subradar en · ADJ
Etymology
From sub- + radar.
Meanings
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(not-comparable) Below an area being investigated by radar.
One of the major difficulties with this method is that the largely unknown planetary topography can introduce errors in round trip travel times as much as 5 μs (i.e., the subradar point could be a mountaintop or a valley) […]
1993, Clifford M. Will, Theory and Experiment in Gravitational Physics, page 175: