[daip] AIPS ANTAB task

[Eric Greisen]

Lisakov Mikhail wrote:
> Dear Eric,
> 
> 
> My name is Mikhail Lisakov, I'm doing amplitude calibration of RadioAstron mission space and ground data.
> I've got a question about how does  AIPS ANTAB task work:
> 
> It is written in ANTAB help file that:
> 
> DPFU is "Zenith point source sensitivity (K/Jy)".
> 
> But is seems natural to define DPFU in the point (at the elevation, or whatever gain depends on) where aperture efficiency (or gain)
> has its maximum (and most colleagues I've asked think so too). 
> 
> So the question is:
> how does ANTAB task really treat DPFU value from ANTAB file?
> 
> 
> Thank you in advance.
> 
> Best regards,
> Mikhail Lisakov.

I have been away on vacation.

APCAL uses the DPFU to scale the gain curve also given in ANTAB.  If 
that gain curve were normalized to 1.0 at its peak, then the DPFU would 
apply to the maximum.  It is normally assumed that the gain curve is 
normalized to 1.0 at zenith and so that is where the DPFU would apply.
The two functions must go together but I see no reason why you could not 
do either.  The tasks clearly assume 1.0 at zenith for relative gain 
when you read the help file.

Eric Greisen