A baryon sweep in progress
A baryon sweep is a procedure used to eliminate baryon particles from a starship. The baryons accumulate as a natural side-effect of warp travel and generally need to be removed every five years to keep harmful radiation from building up.
The sweep can be accomplished at specialized space stations such as the Remmler Array. The sweep is green in color and resembles a force field, capable of passing through solid matter. The strength of the sweep can be adjusted and made more effective for a ship which has made heavy use of its warp drive. The sweep is deadly to organic matter, and all lifeforms aboard a ship are evacuated to a safe location before the sweep is initiated. Additionally, the sweep can be damaging to certain areas such as the bridge and computer core, so field diverters can be installed in order to deflect the sweep and protect the sensitive equipment. Once the diverters are installed and the crew evacuated, an auto shutdown sequence is initiated, the ship is powered down, and the sweep begins. The sweep takes several hours to complete and is generally conducted from stern to bow.
The USS Enterprise-D docked at the Remmler Array for its first sweep in 2369. It needed a stronger than usual sweep because it had spent more time at warp in five years than most ships did in ten. (TNG: "Starship Mine")
- Baryons are heavy subatomic particles, including protons and neutrons. As practically all matter in the universe contains these particles a process which eliminates baryons wouldn't leave much of the Enterprise behind. We can assume that the baryon sweep refers to a specific type or types of heavy subatomic particle created by the subspace field of warp drive, rather than the entire family of them.
- This is never mentioned or even touched upon in VOY where it could have clearly been a problem. Since this episode it has never been mentioned again except as a possible explanation of the "5 year mission" limit of TOS as any more time could have resulted in radiation poisoning. However there is no proof to say the baryon sweep even existed then.