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| SAFER | simplified aid for EVA rescue |
| SAMS | Space Acceleration Measurement System |
| SAR | synthetic aperture radar |
| SPK | Stredstvo Peredvizheniy Kosmonatov [cosmonaut maneuvering unit] |
| SSAS | Solid Sorbent Air Sampler |
| STS- | Space Transportation System [designation for U.S. Space shuttle missions] |
| TDRS | Tracking and Data Relay Satellite |
| TEPC | Tissue Equivalent Proportional Counter |
| TI | terminal [phase] initiation |
| TSuP | Tsentr Upravleniya Polyotami [Russian flight control center] |
