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Re: VLBI and MIRANdA

From: <adeller_at_email.protected>
Date: Fri, 13 Apr 2007 10:36:25 +1000 (EST)

Hi Steve,

I agree with Tasso that it is worthwhile listing the numerous advantages
that would come with a 2.3 GHz capability for MIRANdA. We'll never get it
if we don't squeak loudly enough...

On the field of view question, its difficult when the configuration has
not been pinned down, but surely we could tie only a subset of the most
closely spaced antennas if FOV was a concern and multibeaming was not
available. This could be mentioned at the end of the paragraph in the
introduction which begins "If it is possible (given the multi-beaming
capabilities of MIRANdA) to form multiple, independent phased arrays from
MIRANdA...".

Something like, "For observations which are not sensitivity limited but
require a large FOV and the uv coverage of MIRANdA, the option exists to
tie a subset of more closely spaced antennas, sacrificing a small portion
of collecting area to increase FOV" might be appropriate. It could then
also be mentioned again in the first paragraph of the section "MIRANdA as
a component of the Australian VLBI array".

Cheers,
Adam

On Fri, 13 Apr 2007, Tasso Tzioumis wrote:

>Steven mate,
>
>Thanks for the opportunity to comment on this. Unfortunately I missed most of
>the science workshop due to other commitments and did not have a chance to
>contribute to this. So here are a few comments:
>
>1. The question of MIRANDA configurations and field-of-view questions are
>covered extensively in the text but not in your introduction/summary up-front.
>I think it will be good to mention this there for those who do not read the
>details. From the introduction I've got the impression that this was a huge
>and unsolvable limitation, where in the later text the discussion is much
>better balanced.
>
>2. In the evlbi section you need to mention U. Tas. explicitly as an equal
>partner. It is probably an oversight from an earlier version without Hobart.
>
>3. In the introduction, L-band in Ceduna is mentioned. It may be cheaper to do
>but I cannot see where the funds will come from, so I do not think it'll ever
>happen.
>
>4. And this brings me to the main point, about 2.4 GHz capability on MIRANDA:
>I was not in the discussions but I think we are giving up on that too early
>and too easily. I think there are many reasons to have 2.4 GHz, at least on
>bits of MIRANDA.
>On uv-considerations we have:
>- Ceduna is the obvious one (and I do not think L-band will happen there
>unless we can find some new source of funding).
>- there are also the AuScope antennas, especially Katherine, that will fill in
>the uv very well
>- the NZ antennas which will provide 6000km baselines to MIRANDA, doubling the
>resolution
>- filling in the uv gap to South Africa. The 9000km baselines will now reduce
>to 6000km baselines. And if the in-between spacings are filled by NZ, then the
>uv would be phenomenal.
>- other tracking antennas e.g. New Norcia and the APT antennas in Japan and
>China.
>With all those antennas, then MIRANDA may look more like an SKA pathfinder...
>So, I think 2.4 GHz opens up huge possibilities for VLBI and even eVLBI.
>
>Even if only a subset of the MIRANDA antennas are fitted with the S-band
>receivers, the gains will be very large.
>
>Then are other possibilities like tracking spacecraft as we did with Huygens.
>Again, a big equivalent antenna in WA will complement our other antennas in
>the East coast by providing both uv and time coverage.
>
>I think the impact on VLBI and the science we do with it will be large if
>MIRANDA was extended to 2.4 GHz and the possibility is not even seriously
>addressed here. I feel we need to make the case as strongly as we can, even if
>it appears that it is not possible under the current MIRANDA parameters.
>
>Cheers for now
>Tasso
>
>
>

!=============================================================!
Adam Deller Ph +61 3 9214 8502
SKA Group Fax +61 3 9214 8797
Centre for Astrophysics and Supercomputing
Swinburne University, Hawthorn VIC 3123, Australia
!=============================================================!
Received on 2007-04-13 10:36:44