[meteorite-list] Space Radar?

[Sterling K. Webb]

> Optical telescopes can have very wide fields of view and are relative 
> cheap to build and operate making them the obvious choice, especially 
> in this cash strapped era.

Most important, the photons are FREE.
Unlike all those expensive electrons you
have to buy for radar...


Sterling K. Webb
--------------------------------------------------------------------
----- Original Message ----- 
From: "Richard A. Kowalski" <kowalski at lpl.arizona.edu>
To: <meteorite-list at meteoritecentral.com>; "Meteorites USA" 
<eric at meteoritesusa.com>
Sent: Thursday, April 14, 2011 12:40 AM
Subject: Re: [meteorite-list] Space Radar?


> --- On Wed, 4/13/11, Meteorites USA <eric at meteoritesusa.com> wrote:
>
> > From: Meteorites USA <eric at meteoritesusa.com>
> > Subject: Re: [meteorite-list] Space Radar? (Was: Cold Asteroids May 
> > Have A
> Soft Heart)
> > To: meteorite-list at meteoritecentral.com
> > Date: Wednesday, April 13, 2011, 10:15 PM
> > Richard, List,
> >
> > Since smaller meteoroids and asteroids are nearly
> > undetectable in space, and we're currently searching
> > optically with telescopes. Is it possible to detect
> > meteoroids/asteroids with space based radar?
> >
> > Will radar even work in space? If so, what's the range, and
> > how would it work? Do we have something like this?
> >
> > I know we have space based weather radar satellites, but
> > what about pointing them into empty space to search for
> > asteroids?
> >
> > Sorry if this is a dumb question... Just curious.
> >
> > Regards,
> > Eric
>
>
>
> Not a dumb question and one that I field every so often.
>
> While it could be possible to detect NEOs and other asteroids usig a 
> space based radar system, such a system would be ungodly expensive and 
> difficult to construct and operate.
>
> Remember that radar works by sending our the radio signal and then 
> observing the reflected energy. The radio telescopes here on earth 
> that observe asteroids and other planets using radar are huge (The 
> dishes at Goldstone and Arecibo) and they require huge amounts of 
> power to operate. The engineering alone would make the project 
> unlikely and the power requirements make it a non-starter.
>
> Also, while we are familiar with air traffic and weather radar systems 
> here on the surface, these are vastly less powerful than what would be 
> required by an NEO detection system. ATC radar can be much less 
> powerful than required to "paint" every target because most aircraft 
> have a transponder installed. The transponder in effect "hears" the 
> radar pulse and transmits essentially a "Here I am!" message in 
> response. Asteroids of course have no such transponder, so you have to 
> "paint" the asteroid and then detect the reflected signal.
>
> Finally, most radar systems have narrow beams. This Field of View is 
> tiny on the two dishes I mentioned. The optical community frequently 
> gets requests for continuing observations of NEOs that will be 
> observed with radar to make sure they point the telescope precisely 
> enough that the asteroid is in their beam. Even a handful of 
> arcseconds off (an arcsecond is 1/3600 of a degree) and they miss the 
> asteroid entirely.
>
> Optical telescopes can have very wide fields of view and are relative 
> cheap to build and operate making them the obvious choice, especially 
> in this cash strapped era.
>
>
> Hope this helps
>
>
> -- 
> Richard Kowalski
> Catalina Sky Survey
> Lunar and Planetary Laboratory
> University of Arizona
> http://www.lpl.arizona.edu/css/
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