These are four approximately one-foot long pieces of Stanley Tool & Die metal measuring tape that were used as antennas for the Environmental Research Satellites built by TRW Space Vehicles Division for the Department of Defense. They formed part of a gift of a demonstration model of the satellite donated to NASM by TRW in April 1975. It is now stored at the Garber facility. The normal winding mechanism for a tape measure was reversed on the satellite to cause the tape to deploy after launch.

The TRS/ERS series of spacecraft were developed in the early years of the space program. They were called piggyback satellites because they were launched on other spacecraft and were then detached once in orbit. The primary mission of these small polygonal satellites was more often military than scientific in nature. Power for operation of the on-board instruments and transmitters was provided by silicon solar cells that covered the sides. The National Air and Space Museum's demonstration model is of the U.S. Air Force satellite ERS-17, flown aboard an Atlas-Agena vehicle on July 20, 1965. It stayed aloft for 43 hours.