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Season 1 - Sep. 28, 1987
Season 2 - Nov. 21, 1988
Season 3 - Sep. 25, 1989
Season 4 - Sep. 24, 1990
Season 5 - Sep. 23, 1991
Season 6 - Sep. 21, 1992
Season 7 - Sep. 20, 1993

Star Trek: The Next Generation Season 6 Episode 18
HD
Overview:
Stardate: 46682.4. The crew evacuates the Enterprise when the ship needs to be cleaned of particles that have built up over the ship’s hull. However, Picard accidentally stumbles over a terrorist group who plan on destroying the ship. He only has a short time to stop their attempts before the ship is swept by a beam of radiation to remove the particles that is lethal to all forms of life.