into the dark ages: a lunar-orbiting, low frequency...

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Jack Burns University of Colorado at Boulder Co-author: Joseph Lazio Naval Research Laboratory Into the Dark Ages: A Lunar-Orbiting, Low Frequency Antenna to Measure the Global Signatures of the First Collapsing Structures in the Early Universe The 21-cm hyperfine transition of hydrogen holds great promise for tracking the evolution of the Universe and constraining the birth of the first stars and black holes. We describe a single antenna experiment in lunar orbit that would be the first to observe the Universe during and after the “Dark Ages” when the Universe was < 1 billion yrs old. The all-sky hydrogen signal has predicted features at frequencies between 25 and 100 MHz that are characteristic of the expansion of the Universe and the ignition of stars and/or black holes. However, this portion of the radio spectrum is heavily contaminated by civil and military transmitters much stronger than the hydrogen signal. A single dipole antenna in lunar orbit, carried into the radio shielded zone above the farside, operating at 25–100 MHz has much potential for cosmological measurements. A stable broadband spectrometer with carefully controlled noise properties on the spacecraft bus will be required to carry out high dynamic range observations. Also required will be robust algorithms for removal of the Galactic foregrounds, which are being developed by ground-based experiments operating at higher frequencies. These data will be the first to produce measurements of the Universe’s reionization about 13 billion yrs ago.

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Jack Burns University of Colorado at Boulder Co-author: Joseph Lazio Naval Research Laboratory Into the Dark Ages: A Lunar-Orbiting, Low Frequency Antenna to Measure the Global Signatures of the First Collapsing Structures in the Early Universe The 21-cm hyperfine transition of hydrogen holds great promise for tracking the evolution of the Universe and constraining the birth of the first stars and black holes. We describe a single antenna experiment in lunar orbit that would be the first to observe the Universe during and after the “Dark Ages” when the Universe was < 1 billion yrs old. The all-sky hydrogen signal has predicted features at frequencies between 25 and 100 MHz that are characteristic of the expansion of the Universe and the ignition of stars and/or black holes. However, this portion of the radio spectrum is heavily contaminated by civil and military transmitters much stronger than the hydrogen signal. A single dipole antenna in lunar orbit, carried into the radio shielded zone above the farside, operating at 25–100 MHz has much potential for cosmological measurements. A stable broadband spectrometer with carefully controlled noise properties on the spacecraft bus will be required to carry out high dynamic range observations. Also required will be robust algorithms for removal of the Galactic foregrounds, which are being developed by ground-based experiments operating at higher frequencies. These data will be the first to produce measurements of the Universe’s reionization about 13 billion yrs ago.

William .M Farrell NASA/GSFC Co-Authors T. J. W. Lazio NRL, Washington DC Timothy J. Stubbs NASA/GSFC & UMBC R. J. MacDowall NASA/GSFC J. O. Burns U Colorado J. S. Halekas UC Berkeley, NLSI’s DREAM team and NLSI’s LUNAR team Lunar Environmental Effects and Astrophysical Platforms The Moon provides a natural platform for astrophysical observatories, and the advantages for radio observatories are especially great. On the lunar farside, the Moon blocks terrestrial man-made noise, thus providing a low-noise broadband radio environment from below 10 MHz to 100 MHz for study of the Dark Ages period, extra-solar planet radio emission, and other highly desirable RF targets. While there are definite advantages, any object on the lunar surface is exposed directly to the harsh surrounding environment. For example, unlike terrestrial radio systems, any lunar radio system is immersed in a conducting gas and thus is directly connected to the lunar plasma environment. NASA’s Lunar Science Institute has a team that studies the lunar environment (DREAM) and another who considers the placement of astrophysical RF platforms on the Moon (LUNAR), and we are engaging in a combined study to better understand the impact the harsh lunar environment may have on such platforms. Conversely, we also find that those same RF platforms can be used to better-quantify the character of the lunar environment, such as in unique studies of the lunar plasma sheaths and ionosphere via RF cutoffs, and any environmental effort should examine knowledge flow in both directions.

