Development and Demonstration of a Buddy-Tag Prototype

Future nuclear arms-control agreements may place numerical limits on the total numberof warheads in the nuclear arsenals of states. Verifying these limits may require inspectors to account for individual warheads, both deployed and non-deployed. Typically, this task can be accomplishedwith unique identifiers, but standard tagging techniques may be unacceptable in this case due to host concerns about safety and intrusiveness. First proposed by Sandia National Laboratoriesin the 1990s, the “Buddy Tag” concept seeks to address these concerns by separating the tag from the treaty accountable item itself. Verification of the pairings between tags and accountable items would take place during a short-notice inspection, where the host would be required to produceone buddy tag for each item. A buddy tag has two key elements: a tamper-indicating enclosure and a motion-detection system designed to detect illicit movements in a stand-down period. As part of this project, we have built a full-up buddy-tag prototype for demonstration and evaluation purposes.This paper reviews the design choices and functionalities of the different subsystems, both for the enclosure and for the motion-detection system. We pursue a modular approach for the tag’s hardware, built around a Raspberry Pi and an ITAR-free high-precision inertial measurement unit, and use open-source algorithms for the motion-detection software. We also discuss the results of an experimental campaign assessing the performance of the tag under challenging (“noisy”) environmental conditions and propose a set of standing-operating procedures for the buddy tag conceptrelevant for the arms-control and safeguards context.