POEMMA: Probe of extreme multi-messenger astrophysics

Developed as a NASA Astrophysics Probe mission concept study, the Probe Of Extreme Multi Messenger Astrophysics (POEMMA) science goals are to identify the sources of ultra-high energy cosmic rays (UHECRs) and to observe cosmic neutrinos above 20 PeV. POEMMA consists of two satellites flying in loose formation at 525 km altitudes. A novel focal plane design is optimized to observe the UV air fluorescence signal from extensive air showers (EASs)in a stereoscopic UHECR observation mode and the Cherenkov signals from EASs from UHECRs and neutrino-induced τ-leptons in an earth-limb viewing mode. POEMMA is designed to achieve full-sky coverage and significantly higher sensitivity to the highest energy cosmic messengers compared to what have been achieved so far by ground-based experiments. POEMMA will measure the spectrum, composition, and full sky distribution of the UHECRs above 30 EeV to identify the most energetic cosmic accelerators in the universe and study the acceleration mechanism(s). POEMMA will also have sensitivity to cosmic neutrinos by observing the upward-moving air showers induced from tau neutrino interactions in the earth. POEMMA will also be able to re-orient to a Target-of-Opportunity (ToO) neutrino mode to view transient astrophysical sources with unique sensitivity. This paper discusses the science goals, instrument design, mission profile, and the simulated UHECR and neutrino measurement capabilities for POEMMA. (author)