Matthew Benjamin University of Colorado at Boulder Co-authors: Jack Burns University of Colorado at Boulder Joseph Lazio Naval Research Laboratory Douglas Currie University of Maryland at College Park Douglas Duncan University of Colorado at Boulder Justin Kasper Harvard-Smithsonian Astrophysical Observatory Robert MacDowall Goddard Space Flight Center The NLSI LUNAR (Lunar University Network for Astrophysics Research)

Team – Accomplishments from the First Year This poster focuses on the accomplishments during the first year of the NLSI Lunar University Network for Astrophysics Research (LUNAR) team. The Moon is a unique platform for fundamental astrophysical measurements of gravitation, the Sun, and the Universe. Lunar Laser Ranging of the Earth-Moon distance provides extremely high precision constraints on General Relativity and alternative models of gravity. Accomplishments in the first year included improvements in the sensitivity of lunar laser ranging of the moon and development of the next generation of corner cube reflectors. We constructed new models of the radio signals expected from an early epoch of the Universe during and following the “Dark Ages”, developed observational techniques aimed at observing the early universe in low radio frequencies, and further characterized the lunar radio frequency interference (RFI) environment. We also began the modeling and testing of materials and technology for this low frequency radio array. We conducted a graduate level “Lunar Science Seminar”, and we developed various education and public outreach events on lunar science including a planetarium show aimed at K-5 students.

Peter C. Chen Lightweight Telescopes, NASA GSFC Co-authors: Michael E. Van Steenberg* NASA GSFC Paul D. Lowman NASA Goddard Space Flight Center Ronald J. Oliversen NASA Goddard Space Flight center

Fun With Lunar Regolith Simulants

We report on a new class of materials that shows promise as a building block for infrastructures and instrument support on the Moon, and may enable future large astrophysical observatories on the Moon and in space. We have found that, by combining lunar regolith simulants with polymer binders and special additives, a substance is made that is demonstrably harder than cement but has in addition many useful physical and chemical properties. The fabrication process is simple, does not require water, and can take place under lunar conditions of vacuum and radiation. Investigations are currently under way to study how the properties of this ‘lunar cement’ can be quantified and optimized by changing the proportions of the ingredients and measuring the corresponding changes in physical properties (Young’s modulus, Poisson ratio, shear modulus, ultimate tensile strength, etc). Potential applications include structures to protect humans and equipment from space radiation and meteor impact, solar power arrays, energy storage, very large telescopes on the Moon and in space, dust repellent surfaces, helium 3 extraction, and others.

*deceased

This work is supported under grant NNA09DB30A from LUNAR, a consortium of research institutions led by the U. of Colorado, Dr. J. Burns, PI.

Peter C. Chen Lightweight Telescopes, NASA GSFC Co-authors: Michael E. Van Steenberg* NASA GSFC Co-authors: Douglas M. Rabin NASA Goddard Space Flight Center Ronald J. Oliversen NASA Goddard Space Flight Center

A Scalable Superconductor Bearing System for Lunar Telescopes and Instruments

We report on a new design for pointing and tracking telescopes and instruments on the Moon. Lunar telescopes require bearing and drive systems that can move and follow targets very precisely under cryogenic conditions, over long time periods, preferably with no maintenance, and preferably do not fail with loss of power. HTS bearings, consisting of permanent magnets and bulk superconductors, are well suited to the task. The components do not make physical contact; hence there is no friction and no wear. The levitation is passive and stable; no power is required to maintain position. We report on the design and laboratory demonstration of a prototype two-axis telescope mount. Unlike previous designs, this new configuration is simple and easy to implement. Most importantly, it can be scaled to accommodate instruments ranging in size from decimeters (laser communication systems) to meters (solar panels, communication dishes, optical telescopes, optical interferometers) to decameters and beyond (VLA-type radio interferometer elements).

