GBT Commissioning and Operations Meeting 24 October 2003 AGENDA 1. Az Track and Telescope Status -- Bob 2. Observing News -- Ron 3. Frontends, IFs, and Spectral Baselines -- Roger 4. Spectrometer Status -- Rich 5. Software Status -- Ray / Nicole 6. Scheduling Status -- Carl 7. Project Planning Status -- John 8. Any other Business REPORTS 1. Az Track and Telescope Status Azimuth track: SG&H have experienced run times of nearly a week with the model. This would have stretched the schedule out. Instead, they are procuring additional RAM (2 GB), and "condensing" the model (causing the model to assume a set of boundary conditions on the sections far from the wheel loading patch, where values would be linear. These move and change size as the load patch moves.). Dennis and I are planning to visit them the first week in November, and will invite the new structural engineer, if he is on board by that time. Structural repairs: The walkway far side is 100% complete. The near side is about 50% complete. Repairs remaining: Near side: Finish welding the stiffener in, replace handrails, and repair one remaining fillet crack. At Actuator room: Grind and repair a conduit attachment, cut beams for stiffeners, weld in stiffeners, and repair 2 fillet cracks. At walkway support: install 2 2" angle iron braces. Nearly all of the above will have to be done in rappeling gear. Counterweight cover plate: Grind or drill crack tips and caulk. We received a good amount of documentation from the fabricators of the elevation shaft assemblies. They had a number of defects during fabrication, but appear to have corrected them, or received a disposition of some kind from Radiation Systems or NRAO. Much to study here. Strain Gauge installation and testing occurs next week -- RAA 2. Observing News Observing and commissioning this week has been a mixed bag, not only of topics (Radar, Galactic/extragalactic HI, K-band observing, Pulsar, Spigot Card tests, program checkouts, RFI tests, K-band commissioning, Holography,....) but in problems experienced. Most of the problems we've seen have occurred during test time -- all of the observers this week seem to be very happy with their GBT time. By far, the majority of lost time for observing this week was due to high winds. Items for possible discussion at the meeting are: o Servo/Brake faults with the antenna seem to be happening frequently. o The lower K-band receiver has a problem with refrigerator modulation that will require removing the receiver. This has been scheduled for mid November so as to minimize impact on already-scheduled observation. Most projects aren't affected by the problem -- at worse, a few projects may be about 75% as efficient as they could have been. o LO1 5/500 MHz lock warning messages have been causing a stir. The problems don't seem to affect observing but the engineers have lost some sleep trying to understand what's going on. o We had two Holography runs, both of which seemed to have produced excellent data. There's a 'systematic' correction factor I've overlooked but that I need to determine before I can proceed with the data reduction. Basically, due to the offset geometry of the GBT, a phase correction that is normally insignificant for a conventional telescope is about 500x larger and cannot be ignored for the GBT. o We had our "Power Balancing" workshop yesterday and I think all went away with a better feel for how we should implement a solution and the level of effort needed. I'll post a summary sometime on Friday. It's unlikely Jim will be able to make it to the meeting. He and Jim Moran/Maryam Modjaz seem very pleased with the improvement from last Spring in the baselines and calibration of the K-band system. -- Ron 3. Frontends, IFs, and Spectral Baselines New cryogenic amplifiers for the Ku-band receiver were received Thursday from CDL. These amps have better transistors, providing minimum noise temperatures of about 7K. The amps being replaced were built in 1992-93, had minimum noise of about 15K, and were difficult to repair. So, when one of the old units developed a problem, the decision was made to replace all with the new design. In a similar development, new cryo amps for the Q-band receiver will soon be here. Two of the eight units in the receiver last year were found to have gain instabilities, and while replacing those, CDL volunteered to supply eight new units. These will be available early next week, and will be drop-in replacements. The minimum receiver noise will be about 10K lower with the new amps. About 10 hours of testing with the spectrometer using noise sources and the X-band front-end were accomplished in attempts to understand baseline structures introduced on continuum sources. It is clear that ripple in Tsys produces ripple in (Ton - Toff)/Toff, with amplitude scaled by Tsor. Evidence though shows the curious fact that the system exhibits Tsys ripple introduced very late in the system, perhaps even within the high-speed samplers. The Tsys should of course be set at the front-end, so we continue to struggle to understand what the evidence shows. -- RDN 10/24/2003 4. Spectrometer Status No major problems this week. Jim Braatz reported a 1-channel spike in the middle of the band. This is due to a 100 MHz harmonic getting into the system. This may be due to a slight timing problem in the High Speed Samplers, explained below. This week continue on redesign LTA board. specifically working Address and sequencer FPGA design. Some progress was made on the High Speed Samplers. As reported previously, after modification, the samplers showed evidence (illegal sample values) of timing or noise problems. This was finally traced to a slight change in the 100 MHz clocks relative to the 400 MHz clocks in the sampler. By adding about 3" of cable to the 100 MHz lines, the system ran error-free. In addition, the samplers ran better in the system than other samplers. This can be explained in further detail at the meeting. The bottom line is that all samplers except the two which were modified with longer 100 MHz clock cables showed very small 1-channel spikes at 100 MHz harmonics. The modified ones were clean. Three