Spacecraft Navigation

On the planet earth we have reference points as to where we are. Where in space does NASA use as a reference point as to where the space shuttle is at a given moment?
I asked the question first and then when I found the answer I placed the link above called, "Spacecraft Navigation" as being the answer.

***
GPS (Global Positioning System) has greatly enhanced our ability to survey the planet.

***
From NASA
Hubble Space Telescope Released
Tue, 19 May 2009 08:05:28 AM CDT

"Using Atlantis' robotic arm, Mission Specialist Megan McArthur released NASA's Hubble Space Telescope at 8:57 a.m. EDT. With soft separation burn, Atlantis now is slowly backing away from the telescope. A jet firing will be performed in about a half-hour to increase Atlantis’ separation rate from the telescope, as the seven crew members bid farewell to Hubble for the final time."