*deceased

This work is supported under grant NNA09DB30A from the Lunar University Network for Astrophysics Research (LUNAR), a consortium of research institutions led by the University of Colorado, Dr. J. Burns, PI.

Paul Lowman NASA Goddard Space Flight Center Co-authors: Peter C. Chen Lightweight Telescopes, NASA GSFC

Comparative Scientific Value of Manned Missions to the Moon and to an Asteroid

It has been proposed to make the first manned mission outside LEO a rendezvous with an asteroid. This paper argues that the feasibility and scientific value of a new lunar mission is greater than that of an asteroid mission. An asteroid mission would encounter the problem of high-energy, high-Z cosmic rays, for which shielding would be prohibitive. Also, samples from an asteroid would probably prove to be like meteorites already in collections. The lunar surface in contrast provides abundant shielding material, and potentially valuable resources such as helium 3. Astronomy from the Moon was proven feasible by the Apollo 16 UV telescope, and a radio astronomy satellite (Explorer 49). Furthermore, there are many unsolved scientific questions about the Moon itself, some with major implications for the geologic history of the Earth. For example, better knowledge of the impact cratering rate of the Moon would increase our ability of predict catastrophic impacts on the Earth. It is concluded that although an asteroid mission would be valuable, a new lunar program would be even more so.

This work is supported under grant NNA09DB30A from LUNAR, a consortium of research institutions led by the University of Colorado, Dr. J. Burns, PI.

Peter C. Chen Lightweight Telescopes, Inc. and Code 671, NASA GSFC Co-authors: Yong-Chun Zheng National Astronomical Observatories, Chinese Academy of Sciences, Beijing, China

From the Moon to Mars and Beyond

We report on an ongoing study on how a moonbase – either human attended or robotically operated – can provide vital support and make possible manned missions to Mars and Jupiter and beyond. It is well known that, on voyages beyond the Earth’s protective magnetosphere, high energy radiation from galactic and solar sources pose serious health hazards and can be fatal to the crew. Providing the requisite shielding via launches from Earth and/or assembly in space are many orders of magnitude beyond the capability of chemical rockets. The long travel times to outer planets also compound the hazard. We suggest that resources and conditions on the Moon can be used to advantage to overcome these problems. We report on the status of a study on the feasibility of using CAS-1, a lunar regolith simulant developed by the Chinese Academy of Sciences, to design radiation shielding for spacecraft. The shielding technique, in combination with recent advances in the fields of Earth-based remote mining and mass rapid transportation, can be enabling factors for human exploration of the outer planets.

This work is supported under grant NNA09DB30A to P. Chen from LUNAR, a consortium of research institutions led by the University of Colorado, Dr. J. Burns, PI

Douglas Currie University of Maryland Co Author Kris Zacny Honeybee Robotics

Regolith Drilling for the Lunar Laser Ranging Retroreflector Array for the 21st Century

The Lunar Laser Ranging Retroreflector Array for the 21st Century (LLRRA-21) in combination with a Lunar Laser Ranging (LLR) program within the International Laser Ranging Service (ILRS) should provide extensive new information on the lunar interior, General Relativity and cosmology. Since Apollo, the ground stations improved the ranging accuracy by 200x and now the Apollo arrays provide a significant limitation of the LRR accuracy. While the LLRRA-21 can provide 100x improvement, the ultimate accuracy will require drilling to a depth of 1m and anchoring the Cube Corner Retroreflectors (CCR).

Drilling beyond 1m was achieved during Apollo 15-17 and Soviet Luna 24 missions, though this was not trivial. To achieve the required depth, Honeybee has developed the pneumatic drilling procedure. This novel design allows the CCR to be deployed from a small lander or a rover. The CCR with its deployment system would weigh only a few kilograms and use a few Watts of power during deployment. The required push force, a significant limitation on the low gravity Moon, would be virtually zero.

A demonstration of this pneumatic drilling with a CCR will be available at the Ames Regolith Facility.

D. L. Jones JPL/Caltech Loss in Transmission Lines from Low Frequency Lunar Array Dipoles A number of lunar-based low frequency radio array concepts have been studied during the past few years, motivated by the potential value of sensitive observations of neutral Hydrogen at tens of MHz for studies of the cosmic Dark Ages. One concept involves large numbers of dipole antennas connected to central station hubs via balanced parallel-conductor transmission lines. Since the distance from an individual antenna and a station hub could be many tens of meters, loss in the transmission line is a significant issue. This poster presents the results of numerical calculations of transmission line loss under a range of assumptions, and demonstrates that reasonable values are possible at the lowest frequencies (< 10 MHz). At higher frequencies, ohmic loss in small conductors is a serious problem. This suggests that using conductor material that is superconducting at lunar night temperatures would be highly beneficial, and may be enabling. This work was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. The LUNAR consortium is funded by the NASA Lunar Science Institute (via Cooperative Agreement NNA09DB30A) to investigate concepts for astrophysical observatories on the Moon.

Doug Duncan University of Colorado Co Authors Jack Burns University of Colorado Matt Benjamin University of Colorado EPO Activities of the Lunar University Network for Astrophysics Research

(LUNAR) This poster will show the E/PO work done on behalf of LUNAR. We are producing a planetarium program for elementary age children and families, in both English and Spanish, called "Max Goes to the Moon.” The plot of the show is based on the award-winning book of the same name. Max, a real dog belonging to author and scriptwriter Jeff Bennett, helps communicate to children the story line of tangible preparations needed for going to the Moon. Moon phases and basic ideas about science are taught along the way. Our E/PO plan includes developing and implementing teacher workshops, and we are doing this in conjunction with the national Astronomical Society of the Pacific meeting. Low cost “Galileoscopes” are given to every participating teacher for lunar observations. We hosted public events and lectures that highlight and enhance general awareness of lunar science. For the LCROSS impact we held a “Lunar Bagel Breakfast” that attracted more than 400 people and made NBC news. An “Interdisciplinary Lunar Science Seminar” taught at the graduate level by NLSI PI’s Jack Burns, Mihaly Horanyi, and Bill Bottke featured presentations by faculty members, or reviews of published papers by graduate students. Topics included those studied by the three Boulder-based NLSI teams.

Steven Furlanetto University of California at Los Angeles Co Authors Andrei Mesinger Renyue Cen Oral

21cmFAST: Predictions for a Low-Frequency Radio Telescope from the Moon

A future low-frequency radio telescope on the far side of the moon promises to revolutionize our understanding of the first phases of galaxy formation in our Universe: by measuring the brightness of the hyperfine line of neutral hydrogen (with a rest wavelength of 21 cm), it can teach us about the appearance of the first stars, galaxies, and black holes. Here we describe a new tool to predict this rich signal using only modest computational resources. We include all relevant physical processes, including the ultraviolet, ionizing, and X-ray backgrounds, and the code produces detailed maps of the signal accurate on scales of a few arc-minutes. The results provide a crucial input in planning such a telescope for the moon.

Lauren Holzbauer Co Author Steven Furlanetto University of California at Los Angeles

View From the Moon: Signatures of the Lyman-Werner and Lyman-alpha Radiation Backgrounds from the First Stars

We have developed a new method for calculating the power spectra of the Lyman-Werner (LW) and Lyman-alpha (Lya) backgrounds at high redshift. At these early epochs the radiation backgrounds are symptoms of a universe newly lit with its first (Population III) stars that have formed in dark matter halos. LW photons (11.5-13.6eV) are of particular interest due to their culpability in the dissociation of molecular hydrogen. The Lya background sets the spin temperature of the neutral gas in the intergalactic medium (IGM); inhomogeneities in the temperature imprint fluctuations on the 21-cm signal. By superimposing a flux profile on all halos harboring PopIII stars and using the halo model to obtain the spatial distribution of halos, we can efficiently calculate power spectra for the radiation backgrounds. We have found that the shape of the LW power is identically set at all redshifts by a distinct turnover on the scale corresponding to the distance at which the LW flux profile terminates (~ 100cMpc). These signatures could be seen with a view from the moon; a future telescope on the lunar surface would allow observation of the 21-cm signal unimpeded by the Earth's atmosphere. Such unprecedented data could reveal when the first luminous sources formed and when re-ionization commenced.

