VEGAS Team Meeting

April 23, 2012

Attendees

CASPER Team:

• Glenn Jones
• Dan Wertheimer

NRAO:

• Galen Watts
• Randy McCullough
• Marty Bloss
• John Ford
• Mark Whitehead
• Anish Roshi
• Ray Creager
• Jason Ray
• Richard Prestage

Meeting Notes:

Observation Status:

The Green Bank weather has taken a bad turn. Continue to wait for a few more weeks in hopes of continued observing with current system.

Quadrant Detector for wind corrections. Initial tests of using QD data for corrections are encouraging, but it is not something that could be used right now to raise the wind limits for QC observations.

Testing Status:

1. Roach II and SFP+ update
   • Prototype boards w/QRD memory issue have been fixed by hardware calibration. All are now working reliably. All other issues are resolved, so a new layout is in production yielding new production boards in mid to late summer 2012. Our schedule allows us to wait for the production boards.
   • Mezzanine SFP+ issues have been cleared and released for production. SFP+ boards expected in a month a two
2. ASIAA vs National ADC board
   • We select the ASIAA ADCs for VEGAS
   • The system requires 16 boards; order 22
   • We could wait to order, but a production run is currently being being scheduled and we would like to tag on that run.
   • Both types of ADCs are interleaved ADCs running at 1/2 the rate so there are some phase, offset, and gain differences between them that cause spurs due to matching (<40dB). With careful adjusting this can be reduced further to -48dB. Not a critical issues so we should measure them upon installation and have software compensate during use. If they remain stable calibration would not need to be reset often except when changing equipment; we will do empirical measurements during use to determine how often calibrations are necessary
   • Results from the Allan Variance tests for the ASIAA ADC follow. It seems to be good to about 20s, which is comprable to what we got for the National ADC ~15s.

• • (note that the theory line is shifted incorrectly)

Other items:

The majority of VEGAS Mode 13 work will re-commence once Mark Wagner returns to Berkeley in two weeks. This should be the next mode tested in Green Bank.

While work focuses on Modes 2-17, we will switch to bi-weekly team teleconferences. Once integration and Mode 13 tests ramp up weekly meetings should resume. May 7 will be next team teleconference meeting.

Test during GBT maintenance next Thursday will include 1-sec integration fix.

Add to mail exploder Ray, Hon

-- MartyBloss - 2012-04-23