The Transportable Array is composed of 400 seismometers that are being deployed in a rolling grid across the United States over a period of 10 years. The stations are placed 70 km apart, and can map the upper 70 km of the Earth. After approximately two years, stations are moved east to the next site on the grid – unless adopted by an organization and made a permanent installation. Once the sweep across the United States is completed, over 2000 locations will have been occupied. The Array Network Facility is responsible for data collection from the Transportable Array stations.