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projects:jupiter:intercont-2024-04-06 [2024/05/24 16:14]
wucknitz 		projects:jupiter:intercont-2024-04-06 [2024/08/28 09:26] (current)
wucknitz
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 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. 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.
  
 +
 +===== Presentations =====
 +
 +Some results were shown at conferences:
 +
 +{{:projects:jupiter:lfm2024.pdf|Talk by Olaf Wucknitz on 2024-06-07}} at the [[https://indico.lofar.eu/event/3/|LOFAR Family Meeting 2024]]
 +
 +{{:projects:jupiter:067_wucknitz.pdf|Poster}} at the [[https://events.mpifr-bonn.mpg.de/indico/event/371/|16th EVN Symposium in Bonn, 2-6  September 2024]]
  
  
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 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. 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.
 +
 +Historical note: Fringes on EU, US and EU-US baselines were first seen on the screen on 21st May 2024. The plots shown below were produced later.
  
  
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 +=== Strange effects ===
 +
 +In the zoom ins, some fine horizontal striping is visible in the phase and coherence plots for the LWA1 baselines. For LWA_NA-LWA-SV it is also there, but appears wider in these plots.
 +
 +Some investigation of these baselines and LWA-Europe baselines indicate that this is related to how the delay compensation is done in the stations. If my understanding is correct :?: :?:, the shift is done purely in the time domain for the LWA1 station, which means there are no funny frequency dependent effects. For the other stations, it is apparently applied in frequency space after channelising to 0.025MHz for LWA_SV, and a bit less (probably 196/8192=0.02392578125MHz) for LWA_NA. The bandpass of this process can be seen in higher-resolution plots of the amplitudes. In addition, the phases are very noisy, and the coherence is much lower, in a narrower regular pattern. Plots not shown here indicate that the period is exactly 1/4 of the channel width (of the order 6kHz).
 +
 +Here we show this by using a frequency resolution that is 4 times higher then before (50176 channels over the 19.6MHz band, channel width 390.625Hz.
 +
 +The plots for all three baselines show exactly the same frequency range:
 +
 +{{:projects:jupiter:lwa1-lwa_na_highres.png?300|LWA1-LWA_NA, highres}}
 +{{:projects:jupiter:lwa1-lwa_sv_highres.png?300|LWA1-LWA_SV, highres}}
 +{{:projects:jupiter:lwa_na-lwa_sv_highres.png?300|LWA_NA-LWA_SV, highres}}
 +
 +In the amplitudes we see the filter bands in LWA_NA and LWA_SV, but not in LWA1. The patterns from the former can be seen in the baselines to LWA1. The baseline LWA_NA-LWA_SV shows a combination of both, with a beating pattern (particularly low coherence at the lowest frequencies).
 +
 +The filter pattern is very plausible, but why we have this additional finer (factor of 4) modulation of the coherence is not clear to me. :?: :?:
  
  
 ==== Transatlantic baselines ==== ==== Transatlantic baselines ====
  
 +We start with baselines to NenuFAR, because it is by far the most sensitive European station. Residual delays are still large, therefore we use again the higher spectral resolution of 390.625MHz.
 +
 +
 +=== NenuFAR -  LWA 1 ===
 +
 +{{:projects:jupiter:nenufar_lwa1_1.png?300|NenuFAR-LWA1, full range}}
 +{{:projects:jupiter:nenufar_lwa1_2.png?300|NenuFAR-LWA1, zoom in}}
 +
 +In the zoom in, fringes can be seen at all frequencies.
 +
 +
 +
 +=== NenuFAR -  LWA_NA ===
 +
 +{{:projects:jupiter:nenufar_lwa_na_1.png?300|NenuFAR-LWA_NA, full range}}
 +{{:projects:jupiter:nenufar_lwa_na_2.png?300|NenuFAR-LWA_NA, zoom in}}
 +
 +In the zoom in, we do again see the regular pattern in frequency of higher and lower coherence and oscillating noise in the phases. 
 +
 +
 +=== NenuFAR -  LWA_SV ===
 +
 +{{:projects:jupiter:nenufar_lwa_sv_1.png?300|NenuFAR-LWA_SV, full range}}
 +{{:projects:jupiter:nenufar_lwa_sv_2.png?300|NenuFAR-LWA_SV, zoom in}}
 +
 +In the zoom in, we see how the high/low noise frequencies are a different from the ones seen in LWA_NA.
 +
 +
 +
 +=== DE602 - LWA1 ===
 +
 +With 7970 km this is the longest projected baseline:
 +
 +{{:projects:jupiter:de602_lwa1_1.png?300|DE602-LWA1, full range}}
 +{{:projects:jupiter:de602_lwa1_2.png?300|DE602-LWA1, zoom in}}
 +
 +
 +
 +=== KAIRA - LWA1 ===
 +
 +[[https://www.sgo.fi/KAIRA/index.php|KAIRA]] is very special, because it is not part of the general astronomical LOFAR array, but mostly used for ionospheric work. Thanks to the tremendous help of Derek McKay, it often participates in astronomical (VLBI and otherwise) observations. The projected baseline length to LWA1 is 6775 km.
 +
 +{{:projects:jupiter:kaira_lwa1_1.png?300|DE602-LWA1, full range}}
 +{{:projects:jupiter:kaira_lwa1_2.png?300|DE602-LWA1, zoom in}}
 
projects/jupiter/intercont-2024-04-06.1716560071.txt.gz · Last modified: 2024/05/24 16:14 by wucknitz     Back to top

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