[meteorite-list] Space Radar?

From: Meteorites USA <eric_at_meteoritecentral.com>
Date: Wed, 13 Apr 2011 23:41:34 -0700
Message-ID: <4DA6971E.5030506_at_meteoritesusa.com>

How much is the Earth worth? ;)

Eric


On 4/13/2011 11:35 PM, Sterling K. Webb wrote:
>> 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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>
>
Received on Thu 14 Apr 2011 02:41:34 AM PDT