  The Probe Of Extreme Multi-Messenger Astrophysics (POEMMA) is designed to
accurately observe ultra-high-energy cosmic rays (UHECRs) and cosmic neutrinos
from space with sensitivity over the full celestial sky. POEMMA will observe
the extensive air showers (EASs) from UHECRs and UHE neutrinos above 20 EeV via
air fluorescence. Additionally, POEMMA will observe the Cherenkov signal from
upward-moving EASs induced by Earth-interacting tau neutrinos above 20 PeV. The
POEMMA spacecraft are designed to quickly re-orientate to follow up transient
neutrino sources and obtain unparalleled neutrino flux sensitivity. Developed
as a NASA Astrophysics Probe-class mission, POEMMA consists of two identical
satellites flying in loose formation in 525 km altitude orbits. Each POEMMA
instrument incorporates a wide field-of-view (45$^\circ$) Schmidt telescope
with over 6 m$^2$ of collecting area. The hybrid focal surface of each
telescope includes a fast (1~$\mu$s) near-ultraviolet camera for EAS
fluorescence observations and an ultrafast (10~ns) optical camera for Cherenkov
EAS observations. In a 5-year mission, POEMMA will provide measurements that
open new multi-messenger windows onto the most energetic events in the
universe, enabling the study of new astrophysics and particle physics at these
otherwise inaccessible energies.
