ALMA SSR Committee Berkeley Meeting, 12-13 October 2000 Attended by: B. Clark, R. Lucas, J. Mangum, S. Myers, S. Scott, M. Wright, P. Schilke (members) B. Glendenning, J. Schwarz (ex officio) D. Muders, G. Harris (Analysis Group)

Minutes

1. Status of General Use Cases and Comments (UC Writing group)
   • A deadline for entering programme technical data in phase II seems necessary for practical reasons; but there is of course no deadline for updating this data.
   • The existence of a purge period for projects accepted but not started is clearly a policy issue. Let's for the time being assume that there is one (about 1 year or one scheduling period).
   • We precised that what is allocated to a project is a level of sensitivity in required atmospheric seeing conditions, and not a fixed amount of time (though a hard limit on the total integration time must be specified to avoid overflowing if the actual sensitivity has been misestimated). This policy will be stated in the requirements.
   • The Use Cases will be updated by the UC group.
2. Status of Observing Modes Use Cases (UC Writing group)
   Use Cases drafts for about half of the observing modes / calibration modes were presented and discussed. Updates will be made by the authors.
3. Data Rates summary and Data Storage format (S. Scott) Steve presented the document he had sent with S. Myers a few days in advance.
   • We shall store the visibilities as cross-correlation coefficients. They will have to be multiplied by stored system noise spectra to get Ta* scale and by stored Jy/K values to get visibilities in Janskys.
   • There is no need to include weights/channel in the base-line based data since those weights are involving system temperatures and are thus antenna-based. We shall instead keep a system noise (Tsys) spectrum for each antenna and band.
   • Switch between 16-bit and 32-bit precision should be automatic (based on signal strength) and at the baseline and spectrum level.
   • We shall keep a spectral average of each sub band with a high time resolution (i.e. resolving the atmospheric fluctuations) whatever is the actual intergration time for the spectral data. This allow a check for atmospheric phase fluctuations using the source continuum if present.
   • The requirement on data rate would be more clearly specified in terms of visibilities per second.
4. Requirements List and priorities discussion
   • We decided on four priority levels:
     • 0: Essential
     • 1: Needed for interim science (use by experts)
     • 2: Needed to open the system to general users
     • 3: Desirable
   • In the Pipeline section me must clearly distinguish the three pipeline uses that have different priorities: calibration, quick look, and science data processing.
5. General discussion on working procedures
   • The face to face meetings are more efficient that the phone meetings, but they seem too infrequent. We'll try to increase the frequency of face to face meetings to 3/year. Their duration should be kept within two days but could be prepared by subgroup meetings in the preceding days.
   • The phone meetings should be more focused on one or two issues per meeting.
   • Deadlines should be more clearly stated for each action item.
6. Future meetings:
   • Next phone meeting fixed for November 6, 16h UT.
   • A face to face meeting is foreseen in February 2001 (in Europe).

Action List

1. Analysis group to revise the General Use Cases based on comments and replies;
2. R. Lucas to include priorities in requirements list;
3. R. Lucas to draft a precise specification for Scheduling Blocks;
4. G. Harris to weekly keep an up-to-date copy on the Use Cases on a freely accessible (no password) URL;
5. Observing Modes mini-groups to continue writing observing mode Use Cases (modes not yet drafted are in bold face):
   1. Gareth Harris, Barry Clark, Steve Scott, Jeff Mangum
   • Multi-Field Mosaic (Interferometric)
   • Amplitude Calibration (Total Power)
   • Flux Calibration (TP or Interferometric)
   2. Robert Lucas, Francois Viallefond, Mel Wright
   • On-The-Fly Mosaic (Interferometric)
   • Delay Calibration (Interferometric)
   • Pointing Calibration Session (TP and Interferometric)
   3. Dirk Muders, Peter Schilke
   • On-The-Fly Mapping (Total Power)
   • Bandpass Calibration (Interferometric)
   • Baseline Calibration (Interferometric)
   4. Joe Schwarz, John Richer, Robert Lucas
   • Position Switched Mapping (Total Power)
   • Phase Calibration (Interferometric)
   • Beam Shape Calibration (TP and/or Interferometric ?)
   5. Rein Warmels, Jeff Mangum, Steve Myers, Steve Scott
   • Frequency Switched Mapping (Total Power)
   • Pointing Calibration (TP and Interferometric)
   • Polarization Calibration (TP and/or Interferometric ?)

Documents

• Version 1 report: http://iraux2.iram.fr/%7Elucas/almassr/report-1/report-1.html
• Drafted Requirement List: http://iraux2.iram.fr/%7Elucas/almassr/requirements/requirements.ps
• General Use Cases: http://groupware.eso.org:8000/bscw/bscw.cgi/0/78225
• Use Cases Comment List: http://groupware.eso.org:8000/bscw/bscw.cgi/d93552/SSR-UC-Comments.html