Development of a Simultaneous Flashing System for Testing the Proposed Radio-Cherenkov Cross-Trigger Onboard PBR

The Probe Of Extreme Multi-Messenger Astrophysics (POEMMA) is a planned satellite mission with the goal of observing cosmic rays and neutrinos at the highest energies by detecting extensive air showers (EAS) produced in the Earth’s atmosphere using both a UV fluorescence camera (FC) and an optical Cherenkov camera (CC). POEMMA Balloon with Radio (PBR) is a pathfinder experiment for POEMMA that seeks to address similar science goals but is designed as a payload for a NASA super-pressure balloon and optimized for stratospheric observation of EAS. In addition to the FC and CC, PBR features a radio instrument (RI) for detecting the signature of EAS in the 50 – 550 MHz band. As a result of small signal amplitudes relative to the thermal background, a standalone RI would face a high energy threshold compared  with the FC and CC. By using the CC to trigger the RI, information can be collected that may be useful for addressing these issues in next generation RI. A calibration system capable of generating collimated nanosecond-scale optical light pulses at 1 Hz is being developed to test this cross-trigger configuration. By synchronizing the “Cherenkov flasher” with a radio pulsing system, we aim to produce simultaneous optical and radio signals to investigate the timing and sensitivity requirements of a cross-trigger implementation on PBR. Here, we present the design and preliminary results of the Cherenkov flasher system and discuss the planned cross-trigger tests using the combined CC and radio pulsers.