S-band Spotlight

Arecibo radar tracks close flyby of asteroid 2019 OK

On July 24, 2019, the near-Earth asteroid 2019 OK passed by the Earth at 1/5 of the distance to the moon. The object is between 50 - 130 meters in size, but was detected just 24 hours before its close flyby. Arecibo radar was used to greatly refine the asteroid's predicted orbit so that it can be tracked for the next century.

The figure on the left shows the detection of the asteroid from Arecibo radar. The 30 Hz offset of the reflected radio signal is used to refine the velocity and predicted trajectory of 2019 OK. The width of the observed signal is used to determine its rotation period. On the right, a schematic from JPL Horizons shows the proximity of 2019 OK to Earth during its close flyby.

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The Planetary Radar Science group is a department of the Arecibo Observatory, which is an NSF facility operated under cooperative agreement by the University of Central Florida (UCF), Yang Enterprises, Inc. (YEI), and la Universidad Metropolitana (UMET). The Arecibo Observatory Planetary Radar program is fully funded by NASA's Near-Earth Object Observations program.

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Recently Observed Objects


Past Observations

Upcoming Radar Targets

The following tables list: (1) targets with submitted observing proposals, including those from our annual high and medium priority proposals and (2) possible radar targets, often newly discovered asteroids, that may be detectable, but have not yet been scheduled for observation.

These tables are not comprehensive lists of all asteroids visible from Arecibo. For more complete lists of 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!

Requests for Optical/Infrared Observations

Astrometry: optical astrometry is specifically requested for objects with three-sigma plane-of-sky pointing uncertainties (from the JPL Horizons database) of tens of arcseconds or more. The plane-of-sky uncertainties refer to the first date of the radar observing window listed. Often these are lower limits as the pointing uncertainty often grows with time, especially for newly discovered objects; however, in some cases the pointing uncertainty is much lower prior to the object entering the Arecibo field of view. 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.

Spectra: spectra refers broadly to optical or infrared spectra and colors, which are most important for completeness of the strongest radar targets, for candidate binary asteroids, and for potential human-exploration targets. Observers are asked to relay probable spectral-class information to the radar team to compare with characteristics suggested by radar.

Object Dates Expected
H mag Request
153814 (2001 WN5) Aug 22-25 High-res Imaging 18.2 Y Y PHA, 2.7-h period?
99248 (2001 KY66) Sep 01 Astrometry 16.4 PHA, 19.7-h period?
237805 (2002 CF26) Sep 04-05 Imaging 17.4 3.8-h period
2100 Ra-Shalom Sep 06-10 Imaging 16.1 Y 19.8-h period, Yarkovsky candidate?
465617 (2009 EK1) Sep 12 Astrometry 21.4 Y PHA, NHATS, period unknown
1998 FF14 Sep 23-24 High-res Imaging 20.7 Y PHA, period unknown
2017 SL16 Sep 23 Astrometry 25.2 NHATS, period unknown
354030 (2001 RB18) Sep 27-28 Imaging 18.5 Period unknown
2015 KN120 Sep 27 Astrometry 20.4 NHATS, period unknown
162082 (1998 HL1) Oct 25-29 High-res Imaging 18.9 Y Y PHA, period unknown
2015 JD1 Oct 31-Nov 05 High-res Imaging 20.6 Y Y PHA, period unknown
481394 (2006 SF6) Nov 08-16 High-res Imaging 19.9 Y Y PHA, NHATS, period unknown
85236 (1993 KH) Nov 10 Astrometry 18.6 Period unknown
2005 WD Nov 10 Astrometry 21.9 PHA, period unknown
2010 JG Nov 11-12 Imaging 20.9 Y PHA, period unknown
2011 YS62 Nov 12-18 High-res Imaging 19.7 Y Period unknown
2012 MM11 Dec 06 Astrometry 20.3 PHA, period unknown
216258 (2006 WH1) Dec 13-14 Imaging 20.2 Y PHA, period unknown
2011 WN15 Dec 12-13 Imaging 19.6 Y PHA, period unknown
264357 (2000 AZ93) Dec 17 Astrometry 21.0 PHA, period unknown

The following may be detectable if scheduled for radar observations. Requests for optical astrometry are indicated where the pointing uncertainties are a significant fraction of, or larger than, our 2 arcmin pencil beam. Priority level (high, medium, low) is noted: high = likely to propose urgent radar observations, medium = may observe as a target of opportunity during other scheduled observations, low = unlikely to pursue. Priority level is subjective and is based on how detectable the object is, whether it is potentially hazardous or NHATS-compliant, and how likely it is to be scheduled. Objects may move from this table to the table above as they are scheduled on the telescope.

Object Dates Expected
H mag Request
Priority Level Notes
2019 QY4 Sep 06-14 Astrometry 27.9 Medium NHATS; period unknown
2019 RH Sep 08-12 Astrometry 26.0 Medium Period unknown
2019 RT Sep 09-10 Astrometry 24.3 Medium Period unknown
2019 RX1 Sep 09-12 Astrometry 25.4 Medium Period unknown
2019 RQ2 Sep 13-16 Astrometry 25.3 ~3 arcmin Medium PHA; period unknown
2019 RC Sep 14-18 Astrometry 21.8 ~1 arcmin Medium PHA; period unknown
2019 QZ1 Sep 19-30 Astrometry 23.3 ~1 deg Medium NHATS; period unknown
2019 SH Sep 22-23 Astrometry 21.8 ~40 arcsec Medium PHA; period unknown
2019 QY1 Nov 09-15 Astrometry 20.7 Medium PHA; period unknown

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