Why does 2003 UB313's designation not match its October 21 discovery date?

[tony873004]

If I understand correctly, the name 2003 UB313 means:

2003 - year of discovery
U - 2nd half of October (A=first half of January, B=2nd half of January, C=first half of February...)
B - the 2nd day in of this half-month interval. U begins on Oct. 16, so UB should be Oct. 17.
3 - The 3rd group of 25 objects discovered in the period U.
13 - The 13th object discovered in the 3rd group of 25 objects in the period U.

But...
The journal paper announcing the discovery says it was discovered in an image taken on October 21, 2003.

Anybody know why the 4 day discrepency?

Sorry for so many questions lately. I'm in my curious mood.

 

[tony873004]

I'm beginning to wonder if the B part is correct. It wouldn't make sense that any letter higher than P (value = 16) occupy the place of the 2nd letter. But another NEO, 2006 BQ6 was recently discovered. Am I interpreting the code correctly?

 

[tony873004]

I figured it out. I think? The website I got my info from got it wrong. B does not mean the 2nd day in the half-month interval. It means the 2nd object in the 314th group of 25 objects discovered in the half-month interval. (The 1st group of 25 objects has no subscript, so a subscript of 1 means the 2nd group). The reason it's groups of 25 and not 26 is because they drop the letter "i".

So B313 means 25*313+B. Since B=2, 25*313+2 = 7827

So UB313 means the 7827th object discovered in the 2nd half of October. That seems a bit high. Wikipedia reports that the rate of asteroid discovery is about 5000 per month. KBOs probably add a few 10s of objects to this. Maybe they were just having a good half-month.

Link explaining the designation scheme here:
http://cfa-www.harvard.edu/cfa/ps/info/OldDesDoc.html