GBT Commissioning Meeting 07 March 2003 AGENDA 1. Az Track Status -- Bob A. 2. Spectral Baseline work -- Dana & Roger 3. K-band and other commissioning -- Ron 4. Software status -- Amy 5. Spectrometer status -- Rich 6. Project scheduling -- John 7. Observing schedule -- Carl 8. Any other business REPORTS & DISCUSSION 1. Az Track Status * The delivery of replacement wear plates has been delayed by as much as two weeks.  It is taking longer to get them straight than previously thought.  Jeff Cromer went down to check their progress: all other dimensions and angles are correct.  The earliest that azimuth restrictions could be lifted would be 3/28 to 4/4. * The crack on plate 44 has deteriorated this week.   * 3 proposals have been received for the track welding demonstration. We are requesting formal, best and final bids to be submitted next week. * An Observatory internal review of some track issues is to be held Friday. -- RA Discussion: Bob added that, of the new wear plates at the tooling company, most have a single bow in them that should be relatively easy to flatten to meet spec. One has some waves that may be a little more difficult. The company has said they will replace this plate if it cannot be brought into spec. There were two runs of the track deflection measurements over the past week. These are the "before" measurements that will be compared with the results following the stiffening and bridging retrofit. A metallurgist interested in working on our problems will make a site visit on 18-19 March. The telescope will be weighed in the last two weeks of March. Load cells and jacks have been, or are about to be, shipped. The weighing will be a daytime, maintenance day activity, and access to the telescope may be restricted for at least part of time the measurements are underway. 2. Spectral Baseline work Baselines associated with position switching onto strong continuum sources, when processed in standard ways, suffer from what appears to be low-level variations in system noise that varies rapidly with frequency. Baseline ripple amplitude due to the noise variations is roughly proportional to the source continuum strength. Initial investigation into ways to remove the baseline ripple using continuum calibrators is encouraging, but how the noise variations are introduced is not well understood. Lab tests investigating noise variations using the Ku-band front-end are on-going. We now know that baseline stability is extremely sensitive to phase stability of interconnecting cables within the system. With spectrometer 800MHz bandwidth observations, any cables with lengths more than a few centimeters long must be stable to tenths of electrical degrees over the switching cycle duration. Cables using teflon dielectric operating at room temperature typically exhibit phase/temperature sensitivities of 100ppm/C, much higher than is acceptable in many cases. Other cable types that might substitute at critical locations are being investigated. We continue to work on summarizing the results of our spectral baseline investigation over the last three months. A Tuna lunch talk will be given by Rick on 11 March (Tuesday) in CV and another talk in GB in the near future. A written report will also be produced with recommendations on how to proceed. -- DB Discussion: Roger said that the best guess of the source of the high frequency structure may be the thermal waveguide gap. Measurements are underway to try to confirm this. There are a couple of ideas of how this might be addressed, if confirmed. Barry asked if this is seen on all the receivers, and Roger replied that it was. This design was not used on the maser receivers on the 140 Foot, but was on all the GBT receivers that were used on the 140. 3. K-band and other commissioning The proposal checkouts that were scheduled for last weekend were canceled because of a combination of weather, subreflector problems, and Spectrometer problems. Karen has observed using a couple more Spectrometer modes. There were no other commissioning activities for the telescope this week. Instead, Karen has started reducing the data from her past Spectrometer checkouts and Frank and I have had a few good sessions on specifying full algorithms for configuring the hardware. Depending upon the weather, next week we are planning on some Q-band tests, which I'm outlining tonight, or repeating some of the proposal checkouts that were cancelled last week. Due to Karen's travel plans, the next Spectrometer checkouts will happen at the end of the month. -- RJM Discussion: Bob stated that there had been no more faults with the subreflector since the weekend. Glen said that he had had difficulty getting enough IF power for observations with widely separated lines over the bandpass. He and Roger will pursue this later. Ron noted that the new focus measuring tools are very helpful. 4. Software status Software Development Division #27 - Friday, March 7, 2003 Integration testing on M&C v3.12 was completed Wednesday, March 5; integration testing was successful and the system is ready for regression testing. Regression testing is scheduled for Monday, March 10. M&C v3.12 is scheduled for release (pending successful regression testing) on the morning of Wednesday, March 12. A written report on regression testing for v3.11 will be released by T. Minter on Thursday, March 6. The key updates for the March release are enhancements to the RMS calculations for the active surface, the completion of fixes to ensure spectrometer software reliability, and the astronomical verification and subsequent release of the resolution for the active surface 100ms problem. Work on the completion of GO improvements that were initiated last month has slowed; the slowdown is because FITS file changes