On 2015 January 26, the near-Earth asteroid 2004 BL86 will pass within 0.008 AU of Earth (3.1 times as far away as the Moon). This will be the closest approach to Earth by this asteroid for at least the next 240 years.
As part of an extensive campaign of radar observations to learn about
BL86’s shape, spin state, and surface; and to refine knowledge of its trajectory; the Arecibo Observatory’s S-band planetary radar plans to illuminate the asteroid with a continuous-wave signal over 2015 January 27 03:45 – 04:00 UTC. Over that time, BL86’s radar echo will be received by elements of the Very Long Baseline Array and the Very Large Array in New Mexico. Anyone with an antenna and receiver capable of detecting the echo is welcome to listen in.
BL86 will be above the horizon for most observers in North and South America, and for some parts of western Europe and western Africa. To readily detect its radar echo, observers should have an antenna with an effective collecting area of at least 10 square meters. BL86 will be moving rapidly across the sky. Over Jan 27 03:45 – 04:00, it will move by ~0.5º. The asteroid’s exact position on the sky will depend on where it is observed from as well as the time, but will be near (RA,Dec) = (130º,+17º). A current ephemeris can be obtained from JPL’s Horizons system:
The Arecibo transmission will be tuned to give a nominal echo center frequency of exactly 2380 MHz at geocenter. Without correction for Earth’s rotation, BL86’s radar echo will appear as slowly-drifting and within 15 kHz of 2380 MHz. Predicted echo frequency as a function of time for a given location can be obtained on-request by emailing Michael Busch (firstname.lastname@example.org). We expect an echo bandwidth of 6 Hz or less.
Details of the BL86 radar observing campaign at the Arecibo Observatory, NASA’s Goldstone Solar System Radar facility, and the National Radio Astronomy Observatory are available at: