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UARS Upper Atmosphere Research Satellite (NASA)
U-MARF United Meteorological Archive Retrieval Facility (EUMETSAT)
UHF Ultra High Frequency
UMTS Universal Mobile Telecom System
UN United Nations
UNFCCC United Nations Framework Convention on Climate
UNISPACE United Nations Space Conference
UN-OOSA UN Office of Outer Space Affairs
UPS Unified Propulsion Subsystem
UTC Universal Time Coordinated
UWB Ultra Wide Band