Surveillance Direction System 
Satellite Data System 
Standard Depot System 
System Design Specification 
Software Design Standards 
Short Data Service 
Software Design Specification 
Steering Damping System 
Strategic Defense System 
Switched Data Service 
Science Data System 
Shuttle Data Stream 
Shuttle Dynamic Simulator 
Sorbent Decontamination System 
Safety Data Sheet 
Science Data Segment 
Scientific Data Set 
Scientific Data Sets 
Secure Digital Switch 
Shuttle Data Systems 
Shuttle Dynamic Simulation 
Software Development Specification 
Software Development System 
Space Defense System 
Students for a Democratic Society 
Switched Digital Service 
Synchronous Data Set 
safe delivery system 
Same-Day Settlement 
Satellite Discriminating Sensor