Known Issues CASA 4.5.2

  • Most Important Issues for CASA 4.5.0/4.5.2
    • VLA data taken on 20 September 2017 and later contain an additional Tcal entry for solar observations. CASA 5.0 and earlier will fail in gencal to calculate requantizer gains. Use CASA 5.1 and later for such data.
    • cvel, cvel2, and mstransform with regridms do not regrid properly for channel widths > or = 2 x the native channel width
    • If you want to use a data set filled with CASA 4.3.0 or later in CASA 4.2.2, you may encounter an error about missing spws. To fix, run "!fixspwbackport msname" within CASA on Linux. msname is the name of the MeasurementSet.
    • Restructuring of the clean task is ongoing and tclean is actively being developed. Use with care, being aware of its experimental nature (bugs will not be responded to at this stage)
    • Currently, gaincal will not find good solutions if any correlation (including cross-correlation) in the data is completely flagged. As an interim solution one may split the unflagged data in a separate file and then perform gaincal
    • Plotting the virtual model in plotms fails when it was created in clean with imagermode='mosaic' and ftmachine='mosaic', or gridmode='aprojection'. And it also fails in tclean when gridder='mosaic' or gridder='awproject'
  • General:
    • NFS mounted disks --- It is not recommended that you run CASA (e.g. have your data) on disks that are NFS mounted. It can be done, but in some cases the files will be NFS locked and this can crash casapy or its tasks. In this case, you have to restart casapy.
    • If you receive messages like xvfb timeout you may try to clean out your /tmp folder, then restart CASA.
  • bandpass ---
    • Currently, bandpass will not find good solutions if any correlation (including cross-correlation) in the data is completely flagged. As an interim solution one may split the unflagged data in a separate file and then perform bandpass
  • gaincal ---
    • Caltables generated in CASA 4.5.0,1,2 do not correctly store sky coordinate information for Ephemeris objects (e.g., planetary bodies). This leads to incorrect results when using gainfield='nearest' in calibration application contexts, since as of CAS 4.5.0, the MS does use Ephemeris info for such sky coordinates (causing Eph obects to fail to match to themselves between MS and Caltables). Use of explicit field specifications in gainfield is sufficient to avoid this problem. Ephemeris object sky coordinates are fixed in Caltables beginning in CASA 4.6.
    • When using gainfield='nearest' for channelized and field-dependent calibration (e.g., ALMA Tsys; rarely anything else), an internal calibration application bookkeeping error can arise when one field's calibration is auto-mapped to multiple fields. When this occurs, the results of the calibration task (e.g., solving with gaincal or other solving tasks, or applycal) are highly pathological numerically, yielding grossly distorted solutions or corrected data (e.g., very, very large or small in amplitude by many orders of magnitude, or precisely zero). Additionally, in the applycal case, a far larger-than-expected fraction of the data is also typically flagged. This problem seems to be exceedingly rarely encountered by users, and it can be avoided entirely by avoding gainfield='nearest'. This issue is fixed in CASA 4.6.
  • polcal ---
    • Polarization angle calibration poltype='X' is sensitive to any position shift in the source model relative to the phase center with respect to the phase center in intensity.
  • setjy ---
    • sometimes setjy does not properly overwrite a current model in the header of the ms (virtual scratch column). It is recommended to use delmod if a model exists and shall be overwritten.
  • plotms ---
    • plotms crashes with the xsharedaxis or ysharedaxis parameters being set to True on Linux
  • plotcal (also check the matplotlib section for plotcal issues) ---
    • When plotcal does not release a calibration table properly but keeps it in lock, try to hit the quit button in the plotcal GUI first. Then redisplay the table.
    • If you use plotcal on a caltable, it will then be put into the cache of the table system. If you try to re-run a solve (e.g. gaincal, bandpass, blcal, polcal) with the same caltable name and append=F to overwrite, then when it tries to delete the original caltable it cannot due to the cache. You will see an error like:
                     SEVERE  gaincal::Calibrater::solve 
                     Caught exception: Invalid Table operation: SetupNewTable
                     ngc5921.demo.gcal is already opened 
                     (is in the table cache)
      Either use a different output caltable name, or restart you casapy session (exit and start again) to free up the cache. Update: As of Patch 4, you can use the rmtables task to delete tables.
    • BPOLY solutions from bandpass must be plotted versus frequency and not channel. BPOLY and B solutions can only be overlaid if xaxis = 'freq'.
    • GSPLINE and G solutions from gaincal can be overlaid, though this has not been extensively tested.
    • Currently, plotcal needs to know the MS from which the caltable was derived to get indexing information. It does this using the name stored inside the table, which does not include the full path, but assumes the MS is in the same directory as the cal-table and has the same name it had when the cal-table was created.
    • If there are flagged channels at the lower edge of the data, say, 0~4, and you select a channel and 'locate' it from plotcal, it will give the incorrect channel number (will count from the first unflagged channel, not zero).
  • uvcontsub ---
    • fitorder should be kept low (<= 1) unless the line band is relatively narrow compared to the fit bands. If the image rms markedly rises in the middle line channels after uvcontsub, fitorder should probably be lowered.
    • fitorder > 0 does not work with solint > 'int'
  • VLA Switched Power In CASA v4.2.2 and higher, the weight calibration for EVLA switched power/Tsys corrections is still being investigated. Visibility corrections are ok. Since switched power calibration is not used by the EVLA pipeline (except for requantizer gain corrections, for which this problem is irrelevant), and since calwt=F remains the general recommendation, users should rely on statwt to generate appropriate data weights.
  • concat ---
