S-band Spotlight

Comet 45P/Honda-Mrkos-Pajdusakova

Only the seventh comet imaged using radar!
E. Howell, C. Lejoly, E. G. Rivera-Valentin, L. F. Zambrano-Marin, A. Virkki report that Arecibo (2380 MHz, 12.6 cm) delay-Doppler images obtained on 12 February 2017 reveal Comet 45P/HMP is somewhat larger than previously estimated, at a size of 1.3 km and a rotation period of 7.6 hrs.
A press release of this observation was published in Comet 45P.

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.

For more information, follow us on Twitter at and !

Recently Observed Objects


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

All detections in 2017 - most recent first

2014 QC3
2017 BW
(443103) 2013 WT67
Comet 45P/Honda-Mrkos-Pajdusakova
(364136) 2006 CJ
2015 BN509
2013 FK
163693 Atira - BINARY! Observations at other wavelengths encouraged!
(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! Observations at other wavelengths encouraged!
2102 Tantalus

Past Detections

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
163693 Atira Jan 20 Astrometry 16.3 Y Y BINARY! 3-4 h period?
Comet 45P/HMP Feb 10-17 Imaging Y Comet!
443103 (2013 WT67) Feb 12-20 High-res Imaging 18.0 Y Y PHA, 135-h period?
2014 QC3 Feb 16 Imaging 20.6 Y PHA, period unknown
16 Psyche Feb 24-08 Spectra 5.9 MBA, 4.2-h period
11398 (1998 YP11) Mar 01 Astrometry 16.3 38.6-h period
Comet 41P/TGK Mar 02-08 Spectra Y Comet!
10636 (1998 QK56) Mar 12 Astrometry 17.5 Period unknown
2005 ES70 Mar 12 Astrometry 23.8 Period unknown, non-grav?
Venus Mar 20-27 Imaging Venus!
215588 (2003 HF2) Mar 26-31 High-res Imaging 19.4 Y Y PHA, period unknown
2015 TC25 Mar 27 Astrometry 29.5 40' NHATS, 2-min period
143404 (2003 BD44) Apr 06-May 07 High-res Imaging Y 16.8 Y Y PHA, period unknown
2014 JO25 Apr 12-20 High-res Imaging Y 18.1 Y Y Y PHA, period unknown
2016 JP Apr 18-20 Imaging 21.3 Y Y PHA, period unknown
Moon Apr 26-28 Imaging Moon!
Comet 41P/TGK May 09-17 Spectra Y Comet!
2007 LE May 23-28 Imaging 19.0 Y Y BINARY, PHA, 2.6-h period
Moon May 24-26 Imaging Moon!
418094 (2007 WV4) May 31 High-res Imaging 19.3 Y Y PHA, period unknown
90075 (2002 VU94) May 20-05 Imaging Y 15.2 Y PHA, 7.88-h period
6063 Jason Jun 02-10 High-res Imaging Y 15.9 Y Y 51.7-h period
441987 (2010 NY65) Jun 13-05 High-res Imaging 21.5 Y Y PHA, 4.98-h period, Yarkovsky?
2010 VB1 Jun 16-22 High-res Imaging 23.4 Y Y NHATS, period unknown
190166 (2005 UP156) Jun 06-Aug 11 High-res Imaging Y 17.1 Y Y 40.5-h period

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.

Quick Links