GUANO, NITRATES, and GLIMPSE: The Pipelines Powering Multi-Messenger Astronomy

In this episode, we dive into the cutting-edge of time-domain and multi-messenger astrophysics with a deep look at BAT-GLIMPSE, a revolutionary new open-source pipeline developed for the Neil Gehrels Swift Observatory.

Historically, Swift's Burst Alert Telescope (BAT) suffered from a critical blind spot: its onboard triggering capability is intentionally disabled whenever the spacecraft is slewing (moving between targets) to prevent false alarms. With the observatory taking on more Target of Opportunity observations, the spacecraft spends more time slewing, reducing its chance to serendipitously catch Gamma-Ray Bursts (GRBs). Enter BAT-GLIMPSE (Gamma-ray Localization using Imaging and Mosaic techniques for Pointing and Slew Epochs).

We explore how this fully autonomous system uses advanced coded-mask imaging and mosaic techniques to recover arcminute positions of high-energy transients even while the telescope is in motion. We also break down how GLIMPSE works in perfect synergy with two other powerful ground-based systems:

• GUANO (Gamma-Ray Urgent Archiver for Novel Opportunities): An automated infrastructure that commands on-demand downlinks of time-tagged event (TTE) data around external triggers.
• NITRATES (Non-Imaging Transient Reconstruction and Temporal Search): A highly sensitive, likelihood-based pipeline that hunts for faint, sub-threshold GRBs. While extremely powerful, NITRATES is limited to periods when the spacecraft is in a stable, stationary pointing mode.

By seamlessly filling the gap left by slew intervals, BAT-GLIMPSE and NITRATES together are estimated to double the onboard arcminute-localization rate of Swift-BAT. We'll also discuss the real-world impact of GLIMPSE during the fourth LIGO-Virgo-KAGRA (LVK) observing run, where it operated in extreme low-latency to hunt for gamma-ray counterparts to gravitational waves—specifically in response to pre-merger alerts through the ULTRA-Swift project.

Reference Article:

Ronchini, S., Parsotan, T., DeLaunay, J., & Kennea, J. A. (2026). Swift gives a new BAT-GLIMPSE: Gamma-ray Localization using Imaging and Mosaic techniques for Pointing and Slew Epochs.

Acknowledements: Podcast prepared with Google/NotebookLM. Illustration credits: Spectrum Astro