Earth to Perform Asteroid 'Flyby', Radar imaging |
Earth to Perform Asteroid 'Flyby', Radar imaging |
May 3 2011, 09:02 AM
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Member Group: Members Posts: 648 Joined: 9-May 05 From: Subotica Member No.: 384 |
Asteroid 'Flyby' This Fall
In the text above it clearly says: "The best resolution of the radar images was 7.5 meters [25 feet] per pixel , when the asteroid was about 2.3 million kilometers away from Earth back in April 2010." Than it says that "When 2005 YU55 returns this fall the asteroid will be seven times closer. We're expecting some very detailed radar images. "When 2005 YU55 returns this fall, we intend to image it at 4-meter resolution with our recently upgraded equipment at the Deep Space Network at Goldstone, California." [/quote] So where is that upgrade?!? When imaging from 2,300,000 Km res= 7.5 m/pix When imaging from 325,000 Km res= 4 m/pix I just don't get it. If there was no "upgrade" resolution should be about 1 m/pix this time because asteroid is 7 times closer! Can anybody understand/explain this? -------------------- The scientist does not study nature because it is useful; he studies it because he delights in it, and he delights in it because it is beautiful.
Jules H. Poincare My "Astrophotos" gallery on flickr... |
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Nov 8 2011, 03:49 AM
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#2
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Solar System Cartographer Group: Members Posts: 10172 Joined: 5-April 05 From: Canada Member No.: 227 |
John's right, of course, but the same radar data could be used to create plane-of-sky images. Typically we do this for spherical objects like Venus (the most frequently imaged example)... and what you get is an image with north-south ambiguity and a blurry equator. For irregular objects like asteroids we don't know the plane-of-sky shape without further work, and the process gets too messy to work well. But plot it in delay-doppler coordinates and you get images like these, with the northern and southern sides superimposed. They are perfectly superimposed if the object is symmetrical, but in cases where the object is not symmetrical in delay-doppler space - like an elongated object tilted with respect to the incoming radar - most of the image is made only from one face of the object and there is only limited ambiguity around the sub-radar point.
Phil -------------------- ... because the Solar System ain't gonna map itself.
Also to be found posting similar content on https://mastodon.social/@PhilStooke Maps for download (free PD: https://upload.wikimedia.org/wikipedia/comm...Cartography.pdf NOTE: everything created by me which I post on UMSF is considered to be in the public domain (NOT CC, public domain) |
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