Synchronous Payload Envelope 
Solid Phase Extraction 
Senior Procurement Executive 
Society of Petroleum Engineers 
Solid Polymer Electrolysis 
solid polymer electrolyte 
Secondary Particulate Emissions 
Shuttle Project Engineer 
Signal Processing Element 
Small Programming Enhancement 
Society of Plastics Engineers 
Software Product Engineering 
solar particle event 
Space Physiology Experiments 
Symbolic Programming Environment 
Systems Performance Effectiveness 
Semi-Public Environment 
Sensor Processing Electronics 
Serum protein electrophoresis 
Software Product Evaluation 
solar proton events 
Solid Phase Electrolyte 
Solid-Phase Epitaxy 
Space Physiology Experiment 
Spacecraft Power Electronics 
Spherical Probable Error 
Static Phase Error 
Switch Processing Element 
Synchronous Payload Envelop 
Synergistic Processor Element