[daip] AIPS ANTAB task

[Lisakov Mikhail]

Dear Eric, 

thank you for the reply.

>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.

Just to make sure that I've understood correctly:
1. If POLY is normalized to 1.0 at its peak, then DPFU is taken at the same point (regardless of is it zenith or not)
2. If POLY is not normalized then APCAL normalize it in the way that it would be 1.0 at zenith. DPFU is then taken in zenith, not in peak if peak is not in zenith. 

And some question:
3. How precise should peak be equal to unity?
4. How to use different POLYs for different polarisations? I've tried like that:

GAIN BD ELEV DPFU=0.21,0.21  FREQ = 4000,5000
RCP POLY=0.68365553602812,0.0105448154657294,-8.78734622144113e-05
LCP POLY=0.827027027027027,0.00648648648648649,-6.08108108108108e-05 /

but AIPS doesn't recognize it. 

Many thanks.


Best regards,
Mikhail Lisakov.
________________________________________
From: Eric Greisen [egreisen at nrao.edu]
Sent: 05 April 2013 22:07
To: Lisakov Mikhail; daip at nrao.edu
Subject: Re: AIPS ANTAB task

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