Department of Defense Instruction 5105.58: Measurement and Signature Intelligence (MASINT) [open pdf - 130KB]
The purpose of this Instruction is to "establish policy, assign responsibilities, and provide instructions for MASINT management." It defines the policy, details specific responsibilities for each of the relevant agencies and departments, and includes a glossary of related acronyms and terms.
DOD Instruction 5105.58; DODI 5105.58
Defense Technical Information Center (DTIC): http://www.dtic.mil/dtic/