Test Assembly for Thermal Vacuum Test of the POEMMA-Balloon with Radio Telescope Tilt System

The NASA-sponsored POEMMA-Balloon with Radio (PBR) mission will detect high energy cosmic rays in search for high energy neutrinos. The payload features a fluorescence/Cherenkov telescope and a radio detector. The PBR telescope can be tilted from nadir to 15 degrees above horizontal. The mission will fly for as long as 50 days at an altitude of 33 km with temperatures as low as -60 °C. During operation, the telescope’s axles and bearings will experience a gravitational force of up to 2000 lb, and the tilting system must deliver a torque up to 3000 in-lb about its rotational axis. Tests are required to accurately simulate the weight and torque of the telescope on the flight tilt system. To do this, a custom test stand was designed and fabricated to test the flight tilt system in the large thermal vacuum chamber at NASA’s Columbia Scientific Balloon Facility. The telescope weight is simulated by using turnbuckles to pull on a beam system attached to a test axle and is measured with a low temperature dynamometer scale. A weighted frame is attached to the axle to simulate torque. Additional mounting locations are provided for the tilting sensors, shutter actuators, and system control box. We present the design and status of the laboratory tests and thermal vacuum tests.