2023 Session I (c231)

    Correlation Status





    Sources DOYS UT Freq Stations Status PI Comment
    f231a     123            
    c231a     124            
    c231b     125            
    c231c     126            
    c231d     128            

    General comments



    • Station feedback summary at https://www3.mpifr-bonn.mpg.de/div/vlbi/globalmm/sessions/may23/feedback_may23.asc
    • ALMA scheduled, will have 3 MHz frequency offset
    • LMT runs off Oscilloquartz xtal without H-maser/Rb
    • LMT is linear polarized, has a feed rotator active during calibration scans that ought to return to 'origin' for VLBI scans avoiding any per-scan instrumental polarization angle offsets
    • MOPRA is linear polarized as in 2022 - LBAOps wiki page showing circulars is incorrect
    • NOEMA reference pad N07
    • TAMNA is not observing due to broken maser
    • Onsala DBBC3 16 Gbps in f231a and c231a as station "OD", DDC_U v126 firmware; f231a unfortunately with wrong receiver;  Flexbuff (koll.oso.chalmers.se for the DBBC3 backend. Not all of the 16 Gbps data need to be correlated. Perhaps only on LLAGN.

    Observing Notes

    • MRO c231a on time. Some scattered clouds
    • ATCA late as setup cannot start until CenA and 3c279 rise
    • LMT stopped observations after scan 598; LMT is ready to join c231b. Opacity at 225 GHz is 0.1. Tsys= 94 K
    • LMT skipped a few scans for focus/astigmatism corrections? Message at 7:53 CEST May 6. Missed scan 885. LMT will stop observations after scan 670. Tonight we missed a few scans and were late on a few observations that had a small downtime. Otherwise everything went well at 01:50 CEST May 7.
    • JCMT cannot run pointing/focus/Tsys/efficiency observation now, but can point source.
      With our pointing model we can point source within 10'' without running pointing observation, and focus is pretty stable.
      Problem is we cannot run Tsys.
    • JCMT: We are on source on time from the start. Tau is getting lower and current tau225 ~ 0.2. Our first scan number in the log is 373 (start=2023y129d02h20m00s), but in the vex file scan No for the first scan is No627. Vex starts at 255?
    • EB Tsys=210 K, 20mm water, but still can point on BLLac at 13:20 CEST, May 5; Started c231b a bit late, due to a thunderstorm warning, now we point on 3C273, Tsys=220 K @ elv=20deg, cloudy conditions, 15mm pwv; affected by rain, we point at 27 GHz and do VLBI at 86 GHz, though with marginal performance, Tsys ~300 K at 16:48 CEST, May 6
    • Last night EB had bad weather, heavy rain and thick clouds, Since 3 UT is getting better and we are now pointed on 0954+65 and observing. Tsys=250K at elv=20 at 6:07 CEST, May 8
    •  NOEMA c231b, we lost polarization RCP between 02:00 and 04:00 and four scans between 03:02 and 03:25. Most of the scan 18:04 on M87 was lost due to a blocked antenna (the last 2 minutes of that scan are ok). The rest of the scans were done under good conditions. Message from 11:14 May 6, referring to the night before.
    • Preliminary NOEMA flux estimates: NGC3998 = 76 mJy ,    NGC5077 = 51 mJy  ,    NGC4594 = 151 mJy    for 3C279 =  10.45 Jy
    • NOEMA joined c231a on 12:00 UT. The first two scans were not calibrated optimally but now we're good, phasing efficiency around 90%; Reference antenna is on pad N07, maser/gps drift should be below 1 nsec/day; at 16:36 CEST, May 5: Conditions are degrading, we are getting to low elevation through turbulent cloud layers. Phasing efficiency frequently below 50% now


    Modules still at ALMA OSF, to be shipped to Bonn (status 08/2023)

    ATCA, Mopra

    $ atcapos.py 2023y125d11h45m01s  # first At scan in c231a.vex.obs ==> track A: AT_W110
    $ atcapos.py 2023y126d07h15m00s  # first At scan in c231b.vex.obs ==> track B: AT_W110


    Clock data and Tsys are available via:

    Mopra polarization is linear X,Y, not circular as indicated by https://www.atnf.csiro.au/vlbi/dokuwiki/doku.php/lbaops/lbamay2023/c231b


    Phase center is pad N07 at (4523959.3899 m : 468037.3577 m : 4460353.5681 m), reconfirmed by M. Bremer 22.08.2023 from NOEMA data headers and setup


    Note, if there are no fringes, watch out for alternate YIG LO lock like in C221A vs C221B.

    Data: modules are at SHAO, to be shipped to Bonn (status 08/2023).
    C231A C231C are found on EHT 2023 modules already at Bonn.
    C231B C231D unknown - at SHAO?


    Data: modules still at LMT, to be shipped to Bonn (status 08/2023)

    VEX needs "axis_offset = 3.30 m;", the default of 0 meters is incorrect.


    P. Friberg: modules were shipped to SHAO. Jiang Wu at SHAO preparing shipping 08/2023.

    Recording media

    See the media distribution plan


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