telsim – building a Measurement Set¶

telsim builds a simulated Measurement Set (MS) from a telescope layout: it lays out antennas, computes uvw for the requested time/frequency grid, and writes the standard MS subtables (ANTENNA, FIELD, SPECTRAL_WINDOW, POINTING, …) with no visibility data yet – that’s what skysim – predicting visibilities fills in afterwards.

Required inputs¶

ms: the name of the MS to create.
telescope: the telescope array layout (see simms telsim --list for the bundled layouts under src/simms/telescope/layouts/).
direction: the pointing direction, written to FIELD.PHASE_DIR / POINTING.DIRECTION (see Measurement Set conventions for why these differ).
starttime, dtime, ntimes: the observation’s time grid.
startfreq, dfreq, nchan: the observation’s frequency grid.

Usage¶

$ 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

List the available telescope layouts:

$ simms telsim --list

See Command-line interface for the full option reference.

Where to next¶

skysim – predicting visibilities – simulate visibilities into the MS telsim just created.
Measurement Set conventions – how simms reads/writes MS metadata, and the distinction between phase centre and pointing centre.