Identifying hidden nuclear material in orbit from its own neutron spectrum
Abstract
The Outer Space Treaty bans nuclear weapons from orbit but lacks a dedicated means of verifying what a closed spacecraft contains. The orbital environment supplies a natural interrogation field: trapped protons induce neutron emission, allowing passive inspection without an active source. Detection can flag an anomalous object from kilometre standoff, but a count does not determine composition. Here we construct a conventional aluminium spacecraft and a uranium-bearing object with nearly identical detector-accepted neutron counts, whose reconstructed spectra remain distinct. In the baseline geometry the full spectrum reaches an area under the receiver-operating characteristic of 0.90 after about 70 accepted neutrons. A tungsten configuration matched to the uranium count rate preserves only about 2.2 per cent of the per-neutron spectral separation, raising the requirement to about 3200 neutrons for discrimination and 8200 for 90 per cent power at 5 per cent false attribution against that alternative. Under a published detector-rate benchmark, ten inspectors at 500 m require about one week for discrimination and less than three weeks for controlled attribution. These thresholds define an inspection claim envelope: detection, discrimination and attribution are distinct measurements with distinct range-dwell regimes. The environment supplies the interrogation; proximity determines what may responsibly be claimed.
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BibTeX
@misc{maghrbi2026identifying,
title = {{Identifying hidden nuclear material in orbit from its own neutron spectrum}},
author = {Yasser Maghrbi},
howpublished = {HAL},
year = {2026},
month = sep,
url = {https://hal.science/hal-05713434v2},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Identifying hidden nuclear material in orbit from its own neutron spectrum
AU - Yasser Maghrbi
PY - 2026
DA - 2026/09/21
PB - HAL
UR - https://hal.science/hal-05713434v2
AB - The Outer Space Treaty bans nuclear weapons from orbit but lacks a dedicated means of verifying what a closed spacecraft contains. The orbital environment supplies a natural interrogation field: trapped protons induce neutron emission, allowing passive inspection without an active source. Detection can flag an anomalous object from kilometre standoff, but a count does not determine composition. Here we construct a conventional aluminium spacecraft and a uranium-bearing object with nearly identical detector-accepted neutron counts, whose reconstructed spectra remain distinct. In the baseline geometry the full spectrum reaches an area under the receiver-operating characteristic of 0.90 after about 70 accepted neutrons. A tungsten configuration matched to the uranium count rate preserves only about 2.2 per cent of the per-neutron spectral separation, raising the requirement to about 3200 neutrons for discrimination and 8200 for 90 per cent power at 5 per cent false attribution against that alternative. Under a published detector-rate benchmark, ten inspectors at 500 m require about one week for discrimination and less than three weeks for controlled attribution. These thresholds define an inspection claim envelope: detection, discrimination and attribution are distinct measurements with distinct range-dwell regimes. The environment supplies the interrogation; proximity determines what may responsibly be claimed.
ER -