Survey Simulator 2.0

The Survey Simulator (Driver / SSim / Python ossssim) takes a model of orbits and physical parameters of outer Solar System objects and determines which model objects a characterized survey would detect and track.

Provide a model and a survey characterization directory. Fortran and Python interfaces share the same F95 detection engine.

Repository layout

F95/                 Fortran sources, Driver Makefile, F95/tests regressions
src/ossssim/         Python package (src-layout)
tests/               Python unit tests for the simulator
docs/                Characterization format docs and mini examples
examples/            Python scripts and notebooks
data/
  Models/            model inputs: L7model-3.0-9.0, InnerHot.in, HST_model.txt,
                     Resonance_3_2-g.in
  Surveys/           example characterizations: CFEPS, HST, JWST

data/ holds the only copy of these files. F95/tests/{Models,Surveys}, examples/{Models,Surveys} and tests/data/Surveys are symbolic links to it, so the Fortran regression inputs and the examples use the same files. None of it is shipped in the Python package.

Grid-based survey debiasing and the survey-specific follow-up projects live in separate repositories, not shipped with ossssim:

• survey_debias — shared grid-cell debiasing helpers and runner (imports ossssim).
• jwst-tno-followup — Eduardo et al. 2026 JWST Sample A characterization and the full OSSOS v11 / CFEPS characterizations.
• hst-tno-followup — N26 (Napier et al. 2026) and Bernstein 2004/2006 HST survey characterization.

Clone the ones you need next to this tree, or set SSIM_ROOT when running those scripts.

Language-specific guides:

• F95/README.md — build Driver, GiMeObj API, model-file format
• src/README.md — pip install, Python module usage
• docs/README.md — characterization formats (README.formats, Template.eff)

Quick start

Fortran

cd F95
make Driver GIMEOBJ=InnerHotModel
# or: make Driver GIMEOBJ=ReadModelFromFile
Driver < tests/InnerHotModel.in

See F95/README.md and F95/tests/.

Python

pip install .
# or editable: pip install -e .

The install builds the f90wrap extension ossssimlib (_ossssimlib shared library) via setup.py → make -C F95 MODULE=ossssimlib. Runtime code imports ossssimlib (not the older SurveySubsF95 name).

Examples: examples/. Tests: pytest tests/ (with the package installed and Fortran extension available).

Pass a characterization directory path into OSSSSim(...), for example data/Surveys/CFEPS.

Survey data

The model inputs and example characterizations used by the Fortran regressions, the Python tests and the examples are in data/ (see Repository layout), along with the small docs/examples/mini_survey/.

The full OSSOS v11 release characterizations (CFEPS, OSSOS-MA, All_Surveys, All_r_Surveys, Deep_Surveys) and the JWST Sample A characterization used for science runs are kept, unmodified, in the characterization/ directory of the separate jwst-tno-followup project.

Licence

Released under the European Union Public Licence (EUPL). See LICENCE.txt. Provided as-is, with no warranty.

Contact

• Jean-Marc Petit: Jean-Marc.Petit@normalesup.org

Acknowledgement

Cite Petit, J.-M., et al., AJ, Vol 142 ID 131 (2011) if you use the SurveySimulator or the CFEPS L7SyntheticModel-v09 Kuiper belt model.

Survey characterizations and detections — cite the relevant survey papers:

• CFEPS: Petit, J.-M., et al., AJ, Vol 142 ID 131 (2011)
• OSSOS: Bannister et al. (2016) AJ, 152, 70; Bannister et al. (2018) ApJS, 236, 18
• HiLat: Petit et al. (2017), AJ, 153, 236
• MA Survey: Alexandersen et al. (2016), AJ, 152, 111

Overview

The goal is a quantitative comparison between:

A. An orbital and size-distribution model of the outer Solar System
and
B. Those same distributions as observed by a survey.

The simulator biases a model to mimic survey selection (field coverage, magnitude efficiency, rate cuts, tracking). Compare tracked simulated detections to real survey detections with a statistical method of your choice (e.g. Lawler et al., Frontiers in Astronomy and Space Sciences, 2018). Real detections are not required to run the simulator; they are used afterward to validate models.

Architecture: a GiMeObj routine supplies one object per call; Detos1 applies the survey characterization. Link your GiMeObj when building Driver (InnerHotModel, ReadModelFromFile, or your own). Details: F95/README.md.