. His theory predicted the deflection of light passing close by the sun during 

a total eclipse, and it predicted the frequency shift (redshift) of light as it emerges 

from the gravitational field of stars. ISS provides the continued and routine access to 

space, which in conjunction with modern technologies, have opened a new frontier 

for testing gravitational theory through unprecedented measurement precision.

The ISS provides continued human research access to the space environment, which 

affords the following advantages for unprecedented investigations:

• Long-duration exposure to the orbital free-fall environment.

• Ease of measurement of changes of gravitational potential and relative motions.

Fig. 4.1.1 Scientific package in the European Space 

Agency’s Plasma Kristall instrument. (Source: J. Goree). 

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• Study of very small accelerations on celestial bodies. 

• Reduced atmospheric interference on the propagation of optical and radio signals.

• Ability to track and fit to theory very long time segments of body orbital motion.

Current fundamental forces and symmetries-related experiments under 

development for flight on the ISS are described in the following paragraphs.

US participation in Atomic Clock Ensemble in Space (ACES)

Four U.S. investigators have taken part in ESA’s 

ACES project. ACES features the ISS operation 

of an atomic clock accurate to one part in 1016

for tests of fundamental physics and for providing 

high-accuracy comparisons of ground-based optical 

clocks through a microwave space-to-ground link. 

ACES is planned for installation on the ISS external 

payload facility of the Columbus module. Launch 

could occur as early as 2015 based on current 

development plans. 

The scientific objectives of the ACES project are to 

utilize the ISS laboratory to:

• Demonstrate an atomic clock on the ISS accurate to one part in 1016, measure 

the Earth’s gravitational redshift to two parts in 106, and test relativistic effects 

in the frequency comparisons of moving clocks. 

• Search for a time variation of the fine structure constant to better than one part 

in 1017 over a year period.

• Search for Lorentz transformation violations to the one part in 1010 level.

• Use ACES to perform time synchronization and time transfer experiments 

(both space to ground and ground to ground) and to allow comparison between 

ground clocks to a fractional frequency resolution of 1 part in 1017 after a few 

days of run time.

 As part of the ACES collaborative investigation, microwave ground stations will 

be installed at a number of locations around the Earth so that global links to ACES 

Figure 4.2.1. Schematic of ACES global 

time transfer comparison. (Source: Luigi 

Cacciapuoti, European Space Agency 

Atomic Clock Ensemble in Space project).

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can be maintained during each ISS orbit. At each ground station, ground clock 

signals will be linked up to the ISS ACES payload through microwave ground 

terminals. This will allow common view and non-common view clock comparison 

experiments. The link precision will be more than ten times better than the 

current Global Positioning System carrier phase time-frequency transfer scheme. 

Two microwave ground stations will be established in the U.S., one at the JPL in 

Pasadena, Calif., and the other at the NIST in Boulder, Colo.

Space Optical Clock (SOC) Collaboration

Two U.S. investigators were selected for 

collaborative ground research supporting ESA’s 

Space Optical Clock (SOC) project. The SOC 

project will develop and operate a high-performance 

optical clock with a predicted accuracy of one part 

in 1017. It is planned for installation on the external 

payload facility of the Columbus Module on the 

ISS before the end of this decade. The scientific 

objectives of the SOC project are to utilize the ISS 

laboratory to:

• Demonstrate an optical clock on the ISS accurate to one part in 1017, measure 

the Earth’s gravitational redshift to two parts in 107

, and test relativistic effects 

in the frequency comparisons of moving clocks. 

• Perform a null measurement of the sun’s gravitational redshift to two parts in 107.

• Use the SOC to perform differential geo potential measurements with 1 

centimeter (cm) height resolution on the geoid; such measurements are based 

on the comparison of measurements with distant clocks located on ground.

• Use the SOC to perform time synchronization and time transfer experiments 

(both space to ground and ground to ground) and to allow comparison between 

ground clocks to a fractional frequency resolution of 1 part in 1018.

The U.S. scientists are collaborating as a part of the international science team and 

are supporting the development of required technology, investigation of the clock 

system, and design studies of the hardware. In addition, the U.S. participants will 

perform research contributing to the overall scientific objectives, participate in time 

transfer and clock frequency comparison activities from the ISS clock to ground 

clocks, technology maturation activities, trade studies, and data analysis.

Figure 4.2.2.Schematic view of an optical 

frequency comb, a key element for the 

Space Optical Clock. (Source: K. Vahala)

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Quantum Weak Equivalence Principle (QWEP) Collaboration

A team of U.S. investigators have taken 

part in ESA’s Quantum Weak Equivalence 

Principle (QWEP) project. The QWEP 

project will perform an atom interferometry 

test of the Weak Equivalence Principle 

by measuring the differential acceleration 

experienced by two clouds of ultra-cold, 

rubidium atoms composed of different 

atomic isotopes. QWEP is planned for 

installation on the ISS Columbus Module as 

either an internal experiment or as an external payload in the 2020 timeframe. 

The scientific objectives of the QWEP project are to utilize the ISS research 

laboratory to:

• Test the Weak Equivalence Principle using quantum particles to better than one 

part in 1014.

• Validate the technology for a matter wave sensor in space through demonstration 

of differential atom interferometry and gravity gradiometer measurements.

• Investigate condensate properties in microgravity.

• Demonstrate atom interferometry with ultra-cold atom sources in space.

The U.S. investigators will participate on the international science team and 

support the assessment the QWEP measurements, develop required risk mitigation 

methods and corresponding technologies, investigate measurement methodologies, 

and support hardware design studies.

Quantum Gases and Cold Atom Laboratory (CAL)

CAL will provide a highly flexible Bose-Einstein condensation laboratory in 

space to carry out a variety of experimental studies of BEC and other quantum 

gases, atom lasers, and atom optics. CAL will have the performance capability 

comparable to a state-of-the-art ground experiment in terms of the number of 

atoms condensed, the ability to tune interactions and control trapping potentials 

and the diagnostic capability. The CAL payload is planned to fit into a double 

rack housing the physics package and a single rack accommodating laser system. 

