Hi all! I'm new here; I hope I am posting this in the right place and that I won't sound too ignorant! I am currently studying Electrical Engineering, and pondering "outside the box" sorts of amateur observing setups that I might be able to tinker with down the road. I am particularly interested in tracking and characterizing near earth asteroids. I am wondering, would a home-brew radar system to study NEOs be at all feasible? How powerful would such a system need to be? Has anyone built something like this? Thanks in advance for any replies!
Amateur radar astronomy?
Posted 03 December 2018 - 10:38 AM
If you look at systems like the Very Large Array in Soccoro New Mexico, or any dishes being used by Professional Astronomers which are using Radar to determine sizes of and distances to asteroids, they are rather on the large size.
But then again, where would we be if Karl Jansky hadn't started Radio Astronomy, in the 1930's I believe. So, if you think you have what it takes, not to mention the resources to build a large radio dish(es) or be like George Ellery Hale and able to talk wealthy individuals into funding your equipment and research, then go for it. Where would we be if intrepid souls didn't "boldly go" and do what others wouldn't, couldn't or were too scared to?
Good luck and God Speed.
Posted 03 December 2018 - 12:40 PM
Just a comment to ponder but I had the opportunity to play with Nike and Hawk radar systems in the 60s and 70s. Compared to today's radio astronomy dedicated systems they were relatively small arrays but by the early 80s the Japanese had reduced 40 foot trailers of equipment to foot lockers and brief cases. I suspect that there are a few hundred of these systems gathering rust and dust in some government used equipment graveyard. A little ingenuity might just re purpose this equipment to your needs without having to reinvent the wheel.
Posted 03 December 2018 - 05:14 PM
The classic textbook is Radar Astronomy by Evans and Hagfors: https://archive.org/...ronomy/page/n63
This paper addresses your question specifically: https://echo.jpl.nas...st3_ostro .pdf
Radar is allowed in the amateur radio bands but the maximum power is 1500 watts PEP. You will need a very big antenna. To start looking at amateur radar, try looking up moonbounce ham stations and see what is involved. Clearly you should start doing amateur radio astronomy and work from there. So good reading.
Posted 05 December 2018 - 11:39 AM
Not sure if it has been mentioned here, but lightcurve inversion is the cheapest, most cost-effective and fastest way of characterizing the spin state and shape of a minor body. All you need is a computerized scope + CCD + photometry software. Much cheaper than a huge radar antenna.
Arecibo/Goldstone type radars are not usually owned by amateurs...
or many of the recent papers on 'Oumuamua, like https://arxiv.org/pdf/1711.04927.pdf
- dcbaros and PartlyCloudy like this
Posted 18 December 2018 - 02:47 PM
I live right down the road from Primalucelab which is an Italian brand. They make a professional radio telescope system and I believe it can be arranged in an array. They also designed and built the receiver in house.
Posted 06 January 2019 - 04:30 AM
Does the OP mean Radar or Radio?
Radar transmits a beam that impacts the/an object and then it receives the reflected beam back and performs measurements and determinations based on the reflected/received beam.
Radio is more passive, it basically points it's "ears" at a target or area of the sky and listens.
Ask as the initial post mentions Radar, now they are being directed at Radio scopes.
As they ask about NEO's I would assume they are enquiring about an active setup that pumps out a radar beam, and receives back a signal, not a more passive radio listening aparatus.
Edited by sg6, 06 January 2019 - 04:34 AM.
Posted 12 January 2019 - 02:58 AM
A topic I've look in to recently is building small passive radar systems with RTL-SDR dongles and arrays of antennas to triangulate and characterize meteors entering Earth's atmosphere.
Here's a link that I was looking at recently on the subject: https://hackaday.com...n-a-shoestring/
Edited by DigitalFox, 12 January 2019 - 02:59 AM.
Posted 23 January 2019 - 11:00 AM
Best thing to do is reach out to researchers in the field. IMO: Unless you can find a NEO observer who uses radar to characterize NEOs you will have no idea as to what is needed. Most amateur research in characterizing NEOS is via CCD photometry and light curve analysis. Even these more modest (and valuable) approaches eat up large amounts of money in equipment costs.
Posted 04 February 2019 - 08:36 PM
Well, something that might be interesting to see if it's possible is a passive scheme as follows: there are two big ground stations that do asteroid radar measurements; Arecibo and Goldstone; I've often wondered if when they are doing their asteroid observations that a smaller antenna can't at least pick up the reflection. You wouldn't have to transmit anything but you may have to know a lot about what they are transmitting, since radar nowadays often uses a complex phase modulation scheme such as polyphase Barker or Frank coding to create a synthetic, high power pulse out of a longer, low power transmitted signal. I don't know if that's how they do it for this type of observation, however. You have to know the transmit signal modulation scheme in order to reconstruct the reflected signal, as well as have enough antenna gain (aperture) to be able to detect it. They do announce ahead of time what asteroids are being observed when date-wise, so that optical observers can concentrate their light curve and astrometry on radar target candidates. The minor planet bulletin usually has a list of the upcoming radar observation candidates.