Notes from Commissioning Coordination Meeting 20 September 2002 1. Observing Program Checkouts Richard and Ron reported on the status of program checkouts. Most of the programs in the Active Checkout queue have been examined in detail, and some are ready for scheduling. The primary hold-ups on scheduling the remainder are the need for Spectrometer multi-bank capability, X-band baseline improvements, and getting K-band back on the air and checked out. The present schedule calls for multi-bank capability to be available by the end of October. X-band baselines will be considered very soon (see the discussion below). The K-band receiver will go back on the telescope in the first week of October. Ron is doing active support of some of the programs he has been assigned this weekend. All L-band proposals through trimester 02B have been checked out. Ron has evaluated nearly all of the trimester 02C proposals and detailed comments will go on the gbtstatus web pages within a few days. A number of these proposals will then be moved to the Active Checkout queue and checkouts will be assigned. Some of the 02C programs are very similar to programs already checked out, and so can be scheduled after minimal checkout. There are 30 Spectral line projects among the 02C proposals, but only three new Spectrometer modes were requested that were not identified in previous terms (one additional mode was added after the meeting): 2W2--200 single and multi-mode 1W1--800 multi-mode Either 4N8--12-9 single-bank or 2N4--12-9 two-bank Thus, all spectral line proposals in the queue so far can be satisfied by 12 Spectrometer modes. This allows us to focus our efforts on these modes, many of which have already been examined. We appear to be getting close to having checked out the basic capabilities needed by large numbers of proposals in the queue and progress toward getting more programs on the air should accelerate soon (= good news!). As K-band checkouts will begin soon, Ron pointed out that we will need some additional staff effort to attack these programs. One major issue in program checkout is the quality of spectral baselines. The focus of recent investigations has been L-band baselines, but three programs are being held up by X-band baselines. Phil suggested that it was probably time to attack the X-band baselines, unless L-band baselines were very close to resolution. Rick, Dana, and Roger will meet early in the week to assess the baseline issues and make a recommendation: ** Action 20sep02-1: Assess spectral baseline status and make a recommendation of priorities. JRF, DB, RN 2. Spectrometer Checkouts Dave Hogg wrote up the astronomical checkouts of another Spectrometer mode and it is now on the web. Richard did another three modes on Friday morning, and will do more next Friday. They are finding that the 2-quadrant modes are working nicely, but that the 4-quadrant modes are having problems. Rich was working on the spigot card with Dave Kaplan and Ray Escoffier, but sent along the following notes: > Several 8-sampler modes had engineering tests and were approved. (These are highlighted on Rich's spreadsheet.) > Two tested modes have problems that need to be addressed. > Three requested modes are illegal. Again, this points to the fact that we need multi-bank operation. With multi-bank operation, we can get the same functionality with 4 sampler modes. > Discussed small repeatable blips in the ACF with Ray Escoffier. He suspects ground bounce is the cause and has bade a few suggestions to confirm this and possibly fix it. > Progress on the Spigot Card: o Electrical interface to the new computer is working. o Complete communication protocal tested. o No observing modes validated yet, but it is getting closer. 3. Software Update Nicole distributed a new status report, a description of the new features in the upcoming M&C v3.7 release, and a screen snapshot of the new Configuration Tool. Status reports can be viewed at the URL software.gb.nrao.edu Current projects are all progressing well. The problems with the Configuration Tool described last week that caused it to move to "red" status have been resolved, and it is back on track. Projects for Continuing Maintenance & Enhancements, Observing Capabilities, Pulsar Observing Capabilities, and PTCS are all on schedule. M&C v3.7 will be released next Wednesday, 25 September, as part of the monthly release cycle. Features in this month's release include Spectrometer improvements Balancing Improved Initialization Integration time correction PF2 Rx support FITS file updates for the Spectral processor and LO Other miscellaneous improvements The cable switch on the Spectral Processor that will get the sig/ref phasing correct in the first phase of a frequency switching scan will be done in conjunction with this M&C release (cf. the FITS file update). The Configuration Tool was presented. Ron and Frank have been testing this. This is the initial implementation of basic Spectrometer setup in its simpler modes, and will be expanded and made more general in the future. 4. Baselines Rick reported that the high-pass filters that block signal below 1200 MHz were tested with the L-band receiver last week. They did not remedy the problem with bad baselines that appear to be caused by aircraft RFI. The baseline problems reported by Richard and Dave Hogg are being investigated. Glen noted that he has been seeing some bad baselines in the 300 MHz Receiver that appear to be caused by RFI. Although this causes some loss in data and more work on the part of observers to edit the data, it is still possible to get good data. For this reason, this problem will not move onto the priority list until later. Roger reported that the new modulator for the fiber optic transmission system is still on order, with delivery expected in October. 5. RFI mitigation Other problems investigated include RFI near 1250 MHz, which was traced to Glonass signals (and probably cannot be eliminated), and a 5 MHz rail near 1400 MHz. Feedarm servo filters are still being installed. A decision was taken to install screened plywood in place of the windows in the shielded rooms in the Jansky Lab when those windows are sent out to have their frames re-plated. This work is presently scheduled for December and January. 6. Other business Roger reported that work on the K-band receiver is going well. Mike Stennes has found a number of components and cables that were faulty and has fixed them. The receiver will go to the Equipment Room in the coming week for testing with backends. Ron and the other commissioning scientists plan to have a commissioning plan for K-band observing completed and ready for presentation at the October 4 commissioning meeting. Richard asked for comments on the multi-beam observing plan by next Wednesday, which was taken as an action: ** Action 20sep02-2: Comments on the multi-beam observing plan due in to Richard Prestage by Wednesday, 25 September 2002. (Commissioning Staff) Ron reported that Dave Thilker is getting some nice HI images of M33 and M31. Anish reported on progress in testing cross-correlation and polarization capability. He has been using the Spectral Processor. He finds that in tests in which he expected a correlation coefficient of 1.000, he got 0.986, but it may be possible to calibrate this out. Experiments to test the polarization properties of the GBT are producing good results. He has been able to retrieve the beam shape of the GBT. In all, the telescope and system appear to be working as expected. He now has a setup routine provided by Richard, and further tests will be done on Sunday night. Summary of Actions: Action 20sep02-1: Assess spectral baseline status and make a recommendation of priorities. JRF, DB, RN Action 20sep02-2: Comments on the multi-beam observing plan due in to Richard Prestage by Wednesday, 25 September 2002. (Commissioning Staff) PRJ // 22 Sep 2002