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DN-012 L: In situ lunar surface radiation environment measurements and space weather monitoring

Long-term radiation measurements at the South Pole surface: charged particles from solar events and cosmic rays, and the neutrons the regolith gives off, measured up to at least 100 MeV. Lunar and other space neutron measurements have so far stopped at 20 MeV, yet "the energy region between 1 MeV – 1 GeV accounts for most of the neutron induced cancer risk". Regolith neutrons "may contribute as much as ~30% of effective dose" on surface missions, and the models are unvalidated. It is named in the Moon Base Users Guide (near-term), under the long-duration challenge (Data gaps spreadsheet, DN-012 L; Users Guide, p. 12).

Quotations below are from row DN-012 L of the data gaps spreadsheet unless marked otherwise. ADD Rev C's Appendix E prints the same record as a table, and it matches the row field for field (ADD Rev C, p. 276).

Description

"Measure the radiation environment on the lunar surface at the south pole. Measurements should include flux and energy spectra of electrons, protons, and heavy-ions from solar particle events and galactic cosmic rays, and secondary or albedo neutrons generated by interactions of energetic particles with the lunar regolith. Neutron spectrum measurements inside a lunar lander or habitat or on the surface of the moon are needed to validate models used in the assessment crew radiation exposure. Long-term measurements are needed to capture variations when the Moon is exposed to the solar wind, within Earth's magnetotail, and during dynamic space weather conditions."

Need driver and data type

  • Need driver: Lunar Surface Natural Environment Characterization
  • Data type: In Situ Monitoring

Target measurement parameters

"Measure neutron flux spectrum up to at least 100 MeV. Measure charged particle (electron, proton, heavy- ion) flux and energy spectra at the same time."

Current state of data

"Current estimates of the lunar radiation environment are from orbital satellite data, modeling, and limited in-situ surface measurements with temporal and spatial limitations. A limited number of neutron flux measurements have been made on the Lunar surface or by devices in Lunar orbit, but the energy range for these measurements did not exceed 20 MeV. Neutron flux spectrum measurements have also been made on ISS, during Mars transit, and on the surface of Mars, but the energy range for these measurements was also limited to neutrons below 20 MeV. Models that have not been validated with space measurements for neutrons greater than 20 MeV are currently used to predict crew radiation exposure. The energy region between 1 MeV – 1 GeV accounts for most of the neutron induced cancer risk, and validation of model calculations over just the low energy region provides little information on model accuracy at higher energies, because the physical processes producing higher energy particles differ from those producing lower energy particles. Note that while the LunaNet Interoperability Specifications (LNIS V.5) provides protocols for space weather monitoring/alert services, the sources of data to provide these alerts are not well-defined at present."

Impact if data is unavailable

"Data enables accurate characterization of the average and extreme radiation environments encountered by crew and surface systems. Neutrons produced in the Lunar regolith may contribute as much as ~30% of effective dose incurred by crew on surface missions, but models used to predict this environment have not been validated with surface measurements."

Benefits if data is available

"Long-term, in-situ radiation environment monitoring will improve the fidelity of radiation exposure assessments. Measurement data will be used to quantify the uncertainty in models that predict neutron environments, an important part of the crew exposure assessment and risk prediction process. Additionally, extending the neutron spectral measurements over longer periods of time may also contribute to several Moon to Mars science objectives."

Traceability

  • Objectives: HS-01 LM, AS-01 LM, TH-03 L, LI-09 L (codes as printed; the sheet gives no titles)
  • Segment: Human Lunar Return (HLR): "The M2M segment during which the data is needed, but not necessarily when it is collected" (Data gaps spreadsheet, Key sheet). A segment is not a Moon Base phase.

Priority

None. The spreadsheet has no priority field, and the Users Guide calls the data-gap list "not comprehensive or prioritized" (Users Guide, p. 11).

Moon Base relevance

The Users Guide names DN-012 L for one challenge (Users Guide, p. 12):

  • "Operating on the Lunar Surface for Long Durations" (headline challenge). Its knowledge challenge has two sentences: "Characterize the lunar surface environment to predict performance impacts and risks associated with long duration surface operations." and "Investigate dust mechanics, regolith geotechnical properties, and radiation/charged particle fluctuations, seasonal patterns, and scattering." The guide lists DN-008 L to DN-013 L, DN-015 L, DN-016 L and DN-019 L under both sentences together and does not say which sentence each serves. The challenge's technology half cites tech gaps #0101, #0201, #0301, #0801 and #0804.

The guide ties its challenges to "near-term Moon Base development efforts": missions in phase one "offer opportunities to collect data and mature technologies to enable essential phase two and phase three capabilities" (p. 11). See Technology and knowledge challenges.

Phase 1 mission on the same subject (the wiki's link; no source pairs them): MoonFall's instruments "will measure radiation levels" (Moon Base Phases, "MoonFall"). The gap asks for long-term surface monitoring; the page doesn't say how long MoonFall measures. See the data gaps index.

Sources

Data gaps spreadsheet, DN-012 L · Users Guide, pp. 11–12 · Moon Base Phases, "MoonFall" · ADD Rev C, p. 276