    • When concatenating MSs which have been imported from ALMA Cycle_3 data and have fields with attached ephemerides (typically all solar system objects), it should be verified that the FIELD tables of the MSs to be concatenated have the same FIELD ID for corresponding ephemeris objects (the ids for other objects without ephemeris are irrelevant in this context). If the field ids for corresponding ephemeris objects are not the same, a bug in concat may prevent the FIELD tables from being merged correctly. In this case, the work-around is to split out the objects of interest and concat the split-out MSs. This problem is fixed in CASA 4.6.0 .
  • msmd ---
    • The behavior of the msmd.*forscan methods differs in CASA 4.4 and 4.5 compared to earlier and later versions. In CASA 4.4, with the addition of the obsid parameter and its default of 0, only scans belonging to the first observation ID will be found if obsid is not specified. Starting in 4.6, the obsid parameter defaults to -1, meaning that all scans in all observations will be searched, restoring the behavior of CASA 4.3 and earlier.
  • Synthesis Imaging:
    • clean ---
      • In the clean task, when the modelimage parameter is specified, and a previous model exists on disk with the name 'imagename.model', they are both added before prediction. This can happen if you restart clean to continue a deconvolution, but don't set modelimage='' before doing so.
      • clean expects that all input polarizations are present. E.g. if you have RR and LL dual polarization data and you flagged parts of RR but not LL, clean will ignore both polarizations in slice. It is possible to split out a polarization product with split and image separately. But you will not be able to combine these part-flagged data in the uv-domain. We will remove that restriction in a future CASA release.
      • Facets do not always work on Mac OS X. This is frequently due to a built in limit for the number of open files. Per default the setting is usually 256 (use ulimit -a to check). For facets in clean it might be required to set to a higher number, e.g. ulimit -n 2048. All commands must be issued from a bash shell outside CASA.
      • Mask editing in interactive clean does not work reliably when the input MS is in reference frames other than LSRK or TOPO. Two incarnations of the problem were encountered so far: (a) when working in GEO, as on solar system objects, mask editing is impossible. (b) When working in BARY, masks created in CASA 4.0 cannot be edited when they are used as input masks for interactive clean in CASA 4.1. and higher.
      • The Mac OS compilers are different to Linux compilers and some options are not available (e.g. opemmp and sincos). This causes some of the clean procedures, in particularly mosaicking, to be slower on MacOS than on Linux.
  • Visualization:
    • viewer ---
      • The CASA viewer does not yet support the entire region shapes and parameters at this stage.
      • Viewer may not properly open saved region files
      • With the new region panel being used now, It may be advisable to rename the $HOME/.casa/viewer/rc file that stores previous configurations of the viewer.
      • Viewer - labels are not shown - this can be caused by a conflict between an installed version of PGPLOT and the version of PGPLOT that comes with the non-root version of CASA. If you do have PGPLOT installed in a standard location (e.g. /usr/lib), you may try moving it aside and see if it resolves the problems. If you do encounter this problem, please report it to the CASA team.
      • Some X11 settings can make the viewer unstable. We identified that the line
        Load "glx"
        in /etc/X11/xorg.conf
        is such a setting. If you don't need this line for aother applications, it would be better to have it removed.
  • Analysis:
    • msmoments ---
      • task only accepts MS data (not Scantable). The input MS have a few limitations to work with msmoments task: 1. MS must have FLOAT_DATA column 2. Number of polarizations (correlations) must be same in all rows
    • uvmodelfit ---
      • When running uvmodelfit, the output componentlist does not contain the uncertainty in flux that the task calculates (and displays at the end of the fitting process).
  • Simulation:
    • simobserve/analyze ---
      • corruption of simulated MS by an atmospheric phase screen is only available from the toolkit. simobserve and sm: Under some circumstances, running sm.setnoise and sm.corrupt, or simobserve with thermal noise, twice using the same project name, the noise can be applied a second time, doubling the noise level. Be sure to use different project names for creating different simulations with noise. see casaguides.nrao.edu for the latest simulation information
  • Single Dish
    • sdflagmanager ---
      • Due to a limitation of current implementation, row or channel flag status may not be restored properly. This may happen when any rows are flagged.
    • sflag and sdplot ---
      • Data selection by raster causes an error when it is used in combination with field and/or timerange selection.
    • sdimaging ---
      • sdimaging task may fail when more than several MSes are chosen as inputs (infiles) to create single output image. It is because the file descriptor opened by the task exceeds the limit defined by OSes. You can relax the limit of the number of open file descriptors by the command, e.g., ulimit -n 4096 . Note the typical number of file descriptors opened by the task is 35/MS.
    • tsdbaseline ---
      • Values in MASKLIST column of baseline table would be incorrect for spectra n-sigma clipping do not converge. This issue is not expected to have an impact on the application of baseline table which will be supported in future releases.
    • The following single dish tasks with the old task interfaces are removed: sdbaselineold, sdcalold, sdcal2old, sdfitold, sdflagold, sdflag2old, sdgridold, sdimagingold, sdmathold, sdplotold, sdreduceold, sdsaveold, sdsmoothold, and sdstatold.
    • The following issues in the previous releases are fixed.
      • sdaverage: polaverage did not work properly for row flagged spectra.
      • sdbaseline raised an error when the input data set contains a spectrum in which all channels are flagged.
      • sdcal2 did not recognize CM10 as an ALMA antenna
      • sdcal2: calmode='otf' and 'otfraster' did not work properly if any data selection parameters (iflist, scanlist, pollist, etc.) are specified
      • sdcal2: calmode='tsys' had a bug that frequency labeling is not properly handled when multiple spectral windows are defined for Tsys measurement.
      • sdflag and sdplot: raster row/map selection did not work when input data is in MS format.
      • sdgrid: the data gridded by sdgrid could not be imaged using sdimaging

    See also the Alert notices in the CASA User Reference & Cookbook and the Casaguides Wiki Pages for more details on known problems and workarounds.

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