Getting Started

This page shows how to generate simulated telescope images with SImSiT.

SImSiT is an image simulation library for stars and satellites. A typical workflow consists of:

  1. choosing or editing a configuration file,

  2. running the simulation script, and

  3. inspecting the generated image and reference outputs.

Quick start

To generate a basic example dataset, run:

python scripts/simulate.py config/sidereal.yaml

This creates output under the directory specified by outdir in the configuration file. By default, simulated images are written to an images/ subdirectory and reference products are written to a reference/ subdirectory.

Configuration

Example configuration files are provided in the config/ directory.

Common settings include:

  • outdir: output directory for generated files

  • n_obs: number of simulated observations

  • n_example: number of example/reference records to include in exported example metadata products

  • instrument: detector and optical model parameters

  • conditions: observing conditions such as seeing, sky brightness, and zeropoint offsets

  • catalog: star catalog configuration

  • tracker: boresight and tracking model configuration

Example configurations

Sidereal-tracking example

python scripts/simulate.py config/sidereal.yaml

This produces simulated observations using a sidereal-tracking configuration.

Target-tracking example

python scripts/simulate.py config/target.yaml

This produces simulated observations using a target-tracking configuration.

Empty-field target-tracking example

python scripts/simulate.py config/empty_target.yaml

This example can be used to generate target-tracking images without a simulated satellite source.

Output products

A typical simulation writes:

  • images/*.fits: simulated image products

  • images/sample_metadata_<N>.yaml: example metadata for a subset of images

  • images/reference_truth_<N>.fits: reference truth tables for a subset

  • reference/*.wcs.fits: reference WCS at exposure start

  • reference/*.wcst.fits: reference WCS at exposure end

  • reference/sample_metadata.yaml: metadata for the full simulated set

  • reference/reference_truth.fits: reference truth tables for the full set

External catalog data

Some simulations use locally stored Gaia catalog files. These catalog files are not distributed with SImSiT and must be obtained separately.

If you are using GaiaStarCatalog, configure:

  • catalog.gaia_dir: path to the local Gaia catalog directory

The expected directory layout and required columns should match the format used by the GaiaStarCatalog reader in the Python package.

Notes

The configuration files in config/ are examples and may reflect particular instrument or observing assumptions. Review them before using them as templates for new simulations.