Sci IPT meeting 2008 April 16
CV: Remy, Rob, Jeff, Antonio, Crystal, Al, Meredith, Todd, Hills, Morita, Vila-Vilaro, Testi, Hibbard, Nikolic, Richer, Emerson, Lucas
RH: Report. FE unpacked, accident on site but no one hurt. Some damage to Vx antenna. Melco--acceptance going on, data taken. Third telecon to review data as it is being digested. Target still second week of May for first one, second one then goes thru tests and so on.
KIM: Expect to deliver first antenna mid-May. Data analysis from measurements continues.
Board meeting was upbeat--getting to know new Director, discussion on progress. Science was highlighted by ASAC report. Some point of debate on development plan. Board had second thoughts on a review of where ALMA should be in 2020. A subcommittee of the Board will think again and recommend a process which must be somewhat scaled down. We do need a process and a defined development plan on which to base our budget. The situation needs resolution.
LT: Briefly discussing with van Dishoeck and de Zeeuw. From them I think there is an appreciation of the ASAC's work as what is needed. There may be some change to the composition of the science groups but we need the science justification. Hesitant to have a big meeting, however.
RH: There are different drivers in different partners. In EU it is important to have a budget. In NA and JP it is important to define the actual work.
We will hear the response after the next Board telecon, after the next ASAC telecon.
Cartridge availability items. Will need a CRE but isn't there now. Discussion of plan from Simon.
Polarization--ESO management has accepted to push for mods on the design. They need to negotiate with IRAM. There is a lot of other work to be done but we will return to this.
Line-stretcher compensation. Hills finds the present setup unsatisfacoty.
DTE: We will start out with 4 hardware LLCs, after experience with them we will review the decision on whether to take this out with hardward or software.
FE CRE is in, no feedback.
QW plates. FE held the position of not planning to provide QW plates, now they need specs. A proposed specification was generated. Current FE spec is pretty restrictive. Works at one tuning, high loss add 20-25% to total Tsys but accuracy is only specified to 10%. Could produce this error size itself. The proposed spec is more reasonable in range of frequency and accuracy. Any updates or thoughts?
JGM: We did have a discussion. Do Gie Han and Rick understand that this is the specification?
RH: There has been no response.
CB: I do not understand--the person who was responsible for this was F. Patt. We had a group discussion on this for a few hours. We discussed this in detail.
RH: What we have learned in ALMA is that discussions need to be followed with process. We need a document with the correct number, etc, goes into the system.
It should not be possible for a document to go through the system. I'll work on pushing that through.
All this does is to produce two QW plates at some time, for experiments to see how well they work. This does not define the production run.
Probably would need to be quartz and not molded plastic.
RH: I just attached a new item to the bottom of the agena. CRE form and summary and some illustrated plots. Spectral dynamic range needs to be 10000:1. If phase noise on LO, the convolution with the source will make this show up. So this requirement translates to a req on the LO at the frequency of interest. Multiplication raises spurious system. At 900 GHz, this on the 100 GHz LO would mean 60 dB suppression. In science there is no distance. System says 500 Hz is to be avoided. Second note shows some illustrative plots of what we might get with relaxed specs. Both interferometric and SD spectrum. A problem occurs when FS, a SD mode, but the requirement is on both.
Please look at this offline and send in questions.
ATF to be extended until LO system is needed in Chile. Master Laser etc needs to leave the ATF.
New array has much better sidelobe performance. Reid cautions that when using Briggs weighting etc, the effect in final image is not so pronounced.
RH: Outcome of optimization is that we improve uv coverage and beamshape but we do need 12 extra pads so we will need to make a stong case for the improvement this will make. It will be on the order of $1M. TB decided this is nonsense. RH argued that just looking at the uv patterns one can see big holes, if those holes have no measurements one is certainly worse than if one had made measurements in those regions.
RR: I can make a very strong case for some pad positions to be changed. In the image plane much of the improvement occurs with 2-4 new pads.
RH: We have another 4 weeks or so to close this item. Trenches will soon be dug to put in fibers. Between now and next telecon we need a definite proposal.
RH: We need a concrete table of changes and their results. I don't think it makes sense to move just 2 or 4 pads, but rather how many additional pads we need. If we move 6 and add in 6 that would make more sense.
JM: Will summarize conclusions on atmosphere.
testing at ATF is going on right now. Will do line pointing.
LT: Should we bring DRSP inside project.
RH: Did you volunteer?
LT: Yes, I will do it.
RH: Thanks Michel for his efforts.
Pointing--in order to review documents on AEM amd Melco metrology we have to sign nondisclosure agreements, and to include Vx information we do have we must violate the agreement.
RH: I will inquire about this. Apart from that issue, what is the status of the document?
JGM: It lacks information on metrology.
RH: Rick has decided he is concerned about some things, I'll pass on a note.
Bojan: I'd like to draw attention to the workshop in Grenoble.
Richer: We'd like some contributions from ALMA-J and ACA simulations.
K-IM: I am very interested in the workshop and will attend.
- 16 Apr 2008