Carter had been a longtime member of the Defense Science Board and the Defense Policy Board, the principal advisory bodies to the Secretary of Defense. During the Bush administration, he was also a member of Secretary of State Condoleezza Rice's International Security Advisory Board; co-chair of the Senate Foreign Relations Committee's Policy Advisory Group; a consultant to the Defense Science Board; a member of the National Missile Defense White Team, and a member of the National Academy of Sciences Committee on International Security and Arms Control. He has testified frequently before the armed services, foreign relations, and homeland security committees of both houses of Congress.