SPB2 – Super Pressure Balloon 2

SPB2 (Super Pressure Balloon 2) is part of the JEM-EUSO International Program (Joint Experiment Missions for Extreme Universe Space Observatory), a mission concept devoted to the observation and study from space of the cosmic rays at the highest energies (UHECRs, Ultra High Energy Cosmic Rays) above 10¹⁹eV.

SPB2 is the project for a long duration balloon flight of the JEM- EUSO Collaboration that follows previous balloon flights (EUSO-Balloon in 2014 and EUSO-SPB1 in 2017). This is a second generation stratospheric balloon instrument for the detection of UHECRs via the fluorescence technique and of Ultra High Energy neutrinos via Čerenkov emission. SPB2 is a precursor mission for instruments like the proposed space mission Probe Of Extreme Multi-Messenger Astrophysics (POEMMA). The purpose of such a future space-based observatory is to measure UHECRs and UHE neutrinos with high statistics and uniform exposure.

SPB2 is designed with two mirror Schmidt telescopes, each optimized for their respective observational goals.

The Fluorescence Telescope looks at the nadir to measure the fluorescence emission from UHECRs, while the Čerenkov Telescope is optimized for fast signals (10 ns) and points near the Earths limb. This allows for the measurement of  Čerenkov light from Extensive Air Showers caused by Earth skimming UHE neutrinos if pointed slightly below the limb or from UHECRs if observing slightly above.

The expected launch date of EUSO-SPB2 is Spring 2023 from Wanaka, NZ with target duration of up to 100 days. Such a flight would provide hundreds of UHECR Čerenkov signals in addition to tens of UHECR fluorescence tracks. Neither of these kinds of events have been observed from either orbital or suborbital altitudes before, making EUSO-SPB2 crucial to move forward towards a space based instrument. It will also enhance the understanding of potential background signals for both detection techniques.