Could Jupiter be detected with an interferometer?

[Jan Lustrup]

Question: Could Jupiter’s thermal radiation be observed with a small interferometer?

 

I did a meridian transit interferometer observation a Dec+22 last night for Taurus A.

When looking at the whole observation run (see image 1) I saw what looked like weak fringes around 03:00 utc that did not look like random noise.

 

“Radio Eyes” showed that the planet Jupiter was transiting at that time (03:02utc) but around 0.5 degrees lower in elevation, but still well within my main beam.

I studied a zoomed-in “line-up” with a fringe period of 178 seconds that corresponds to a pin source seen  at Jupiter position at that time ( RA 07:47 & Dec +21:18) and got 8 fringe hits. (see Image 2).

It looks like there is another source also in the mix as well (3C192 is close by at RA 08.05 & Dec +24:10).

 

The Moon’s thermal radiation on 21cm is super strong with my setup (two 2meter dishes spaced 17.3 meters apart) , but what about a thermal source with a tiny diameter as Jupiter?

Could this be Jupiter or just wishful thinking?

 

Jan Lustrup LA3EQ

Norway

 

Image 1:

 

Image 2:

[fasleitung3]

Hi Jan,

The flux of TAU A at 1400 MHz is around 940 Jy. This gives you a signal with a peak to peak amplitude of about 1.1.

The signal you are referring to has an amplitude of about 0.015. This would then correspond to a source with a flux of about 13 Jy. This is way more than the expected thermal radiation. I have not done an excact calculation but a rough estimate gives me somewhere in the 100 mJy range. And this is with minimum Jupiter-Earth distance whereas at the moment Jupiter is further away.

So I don't think this has anything to do with Jupiter.

Best regards,

Wolfgang

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[Jan Lustrup]

Hi Wolfgang…

Thanks for the info and now I can put my mind at rest and not waist any more time on a possible Jupiter thermal detection.

Jan

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[duncan campbell-wilson]

Hi Jan and Wolfgang,

There were  a few papers in the 1990's when Shoemaker-Levy 9 interacted with Jupiter and the subsequent enhanced radio emission.

I know there was 36 cm and  21 cm imaging data taken.

 I am unable to access the publishing house papers.

 If someone has  library access I think you will find the papers have  the flux densities pre , post and during the  comet  crash.

The  radio  signature  of   Jupiter  was very much perturbed for a while after the interaction.

Rgds Duncan  

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[Eduard Mol]

Hi Jan, Wolfgang and all, 

Jupiter has some nonthermal (synchrotron) emission from 300MHz up to a a few GHz, known as “Jovian decimetric emission”. See also

https://ui.adsabs.harvard.edu/abs/2003Icar..163..434D/abstract

It is quite faint, about 5 Jy at 1.4 GHz.

Best regards,

Eduard

Op wo 26 nov 2025 om 10:36 schreef duncan campbell-wilson <duncan.cam...@gmail.com>

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[Jim Brown]

Decametric is a wavelength measured in decameters (10 meters), to
describe radio waves with wavelengths between 10 and 100 meters.
 300 MHz is not considered decametric.

Jim
HNRAO

On 11/26/2025 14:09, Eduard Mol wrote:
>
> It is quite faint, about 5 Jy at 1.4 GHz.

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[Eduard Mol]

I know, Jim :-)

I was referring to the “decimetric” (1/10th of a metre) emissions from Jupiter, NOT the much more well known decametric emissions that the Radio Jove people like to observe. 

Op do 27 nov 2025 om 01:19 schreef 'Jim Brown' via Society of Amateur Radio Astronomers <sara...@googlegroups.com>

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[Dimitry UA3AVR]

Here the presentation about detection of the Jupiter's thermal radiation from at 77 GHz, https://www.youtube.com/watch?v=dlolXA03sAU. This frequency is much more luminous, approximately (77 GHz/ 1.4 GHz)^2 higher in the flux density. Instrument - single dish 2.4 m, albeit with a significantly higher Tsys. I wouldn't say it was an easy job.

[Jan Lustrup]

I agree with using a single 2.4m dish, But how about using TWO dishes in an interferometer setup?

Maybe still impossible? I guess so.

Jan

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[Eduard Mol]

Well it depends…. Have you been able to detect sources with flux densities in the 5-10 Jy range with your interferometer? If so, then the ~5 Jy from Jupiter’s synchotron emission (according to the paper I linked in my previous post) may not be out of reach. 

Op do 27 nov 2025 om 19:41 schreef 'Jan Lustrup' via Society of Amateur Radio Astronomers <sara...@googlegroups.com>

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[fasleitung3]

Hi Eduard,

One has to keep in mind that the distance to Jupiter varies. Obviously it would be best to observe when it is closest but then you have radiation from the sun which will dominate everything, at least for smaller dishes with limited resolution.

So I am not certain how to interprest the 5 Jy in that context. Unfortunately the paper is behind a paywall so I don't know what the authors say about that.

As a side note: We have been able to "see" Jupiter at 3cm with our 10-m dish, but this was quite faint. I do not recall what the distance to Jupiter was at that point.

Best regards,

Wolfgang

[Dave Typinski]

Jupiter's closest approach happens at opposition, thus solar radiation would not
be a concern.

https://www.radiojove.net/SUG/Ephem/Jupiter%20Path%20Loss%202007-2054.pdf

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[Dave Typinski]

Jupiter's closest approach happens at opposition, thus solar radiation would not
be a concern.

https://www.radiojove.net/SUG/Ephem/Jupiter%20Path%20Loss%202007-2054.pdf

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[fasleitung3]

Of course you are right, Dave.
I still had our Earth-Venus-Earth experiment in mind. With Venus things
are just the other way round.

Wolfgang