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View this ticket online: <a href="https://help.nrao.edu/app#app.tickets,t:37451" title="(#)" style="color: #0065A3; font-family: Helvetica, Arial, sans-serif; font-weight: normal; padding: 0; margin: 0; text-align: left; line-height: 1.3; text-decoration: underline;">https://help.nrao.edu/app#app.tickets,t:37451</a>
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Francesco Ubertosi <francesco.ubertosi2@unibo.it> </td>
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Awaiting Agent
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Mac OS12
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Hello, I am working on observations performed with the VLBA in K and Q bands (project code BS301). I have good experience with VLBA data reduction in AIPS, but only at lower frequencies...
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<div>Hello, </div><div><span style="font-size:1.125rem;">I am working on observations performed with the VLBA in K and Q bands (project code BS301). I have good experience with VLBA data reduction in AIPS, but only at lower frequencies (L, S, C or X band). </span></div><div>My question is whether there are specific steps that one should go through when calibrating K or Q band data that differ from the typical calibration steps at lower frequencies. </div><div>I am asking this because I am having difficulties in fringe fitting the phase calibrator used to solve for phase, delays and rates. Even by using weightit 1, aparm(9) = 1 or a lower SNR threshold for solutions, I find many failed solutions. This holds for both K band and Q band observations. </div><div>I managed to fringe fit the calibrator at K band and transfer the solution to the target, but with the Q band data I have not solved the problem. I also tried using CALIB instead of FRING at Q band, because I thought that solving just for the phases and not also for rates and delays could help in finding the solutions - but without success. </div><div>My guess is that the phase calibrator (1303-170) is too weak to perform phase referencing. From my calibrated data, I measure a flux density at K band of around 50 - 60 mJy (total, while the peak flux density is 40 mJy). In the astrogeo database there is only one flux density measurement at K band from 2006, reporting a ~118 mJy flux density. Perhaps time variability has caused this calibrator to decrease its flux density? If its spectral index is steep, then the flux density at Q band may be even lower which would explain why I cannot fringe fit.</div><div>However, it may also be that there are specific steps to perform at K and Q bands that I have missed. </div><div>Could you please provide assistance with these points? </div><div><br></div><div>Thank you for your help. Best,</div><div>Francesco </div>
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