Figure 4.2.3 Schematic of atom interferometer for 

QWEP. (Source: Acta Astronautica, 67, 1059, 2010)

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The payload anticipated mass is 82 Kg, and 

power required is 187 Watts. The experiment 

will be automated, limiting the need for crew 

interaction. 

The first generation of Bose condensation 

experiments required large, well-equipped 

laboratories, staffed with teams of scientists 

often working around the clock. In contrast, 

the field has now matured to the point that 

low-power, rugged and portable BEC systems 

are commercially available and entirely 

automated. Such systems could be validated 

for space with relatively minor modifications. 

It should be stressed, however, that for many 

state-of-the art capabilities such as the ability 

to trap multiple species or load into an optical 

lattice (an array of potential wells formed by 

a standing, wave laser beam), the complexity 

of the system will increase dramatically. The 

CAL development schedule and budget include 

allowances for development of such capabilities.

The heart of the facility will be an “atom 

chip.” This consists of micro fabricated 

wires patterned on a dielectric surface. For 

appropriate geometries of the wires, the 

magnetic field produced by a current through 

these wires produces exceptionally tightly 

confining magnetic traps. Because of this tight 

confinement, evaporative cooling proceeds very 

rapidly and efficiently, allowing condensates of 

a few hundred thousand atoms to be produced 

within seconds. In a microgravity environment, 

it is expected that this process will be more 

efficient, thus allowing larger condensates than a comparable system can achieve on 

the ground. The atom chip will be placed in an ultra-high vacuum chamber, along 

with one or more atomic sources. Rb, K, and Li are possible candidates. 

Each may be incorporated, even if initial experiments only utilize one or two. 

Figure 4.2.4. The planned Cold Atom Laboratory 

payload in a double rack housing the physics 

package and a single rack accommodating laser 

system. (Source: NASA’s Jet Propulsion Laboratory 

Cold Atom Laboratory project)

Figure 4.2.5. Difference between laser cooled 

fermions and bosons showing the effect of the 

Pauli Exclusion Principle in fermions. (Source: 

Kettelle et al, Nature 416, 211, 2002)

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This flexibility will increase the range of experiments that may be explored for 

future payloads. 

Because of the high efficiency of the atom chip approach, only modest laser powers 

(tens of milli Watts [mW]) are needed to prepare and detect the cold atoms. This 

will allow the laser system to be quite modest. Two laser frequencies are needed 

per species (a trapping/detection laser and a “repumper” laser). Each species is 

envisioned to have a single Extended Cavity Diode Laser modulated to provide the 

repumper frequency. An additional laser of modest power (<2mW) would be used 

for an optical lattice. The laser system baseline approach is to utilize a Commercial 

Off The Shelf (COTS) system. 

When the decadal review was completed, there were no planned NASA 

investigations or collaborations with ESA in the fundamental physics research 

area. NASA has recently decided to develop the CAL for use on ISS in the 2017 

timeframe. Taking the advantage of the absence of gravity, CAL promises access 

to the coldest spot in the universe—the space environment. The primary science 

objective for CAL is to utilize the cold temperature region to allow scientists to 

study ultra cold quantum gasses, collisions at the extreme low energy, and quantum 

interfaces and decoherence of macroscopic quantum clouds. CAL will be used 

for studying condensate expansion of clouds of atoms into extremely weak traps 

to achieve temperatures an order of magnitude below what has been achieved in 

terrestrial experiments. The facility will be used to study mixtures of Bose and Fermi 

gases at extremely low temperatures with tunable interaction strengths, to study 

quantum gases in optical lattices (arrays of potential wells formed by standing wave 

laser beams) of varying strength and dimensionality, and to study “atom lasers” and 

matter wave propagation in microgravity with long interaction times. CAL will be 

also a pathfinder experiment for future cold atom experiments in space including 

fore-mentioned QWEP.

Matter Near Critical Phase Transitions

The study of critical phenomena began over 180 years ago with observations of 

the supercritical phase and critical point of CO2

. Shortly thereafter, Van der Waals 

developed an equation of state and applied it to the liquid gas critical point. This 

equation was later extended to a wide range of critical points observed in solid 

systems. The concept of an order parameter by Landau successfully explained 

the singular behavior of the thermodynamic behavior in the early era of critical 

phenomena studies. As more precise experimental techniques were developed, 

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it became apparent the behavior of the real 

systems was inconsistent with the predictions 

of Landau’s model. The concepts of scaling and 

universality were developed to better explain 

the critical phenomena observed. A key feature 

of a continuous phase transition in many 

physical systems in nature is scale-invariance 

in fluctuations of the order parameter, which 

implies continuity between large and small 

scale fluctuations associated with the transition. 

Scale-invariance occurs in many systems 

that are not completely understood such as 

the universe at the onset of the big bang as 

envisioned by cosmologist, the clustering of 

galaxies, massless fields in elementary particle 

physics, the distribution of earthquakes, and 

turbulence in fluids and plasmas. In each 

example cited, there is a wide range of scales 

over which some phenomena vary as a powerlaw of the scale. The RG theory is the most successful approach developed to date 

to derive and explore the relations between the characteristics of a system as viewed 

on different length scales. Many scientific investigations using liquid-gas critical 

point systems have been performed on the ground to test the theoretical predictions 

very close to the critical point. The predictions of the RG theory have been 

reasonably well validated. Nevertheless, the theory is based on assumptions that 

need to be validated based on more sophisticated experiments. Thus, it is important 

to test RG theory to the utmost precision achievable. Currently, there is one critical 

phenomena experiment ongoing on the ISS focused to validate assumptions 

supporting the RG theory. 

DEvice for the Study of Critical LIquids and Crystallization Alice Like Insert 

(DECLIC-ALI)

NASA/CNES is studying the equilibration near the liquid gas critical point in 

microgravity utilizing the ALI of the DECLIC facility (Pont, 2011). The DECLICALI will operate a number of experimental sequences throughout 2013. The U.S. 

objectives for this project are: to study the temperature and/or density equilibration 

behavior near the critical point in both the single and two-phase regions; to 

compare the temperature and density relaxation measurements with theoretical 

Figure 4.3.1. Picture of DEvice for the Study of 

Critical LIquids and Crystallization. (Source: Centre 

National d’Etudes Spatiales/NASA)

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modeling predictions; to determine the coexistence curve of the sample fluid 

near the critical point; to determine the thermal diffusivity from the relaxation 

measurements; and compare the results with theoretical predictions.

