SUPREME-QG: Space-borne Ultra-Precise Measurement of the Equivalence Principle Signature of Quantum Gravity

Selim Shahriar
Northwestern University, Evanston

Progress in physics has largely been driven by the development and verification of new theories that unify different fundamental forces of nature. For example, Maxwell revolutionized physics with his unified theory of electricity and magnetism, and the Standard Model of particle physics provides a consistent description of all fundamental forces (electromagnetic, strong, and weak) except for gravity. The major barrier to completing the quest for unification is that General Relativity (GR), the current theory of gravity, cannot be reconciled with QM. Theories of Quantum Gravity (TQG), which are yet untested, prescribe modifications of both GR and QM in a manner that makes them consistent with each other. Tests of TQG represent arguably the greatest challenge facing our understanding of the Universe. The most promising way to test TQG is to search for violation of the Equivalence Principle (EP), a fundamental tenet of GR which states that all objects experience the same acceleration in a gravitational field. Violation of EP is characterized by a nonzero Eotvos parameter, Eta, defined as the ratio of the relative acceleration to the mean acceleration experienced by two objects with different inertial masses in a gravitational field. EP violations at the level of Eta < 10^(-18) arise in many versions of TQG (e.g., string theory). The most precise test of the EP to date has been carried out under the space-borne MICROSCOPE experiment employing classical accelerometers, constraining the value of Eta to <1.5×10^(-15). We propose to investigate the use of a radically new method that leverages quantum entanglement to test the EP with extreme precision, at the level of Eta ~ 10^(-20), using a space-borne platform. This method is described in a recent paper by us (PRD 108, 024011, ’23). It makes use of simultaneous Schroedinger Cat (SC) state atom interferometers (AIs) with two isotopes of Rb. Consisting of N=10^6 atoms, the SC state, which is a maximally entangled quantum state generated via spin-squeezing of cold atoms in an optical cavity, acts as a single particle, in a superposition of two collective states, enhancing the sensitivity by a factor of ~root(N)=10^3. Such large-N SC states are difficult to create and have not been observed yet, let alone leveraged for precision metrology. In another recent paper, we described a novel protocol, namely the generalized echo squeezing protocol (GESP), to overcome the challenges of creating such a state (PRA 107, 032610, ’23). We will demonstrate the functionality of this method in a testbed to enable a follow-on space-borne mission capable of testing the EP at the level of Eta ~ 10^(-20). If EP violation is observed, the version of TQG that agrees most closely with the result would form the foundation for a complete theory governing the universe, including its birth: the Big Bang. A null result would force physicists to conceive an entirely new approach to addressing the irreconcilability of GR and QM, fundamentally altering the course of theoretical physics. Either outcome would represent one of the greatest developments in our quest for understanding nature. The SC-state AI (SCAI), also holds the promise of revolutionary improvements in the precision of gravitational cartography and inertial navigation, when configured for simultaneous accelerometry and rotation sensing. The sensitivity of such a sensor, for one second averaging time, would be ~0.9 femto-g for accelerometry, and ~0.5 pico-degree/hour for rotation sensing. This would represent an improvement by a factor of ~10^5 over the best conventional accelerometer, and a factor of ~10^4 over the best conventional gyroscopes. As such, the SCAI would find widespread usage in defense as well as non-defense sectors, including deep-space exploration, for inertial navigation. A space-borne SCAI would be able to carry out gravitational cartography with a resolution far greater than that achieved using the GRACE-FO satellites.

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Loura Hall

PULSAR: Planetary pULSe-tAkeR

Marco Quadrelli
NASA Jet Propulsion Laboratory

There is a strong coupling mechanism between the lithosphere, ionosphere, magnetosphere, atmosphere, and the plasmasphere of many planetary bodies. For example, the ionosphere has been shown to respond to space weather events induced by Solar activity, as well as to atmospheric events, and events in the surface and interior of a planet. PULSAR (Planetary pULSe-tAkeR) is a stable spacecraft constellation that enables large and reconfigurable detector baselines to sense a wide range of frequencies in this coupled domain, and distributed spatial and temporal measurements on a global scale, leading to new planetary science measurements. Like a doctor taking vitals and monitoring the health state of a patient, PULSAR literally “takes the pulse of the planet”.