need to be negotiated with the Aips++ group as do changes to IARDS. Work continued on the EMS this week, culminating in the completion of 6 MRs which have been submitted to K. Constantikes for approval. To meet the goal of having a "show and tell" piece available for the PTCS Conceptual Design Review in April, the team has compiled a work plan that shows incremental progress through the month of March towards this goal. A draft Plan of Record is complete for April and will be finalized on Monday, March 10 at the morning scheduling meeting. (The draft will be distributed at the Friday Commissioning Coordination meeting.) Joe Brandt has begun work on upgrading to VxWorks tornado2. This upgrade combined with a compiler upgrade will allow the Software Development Division to make use of additional C++ features such as exceptions and the C++ Standard Library throughout Ygor. -- AS 5. Spectrometer status The spectrometer had some problems during the week, but is working correctly right now. Most of the effort this week has focused on fixing module level problems. LTA test fixture: This has had an intermittent problem for a year or so. It has become unusable in the past few weeks. Some modifications were made and it seems to be working now. Failed LTA cards: One LTA card has been repaired. We still have one bad LTA card. Sample Distributor card: The spare sample distributor board has a problem that affects sampler 0. We have not had time to do anything with it yet. System Monitor card: The spare system monitor card seems to have fixed itself during testing today. I will leave it in for the day and see how it does. This may have been a bad connection somewhere. This is the board that caused Braatz's problems over the weekend. There was no pulsar spigot testing this week. The need to get the above modules fixed took precedence. Two repaired cards were tested in the system today (one LTA and one System Monitor). These were removed for the weekend observing - just in case! Ray would like to come up and help with the LTA problems that we have been experiencing lately (multi-integration glitches and slot dependence). It would be nice to schedule this fairly soon. Plans for next week: fix the failed Sample Distributor and LTA cards. -- RL Discussion. Dave asked if there was anything that could be done in a fundamental way to improve reliability. John replied that a re-build of the sample distributor card is planned, and will help. Also, Ray is coming over to help diagnose the "slot dependency" of the LTAs. The long term plan is to try to root out the causes of unreliable performance and fix them, but that may take a while. 6. Project scheduling March schedule Last weeks in March are still scheduled for weighing operations. No overnight shutdowns anticipated. March is heavier with observing, lighter with commissioning. April Schedule Last weeks in April are set aside for track welding, as a placeholder. It is unclear exactly when this will happen. 6 month planning Configuration project discussions (email by Ron) Agreed that the direction Ron proposed was sound. John warned that the balancing was left out. Richard and Ron contend that this is the provence of the baseline group. John's concern is that it will get dropped under the table. Project list discussion (Nicole's spreadsheet) Discussed the spreadsheet version of the task list that Nicole put together, and Richard modified. We went down the list and agreed as to which were to be active in the next 6 months. John will flesh out the RFI and Baseline areas. We need to put people's names in each box on the chart before we can really say that we're committed to the project. This list will be publicized soon K band upgrade cost estimate John reported about a 50K materials cost to upgrade the receiver. John will ask Mike Stennes to prepare estimates of: 1) Just replacing the amplifiers. 2) Building a 2 beam variant of the wideband system. Phil and Ron will develop a rationale for these 3 options. Long-term outlook No action taken. All should think about this for next week. AOB Discussed faults that happened over the weekend. Discussed communications problems between people working on the system, operators, and observers. John and Bob will dust off John's mail from last summer and issue it, if appropriate, to inform people what their responsibilities are regarding working on the telescope. -- JF Discussion: Roger stated that they had been unable to get on the telescope to re-cool the Q-Band Rx, so that would now be done on Monday or Tuesday of next week. There is also some cabling work that needs to be finished for Q-Band hookup. 7. Observing schedule Last Week ======== Observations for GBT02A-008, GBT03B-037 (TOO), GBT02C-007, GBT02B-018, GBT01A-054 and GBT02A-031 GBT02A-008 has been completed. March ===== Astronomy ~ 341 hours (backup ~ 284 hours) Maintenance ~ 146 hours Test & COmmissioning ~ 260 hours April ==== Astronomy ~ 334 hours Maintenance ~ 151 hours Shutdown ~ 39 hours Tests & Commissioning ~ 197 The simple dynamic scheduling seems to be working. -- RCB Discussion: Carl stated that if the wear plates are replaced by the end of March, he will not have to make any adjustments to scheduled programs in April. If not, some might have to be rescheduled. Juan asked if the backup observers were being guaranteed that they will get all the time they requested, and they are. 8. Any other business Richard noted that Claire Chandler will be here from 7 April through the end of the month. She will work on "out-of-focus" holography, or OOF, in conjunction with the group at Cambridge University. If this can't be worked out for some reason, she will help with program checkout. The PTCS Conceptual Design Review is scheduled for 8-9 April. PRJ 7 March 2003