Creating data sets

Anime uses the CASA Measurement Set (MS) data format as on-disk storage format from which data are read and written back to. Conversion to and from the more traditional uvfits format is also supported. While there is no standard format for storing VLBI data, support for a handful of commonly used data formats will be made available.

We load the necessary modules first.

relativepath = "../../../"

include(joinpath(relativepath, "src", "Anime.jl"))
using .Anime
#using Anime

In manual mode

In manual mode, the function msfromconfig is used to create an MS from scratch, with the observation and site parameters passed as arguments. The casatools python library is used under the hood.

msname = "eht.ms"
mode = "manual"
stations = joinpath(relativepath, "inputs", "eht_2017.stations")
casaanttemplate = joinpath(relativepath, "inputs", "antenna_table.template")
spw_centrefreq = [229.0e9]
spw_bw = [2.0e9]
spw_channels = [32]
sourcedict = Dict{String, Any}("M87" => Dict{String, String}("RA"=>"12h30m49.42", "Dec"=>"+12.23.28.04", "epoch"=>"J2000"))
starttime = "UTC,2021/04/28/00:00:00.00"
exposure = 1.0
scans = 2
scanlengths = [900.0, 600.0]
scanlag = 300.0
autocorr = false
telescopename = "VLBA"
feed = "perfect R L"
shadowlimit = 1e-6
elevationlimit = "10deg"
stokes = "RR RL LR LL"
delim = ","
ignorerepeated = false

msfromconfig(msname, mode, stations, casaanttemplate, spw_centrefreq, spw_bw, spw_channels, sourcedict, starttime, exposure, scans, scanlengths, scanlag;
 autocorr=autocorr, telescopename=telescopename, feed=feed, shadowlimit=shadowlimit, elevationlimit=elevationlimit, stokes=stokes,
 delim=delim, ignorerepeated=ignorerepeated)

Python: True

The above step creates a fully functional MS that can be used for further processing.

In uvfits mode

This method accepts an existing uvfits file (e.g. output by eht-imaging) and uses CASA to convert between the two formats. This is done via msfromuvfits:

uvfits = joinpath(relativepath, "inputs", "uvfitsfiles", "hops_lo_3601_M87+zbl-dtcal_selfcal.uvfits")
msname = "eht.ms"
mode = "uvfits"

msfromuvfits(uvfits, msname, mode)

Python: True

It is the responsibility of the user to ensure that the input uvfits file contains all the necessary information that CASA would need to create an MS. eht-imaging output files are consistent with these specifications.

A helper function to convert an MS back to uvfits format is also provided:

msname = "eht.ms"
uvfits = "eht.uvfits"
datacolumn = "data"

mstouvfits(msname, uvfits, datacolumn)

[ Info: Creating eht.uvfits from eht.ms...

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