[daip] Request for FITLD modification for DiFX data

[Eric Greisen]

Walter Brisken wrote:
> The software correlator produces output data that is nearly identical to 
> that of the hardware correlator.  I have found one difference that 
> requires a minor change to FITLD.
> 
> First, one can identify data produced by DIFX by looking at the FITS 
> header.  There will be a line
> 
> CORR    = 'DIFX'
> 
> at the top.  Feel free to suggest alternatives to this if this is not 
> appropriate.  I continue to set TELESCOP = VLBA and ORIGIN = VLBA 
> Correlator.
> 
> The change requested for DiFX is as follows:  The digital saturation 
> parameter, called SATUR in FITLD, should always be set to 1.0 for data 
> from DiFX.  This parameter is very tersely described in vlba scientific 
> memo 12.
> 
> As far as I can tell, all of the other corrections made for VLBA 
> correlator data also apply to DiFX correlated data.
> 
> Thanks,
> 
> Walter
> 
> 
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CORR is used for correction too much.  At present we do not detect 
unknown keywords so FITLD would have to recognize some new one.  OROGIN 
really is supposed to be VLBA or perhaps NRAO an institution.  So we 
should have a correlator keyword - how about CORRELAT or perhaps 
CORLATOR which is better as a mnemonic if poorly spelled.  The former 
follows the rule of correct but truncated spelling.

As for actually making these changes - we will see - I know nothing 
about SATUR.

Eric