The term "round-trip distance" is used in "laser ranging."
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This first ever active laser ranging over a round trip distance of nearly one half million miles was a great technological effort.
http://www.aman.org/leadership.html
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surveyor's laser ranging device measures a time interval of 1.176x10^-6 seconds for a laser light pulse to make a round trip from a marker
https://answers.yahoo.com/question/index?qid=20070921213131A...
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the laser beam provides a measure of the round-trip distance to LARES
http://space.skyrocket.de/doc_sdat/lares.htm
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Range resolved lidar for long distance ranging with sub-millimeter resolution
beat signal at 6.67 GHz corresponds to a round trip distance of 26.7 mm
https://www.academia.edu/25929962/Range_resolved_lidar_for_l...
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The Laser Ranging Retroreflector experiment was deployed on Apollo 11, ... providing a measurement of the round-trip distance between Earth and the Moon.
http://www.lpi.usra.edu/lunar/missions/apollo/apollo_11/expe...