Analog Field Deployments

Neutron and gamma-ray spectrometers flown to the Moon and Mars measure hydrogen and elemental composition from orbit or from a rover deck. We take the same measurement techniques into the field on Earth, deploying portable neutron and gamma-ray detectors at planetary analog sites to test retrievals of soil moisture and hydration, validate our models against ground truth, and inform the design of future flight instruments. The same measurements also connect planetary science back to terrestrial hydrology, where cosmic-ray neutron sensing is an established tool for mapping soil moisture at the hectometer scale.

Paired cosmic-ray neutron sensors on tripods on the Alvord Playa, Oregon, with Steens Mountain in the background — Paired cosmic-ray neutron sensors deployed on the Alvord Playa, Oregon, during the August 2025 field campaign. Steens Mountain in the background.

The Instrument

Our field-portable cosmic-ray neutron sensor (CRNS) passively counts neutrons produced by galactic cosmic rays interacting with the ground. Because hydrogen is highly effective at moderating neutrons, the count rate is inversely related to the water content of the soil within a footprint of roughly 150 to 250 meters radius and a sensing depth of tens of centimeters. The system pairs a moderated detector (sensitive to epithermal neutrons) with a bare detector (sensitive to thermal neutrons), the same measurement principle used by orbital and landed planetary neutron spectrometers from Lunar Prospector and Mars Odyssey to the DAN instrument on the Curiosity rover.

The full system packs into two detector modules totaling about 23 kg, runs on internal batteries, and logs GPS, temperature, and pressure alongside the neutron data. For campaigns requiring air travel, we worked with Quaesta Instruments to build a smaller carry-on-portable version around He-3 proportional counters.

Field Campaigns

NASA MSFC Lunar Terrain Field, Alabama

June 2026

CRNS depth-sensitivity test at the regolith test field at NASA Marshall Space Flight Center, run alongside a joint neutron and seismic experiment campaign with NASA MSFC and partner institutions.

Namib Sand Sea, Gobabeb, Namibia

October 2025

A NASA-funded deployment based at the Gobabeb Namib Research Institute, carried out as part of the Dragonfly mission analog field campaign. We measured neutron count rates across a full dune profile (dune crest, slopes, base, and interdune) as a Mars dune analog for comparison with Mars Odyssey orbital and MSL DAN surface neutron data. The measurements resolved clear differences in near-surface moisture between geomorphic units of the sand sea, with interdune surfaces distinctly wetter than the extremely dry dune crests. Collaborators include BYU, the University of Idaho, the University of Nebraska-Lincoln, the Gobabeb Namib Research Institute, and the University of Basel.

Alvord Playa, Oregon

August 2025

Deployment on the Alvord Desert playa as part of a NASA PSTAR field campaign investigating habitable environments. Wet and dry playa sites showed clear contrast in neutron count rates and derived soil moisture, demonstrating the sensitivity of the technique across hydrologic gradients.

San Francisco Volcanic Field, Arizona

Published 2026

Radiochemical mapping of silicic-to-basaltic volcanic terrains with a portable gamma-ray and neutron detector, constraining Si, Fe, and Th abundances as a lunar analog study for discriminating volcanic lithologies, directly relevant to the Lunar-VISE investigation of the Gruithuisen Domes. Published as Ölçek et al. (2026) in Icarus.

Earlier Deployments

2022 – 2024

Jornada Experimental Range, New Mexico (July 2022): rover-integrated mobile CRNS surveys. Lake Pleasant, Arizona (May 2024): stationary soil-moisture calibration measurements.