Re: Summary of October 27/28 meeting

[Richard Crutcher <crutcher@astro.uiuc.edu>]

With regard to the following point:

- polarisation calibration; at Plateau de Bure, new dual polarisation
will 
be installed; but so far no experience with polarisation calibration. 
Can experience at cm wavelengths be transposed at mm/sub-mm  wavelengths
?
Any experience with this in the US ?

We have quite a bit of experience with polarization observations and of
course calibration with BIMA: 90 GHz line and continuum linear, 
113 GHz line circular, 230 GHz line and continuum linear. I would be
happy to write a short report if you wish.

Dick Crutcher

Robert Lucas wrote:
> 
> --
> Robert LUCAS,            Institut de Radioastronomie Millimetrique
> 300 rue de la Piscine,  F-38406 St Martin d'Heres Cedex   (FRANCE)
> Tel +33 (0)4 76 82 49 42 - Fax +33 (0)4 76 51 59 38 - Tlx 980753 F
> E-mail: mailto:lucas@iram.fr                http://iram.fr/~lucas/
> 
>   ------------------------------------------------------------------------
> ALMA Science Software Requirements Committee
> --------------------------------------------
> 
> A brief summary of discussions between European Members, in Garching
> on October 27/28, 1999.
> 
> - Current membership of Committee is:
> 
> Barry Clark (NRAO)              bclark@nrao.edu
> Mark Holdaway (NRAO)            mholdawa@nrao.edu
> Robert Lucas (IRAM), chair      lucas@iram.fr
> Jeff Mangum (NRAO)              jmangum@nrao.edu
> Michael Olberg (OSO)            olberg@oso.chalmers.se
> John Richer (MRAO)              jsr@mrao.cam.ac.uk
> Peter Schilke (MPIFR)           schilke@mpifr-bonn.mpg.de
> Joe Schwarz (ESO)               jschwarz@eso.org
> Steve Scott (OVRO)              scott@ovro.caltech.edu
> Francois Viallefond (Paris)     fviallef@maat.obspm.fr
> Mel Wright (Berkeley)           mwright@astro.berkeley.edu
> 
> Ex officio:
> Stephane Guilloteau (IRAM)      guillote@iram.fr
> Al Wootten (NRAO)               awootten@nrao.edu
> 
> - We proposed to have the e-mail list open to any one interested in
> listening/contributing (since these discussions have to be open to the
> science groups). I'll send an email in this direction to S.G. and
> A.W., to be forwarded to the science groups / calibration and imaging
> groups.  We nevertheless keep the current members as responsible for
> the final reports and for telephone/face-to-face meetings.
> 
> - We proposed to set up a conference phone call between all members on
> Nov 17th or 18th at 16h UT (Europe=17-18h; USA=09-12h). Please send
> suggestions for the agenda. As opposed to the e-mail list, I think
> that for efficiency, we need to keep the attendance to
> phone/face-to-face meetings limited to Committee members.
> 
> - I think we shall probably have a face-to-face meeting in the US
> (along with the AIPS++ data pipeline meeting in January? any other
> suggestions ?)
> 
> - A short presentation was made to all software group members
> (basically a summary of what had been discussed on the email list
> before). Some questions were raised: do we include provision for the
> nutating subreflectors ? Do we need as much as 64 sub-arrays ?
> 
> - Then we met for approx. two 1.5 hour sessions. Discussion issues:
> 
> 1) Observing modes
> ------------------
> 
> - Does it make sense to observe in on the fly simultaneously in single-dish
> mode and interferometric mode ?
>   . not for continuum since the dump times are going to be very
>  different
>   . may be for line but then it may not be worthwhile since on would spend
>  generally much less time in single dish mode to recover short spacing data than
>  in interferometry. mode, additionally an Off position is needed in total power, which is
>  useless in Interferometric mode;
>   . may be one would like to do frequency switch + on the fly in which case one can
>  possibly do both SD and Int. at the same time.
> 
> - in some projects one would like to be able to switch
> frequencies/receivers quite fast; note that this is needed for
> calibration.
> 
> - add holography measurements, beam shape measurements (for thermal,
> gravitational variations) to the list of observing modes.
> 
> - add measurements of offsets between receivers (specific observing
> procedure, probably with planets).
> 
> - calibration operations: F.V. proposed that one could self-calibrate
> the pointing if the source is strong enough to obtain a map in quasi
> real time, by comparing the map obtained with all baselines related
> with one antenna to the map obtained with all baselines, or the
> current source model. Clearly more work (simulations) are needed on
> this point.
> 
> - polarisation calibration; at Plateau de Bure, new dual polarisation will
> be installed; but so far no experience with polarisation calibration.
> Can experience at cm wavelengths be transposed at mm/sub-mm  wavelengths ?
> Any experience with this in the US ?
> 
> - number of sub-arrays: we tried to see how many separate sub-arrays
> should be needed. One needs two to calibrate the atmospheric phase
> screen in real time while observations go on, and three during
> reconfigurations if one wants to use separately antennas in the
> previous (e.g. compact) configuration, antennas already in the new
> (e.g. extended) configuration) and antennas just moved to calibrate
> the baselines. For single dish operations, how many sub-arrays ?
> 
> - Do we need a pulsar mode ? ask for specs to the interested scientists
> (see science group work plan)
> 
> - Baseline calibration: not needed as soon as moved; we may wait till
> more are available provided the antennas without known precise
> positions are flagged as such in the on-line phase calibration.
> 
> - Operators' needs should be included as well, not put in only later as
> an afterthought (B. Glendenning).
> 
> 2) Astronomer input at proposal submission and after acceptance/Scheduling
> --------------------------------------------------------------------------
> - Astronomer input should be in two steps: one before proposal
> evaluation, one after the proposal is accepted to specify actual
> observing modes, position and frequency data, ... This `Phase I, Phase
> II' concept is is use on, e.g., HST and the VLT.
> 
> - interactive scheduling should be used only for maintenance/tests and
> time specific observations (ephemeris sky events). Here interactive
> scheduling means the mode in which the astronomer is given real-time
> control of the instrument.
> 
> - automatic scheduling:
>  . Phase II tools should produce typ. 15-minute blocks to enable
> interruptions due to weather, priorities changing with LST, ...
>  . the PI may set breakpoints where he/she wants to see the data
> before going on. However there is the danger of `cheating' by the
> astronomer (changing objectives if observations are not
> successful). Probably we need some control by one staff astronomer.
> In that case the should be fast enough (at most a few days), if we
> have continuously evolving configurations.
> 
> - does automatic scheduling imply guaranteed data quality ? probably yes.
> sensitivity limit should be specified at input, and considered in
> proposal evaluation.
> 
> 3) On line data pipeline: How far can this be automated ?
> ---------------------------------------------------------
> 
> The consensus seemed to be that one could probably do more with
> interferometric data than with single dish data (spectral baseline
> removal) and for mixing short-spacing with interferometer data.
> 
> - How often should interferometer maps & total power maps be produced ?
> 
> 4) Other
> --------
> 
> - The system must be able to dump raw correlator data for
> test/engineering use, when needed.
> 
> - Will Doppler tracking be done in hardware or software ?

-- 
Richard M. Crutcher
Chair, Department of Astronomy
University of Illinois
Voice: 217/333-9581
Fax: 217/244-7638
Date: Thu, 27 Jan 2000 11:40:45 +0100 (MET)
To: lucas@iram.fr
From: Majordomo@web3.hq.eso.org
Subject: Majordomo file: list 'alma-sw-ssr' file 'alma-sw-ssr.991112'

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