Under Secretary of Defense for Research and Engineering Mike Griffin has established a Defense Science Board task force to study the resiliency of the current GPS constellation and recommend architecture changes over the next 10 years that will improve the Defense Department's ability to "deny and confound" other space-based positioning, navigation and timing systems. The PNT task force, which Griffin introduced in a Dec. 6 memo , will begin its work in the next three months and complete its report...