; and (ii) the technical needs and capacities of the Department of Defense and the National Nuclear Security Administration, as applicable. (B) Department of Defense In selecting participants from the Department of Defense for the exchange program established under subsection (a), the Chairman shall ensure that there is a mix of military personnel and civilian employees of the Department. (d) Terms Exchanges pursuant to the exchange program established under subsection (a) shall be for terms of one to two years, as determined and negotiated by the Chairman and the Administrator. Such terms may begin and end on a rolling basis. (e) Guidance and implementation (1) Guidance Not later than 90 days after the date of the enactment of this Act, the Chairman and the Administrator shall jointly develop and submit to the congressional defense committees interim guidance on the form and contours of the exchange program established under subsection (a). (2) Implementation Not later than 180 days after the date of the enactment of this Act, the Chairman and the Administrator shall implement the guidance developed under paragraph (1). 1644. Procurement authority for certain parts of intercontinental ballistic missile fuzes (a) Availability of funds Notwithstanding section 1502(a) of title 31, United States Code, of the amount authorized to be appropriated for fiscal year 2019 by section 101 and available for Missile Procurement, Air Force, as specified in the funding table in division D, $9,841,000 shall be available for the procurement of covered parts pursuant to contracts entered into under section 1645(a) of the Carl Levin and Howard P. Buck McKeon National Defense Authorization Act for Fiscal Year 2015 ( Public Law 113–291