n21dk01

    n21dk01 Correlation Report

    General information

    • Project: "Wideband spectral line VLBI study (Dongjin Kim) 22/43GHz 8Gbps"
    • Epochs: G, H, I, J, E, K, L
    • Station feedback: No further issues found outside the a priori known issues (weather, broken shutter).
    • Data issues: No major issues, only that VDIF of KVN epoch J had to be processed at the correlator to split out the two VDIF threads into separate files - as all KVN Mark6 had recorded epoch J from two 10G interfaces, but onto the same Mark6 module "group", leading to "clumpy" VDIF and associated initial problems in DiFX
    • Requested config: PI request was K-band 0.25 MHz/ch 1.0 sec AP, and separately Q-band 0.50 MHz/ch 0.5 sec AP
    • Actual config: 0.25 MHz/ch 0.5 sec AP, because after a few unsuccessful split-correlation configuration "hacks" DiFX and recordings turned out to unavoidably require a joint K+Q correlation. The PI will need to use CASA/AIPS to split out K and Q bands, and apply spectral (Q) or temporal (K) averaging to the requested resolution.

    Status

    what date
    Effelsberg transfer Epochs G and H complete, remainder postponed due EVN Session 2 VLBI (27 May-17 Jun) 20.05.2021
    Yebes transfer Epochs G, H, I, J, E complete 11.06.2021
    Effelsberg transfer Epochs I, J, E, K, L completed 23.06.2021
    Fringes Ef-Ys K-band and Ef-Ys Q-band, epoch G 10.06.2021
    KVN started data transfer 16.06.2021
    KVN ongoing transfers... 16.08.2021 still transferring... finished. xx.08.2021
    Epoch G full correlation K+Q v1 finished 15.08.2021
    Epoch I full correlation K+Q v1 finished 16.08.2021
    Released (difxexport) version 1 of epoch G and epoch I to the PI. Awaiting feedback. 17.08.2021
    KVN finished data transfer, info from DK Jung 06.09.2021
    Reported back that Ku missing in epoch H, 7 other files 0-byte, retransfer? No. 08.09.2021
    Remaining five epochs correlated xx.04.2022
    Data Status
    Ep DOY Ef 2021 Ys xfer Kt xfer Ku xfer Ky xfer Correlated Releasable?
    G 124 20.5. ok 8.6. ok 22.7. ok 10.7. ok 1.7. ok rev 1 yes; Nov 2021
    H 127 19.5. ok 29.5. ok 25.7. ok -missing- 23.7. ok rev1 4.4.22 yes; Apr 2022
    I 141 20.6. ok 5.6. ok 5.8. ok 4.8. ok 3.8. ok rev 1 yes; Nov 2021
    J 141 21.6. ok  8.6. ok 20.8. ok 17.8. ok 14.8. ok rev1 4.4.22 yes; Apr 2022
    E 142 20.6. ok 11.6. ok 1.8. ok 29.7. ok 28.7. ok rev1 3.4.22 yes; Apr 2022
    K 143 23.6. ok (not observed) 28.8. ok; 2 scans 0B 26.8. ok 23.8. ok rev1 3.4.22 yes; Apr 2022
    L 143 23.6. ok (not observed) 2.9. ok 1.9. ok; 1 scan 0B 31.8. ok; 2 scans 0B rev1 4.4.22 yes; Apr 2022
    Production Correlation Status
    Ep DOY Correlation Config Diagnostics Notes
    G 124 15.8.2021 rev1 v2d, vex Residuals pdf, FITS pclist Ef not on source until ~18:30 UT
    Ku residual rate +20 mHz
    H 127 4.4.2022 rev1     Ku did not observe
    Effelsberg was scheduled for K-band only
    I 1411 16.8.2021 rev1 v2d, vex Residuals pdf, FITS pclist Ku residual rate +20 mHz
    J 141 4.4.2022 rev1      -
    E 142 2.4.2022 rev1     Ku residual 0 Hz after Ku -0.8e-12 s/s in VEX
    Ef and KVN stopped after No0065
    Ys did whole track but from No0066 no baselines
    K 143 2.4.2022 rev1     Ys did not observe
    L 143 3.4.2022 rev1     Ys did not observe

