Notes for V2C telecon, June 27, 2013 ------------------------------------ In attendance: Arthur Niell, Johannes Boehm, Ruediger Haas, Brian Corey, Mamoru Sekido, Chris Beaudoin, Dirk Behrend, John Gipson, Bill Petrachenko. Broadband developments: ----------------------- Arthur reported that automated processes for extracting correlated flux density are now complete. A history of past fluxes is available to demonstrate internal consistency but still need to verify absolute values. Data has now been correlated for the 24 hour May session. For some reason PCAL does not line up the band data as well as in previous sessions leaving a residual phase curvature with frequency. Spurious PCAL does not seem to be the problem and in fact the elevation dependence of spurious PCAL seen in previous sessions has essentially disappeared. GGAO12 is now down due to a faulty turbo pump. A new one is on order. No new broadband observations are planned until the May session has been fully processed and analyzed. Production of the Kokee broadband front end is on schedule. A new dewar was designed by Chris Eckert; it held vacuum first try. The front end will be sent to Lincoln Labs for characterization mid-July. Completion is required by end of September with component deliveries etc on schedule. After completion of the Kokee front end, a new front end will be made for Westford. Ahmed emailed to say that he had finished a rescaling of the QRFH to cover 2.2-14 GHz (which is the VGOS spec) instead of 2-12 GHz (which was the design target for GGAO12). This was done either for Jim Lovell or Callisto probably inspired by investigations into an Auscope broadband upgrade. In addition to improved high frequency performance, the new feed will have better RFI rejection below 2 GHz. Simulations show 70% efficiency all the way to 14 GHz. In the past simulations agreed with measured values to within about 5%. Arthur mentioned that correlator support for mixed S/X -> broadband observations has been upgraded so that flux denxities are now calculated correctly. Ruediger mentioned that he has been pushing for dual S-band polarizations at Onsala for CONT14 and wondered whether it would be supported in the correlator. Arthur wasn't sure and said he would check if it made sense to include it in the list of things to do. Arthur mentioned that RDBE3.0 including support for complex sampling, PCAL and more has now been tested at an internal consistency level. However, support for complex data in the correlator is not yet working correctly. RFI: ---- Brian reported that RFI spectra were taken using GGAO12 down to 10 MHz in low band. Low band is nominally 2-5 GHz. Data were taken at 12 azimuths and the spectra did not vary much with azimuth. There is a lot of RFI just below 2 GHz and another strong band around 750 MHz. The DORIS beacon can be seen at about 2 GHz. Initial analysis indicates RFI is no stronger than about 10 dB below the non-linear threshold. However absolute calibration is difficult. Chris reported that he communicated with Hayo to try to recreate the La Plata RFI monitoring system. Apparently Gerhard Kronschnabel designed the system and it was modified at La Plata to point the antenna automatically. The La Plata group are interested to collaborate to develop a RFI monitoring system that could be copied by others. Source Structure: ----------------- Johannes reported that Stas Shabala produced a memo reporting simulations of the impact of source structure on station positions. CONT11 schedules were analyzed. Depending on the station, source structure intruced errors between a few mm and about 1 cm. Johannes will circulate the memo to the V2C. Automation: ----------- John reported that within the next week there will be a meeting at USNO where this topic will be discussed. There is still some disagreement on details of the VEX2 definition. Scheduling: ----------- Johannes reported that Jing Sun is now using the VieVS scheduling software operationally to schedule Austral sessions. John reported that some minimal support has been added to SKED to support broadband sessions, specifically to properly calculate SNR's and media usage. The upgraded version achieved nearly 60 scans per hour for the May 24 hour broadband session. Achieving this number of scans also required some tweeking of the slew parameters at Westford. Atmosphere: ----------- Arthur mentioned that Chris Beaudoin has a student looking at ionosphere TEC values determined as part of broadband fringing and comparing them to GPS values. This will add credibility to the fringing process. Other: ------ Mamoru Sekido reported that NICT continues to work on their small antenna with a fixed frequency broadband system. The current LNA works to 11 GHz and the next generation LNA will work to 14 GHz. Both are uncooled. The new LNA will be installed within the next week. The GSI 12m antenna at Ishioka should be completed near the end of this year with observations beginning early next year. Ruediger reported that the Onsala Twin project has run into a problem with the local legal authority - next level from the most local. They have withdrawn the building permit for one of the antennas due to potential issues with bird life. The decision will be appealed but if the appeal is unsuccessful this could lead to a delay of about six months while a new site is found and the authorization process restarted. Due to summer vacations there will be no V2C telecon in July. The next telecon will be on August 29.