About Us

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The Arecibo Observatory planetary radar is the world's most powerful instrument for post-discovery characterization and orbital refinement of near-Earth objects. Arecibo radar observations are critical for identifying asteroids that might be on collision course with Earth and, if necessary, preventing a collision. Radar can provide detailed physical characterizations of NEAs:

  • If a small body is on course for an Earth collision in this century, Arecibo radar measurements could show this, and would dramatically reduce the difficulty and cost of any mitigation effort by defining the object's size, shape, mass, spin state, and orbit, and by revealing if it is one body or a two-body system.
  • Radar investigations of many NEAs are roughly equivalent, in their science content, to space flyby missions, but have a much lower cost (five orders of magnitude)

Radar is invaluable in determining the orbits of potentially hazardous NEAs.

  • Range-Doppler radar measurements complement optical observations by providing line- of-sight positional astrometry with precision as fine as 10 m in range and 1 mm/s in velocity, with a fractional precision 100 to 1000 times finer than that of typical optical measurements.
  • Radar data increase the average interval of predictability (relative to optical-only orbit solutions) by up to 370 years and can provide warnings of impact during the initial discovery period, whereas two widely separated observations are needed for optical-only orbits.
  • Radar data can quickly eliminate collision false alarms caused by optical-only data.

These unique capabilities of radar are critically important as we work towards the 2005 Congressional mandate of detecting and characterizing 90% of NEAs down to 140 m in size.

The Solar System Studies group is a department of the Arecibo Observatory, which is an NSF facility operated under cooperative agreement by SRI International, Universities Space Research Association (USRA), and la Universidad Metropolitana (UMET). The Arecibo Observatory radar is funded through the NASA Near-Earth Objects Observations program and scientific staff in the department are USRA employees.

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Recently Observed Asteroids:


All detections in 2016 - most recent first

For media inquiries, please contact our USRA communications lead, Dr. Edgard G. Rivera-Valentin

2016 LY8
2016 LG
XL91F8C - taken from NEOCP, now designated as 2016 LO48
(464798) 2004 JX20
2002 LY1
(35396) 1997 XF11
(441987) 2010 NY65
2016 CF194 - weak detection
2009 DL46 - extremely narrow bandwidth (slow rotation)!
2016 JC6
2002 CX58
2016 GS2
2016 HD3
2016 HK
2015 XA379
2001 BB16
(438661) 2008 EP6
2015 WE2
(85990) 1999 JV6
(162385) 2000 BM19
(337866) 2001 WL15 - first detected in Dec 2015

All detections in 2015

Upcoming Radar Targets:

Asteroid Dates Expected
H mag Request Optical
Request Optical
Request Optical
2010 NY65 Jun 12-01 High-res Imaging 21.4 Y Y PHA, period unknown
2002 LY1 Jun 12-13 Imaging 22.1 Y PHA, period unknown
2002 LT38 Jun 25 Astrometry 20.3 Y PHA, NHATS, period unknown
154244 (2002 KL6) Jul 12-16 High-res Imaging Y 17.5 Y Y Period unknown
3103 Eger Jul 23-24 Imaging 15.4 Y 5.7-h period, E type
2011 BX18 Jul 25 Astrometry 18.0 PHA, period unknown
2005 OH3 Jul 25 Astrometry 26.0 LOST? NHATS, period unknown
16834 (1997 WU22) Jul 26 Astrometry 15.6 9.3-h period, S type

Requests for Optical Observations:

Astrometry: optical astrometry is specifically requested for objects with plane-of-sky pointing uncertainties of tens of arcseconds or more. Optical observers are asked to submit astrometry to the Minor Planet Center as soon as possible after observations.

Lightcurves: optical lightcurves and period estimates are specifically requested for objects that will produce high-resolution images (i.e., possible shape models), for targets of IRTF thermal-infrared observations, for candidate binary asteroids, and for potential human-exploration targets. Lightcurve observers are asked to relay period estimates to the radar team to help with the planning of radar observations. During the analysis and modeling process, the radar team may request to use available lightcurve data.

Characterization: optical characterization refers to spectra and colors, which are most important for targets of IRTF thermal observations, for completeness of the strongest radar targets, for candidate binary asteroids, and for potential human-exploration targets. Optical observers are asked to relay probable spectral-class information to the radar team to compare with characteristics suggested by radar.

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