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

[Jan Lustrup]

Hi Eduard & all

Well my normal lower limit is around 10 Jy, but this varies due to external noise pick up vs antenna elevation/time of day etc..…. But I do see some sign of fringes from 5 Jy from time to time.

Here (see image below) is what could be Jupiter and 3C192 both at ~ 5 Jy and they are close to each other now. It seems to me I see only weak Jupiter fringes at first, then a fringe mix-up when both are in my antenna lobe at the same time, then later only 3C192.

Not sure but this is seen several times now. Jupiter moves at a slightly different speed then the background stars so the two sources are getting closer and closer together now. So I will have to wait several weeks before trying again when their separation is larger.

 

Jan Lustrup LA3EQ

Norway

   

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[fasleitung3]

Hi Jan,

What would really help with your analysis is to follow up on the idea of FFT of your data. I understand it is not so easy for you to implement it, but it would really get some good insight.

One of the things you could also do, is to average the transit of several days to improve SNR. Of course this could also be combined with the FFT.

Best regards,

Wolfgang

[Alex P]

Not sure an FFT will show much as the 'signal' is of near amplitude to,  and quite similar to the signature of the noise.

IF you send me the data file, I can try some filtering in Matlab

Echoing Wolfgang :  comparing / averaging several days of observations will be the best approach

Alex

[Jan Lustrup]

Hi Wolfgang,

Yes indeed….a follow up of FFT and averaging several days is the best way to go on.

You know, here in Norway we have a saying:

“necessity teaches the naked woman to spin clothes”

In other words: “make do with what you got”!

 

What I got:

Radio Eyes gives me Ra & Dec information, and the expected fringe period for any given declination at any meridian transit time.

It also gives me flux value of many sources, so now I have an idea about time of transit, expected fringe period and possible maximum fringe amplitude.

 

My antenna rotator display shows my azimuth and elevation.

I know my antenna baseline length and antenna HPBW.

 

RadioSkypipe has a good averaging option and one may zoom the graph in both X/Y axis, so I set up the time axis to 180 seconds pr vertical divider (the expected fringe period of Jupiter meridian transit) and did a 500 times post detection average. What looked like just noise in the raw data in the interferogram now turned into lots of nice fringes with many lining up (red *) to 180 seconds each! But of course Jupiter and 3C192 are only 20 minutes apart in transit time and a few degrees separated in elevation, so they will interact by having slightly different fringe periods, fringes  mingeling together at times.

 

So Wolfgang, am I detecting any type of radiation at all from Jupiter? If so, what type of radiation? Or is this only synchrotron radiation from the extragalactic source 3C192?

So far the jury is out.

Jan Lustrup LA3EQ

Norway

 

 

The t9From: 'fasleitung3' via Society of Amateur Radio Astronomers [mailto:sara...@googlegroups.com]
Sent: tirsdag 2. desember 2025 08:52

To: sara...@googlegroups.com
Subject: Re: [SARA] Re: Could Jupiter be detected with an interferometer?

 

 

Hi Jan,

What would really help with your analysis is to follow up on the idea of FFT of your data. I understand it is not so easy for you to implement it, but it would really get some good insight.

One of the things you could also do, is to average the transit of several days to improve SNR. Of course this could also be combined with the FFT.

Best regards,

Wolfgang

 

.

[Jan Lustrup]

Good idea Alex, that’s worth a try,,

Here attached is last night’s file I named “radioskypipe 2 dec25.spd”.

Jan

From: 'Alex P' via Society of Amateur Radio Astronomers [mailto:sara...@googlegroups.com]
Sent: tirsdag 2. desember 2025 13:33
To: Society of Amateur Radio Astronomers
Subject: Re: [SARA] Re: Could Jupiter be detected with an interferometer?

 

Not sure an FFT will show much as the 'signal' is of near amplitude to,  and quite similar to the signature of the noise.

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[b alex pettit jr]

Jan,

Its a binary data file .. can you create an ASCII file    *.txt,    *.csv   or something ?

[Jan Lustrup]

Sorry Alex, I do not know how to do that.

Jan

 

From: 'b alex pettit jr' via Society of Amateur Radio Astronomers [mailto:sara...@googlegroups.com]
Sent: tirsdag 2. desember 2025 14:14
To: 'Jan Lustrup' via Society of Amateur Radio Astronomers
Subject: Re: [SARA] Re: Could Jupiter be detected with an interferometer?

 

Jan,

 

Its a binary data file .. can you create an ASCII file    *.txt,    *.csv   or something ?

 

 

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[fasleitung3]

Hi Jan,

The key element would be to get the data out of RadioSkypipe in a format which can be used by other tools.

Alex has offered help to do some post-processing, but he is struggling with the data format. Maybe someone in the group here can help with that. I personally have never used RadioSkypipe and also I am afraid I do not have the time to help with that.

It is one of the unfortunate things that too many proprietory formats are invented.

Wolfgang

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[b alex pettit jr]

I found This

File Format (Radio-SkyPipe II)

Radio-SkyPipe II (R-SP) uses a binary proprietary file format for its data files.    
    File Extension
        By default, R-SP saves files with a .spd extension. (radiosky.com)

     ==========================================================
    Export Options
        R-SP provides a “Delimited File” export (text) for spreadsheet or database import. 
         The exported format is:   Date (delimiter) Time (delimiter) Raw data value (CR) per line. (radiosky.com)

     ===============================================================

[Don Latham]

Could be csv with a linefeed after cr?

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From: "sara" <sara...@googlegroups.com>
To: "sara" <sara...@googlegroups.com>
Sent: Tuesday, December 2, 2025 1:32:20 PM

Subject: Re: [SARA] Re: Could Jupiter be detected with an interferometer?

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406-626-4304

[b alex pettit jr]

YES That's what the specifier defines.

 Date    (delimiter)     Time    (delimiter)    Raw data value    (CR)        per line.