Arecibo observed asteroid 2014 JO25 which will flyby Earth on April 19, 2017 at ~4.57 Lunar Distances.
http://www.naic.edu/~pradar/press/2014JO25.php
2014 JO25 was discovered in May 2014 by the Catalina Sky Survey and designated a potentially hazardous asteroid based on its size
and relative proximity to Earth. Prior to accurate radar measurements, its diameter was estimated using data from the NEOWISE spacecraft
to be 650 meters, more than twice the size of the Arecibo telescope's reflector. The Arecibo Observatory Planetary Radar system, which
is the most sensitive and the most active in the world, has now provided direct measurement of this asteroid’s size, shape, rotation,
and near-surface geology.
“Using radar, we can illuminate a near-Earth asteroid and directly measure its features. In this case, we found 2014 JO25 to be a contact-
binary or peanut-shaped asteroid,” noted Dr. Edgard Rivera-Valentín, Planetary Scientist with the Universities Space Research Association
(USRA) at Arecibo Observatory. “Each lobe is between about 640 m - 670 m in diameter for a total size of about 1.3 kilometers (0.8 miles)
along its widest point, so twice as large as inferred using infrared data from the NEOWISE spacecraft" continued Rivera-Valentín.
Additionally, Arecibo data suggests 2014 JO25 rotates about once every 3.5 hours.
