Mangum Wootten Darrel
Software CDR8 under way in Chile.
Four antennas on high site, looking forward to running with them but so far no luck. Being simultaneously construction and commissioning is difficult; one trips over the other too often.
Not much to be said on ACDs. Actual motion ante temp control are difficult. Production devices are expected in next few months. No detailed findings.
LLC operate and do their job. When they are on phase is improved, when off phases change. We saw a very odd thermal coefficient to Melco and were trying to undersand when fiber broke. Could have been associated with temp, using another fiber now intended for commo purposes.
A configuration is selected for four antennas, short baselines. We expect to be able to make simple maps.
Holography--follow detail on JIRA tickets which have reports. Maps look good but we see astigmatism especially at B3 which differs dish to dish doesn't change with elevation. May come from rx. At higher freqs the astigmatism is much less, suggesting the dishes are good with temperature and elevation but there seems to be another factor in the front end. After return to the OSF DV02 surface errors had gone from 11 microns when it left originally to 18 microns when it returned. Groups of panels or single panels have moved some how.
DTE: nothing to add.
There is a lot of data on phase stability. Periodic errors seen earlier have gone away, perhaps owing to a software fix.
Total power instabilities have occurred in a number of ways. Faulty amplifier in one case but ones which were vexing were finally tracked to the membrane. A 5 deg tilt angle was selected but it isn't enough. Width of beam and tilt mean one side of the beam is normal to the membrane then and we see baselines in the spectra and variations when the wind blows. A bigger tilt may be difficult given the constrained space.
DTE: The tilt may go back to the prototype days.
REH: It goes back to the original antenna spec.
Commissioning scientist post to be given. Lance Simms made a big contribution but has returned to Lawreence Livermore Labs. We do need to replace that loss. Appointment length 2.5 yrs now. How to recruit being accepted.
Scott Schnee has accepted NAASC
CREs. Some variances on requirements for all of the production cartridges. For B6--specifies goodness of polzn in frequency ranges at 99% or 98%. This is OK for best lines. Spec is 99.5%.
Current feed horn design is overmoded high freq so sensitive to manufacturing errors. Design should be changed but it appears that would introduce a delay. We need 98%. To make accurate total power calibration we would need to do full polzn.
How integrated are the horns and the mixers?
Is 98% across whole band something we can live with?
LT: need spec across whole band. Can we really do anything? We do have accurate polzn on B7.
REH: Could get new ones perhaps a year from now, then have half with new design. New version promises 96.8% -15dB across the band.
Two ends are where the -15dB applies, middle of the band works.
Other change request also. This involves switches, which are solid state and switch in ns. Then there is a period in which the value of the loss settles down. Probably owing to trapped charges in gates. First CRE gave a longer grace time for settling, only one bit could be changed at a time. A further CRE is proposed to .02dB after 1s. This is .5%, not a huge factor on gain and down to very small after two seconds. Probably this is acceptable.
221. Change in the IF Switch Operations Mode and Specifications
STC asked about call for studies for development proposals. STC endorsed, will go ahead with call and then use those as the source for development plan. Call should go out on a month timescale.
Same scheme as for ELT instruments.
EA: In JP most activity is to develop EA ARC, attend test proposal activities.
EU prototype still not clear as to disposition. Temporary importation expiring.
NA call for proposals is out.
O2 procurement. Contract going on. Expect delivery beginning of August to OSF. Training planned for AIV and someone from Cambridge.
Some discussion on cloud monitoring. Need a real recommendation by next month's meeting. Using one at Paranal. Optical. Only during night as a check.
ASTE may have a near infrared camera.