  Are we alone? Answering this ageless question will be a major focus for
astrophysics in coming decades. Our tools will include unprecedentedly large
UV-Optical-IR space telescopes working with advanced coronagraphs and
starshades. Yet, these facilities will not live up to their full potential
without better detectors than we have today. To inform detector development,
this paper provides an overview of visible and near-IR (VISIR;
$\lambda=0.4-1.8~\mu\textrm{m}$) detector needs for the Advanced Technology
Large Aperture Space Telescope (ATLAST), specifically for spectroscopic
characterization of atmospheric biosignature gasses. We also provide a brief
status update on some promising detector technologies for meeting these needs
in the context of a passively cooled ATLAST.
