Franck Marchis is a French-born American planetary astronomer at the SETI Institute, where he is a senior astronomer and director of citizen science at the Carl Sagan Center. Born in Caen in 1973, he earned his doctorate in planetary science at the University of Toulouse and moved to the United States in 2000. He has written or co-written more than 200 peer-reviewed papers, mostly on small bodies of the solar system, and in recent years he has built networks of connected telescopes run by amateurs and automated sensors.

Marchis made his name with adaptive optics, the technique that sharpens ground-based telescope images by correcting for atmospheric blur. As an assistant research astronomer at the University of California, Berkeley, he led a team with colleagues at the Paris Observatory that used the European Southern Observatory's Very Large Telescope to find a second moon orbiting the asteroid 87 Sylvia. Reported in Nature in August 2005, the result made Sylvia the first known triple asteroid, and Marchis proposed the names Romulus and Remus for its moons. His group also measured the density of the Trojan asteroid 617 Patroclus, and asteroid (6639) Marchis was named for his work on multiple asteroids.

His career widened into instrument planning and the search for extraterrestrial technology. He has served on the Gemini Planet Imager steering committee and the Thirty Meter Telescope science definition team, studied directly imaged exoplanets, and worked on LaserSETI, which looks for brief optical flashes as possible technosignatures within the broader SETI effort. He co-founded Unistellar, the Marseille company that makes smartphone-linked eVscope telescopes, and as its chief scientific officer helped build a community of thousands of citizen astronomers. He was elected a fellow of the California Academy of Sciences in 2023.

Marchis's newer venture, SkyMapper, which he co-founded and leads as chief executive, is building a network of connected telescopes and all-sky sensors for astronomy, satellite tracking, transient detection and airspace monitoring. In June 2026 he promoted the project to UFO and UAP communities with an "ask me anything" session on Reddit, arguing that sky observations are fragmented, unverified and usually too low in resolution to be scientifically useful, and noting that barely 1 percent of meteors entering the atmosphere are detected. By October the company was offering SkyViewer, which lets users remotely operate network telescopes without owning one.

Marchis approaches UAP as a data problem rather than a question of belief: before anyone can say what is unusual overhead, he argues, there has to be a continuous, verifiable record of everything that is up there. That stance carries his long record in asteroid science and citizen astronomy into the UAP debate, where he offers SkyMapper to enthusiasts as a source of observing time and continuous sky coverage rather than as a search for any particular explanation.