2019PASP..131h4401L

Glints of light from specular reflection of the Sun are a technosignature of artificial satellites. If extraterrestrial intelligences have left artifacts in the solar system, these may include flat mirror-like surfaces that also can glint. I describe the characteristics of the resulting flashes. An interplanetary mirror will appear illuminated for several hours, but if it is rotating, its glint may appear as a train of optical pulses. The resulting glints can be very bright, but they will be seen only if the mirror happens to reflect sunlight to Earth. The detection of large mirrors is limited mainly by the fraction oriented to reflect sunlight toward Earth. I give rough calculations for the expected reach of each exposure of Pan-STARRS1, LSST, and Evryscope for mirror glints. A single exposure of Pan-STARRS1 has an effective reach of 10^–9–10^–7 au³ for interplanetary mirrors with effective areas of 10 m², depending on rotation rate. Over several years, Pan-STARRS1 might accumulate a reach ∼10⁵ times greater than this, as it tiles the sky and different mirrors enter and exit a favorable geometry.