Sci IPT telecon 28 May 2008.
Hills, Peck, Brogan, Indebetouw, Hunter, Mangum, Reid, Richer, Nikolic, Emerson, C. Wilson, Nyman
The meeting was conducted according to the not entirely satisfactory agenda Al posted at https://safe.nrao.edu/wiki/bin/view/ALMA/28May08Agenda
Some links to material refer back to postings in the almasci archive but access to this material requires one to know one's almasci password, a problem for some members.
Some problems with attachments were repaired by Al during the course of the telecon.
Richard reviewed the project status, illustrated by the slides he provided which were attached to the agenda.
Richard reviewed the ASAC charges along with the recent Board meeting actions relevant to the science IPT.
A discussion was held on Band 10. Current technology will not allow development of a receiver with frequency coverage from 787-950 GHz. The current spec is six photons over 80% of the band (Trx~230K), with 8 photon noise over the remaining 20% (Trx~334K). An illustration of the atmospheric opacity including all major species shows that important lines identified by the ASAC in 2001--HCN, HCO+, CO, [C I] all lie in the lower part of the band. Is coverage of this smaller portion of the band at the specification sensitivity scientifically useful? The ASAC also identified the ionized carbon line at redshifts of 1 to 1.4 as compelling but no more complete case has been written for this. Wootten mentioned he would discuss this in a short note. Brogan noted the best transmission occurs mid-band and expressed a desire for coverage there for continuum, as the highest ALMA resolution is achieved in this band; the protoplanetary disk case focuses on this band and the atmosphere is most difficult to deal with at this frequency. Discussion continues.
The status of the extended configuration redesign was discussed. Reid presented some simulations showing the difference in sampling of the M31 HII region image between two arrays; holes in uv coverage in this 4 hour dataset are clear. Richard noted the cost of changing the design could be about $1M so the case must be compelling. Brogan mentioned including atmospheric noise. The current spec can meet the demands of the third science goal in the bilateral agreement, Rob stated. It was decided that we might focus on Band 1 for showing compliance with that specification.
The review of the high site design is coming up quickly. Richard would like to present to the Board in its Montpelier meeting in June.
Peck reported that the lifetime of the ATF had been extended to 1 September, pending developments with AIV needs.
Reid discussed a plot of the uv error amplitudes after CLEANing a simulated noiseless 4h observation of an HII region with out26 and its reoptimized version. There was some discussion over whether this was the best image for showing to ASAC and Board, or whether the protoplanetary disk image would be more compelling. Reid noted that the circular symmetry of that image posed certain imaging problems.
Crystal mentioned the alignment of telcal capabilities and CASA needs. There was a supposition that CASA should be able to replicate telcal results but the former were not well known to CASA developers. Myers will convene a discussion between these groups in the near future to ensure alignment. Telcal works on the ASDM format data while CASA works on measurement sets.
Mangum and Testi are finalizing purchase and plans for deployment of eight weather stations in a network at the AOS. A plan is also being devised to close out construction site characterization activities (material at the AOS) and redeploy some devices to operations. Wootten is working on this.
There was no SSR report. There was no report on the DRSP. There was no report on Spectral Line working group activities.
Next meeting will be 18 June, though the travel schedule of IPT leaders is complex at that time and it may be moved to a different date.
- 28 May 2008