A nearby primordial-black-hole (PBH) evaporation burst would produce a curved gamma-ray wavefront, leading to detectable departures from plane-wave inter-satellite delays. We introduce a geometric method that combines imaging localizations with multi-spacecraft timing to determine the distance of a gamma-ray transient. Applied to -localized short GRBs, the most constraining event reaches 1. 2 AU, already probing a meaningful Solar System-scale regime. Our analysis shows that direct distance measurements are achievable to 10³ AU scales with the current and near-future technical capabilities. Once a finite source distance is measured, the corresponding PBH mass and lifetime can be directly inferred. Future wide-field localization and long-baseline deep-space gamma-ray detectors could extend such searches to 10⁵ AU and beyond. Swift
Xiao et al. (2026) studied this question.