A System Threat Assessment (STA) is obtained from the Intelligence community during the JCIDS shortfall identification process. It will be obtained primarily from the Capstone Threat Assessments (CTAs) and System Threat Assessment Report (STAR). The CTAs project foreign capabilities in particular warfare areas looking out 20 years.
Once the JCIDS Process identifies a materiel solution and the Material Solution Analysis (MSA) Phase begins, the program office should task the appropriate intelligence production center for the lead service to produce the STAR for Acquisition Category (ACAT) I / Major Defense Acquisition Programs (MDAPs) and the STA for ACAT II programs in accordance with the regulations of that service. The program office needs to work with the producing intelligence center to provide system specific characteristics as they evolve. The program office must also work with the appropriate Service Intelligence Production Center to identify Critical Intelligence Parameters (CIPs) and ensure production requirements are levied against those CIPs. 
AcqLinks and References:
-  Defense Acquisition Guidebook (DAG) – Section 8
- DoD Instruction 5000.02 “Operation of the Defense Acquisition System”
- Army Regulation 381-11 “Intelligent Support of Capability Development” – 26 Jan 07 – Section 4-2
- CJCSI 3312.01A “Joint Military Intelligence Requirement Certification” – 26 Feb 08