The DECLIC facility is a joint Centre National d’Etudes Spatiales (CNES) NASA 

ISS research program. DECLIC uses the EXpedite the PRocessing of Experiments 

to the Space Station (EXPRESS) rack standard infrastructure. The ALI portion 

accommodates two fluid cells each filled with 0.6 cc of SF6 (Tc = 45.5 degC, 

Pc = 3.7 MPa, Pc = 0.742 g/cc) at the near critical density. The direct observation 

cell allows measurement of optical transmission, 90-degree scattering, that can give 

small angle light scattering pictures and transmit images with shadowgraphy. The 

second cell, interferometric observation cell, has an optical window and a mirror 

coating to measure interferograms using Twyman-Green Interferometry. It has four 

thermometers and two pressure sensors. The data sampling rates for temperature 

and pressure are at up to 2 kHz. The thermometers can be configured as heating 

elements also. The body of the two cells is made of copper alloy and the optical 

windows are all sapphire except for a 90-degree scattering window made of fused 

Silica. The modular sample cells are integrated within the ALI. The temperaturecontrol stability of the ALI is better than 10 μK.

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This section describes the recommended fundamental physical science program 

to support the top four priorities of the 2011 Decadal Review. A critical element 

needed for successful accomplishment of the decadal priorities is sponsorship of a 

broad ground-based research program to nurture and develop the next generation 

flight experiments. The discussion focuses on facilities and experiments that can be 

developed in each priority area. A simple timeline is implied for each area by the 

order in which the experiments are described. The ultimate selection of what and 

when experiments are developed rests with NASA Headquarters through their peer 

review selection processes.

Complex Fluids and Soft Matter

The decadal review recommendations in this thrust area encompasses a broad 

program of which dusty plasmas is one element that is under consideration for 

the future ISS utilization. When it is realized for the implementation, the NASA 

Research Announcements (NRA) process would be used to select flight and 

ground-based investigators every three years throughout the life of the program.

Dusty Plasma Physics Facility (DPPF)

To initiate a sustaining program in the dusty 

plasmas area in the U.S., a unique U.S. DPPF 

needs to be developed. The DPPF will employ a 

different design than those of current European 

instruments to allow study of different 

kinds of science. For example, to study the 

transition from 3-D to 2-D physics, one of the 

manipulation capabilities on the first scientific 

payload will be temperature control of the 

electrodes to apply a desired thermophoretic 

force. By increasing the temperature gradient 

in the chamber, an experimenter will be able 

to progressively flatten a suspension of dust 

particles. To study nonlinear synchronization, 

another manipulation capability will be 

electrodes to drive waves that can be imaged 

with cameras. The cameras will be configured differently to allow stereoscopic 

imaging. This will allow an identification of the theoretically predicted, weak forces 

associated with wakefields. The DPPF configuration will be different from those 

Recommended Future 

Research Program

Fig. 5.1.1 Cross-sectional image of a suspension 

of polymer microspheres in a dusty plasma in a 

European Space Agency parabolic flight. (Arp, 

Goree and Piel PRE 2012). Features include a 

void that is due to a weak force called the ‘ion 

drag force,’ which is approximately one-tenth as 

strong as gravity under 1g conditions, wavefronts 

for a compressional sound wave, and small chains 

of microspheres that suggest a weak attractive 

force. (Source: J. Goree)

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of PK-4 and PlasmaLab, which are designed to investigate other questions such 

as the effects of strong ion flows (PK-4) and observation of critical phenomena 

(PlasmaLab). The DPPF will be designed as a modular facility using EXPRESS rack 

lockers, allowing deployment of new instruments simply by exchanging out one 

or two lockers in the facility. The DPPF will be designed to operate autonomously 

with limited crew intervention. 

It is envisioned that a total of four different instrument payloads will be flown 

in the DPPF. To generate a broad community of NASA researchers in this 

field, the NRA process would be used to select between 6 to 10 ground based 

investigators every three years, for a total of 10 flight investigators to complete 

their investigations on the ISS using the four different DPPF instrument inserts. 

Candidate examples of investigations include: 

• Search for the predicted weak attractive forces between two dust particles in 

addition to the strong repulsive electric force.

• Study the transition between 2-D and 3-D physics using temperaturecontrolled electrodes.

• Study nonlinear dynamics of large plasmas.

• Perform an elegant test of the fluctuation theorem.

Fundamental Forces and Symmetries

The gravitational interaction is by far the weakest of the four known fundamental 

forces of nature. Yet, by virtue of its universal attraction it is the dominant force at 

long ranges and plays a central role in both forming the structure and governing 

the motion of planets, stars, galaxies, and exotic objects such as neutron stars and 

black holes. Gravity also gives “shape” to the universe itself and guides its dynamical 

evolution. The geometry of spatial relations among objects and the timekeeping 

of our most precise atomic clocks are intimately tied to the properties of the 

gravitational field(s). It is important to know if Einstein’s tensor field of gravity is 

acting alone in establishing nature’s arena or if other fields such as the scalar field 

also contribute to this function. And if there are other new long-range, very weakly 

coupled force fields still to be found, their slight modifications of the apparent 

gravitational interaction and its consequent effects on the orbits of celestial bodies, 

clocks, rulers, and other experimental devices, will be one of the most likely routes 

to the discovery of “new physics.”

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To generate a broad community of NASA researchers in this field, the NRA process 

is employed and the selection of between 6 to 10 ground-based investigators occurs 

every three years for the approximate 15-year life of the program. In addition, flight 

investigators will be selected every three years for the investigations described in the 

following paragraphs.

