"The Evolution of Technology in the Deep Space Network: A History of the Advanced Systems Program" (PDF). National Aeronautics and Space Administration, Jet Propulsion Laboratory, California Institute of Technology. p. 5. Archived from the original (PDF) on 2011-06-14. ↑ Neff, D. Use of a 2.3-GHz Traveling-Wave Maser on the Usuda 64-Meter Antenna (PDF).