The Lunar University Network for Astrophysics Research (LUNAR), is a team of researchers and students at leading universities, NASA centers, and federal research laboratories undertaking investigations aimed at using the Moon as a platform for space science. LUNAR research includes Lunar Interior Physics & Gravitation using Lunar Laser Ranging (LLR), Low Frequency Cosmology and Astrophysics (LFCA), Planetary Science and the Lunar Ionosphere, Radio Heliophysics, and Exploration Science. The LUNAR team is exploring technologies that are likely to have a dual purpose, serving both exploration and science. There is a certain degree of commonality in much of LUNAR’s research. Specifically, the technology development for a lunar radio telescope involves elements from LFCA, Heliophysics, Exploration Science, and Planetary Science; similarly the drilling technology developed for LLR applies broadly to both Exploration and Lunar Science.

Lunar Laser Ranging
LUNAR has developed a concept for the next generation of Lunar Laser Ranging (LLR) retroreflector. To date, the use of the Apollo arrays continues to provide state-of-the-art science, over a lifetime of >40 yrs. This program has determined properties of the lunar interior, discovered the liquid core, which has now been confirmed by seismometry, and provided most of the best tests of General Relativity (GR). However, the single-shot ranging accuracy is now limited by the structure of the Apollo arrays. The next generation LLR program will provide lunar emplacements that will support an improvement in the ranging accuracy, and thus the lunar physics, by factors of 10-100.

Low Frequency Cosmology and Astrophysics (LFCA)
The focus of the LUNAR LFCA research is to strengthen the science case and develop relevant technologies related to tracking the transition of the intergalactic medium (IGM) from a neutral to ionized state during the time that the first stars and first accreting black holes were forming using the redshifted 21-cm signal from neutral hydrogen. The eventual goal is to exploit the “radio-quiet” properties of the Moon’s farside as the site for a lunar radio telescope to conduct these fundamental measurements.

Planetary Science connection to LFCA
The Scientific Context for the Exploration of the Moon (SCEM) identifies the “Lunar Environment,” particularly the fact that the lunar atmosphere presents the nearest example of a surface boundary exosphere, as one of four guiding themes for science-based exploration. From this theme, the report develops a set of science goals, including “Determine the global density, composition, and time variability of the fragile lunar atmosphere before it is perturbed by further human activity.” The SCEM report also notes that the Moon may continue to outgas and that the lunar atmosphere, as it is coupled to the solar wind, is a dynamic system. As such, long-term monitoring is required to understand its properties. Further, as a surface boundary exosphere, studies of the Moon are likely to inform processes occurring on Mercury, other moons, asteroids, and potentially even Kuiper Belt objects. LUNAR has developed a concept to measure the Moon’s ionospheric density using the plasma frequency cutoff from observations with low frequency dipole antennas on the lunar surface.

Radio Heliophysics
High-energy particle acceleration occurs in diverse astrophysical environments including the Sun and other stars, supernovae, black holes, and quasars. A fundamental problem is understanding the mechanisms and sites of this acceleration, in particular the roles of shock waves and magnetic reconnection. Within the inner heliosphere, solar flares and shocks driven by coronal mass ejections (CMEs) are efficient particle accelerators which can be readily studied by remote observations.Electron densities in the outer corona and inner heliosphere yield emission frequencies below ~10 MHz. Observations must be conducted from space because the terrestrial ionosphere is opaque in this frequency range, preventing any of this emission from reaching a receiver on Earth. Work on the Radio Observatory on the Lunar Surface for Solar Studies (ROLSS) concept has included refinement of instrument performance requirements, prototyping of critical components such as antennas and correlator electronics, and the use of simulations and observations from analogous instruments in space or radio arrays on Earth.

Exploration Science
The LUNAR team is investigating human missions to the lunar L2/Farside point that could be a proving ground for future expeditions to deep space while also overseeing scientifically important investigations. On an L2 mission, the astronauts would travel 15% farther from Earth than did the Apollo astronauts and spend almost three times longer in deep space. Such missions would validate the Orion Multi-Purpose Crew Vehicle’s life support systems for shorter durations, would demonstrate the high-speed reentry capability needed for return from deep space, and would measure astronauts’ radiation dose from cosmic rays and solar flares to verify that Orion provides sufficient protection. On such missions, the astronauts could teleoperate landers and rovers, which would obtain samples from the geologically interesting (and unexplored) farside (i.e., South Pole-Aitken Basin) and deploy a lunar radio telescope. Such telerobotic oversight would also demonstrate capability for future, more complex deep space missions.

Read the team summary report for years 1-3

A schematic view of the early Universe in the context of studying it using the 21-cm line of neutral hydrogen. The Universe evolves in time from left to right. The top panel shows the structures visible in neutral hydrogen, blue being cold gas, red being hot gas, with black regions either being ionized (no neutral hydrogen) or at the same temperature as the cosmic microwave background. The bottom panel shows how the mean temperature of the hydrogen, which we hope to measure using observatories at the Moon, changes with time, or, equivalently, redshift or the observed frequency of the redshifted 21-cm line. Major epochs are marked in the lower panel.

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