Investigating nearby exoplanets via interstellar radar

Abstract

Interstellar radar is a potential intermediate step between passive observation of exoplanets and interstellar exploratory missions. Compared with passive observation, it has the traditional advantages of radar astronomy. It can measure surface characteristics, determine spin rates and axes, provide extremely accurate ranges, construct maps of planets, distinguish liquid from solid surfaces, find rings and moons, and penetrate clouds. It can do this even for planets close to the parent star. Compared with interstellar travel or probes, it also offers significant advantages. The technology required to build such a radar already exists, radar can return results within a human lifetime, and a single facility can investigate thousands of planetary systems. The cost, although too high for current implementation, is within the reach of Earth's economy.

Artificial Broadcasts as Galactic Populations. I. A Point Process Formalism for Extraterrestrial Intelligences and Their Broadcasts

“…Not every technosignature is a broadcast: unpowered artifacts in the solar system (Freitas & Valdes 1985;Rose & Wright 2004;Davies & Wagner 2013) and anomalous atmospheric compositions resulting from industrial pollution (Whitmire & Wright 1980;Lin et al 2014) are not broadcasts. On the other hand, not every broadcast need be an attempt at communication-they include directed energy transmission for power beaming (Inoue & Yokoo 2011;Benford & Benford 2016), propulsion (Lingam & Loeb 2017), or remote sensing (Scheffer 2014). Broadly speaking, waste heat from megastructures (Dyson 1960) and exhaust radiation from vehicles (Harris 1986) are broadcasts too.…”