Free-space (a) and guided-wave (b) and (c) ranging experimental schematics. Using parameter estimation techniques on interference-class waveforms, we estimate the distance between two scattering ...

On Aug. 14, 2021, a small near-Earth asteroid (NEA) designated 2021 PJ1 passed our planet at a distance of over 1 million miles (about 1.7 million kilometers). Between 65 and 100 feet (20 and 30 ...