Lunar HalO Orbiting Neutron Spectrometer (LOONS)
Abstract
The detection of fast neutrons is important in geospace, solar, and planetary physics. Galactic cosmic ray interactions with the Earth's atmosphere, other planetary atmospheres and the lunar surface produce secondary neutrons. These neutrons cover a broad range in energy and intensity that depend on the GCR intensity and the composition of the target, whether it is an atmosphere or regolith. Neutrons are also generated in solar flares. Identifying the sources and mechanisms of acceleration through direct measurements of solar neutrons will help to constrain current models of acceleration, ultimately improve our ability to forecast space weather, and potentially assess the impact that our young Sun (and other host stars) has on climate and the habitability of the Moon and Mars. Improved knowledge of atmospheric neutrons themselves, including spatial and temporal variations is important because neutron-induced single event upsets in avionics systems constitute a microelectronics reliability problem. Furthermore, neutrons are penetrating, dangerous and abundant, posing a health and safety risk for astronauts and aircraft personnel. Neutrons also constitute a major radiation background for other NASA assets in low-Earth orbit. Lunar outposts through such programs as Artemis and Lunar Gateway offer a new opportunity to study neutrons from several sources. The Lunar Gateway will be in a Near-Rectilinear Halo Orbit an ideal location for future neutron instrument to take unique measurements of neutrons of lunar, terrestrial and solar origin. Neutrons are ubiquitous products of nuclear interactions and thus, challenges the identification of their sources. Their charge-less nature complicates capturing the particle's full energy and direction of travel. Scintillator-based technologies have a proven record for detecting and measuring fast neutrons. They have high stopping power, good energy resolution, and fast timing properties. Modern readout devices such as silicon photomultipliers (SiPMs) offer an ideal alternative to photomultiplier tubes given their inherently compact size, fast response, and low operating voltages. We discuss a versatile neutron spectrometer concept, the Lunar HalO Orbiting Neutron Spectrometer (LOONS), based on arrays of scintillating blocks readout by SiPMs, that would measure fast neutrons at energies corresponding to the bulk of solar and magnetospheric neutrons.
- Publication:
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43rd COSPAR Scientific Assembly. Held 28 January - 4 February
- Pub Date:
- January 2021
- Bibcode:
- 2021cosp...43E.370D