a friend of a friend-- someone you don't hang out with directly, but who moves within the same circles, and each of you know who the other is.
"That girl Ann is in my psychology class."
"I don't know who that is."
"Sure you do, she's one of Ashley's satellite friends: long hair, way too much makeup, always wearing purple somewhere..."
"Oh yeah, her."
Someone you have in your Facebook friends list not because you like them so much but because at one point in your life you met them and they live somewhere else completely and you never know when they might come in handy.
Jim: "Hey I was thinking of going to Europe this summer."
Jack: "Oh I have some satellite friends there you can get in touch with!"