Rabal, a Hekaran male
Doctor Rabal was a Hekaran who supported the theories of his sister, Serova that warp drive was damaging to subspace. Rabal was initially skeptical of his sister but he was later convinced that her theories may have had truth behind them.
In 2370, Rabal and Lieutenant Commanders Geordi La Forge and Data submitted a report to the Federation Science Council following the revelation that warp drive was in fact damaging subspace, eventually leading to a subspace rift forming. (TNG: "Force of Nature")
Rabal was played by actor Michael Corbett. The costume worn by Corbett as Rabal was auctioned off in the It's A Wrap! sale and auction.