That is a position reference beacon for an earth mapping Lidar system. They use a Laser based Lidar bore sighted with a standard Radar system to survey the changes in the earths surface. By using the two sensors covering different wavelengths they can very accurately measure the earths surface. I believe that their accuracy is somewhere on the order of ± .0002 inches but it is very difficult to quantify. The survey is being done under a grant from the NSA.
Oh by the way I have no idea what I am talking about but I did stay at a Holiday Inn last night.