projectis the root file name for
simmosoutput (ms, images, etc)
integrationset when you want to observe and for how long.
refdateis the middle of the track.
nchanspecify the frequency information for the output which will be interpolated from the input. There is no "continuum" mode in ALMA as there was on the old VLA, so you just specify
nchan=1 if you want a continuum simulation.
relmarginspecify where you want to observe, and how to space the pointings of the mosaic, since you'll probably do a mosaic.
imsizeare the parameters for the output image. Even if you don't care about producing an image, but just want to simulate visibilities,
simmosuses these two parameters to set the field of view and lay out mosaic pointings.
checkinputs="yes"produces a graphical output with your scaled input model and the primary beams of your desired mosaic overlaid (and the elevation of the source as a function of time and coming in the future a spectral window with atmospheric transmission).
checkinputs="only"produces the same window, and then stops before running the time-consuming visibillity calculation and deconvolution. This is recommended if you are trying a new image size, or mosaic parameters, etc. Get it all right and then run the actual simulation.