The satellite explanation originated in 1954 when newspapers including the St. Louis Post Dispatch and the San Francisco Examiner ran stories attributed to retired naval aviation major and UFO researcher Donald Keyhoe saying that the US Air Force had reported that two satellites orbiting the Earth had been detected. At this time no man-made satellites had been launched.

Black Knight satellite.

 

Here are some links, for extra readings. Remember, links and websites are more interesting and valuable when they provide citations and sources.
Otherwise, they are just gossip.

http://www.ancient-code.com/20-facts-black-knight-satellite/

http://en.wikipedia.org/wiki/Black_Knight_satellite

http://inserbia.info/today/2013/05/black-knight-alien-satellite-in-earths-orbit-or-something-else/

http://www.abovetopsecret.com/forum/thread950743/pg1

http://www.armaghplanet.com/blog/the-truth-about-the-black-knight-satellite-mystery.html

http://beforeitsnews.com/space/2014/06/13000-year-old-satellite-the-full-story-of-the-black-knight-ufo-hd-video-2480068.html

http://skeptoid.com/episodes/4365