Problem loading data from 1990

[bnorris]

Hello all,

Another question... I'm trying to analyse some old data from the archive, from 1990. But atlod gives the error message
RPFITSIN: Corrupted data encountered, skipping...
multiple times as it lists the various scans. It then thoughtfully flags out ALL of the visibilities:

Summary of spectra flagged
Flagging Reason Fraction
--------------- --------
Antenna off-source/off-line 12.4%
Bad SYSCAL values 87.6%
---------------------------------------

Are these bad SYSCAL values a real problem, ie the data is actually unusable, or is this an issue due to the age of the data files?

The files I'm trying to load are 90-06-29_1327.C3 ,90-06-30_0201.C3 and 90-06-30_1510.C3.

Thanks!
Barnaby

[ste616]

Hi Barnaby,

Try using the atlod options relax and samcorr for pre-1993 data.

[bnorris]

Thanks Jamie. I tried samcorr and relax but get
### Fatal Error: You cannot use options samcorr, xycorr or opcorr with relax
Using relax alone (without samcorr), atlod succesfully loads the data (although still with plenty of "RPFITSIN: Corrupted data encountered, skipping..." errors). However when I try to gpcal 1934-638 it reports that the scatter in estimating XY phase for antennas 1,2,4 and 5 are ~45 degrees, for each iteration. There's no obvious RFI seen in uvplt/pgflag, so I'm wondering if this data is suffering from the lack of samcorr corrections, etc.?

Cheers
Barnaby

[ste616]

Hi Barnaby,

The XY phase estimation errors could be because you can't supply xycorr as an atlod option with relax. I've never tried loading such old data before so I can't tell you all the errors you might encounter. Perhaps read the Miriad manual about the "XY phase problems" the old system suffered from to get an idea on how to proceed.