http://www.marinetimes.com/story.php?f=1-292925-1521041.php

“TOKYO — The United States has asked Japan to shoulder three-quarters of the cost to move Marines from their base in Okinawa but plans to build a new radar system for a joint missile shield in Japan in the next six months, reports said Wednesday.”

From that and the rest of the article it sounds more like a permanent facility. SBX is essentially a ship. Wouldn’t make sense to tie it to a pier and leave it there. Even the original cited article said “The Japanese Air Self-Defense Force base in Tsugaru, Aomori Prefecture, is seen as the most likely candidate site to build the ground-based radar …”