Quantum Tests of Equivalence Principle and Space-Time (QTEST)

EEP is one of the most fundamental physics 

laws to be tested. This is not only because it is 

one of the pillars of modern physics, but also 

because a breakdown of any modern physic’s 

law or symmetry often implies a breakdown in 

EEP. QTEST is essentially the same concept of 

QUITE and QWEP, that is, two different lasercooled atomic species will be used as free-fall test 

masses, and atom interferometry will be used for 

differential acceleration measurements. 

There have been significant advancements in 

experiment design, technological development and 

science analysis since the QUITE proposal many years ago. Continuous academic 

research has resulted in new and improved approaches to atom interferometry. 

The atom interferometer technology and many of its critical components have also 

significantly matured. There is also a new understanding of the associated physics and 

interpretation of the measurements. In particular, emphasis is now focusing on the 

quantum matter wave aspect of the EEP test. In this context, the experiment is not 

just testing two falling objects, but two quantum wave functions. The physics and 

phenomena of the matter wave under gravity are subjects of discussion and debate. It 

is a quite intriguing possibility that such an experimental test system may provide a 

means to probe the connection between the quantum system and gravity.

To achieve this goal, a Large Momentum Transfer atom interferometer will be used 

for the QTEST approach. It will use two rubidium isotopes to provide the needed 

symmetry in the highly precise differential measurements. Dual ultra-cold atom 

sources will be used as well since a majority of the systematic errors can be reduced 

by using colder and smaller atomic clouds. Symmetric Bloch diffraction will be used 

to form and complete the atom interferometer sequence to improve the symmetry of 

the measurement system and reduce potential systematic errors.

Figure 5.2.1. Concept of the Quantum Tests 

of Equivalence Principle and Space-Time. 

(Source: H. Mueller)

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The autonomous QTEST payload would be located in the Active Rack Isolation 

Systems (ARIS) rack near the center of the ISS structure. This location would 

provide a reduced acceleration environment especially at lower frequencies. Other 

environment control implementation would be included within the payload. 

Microgravity Facility for Optical Reference Comb Experiments in Space 

(MicrogFORCES)

Precision measurements require ultrastable frequency reference sources and a 

benign laboratory environment. Space 

provides a very pristine environment 

for performing ultra-high precision 

measurements. In addition, a spacebased platform can provide access 

to large variations of gravity-related 

accelerations, the void of space, and 

global Earth coverage. These attributes 

make the ISS an ideal platform for 

fundamental physics tests and highprecision global measurements and services. A microgFORCES on the ISS would 

allow groundbreaking investigations in fundamental physics. microgFORCES 

would also be an ideal platform to demonstrate new high-impact technologies and 

to provide global metrology services. The ISS envisioned payload would consist 

of a self-referenced optical frequency comb that is stabilized to a set of extremely 

stable optical reference cavities and referenced to a trapped ion atomic clock. 

The key science and technology objectives of microgFORCES facility are: 1) to 

demonstrate a stabilized optical reference in space at a 10-16 level; 2) to perform 

the fundamental physics tests of Lorentz symmetry in a migrogravity environment 

with the anticipated goal of improving current correlation by two orders of 

magnitude; and 3) to establish an ISS capability to enable high performance global 

clock comparisons and time transfer. This facility could also provide an opportunity 

for U.S. scientists to collaborate with the ISS planned ESA SOC project. 

Collaboration would provide an opportunity for maturing and validating a number 

of high-precision measurement techniques that are of great interest to NASA and 

the Department of Defense.

Figure 5.2.2. Microgravity Facility for Optical Reference 

Comb Experiments in Space uses a combination of highly 

stabilized resonator cavities and a compact atomic clock 

linked by a self-referenced frequency comb. (Source: 

Folkner et al, NASA’s Jet Propulsion Laboratory)

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Space Optical Clock (SOC) NASA Sub-system

U.S. researchers possess the expertise required for many of the SOC sub-systems 

planned by ESA for development and operation on the ISS. A NASA contribution 

could elevate NASA to a near-equal partner to ESA in this ambitious scientific 

pursuit of testing the range of validity of Einstein’s theories of relativity and would 

allow U.S. scientists to be participants in the discovery of any transformational 

changes to the collective “view the world” that may come about because of 

measurements taken in space. NASA could play a key role with ESA by developing 

the stabilized clock laser and the optical link portions of this experiment. Additional 

recommended NASA contributions are for the development of an optical frequency 

comb or one or both of the atom interferometer physics packages.

Quantum Weak Equivalence Principle (QWEP) NASA Sub-system

In the budget-constrained environment, it would be beneficial for NASA to 

collaborate with ESA on the planned QWEP project. ESA would benefit from the 

ability to coordinate with the leading expertise in the U.S. in atom interferometer 

development, and U.S. scientists would be able to achieve nearly all of the planned 

science objectives of QTEST. Such a partnership could include NASA developing 

a major subsystem for the ESA QWEP project as well as jointly participating in the 

QWEP investigations and resulting science data analysis and interpretation.

Relativistic Gravity Experiment At L2 (REGAL2)

The REGAL2 will perform a precise test of many of the laws of fundamental physics 

through measuring the different time dilations of high-precision clocks located in 

the weak gravity environment near the Earth-Moon L2 and on Earth. The key 

technologies required for REGAL2 are essential for future plans to develop optical 

communication capability in space. Through gravitational time dilation, a clock 

located at a significant distance from a massive body, like the Earth, runs faster than 

one located within the gravitational environment of the Earth. In low-Earth orbit, 

the gravitational potential is reduced by a few percent as compared to the Earth. At 

the L2, approximately 300,000 km from Earth, the gravity potential is essentially 

zero. This difference will allow for improved tests of Einstein’s predictions. This 

experiment could improve the precision accuracy of current Einstein’s gravitational 

redshift measurements by a factor of more than 1,000 and would enable a highprecision test of Einstein’s equivalence principle. Any confirmed violation would be 

a major scientific discovery. REGAL2 is envisioned to consist of an optical atomic 

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34

clock accurate to a few parts in 1017 and a frequency-stabilized laser as the optical 

local oscillator. The clock would be referenced to an atomic frequency based on 

trapped and laser-cooled atomic species. The experiment would also feature a laser 

transponder to provide a high-performance frequency link to a second precision 

clock located on the ground. The key technologies required for REGAL2 are also 

essential for future plans to develop optical communication in space. A synergistic 

development of this technology may be undertaken with this endeavor.

