LOS (Loss Of Signal) … a term first popularized during the Apollo lunar missions when the astronauts were behind the Moon and out of line-of-sight radio communication with the Earth. Also refers to loss of signal during re-entry when the ionized atmosphere enveloping a returning spacecraft blocks all radio transmissions.

Dark Side of the Moon … that side of the Moon that always faces away from the Earth and is never seen. The side the Apollo astronauts saw during LOS.

“Doug, this is Houston. Do you read? Over?”

” ”

“Doug, this is Houston. Do you read? Over?”

” ”

“Houston, this is Scottsbluff. Doug is confirmed LOS.”

“Roger that, Scottsbuff. LOS.”

“Houston, this is Alliance. We concur with Scottsbluff. Doug has definitely gone Dark Side of the Moon.”

“Roger that, Alliance.”