National Weather Service United States Department of Commerce
Left: Haines Alaska ASOS,
Photograph by Tom Burgdorf
Right: A typical ASOS unit
ASOS Basics and Resources ASOS Technical Info
What is ASOS? Operations and Monitoring Center
ASOS User's Guide
Change for Ice Pellets 
User's Guide Appendices
If you have trouble viewing Table 4, and Figures 1, 18-19, see ASOS Charts
ASOS Tech News Page (restricted site)
Surface Weather Information/ASOS
ASOS Implementation
ASOS Sites (FAA) Forms