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Loura Hall

Inflatable Starshade for Earthlike Exoplanets

John Mather
NASA Goddard Space Flight Center

We will design the first family of ISEE’s (Inflatable Starshade for Earthlike Exoplanets) with sizes from 35 to 100 m diameter. A starshade would enable any telescope to observe exoplanets, a top priority for astronomy worldwide. Compared with other starshade concepts, we aim for a lower mass, cost and complexity, while still providing high performance and science yield (>100 targets). Our starshades would be compatible with the 6 m diameter Habitable Worlds Observatory (HWO) now being planned, as well as the world’s largest telescope, the 39 m diameter European Extremely Large Telescope now being built in Chile, working as part of the HOEE, (Hybrid Observatory for Earthlike Exoplanets), and other future telescopes. We need to observe oxygen at visible wavelengths and ozone at UV.

An ISEE, positioned between a target star and the telescope, would block the starlight without blocking the exoplanets. Starshades have perfect optical efficiency, they work with any telescope, and they can block the starlight much better than the requirement, for a star >1010 times brighter than the target.

The competing technology uses a nearly perfect and perfectly stable space telescope like HWO, with an internal coronagraph, to keep the starlight away from the image of the planet. Coronagraphs have the key advantages that they are compact, testable, and have instant availability. However, tested coronagraphs have not yet met the contrast requirement. Moreover, there is no possibility of an ultraviolet coronagraph. If the extreme picometer stability and optical perfection requirements on HWO and its coronagraph could be relaxed by using it with a starshade, then HWO itself could be built at much lower cost and risk. If UV observations of exoplanets are essential, then a 35 m starshade with HWO is the only possible solution.

The HWO will be NASA’s next great observatory, and it will include a high performance coronagraph to observe exoplanets. This choice changed the landscape for the competing starshade technology. A starshade mission could still become necessary if: A. The HWO and its coronagraph cannot be built and tested as required; B. The HWO must observe exoplanets at UV wavelengths, or a 6 m HWO is not large enough to observe the desired targets; C. HWO does not achieve adequate performance after launch, and planned servicing and instrument replacement cannot be implemented; D. HWO observations show us that interesting exoplanets are rare, distant, or are hidden by thick dust clouds around the host star, or cannot be fully characterized by an upgraded HWO; or E. HWO observations show that the next step requires UV data, or a much larger telescope, beyond the capability of conceivable HWO coronagraph upgrades.

An inflatable starshade would overcome the main obstacle to starshades: their mechanical design. Starshades have never been flown, they have strict shape and edge requirements, and they must be propelled and precisely positioned. Prior designs based on discrete elements can be scaled up to the size required for HWO (35-60 m) and HOEE (100 m), but they are massive and hard to test leading to high cost and risk. Our mass budget aims for 250 kg for the 35 m HWO case, 650 kg for the 60 m case and 1700 kg for the 100 m HOEE case.We will extend our ideas and produce detailed designs and finite element models, suitable for strength, stiffness, stability, and thermal analysis. We will develop small-scale laboratory test equipment and verify solutions to issues like bonding large sheets of high-strength material into inflatable systems. Deliverable items would include mass/power budgets, strength and stiffness, and lab tests of critical items. We will update mission concepts for HWO and HOEE based on the starshade parameters.
Depending on progress with the HWO mission, starshades could be required to complete our knowledge of exoplanets. An inflatable starshade could make them possible.

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NASA Instrument on Firefly’s Blue Ghost Lander to Study Lunar Interior

LMS instrument aboard the Blue Ghost Lander heading to Mare Crisium in mid-January

As part of its Artemis campaign, NASA is developing a series of increasingly complex lunar deliveries and missions to ultimately build a sustained human presence at the Moon for decades to come. Through the agency’s CLPS (Commercial Lunar Payload Services) initiative, commercial provider Firefly’s Blue Ghost lander will head to the Moon’s Mare Crisium for a 14-day lunar lander mission, carrying NASA science and technology that will help understand the lunar subsurface in a previously unexplored location.

Developed by the Southwest Research Institute (SwRI), NASA’s Lunar Magnetotelluric Sounder (LMS) will probe the interior of the Moon to depths of up to 700 miles, two-thirds of the way to the lunar center. The measurements will shed light on the differentiation and thermal history of our Moon, a cornerstone to understanding the evolution of solid worlds.

Magnetotellurics uses natural variations in surface electric and magnetic fields to calculate how easily electricity flows in subsurface materials, which can reveal their composition and structure.

