Tilt Sensor Temperature Control System for the POEMMA Balloon with Radio Mission

The POEMMA Balloon with Radio (PBR) payload will ascend 33 km above sea level to measure high energy cosmic rays and search for neutrinos. Launch is planned from Wanaka, New Zealand in 2027 for a flight lasting up to 50 days. PBR features a hybrid Fluorescence-Cherenkov telescope and radio detector mounted on a mechanism capable of -90° to 15° tilting relative to horizontal. Accurate event detection and classification rely on tilt angle, particularly for events near Earth's limb. Tilt is measured with an inclinometer operational between -40℃ and 85℃. During the 2023 EUSO-SPB2 flight, the inclinometer acted as a thermometer below -40℃. To prevent this, the PBR incorporates a temperature control system using a thermoelectric cooler (TEC), which is preferable to electrically noisier thermal switches that would interfere with the radio detector. The PBR tilt sensor system also includes a Resistance Temperature Detector (RTD) and resistive heater. The TEC monitors the RTD and maintains a minimum temperature currently set at 10℃. The TEC powers the heater until the target is reached; the heater is then ramped off. This temperature control method will also be implemented in the tilt system control box. We report on the status and testing of these systems.