imSim is a software package that simulates the LSST telescope and survey. It produces simulated images from the 3.25 Gigapixel camera which are suitable to be processed through the LSST Data Management pipeline. imSim takes as an input a catalog of astronomical sources along with information about how the light is distorted on the way to Earth including lensing and extinction information. The images which are produced include the systematic effects of the atmosphere, optics and sensors on the observed PSF.
imSim calls the GalSim library for astronomical object rendering and is designed to be used inside of the LSST Data Management and LSST Simulation Group software environment. It is not a stand alone program. It requires a working LSST software stack to build and run.
Communication with the imSim development team should take place through the imSim GitHub repository which is part of the DESC GitHub organization. Other questions can be directed to Chris Walter at Duke University.
Details on the models implemented by imSim including their validations can be found in the imSim Feature Matrix.
Set up the lsst_sims distribution, then enter the following from
this repo directory:
$ eups declare -r . imsim -t current
$ setup imsim
$ scons
Once you have eups declared a package like this, you only need to
execute the setup imsim command, and that command can be issued from
any directory. The scons build step needs only to be re-run if a
new command line executable is added to the bin.src folder.
The executables in the bin folder should be in your path and so
should be runnable directly from the command line:
$ imsim.py --help
usage: imsim.py [-h] [-n NUMROWS] [--outdir OUTDIR] [--sensors SENSORS]
[--config_file CONFIG_FILE]
[--log_level {DEBUG,INFO,WARN,ERROR,CRITICAL}]
[--psf {DoubleGaussian,Kolmogorov,Atmospheric}]
[--disable_sensor_model] [--file_id FILE_ID]
[--create_centroid_file] [--seed SEED] [--processes PROCESSES]
[--psf_file PSF_FILE] [--image_path IMAGE_PATH]
instcat
positional arguments:
instcat The instance catalog
optional arguments:
-h, --help show this help message and exit
-n NUMROWS, --numrows NUMROWS
Read the first numrows of the file.
--outdir OUTDIR Output directory for eimage file
--sensors SENSORS Sensors to simulate, e.g., "R:2,2 S:1,1^R:2,2 S:1,0".
If None, then simulate all sensors with sources on
them
--config_file CONFIG_FILE
Config file. If None, the default config will be used.
--log_level {DEBUG,INFO,WARN,ERROR,CRITICAL}
Logging level. Default: INFO
--psf {DoubleGaussian,Kolmogorov,Atmospheric}
PSF model to use. Default: Kolmogorov
--disable_sensor_model
disable sensor effects
--file_id FILE_ID ID string to use for checkpoint filenames.
--create_centroid_file
Write centroid file(s).
--seed SEED integer used to seed random number generator
--processes PROCESSES
number of processes to use in multiprocessing mode
--psf_file PSF_FILE Pickle file containing for the persisted PSF. If the
file exists, the psf will be loaded from that file,
ignoring the --psf option; if not, a PSF will be
created and saved to that filename.
--image_path IMAGE_PATH
search path for FITS postage stamp images.This will be
prepended to any existing IMSIM_IMAGE_PATH environment
variable, for which $CWD is included by default.
imSim is currently still considered beta code. A list of tagged versions and pre-releases of this package can be found here, with the master branch including the most recent (non-tagged) development.
This software was developed within the LSST DESC using LSST DESC resources, and so meets the criteria given in, and is bound by, the LSST DESC Publication Policy for being a “DESC product”. imSim is licensed with a BSD 3-Clause "New" or "Revised" License as detailed in the included LICENSE file.
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