Quantum Gases

It is important to look at the tiny 

building blocks of matter and how 

they manifest the fundamental laws 

of physics. Atoms are the smallest 

systems available for study of many 

of the basic principles of the universe 

in a laboratory setting. New study 

techniques allow the use of laser light 

to cool and probe the properties of 

individual atoms as a starting point. 

By carefully working with individual atoms, one can observe the smallest pieces of 

matter leading to a better understanding of the complex behavior of large systems. 

Furthermore, conducting these types of experiments in space allows us to remove 

the variables associated with the influence of gravity and manipulate matter freely 

without having to counteract the accelerations associated with specimens “falling” 

within the experimental devices. By observing the behavior of atoms completely 

under the experimenter’s control, one has the opportunity to explore experimental 

regimes that could lead to new insights and perhaps unexpected observations. 

Experimentation in a microgravity environment allows the study of clouds of atoms 

cooled by laser light to very near absolute zero, freely floating without the forces 

that would contain them on Earth. Further, the ISS microgravity environment will 

allow for longer observation times and higher precision measurements of an atom 

nearly at rest. 

NASA recognizes the unique features of the ISS microgravity research environment. 

To capitalize on this opportunity and provide the opportunity to the broad science 

community to engage and take advantage of the new capability, NASA plans to 

develop a state-of-the-art, ultra cold atom laboratory ISS facility. To engage academic 

Figure 5.3. Cloud of atoms are controlled against gravity (left) 

and allowed to freely expand (right). (Source: R. Thompson, 

NASA’s Jet Propulsion Laboratory)

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scientists, the competitive NRA will be employed. To generate a broader interest and 

invite more creative ideas, the NRA will solicit flight and ground research proposals. 

Currently, two rounds of CAL-related NRA competitions are planned. 

Cold Atom Laboratory 2 (CAL2)

NASA planning includes the future upgrade of the CAL facility design. The CAL2 

design upgrade would provide a more flexible and capable facility for studying atom 

interference with the quantum gases.

The combined objectives of CAL and CAL2 are to provide the capability to perform 

science related to cold atoms and a technology maturation path to dedicated cold 

atom experiments such as QTEST. To address cold atom science, the facility will 

provide various types of bosons, various types of fermions, and also interactions 

between bosons and fermions at high resolution. In the case of bosons, one can 

study the competition between long-range spatial order commensurate with the 

optical lattice and order in momentum space as in a Bose–Einstein condensate. In 

the case of cold fermions, the possibility for pairing and the conditions under which 

superfluidity can occur in the presence of an optical lattice are possible investigation 

topics. Fermions in optical lattices, which interact via repulsive interactions, are 

expected to show a very rich phase diagram in the microgravity environment. 

While similar phenomena occur in crystalline materials where the electrons of the 

solid experience the periodic lattice of the crystalline arrangements of the ions, the 

studies of systems of such ultra cold atoms in optical lattices offer unprecedented 

control of the microscopic parameters. When combined with quantum simulations, 

the opportunity is provided to test the theoretical framework and understanding 

of a very broad range of phenomena. The marriage of quantum degenerate 

fermions with BECs promises exciting discoveries about basic quantum mechanical 

interactions ranging from extremely weak to quite strong correlations. The noninteracting limit can be used to refine the understanding of the implications of the 

Pauli exclusion principle. The mixture of quantum degenerate fermions with BECs 

may also demonstrate effects similar to those in the strongly interacting 4He–3He 

liquid. Studies of the effects of interaction based spatial phase separations will 

yield a more complete level of understanding and lead to improved experimental 

technique to increase the understanding of quantum degenerate systems. 

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36

Macro Mechanical Quantum System Experiments

The ISS offers the 

opportunity for 

investigations of 

micromechanical 

quantum systems. 

Ground based laboratory 

approaches have 

demonstrated the ability 

to cool micromechanical 

systems to the regime 

where the quantum 

phenomena can be 

observed. A macroscopic quantum system can also be used for studying quantum 

phenomena at the boundary between the microscopic and atomic scale world 

in which quantum physics dominate. In addition, several researchers have 

hypothesized that gravity may play an important role through gravity-induced 

quantum decoherence. Study of such systems in a microgravity environment 

provides the opportunity to improve our understanding of gravity and quantum 

systems and clarify the links between them.

Micromechanical quantum systems have been usefully demonstrated in optomechanic resonators where interaction with light is used for bringing the system 

down to extremely low temperature and for detection of small motions of the 

mechanical system. Using opto-mechanically-coupled quantum systems in the 

microgravity environment of space will enable observation of the coupling between 

gravity and macroscopic particles (approximately 1,010 atoms) acting as quantum 

systems. Experiments in space can also test the physics of entanglement and 

decoherence over long baselines in an almost dissipation-free environment. 

Matter Near Critical Phase Transitions

The condensed-matter state is prevalent everywhere we look in the universe. 

While most of the volume of the universe is nearly an absolute vacuum, this vast 

expanse of space is punctuated with dense matter at many length scales, from the 

sun and our solar system to galaxies and galactic clusters. Human access to the 

space environment offers a unique opportunity to enhance our understanding 

of principles responsible for formation of the condensed matter state. The space 

Figure 5.3.2 Optical bench for the proposed DECoherence In Double-Slit 

Experiments. (Source: NASA’s Jet Propulsion Laboratory).

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environment is required when the experimental region of interest cannot be 

reached in ground-based studies, or gravity-related accelerations cause sample 

inhomogeneity that will reduce the resolution in ground-based experiments by 

orders of magnitude. Investigations related to this research topic will concentrate 

on exploring model systems possessing extraordinary properties such as liquid-gas 

phase transition.

