

NASA Captures New Images of Large Asteroid Passing Earth - ccarpenterg
http://www.nasa.gov/mission_pages/asteroids/news/yu55-20111107.html

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zrgiu_
from slashdot:

 _The article explains why the asteroid looks like a pixelated sprite taken
from the era of Monkey Island.

For those that didn't want to bother reading both articles and just wanted to
have a look at the image but then thought "WTF" after having a look at it:

"The individual pulses can be timed very accurately as well, so that the shape
of the asteroid can be determined, too. If there is a bump on the asteroid,
like a hill, then a pulse hitting that won’t travel quite as far as a pulse
that hits a crater. It gets back sooner, and this can be measured. The spatial
resolution of this method at the distance of YU 55 will be about 4 meters, so
they’ll be able to make an image that’s about 100 pixels across of it."_

~~~
ugh
I’m not really sure why that needs an explanation. All our imaging
technologies have a certain maximum resolution. The asteroid is small and far
away, ergo we are not going to get many pixels.

~~~
mturmon
I agree, about resolution.

But, people looking at the image may not understand it is a radar image, not
an optical image.

People might think that the highlights on the top of the image are sunlight,
and the dark area below is shadow, but of course they're not, because radar
doesn't care about sunlight.

In fact, I'm not sure how they pseudo-colored the images. In vanilla radar
imaging, you get the highest return off surfaces that are perpendicular to
line of sight (generally speaking). Here's a (model) plane radar image:
[http://www.fhr.fraunhofer.de/fhr/site/drucken_c336_f4_en.htm...](http://www.fhr.fraunhofer.de/fhr/site/drucken_c336_f4_en.html)
A lot of the radar imaging work is classified.

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beej71
I feel like I'm about to ask an incredibly dumb question, but why does the
radar image show such a pronounced crescent shape on the asteroid? What's
causing the radar "shadow"?

~~~
nitrogen
It's possible that those images show a side view generated from the radar
response, rather than a front view. The pixel intensity could be sample
intensity, so the more reflective surfaces there are at a distance Y, angle X,
the brighter the pixel at (X, Y) will be. Since the back of the asteroid is
shadowed by the front of the asteroid, the radar provides an image of the side
facing the radar only.

This is how I generate side and top view images from Kinect data in my
lighting automation software, anyway (Shameless plug: see
<https://github.com/nitrogenlogic/kinradar> for an ancient ASCII art version
you can play with, or <http://www.nitrogenlogic.com/> for the real thing). I
don't actually know how the NASA images were produced.

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Luyt
This asteroid has a page on WikiPedia,
<http://en.wikipedia.org/wiki/2005_YU55>

_"On 19 January 2029, 2005 YU55 will pass about 0.0023 AU (340,000 km; 210,000
mi) from Venus. The close approach to Venus in 2029 will determine how close
the asteroid will pass the Earth in 2041."_

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c4m
Additional information from <http://neo.jpl.nasa.gov/news/news171.html> :

\- the asteroid is 400 meters in size

\- it's a "C-type" asteroid (<http://en.wikipedia.org/wiki/C-type_asteroid>)

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kablamo
I think they just took a screenshot of some video game from the 90s. Duke
Nukem? Doom?

Seriously does this kind of image do anything for the scientists or is this
just PR?

~~~
mturmon
Tone is annoying but the question is good. Here's some background on why this
is being done:

<http://echo.jpl.nasa.gov/introduction.html>

Briefly: asteroid geology, better orbit prediction through understanding of
mass distribution, modeling for evolution of solar system studies.

There would have to be a rationale, because time on the telescopes is limited.

