Experienced tier: Challenge data is now live on the Roman Research Nexus and Hugging Face. Submissions close October 2, 2026.

Beginner tier: Submissions are now closed, but the data remain available on Hugging Face.

Sign Up for RMDC26
Sign-up is open until the Experienced tier closes on October 2, 2026.

RMDC26 is a community challenge to model simulated Roman microlensing data ahead of the mission’s Galactic Bulge Time Domain Survey. The goal is to broaden participation, standardize best practices, and spur innovation in microlensing modeling and tooling.

Roman is expected to detect tens of thousands of microlensing events during its prime mission and thousands of exoplanets, probing regions of exoplanet parameter space beyond earlier surveys.

Why participate:

  • Learn or sharpen microlensing modeling skills
  • Try and compare open‑source tools on realistic data
  • Contribute new ideas and pipelines before launch

The data in this challenge is intended to be a semi-realistic representation of the microlensing data volume and type expected from the Roman Galactic Bulge Time Domain Survey.

The challenge launched at AAS 247, where we hosted a workshop covering various aspects of the Data Challenge. The workshop took place on Sunday, January 4, from 9:00 AM to 5:00 PM MST. It was not offered in a hybrid format, but all workshop materials are available online at the preceding link. Similar hands-on sessions will be offered at the 2026 Sagan Summer Workshop, which participants can attend in person, remotely live, or remotely on demand.

Important Dates

Milestone Date
Challenge sign-up opened Early December 2025
Kick-off workshop at AAS 247 January 4, 2026
Beginner submission deadline June 26, 2026
Experienced submission deadline October 2, 2026
Evaluation begins October 2026
Evaluation panel discussions October 2026
Evaluation panel final reports due November 2026

Challenge Overview

Ground Rules

1) Document dependencies and CPU hours.
2) All developed code should be documented and open source.
3) One final submission per team.
4) Submissions must pass format validation with the submission tool.
5) One designated team lead/contact person.
6) Communication with experienced microlensing researchers is encouraged.

Challenge Tiers

RMDC26 offers two challenge tiers: a Beginner tier for those new to microlensing and an Experienced tier for veteran microlensing researchers. Anyone may participate in either tier, but the Beginner tier is not intended for entire teams with extensive microlensing modeling experience. Teams may make submissions in both tiers.

Participant Goals

1) Classify all targets.
2) Fit appropriate models to the microlensing events and tabulate the parameters derived in each case, optionally including derived physical parameters.
3) Describe the approach taken to modeling; the software and hardware used; and any innovations in modeling or classification made in response to the challenge.
4) Optional: provide plotted output for each model and posterior samples.

Submission

Submissions are validated using the microlens-submit tool. It validates and packages submissions and creates draft dossiers so you can preview how your submission will look to evaluators. It is also useful for managing your many events and solutions and tracking your progress. You can use this tool through the CLI or Python API. It installs as a Python package via pip:

# PyPI
pip install microlens-submit

# Conda-Forge
conda install microlens-submit

The microlens-submit documentation includes detailed specifications for how to create a submission. Strict adherence to the submission criteria is required, as much of the evaluation process is automated.

Evaluation

The evaluation panel will assess each team’s entry on the following criteria:

# Criterion Points
1 Accuracy of model parameters 5
2 Number of events modeled 5
3 Software/computational efficiency 5
4 Innovation 5
5 Broadening the field by bringing in new researchers 5

You can find a copy of the evaluation rubric here.

Microlensing Resources and References

Contact