2007 RS1
Closest Approaches to the Earth by Minor Planets
Distance  Date (TT)       Permanent designation   Provisional   H     Reference     
  (AU)                                            designation              
0.000086* 2004 Mar. 31.65                         2004 FU162   28.7   MPEC 2004-Q22
0.000226  2004 Dec. 19.86                         2004 YD5     29.3   MPEC 2004-Y35
0.000328  2004 Mar. 18.92                         2004 FH      25.7   MPEC 2004-F24
0.000466  2007 Oct. 17.64                         2007 UN12    28.6   MPEC 2007-U84
0.000492  2007 Sept. 5.05                         2007 RS1     30.6   MPEC 2007-R21
0.000560  2005 Nov. 26.02                         2005 WN3     29.9   MPEC 2005-W65
0.000564  2003 Sept.27.96                         2003 SQ222   30.1   MPEC 2003-T03
0.000665  2007 Dec. 13.17                         2007 XB23    27.1   MPEC 2007-X61
…
Absolute magnitude H=30.6 corresponds to a diameter of about 2 metres.
2007 RS1 currently holds the record for the smallest NEO with a well determined orbit