; 136 Stat. 2945) has been submitted to the congressional defense committees. (g) Phase 6.x process defined In this section, the term phase 6.X process means the phase 6.X process for major stockpile sustainment activities set forth in the memorandum of the Nuclear Weapons Council titled Procedural Guidelines for the Phase 6.X Process and dated April 19, 2000. 1641. Requirements relating to operational silos for the Sentinel intercontinental ballistic missile The Secretary of the Air Force shall refurbish and make operable not fewer than 150 silos for the LGM–35A Sentinel intercontinental ballistic missile at each of the following locations: (1) Francis E. Warren Air Force Base, Laramie County, Wyoming. (2) Malmstrom Air Force Base, Cascade County, Montana. (3) Minot Air Force Base, Ward County, North Dakota. 1642. Long-term sustainment of Sentinel ICBM guidance system (a) In general Prior to issuing a Milestone C decision for the program to develop the LGM–35A Sentinel intercontinental ballistic missile system (referred to in this section as the Sentinel ), the Under Secretary of Defense for Acquisition and Sustainment shall certify to the congressional defense committees that there is a long-term capability in place to maintain and modernize the guidance system of the Sentinel over the full life cycle of the Sentinel. (b) Certification elements The certification described in subsection (a) shall include a list of capabilities to maintain and advance— (1) accelerometers; (2) gyroscopes; (3) guidance computers; (4) specialized mechanical and retaining assemblies; (5) test equipment