02dec2020
Date: Wed, 2 Dec 2020 00:18:26 +0530 (IST)
From: Nissim Kanekar <nkanekar@ncra.tifr.res.in>
To: Santaji N Katore <snk@ncra.tifr.res.in>
Subject: Mild issues in the ETC ...


Hi Santaji,

We had noticed an interesting issue with the ETC if users choose the "Continuum" mode but use a different central
observing frequency from the standard one. What happens is that if they choose a frequency too far away from the
peak of the band, the ETC calculator fails. This is because we have the following constraint:

if(gby_tsys > ref_gby_tsys * 0.5 ) { return(1.0/gby_tsys); }
        else { return(0.0); }

And ref_gby_tsys is measured at the peak of the G/T_sys curve, rather than at the central frequency. I think we
should fix this, by simply changing ref_gby_tsys to the value at the centre of the band as chosen by the user.
Basically, we should just evaluate ref_gby_tsys at the central frequency at the beginning, using the equation

gby_tsys= a*1 + b*x + c*x*x + d*x*x*x + e*x*x*x*x + p*x*x*x*x*x + q*x*x*x*x*x*x;

and setting x = central frequency.

Could you implement this?

Thanks!
Nissim

Dear Nissim,

        it is modified.

getsefed is changed

        if(band == "Band2" ) {  gain=0.33;}
        if(band == "Band3" ) {  gain=0.33;}
        if(band == "Band4" ) {  gain=0.33;}
        if(band == "Band5" ) {  gain=0.22;}

	x1=freq ; // Representative Frequency or central freq

	ref_gby_tsys=a*1 + b*x1 + c*x1*x1.... .... is added to each band.

Thanks,
Santaji