LBA Experiment V230a

Goal: to determine position of stations ATCA, MOPRA, CEDUNA with accuracy 1—10 cm. Text of the proposal. Duration: 12 hours. Sky frequency: K-band (22.4 GHZ).

Main results

  1. Site positions

    Formal errors for site positions are: ± 10 — 30 mm for the vertical component and ± 3 — 6 mm for horizontal components.

    Station Station coordinates on 2007.06.24
      X Y Z
    ATCA-104 -4751640.182 ± 0.008 2791700.322 ± 0.006 -3200490.668 ± 0.007
    CEDUNA -3753443.168 ± 0.017 3912709.794 ± 0.017 -3348067.060 ± 0.016
    MOPRA -4682769.444 ± 0.009 2802618.963 ± 0.006 -3291758.864 ± 0.008

  2. Coordinates of new sources

    In order to test a feasibility of extension of the Calibrator Survey to the southern hemisphere, 5 new sources, previously not observed with VLBI, were included into the schedule, two scans per source.
    All 5 new sources have been detected. Formal errors of their position are ± 2 — 6 mas.

    0100-760 01h 02m 18s.6609 ± 0.0018 -75° 46' 51''.730 ± 0.003 24 32
    0219-637 02h 20m 54s.1722 ± 0.0004 -63° 30' 19''.387 ± 0.002 31 32
    0333-729 03h 32m 43s.0009 ± 0.0011 -72° 49' 04''.521 ± 0.004 18 32
    1941-554 19h 45m 24s.2477 ± 0.0007 -55° 20' 48''.949 ± 0.006 5 16
    2140-781 21h 46m 30s.0694 ± 0.0003 -77° 55' 54''.735 ± 0.002 25 25

  3. Parameters of radiotelescopes

    Parameters of the radiotelescopes determined from the experiment. The column 2 contains the averaged adjusted SEFD at elevation angles > 60°. The column 3 contains the multiplicative error factor of the SEFD estimate. The column 4 and 5 contain the estimates of the receiver temperature and the atmosphere opacity in zenith direction.

    Station SEFD m.e.f. T_rec opacity
    ATCA-104 850 0.17 25 0.17
    CEDUNA 8300 0.19 164 0.10
    MOPRA 890 0.17 26 0.12
    HARTRAO 7900 0.37 206 0.06
    HOBART26 2300 0.18 142 0.48
    PARKES 960 0.25 60 0.06
    SESHAN25 10000 0.21 119 0.27

  4. Estimates of the Correlated flux density

    The table of the Mean correlated flux densities of observed sources in jansky, except amplitude calibrators, at three ranges of the baseline projection length is available here.

Residuals

Plot of residuals at all baselines and plot of a sum of residuals and estimates of clock function at all baselines. The overall fit at all baselines is 50.1 ps with 2.5% observations discarded at RR polarization and 40.0 ps at LL polarization (with 7% of points discarded). 80% of scheduled observations at RR polarization and 90% of observations at LL polarization were used in the solution.

Listings of RR solution and LL solution are here.

Schedule file and log files

Problems

Group delays at PARKES show a scatter at a level ± 2 ns. Refer to the plot of residuals with clock function.

Estimates of clock function at baseline HOBART26/PARKES at v230 experiment have a scatter ± 2000 ps, while normally they should have a scatter one order of magnitude less: of ± 100 — 300 ps. For example, the estimate of clock function at baseline HOBART26/PARKES at crf45 experiment that run two weeks earlier on 2007.06.12 were a smooth function of time with peak to peak variations 200 ps.

Analysis of short time variabilities of fringes amplitudes and fringe phase at baselines with Parkes did not reveal anything unusual:

The scatter of fringe phases within 2 minutes is not much greater at baselines with PARKES than at baselines without PARKES. The clock behavior is consistent with lack of phase stability at some parts of equipment. It is unlikely it is caused by malfunctioning of H-maser itself, since estimates of clock function have very small scatter at IVS experiments before and after v230.

Schedule of the v230 experiment in sked format.

Schedule of the v230 experiment in vex format.

Listing of the coarse solutions using v230 data.

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This page was prepared by Leonid Petrov ()
Last update: 2008.06.24_22:04:09