Abbreviation,Definition
21CSLC,21st Century Space Launch Complex
AA,Associate Administrator
AAAC,Astronomy and Astrophysics Advisory Committee
ACCESS,Advanced Collaborative Connections for Earth System Science
ACE,Advanced Composition Explorer
ACRIMSat,Active Cavity Radiometer Irradiance Monitor Satellite
ACS,Advanced Camera for Surveys (Hubble Space Telescope instrument)
ACT,Advanced Component Technologies
ADA,Americans with Disabilities Act
ADAP,Astrophysics Data Analysis Program
ADCAR,Astrophysics Data Curation and Archival Research
ADS,Astrophysics Data System
AES,Advanced Exploration Systems
AFOSR,Air Force Office of Scientific Research
AFRL,Air Force Research Laboratory
AIM,Aeronomy of Ice in the Mesosphere
AirMOSS,Airborne Microwave Observatory of Subcanopy and Subsurface
AIRS,Advanced Infrared Sounder
AITS,Agency Information Technology Services
ALHAT,Autonomous Landing and Hazard Avoidance Technology
ALI,Advanced Land Imager
AMMOS,Advanced Multi-Mission Operations System
AMMP,Aircraft Maintenance and Modification Program
AMO,Agency Management and Operations
AMS,Alpha Magnetic Spectrometer
AMSR-E,Advanced Microwave Scanning Radiometer for the Earth Observing
System
AMSU,Advance Microwave Sounding Unit
AO,Announcement of Opportunity
APPEL,Academy of Program/Project and Engineering Leadership
APRET,Astrophysics Research and Enabling Technology program (replaces
APRA) 
UHF,Ultra High Frequency
ULA,United Launch Alliance
URC,University Research Centers
USA,United Space Alliance
USAF,United States Air Force
USAID,U.S. Agency for International Development
USDA,United States Department of Agriculture
USE,Upper Stage Engine
USGCRP,U.S. Global Change Research Program
USGS,United States Geological Survey
USOS,U.S. On-orbit Segment (ISS)
USPI,U.S. Participating Investigators (Explorer)
USRA,Universities Space Research Association
UV,Ultraviolet
UVS,UV Spectrometer
VAB,Vehicle Assembly Building
VAFB,Vandenberg Air Force Base
VAO,Virtual Astronomical Observatory
VCL,Vegetation Canopy Lidar
VGA,Venus Gravity Assist
VIIRS,Visible-Infrared Imager Radiometer Suite (NPOESS Preparatory Project
instrument)
VLRS,Vehicle-Level Reasoning System
V&V,Verification and Validation
WFC,Wide Field Camera
WFF,Wallops Flight Facility (NASA, managed by GSFC)
WFIRST,Wide-Field Infrared Survey Telescope
WISE,Wide-field Infrared Survey Explorer
WMAP,Wilkinson Microwave Anisotropy Probe
WSC,White Sands Complex
WSTF,White Sands Test Facility, (NASA, managed by JSC)
XCVR,Transceiver
XMM,X-ray Multi-mirror Mission (Newton Observatory)
WMS,Web Mapping Service
XPI,X-ray Polarimeter Instrument