DECLIC-ALI-R and DECLIC ALI-2

Results from the currently operating ISS 

DECLIC-ALI investigation indicate that the 

critical density was missed by about two percent 

because of the inability to adjust the fluid 

content in orbit. To fully meet the proposed 

CNES/NASA investigations on DECLICALI, a refurbished cell can be developed 

(ALI-R) to ensure that the critical density 

can be reached. This represents a low-cost, 

high pay-off investigation. To take advantage 

of the full capability of the DECLIC facility 

to perform critical phenomena experiments, 

a new instrument, DECLIC-ALI-2, can be 

developed. This instrument can be designed to 

address questions raised by current DECLICALI and ALI-R investigations or could be used 

to investigate topics such as finite size effects, 

dynamical effects and/or heat transfer effects 

near the critical point.

Figure.5.4.1. Pictured is a DEvice for the Study of 

Critical LIquids and Crystallization Alice Like Insert 

sample cell. (Source: Y. Garrabos) 

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38

Experiments conducted on the ISS require an understanding of natural and 

induced environments present. These environments include microgravity, vibration, 

radiation, vacuum, and thermal extremes. Depending on the particular experiment, 

each of the environments must be considered in the design of the experiment. 

Section 7 provides a general summary of the microgravity, vibration and radiation 

environments an experimenter will encounter on the ISS. Vacuum and thermal 

environments are dependent upon the location of the experiment. Internally 

mounted experiments within the pressurized volume of the ISS will experience 

very controlled pressure and temperature environments. However, experiments 

mounted externally will be subject to the low-Earth orbit, vacuum environment 

and to thermal cycles associated with each orbital pass around the earth. ISS offers 

several external locations on U.S., Japanese and European sites for the mounting 

of unpressurized experiments. Each of the locations provide different opportunities 

to take advantage of the natural environments present for fundamental physics 

research and intermediate disciplines.

Lessons Learned

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The ISS provides world-class facilities for in-orbit research. This section provides 

a brief summary about U.S. and foreign facilities available. Research facilities are 

located internally and externally providing access to all low-Earth-orbit environments 

for experimentation. More complete ISS research facilities information is available at 

the NASA website http://www.nasa.gov/mission_pages/station/research/experiments.

U.S. Experiment Support Facilities 

The internal pressurized U.S. laboratory facilities of potential interest for experiments 

related to fundamental include the FIR, the Combustion Integrated Rack, the 

Material Science Research Rack (MSRR), Microgravity Acceleration Measurements 

System (MAMS), Space Acceleration Measurement System (SAMS) the Window 

Observational Research Facility, and the Microgravity Science Glovebox (MSG). 

In addition, the ISS features eight EXPRESS racks that feature a standard design 

architecture and outfitting scheme to allow for ease of experiment integration. In 

ISS Facilities and How 

to Use Them 

Figure 7.1.1. U.S. International Space Station Internal facilities available for in-orbit research. (Source: NASA)

CGBA

MAMS

SAMS

ExPRESS Rack (1-8) MSRR

MSG

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40

conjunction with the internal facilities, there are multiple external Express Logistics 

Carrier (ELC) experiment site locations available. External experiment design 

requirements are unique to each site location and need to be considered as a part of 

the experiment design. 

ESA and Japanese Aerospace Exploration Agency (JAXA) 

Research Support Facilities

ESA and JAXA facilities that are available for fundamental physics research 

include the Fluid Science Lab (FSL), the European Drawer Rack (EDR), the 

Ryutal (Fluids) rack, the 

Kobairo (Gradient Heating 

Furnace), the Multipurpose 

Small Payload Rack (MSPR), 

the Space Environment 

Data Acquisition facility, 

and the Superconducting 

Submillimeter-wave LimbEmission Sounder. ESA and 

JAXA also provide external 

mounting locations for 

unpressurized payloads.

Figure 7.1.2. U.S. External facilities available for in-orbit research 

(several palates are available with multiple experiment sites/pallet). 

Credit: NASA)

ELC (1-5)

Ryutai FSL

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Figure 7.2.1. The European Space Agency and Japanese Aerospace Exploration Agency ISS internal facilities for in-orbit 

research. (Source: JAXA/ESA)

MSPR

Figure 7.2.2. The European Space Agency’s 

external facilities for in-orbit research. (Source: ESA)

Figure 7.2.3. Japanese Experiment Module - External Facility 

and the Experiment Logistics Module - Exposed Section. 

(Source: JAXA)

Kobairo

EDR

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42

Conducting an Experiment on the ISS: Review of the Unique 

Conditions of ISS

Environmental Conditions on the ISS: Microgravity

 The ISS orbit has a normal 450 km altitude and 51.6 degree inclination. One 

orbital period around the Earth is approximately 90 minutes. In Earth orbit, the 

microgravity environment is attributed to the ISS free-fall condition with all parts 

of the ISS continuously falling together through space as it orbits the Earth. The 

term microgravity (μg) is used to describe the space environment because absolute 

zero gravity (g) is not achievable in practice. An orbiting ISS experiences both 

atmospheric drag and solar radiation pressure. These forces produce the effect of 

small gravity equivalent accelerations and push heavier objects toward the front 

end of the moving ISS. If the ISS is rotated 

for a docking maneuver for example, small 

centrifugal forces can also be created. Tidal 

forces, also called gravity gradient forces, are 

present in the orbiting ISS because of small 

differences in the forces of gravity over the 

extended object. The presence of the small 

tidal forces has been demonstrated through 

in-orbit inspection of a spherical bubble. 

The shape of a spherical bubble is elongated 

toward and away from the direction to the 

Developing and Flying 

Research to ISS

Figure 8.1. The International Space Station U.S. Lab’s interior (initial ISS laboratory installation and in operation). 

(Source: NASA)

Figure 8.1.1 The chart shows altitude of the 

International Space Station orbit variation over a year. 

(Source: NASA’s Jet Propulsion Laboratory)

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Earth. In the orbiting ISS, these small effects are reduced to the level of a 10-6 g. 

Within a small region, very near the center of mass of the spacecraft, a level of 10-7 g 

can be achieved.

