10 U.S.C. § 133a

(a) Under Secretary of Defense .— There is an Under Secretary of Defense for Research and Engineering, appointed from civilian life by the President, by and with the advice and consent of the Senate. The Under Secretary shall be appointed from among persons who have an extensive technology, science, or engineering background and experience with managing complex or advanced technological programs. A person may not be appointed as Under Secretary within seven years after relief from active duty as a commissioned officer of a regular component of an armed force. (b) Duties and Powers .— Subject to the authority, direction, and control of the Secretary of Defense, the Under Secretary shall perform such duties and exercise such powers as the Secretary may prescribe, including— (1) serving as the chief technology officer of the Department of Defense with the mission of advancing technology and innovation for the armed forces (and the Department); (2) establishing policies on, and supervising, all elements of the Department relating to defense research and engineering, technology development, technology transition, appropriate prototyping activities, experimentation, and developmental testing activities and programs and unifying defense research and engineering efforts and enhancing jointness across the Department; (3) serving as the principal advisor to the Secretary on all research, engineering, and technology development activities and programs in the Department; (4) directing the Secretaries of the military departments and the heads of all other elements of the Department with regard to matters for which the Under Secretary has responsibility; and (5) conducting developmental prototyping, designing and executing experiments of prototypes in the field to demonstrate operational relevance to address joint force capability gaps, and encouraging and supporting the rapid transition of technology from the research and development phase into operational use within the Department. (c) Precedence in Department of Defense.— (1) Precedence in matters of responsibility .— With regard to all matters for which the Under Secretary has responsibility by the direction of the Secretary of Defense or by law, the Under Secretary takes precedence in the Department of Defense after the Secretary and the Deputy Secretary of Defense. (2) Precedence in other matters .— With regard to all matters other than the matters for which the Under Secretary has responsibility by the direction of the Secretary or by law, the Under Secretary takes precedence in the Department of Defense after the Secretary, the Deputy Secretary, and the Secretaries of the military departments.