Donald J. Kessler is an American astrophysicist and former NASA scientist known for his studies regarding space debris.Kessler worked at the Johnson Space centre in Houston, Texas, as part of NASA's Environmental Effects Project Office.While there, he developed what is now known as the Kessler syndrome, which posits that collisions between space debris become increasingly likely as the density of space debris increases in orbit around the earth, and a cascade effect results as each collision in turn creates more debris that can cause further collisions. Kessler first published his ideas in 1978, in an academic paper titled "Collision Frequency of Artificial Satellites: The Creation of a Debris Belt."