[daip] forwarded message from Chris Phillips

[Eric Greisen]

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From: Chris Phillips <phillips at jive.nl>
To: Eric Greisen <egreisen at cv3.cv.nrao.edu>
Subject: Re: AIPS and JIVE
Date: Thu, 25 Jan 2001 13:15:47 +0100 (MET)

On Tue, 23 Jan 2001, Eric Greisen wrote:

> Can you remind me why it is that you are coming?

I can give you a more detailed summary next week after I have spoken to a
few people here. But basically the problems I can think of from the top of
my head:

FITLD using binary fits (rather than uvfit) assumes that the data is from
VLBA correlator (ignoring the INSTRUM keyword). We what to us binary fits,
but cannot because all sorts of VLBA specific stuff is done to the data.
(Stuff like dividing the data by the weights, which we have already done).

CVEL assumes VLBA is the only earth centered correlator (ie for EVN data,
a correction is made for Earth rotation which is already done by the
fringe rotations).

BPASS apparently does a similar thing - it assumes baseline fringe
rotation rather than Earth centred fringe rotation.

BPASS has the option for VLBA data to make a correction for the effect the
fringe rotators have on the bandpass shape. Because the VLBA correlator is
an FX correlator (EVN XF) this would need to be done in a totally
different way - maybe it will not be possible for EVN data (it is a second
order effect).

I will sit down with my old notes on this stuff and talk to a few people
here and put together a slightly more coherent list next week.

> would help if you provided a synopsis of the perceived problems and
> a sample data tape well in advance of your trip.

I can arrange a uvfits and binary fits file of (say) an hours worth of
data - is this what you would like? I can either put it on anonymous ftp or
express post it to you? (I guess it would be 20-200 Mb).

Cheers
Chris


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