  Recent measurements at Q-band (43 GHz) have verified the improved performance
of the GBT provided by the updated gravity model that was deployed in the fall
of 2014. The measured gain curve is indistinguishable from 1.0 over an
elevation range from 15 degrees to 80 degrees. This represents a significant
improvement on the previous gain curve from 2009 that showed decreasing
efficiency below 40 degrees and above 65 degrees elevation. The current
estimated surface errors, under good conditions, is 230 microns for the GBT.