Geraint Harker University of Colorado at Boulder Co-authors: Jack Burns University of Colorado at Boulder Judd Bowman California Institute of Technology Probing the cosmic dark ages with a low-frequency radio antenna in lunar

orbit Abstract: A low-frequency radio antenna on the far side of the Moon, or in lunar orbit, may allow detection of redshifted 21-cm absorption and emission from the cosmic dark ages and the epoch of reionization, and lead to constraints on cosmology and on the first sources of radiation in the Universe. I will argue why it is attractive, and probably necessary, to place the antenna on or near the Moon rather than on the Earth. One challenge facing such an experiment is the intense foregrounds originating from our Galaxy and from extragalactic sources, which place very stringent requirements on the capabilities of the instrument and the data analysis. I will show the results of our program to model the observations of a lunar-orbiting low-frequency dipole experiment and to extract a simulated 21-cm signal from them. I will also discuss the possibility of using the Moon itself as a calibration source. The concept of this experiment is similar to that of a higher-frequency experiment, EDGES, being conducted from the Earth. I will show how the extension to low frequencies enabled by an experiment in lunar orbit makes the extraction of a signal more tractable, and may greatly enhance the scientific potential of such an experiment.

Laura Kruger University of Colorado Boulder Co-Authors Jack Burns University of Colorado Ricardo Alfaro University of Colorado Francesca Lettang University of Colorado Exploration of the Dark Ages: An investigation into Kapton’s suitability as a radio telescope material We present the first results from our study of the effects that harsh lunar conditions may have on a polyimide film (Kapton). The NLSI LUNAR (Lunar University Network for Astrophysics Research) team is proposing to use this film as the backbone for a revolutionary low frequency radio antenna array (<100 MHz). We intend this array to observe the “Dark Ages” and the Epoch of Reionization in the early universe (<1 billion years after the Big Bang), the period when observable structures are just beginning to collapse. We have designed a series of experiments to investigate the change in the Kapton’s properties, especially electrical conductivity and tensile strength. The film was placed in a vacuum chamber under high vacuum (10-6 Torr) and thermally cycled every 24 hours for a month between the temperature extremes of -150˚C and 100˚C. The film was also exposed to UV light (120-160 nm) during the hot cycle to mimic solar intensity. Additionally, we simulated the film’s travel and deployment by wrapping the Kapton around a rod and remotely unrolling it under vacuum at -150˚C. We will continue our study by using heaters embedded in the film to emulate the future metallic dipoles, transmission lines, and electronics in the array.

Joseph Lazio Naval Research Laboratory Co Authors Jack Burns University of Colorado

From the Lunar Ionosphere to the First Stars The modern Universe is nearly fully ionized – even in our own solar system, most of the mass is in the Sun, which is a ball of ionized hydrogen. However, for about 1 billion years after the Big Bang, the temperature was cool enough the hydrogen was neutral. One of the key challenges in modern astrophysics is to understand the timing and cause(s) of this transition from neutral to ionized state, known as the Epoch of Reionization. The NLSI LUNAR team mission includes using the Moon as a platform for studying the Universe. We will motivate how a Lunar Radio Array, emplaced on the far side of the moon, would be an impressive instrument for studying the first stars, the Epoch of Reionization, and even the time before the first stars, known as the cosmic Dark Ages. Before the LRA, there will likely be a series of scientific and technological pathfinders. We will outline a roadmap, starting from small instrument packages, conducting both science from the Moon and science of the Moon, to the full LRA.

