[daip] VLBAUTIL vlbapcor procedure

[Yuri Y. Kovalev]

Colleagues,

There was made a change in the way how PCAL solution is applied in the 
VLBAUTIL procedure vlbapcor.
Until AIPS version 31DEC06 inclusive a default interpolation was used.
Starting with 31DEC07 the interpol 'self' is applied:
%%% Part of the VLBAUTIL 31DEC07 code:
if vba_ok >=0 then
  type 'run pccor'
  task='pccor'; default; tget vlbapcor;task='pccor'
     delcorr 0; runwait('pccor')
  if(vba_frg>0)then
    type 'run sncor'
    task 'sncor';default; tget vlbapcor;task 'sncor'
      snver=MAXTAB('SN');opcode 'zphs';timer 0; sour ''
    runwait('sncor'); opcode 'zdel';runwait('sncor')
  end
  type 'RUN CLCAL'
  task 'clcal';default; tget vlbapcor;task 'clcal'
     gainv gainu; gainu=MAXTAB('cl')+1; snver=MAXTAB('SN')
     interpol 'self'; calsour '';timer 0; ante 0;runwait('clcal')
  vba_sn=snver
  vba_cl=gainu
end
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

I believe that this change can be potentially dangerous.
In case when a short scan is observed, no PCAL value might exist for a 
given short-scan source and interpol 'self' might deliever proper result.

I also see no specific reason why PCAL soulitons should be applied on a 
source by source basis (interpol 'self'). There must be no or very 
little dependence between the instrumental phase and different sources 
observed.

I suggest that you correct the vlbapcor back to the default 
interpolation in the task 'clcal'.

Cheers,
Yuri.