Notes from Commissioning Meeting of 09 August 2002 1. Program checkouts and commissioning priorities Richard reported on efforts that he, Ron, and Carl have made over the past week to organize program checkout and to determine commissioning priorities. A new web page has been set up for this purpose, and can be found at http://www.gb.nrao.edu/gbt/gbtstatus/index.html This web page will contain a complete census of observing programs in the queue and their current status (completed, scheduled, ready for scheduling, awaiting new capability, under checkout, or awaiting checkout). The page also contains current development priorities. It lists the priorities for the next few months in broad terms, and the priorities for August in detail. These pages will continue to be developed and expanded. Ron reported on the status of the 11 proposals that were selected for checkout at the beginning of the summer. They are: 01A-11 Dickey - completed 01A-40 Lockman - scheduled and partially completed 02A-03 Darling - checked out; L-band portion scheduled; other portion awaiting PF2 02A-08 Roberts - observed last week with good results; another installment due in 6 months 02A-22 Allen - completed 02A-38 Thilker - M31 data taken, M33 data scheduled this month. 02B-06 Yusef-Zadeh - Test data taken. RFI problems at 1.7 GHz; needs more testing. 02A-18 Churchwell - Needs multi-bank mode for production observing. Would benefit from more testing when C-band Rx is reinstalled 02A-17 Balser - Undergoing tests. Mostly limited by X-band baseline problems; Needs multibank modes for maximum observing efficiency. 02A-21 Lockman - Undergoing tests. Somewhat limited by baselines. 02A-41 Rood - Same comment as 02A-17. Actions arising from this (I will enumerate these by the date of the commissioning meeting so that the relevant meeting minutes can be consulted in the future, if needed): 09aug02-1: Continue 02B-06 testing; specify limitations in detail. [Ron] 09aug02-2: Continue 02B-18 testing; specify limitations in detail. [Frank] 09aug02-3: Continue 02A-21 testing; specify limitations in detail. [Dana] The action on proposals 02A-17 and 02A-41 is to continue with spectral baseline studies and improvements, but that is covered by an existing commissioning priority that Rick, Dana, and Roger are pursuing. 2. Spectrometer Status Richard reported on Spectrometer status as relayed by Rich. Several more modes were checked out in the past week, particularly the 4-IF, 50 and 12.5 MHz modes. The 2-quadrant modes look good, but the 4-quadrant modes have a step in the auto-correlation function that needs further investigation. The 4 sampler modes, currently being tested in a single bank, should easily expand to 16 sampler modes when multi-bank operation is available. The "scruff" at the edge of the bandpass in one mode is still under diagnosis. 3. Software Status Nicole reported on software status and handed out a Software Development Division status report. The group is in the middle of a release cycle with the next M&C release scheduled for 28 August. Michael Lacasse is giving a presentation next week on the new antenna test range software. The observers interface team has identified a way to place a button on the GO screen that will pop up the new Configuration Tool screen that will allow system configuration. This scheduled for inclusion in the September M&C release. The LO1 investigations are proceeding, but have moved from "green" to "yellow" status. Joe B. reported that they continue to make continue to make good progress in narrowing down the cause of the frequency switched phase inversion problem, but have not found a fix yet. In other news, David Kaplan will be visiting from Caltech to work on the Spigot Card project. Receiver PF2 support will appear in the September M&C release. 4. Spectral Baseline Investigations Rick reported that some progress has been made in narrowing down the causes of the wavy baselines seen in the 1.4 GHz receiver in frequency switched mode. The problem appears to arise ahead of the transfer switch as it moves with frequency and also with change in subreflection position. This suggests that it is in the telescope optics. Two components were found, one corresponding to a 30 m round-trip path, and the other to a 200 m round-trip path. The 30 m component is probably between the subreflector and feed (15 m each way). There is probably some multi-path reflections appearing and perhaps an external source of noise giving rise to the 200 m component. These effects are now easily reproduceable and are thus amenable to testing. Roger reported that the vendor of the fiber optical modulators state that they can provide an improved module that should reduce the 2.4 MHz standing wave the devices are producing. The vendor will not quantify the improvement, and is working on a best-efforts basis only. The cost is $4k. As we need a spare modulator anyway, we will order one of these for evaluation. Delivery time is 4-6 weeks. 5. AIPS++ news Joe M. is on his way back to Socorro after a productive stay in GB. Bob reported that the new van Vleck correction with Hanning weighting is now the default in the Filler. This is currently in Daily, but will migrate to Weekly and Stable in the near future. 6. Other news Glen showed some plots of 800 MHz Spectrometer bandpasses in the 1.4 GHz band that were taken by his student, Chris Orban, and himself as part of an investigation into their flare star proposal. There is major interference evident from GPS satellites, Glonass, and Iridium. A significant finding is that when the Iridium signal strength flares, it affects the entire Spectrometer bandpass when in the 800 MHz, 3-level mode. Summary of Actions from this meeting: 09aug02-1: Continue 02B-06 testing; specify limitations in detail. [Ron] 09aug02-2: Continue 02B-18 testing; specify limitations in detail. [Frank] 09aug02-3: Continue 02A-21 testing; specify limitations in detail. [Dana] PRJ // 10 August 2002