Re: VLBI interest in MIRA (xNTD)
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From: <Chris.Phillips_at_email.protected>
Date: Thu, 8 Mar 2007 20:39:52 +1100 (EST)
Hi Simon,
Presumably putting in a "simple" focal plane array somewhere early on it
the beam waveguide optics would allow you to focus the signal without
going through all the waveguides which kill the L-band signal. Probably
not an affordable option but would be a nice way to do it
Cheers
Chris
On Thu, 8 Mar 2007, Simon Ellingsen wrote:
>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 20:40:17
Date: Thu, 8 Mar 2007 20:39:52 +1100 (EST)
Hi Simon,
Presumably putting in a "simple" focal plane array somewhere early on it
the beam waveguide optics would allow you to focus the signal without
going through all the waveguides which kill the L-band signal. Probably
not an affordable option but would be a nice way to do it
Cheers
Chris
On Thu, 8 Mar 2007, Simon Ellingsen wrote:
>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 20:40:17