The enhanced Agenda from last month's meeting is available.
Action Items Science IPT telecon Feb. 11, 2003
- Polarization widget:
Christine to e-mail to polarization experts to ask input on central
frequency. This has been done, and comments have been received from
several people (to be posted on the mmimcal web page?). The
project scientists will make a recommendation, to be reviewed by the
Al to ask Steve Myers whether wider bandwidths can be used, using the
methods developed at lower frequency by Carlstrom et al.
- Single antenna design:
Scientific areas which benefit most from a single design (i.e. exactly
same beam pattern etc.) are polarization and mosaicing, but the
scientific loss if the antenna's are not identical is hard to
quantify. Operational costs will undoubtedly be higher if there are
two types of antennas, which will impact science indirectly by
leaving less money for other science-related items. This was thought
to be a very serious concern. All to send to Stephane a summary of
their comments. Stephane to transmit these concerns to the JAO.
- Fast switching tests:
Marc Holdaway's updated note to be posted on mmaimcal. Please send
somments in the next week.
Lars-Ake et al. to submit memo in the next weeks on error analysis on
water vapor and delay from 183 GHz data following Delgado's work.
New weather data from Cerro Negro considered to be interesting to
obtain advanced warning of weather changes (~30 min up wind), but not
high priority to work on. Suggestion is to look first at differences
between Chajnantor and down wind (e.g. Pampa La Bola) as test, and
also at new report from Sarazin on satellite data.
See minutes from telecon February 7. Dual load tests show rapid
variations with time and temperature. First semi-transparent vane
tests to occur in early May. New absolute calibration scheme by Jack
Welch considered interesting, if it can be done at 90 GHz rather than
30 GHz. Stephane has made a revised plan, and Bryan and Stephane to
pursue this further. All to send comments to Stephane on plan.
Stephane confirms that compact array should be designed to 15.15m and
urges John to submit document to ALMAEDM. The reconfiguration sequence
can be a separate document to ALMAEDM.
Mark to continue optimizing Y+ array with fewer additional stations
(more pads in common with John's array) along the lines outlined in
the telecon, i.e., reasonable compromise between highest angular
resolution and acceptable sidelobes.
Most urgent here is the question from Steve Scott about the data rates
for the enhanced correlator. All science IPT members to review Steve's
notes and send comments to project scientists in the next week. Main
question is whether the proposed increase in the AVERAGE data rate
from 4 to 8 MB/s is O.K. This would mean that any project which needs
a higher average data rate has to specify it at the proposal stage.
Please think about this from the perspective of the science you would
like to do, e.g. line surveys, high-redshift CO blind searches which
use the full bandwidth at relatively high spectral resolution, ....
Jerome Pety reported that the Japanese simulations are progressing
well and that transfer of expertise has been successful. See the PS
plot of (image and uv plane) fidelities as a function of the SNR for
the m51ha test image on
http://www.cv.nrao.edu/~awootten/mmaimcal/scipt11feb03.html. From the
fidelity definition, fidelity values will always be lower than the
SNR. Here the SNR is defined as the Image peak intensity / theoretical
noise, where the theoretical noise is deduced from the integration
time and Tsys . The interpretation of the results is not
obvious. Indeed, depending on the image properties (for instance its
dynamic) the number of pixels whose intensity is below (i.e. not
detected) or above (i.e. detected) the noise for a given SNR ( may
vary a lot. This effect will affect a lot the median fidelities
computed in the image plane.
The question from Jerome to the Science IPT is: what is the range of
SNR that is expected for real science cases for such simulated images?
"What typical range of SNR can be expected to access to the scientific
goals for each of the standard images used in the memo #398 about ACA
All to send comments to the project scientists in the next week.
The NA Imaging and Calibration Group has held several meetings; agendas for
those may be examined at:
- Soon-to-be-final Level 3 milestones from Bryan Butler: "Included are the
modifications based on the calibration group telecon on December
16 and the Leiden meeting."
- Project news/updates;
ALMA Board met, signed agreement.
Software IPT Preliminary Design Review
will be held in Tucson 18-20 March 2003.
AMAC Meeting 24-25 March Socorro
ASAC Face-to-face Meeting 2-3 April 2003 in Grenoble, France at IRAM.
May 26/27 ALMA Board face-to-face (Europe)
ALMA Week 2 June Victoria
Several of the below items were also discussed at length during the recent
mmaimcal and calibration telecons, but it is important to have the
input and comments of the entire science IPT before recommendations
are made to the project/ASAC.
See ImCal and Calibration for background information on some of the above items.
- Polarization widget: central frequency? See material at ImCal, above. (Stephane/Al)
- Scientific benefits of a single antenna design. See Report. (Stephane/Al)
- Fast switching tests. See material at ImCal, above. (Mark Holdaway)
Reports from Subgroups
- SSR: fast data rate: have we reached a conclusion? Mel Wright's comments.
"We would like input from the Science IPT before making
this proposal and hope that you will help us. I have attached a document
(EnhancedCorrelator.pdf) that attempts to make some assumptions to distill
out reasonable constants in the data rate equation. If these are accepted at
face value, the main unknown in the average data rate is the number of
channels. The second attachment (DataRates.pdf) is our previous request for
a rate increase. It contains more background material and examples that are
not duplicated in the newer document."