Arecibo and Goldstone Radar Imaging of Contact Binary Near-Earth Asteroids L. A. M. Benner, M. C. Nolan, J. L. Margot, S. J. Ostro, M. K. Shepard, C. Magri, J. D. Giorgini, and M. W. Busch

Outline 1.Overview of NEAs detected by radar 2.Updated binary NEA statistics NB7 4.(1139) Atami 5.Smorgasbord of contact binaries 6.Upcoming NEA radar targets 7.Historical note

NEAs Detected by Radar

Binary NEAs: Statistics for Radar Targets OVERALL Discovered by radar: 21/33 = 64% Detected by radar25/33 = 76% Discovered at Arecibo:17/33 = 52% (Includes Sisyphus) Discovered at Goldstone:4/33 = 12% Since completion of the upgrade at Arecibo in 1999: Discovered by radar:20/25 = 80% Detected by radar:23/25 = 92% Abundance among radar targets: 17% Arecibo has become the primary technique for discovery and characterization of binary NEAs.

Binary NEAs Detected by Radar 2000 DP UG KW42001, ST272001, BM KK82002 Sekhmet RO12003, SS Hermes OS2003 (1990) Didymos DJ YT CE AB XD2005 Apollo2005 (1980) 2006 GY DC VV DT SN NB72008 Sisyphus 1985

2005 NB7

(1139) Atami

Contact Binary Candidates Detected by Radar 2201 Oljato (?)1983 Jun 4769 Castalia 1989 Aug 2064 Bacchus1996 Mar 4486 Mithra2000 Jul-Aug 2000 YF Jan 2002 FC2002 Jun 2002 NY Aug HK Aug OM72003 Jan KZ Oct Sigurd2004 Sep 2005 CR Feb 2004 RF Feb 2004 XL Dec 2007 VD Nov 2007 TU Jan-Feb 2002 TD Feb 4450 Pan2008 Feb Not included: 3908 Nyx 4179Toutatis 25143Itokawa Abundance: ~11% among NEAs > 200 m in diameter

What can we estimate for each? ObjectShape? Class OljatoNo S CastaliaAvailable BacchusAvailable Q MithraMaybe 2000 YF29No S 2002 FCNo 2002 NY40MaybeS 2002 HK12MaybeX 1993 OM7No 2001 KZ66YesS SigurdYes S 2005 CR37No C? 2004 RF84No 2004 XL14Not yetCReturns in December 2007 VD12NoS 2007 TU24NoS 2002 TD66NoS PanNoS

(2201) Oljato

(4769) Castalia

(2063) Bacchus

(4486) Mithra

2000 YF29

2002 FC

2002 NY40 Arecibo, Aug. 2002

(141593) 2002 HK12 Arecibo, Aug Aug. 25 Aug. 23

(52387) 1993 OM7 Arecibo-Green Bank 2003 Jan Jan 14

(68346) 2001 KZ66 Arecibo, Oct. 2003

(11066) Sigurd

(3908) Nyx

2005 CR37

2004 RF84

2004 XL14

2007 VD12

2007 TU24

(4450) Pan Arecibo, Feb Feb. 13 Feb. 12Feb. 14

Upcoming Radar Opportunities: JM8May-JuneA 2008 BT18JulyA, G YE45JulyA, G 2005 RC34JulyA, G VHAugustA, G 2000 DP107SeptemberA, G HW1SeptemberA UO1SeptemberA GN59OctoberA, G UT18NovemberA 2004 XL14DecemberA 2008 EV5DecemberA, G 2004 LV3DecemberA CS1JanuaryA, G

NEA Radar Detection History 40th anniversary of the 1st asteroid radar detection is in June: 1566 Icarus by Dick Goldstein at Goldstone