Re: VLBI interest in MIRA (xNTD)
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From: <Chris.Phillips_at_email.protected>
Date: Thu, 8 Mar 2007 20:37:35 +1100 (EST)
>FromSimon....
---------- Forwarded message ----------
Date: Thu, 8 Mar 2007 15:45:02 +1100
From: Simon Ellingsen <Simon.Ellingsen_at_utas.<!--nospam-->edu.au>
Subject: Re: VLBI interest in MIRA (xNTD)
Hi Steven,
>I think 2.4 GHz is important for the xNTD for VLBI. At 1.4 GHz we do
>not have Ceduna, which means that uv coverages at 1.4 GHz which use
>the xNTD will have a very large gap between the east-coast baselines
>and the baselines between east and west coasts. This is not good for
>calibration or high dynamic range imaging.
>
>At 2.4 GHz having both Ceduna and the xNTD will make a big difference.
>Yesterday I was generating uv coverages for my VLBI/MIRA talk next
>week, and the benefit of having both Ceduna and xNTD in the array is
>substantial.
>
>I guess an alternative would be to get 1.4 GHz on Ceduna. I assume
>that this is difficult, as it has not been done yet.
1.4 GHz at Ceduna requires a prime focus installation at that
frequency which requires moving the subreflector out of the way. Its
not insurmountable, but it would be expensive and to date no one has
wanted it enough to come up with the funding to make it happen.
Putting an adjustable subreflector on Ceduna would also have benefits
for 22 GHz operation.
The other point to make long this line is that 2.4 GHz is likely to
be the lower frequency range for the AuScope antennas. The broadband
feeds that will be used for VLBI2010 observations wont go below 2 GHz
because they need to get beyond 10 GHz at the top end. So from the
point of view of maximising the LBA for astronomy 2.4 GHz is highly
desirable.
Regards
Simon
Date: Thu, 8 Mar 2007 20:37:35 +1100 (EST)
>FromSimon....
---------- Forwarded message ----------
Date: Thu, 8 Mar 2007 15:45:02 +1100
From: Simon Ellingsen <Simon.Ellingsen_at_utas.<!--nospam-->edu.au>
Subject: Re: VLBI interest in MIRA (xNTD)
Hi Steven,
>I think 2.4 GHz is important for the xNTD for VLBI. At 1.4 GHz we do
>not have Ceduna, which means that uv coverages at 1.4 GHz which use
>the xNTD will have a very large gap between the east-coast baselines
>and the baselines between east and west coasts. This is not good for
>calibration or high dynamic range imaging.
>
>At 2.4 GHz having both Ceduna and the xNTD will make a big difference.
>Yesterday I was generating uv coverages for my VLBI/MIRA talk next
>week, and the benefit of having both Ceduna and xNTD in the array is
>substantial.
>
>I guess an alternative would be to get 1.4 GHz on Ceduna. I assume
>that this is difficult, as it has not been done yet.
1.4 GHz at Ceduna requires a prime focus installation at that
frequency which requires moving the subreflector out of the way. Its
not insurmountable, but it would be expensive and to date no one has
wanted it enough to come up with the funding to make it happen.
Putting an adjustable subreflector on Ceduna would also have benefits
for 22 GHz operation.
The other point to make long this line is that 2.4 GHz is likely to
be the lower frequency range for the AuScope antennas. The broadband
feeds that will be used for VLBI2010 observations wont go below 2 GHz
because they need to get beyond 10 GHz at the top end. So from the
point of view of maximising the LBA for astronomy 2.4 GHz is highly
desirable.
Regards
Simon
-- Simon Ellingsen : Senior Lecturer Physics & Astronomy, University of Tasmania email : Simon.Ellingsen_at_utas.<!--nospam-->edu.au WWW : http://www-ra.phys.utas.edu.au/~sellings Phone : 6226 7588 ; Area Code : +61 3 (International) 6278 8636 (Home), 6226 2410 (Fax) 03 (Australia)Received on 2007-03-08 20:37:35