NASA: Large asteroid to pass safely by Earth on September 1; know more about 3-mile Florence NASA: Large asteroid to pass safely by Earth on September 1; know more about 3-mile Florence Asteroid Florence Is Among The Largest Near-Earth Asteroids That Are Several Miles In Size. Measurements From NASA's Spitzer Space Telescope And Near-Earth Object Wide-Field Infrared Survey Explorer (NEOWISE) Mission Indicate It Is About 4.4 Kilometers In Size. News Nation Bureau | Edited By : Kajol | Updated on: 19 Aug 2017, 04:57:37 PM New Delhi: A 3-mile big asteroid Florence will pass safely by earth on September 1. The Florence is one of the largest near-Earth objects currently being tracked by NASA.