Apparently it has been reported in the past 100 years, many people have observed a mysterious orbiting objects in the skies. This was documented way before any of earth's artificial satellites were launched by space exploring nations. It was documented by individuals all over the world at various times. Some individuals claim intercepting radio signals and others claiming that they are UFOs watching earth. NASA has stated that this is probably space junk from various space programs explorations.
The reason why this has been dubbed the "Black Knight" is a reference to Britain's attempt at rockets.It is also known as the Dark Knight and Ark. Sooner or later a national space agency or a private individual will identify what this is.