NASA’s next-generation cosmic observatory — the Nancy Grace Roman Space Telescope — is set to launch this weekend on a potentially decade-long mission to hunt for distant exoplanets, map out the Milky Way and unravel some of the universe’s biggest mysteries, such as the true nature of dark matter.

The Roman telescope and its payload are scheduled to lift off aboard a SpaceX Falcon Heavy rocket Sunday (Aug. 30) at 7:26 a.m. EDT from Launch Complex 39A at…