Environmental Conditions on the ISS: Vibration

The vibration environment of an in-orbit spacecraft can be broken into three main 

regimes: quasi-steady, vibratory, and transient. For instance, the ISS definition for 

quasi-steady vibrations includes disturbances at frequencies below 0.01 Hz. The 

sources of the disturbances are atmospheric drag, gravity gradient and rotational 

effects. The quasi-steady acceleration environment of ISS is less than 1 μg rms as 

averaged through the entire frequency range up to 0.01 Hz. The ISS requirements 

specify minimum time intervals of 30 continuous days of “microgravity mode” 

operation, with cumulative time of not less than 180 days per year. 

The vibratory regime is in the frequency range of 0.01 to 300 Hz. Typical sources of 

the disturbance are routine crew activity, thruster firings, fans, and pumps. The ISS 

requirements on the vibratory acceleration limits are defined over a set of frequency 

intervals. In the low-frequency regime (f < 0.1 Hz), the limit is less than 1.6 μg. In 

frequency range, 0.1 Hz < f < 100 Hz, the limit is less than 1.6 μg. The acceleration 

limit is less than 1,600 μg in the frequency range between 100 Hz and 300 Hz. The 

transient disturbances are of relatively short duration and are identifiable events. 

Examples of transient events are docking, operation of airlock valves and routing 

maintenance. The transient acceleration limits of ISS are an instantaneous limit of 

1,000 μg, and an integrated impulse limit of 10 μg-sec per axis over any 10 second 

interval. The actual vibration environment of the ISS has been monitored under 

the NASA Glenn acceleration measurement program (http://microgravity.grc.nasa.

gov). It is important to point out that the ISS vibration level is much worse than 

levels that can be easily achieved in a laboratory on the ground. Extra care has to 

be given when one designs a space experiment requiring more stringent vibration 

requirements. Recognizing this concern, the ISS provides accommodations for 

experiments sensitive to vibration disturbances. For vibration-sensitive experiments, 

ISS offers an ARIS. The ARIS facility provides the ability to predict and prevent 

the potential impacting effects of ISS-induced vibrations on experiments mounted 

within the ARIS rack. Stringent in-orbit tests of ARIS determined that sensitive 

experiments installed within an ARIS rack would be isolated and protected from 

vibration and acceleration related motions.

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44

Environment Conditions on the ISS: Radiation Environment

There are three major sources of charged particles in the ISS space environment: 

galactic cosmic rays, solar energetic particles and trapped particles in the Van Allen 

Belt. Galactic cosmic rays are generally isotropic with energies up to hundreds of 

gigaelectronvolts. Solar energetic particles or solar particle events are names for 

this very energetic process. These terms are also used to describe the potentially 

damaging situation that occurs when very strong magnetic fields in the solar 

photosphere reach a critical instability. A third term used in a similar manner is 

a solar proton event since protons are the most abundant comprising more than 

90 percent of the subatomic particles. For the typical ISS low-Earth orbit, these 

solar particles are shielded by the Earth’s magnetic field and are of limited concern. 

However, should a major solar particle event occur, crew procedures are in place 

to mitigate associated risks. Trapped particles relevant to the ISS orbit are mostly 

protons. The main problems associated 

with the trapped particles is the 

electrostatic charging effects to the ISS 

when it passes through the auroral zone 

and “single event” upset phenomena 

that can impact electronic devices caused 

by a single passing energetic particle. 

The typical impacts of charged particles 

on experiments are noise pick-up in data 

acquisition electronics and/or direct 

heating effects impacting heat sensitive 

measurements. NASA is prepared to 

provide experiment design guidance to 

limit either or both of these issues. 

On account of the orbital inclination of the ISS, it passes through the South 

Atlantic Anomaly (SAA) on a routine basis. The SAA contains a large flux of 

protons because of the off-axis, off-centered magnetic field of the Earth. It is 

expected that 50 percent of ISS orbits will pass through the SAA. The proton dose 

rates experienced during an orbital pass through the SAA exceed 10 protons/cm2sec 

for approximately 10 minutes of the 90-minute orbit.

Figure 8.1.2. Trapped proton flux map at 380 km. 

(Source: SPENVIS)

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Supporting research in science and technology is an important part of NASA’s 

overall mission. NASA solicits research through the release of NASA Research 

Announcements (NRA), which cover a wide range of scientific disciplines. All NRA 

solicitations are facilitated through the web-based NASA Solicitation and Proposal 

Integrated Review and Evaluation System (NSPIRES) http://nspires.nasaprs.com/

external/. Registering with NSPIRES allows investigators to stay informed of newly 

released NRAs and enables submission of proposals. NSPIRES supports the entire 

lifecycle of NASA research solicitations and awards, from the release of new research 

calls through the peer review and selection process. 

In planning the scope of their proposal, investigators should be aware of available 

resources and the general direction guiding NASA research selection. NASA places 

high priority on recommendations from the 2011 National Research Council’s 

NRC Decadal Survey, which placed emphasis on hypothesis-driven spaceflight 

research. In addition, principal investigators (PI) should be aware that spaceflight 

experiments may be limited by a combination of power, crew time, or volume 

constraints. Launch and/or landing scrubs are not uncommon, and alternative 

implementation scenarios should be considered in order to reduce the risk from these 

scrubs. Preliminary investigations using ground-based simulators may be necessary 

to optimize procedures before spaceflight. Also, many experiments require unique 

hardware to meet the needs of the spaceflight experiment. To understand previous 

spaceflight studies, prospective PIs should familiarize themselves with the NASA ISS 

Program Science Office database, which discusses research previously conducted on 

the ISS, including that of the International Partners. A detailed catalog of previous, 

current, and proposed experiments, facilities, and results, including investigator 

information, research summaries, operations, hardware information, and related 

publications is available at www.nasa.gov/iss-science through the NASA ISS Program 

Office. Additionally, details pertaining to research previously supported by the Space 

Life and Physical Sciences Research and Applications Division of NASA’s Human 

Exploration and Operations Mission Directorate can be located in the Space Life 

& Physical Sciences Research and Applications Division Task Book in a searchable 

online database format at: https://taskbook.nasaprs.com/Publication/welcome.cfm. 

