Goldstone detects "STRONG" radar echoes from 2010 AL30
Posted by Emily Lakdawalla
12-01-2010 22:05 CST
One final item before I go to bed: radio scientist Lance Benner posted to the Minor Planets Mailing list this evening the following message:
We have detected STRONG radar echoes from 2010 AL30 at Goldstone. The bandwidth is consistent with the object's expected size and the ~9 minute rotation period found by Bill Ryan and Richard Miles. We hope to obtain a precise size estimate soon.
The Doppler correction came in at about the 1-sigma level relative to our a priori estimate. We're updating the ephemeris now. Thank you again for all your help!
Nine-minute rotation? That is fast!! The observations of 2010 AL30 from Goldstone took place from 2:20 to 4:40 UTC on January 13.
When Benner says "thank you for all your help," his message is addressed to amateur astronomers around the world who pointed their telescopes at 2010 AL30 upon its approach, gathering information that helped to refine its orbit. In an earlier message to the group, Benner said "The pointing uncertainties have shrunk from about 523 arcseconds to about 11 arcsec at the start of tonight's track. Without all the astrometry you have reported, our observations would not be possible."
Although no backyard 'scope can equal the capability of Goldstone to measure the shape, size, and physical properties of an asteroid, Goldstone depends upon accurate positional information for its pointing. I'm sure they could have detected 2010 AL30 with less precise information; but to point in exactly the right direction results in much stronger echoes from the asteroid, improving the quality of their data by leaps and bounds. And being able to point so precisely might have been what allowed Benner to get time on such an important instrument on such short notice -- I'm not sure.
That's my favorite aspect of the study of near-Earth objects: the way that the science benefits from the participation of people at extremes of the observing spectrum, from the serious but amateur backyard astronomer to the scientists who run the world's largest telescopes.
I'll keep my eyes peeled for further science results from Goldstone's observations of 2010 AL30, and remember how they benefited from the help of amateurs.
A final note: JPL issued a statement this afternoon that contradicted some speculation across the Web, that because 2010 AL30 has a 1-year orbit that it might be an Earth artifact -- a lost rocket stage or some such thing. Although it does have a 1-year orbital period, "this object's orbit reaches the orbit of Venus at its closest point to the sun and nearly out to the orbit of Mars at its furthest point, crossing the Earth's orbit at a very steep angle. This makes it very unlikely that 2010 AL30 is a rocket stage. Furthermore, trajectory extrapolations show that this object cannot be associated with any recent launch and it has not made any close approaches to the Earth since well before the Space Age began. It seems more likely that this is a near-Earth asteroid about 10-15 meters in size...."
Analysis of the Goldstone data should be able to resolve this once and for all!