From: <David.Jauncey_at_email.protected>
Date: Fri, 23 Mar 2007 13:21:43 +1100

Dear Steven,

Thanks for your e-mail re "MIRANdA", or whatever the xNTD wants to be
called these days.

One particular item you may well wish to mention is the possibility of
using it with RadioAstron. The mission seems finally to be heading for
an '08 launch, and assuming that the Australian 18 cm receiver still
works after 15 years sitting in an office in Moscow (???), RA will offer
18 cm as one of its frequencies.

The real push for 18 cm is the ability to be able to measure the
scattered sizes of a bunch of scintillators, as 18 cm is well in the
regime of strong scattering. If you have the scattered size at 18 cm and
the measured characteristic time-scale, you can derive the screen
distance by assuming an ISM velocity, V_ISM. Given an annual cycle
measurement, then you may even have a good estimate of V_ISM. It is
expected that the scattered size. Moreover, with a 300 MHz spanned
bandwidth, you can confirm the Lamda^2 time-scale behaviour directly
with MIRANdA, or whatever it's called.

As scattering is a stochastic process, the scattered size should be at
most a 2-dimensional Gaussian, so high quality imaging is not all that
necessary. So a couple of big telescopes in the south like Parkes and
MIRANdA, plus the smaller ones across Oz, would give, with the space
baselines, the necessary zero-spacing flux density and angular size as
well.

If you want an argument to support of building a southern hemisphere
tracking station for RA, this is about the best I can think of. In an
"interesting" way, measurements at the longer wavelengths can provide
particularly higher resolution than say those at 5 GHz.

Better yet, why not just hive off one of the MIRANdA 12 m antennas and
make it a tracking station for BOTH RA and VSOP-2?

I've cc-d J-P for his interest, too.

Cheers from a beautiful sunny spring day in Japan,

Dave

-----Original Message-----
From: owner-vlbiobs_at_atnf.<!--nospam-->csiro.au [mailto:owner-vlbiobs_at_atnf.<!--nospam-->csiro.au]
On Behalf Of Steven Tingay
Sent: Friday, 23 March 2007 9:35 AM
To: VLBI observers
Subject: Science case for VLBI and MIRANdA

Dear All,

Following on from the MIRANdA (formerly known as the xNTD, MIRA etc
etc) science meeting last week, Simon Johnston is putting together a
revised science case for MIRANdA. He has asked me to lead the
write-up of the science case for VLBI using MIRANdA. I'd like to ask
for some contributions from you folks, perhaps half a page of text on
any areas of VLBI science for which you think MIRANdA would be useful.
 I was hoping to finger a few people as follows:

L-band masers: Phillips/Ellingsen
IDV and AGN: Lovell
Wide-field VLBI: Lenc
Pulsar parallax: Deller/Dodson
Transients: Tingay
Space VLBI: Edwards

Please let me know if you are able to do this. If anyone else has
something else to contribute, please feel free. I'll need text by
about April 10th.

To help give you some idea of the uv coverages, beam, and imaging
sensitivities possible using MIRANdA for VLBI, Adam has added MIRANdA
to his online sensitivity calculator. It is located for the moment
at:

http://astronomy.swin.edu.au/~adeller/software/lba

Additional relevant information is that MIRANdA will likely be 30
antennas of 12 m diameter. Used as a phased array they should give a
Tsys of approximately 50 Jy at L-band (these numbers are incorporated
into the sensitivity calculator). The maximum baseline for MIRANdA
will be approximately 8 km. The maximum bandwidth will be 300 MHz.
Multi-beaming may be possible for VLBI observations, to increase the
FoV beyond a single phased array beam.

As a note, Adam has also added the 3 Australian NCRIS geoscience 12 m
antennas to the calculator, as well as the 4th geoscience 12 m antenna
of AUT. So, you can start looking at how the LBA uv coverage will
improve with the addition of these antennas. It is a substantial
improvement!

Thanks and Cheers, Steven

P.S. Just a reminder to let me know if you are able to make our next
operations meeting at Swinburne on April 26 and 27.

-- 
* * * * * * * * * * * * * * * * * * * * * * * * * *
Assoc. Prof. Steven Tingay
Swinburne SKA Project Leader
Centre for Astrophysics and Supercomputing
Faculty of Information and Communication Technologies
Swinburne University of Technology
Mail H39
P.O. Box 218
Hawthorn, Vic 3122
Australia
Ph     +61 (0)3 9214 8758
Fax    +61 (0)3 9214 8797
Email  stingay_at_astro.<!--nospam-->swin.edu.au
          s.tingay_at_optusnet.<!--nospam-->com.au
          Steven.Tingay_at_gmail.<!--nospam-->com

Received on 2007-03-23 13:22:00