Systems at Scale (SAS) refers to multi-system configurations.

The SAS Unit in RTSS develops solutions for multi-system issues through three related areas of work:

• product line practice (PLP), led by Lawrence Jones
  The goal of this work is to make product line development and acquisition a low-risk, high-return proposition for all organizations.
• system of systems practice (SoSP), led by Dennis Smith
  The goal of this work is to provide an integrated set of methods and practices specific for successfully engineering, governing, and acquiring systems of systems.
• system of systems software assurance (SoSSA), led by John Goodenough
  SoSSA is aimed at developing justified confidence that an SoS functions acceptably in its actual environment of use despite unanticipated usage, environmental conditions, or reconfiguration/evolution and despite the inevitable presence of defects and vulnerabilities.