Abstract The Extreme Universe Space Observatory on Super Pressure Balloon 2 (EUSO-SPB2) mission launched from Wanaka, NZ, on May 13th, 2023, and was terminated about 36 hours later over the Pacific Ocean due to a leak in the balloon. The payload included two main instruments. The Fluorescence Telescope (FT) pointed in nadir to search for the first Ultra High Energy Cosmic Rays (UHECR) induced Extensive Air Showers (EAS) signatures in fluorescence light viewed from balloon altitude. A first analysis of our flight data does not indicate any observations of UHECRs. The Cherenkov Telescope (CT) looked for Cherenkov light signatures from EAS. These EAS can be induced by above-the-limb Cosmic Ray (CR) and PeV-scale Earth-emergent neutrinos. By using the Earth as a tau neutrino to tau-lepton converter, EUSO-SPB2 has sensitivities toward these Earth-emergent tau-neutrinos. During the first analysis, several above-the-limb CR candidates were found, demonstrating the instrument’s ability to measure Earth-emergent neutrino signatures. As part of EUSO-SPB2, we planned Target of Opportunity (ToO) observations to follow up on possible neutrino sources by catching parts of the sources’ path across the sky in the CT’s field of view. Possible neutrino source candidates include gamma-ray bursts, tidal disruption events, and other steady or flaring sources. During its descent, there was a loss of control over the payload azimuth rotation, interrupting plans for targeted ToO observations. However, some sources crossed the CT’s field of view during the balloon’s descent. These chance-coincident observations demonstrate the viability of conducting ToO follow-up observations from a near-space environment. Despite the short flight of EUSO-SPB2, we can show that our instruments were operational and prepared to do observations of CRs and neutrinos at high energies. The knowledge and experiences gained during the EUSO-SPB2 flight can be utilized in the planned POEMMA Balloon with Radio mission.
Tobias Heibges (Tue,) studied this question.