GSN(Ground Station Network:GSN) is the network of some universities and organizations. If you can not communicate with your satellite in your Ground Station, you can do that thorugh the other Ground Station of GSN menber at the same time. GSN menbers are Tokyo univ., Titech, Kyushu univ., Nihon univ., Soka univ., Hokkaido Kogyo univ., Koku Kosen, Takamatsu Kosen, KSE, Stanford univ., and Santa Clara univ.
See more details about GSN at GSN official website.
GSN Official Website