“For more than 50 years, scientists have used magnetotellurics on Earth for a wide variety of purposes, including to find oil, water, and geothermal and mineral resources, as well as to understand geologic processes such as the growth of continents,” said SwRI’s Dr. Robert Grimm, principal investigator of LMS. “The LMS instrument will be the first extraterrestrial application of magnetotellurics.”

Mare Crisium is an ancient, 350-mile-diameter impact basin that subsequently filled with lava, creating a dark spot visible on the Moon from Earth. Early astronomers who dubbed dark spots on the moon “maria,” Latin for seas, mistook them for actual seas.

Mare Crisium stands apart from the large, connected areas of dark lava to the west where most of the Apollo missions landed. These vast, linked lava plains are now thought to be compositionally and structurally different from the rest of the Moon. From this separate vantage point, LMS may provide the first geophysical measurements representative of most of the Moon.

The LMS instrument ejects cables with electrodes at 90-degree angles to each other and distances up to 60 feet. The instrument measures voltages across opposite pairs of electrodes, much like the probes of a conventional voltmeter. The magnetometer is deployed via an extendable mast to reduce interference from the lander. The magnetotelluric method reveals a vertical profile of the electrical conductivity, providing insight into the temperature and composition of the penetrated materials in the lunar interior.

“The five individual subsystems of LMS, together with connecting cables, weigh about 14 pounds and consume about 11 Watts of power,” Grimm said. “While stowed, each electrode is surrounded by a ‘yarn ball’ of cable, so the assembly is roughly spherical and the size of a softball.”

The LMS payload was funded and will be delivered to the lunar surface through NASA’s CLPS initiative. Southwest Research Institute based in San Antonio built the central electronics and leads the science investigation. NASA’s Goddard Space Flight Center in Greenbelt, Maryland, provided the LMS magnetometer to measure the magnetic fields, and Heliospace Corp. provided the electrodes used to measure the electrical fields.

Under the CLPS model, NASA is investing in commercial delivery services to the Moon to enable industry growth and support long-term lunar exploration. As a primary customer for CLPS deliveries, NASA aims to be one of many customers on future flights. NASA’s Marshall Space Flight Center in Huntsville, Alabama, manages the development of seven of the 10 CLPS payloads carried on Firefly’s Blue Ghost lunar lander.

Media Contact: Rani Gran
NASA’s Goddard Space Flight Center, Greenbelt, Maryland

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Rob Garner

New Jersey Students to Hear from NASA Astronauts Aboard Space Station

Students from the Toms River School District in New Jersey will have the chance to connect with NASA astronauts Don Pettit and Butch Wilmore as they answer  prerecorded science, technology, engineering, and mathematics (STEM) related questions from aboard the International Space Station.

Watch the 20-minute space-to-Earth call in collaboration with Science Friday at 10 a.m. EST on Tuesday, Jan. 14, on NASA+ and learn how to watch NASA content on various platforms, including social media.

Science Friday is a nonprofit dedicated to sharing science with the public through storytelling, educational programs, and connections with audiences. Middle school students will use their knowledge from the educational downlink to address environmental problems in their communities.

Media interested in covering the event must RSVP by 5 p.m., Friday, Jan. 10, to Santiago Florez at: sflorez@sciencefriday.com or 221-840-2244.

For more than 24 years, astronauts have continuously lived and worked aboard the space station, testing technologies, performing science, and developing skills needed to explore farther from Earth. Astronauts aboard the orbiting laboratory communicate with NASA’s Mission Control Center in Houston 24 hours a day through SCaN’s (Space Communications and Navigation) Near Space Network.

Important research and technology investigations taking place aboard the space station benefit people on Earth and lays the groundwork for other agency missions. As part of NASA’s Artemis campaign, the agency will send astronauts to the Moon to prepare for future human exploration of Mars; inspiring Artemis Generation explorers and ensuring the United States continues to lead in space exploration and discovery.

See videos and lesson plans highlighting space station research at:

https://www.nasa.gov/stemonstation

-end-

Abbey Donaldson
Headquarters, Washington
202-358-1600
Abbey.a.donaldson@nasa.gov

Sandra Jones 
Johnson Space Center, Houston
281-483-5111
sandra.p.jones@nasa.gov

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Abbey A. Donaldson