Vacuum Tube, Space Surveillance Fence


Display Status:

This object is not on display at the National Air and Space Museum. It is either on loan or in storage.

Collection Item Summary:

This is a vacuum tube used in the U.S. Navy Space Surveillance Fence. The system's three transmitter stations, located across the southern United States, emitted a continous wave of radio energy in a narrow fan-shaped pattern. Together the beams extended about 5,000 miles from west to east and about 15,000 miles into space. Any object passing through a beam was illuminated and the reflected signals acquired by one or more or the six receiving stations along the same latitude as the transmitting stations. Each of the receiving stations had many hundreds of these vacuum tubes to amplify the reflected signals during the early years of operation of the system. Unclassified and classified catalogs of all known objects in orbit were prepared from data from the Space Surveillance Fence and other sensors.

The Air Force assumed operation of the Space Surveillance Fence from the Navy in 2004. It was decommissioned in 2013, to be replaced by a space-based system.

Amperex manufactured the vacuum tube. The Air Force transferred it to the Museum in 2014.

Collection Item Long Description:

Data Source

National Air and Space Museum

Restrictions & Rights

Do not reproduce without permission from the Smithsonian Institution, National Air and Space Museum



  • Non-Magnetic White Metal
  • Glass
  • Ferrous Alloy
  • Paint
  • Copper Alloy


3-D (Diameter x Depth): 9.4 × 16.5cm, 2.3kg (3 11/16 × 6 1/2 in., 5lb.)

Country of Origin

United States of America



Inventory Number


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