Week 18 of the Early Operations system optimization period
This week marked the start of the near-real-time public alert stream. Throughout the week, the team used a special configuration of the Feature Based Scheduler (FBS) to acquire hundreds of repeated observations in multiple bands for three target fields with available template coverage to support difference image analysis, namely, Euclid Deep Field South (two adjacent pointings), COSMOS, and part of the Virgo galaxy cluster near M49 that was featured in the Rubin First Look images. This “alert-intensive” observing strategy was designed to provide a full-scale test of the Prompt Processing system, to exercise interactions with the community alert brokers, and to produce a unique fast-cadence set of observations for the science community. Team members supporting nighttime operations from Cerro Pachón and around the world were thrilled to see candidate supernovae, variable stars, active galactic nuclei, and Solar System objects appearing on the broker platforms within minutes of the exposures being acquired. Documentation on Prompt products is available at https://prompt-products.lsst.io/. The special “alert-intensive” observations concluded on the night of Thursday 26 February 2026.
Looking ahead into March, the team is preparing for a multi-week period of sustained pre-LSST observations using an FBS configuration similar to the baseline (v5.1) LSST survey strategy to assess the current system performance, in particular, the average effective survey speed and distribution of delivered image quality. Routine alert production will continue in this observing mode, but at the “natural” level for the LSST cadence given the current availability of templates derived from observations during the on-sky commissioning campaign and Early Operations, primarily in the LSST Deep Drilling Fields. The current plan is to begin the sustained pre-LSST observations by Saturday 7 March 2026, with intermittent pre-LSST observations during the next week.
One night of engineering downtime is planned for 4 March 2026. Several dedicated on-sky engineering tests are planned for the period between 27 February 2026 and 6 March 2026. The currently installed filter set is grizy with the next filter swap to exchange y for u currently planned for 10 March 2026.