Simulating Observations in CASA

Overview

This page contains tutorials on how to simulate data in CASA. The two main CASA tasks that are used for this are simobserve and simanalyze. CASA includes configuration files for a large number of interferometers (ALMA, VLA, VLBA, ATCA, CARMA, SMA, PdBI and WSRT).

For ALMA, the Guide to Simulating ALMA Data gives an introduction to ALMA simulations, and discusses their relevance to ALMA observing proposals. The task simalma is available to simplify the process of simulating data that combines the 12-m Main Array and the ACA.

If you are a new user of CASA, take a look at CASA Docs (the official CASA Documentation).

If you are new to CASAguides, start with How To Use A CASAGuide.

General introduction to CASA simulations

Simulating interferometric observations in CASA proceeds in the following steps:

1. Make a model image. The model image is a representation of the sky brightness distribution that you would like to simulate observing, stored initially as a FITS file. There are several paths to making the FITS file, discussed below.
2. Generate uv data with the simobserve task.
3. Image the simulated observation with the simanalyze task.

This page on "Introduction to CASA simulations" provides a detailed introduction on how to simulate interferometric data in CASA.

Tutorials

A detailed overview of how to simulate data in CASA is given in the "Simulation" pages of the CASA Docs documentation. The following tutorials provide additional examples:

Last updated for
CASA 5.4.1	Simulating ngVLA Data
	This tutorial shows how to create simulated data for the next generation Very Large Array (ngVLA) either by using simobserve or the sm toolkit. Additionally, it shows how to estimate the scaling parameter for adding thermal noise using the sm.setnoise function and the simplenoise parameter.
	Previous Versions: None
CASA 6.6.1	Simalma
	This tutorial demonstrates how to use simalma, a task that simplifies simulations that include the main 12m array plus the ACA. Like the previous guide, this one is of particular interest to those wishing to explore multi-component ALMA observations.
	Previous Versions: 6.5.4 | 6.4.1 | 6.1.1 | 5.4 v2 | 5.4 | 5.1 | 4.4 | 4.3 | 4.2 | 4.1 | 4.1 (original)
CASA 6.5.4	ACA Simulation
	A tutorial for simulating ALMA observations that use multiple configurations or use the 12-meter array in combination with the ALMA Compact Array. This tutorial demonstrates combining data from each ALMA component "by hand". This guide is of particular interest to those wishing to explore using the 12-m array in combination with the ACA, and those interested in combining data from multiple 12-m array configurations.
	Previous Versions: 5.4 v2 | 5.4 | 5.1 | 4.4 | 4.3 | 4.2 | 4.1 | 4.0 | 3.4 | 3.3
CASA 6.5.3	Simulation Guide Component Lists
	Tutorial for simulating data based on multiple sources (using both a FITS image and a component list). If you are interested in simulating from a list of simple sources (point, Gaussian, disk), rather than or in addition to a sky model image, then read the considerations here.
	Previous Versions: 5.4 | 5.1 | 4.4 | 4.3 | 4.2 | 4.1 | 4.0 | 3.4 | 3.3
CASA 5.4	Protoplanetary Disk Simulation
	A sky model with a lightly annotated script that simulates a protoplanetary disk. Uses a theoretical model of dust continuum from Sebastian Wolff, scaled to the distance of a nearby star. This is another fairly generic simulation - if you're short on time, you probably don't need to go through this one and the New Users guide, but it can be useful to go through multiple examples.
	Previous Versions: 5.1 | 4.4 | 4.3 | 4.2 | 4.1 | 4.0 | 3.4 | 3.3 | 3.2 | 3.1
CASA 6.5.4	Protoplanetary Disk Simulation - VLA
	This tutorial explains the steps for simulating VLA observations using the same protoplanetary disk sky model that was used for the analogous ALMA tutorial. Observational and analysis parameters are changed step by step and the results are compared to the VLA exposure calculator.
	Previous Versions: 6.4.1 | 6.2.0 | 5.7.0 | 5.5.0 | 5.4.0 | 5.3.0
	Advanced: Corrupting Simulated Data (Simulator Tool)
	simobserve calls methods in the simulator tool. For advanced CASA users, the simulator tool has methods that can add to simulated data: phase delay variations, gain fluctuations and drift, cross-polarization, and bandpass and pointing errors. simulator also has more flexibility than simobserve in adding thermal noise. The tutorial linked from this page describes the simulation of data using the task interface only. The simulator tool is part of the CASA toolkit. An examples of advanced techniques for corrupting a simulated MeasurementSet can be found in this CASA Guide on Corrupting Simulated Data (Simulator Tool).
	Previous Versions: none

Archived Simulation Guides

Last updated for
CASA 4.4	Simulation Guide for New Users
	A fully annotated tutorial that uses a Spitzer SAGE 8 micron continuum image of 30 Doradus and scales it to greater distance.
	Previous Versions: 4.3 | 4.2 | 4.1 | 4.0 | 3.4 | 3.3
CASA 4.0	M51 at z = 0.1 and z = 0.3
	A fully annotated tutorial that uses a BIMA-SONG cube of a nearby galaxy and scales it to greater distance.
	Previous Versions: 3.4 | 3.3 | 3.2 | 3.1
CASA 3.4	N891 simdata
	A sky model, script, and discussion that simulates a nearby edge-on spiral galaxy. Uses a galactic CO cube from the Galactic Ring Survey and places it at 10Mpc. The data are similar to what NGC891 would look like if it were observable from the southern hemisphere.
	Previous Versions: 3.3 | 3.2
CASA 4.4	Einstein-Face
	A sky model and lightly annotated script that simulates the face of Einstein as seen by ALMA. Uses a non-science image to demonstrate the effects of spatial filtering by ALMA.
	Previous Versions: 4.3 | 4.2 | 4.1 | 4.0 | 3.4 | 3.3 | 3.2 | 3.1
	Example input images
	Example output simulations

User Feedback

We welcome input on developing the CASA simulator. Contact https://help.almascience.org if you would like to volunteer your input.