Anyone know how Synthetic Aperture Imaging works?

Radio Astronomy
1

I have been interested in Synthetic Aperture Imaging using multiple antennas to act as one larger one/

Anyone have any resources on how that works?

2

does this help?

https://www.unavco.org/instrumentation/geophysical/imaging/sar-satellites/sar-satellites.html

3

Not really but it is interesting.

4

think i misunderstood your question. Are you asking about the antenna system? Such as using several antennas as one by using GPS or other signal source to phase the antennas?

5

Yep!

That’s the thingy!

6

Yep!

That’s the thingy!

7

There’s multiple names for what you are describing. As the name suggests, synthetic aperture imaging aims at making an image of the sky in radio. Imaging is done by correlating the signals from different antennas.

However, you may also mean beamforming, where the signals from different antennas are added in phase to make a single, more sensitive antenna, whose beam is smaller than that of a single antenna.

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8

Specifically I mean using multiple antennas for radio astronomy to get a better image then the singular antenna can.

9

still not sure? by better signal, do you mean a better sig/noise ratio, or a wider beamwidth of the sky?

10

rom: Patrick Barthelow <apolloeme@gmail.com>
To: noreply@community.libre.space
Cc:
Bcc:
Date: Fri, 2 Nov 2018 20:44:05 -0700
Subject: Re: [Libre Space Community] [Radio Astronomy] Anyone know how Synthetic Aperture Imaging works?

Merlin is the name of a network of Very long baseline Radio telescopes, whose position on the earth is precisely known and whose
data streams can be combined in perfect syncronism with respect to UTC. giving a "view of the the same object or region of the heavens, that
takes advantage of the spacing and dish total areas.

So I looked up Merlin, and Synthetic Aperture on Google and got this link from NASA on the top, the first of the list. One of a 4 part NASA series

Best, 73, Pat Barthelow AA6EG
apolloeme@gmail.com

"The most exciting phrase to hear in Science, the one that heralds
new discoveries, is not “Eureka, I have found it!” but:
“That’s funny…” ----Isaac Asimov

11

What type of resources do you want?

You may want to check “Interferometry and Synthesis in Radio Astronomy” A. Richard Thompson

Also, Ivan MartĂ­ from Chalmers Univ. developed this Python program that allows you to simulate different antenna arrays and see the UV coverage and so on. https://launchpad.net/apsynsim
It is a cool and friendly program.

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12

Also, be careful, because the video you posted is about SAR (Synthetic Aperture Radar) which is a Radar technique (very awesome technique btw), but it is related to Earth Observation not to RadioAstronomy.

If you are interested in Radioastronomy, then the reference I provided you could be of help (I could try to find further references if needed). But if you are interested in SAR for Earth (*) Observation then that reference will not be of help.

(*) Earth or any other body orbited by a spacecraft (e.g. Mars)

13

In this case you are talking about interferometry, where the signals from all pairs of antennas are correlated to form so-called visibilities. These visibilities contain the information of the image of the sky, which can be recovered through a 2D Fourier transform.

Here is a python notebook showing how all-sky images can be formed by using 96 dipoles from the low-band antennas (10-90MHz) of the LOFAR Low Frequency Array: lofarimaging/LOFAR LBA imaging tutorial v4.ipynb at master · cosmicpudding/lofarimaging · GitHub

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14

There’s a group called the Society of Amateur Radio Astronomers that has some interesting small project ideas. There’s a little info on interferometry of the Sun using a pair of 8 foot diameter dish antennas.

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