About Us

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.

For more information, follow us on Twitter at and

Click on an object in the solar system or choose from the list at left to learn more

list of planets Mercury Asteroids Jupiter Saturn Comets

Recently Observed Asteroids:


All detections in 2015 - most recent first

For media inquiries, contact our press officer Ruth Torres, rutorres at suagm.edu

2004 MW2
2015 LR21
2010 NY65
2015 LK24
2015 LQ21
1566 Icarus
2015 KW120
(417211) 2005 XL80
(285330) 1999 FN53
5381 Sekhmet - Binary, discovered at Arecibo in 2003!
2012 LC1
2015 HS11
194 Prokne
2015 HD10
2063 Bacchus
2015 GA1
(235756) 2004 VC
2015 FQ
2015 EL7
2015 FL
2015 EE7
2015 CW13
(189008) 1996 FR3
(416151) 2002 RQ25
(90416) 2003 YK118
2013 BK18
2014 YM9
2015 BG92
2015 AK45
69 Hesperia
2013 BZ45
(357439) 2004 BL86 - Binary!
2007 EC
(162004) 1991 VE
2062 Aten - fourth detection in four years!
2014 UF206
(85990) 1999 JV6
(410088) 2007 EJ

Upcoming Radar Targets:

Asteroid Dates Expected
H mag Request Optical
Request Optical
Request Optical
1566 Icarus Jun 17-20 High-res Imaging Y 16.9 Y Y PHA, 2.27-h period
2010 NY65 Jun 20-29 Imaging 21.4 Y PHA, period unknown
2015 HM10 Jul 06-08 High-res Imaging 16.6 2'-4' Y Y Bistatic, speckle, period unknown
(85989) 1999 JD6 Jul 15-04 High-res Imaging Y 17.1 Y Y PHA, 7.68-h period, K type
2011 UW158 Jul 14-17 High-res Imaging Y 19.4 Y Y PHA, NHATS, speckle, period unknown
(385186) 1994 AW1 Jul 20-30 High-res Imaging Y 17.5 Y Y BINARY, PHA, 2.52-h period, Sa type
(348400) 2005 JF21 Jul 20-24 Imaging 17.1 Y PHA, period unknown
(242291) 2003 NZ6 Jul 21-25 Imaging 19.0 13.5-h period
2010 PR66 Jul 25-28 Imaging 19.3 Y PHA, period unknown
2005 GO22 Aug 10 Astrometry 18.6 PHA, period unknown
2011 AK5 Aug 11 Astrometry 21.5 1' PHA, NHATS, period unknown
(206378) 2003 RB Aug 15-23 High-res Imaging 18.7 Y Y PHA, 16+ h period
(232691) 2004 AR1 Aug 16-21 Imaging 19.8 Y PHA, period unknown
(250458) 2004 BO41 Aug 26 Astrometry 17.8 Period unknown
4055 Magellan Aug 26-06 Imaging 14.5 Y 7.45-h period, V type
2011 UW158 Aug 29 Astrometry 19.4 PHA, NHATS, second opportunity this summer
(7822) 1991 CS Sep 01 Astrometry 17.4 PHA, 2.4-h period, S type
2001 UZ16 Sep 13 Astrometry 19.4 PHA, period unknown
(86666) 2000 FL10 Oct 01 Astrometry 16.8 Period unknown
1998 XN2 Oct 22-30 Imaging 19.5 0.5' Y PHA, period unknown
2009 FD Oct 26-02 High-res Imaging 22.1 Y Y Non-zero impact hazard, 5.87-h period
2006 UY64 Oct 28-01 Imaging 19.5 20'' Period unknown
2005 UL5 Nov 12-16 Imaging 20.2 Y PHA, period unknown
1864 Daedalus Nov 25 Astrometry 14.9 8.6-h period, Sr type
2011 YS62 Nov 26 Astrometry 20.2 5 deg! Period unknown
(345722) 2007 BG29 Nov 29 Astrometry 18.0 Period unknown
(163899) 2003 SD220 Dec 01-18 High-res Imaging 16.9 Y Y PHA, NHATS, period unknown
2011 WN15 Dec 02-09 Imaging 19.6 20'' Y PHA, period unknown
(163696) 2003 EB50 Dec 04-10 Imaging 16.4 27.2-h period
(33342) 1998 WT24 Dec 10-21 High-res Imaging 17.9 Y Y PHA, speckle, 3.697-h period
1995 YR1 Dec 20 Astrometry 20.2 1' Y PHA, period unknown
2002 AC5 Dec 22-27 Imaging 19.9 Y PHA, period unknown
2010 BB Dec 26 Astrometry 20.4 Y PHA, NHATS, period unknown
(294739) 2008 CM Dec 28-31 High-res Imaging 17.3 Y Y PHA, 3.054-h period
2004 MQ1 Dec 30 Astrometry 18.0 3' Period unknown

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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