Observations 2024-04-06 17:30-19:30 UTC

The same setup as in earlier observations was used. This time we had KAIRA, NenuFAR, LWA1, LWA-SV, LWA-NA, LWA-OVRO (unfortunately no useful data this time), DE602,603,604,605,609, FR606, SE607, PL610, PL612, IE613, LV614. DE601 was out of order, and the other DE stations used an incorrect pointing (position of Jupiter one month earlier), but still show signals.

I selected about four seconds (starting 18:20:45 UTC) of data with good Jupiter signals in most stations for the initial analysis. Data were channelised from LOFAR/NenuFAR subbands by a factor of $5^3=125$ and from the 19.6-MHz LWA bands by a factor of $2^8 * 7^2 = 12544$, which produces a final channel width of 1562.5Hz. A simple FFT was used instead of a PFB, even though the latter is also implemented. In this process the data were shifted towards the centre of the Earth as reference by applying an integer sample shift in the time domain and a fractional shift and fringe stopping (post-F) as phase correction after the channelisation. The software for this is not well tested, and all results should be interpreted with care.

For the plots below I uses a polarisation combination that should be close to the dominant circular sense. This is $X+{\rm i}Y$ for NenuFAR and the LWA and $X-{\rm i}Y$ for LOFAR and KAIRA. I only plot a limited part of the band.

We start with the shortest baseline NenuFAR-FR606. FR606 actually sits within the NenuFAR array:

The panels show the amplitudes for (top) NenuFAR and FR606 on a logarithmic scale, the phases of the correlation between them and finally a measure for the correlation coefficient (bottom). This is calculated as the phasing efficiency (0 to 1) when integrating the complex visibility over each pixel. The numbers in parentheses on the top right show how many bins in time and frequency are in each pixel.

What do we see? The FR606 data are affected by strong RFI, probably leaking in from lower frequencies. This shows that NenuFAR is much more RFI-robust. In the NenuFAR amplitudes on top, we see the structure of Jupiter's emission modulated by (probably:?:) interplanetary scintillation (e.g. dark lanes towards the right).

The phases are very stable, as expected, with the exception of RFI-affected parts. There are about two phase turns per MHz, which corresponds to a residual delay of about $2.2\,\mu\rm sec$. The cause of this is not entirely clear.

The phasing efficiency approaches 0.9 at the strongest parts, which means that the signal strength is well above the SEFD of the baseline.