Within the Department of Defense, the Missile Defense Agency (MDA) (formerly the Ballistic Missile Defense Organization) is responsible for developing and testing the Ballistic Missile Defense System There are three segments currently under development: Boost Phase Defense, Midcourse Defense, and Terminal Defense. An element of the Midcourse Defense Segment is the Ground-based Midcourse Defense (GMD), formerly known as the National Missile Defense (NMD). The proliferation of weapons of mass destruction and technology of long-range missiles is increasing the threat to our national security. The GMD is designed to protect all 50 States of the United States against limited ballistic missile attack by intercepting long-range ballistic missiles during the midcourse (ballistic) phase of their flight, before their reentry into the earth's atmosphere. The MDA completed the NMD Deployment Environmental Impact Statement in July 2000 to support a future deployment decision. The Secretary of Defense has not yet made a decision to deploy the GMD. However, the need has been identified to gain a higher level of confidence in GMD's capabilities through tests under realistic operational conditions. Validation of the operational concept (VOC) through ground testing of the GMD is a vital part of operationally realistic testing.