Journal of Research of the
National Institute of
Standards and Technology

Cover Explanation:

The cover illustration shows a map of the SIM Time Network (SIMTN).  The SIMTN continuously compares the time standards of 16 national metrology institutes located in North, Central, and South America and publishes the measurement results in real-time on the Internet.  Many of the SIMTN members are responsible for keeping the “official time” for their respective countries.  For more information about this topic please see the paper by M.A. Lombardi et al., "The SIM Time Network" on page 557 of this issue of the Journal of Research of the National Institute of Standards and Technology. Cover illustration arranged by C. Carey.