The Extreme Universe Space Observatory on a Super Pressure Balloon II Mission (EUSO-SPB2) is a precursor for a next generation space observatory for multi-messenger astrophysics. The EUSO-SPB2 instrument will measure PeV and EeV-scale cosmic rays, optical backgrounds that could mimic tau neutrino interactions in the Earth's limb, and search for optical signatures consistent with the upward-going candidate events that the Antarctic Impulse Transient Antenna (ANITA) reported. The payload, now in the design and fabrication stage, features a pair of optical telescopes that have 1 meter diameter apertures. The Fluorescence Telescope will have sensitivity in the UV to target extensive air showers at EeV energies. The Cherenkov Telescope will have UV/VIS sensitivity to target Cherenkov emission from air showers at PeV energies. The planned launch date is 2022. We discuss the science and mission, and the current status.

The detection of astrophysical neutrinos by IceCube and the potential to constrain source models of ultra-high energy cosmic rays provide the motivation to develop instruments for the observation of neutrinos above 10 7 GeV. Among the different techniques to detect ultra-high energy neutrinos is the Earth-skimming technique. It makes use of the fact that the tau produced in a tau neutrino interaction inside the Earth can emerge from the ground and initiate an upward-going particle shower in the atmosphere. The particle shower and thus the neutrino can be reconstructed by measuring the Cherenkov and radio emission from the shower particles. In this presentation, we discuss our ongoing development of a Cherenkov telescope for the detection of tau neutrinos, which is to be deployed on the Extreme Universe Space Observatory Super Pressure Balloon 2 (EUSO-SPB2) and is a precursor experiment for the proposed Probe of Extreme Multi-Messenger Astrophysics (POEMMA) mission. POEMMA aims at the detection of ultrahigh energy cosmic rays and ultrahigh energy neutrinos from low earth orbit. The 1 m 2 Cherenkov telescope for EUSO-SPB2 will use silicon photomultipliers coupled to a 100 MS/s readout based on the ASIC for General Electronics for TPC's (AGET) switch capacitor ring sampler. We present the optics, results from our studies to qualify the readout concept and the design of the mechanical integration of the photon detectors and the readout into the telescope.