The Advanced Particle-astrophysics Telescope (APT) is a mission concept for a space-based
gamma-ray telescope whose capabilities include prompt localization of gamma-ray bursts (GRBs)
to support multi-wavelength and multi-messenger astrophysics. ADAPT — APT’s balloon-borne
prototype — can localize GRBs in well under a second using on-board computing hardware.
ADAPT will partner with ground-based, fast-slewing optical telescopes, rapidly providing alerts
that enable the partner to observe a short-duration burst within a few seconds of detection.
In this work, we investigate the utility of having ADAPT issue progressively more accurate location
estimates for a GRB as detected Compton events from the burst accumulate over time. We develop
a computational model to estimate how frequently ADAPT can compute these estimates, finding
that it can do so at least every 150 ms for a 1 MeV/cm2 burst on a low-power quad-core Intel
Atom processor. We then assess how quickly ADAPT’s localization improves as it observes
more events and show that a partner instrument can slew to a burst’s location faster if it exploits
progressive location estimates than if it waits for one final estimate. Real-time, on-board source
localization thus has a role to play in cooperative observation of gamma-ray transients even when
data collection time, rather than computing time, dominates the cost of detection.