Hi guys,
I have been looking at some data just after it has been ATLODed into MIRIAD format. I ran UVFLAG for the edge channels in the band (16cm CABB band), then for shadow(25). I then ran UVFSTATS on it to check the flagged percentages straight off the bat. The usual regions of the spectrum that are heavily RFI-afflicted are flagged (see plot of flagged percentage of Stokes xx,yy products vs. channel), but there are also two regions between channels ~240 - 510 and 775 - 1025 that have this weird repeating pattern of 2 bad channels (fully flagged) then 6 good channels. The RFI environment seems to be OK here (attached a plot of the RFI environment vs. freq), and given the regular pattern, I can only think that these are known correlator birdies that were flagged during the ATLOD stage by the birdies option. Does this sound reasonable? Are there any lists anywhere of the birdie channels?
Cheers,
Craig.
Birdies?
Moderator: Mark.Wieringa
Birdies?
- Attachments
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- Close-up of flagging pattern
- Screen Shot 2013-02-26 at 2.43.33 PM.png (11.98 KiB) Viewed 14631 times
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- Flagged percentage vs. Channel no.
- Screen Shot 2013-02-26 at 3.20.48 PM.png (17.29 KiB) Viewed 14631 times
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- RFI environment
- Screen Shot 2013-02-26 at 2.52.23 PM.png (81.87 KiB) Viewed 14631 times
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ste616
- Site Admin
- Posts: 220
- Joined: Thu Feb 04, 2010 3:27 pm
- Location: Paul Wild Observatory Narrabri NSW
Re: Birdies?
Hi Craig,
Yes, the Users Guide has the list of birdie channels, and there are only 12 of them (see the Users Guide).
The channels you are seeing as bad are most likely a block that has dropped during the observations, as the alternating bad channels is the signature of missing blocks. If you can give us the actual channel numbers (at at least just a couple of them) we can tell you which block was the problem.
These channels will have been flagged by the correlator, not by atlod, and cannot be recovered.
Yes, the Users Guide has the list of birdie channels, and there are only 12 of them (see the Users Guide).
The channels you are seeing as bad are most likely a block that has dropped during the observations, as the alternating bad channels is the signature of missing blocks. If you can give us the actual channel numbers (at at least just a couple of them) we can tell you which block was the problem.
These channels will have been flagged by the correlator, not by atlod, and cannot be recovered.
cheers
Jamie Stevens
ATCA Senior System Scientist
Jamie Stevens
ATCA Senior System Scientist
Re: Birdies?
Thanks Jamie.
OK. I think I can see that now. The observer has re-booted the block an done a dcal, pcal and acal about 1/3 of the way through a 12 hour run. This means that the first part of the observation and last part will have to be calibrated separately, yes? Or can I just use GPBREAK to insert a break-point in the gain interpolation at the point where this happened? Presuming I need to do a full calibration of both parts of the data, the observer did not re-do any time on 1934 after this event apart from setup - does that sink me?
Cheers,
Craig.
OK. I think I can see that now. The observer has re-booted the block an done a dcal, pcal and acal about 1/3 of the way through a 12 hour run. This means that the first part of the observation and last part will have to be calibrated separately, yes? Or can I just use GPBREAK to insert a break-point in the gain interpolation at the point where this happened? Presuming I need to do a full calibration of both parts of the data, the observer did not re-do any time on 1934 after this event apart from setup - does that sink me?
Cheers,
Craig.