High Speed Samplers were partially modified. This modification takes only about 2/hrs per sampler. It removes all the switching power supply noise from the sampling clock. This partial modification will be compared with the full modification (which takes a day per sampler and is a bit tough on the circuit board.) The results will be discussed with Fisher, O'Neil, and Ford to decide which way to go. Good news on the spigot card: modifications to the firmware to prevent the microprocessor from missing interrupts from the control computer were successfully tested. More good news: the absolute timing of an artificial pulsar relative to site time was verified. This is very important for tieing observations at different epochs together. Bad news on the spigot card: it picks up framing errors in the data stream after about 40 seconds. This may be related to some recent changes to the spigot computer. Kaplan is investigating. Plans for next week: - Continued work on the LTA re-design - Spigot testing with Kaplan - Continued work on high speed samplers -- Rich & Holly 5. Software Status Single Dish Development IPT #56 - Friday, October 24, 2003 Today ends week 3 of 6 in the current development cycle, which is the 8th cycle in 2003. The Plan of Record for the current development cycle is available from the wiki at Software.PlanOfRecordC82003 along with the most up-to-date status information. The spectrometer balancing issue was resolved last week, corroborated by recent observing and commissioning activities. A followup meeting to discuss a strategy for systemically understanding how to balance for different observing scenarios, and making the process easier, was held on Thursday. Incremental work was completed on Python and antenna tasks for PTCS, making the SOAP interface to M&C more complete, SDFITS generation, and prototype applications for the "new GO" which will be unveiled during the next cycle for initial community review. One milestone for the week is that Bob Garwood successfully imported an SDFITS file containing spectrometer data into DISH and made a plot. This data was preprocessed with the new Python components, so the filler was bypassed. The good news is that both paths produce the same output. Additional work is required to calculate Tsys and Tcal which is currently underway. There was no significant operational support this week. -NMR 6. Scheduling Status Last Week ======== Observations for: GBT02A-031, GBT03A-014, GBT02A-028, GBT03B-005, GBT02A-063, GBT02A-046, GBT02C-062 Completed: GBT03B-005 October ====== Scheduled hours [backup]: Astronomy ~ 327 [90] Maintenance ~ 132 Tests & Comm ~ 285 [18] November ======= Scheduled hours [backup]: Astronomy ~ 282 [130] Maintenance ~ 101 Tests & Comm ~ 193 [47] Shutdown ~ 36 Un assigned ~ 104 December ======= Scheduled hours [backup]: Astronomy ~ 199 [38] Maintenance ~ 111 Tests & Comm ~ 198 [30] Shutdown ~ 36 Un assigned ~ 201 -- RCB 7. Project Planning Status October 20th Planning Meeting Minutes Rm 241 OCTOBER 14th 10:00 A.M. [0] Observer comments From Frank on radar: Successful. Problem summary: Lunar Ephemeris file woes: "There were initial problems with the lunar ephemeris file. We learned that the file must be strictly in the right format, with no flexibility in the spacing of the columns. This should become more flexible, and we should be able to pick the ephemeris file out of a list rather than always having to name it "Asteroid.tbl". A request should be entered into the project office, if none yet has been. From Frank on RFI scans Successful. Problem summary: 1. iards did not work, and gave lots of error messages. 2. The 240 MHz filter in the 450 MHz receiver XLC channel does not work. 3. Converter module #2 was found to be disconnected. 4. gbdish seems not to find the Ypol part of scans, and thinks there are only half the number of integrations. Problems 1 & 4 were solved by running "weekly" instead of "stable". Gary is going to check out the 240 MHz filter. It can't be replaced until the receiver is brought to the lab. The perpetrators of #3 will be shot. From Ron, on commissioning K band: Mixed success. Upper half good, lower half not so good. Problems: Chairs RH 9 Balancing OD2 R1/L1 instabilities These problems were mostly discussed via email last week, and so we did not belabor them. The Balancing problem is fixed, a native RH 9 installation is coming along, with a workaround in place. Chairs will be ordered. The OD2 is being worked on today. The K band receiver status will be determined at a special meeting this afternoon. [1] Resource calendar schedule conflicts and discussion Wednesday, Oct 22 Track shimming -- Time? Regular maintenance day. The resource calendar showed it going until 11:00 P.M. Monday, October 27th -- 8:30 Maintenance start Observing finished up late on that Monday. [2] October Observing Schedule discussions K band receiver problems The lower half of the K band receiver is not operating quite like you'd like. We may decide to pull the receiver for test and repair, which may take a week or so. [3] November/December Observing Schedule discussions Carl is running out of backup time to schedule. The commissioners will endeavor to get stuff off the checkout queue and onto the ready queue. Ron and Carl will meet with all involved to work out a plan. We will try by all means possible to fill the backup time with astronomy projects. [4] GBT development planning Cycle 9 2003 project meeting November 10th Cycle 9 2003 allocation meeting November 11th Q4 2003 Quarterly review/Q1 2004 Quarterly Goals Dec 15th Cycle 1 2004 project meeting Jan 12th Cycle 1 2004 allocation meeting Jan 13th 6 Month look discussions: At our meeting last week, we found that we will be seriously oversubscribbed in the software field for the foreseeable future, and not just for the 6 months. We are going to create a spreadsheet of effort required over the next year. This is for the purpose of deciding what if any projects must be put off or cancelled. Phil, John, and Nicole will start the process, with Project Managers stepping in to check the numbers for their projects. [5] AOB None -- JF 8. Any other Business