Monday, March 4, 2013

Close approach of Asteroid 2013 ET

M.P.E.C. 2013-E14, issued on 2013 March 04, reports the discovery of the asteroid 2013 ET (discovery magnitude 16.9) by Catalina Sky Survey (mpc code 703) on images taken on March 03.3 with a 0.68-m Schmidt + CCD.

2013 ET has an estimated size of 64 m - 140 m (based on the object's absolute magnitude H=23.1) and it will have a close approach with Earth at about 2.54 LD (Lunar Distances = ~384,000 kilometers) or 0.0065 AU (1 AU = ~150 million kilometers) at 1207 UT on March 09 2013. This asteroid will reach the peak magnitude ~15.0 on the first hours of March 09.

We performed some follow-up measurements of this object on 2013, March 04.4, while it was still on the neocp, remotely from the Haleakala-Faulkes Telescope North, through a 2.0-m f/10.0 Ritchey-Chretien + CCD (Faulkes Telescope is operated by Las Cumbres Observatory Global Telescope Network). Below you can see our image, stack of 5X10-second exposures, taken with the asteroid at magnitude ~16.9 and moving at ~6.15"/min. At the moment of the close approach 2013 ET will move at ~ 153"/min. Click on the image below to see a bigger version. North is up, East is to the left.

Below you can see a short animation showing the movement of 2013 ET (three consecutive stacks of 5X10-second exposures each). North is up, East is to the left. Click on the thumbnail for a bigger version:

UPDATE - March 10, 2013

Due to its close approach, 2013 ET was a strong radar target at Goldstone. On a message on mpml, JPL Radar Team confirmed  they were able to detect radar echoes from 2013 ET at Goldstone on March 07.

"The radar signal-to-noise ratios were stronger than expected and we obtained images with a range resolution as fine as 7.5 meters/pixel, but even so, the images barely resolve the object into a few range rows because 2013 ET is so small.  The Doppler broadening (aka the bandwidth) of the echoes varies as the asteroid spins, so clearly it's somewhat elongated, and there are hints of irregularity in the shape in the images. We're planning to release some images after the track on March 10 when we should see more detail if things go well."

UPDATE - March 19, 2013

As announced on the previous update of this post, asteroid 2013 ET was successfully targeted by the 70-meter Deep Space Network antenna at Goldstone, Calif. A sequence of radar images was obtained on March 10, 2013 by NASA scientists when the asteroid was about 1.1 million kilometers from Earth, which is 2.9 lunar distances.

"The radar imagery suggests the irregularly shaped object is at least 130 feet (40 meters) wide. The 18 radar images were taken over a span of 1.3 hours. During that interval, the asteroid completed only a fraction of one rotation, suggesting that it rotates once every few hours."

Credit: NASA/JPL-Caltech/GSSR

by Ernesto Guido, Kris Rochowicz & Nick Howes

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