More than 210 VSAT links have been established so far to ensure communication with IMS monitoring facilities and national data centres (NDCs). The number continues to increase with more IMS stations being built. Each station needs to be equipped with communication devices to enable the sending of data for analysis to the IDC in Vienna. When several IMS monitoring stations are co-located, they use one VSAT set-up for the communication needs of all stations.

VSATs connect to six communication satellites which are located at a height of 36,000 kilometres above the equator. The satellites are geostationary, i.e. they rotate along with the Earth. Three of the satellites cover the areas of the Atlantic, Pacific and Indian Oceans. The other three satellites are stationed above North America, Europe and the North Pacific Region to provide for a more efficient coverage of the Northern Hemisphere.

Transmissions are routed from the satellites to three hubs on the ground which forward transmissions through terrestrial links to the CTBTO in Vienna.  Two of the hubs are located in the United States of America and one in Norway.

The hub on the west coast of the USA transmits data coming from the satellites covering the Pacific Ocean, the American and the North Pacific region. The hub on the east coast of the USA transmits data via the satellite covering the Atlantic Ocean region, and the hub in Norway covers transmissions from satellites above the European and the Indian Ocean region.