[asac] letter to ASAC (fwd)

[Karl Menten]

Dear ASAC members,

On behalf of the ALMA Science Software Requirements Committee, Robert 
Lucas has produced the attached document with questions of the SSR 
regarding a number of important issues. Please send me your opinions on
these issues so that I can collect them and we can start discussing them
at the upcoming ASAC telecon.

Cheers,
	Karl

-----------------------------------------------------------------------------
Dr. Karl M. Menten   (kmenten at mpifr-bonn.mpg.de)
Max-Planck-Institut fuer Radioastronomie
Auf dem Huegel 69, D-53121 Bonn, Germany
Tel.: +49 (0)228-525297 * Fax: +49 (0)228-525435
-------------- next part --------------

to ALMA Project Scientists and Alma Science Advisory Committee Members:
-----------------------------------------------------------------------

Object: Project-wide issues of specific interest to Science Software
Requirements


  During our past six months of work in the Science Software
  Requirements Committee we have encountered several issues on which
  we agree that further input on your side will be needed before our
  work can be completed. Our preliminary report (ALMA memo 293) has
  been recently officially reviewed and we take this opportunity to
  raise the following questions. These are mainly issues related to the
  way ALMA is operated as a whole. For each issue we would like to
  have either a definite answer or a baseline/fall-back
  alternative. The questions are given in order of decreasing importance.

1) Array Scheduling

  We have been assuming that ALMA will be dynamically scheduled so
  that each project is observed during weather conditions (seeing,
  opacity, wind) that allow its objectives to be achieved. This
  implies dynamic scheduling in near real time (Dynamic Scheduling) as
  stressed in mma memo 164, and in ALMA Project Book, Chapter
  2(III.4). This has implications on the feedback from the PI, on the
  basis of calibration data and images produced by the pipeline: this
  feedback can only be offered at the end of one transit (observing
  session), assuming the project observations are divided into several
  transits either due to schedule optimization (as high elevations are
  preferred) or intentionally by the insertion of breakpoints. This
  limitation on `interactivity' has to be realized. We believe it is a
  small price to pay for the increase in productivity expected from
  dynamic scheduling.

  An alternate scheduling method is the traditional interactive
  observing, which should be available since it can be useful for test
  purposes and for special -- timely and unforeseen -- observations.

Our question: Is dynamic scheduling to be the default mode of
  scheduling, accepting the restricted interactivity implied by this
  mode ?

2) Purpose of the pipeline
 
  The data flow ALMA Project Book, Chapter 2(III.5) will include a
  pipeline that may be used to  fulfill several purposes:
 
  a) check that the data obtained can be calibrated, with feed back to
    the observing process to use the optimal phase calibration cycle.

  b) give feed back to the dynamic scheduler by monitoring the observed
    phase noise.

  c) produce calibrated uv data and maps of test quasars to check in
    real-time the quality of observations, with feed back to the
    dynamic scheduler.
  
  d) produce calibrated uv data and maps of the project source(s) to
    enable the PI to evaluate her/his data at the end of the observing
    session and to proceed with scientific interpretation when the
    project is finished (after improved reduction if needed), while
    incrementing the ALMA data archives.

  e) use calibrated uv data and maps of the project source(s) in order
    to derive simple quality parameters (noise level, signal to noise
    ratio) that may be used to define when the project goals are
    attained.

  f) use calibrated uv data and maps of the project source(s) in order
    to derive similar or more sophisticated parameters (source size,
    number of sources ... see examples in memo 293) to be fed back
    into the project's observing process, which may then take
    automatic decisions.

  While we believe that a, b, c and d should be implemented as
  baseline features, there is some concern that f) and maybe e) might
  be too ambitious goals (software has a cost too) or even may
  increase the distance between the astronomers and the instrument to
  an unwanted level.

Our question: Which degree of sophistication should be set as a goal
for the ALMA data pipeline ?

3) Operational aspects

  For the specification of GUI (graphical User Interfaces) a clear
  description of the relative duties of the operators and local staff
  astronomers will be needed, in view of the following tasks 

  - Allocation of antennas to simultaneous projects (e.g. a sub-array
    for calibration, a sub-array used for astronomy, some antennas in
    maintenance) ?
 
  - Control on the dynamic scheduling process

  - Communication with the PIs if needed 

Our question: Can the relative duties of the staff in charge of
controlling the array be already outlined ?

  
4) Policy on data propriety:

  We are assuming, as is the usual practice in most observatories,
  that only the proposing team has access to the data during a limited
  proprietary period and that the data ultimately become public. The
  actual length of the propriety period can be probably be set later,
  but some policy questions may affect the software requirements, such
  as:

  4.1 is only the scientific data covered, or all header information
  including monitoring data, or some header information only
  (like coordinates and frequencies) ?

  4.2  if public data is reprocessed in the pipeline by others, to search
  for unforeseen scientific results, does this start a new proprietary
  period ?

Our question: Can the proprietary data policy of ALMA be already
outlined ?


5) Special modes

  Some specific observations (Sun, Pulsars, ...) may need very short
  integration times, fast frequency changes, ... for which the exact
  scientific software (and hardware ?) requirements need to be
  investigated in detail. For these issues we would like having
  specialized astronomers as correspondents, so that we may include
  their contributions in our requirements, in a coherent manner.


6) Other details

  - is an audio channel from the antenna cabins to the operator
    planned ? (see comment 95)

  - We assume, as DSB mode is clearly an option for some frequency
    bands, that side band separation has to be handled by software for
    interferometric work in those bands.



Robert Lucas,

on behalf of the Science Software Requirements Committee