[meteorite-list] Space Radar?

[Richard A. Kowalski]

--- 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/