Quickstart¶

This walkthrough builds a small Measurement Set (MS) from scratch and simulates visibilities into it from an ASCII sky model.

1. Create an MS¶

telsim – building a Measurement Set builds the MS – antenna layout, time/frequency grid, and pointing – with no visibility data yet:

$ simms telsim --telescope kat-7 \
    --direction "J2000,0h24m20s,-30d12m33s" \
    --starttime 2024-03-14T06:15:10 --dtime 8 --ntime 100 \
    --startfreq 900MHz --dfreq 1MHz --nchan 64 obs.ms

2. Write a sky model¶

An ASCII sky model is a catalogue of sources, one per line. A single point source looks like:

#format: name ra dec stokes_i
src1 0h24m20s -30d12m33s 1.0

3. Predict visibilities¶

skysim – predicting visibilities predicts model visibilities from the sky model into a data column on the MS created above:

$ simms skysim --ascii-sky skymodel.txt --column DATA obs.ms

Chain both steps¶

telsim and skysim can be chained into one invocation with --chain (see Command-line interface):

$ simms --ms obs.ms --chain \
    telsim --telescope kat-7 --startfreq 900MHz --dfreq 1MHz --nchan 64 \
    skysim --ascii-sky skymodel.txt --column DATA

Where to next¶

telsim – building a Measurement Set – telescope layouts, time/frequency grid, pointing.
skysim – predicting visibilities – sky model schemas, FITS models, noise, column add/subtract, chunking.
Measurement Set conventions – how simms reads/writes MS metadata.
Command-line interface – full option reference.