The parallax from the combined radio and 2007 Hipparcos HIAD data as a function of Radio Cosmic Noise (﹩{\sigma }_{\mathrm{radio}}^{\mathrm{noise}}﹩). The top hashed area (green) is the 2007 Hipparcos solution, and the hashed area below (red) is Hipparcos HIAD combined with the radio-only proper motions (this work, assuming ﹩{\sigma }_{\mathrm{radio}}^{\mathrm{noise}}=2.4﹩ mas). The combined radio+Hipparcos solutions are shown as circular symbols and error bars (blue) for different values of assumed ﹩{\sigma }_{\mathrm{radio}}^{\mathrm{noise}}﹩. When ﹩{\sigma }_{\mathrm{radio}}^{\mathrm{noise}}\gt 3﹩ mas, the sensitivity of the parallax to the radio positions is reduced.