Asteroid 3753 has been known since 1986 and is on nearly the same heliocentric orbit as the Earth. It is a 3 mile wide asteroid with a slightly inclined orbit so that every 385 years its perigee boost with Earth places it alternately farther from the Sun and slightly closer to the Sun relative to the Earth. It seems not to get closer than about 40 times the Earth-Moon distance or 10 million miles from the Earth, so I would be hard pressed to call it a satellite or new moonlet of the Earth.
All answers are provided by Dr. Sten Odenwald (Raytheon STX)
NASA IMAGE/POETRY Education and Public Outreach program.