Operation -- Annihilate! - S1-E30
Visible crew/equipment: When Kirk and the landing party are standing on the transporter pads ready to beam down to planet, the camera pans to the right as the transporter operator stands at the console, and the end of the set is visible with black cables lying on floor. (00:07:15)
Operation -- Annihilate! - S1-E30
Visible crew/equipment: When Spock and McCoy walk into Kirk's quarters, in the wideshot the white tape mark can be seen on the floor under the desk at Spock's feet, before Spock requests permission to beam down to the planet, and can be seen again when Kirk stands up.
Chosen answer: If they're in orbit, they're being pulled along by the planet's gravity well, therefore, impulse engines would only be used for minor corrections and would be "on standby" while in orbit, but not active. (Like keeping your car idling without revving the engine and creating plumes of exhaust).
Captain Defenestrator
Thank you for the info.
Movie Nut