Supplemental Security Income 
Scuba Schools International 
Small Scale Integration 
Solid-State Imager 
Sensitive Security Information 
Solid State Imager 
Solid State Imaging 
Space Studies Institute 
Spectral Solar Irradiance 
Steady-state irradiation 
Strategic Studies Institute 
Server Side Includes 
Spaceport Systems International 
Serial Signal Interface 
Server Side Include 
Significant Structural Item 
Single-Source Image 
Sliding Scale Insulin 
Social Security Income 
Social Services Inspectorate 
Solar Spectral Irradiance 
Soldier Support Institute 
Space Services Incorporated 
Spectral Statistical Interpolation 
Storage-to-Storage Instruction 
Attack Submarine 
Schedule Support Impact 
Short Subscriber Identity 
shoulder sleeve insignia 
Single Signal Interconnect