Scientists have developed BAT-GLIMPSE, a new open-source software tool that enables the Burst Alert Telescope (BAT) aboard the Swift observatory to localize gamma-ray bursts (GRBs) even when the spacecraft is performing slew maneuvers. Previously, Swift-BAT's onboard triggering system was disabled during these movements, preventing autonomous detection and localization of transients during these intervals. BAT-GLIMPSE employs coded-mask imaging and mosaic techniques, automatically selecting the appropriate analysis based on spacecraft attitude, thereby enabling searches for transient sources during both pointing observations and spacecraft slews.

The performance of BAT-GLIMPSE was validated on a sample of 66 previously reported GRBs. The software successfully recovered arcminute positions for 43 of these events, with typical offsets of approximately 5 arcminutes, consistent with published localizations. Notably, approximately 88% of the GRBs that occurred during spacecraft slews were recovered through BAT-GLIMPSE's imaging or mosaic analyses. This demonstrates the new system's ability to fill a critical gap in GRB detection.

BAT-GLIMPSE played a crucial role during the fourth LIGO-Virgo-KAGRA observing run (O4) in the search for gamma-ray counterparts to gravitational waves, particularly in response to pre-merger alerts that triggered Swift spacecraft slews with extremely low latency. Operating synergistically with NITRATES, another analysis tool, BAT-GLIMPSE is estimated to double Swift-BAT's onboard arcminute-localization rate, unlocking the full potential of the Swift mission for time-domain and multi-messenger astrophysics.