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Re: Fwd: VLBI and MIRANdA

From: <Chris.Phillips_at_email.protected>
Date: Fri, 13 Apr 2007 14:46:11 +1000 (EST)

Hi Steve,

My few cents worth. Firstly the main issues:

  2.4 GHz is definitely not written off for MIRANdA yet (though I admit it
  it low probability). Unless we can put in a strong case here now it
  certainly will not happen. I think at the minimum a section is needed
  arguing why 2.4 GHz is needed. I think Tasso covered the main issues.
  I would remove the section suggestion adding L-band to Ceduna. Probably
  adding some uv plots with MIRANdA with LBA+Hart+NZ clearly shows the
  benefit of 2 GHz on MIRANdA.

  Throughout the text is discussion about the problem with FOV. I would cut
  this from all the science discussions entirely and add some comments in
  the wide-fov section. A lot of standard VLBI science is happy with 5" fov
  so making a point of it distracts from the main arguments.

Some more general stuff:

Overview (and later):

"The later application means that MIRANdA is not used as an element of the
LBA". This should be removed or reworded. MIRANdA does not *have* to be
used for the VLBI followup but maybe we would want to. You see to be
ruling it out - I would start initially assuming we would include MIRANdA
(at 2.4 GHz!) in the followup obs.

Introduction:

MIRANdA will have roughly twice the Tsys of Parkes. So it is closer to a
45m in sensitivity.

"all existing telescopes are concentrated in the south-east". Ceduna is
not in the south-east. This statement should be reworded.

OH masers:

Remove all the "~" characters.

Pulsar parallaxes:

"The LBA is the only existing Souther VLBI array which is sensitive enough
to..." Which *other* Southern VLBI arrays is being compared to...

Imaging over wide fields:

"The currently proposed 200 element FPAs have the potential to form up to
50 independent beams..."

There is *no* way we are going to be able to do vlbi on each of these 50
beams (unless all the other telescope data can be shipped to and processed
on the MIRANdA correlator). You probably want to say we would want to look
at a handful of sources in the full fov.

MIRANdA and PAHMELA

         PAHMELA => PAMHELA

We should be pushing for MIRANdA as an extension to PAMHELA. This is meant
to be an SKA demonstrator. If we cannot do evlbi to MIRANdA we
demonstrating long haul connectivity in Australia is a problem.

Transient detection with MIRANdA and trigger criteria:

4. "Is a 1.6 observation currently possible at Parkes". Drop "the ATCA and
Mopra". That should rarely be a problem.

evlbi capabilities and example science:

"Phillips, Deller etal 2007, in preparation" -> "submitted" :-)

---------------------------------------------------
2.4 GHz for MIRANdA

A few more comments on S-band for MIRANdA. I have been playing with the
sensitivity calculator and the science drive is not totally clear cut.

  - The WA AusScope antenna Yarragadee fills in pretty much the same uv
    spacing as MIRANdA.
  - MIRANdA adds little to sensitivity over Yarragadee (e.g. 23 uJy image
    RMS cf 19 uJy, or 11 uJy cf 10 uJy with Tid included). This is with
    1/sigma^2 weighting. However I have noticed you loose all your
    resolution with 1/sigma^2 weighting and with no weighting you get
    a much smaller beam and MIRANdA halves the image sensitivity.

An antenna in WA *and* NZ makes a big difference to observations to Hart.
The plus for MIRANdA over Yarragadee is baseline sensitivity. This allows
detection of weak sources on more baselines with *will* improve
calibration and this will probably have a much larger sensitivity
improvement on the raw SEFD numbers. This is particularly important on the
longer baselines.

Cheers
Chris
Received on 2007-04-13 14:46:26