ASO Assists NASA/JPL with Arecibo and Goldstone Asteroid Radar

The asteroid 2011 YH40 is approaching rapidly and will pass by the Earth in mid-January, attaining magnitude 14 as it speeds rapidly through the skies.
Presently, the minor planet is 17th magnitude high in northern skies and moving relatively fast, but easily measureable by experienced observers.

At this time, Doc Clay is assisting NASA for aiming and analysis of this asteroid with the world's greatest radio telescopes: the huge Arecibo and the steerable Goldstone antennaes as they prepare to study and map 2011 YH40 from January 14 through 16.

Joining ASO in this endeavor is Dr. Joe Pollock of the Appalachian Observatory (32 inch RC telescope), and well known minor planet researcher Brian Warner of Palmer Divide Observatory in the Rocky Mountains.

Since January 1, data from the three observatories has been steadily streaming into NASA and already ASO has contributed nearly 200 photometric and astrometric measurements of this target (see January 6 asteroid rotation plot from ASO, below).

Analyzing the data as it is contributed is the Czech astronomer Petr Pravec, who has already come up with several "best fit" solutions for the data submitted thus far. With the nearly full moon in the sky at this time, the signal to noise ratio of each measurement becomes quite problematic. Nonetheless, here are the initial data findings:

1) 2011 YH40 has a roatational period of what appears to be 3.356 hours with an uncertainty of only 0.002

2) there is a secondary "tumbling", perhaps end over end, of the minor planet with a period of about 23 hours.

3) the amplitude or magnitude change of the object during its rotation is about 0.5 to 0.8 magnitudes and varies from night to night.

The first graph below is the ASO plot from its data on Jannuary 6.0 UT, for a 6.5 hour observintg run; the seond plot is Dr. Pravec's analysis of all observers showing the remarkable consistency between the three observatories since January 1.
(CLICK TO ENLARGE)