Tachyon sweep

A tachyon sweep was a scan which used tachyons. It was used by Starfleet officers from around the 23rd century to detect cloaked vessels inside nebulas.

In 2373, Lieutenant Tuvok suggested that the USS Voyager begin a tachyon sweep of a class 17 nebula in the Delta Quadrant. Tuvok explained that it would reveal the existence of cloaked ships, as he believed Voyager should be careful while being so close to Klingon space, despite the fact that Klingon Empire was on the other side of the galaxy. Tuvok's brain was infected at the time with a memory virus, which had him confuse the present with an altercation that Kang and the Klingons had with the USS Excelsior, a starship Tuvok served on in 2293, at the Azure Nebula. The class 11 nebula bore a similarity to the class 17 Voyager was near.