Minutes from teleconference of the OSF Holography group. Last revised 2005-09-06. Tuesday, August 30 at 1600 UTC. Participants: Tony Beasley, Cesar Ocampo, Eduardo Donoso, Darrel Emerson, Jorg Eschwey, Brian Glendenning, Robert Lucas, Jeff Mangum, Rick Murowinski, Antonio Perfetto, Sakamoto, Dick Sramek, John Webber. The Agenda was to review the action items from the minutes of the last meeting. These are: PREVIOUS ACTION ITEMS, from Minutes of our meeting of July 29 2005: a) Antonio continues to work on estimates for the holography hardware. For now this will assume we are NOT changing our baseline plan of putting the transmitter on a 50-m tower within the OSF compound. b) Dick continues with the system block diagram. As in (a), the assumption continues that we'll be using a tower in our compound. Delivery of system diagram about 2-3 weeks. c) Jorg is making an estimate of what it would take to put a transmitter on a nearby mountain peak. Antonio will provide the needed technical information. Timescale for estimate about 5 weeks. d) Jeff Mangum will look at the APEX holography measurements. Reflections may be an issue - would this be better or worse with a mountain top transmitter? Do we need 2 frequencies? Communicate with the rest of the group, but especially to Antonio. e) Tower siting, assuming there will be a tower. Darrel continues to work with Eduardo, with latest input from Rick about the Vertex and Mitsubishi site facilities. f) Brian will make sure Robert Lucas knows about the new holography data format. Robert will adapt his analysis software to this. g) Dick Sramek will put into the PSI plan, the intention to test the revised holography system at the ATF. h) Rick, Schedule and milestone plan. A continuing task, but Rick will in particular get better information from Antonio. i) For everyone: another telecon to confirm progress will be held in about one month (i.e. end of August). ----------------------------- DISCUSSION Although listed in order of previous Action Items, the discussion listed under one point often ranged over several different issues: Item (a). Antonio asked if there was still the need to repoint the transmitter antenna. The baseline plan is to use a holography transmitter tower within the compound, which will therefore need to be repointed between our own holography pad, and a pad within the contractor's compound. [See comment below **] Antonio asked about whether we should be building a spare holography receiver, which would cost about 100k$. The answer is to delay doing so, but with the hope that budget would eventually permit a spare. A spare holography receiver has not so far been included in the budget. The Japanese will be providing a holography receiver for their antennas. [** In correspondence after the meeting, it was confirmed that the holography on Japanese antennas will use the same transmitter & tower. This implies the transmitter needs to be pointed in at least 3 directions, not 2. This may also involve a change in elevation as well as in azimuth.] Item (b). Dick expects to have the block diagram available by the end of this week. Item (c). Jorg and Eduardo now estimate that it is simply not feasible to put a holography transmitter on a nearby mountain. Apart from the logistical problems, there are serious environmental archaelogical issues that would have to be faced. Erecting a tower within our own compound, however, merely requires a letter of intention from ALMA. Item (d). Prior to the meeting, Jeff had distributed information about the APEX results. The conclusion is that we do not need 2 frequencies, and based on our own experiences, ground reflections present a tractible problem. Item (e). The most appropriate siting for the tower is in the SE corner of our compound, which gives line-of-site access to both our own holography antenna pad and that of the contractor. Rick confirmed that there is some discussion taking place on the siting of the contractor's compound, which could cause us to rethink this decision, but for now we should disregard that. There is room within our compound to place a tower up to about 450 meters from our antenna holography pad. However, for a fixed height of tower, the larger distance would of course reduce the elevation angle from the antenna to the transmitter. Robert Lucas confirmed that a distance of about 300 meters from antenna to tower was a good compromise, so we will take that as a working assumption. Darrel and Eduardo will come up with detailed site coordinates for the tower, and generate a terrain profile between this proposed position and the antenna pads. Item (f). Holography data format and analysis compatibility: all in hand between Brian and Robert. Items (g) and (h): the intention to test revised holography hardware and software at the ATF was reaffirmed, to start no sooner than 6 months from now. The existing ATF holography hardware may be transported from the ATF to Charlottesville immediately. [** Since the meeting Rick checked and confirmed this.] ----------------------------------- NEW ACTION LIST: 1. Antonio continues to refine the budget, including for a spare holography receiver. 2. Darrel and Eduardo continue to work to refine the proposed tower coordinates, and will generate a terrain profile. 3. Rick will coordinate with Dick on the schedule, making sure that everyone is kept informed so that everything is consistent and there are no surprises. 4. Next meeting: in order to avoid other ALMA distractions, we may have a short teleconference mid-September, followed by a longer teleconference near the end of October.