Early Science Program

"Early science" is defined as any science enabled by Rubin for its community prior to the first annual data release, Data Release 1 (DR1), of the Legacy Survey of Space and Time (LSST).

The goal of the program is to support the community as they develop their LSST analysis software and workflows, and to enable high-impact science as soon as possible

The program includes:

• a series of Data Previews produced by reprocessing of science-grade commissioning data,
• a progressive ramp-up of the alert stream and Prompt Products availability, and
• an incremental template-generation strategy to support alert production.

This page summarizes "Rubin Observatory Plans for an Early Science Program", Rubin Tech Note 11 (RTN-011; DOI 10.5281/zenodo.14846372).

Data previews

A series of data releases based on the commissioning data, which progressively increase in size and complexity as a ramp up to the first annual data release.

LSSTComCam commissioning

The on-sky commissioning campaign using the LSST Commissioning Camera (LSSTComCam) began on 24 October 2024 and ended on 11 December 2024, lasting a total of 7 weeks. It included observations to support both engineering and science pipelines commissioning. The science-grade LSSTComCam observations were processed and released as Data Preview 1.

LSSTCam commissioning and Science Validation surveys

The acquisition of images with the LSST Camera (LSSTCam) began on 17 April 2025 and continued through 21 September 2025. The initial images consisted only of small-field survey visits (a subset of which formed part of the Rubin First Look campaign). The Science Validation (SV) surveys began acquiring visits in a manner consistent with the planned LSST operations on 20 June 2025, including a wide-field region and deep drilling fields. The subset of these science-grade LSSTCam observations will be processed and released as Data Preview 2.

Resources to learn more about the history and progression of commissioning and the SV surveys:

• Science Validation survey summary (30 September 2025)
• monthly commissioning monthly status updates
• weekly technical updates about commissioning
• nightly scheduler reports

See also Section 2 of RTN-011 for a summary of the commissioning and SV surveys.

Data products and timeline

Data Preview 0 (DP0; available now) is based on simulated LSST-like data. It includes images and catalogs for Galactic and extragalactic objects (including variable stars and supernovae), and catalogs of moving objects.

Data Preview 1 (DP1; available now) is based on data from LSSTComCam. It includes processed visit images and source catalogs, deep coadd images and object catalogs, the results of difference image analysis, and catalogs of moving objects.

Data Preview 2 (DP2; mid-2026) will be based on data from LSSTCam. It will include processed science-grade commissioning data, and the same full suite of data products as DP1 (cell-based coadds remain a stretch goal).

Data Release 1 (DR1; by Feb 2028) will be based on the first year of data taken as part of the 10-year LSST survey. Processing is anticipated to take one full year, and will deliver the full suite of data products (including cell-based coadds and a shear catalog).

See Section 3 of RTN-011 for details on the plan for the Data Previews.

Prompt data products

Prompt data products are the result of Difference Image Analysis (DIA) and include processed visit images, difference images, and catalogs of detections in difference images (DiaSources), their associated astrophysical objects (DiaObjects), and Solar System objects (SSObjects). An alert is issued for each newly-detected DiaSource.

Alert production and template generation

Prior to DR1, the alert stream cannot run at full scale because DIA requires template images, which are constructed as part of an annual data release.

In order to produce alerts on a limited scale in at least some sky regions, and to enable early science in the time-domain, the plan is as follows.

1. Generate templates using commissioning and early operations LSSTCam data.
2. Incorporate additional templates incrementally during the first year of survey operations.

The first Rubin alerts are expected to begin between December 2025 and February 2026 (Rubin Tech Note RTN-061 describes the criteria for sending the first Rubin alerts). Alert production during Early Science may be produced with higher latency, but once begun, alert production will proceed continuously.

Solar System discoveries will be reported to the Minor Planet Center on an ad-hoc basis during Early Science.

Learn more about alerts and brokers.

Prompt Products Database (PPDB)

The DiaSource, DiaObject, SSObject, and SSSource catalogs that result from Prompt processing are stored in the PPDB. These contents are very similar to the cumulative content in all released alerts. Due to ongoing technical development, the PPDB will not be available until mid-2026 (i.e., several months after the alert stream).

Prompt images

Prompt-processed visit images and difference images will be released during Early Science, and will be subject to the 80-hour embargo period. The start date, cadence, and latency of the release of prompt images remains to be determined.

Prompt source catalog

As a temporary measure to support Early Science, source detection will be run on all Prompt-processed visit images and the results made available as a Source catalog that accompanies the visit images on an 80-hour timescale. This temporary measure would end with the release of the DR1 Source catalog.

See Section 4 of RTN-011 for details on the Prompt data products during Early Science.

Questions?

Use the Support and Early Science categories in the Rubin Community Forum.