    A Priori

    Yebes

    • J. Gonzales: rate 1.17e-13 s/s, offsets in logs named n1k01?ys.log on vlbeer.
    • Did not observe K and L due to heavy rain and broken shutter.
    • VEX freq block sidebands UUUU UUUU LLLL LLLL rather than the default UL UL ... from SCHED
    • Epoch E: scan No0003 (142-0814) file empty or not recorded

    Effelsberg

    • U. Bach, etransferred epochs G & H. Pending transfer of the remaining epochs.
    • Offset +19.3 usec in G
    • Logs named ndk01g, ndk01h, and later n1k01i, n1k01j, n1k01k, n1k01l, n1k01e on vlbeer
    • H-maser rate same as in GMVA f211a, i.e., 2.05e-13 s/s.
    • VEX freq block sidebands UUUU LLLL rather than the default UL UL ... from SCHED.
    • Epoch G: wind and bad weather, first part ot track unusable, not on source until ~18:30 UT

    KVN Yonsei, Ulsan, Tamna

    • Table of clock offsets, sign for VEX same as in table
    • Table of most recently determined site positions
    • H-maser rates not available, assuming 0 us/s for Yonsei and Tamna, same 0 us/s for Ulsan but high residual rate 20 mHz and used VEX Ku -0.8e-12 s/s
    • Tie of KVN to Ef+Ys : shift KVN VEX clocks by -2.83 us from kvn a priori values

    DiFX

    Special setup for correlation, because Effelsberg does not have simultaneous K and Q capability.

    • Modes 'kband' and 'qband' in Observed VEX are are dual band at KVN, single band at Ef: would end up with FITS with KVN+Ef KQ+K for mode 'kband', and FITS with KVN+Ef KQ+Q and mode 'qband', i.e., KVN KQ in both FITS files (data duplication).
    • Initial attempt using v2d "freqIds=..." and a K-band and a separate Q-band v2d file was only partially successful. Issue: any change in array composition (e.g., telescope recorded data in one scan, in another one not) jumbles the DiFX .input FREQ table frequency IDs an e.g nominally K-band -only list of freqIds refers to some Q-band recorded channels as well and misses some K-band recorded channels.
       
    • Production approach uses VEX file where Ef has been made dual K&Q, a v2d file with two Datastreams for Ef (one K, one Q), and a bit of scripting to separate the Ef filelist into two lists one with K-band and the other with Q-band VDIF files
    • Zoom bands of 64 MHz added into to KVN 2ch x 512 MHz to match Ef Ys 64 MHz wide channels in USB/LSB
    • Zoom bands added also to Ef Ys 64 MHz LSB channels in order to flip these into USB and produce all-USB visibility data; avoids HOPS fourfit issues with mixed USB-LSB visibilities

    Effelsberg file list splitting by band, example for Epoch G:

    vsum -s /data/n21dk01g/Ef/*.m5a > filelist.ef
    rm -f filelist.ef.k filelist.ef.q
    for scanNr in `vexpeek -s n21dk01g.vex.obs | grep kband | grep EF | cut -c 3-6`; do
        echo "grep kband 01g_ef_no$scanNr"
        grep "01g_ef_no$scanNr" filelist.ef >> filelist.ef.k
    done
    for scanNr in `vexpeek -s n21dk01g.vex.obs | grep qband | grep EF | cut -c 3-6`; do
        echo "grep qband 01g_ef_no$scanNr"
        grep "01g_ef_no$scanNr" filelist.ef >> filelist.ef.q
    done

    Notes

    The FITS-IDI file of each epoch contains both K and Q band, at a resolution of 0.5 seconds and 0.25 MHz/channel

    This is due to the way that the correlation had to be configured because not all scans had all recordings from all stations, hence the DiFX-internal frequency indices were not consistent across all scans, hence selective correlation in two runs using only specific frequency indices and per-band averaging settings never produced consistent K(/Q)-only products per run.

    The K and Q bands must be manually split out by the PI from the FITS-IDI file under AIPS/CASA.

    For K-band, temporal averaging needs to be applied during the manual splitting to get from 0.5s AP to PI-requested 1.0s APs.

    For Q-band, spectral averaging needs to be applied during the manual splitting to get from 0.25 MHz/channel to the PI-requested 0.50 MHz/channel.

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     n21dk01_KVN_clk.png
    clock info for KVN
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     n21dk01g.KQ.vex.obs
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    n21dk01g.vex.obs
    Epoch G initial file, Ys-Ef fringes, KVN todo
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     n21dk01g_v1.pclist
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