V2C telecon notes, Thursday Sept 27, 2012 ----------------------------------------- In attendance: Miroslav Pantaleev, Jim Lovell, Dirk Behrend, Mamoru Sekido, Jing Sun, Tobias Nilsson, Zinovy Malkin, Gino Tucarri, Arthur Niell, Chris Beaudoin, Bill Petrachenko, John Gipson, Chopo Ma, Dan MacMillan 1. Broadband system developments and tests (Arthur, Chris, Gino,...) - PCAL analysis (Brian) - fixed frequency feed at NICT (Sekido) Another broadband geodetic-style observation using the Westford/GGAO12 baseline is planned for next week. The session will probably be 6-hr but could be longer. The schedule appears to have improved sky coverage due to sked parameter tweaks. The Westford dewar is being installed and expectation is for receiver noise down to 30K due to improved cabling. SLR radar will be turned off. This required 1 weeks notice. The GGAO12 upgrade is being assembled at Haystack. Included in the upgrade is a new front end positioner, a new dewar, and a band splitter for transmitting signals from the front-end to control room. All components are in hand but in some cases that are larger than expected and vacuum leaks in the dewar are being repaired - no show stoppers expected. The system is being test driven on the ground and will be installed at GGAO after the geodetic session next week. A new mechanical engineer at Haystack is assisting with this work. Sept 17 observations confirm ~6 ps azimuth dependence to pcal delay. Measurements with the broadband system are quite precise both for pcal phase and group delay. Long term trends need to be removed to clearly see the dependence. It is not known whether the variation is predominantly in the LMR-400 5 MHz cable or the downlink fiber (or both). DBBC3. Firmware is being developed for FPGA's handling band generation. Plans are being made to integrate the DBBC3 into a front end - probably Noto first but others later. To avoid self-generated RFI the DBBC3 is being integrated into an aluminum box for shielding. DBE intercomparison is planned for Oct. 25-26 at Haystack immediately after the VLBI Technology Workshop. Participating in the comparison are the RDBE (USA), DBBC (Italy), CDAS (China), ADS3000 (Japan), and if export issues can be sorted out a prototype system from IAA. Sekido-san distributed some view graphs before the meeting and discussed the situation at NICT leading to their decision for fixed frequency feeds to achieve broadband observations. This is part of a project for precise intercontinental frequency (and maybe time) comparisons. The idea is to use small (1.6-m) VLBI antennas near the atomic oscillators and a larger antenna for signal boosting. The small antennas will use uncooled Quadridge feeds with fixed filters to avoid RFI. The large "boost" antenna will likely be the Kashima 34-m which, due to its Cassegrain optics, will need a feed with spreading angle ~7 degrees. To achieve this they plan to use two coaxial (one inside the other) sub-feeds with bands 3.2-6.4 GHz and 9.6-15 GHz. They have chosen minimum redundancy frequencies at 3.2, 4.8, 9.6, and 12.8 GHz. The time/freq project completion date is 2015 but initial test observations are planned for 2013. Long term they hope to participate in VLBI20120 additionally including 11-m (and faster) antennas at Koganei and Kashima. The frequencies they have chosen are clearly within the VLBI2010 range and have reasonable (although not optimum) performance due to their minimum redundancy character. Overlap with other VLBI2010 antennas may be problematic due to disjoint RFI restrictions. 2. RFI (Bill, Chris, Brian) Barriers are being designed to shield the GGAO VLBI antenna from colocated DORIS transmitter and SLR aircraft avoidance radar. A detailed test plan is being developed. A DORIS transmitter will be provided with a frequency offset so that barrier tests will not interfere with normal DORIS operations. 3. Source structure (Richard, Arnaud) Richard Porcas sent a note that VLBA+Eff observations were carried out in Sept of 7 sources to study core shifts. 4. Full automation: schedule -> final products (John) John has enhanced sked to generate VEX files that can be used to automatically set up correlator control files. In the past this required a lot of hand work. The development was done in consultation with Mike Titus at Haystack. Adam Deller also succefully tested the new process. DBCAL, which is used to input met and cable cal data, has been replaced by software which automatically searches for appropriate files and inserts the data into open DB format. Ed Himwich is developing Field System code to support DBBC and RDBE. He is currently in Australia testing the DBBC implementation. VEX2 is being define primarily by Ed Himwich and Alan Whitney. New modifications will support VLBI2010 broadband requirements. 5. Optimum schedules (Jing Sun, John) In the near future VieVS applications will turn towards simulations both to confirm previous results determined using PPP and OCCAM and to develop strategies to better handle the atmosphere. 6. Antenna deformations and site ties (Dan) Dan continues to assist Mitch Connelly to develop an error budget for VLBI site ties. Dan has not looked further into the impact of bearing displacements and wonders if the new mechanical engineer at Haystack is available for this. The processes defined by Perguido Sarti for determining gravity path length variations for the Italian antennas is complex and time consuming. Can something be done that is simpler? Jim Lovell plans to survey the Australian antennas to develop thermal and gravitational deformation models. This is planned for end of this year or start of next. Methodology includes Solidworks simulations, use of temperature sensors and laser distance measurements from fixed piers to reflectors on the antenna reflector and structure. Chris Beaudoin pointed out that mechanical displacements do not convert simply to electrical path length variation. 7. Atmosphere (Johannes) 8. TecSpec post-mortem - Feed summary - DBE summary - RFI survey Miroslav informed us that simulations are nearly ready to begin for Eleven and QRFH feed efficiency on the Intertronics antenna. Gino proposed that the missing data CDAS, ADS3000 and IAA prototype be collected at the October 25-26 DBE intercomparison at Haystack. 9. Wiki progress (Brian) Brian has sent out instructions for how to enroll for Wiki "write" access. Two people have given this an initial look. All are encouraged to get set up as soon as possible and to start inserting new content. Although Brian is away for a few days he will be available to answer questions by Oct 1. News: Chris Jacobs sent a note that an agreement has been reached to use the new ESA 35-m antenna at Malarque, Argentina for X/Ka CRF observations. This will finally provide an X/Ka baseline with access to the south polar cap. Reminder: The 1st VLBI Technology Workshop will be held 22-24 Oct at Haystack Observatory. The DBE intercomparison will take place on the following two days. Next V2C telecon: Thur Nov 1, 2012.