From: <c.reynolds_at_email.protected>
Date: Mon, 22 Mar 2010 14:44:31 +0800

hi Richard,

I've taken a look at the vx014b data to investigate the 'Ceduna
problem', and have been unable to reproduce your plot showing Ceduna
going funky when the Hour Angle changed sign
ftp://ftp.atnf.csiro.au/pub/people/vlbi/incoming/CEDUNA_ODD.PS.

Please take a look at:
ftp://ftp.atnf.csiro.au/pub/people/vlbi/incoming/CEDUNA_NOTODD.PS
to see my results. Ceduna looks quite well behaved in its rates and
delays. The SNR is not really good enough to determine if it is
exhibiting the very short timescale phase wander that has been the
hallmark of this problem so it's not a great dataset for diagnosing
that particular problem.

Are you sure your data were from vx014B? Did you do some additional
processing before running fring? Could you possibly run 'md5sum' on
your fits file and send me the results so I can compare it with the
file on our archive to check for possible data corruption?

cheers,
Cormac.

On 5 March 2010 05:30, John Dickey <John.Dickey_at_utas.<!--nospam-->edu.au> wrote:
>Dear Richard,
>
>  That is odd behavior.  But I only have one plot, did you attach more?  The
>one I got is 4.2 Mby, a bit much for just 25 or 30 points to display.  There
>seem to be frequent jumps from low rate to high rate, but both are pretty
>consistent.  A wrap problem is possible, but we just replaced all the
>cables, all the way from the receivers to the control room.
>
>  Anyway, if there were more figures in your mail, could you please compress
>them and resend?  Thanks for your help.
>
>cheers,
>jd
>
>On 05/03/2010, at 2:00 AM, Richard Dodson wrote:
>
>>Hi Tassie-siders
>>
>> You must tremble every time I get some data. Here is something from
>>VX014B which _might_ help with the Ceduna problems.
>>
>>  After a few steps to remove basic instrument offsets I get these
>>residuals.
>>
>>  See how Ceduna has a high rate about 1/2 the time? (page 1, PL 4).
>>I thought at first that a source must have a very bad position, or
>>that the antenna position must be bad and only sensitive to some
>>source coordinates.
>>
>>  But compare that to Ceduna (and everyone else) plotted against
>>Hour Angle. When HA is negative rates are low. When HA is positive
>>rates are high. (page 2 PL 2, page 3 PL 3).
>>
>> Odd behaviour at Ceduna - Who would have believed it?
>>
>> I am guessing that what we see here is a change of rate when the
>>wrap changes, which I guess means that something is getting stretched,
>>but I don't see what that would introduce a rate change.
>>
>> Phases are fine pre-HA=0, all over the shop post HA=0. (page 4, PL 5
>>for amplitude RMS, page 5 PL 7 for phases).
>>
>>
>>  Have fun with this info!
>>
>>              Richard
>><CEDUNA_ODD.PS>
>
>

-- 
----------------------------------------------------
Cormac Reynolds
Phone: +61 8 9266 3785
Fax: +61 8 9266 9246
email: c.reynolds_at_curtin.<!--nospam-->edu.au
----------------------------------------------------

Received on 2010-03-22 17:45:20