New array at Leitrim?
The new cleared space overlaps but is not quite concentric with a large circular area that was cleared and graded around 1967. The original space was suitable for a large circularly disposed antenna array (CDAA) such as an FRD-10, but no array was ever built on the site. It is probably not a coincidence that two FRD-10 arrays were built at other stations in Canada (Gander and Masset) at around the same time, under a program called Project Beagle. It is possible that the original Project Beagle called for the construction of three FRD-10 arrays, but that the Leitrim array was cancelled at some point early in the process, most likely for budgetary reasons.
Whatever the reason, a smaller (and cheaper) Pusher CDAA was built at the station in the early 1970s, but the large graded area remained unused.
Large CDAAs have gone almost completely out of style in the intervening years. Canada operates the only two FRD-10 arrays remaining in the world. The U.S. still operates two even larger CDAAs called FLR-9s, and a third may still be in service with the German BND. And the Russians still operate a half dozen or so large Krug arrays, with Ukraine and perhaps one or two other former Soviet countries possibly also keeping a few in service.
But the days when more than 50 large CDAAs were in operation around the world are long gone.
We can be quite confident, therefore, that whatever system is built in the new circle at Leitrim, it won't be one of the classic "Elephant Cages" of the Cold War.
One possibility is that the new space is intended simply to host the beverage rosette array already at the station. That array was built around 1998 in two distinct sections: a 180-degree fan to the north of the main station buildings and a second 180-degree fan on the south side of Leitrim Road.
The Department of National Defence has been working on a plan to re-route Leitrim Road further south of the main station buildings, and it may be that the location of the southern fan conflicted with that plan, leading to a desire to move the array to a new location.
Presumably time will tell.
Which is good, because DND generally doesn't.
[Update 24 July 2012: It's the beverage array. More details here.]