S-band Spotlight

Arecibo Observes Triple Near-Earth Asteroid 3122 Florence!

Arecibo observed 3122 Florence from September 2 to 5 UT during its close approach to Earth and got amazing radar images of this triple system that was discovered with the Goldstone Solar System Radar days earlier! The primary body is about 4.5 km in diameter, rotates once every 2.4 hours, and shows ridges, indentations, protuberences, and clusters of crater-like depressions. It is attended by two much smaller moons, the streaks moving vertically through the image, that are only a few hundred meters in diameter. The moons appear very narrow compared to the primary in radar delay-Doppler images because they rotate much more slowly. And although the moons appear to go through the primary, they are actually orbiting it. This illusion is due to how three-dimensional space is projected into a two-dimensional radar image. The next time Florence will pass by Earth at a comparable distance will be in September of 2057.

About Us


The Planetary Radar Science 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 Planetary Radar program is fully funded through grants to USRA from NASA's Near-Earth Object Observations program (Grants NNX12AF24G and NNX13AQ46G). The Planetary Radar Science group is also partnered with the Center for Lunar Science and Exploration node (USRA-Lunar and Planetary Institute/NASA-Johnson Space Center) of the NASA Solar System Exploration Research Virtual Institute program.

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Recently Observed Objects


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

All observations in 2017 - most recent first

3122 Florence - TRIPLE system!
25 Phocaea - MBA
2017 BM31
2017 NH
2017 MQ7
2017 MC3
2017 ME4
2017 MB3
(96590) 1998 XB - very weak detection, almost 0.5 AU away!
(441987) 2010 NY65
2017 LX
2010 VB1
2003 WR21
2017 CS - Goldstone-to-Arecibo bistatic observation!
2017 LE
2017 KR27
(190166) 2005 UP156
(6063) Jason
(90075) 2002 VU94
(418094) 2007 WV4
2017 KJ27
(481532) 2007 LE - BINARY discovered in 2012!
(66391) 1999 KW4 - BINARY discovered in 2001!
Comet 41P/Tuttle-Giacobini-Kresak - first detected in March
2017 HK1
2017 HB1
2014 JO25
2017 FF128
2017 FX90
2017 FQ127
2017 FU64
2017 FU102 - weak detection
(143404) 2003 BD44
2017 FR63
2017 FV
2017 FR91
2017 FZ2
(215588) 2003 HF2
2017 EK - P < 1 min!
2005 ES70
(10636) 1998 QK56
2017 ED - P < 1 min!
2017 EF - possible weak detection
Comet 41P/Tuttle-Giacobini-Kresak
2017 DV15
2017 DA38
1998 YP11
16 Psyche
2012 DR32
2017 BM123
2017 CF32
2017 CP1
2014 QC3
2017 BW
(443103) 2013 WT67
Comet 45P/Honda-Mrkos-Pajdusakova
(364136) 2006 CJ
2015 BN509
2013 FK
163693 Atira - BINARY!
(265482) 2005 EE
(438955) 2010 LN14
2016 YC8
(85990) 1999 JV6
2016 YB8
4179 Toutatis - initially detected in late December 2016
1991 VK - initially detected in late December 2016
(226514) 2003 UX34 - BINARY!
2102 Tantalus

Past Observations

Upcoming Radar Targets

The following table includes targets with submitted observing proposals. It is not comprehensive for targets of opportunity, especially newly discovered asteroids. For possible targets of opportunity and long-term future radar targets, updated daily, see: All asteroids visible today (SNR > 2/day), this month (SNR > 2/day), and in the next five years (SNR > 100/day). Note that these tables inevitably include objects that are currently "lost," often suggested by "1d" in the Type column, which stands for "one apparition with a days-long arc," so observer beware!

Object Dates Expected
H mag Request Optical
Request Optical
Request Optical
2014 UR116 Oct 08-09 Imaging 19.7 Y PHA, period unknown
1989 VB Oct 08-23 High-res Imaging 19.7 Y Y PHA, 16-h period
2012 TC4 Oct 12-15 High-res Imaging 26.7 Y Y WORLDWIDE CAMPAIGN!
171576 (1999 VP11) Oct 15-19 High-res Imaging 18.5 Y Y PHA, period unknown
2003 UV11 Oct 27-29 High-res Imaging Y 18.5 Y Y PHA, 16.3-h period
1989 UP Oct 29-09 Imaging 20.5 30" Y PHA, 7-h period
444584 (2006 UK) Nov 11-18 High-res Imaging 20.1 Y Y PHA, period unknown
163696 (2003 EB50) Nov 21-27 High-res Imaging 16.5 Y Y 62-h period
2007 AG Dec 17-04 Imaging 20.1 Y PHA, period unknown
3200 Phaethon Dec 15-19 High-res Imaging Y 14.6 Y Y PHA, 3.6-h period
2008 WM64 Dec 21-23 High-res Imaging Y 20.6 Y Y PHA, 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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