Bart Salazar & Brad Devowe
Community contributors to Roman‑era science infrastructure
The Nancy Grace Roman Space Telescope will transform time‑domain astronomy in the Galactic bulge, enabling the first large‑scale census of isolated stellar remnants—black holes, neutron stars, and free‑floating planets—through microlensing and astrometric measurements.
However, Roman cannot achieve this goal in isolation.
This white paper argues that three small, carefully curated historical datasets, ingested into the Mikulski Archive for Space Telescopes (MAST), will unlock Roman’s full discovery potential. Together, these datasets form a microlensing trifecta—providing the temporal, astrometric, and parallax context Roman needs to convert detections into definitive physical measurements.
Rather than proposing a single massive archive ingestion, we demonstrate why targeted, low‑cost, community‑curated datasets outperform monolithic solutions in scientific return, accessibility, and mission readiness.
Microlensing is fundamentally a time‑integrated phenomenon.
Key physical parameters—lens mass, distance, and velocity—are not fully constrained by any single observation. Long‑timescale events, especially those produced by massive dark lenses, unfold over years and often require multi‑epoch, multi‑platform context to resolve degeneracies.
- Ground‑based surveys such as OGLE and KMTNet provide long temporal baselines
- Space‑based missions such as Spitzer provide parallax leverage
- Roman will add precise astrometric microlensing measurements
No one dataset is sufficient.
Together, they are transformative.
Roman will measure the angular Einstein radius (θE) for thousands of microlensing events—an ability unmatched by any previous mission. Yet θE alone does not yield lens mass.
To determine mass definitively, Roman measurements must be paired with:
- Historical microlens parallax (πE) data
- Long‑baseline light‑curve characterization
- Pre‑identified high‑priority candidates for dark remnants
Without these inputs, Roman risks rediscovering candidates without the ability to immediately confirm their nature.
Archives are not passive repositories.
They are active components of discovery.
Role: Candidate identification and astrometric context
Contribution:
- Identifies rare, long‑duration events (tE ≳ 100–300 days)
- Incorporates Gaia proper motions and parallaxes
- Flags high‑probability black hole and neutron star lenses
This dataset narrows Roman’s search space to the most physically informative events.
Role: Mass degeneracy breaking
Contribution:
- Provides πE measurements from a ~1 AU space‑based baseline
- Enables direct mass determination when combined with Roman θE
- Preserves a unique, no‑longer‑repeatable observing geometry
This dataset transforms Roman astrometry into definitive mass measurements.
Role: Temporal completeness and anomaly recovery
Contribution:
- Combines long‑baseline OGLE monitoring with high‑cadence KMTNet coverage
- Recovers short‑duration features missed by single surveys
- Enables robust modeling of complex events
This dataset ensures Roman inherits a science‑ready temporal record, not fragmented light curves.
| Approach | Massive Ingestion | Trifecta Approach |
|---|---|---|
| Cost | High | Very Low |
| Review Complexity | Large | Minimal |
| Community Reuse | Limited | Broad |
| Scientific Focus | Diffuse | Targeted |
| Time to Impact | Long | Immediate |
Each dataset:
- Is < 1 GB
- Is public
- Serves a distinct, non‑redundant role
- Aligns directly with Roman’s primary Galactic science goals
Together, they form discovery infrastructure, not a single‑use product.
Roman’s success will not be measured solely by photons collected, but by:
- How quickly discoveries can be validated
- How broadly the community can participate
- How effectively past and future missions are connected
MAST’s role is not just to store Roman data—but to activate it.
By hosting these datasets as High‑Level Science Products (HLSPs), MAST enables:
- Immediate co‑analysis
- Reproducible workflows
- Democratized access to high‑impact science
This trifecta proposal was assembled by two members of the public—not as outsiders, but as engaged participants in the Roman science ecosystem.
We believe that:
- Space science belongs to everyone
- Good data organization accelerates discovery
- Flagship missions are strongest when communities are included early
These submissions are a small but concrete example of that philosophy in action.
Some discoveries don’t happen because we look harder.
They happen because we connect what we already have.
This trifecta is about making those connections—so Roman can turn fleeting lensing events into a lasting census of the invisible universe.
This project is released under the MIT License.
See the LICENSE file for details.