[daip] 回复: Re: AIPS---fitld warning message

[童锋贤]

童锋贤 wrote:
>  
> >  > This is a bit curious - FITLD builds the initial calibration table (CL
> >  > version  1) from iinformation in the MC and IM tables.  This message 
> >  > says that there are times in the CL table  for which there was no MC 
> >  > table data within 1 minute.  You could try PRTAB on the CL table and 
> >  > examine the clock and atmosphere columns.  I suspect that normally they 
> >  > contain only zeros and, if so, this message contains nothing 
> >  > significant.  If they are not zero, then it might be good to find the 
> >  > relevant times and fix up the CL table manually.
> >  
> >  
> > Thank you!
> >  
> > I have tried to use "PRTAB" to print 'CL' table, and the values of clock 
> > and atmosphere columns were zeros. I set the values of 'clock' and 
> > 'atmosphere' to zeros in 'MC' and 'IM' tables in my fits file. As you 
> > say "I suspect that normally they  contain only zeros and, if so, this 
> > message contains nothing significant.", that mean only the value of 
> >  'clock' and 'atmosphere' columns in "CL" table which did not get clock 
> > and atmosphere, were zeros and nothing significant?
> >  
> >  
> > But, I use 'FITLD' (AIPS version '31DEC13' )to load fits file, sometimes 
> > there were no warnings at all (just like 'no_warning.FITS' in attachment),
> > sometimes I got some warnings "MC2CL: WARNING 8 CL RECORDS DID NOT GET 
> > CLOCK AND ATMOSPHERE" (just like 'have_warnings.FITS' in attachment). 
> > The fits files in attachment were created by me, maybe there're some 
> > bugs in my fits files.
> >  
> > I'm wondering how the 'MC2CL' work ,and which information do the 'MC2CL' 
> > use in the 'MC' and 'IM' tables.
> 
> MC2CL simply copies the clock and atmosphere corrections that were
> applied by the correlator into the CL table.  In general, these
> corrections are not known at correlation time and so are zero in the MC
> table and thus in the CL table.
> 
> Your example FITS file did however expose an error in the handling of
> the MC table (and potentially the IM table).  The fact that your MC
> table records were separated by < 2 seconds caused the fetching routine
> to fail to find the records which were present in the MC table.  I have
> corrected the code and, if you run a MNJ on Tuesday in 31DEC14, you will
> get the corrected version.  Note that there is no error since the data
> to be fetched was all zero.
>
> The IM2CL routine gets the geometric delay and dispersion terms applied
> by the correlator.  The former are not zero, the latter are usually
> zero.  Fortunately, the similar error for IM tables was only triggered
> by IM records closer than 1 second and so did not occur with your data.
> 
> Thanks you for following up on this matter


Thank you for your patience reply.

Am I must  upgrade to AIPS(version 31DEC14)? Is that ok if I still use AIPS(version 31DEC13)?

you said," The fact that your MC table records were separated by < 2 seconds caused the fetching "....."Fortunately, the similar error for IM tables was only triggered by IM records closer than 1 second and so did not occur with your data".  Maybe you mean "< 2 minutes" ,"closer than 1 minute"? 

I have separated the MC table records by nearly 5 minutes before, and I got the same warnings (MC2CL: WARNING ...). So, I separated MC table records by every 2 minutes if the SCAN of a observation  was longer than 2 minutes( usually the SCAN of a observation  was 5 minutes), but if the SCAN time was shorter than 2 minutes I sepparated MC table records by the SCAN time.



 
Fengxian Tong.
Shanghai Astronomical Observatory, CAS, 80 Nandan Road, 200030,Shanghai 
TEL: +86-21-3477-5512
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