Bennett Maruca Harvard University Co Authors Justin Kasper Smithsonian Astrophysical Observatory Robert MacDowall NASA Goddard Space Flight Center Milan Maksimovic Paris Observatory, France

Searching for Extra-Solar Bursts of Decameter Radiation Terrestrial low-frequency arrays operating in the decameter band (3 MHz - 30 MHz) have been used to detect radio bursts from various sources in the Solar System and to map the diffuse emission of the Milky Way. However, due to limited baseline lengths and the distorting effects of Earth's ionosphere, discrete extra-solar sources have never been observed in this band. We explore potential sources of radio bursts at these frequencies (including Sagittarius A*, gamma-ray bursts, and brown dwarfs) and the feasibility of detecting such events from the lunar surface. Additionally, we present results from our ongoing work with the STEREO/WAVES radio receivers. Both STEREO spacecraft orbit the Sun at a distance of about 1 AU. By considering radio observations from the spacecraft together, an effective baseline of up to about 2 AU is achieved. A given radio burst is observed at slightly different times at the spacecraft depending on their relative orientation to the source and the type of emission mechanism. We demonstrate how this has already allowed us to not only identify bursts from different sources within the Solar System (including Earth, the Sun, and Jupiter), but to also distinguish beamed radiation from diffuse emission.

Jordan Mirocha University of Colorado at Boulder Co-authors: Jack Burns University of Colorado at Boulder Eric Hallman Harvard-Smithsonian Center for Astrophysics John Wise Princeton University Steven Furlanetto University of California at Los Angeles

Cosmological Numerical Simulations of X-ray Heating During the Universe’s “Dark Ages”: Predictions for Observations with a Lunar

Farside Radio Telescope

Due to its tenuous ionosphere and shielding from terrestrial radio interference, the lunar farside is a unique platform for astrophysical research of the very early universe. In particular, the highly redshifted 21cm line of neutral hydrogen contains a wealth of information about the universe’s first stars, galaxies, and black holes. In the last decade, it has been shown that early X-rays are likely the dominant source of heating during the cosmic “Dark Ages” and early Reionization epochs, a time less than one billion years after the Big Bang when the universe began its transition from mostly neutral to almost entirely ionized. These X-rays, produced primarily by accretion onto the first black holes, propagate deeply into the intergalactic medium (IGM) and are expected to drive the global 21cm signal into emission. However, the predictions for this signal are highly uncertain since constraints on the formation and growth histories of the first black holes are limited. Using new high mass resolution cosmological simulations with radiative transfer, we are exploring the effects of an early X-ray background on the 21cm signal. Future tomography of the 21cm signal will place constraints on the accretion history of super-massive black holes and their impact on the IGM.

Tom Murphy

The Lunokhod 1 reflector and what it means for lunar ranging After almost forty years of silence, the reflector on the Lunokhod 1 rover has been found. Imaging by the LRO spacecraft revealed the location of the rover, which allowed the APOLLO (Apache Point Observatory Lunar Laser-ranging Operation) team to narrow their search and quickly find a laser return from the long-lost reflector. The initial return was almost as bright as that from the large Apollo 15 reflector. The twin reflector on Lunokhod 2 was once consistently 25% stronger than the Apollo 15 reflector, but is now ten times worse than Apollo 15. The relative brightness of the Lunokhod 1 reflector adds a twist to the unfolding mystery of the lunar reflector degradation. The location of Lunokhod 1 makes it the most valuable of the five reflectors as a sensitive probe of lunar orientation. Accurate measurement of lunar orientation is crucial for converting reflector measurements into knowledge of the path of the moon's center of mass, which is of fundamental importance in testing general relativity. Likewise, a precision determination of lunar orientation is key to understanding the structure and composition of the lunar interior. Because its return is bright, the Lunokhod 1 reflector will contribute substantially to the science deliverables of modern lunar laser ranging.