What Should Principal 

Investigators Know About 

Conducting Research on 

the ISS?

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46

S.G. Turyshev, U.E. Israelsson, M. Shao, N. Yu, A. Kusenko, E. Wright, C.W.F. 

Everitt, M. Kasevich, J. A. Lipa, J. C. Mester, R. D. Reasenberg, R. L. Walsworth, 

N. Ashby, H. Gould, H. Paik, Int. J. Modern Phys. D 16(12a), 1879-1925 (2007).

C. J. Takacs, A. Vailati, R. Cerbino, S. Mazzoni, M. Giglio, and D. S. Cannell, 

Phys. Rev. Lett. 106, 244502 (2011).

A. Vailati, R. Cerbino, S. Mazzoni, C. J. Takacs, D.S. Cannell, M. Giglio, 

Nature Communications 2:290 doi: 10.1038/ncomms1290 (2011).

Bin Liu, J. Goree, V.E. Fortov, A.M. Lipaev, V.I. Molotkov, O.F. Petrov, 

G.E. Morfill, H.M. Thomas, H. Rothermel, and A.V. Ivlev, Physics of Plasmas16, 

083703 (2009).

Bin Liu, J. Goree, V. E. Fortov, A. M. Lipaev, V. I. Molotkov, O. F. Petrov, 

G. E. Morfill, H. M. Thomas, and A. V. Ivlev , Physics of Plasmas 17, 053701 

(2010).

M. Barmatz, Inseob Hahn, J. A. Lipa, and R. V. Duncan, Reviews of Modern 

Physics, 79, 1 (2007).

J.A. Lipa, D.R. Swanson. J.A. Nissen, T.C.P. Chui, and U.E. Israelsson, Phys. Rev. 

Lett. 76, 944 (1996).

Hacene Boukari, Robert L. Pego, and Robert W. Gammon, Phys. Rev. E 52, 

1614-1626 (1995).

Berg, R.F.; Moldover, M.R.; and Zimmerli, G.A., Phys. Rev. Lett., 82, 920-923, 

(1999).

Berg, R. F.; Moldover, M. R.; Yao, M.; Zimmerli, G. A., Phys. Rev. E., 77, 

041116-1-041116-23 (2008).

J. A. Lipa, D. R. Swanson, J. A. Nissen, Z. K. Geng, P. R. Williamson, 

D. A. Stricker, T. C. P. Chui, U. E. Israelsson, and M. Larson, Phys. Rev. Lett. 84, 

4894 (2000).

G. Pont, S. Barde, D. Blonde, B. Zappoli, Y. Garrabos, C. Lecoutre, D. Beysens, 

M. Hicks, U. Hegde, I. Hahn, N. Bergeon, B. Billia, N. Mangelinck-Noël, 

A. Ramirez, R. Trivedi, conference proceedings, 62nd International Astronautical 

Congress, Cape Town, SA (2011).

Citations

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ACES Atomic Clock Ensemble in Space

AMS Alpha Magnetic Spectrometer

ARIS Active Rack Isolation System

BEC Bose-Einstein Condensate

CAL Cold Atom Laboratory

CAL2 Cold Atom Laboratory 2

CHeX Confined Helium Experiment

CLASS Condensate Laboratory Aboard the ISS 

CNES Centre National d’Etudes Spatiales

CVX Critical Viscosity Experiment

DECLIC-ALI Device for the Study of Critical Liquids and Crystallization Alice Like Insert

DPPF Dusty Plasma Physics Facility

EDR European Drawer Rack

EEP Einstein’s Equivalence Principle

ELC Express Logistics Carrier

ESA European Space Agency

EXPRESS Expedite the Processing of Experiments to the Space Station

FIR Fluid Integrated Rack

FSL Fluid Science Lab

GRADFLEX Gradient Driven Fluctuations Experiment

ISS International Space Station

JAXA Japan Aerospace Exploration Agency

JEM-EF Japanese Experiment Module – Exposed Facility

JPL NASA’s Jet Propulsion Laboratory

LPE Lambda Point Experiment

LTMPF Low Temperature Microgravity Physics Facility

MAMS Microgravity Acceleration Measurements System

MSG Microgravity Science Glovebox

MSPR Multipurpose Small Payload Rack

MSRR Material Science Research Rack

NASA National Aeronautics and Space Administration

NIST National Institute of Standards and Technology

NRA NASA Research Announcements

PARCS Primary Atomic Reference Clock in Space

QTEST Quantum Tests of Equivalence Principle and Space-Time

QUITE Quantum Interferometer Test of Equivalence

QWEP Quantum Weak Equivalence Principle

RACE Rubidium Atomic Clock Experiments

REGAL2 Relativistic Gravity Experiment At L2

RG Renormalization Group

SAA South Atlantic Anomaly

SAMS Space Acceleration Measurement System

SOC Space Optical Clock

VOC Volatile Organic Compounds

ZENO Critical Fluid Light-Scattering Equipment

Acronyms

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48

The Complete ISS Researcher’s 

Guide Series

1. Acceleration Environment

2. Cellular Biology

3. Combustion Science

4. Earth Observations

5. Fluid Physics

6. Fruit Fly Research

7. Fundamental Physics

8. Human Research

9. Macromolecular Crystal Growth

10. Microbial Research

11. Microgravity Materials Research

12. Plant Science

13. Rodent Research

14. Space Environmental Effects

15. Technology Demonstration

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For more information...

Space Station Science

http://www.nasa.gov/iss-science

Facilities

http://www.nasa.gov/mission_pages/station/research/

facilities_category.html

ISS Interactive Reference Guide:

http://www.nasa.gov/externalflash/ISSRG/index.htm

Researchers/Opportunities

http://www.nasa.gov/mission_pages/station/research/

ops/research_information.html

ISS Research Customer Helpline

JSC-ISS-research-helpline@mail.nasa.gov

281-244-6187

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50

National Aeronautics and Space Administration

Johnson Space Center

http://www.nasa.gov/centers/johnson

www.nasa.gov

NP-2015-04-021-JSC 

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