K. P. Stewart Co Authors B. C. Hicks N. Paravastu R. MacDowall D. Jones C. Gross J. Lazio K. W. Weiler

Numerical Simulations of the Lunar Polymide Film Antennas The Moon has been identified as a unique platform for both cosmological and solar observations at low frequencies. Science antennas constructed of metal dipoles deposited on thin dielectric film substrates would have the advantages of convenient packaging and easy deployment on the lunar surface. Dielectric sheets, e.g., 25-μm thick polymide, 1 to 2 m wide and up to several hundred meters long, deposited with an array of dozens of adjacent antennas could be rolled up for transport. We report numerical simulations of the electromagnetic properties (gain, response pattern, and feedpoint impedance) of antenna designs that would be useful for solar radio studies at frequencies around 10 MHz and cosmology investigations at frequencies around 100 MHz. We have considered a range of lunar regolith properties. Feedpoint impedance measurements with a thin-film dipole placed on dry, sandy soil, and on asphalt give excellent agreement with numerical simulations.

Richard Miller University of Alabama in Huntsville Co-authors: Massamiliano Bonamente University of Alabama in Huntsville Riley Freelove University of Alabama in Huntsville Sue O'Brien University of Alabama in Huntsville, William S. Paciesas University of Alabama in Huntsville David J. Lawrence Johns Hopkins Applied Physics Laboratory John Goldsten Johns Hopkins Applied Physics Laboratory Alex Harwit Ball Aerospace Dennis Ebbets Ball Aerospace C. Alex Young ADNET Systems, NASA/GSFC

The Lunar Occultation Observer: A New Paradigm for Nuclear Astrophysics

The Lunar Occultation Observer (LOCO) is a new γ-ray astrophysics mission concept having unprecedented sensitivity in the nuclear regime (~0.1-10 MeV). LOCO will perform an all-sky survey of the Cosmos at nuclear energies, and will have the capability to address multiple high priority science goals. Placed into lunar orbit, LOCO will utilize the Moon's unique environment to maximize performance relative to terrestrial endeavors. Specifically, LOCO will use the Moon to occult astrophysical sources as they rise and set along the lunar limb. The encoded temporal modulation will then be used to image the sky thereby enabling spectroscopic, time-variability, point- & extended-source analyses.

This Lunar Occultation Technique (LOT) enables the excellent flux sensitivity, position, and energy resolution required of the next-generation nuclear astrophysics mission. In addition, occultation imaging eliminates the need for complex, position sensitive detectors. The LOCO concept is cost effective, and has a relatively straightforward and scalable implementation appropriate for an Explorer-class mission. The top-level mission concept will be reviewed, provide a status report for detector development and mission planning, and outline science return estimates.

Richard Miller University of Alabama in Huntsville Co-authors: Riley Freelove University of Alabama in Huntsville David J. Lawrence Johns Hopkins Applied Physics Laboratory, USA John Goldsten Johns Hopkins Applied Physics Laboratory, USA Alex Harwit Ball Aerospace, USA High-Resolution Gamma-Ray Spectroscopy with Silicon Photomultipliers in Support of the Lunar Occultation Observer (LOCO) Mission Concept

The long-term goal of our program is the development of the Lunar Occultation Observer (LOCO), a next-generation mission capable of surveying the Cosmos in the nuclear regime (~0.1-10 MeV). In support of this mission, as well as other secondary nuclear physics applications in planetary exploration and national security, we are developing an inorganic-scintillator spectrometer module based on next-generation silicon photomultiplier technologies. Silicon photomultipliers (SPM) represent a viable alternative to PMTs. An operational and effective silicon photomultiplier is an enabling technology offering a number of key features that will positively impact space-based applications including: ruggedness, compactness, low power operation, and insensitivity to magnetic fields. This effort - supported in part by LUNAR, a NASA Lunar Science Institute - leverages existing detailed modeling efforts, initial feasibility tests, preliminary performance testing, and industrial partnerships. We will present the current status of module development, outline the roadmap for raising the TRL, and review design and performance tradeoffs.