The Stellar Occultation Hypertemporal Imaging Payload: A Year Aboard the International Space Station

From its vantage point on the aft side of the International Space Station (ISS), for just over a year the Stellar Occultation Hypertemporal Imaging Payload (SOHIP) monitored the light from bright stars traveling through Earth's atmosphere. Using two optical telescopes, SOHIP's mission was to measure the scintillation and refractive bending of this starlight to detect and characterize upper atmospheric perturbations down to length scales of 10 meters. SOHIP measurements of atmospheric properties such as temperature, pressure, air-density, and refractivity profiles at altitudes up to 50 kilometers can provide estimates of atmospheric gravity waves and turbulence in the stratosphere. Designed and built by Lawrence Livermore National Laboratory's (LLNL's) Space Science and Security Program (SSSP), the SOHIP prototype featured LLNL-patented low-cost monolithic-optics technology, a computationally powerful Payload Electronics Module (PEM) built around the Nvidia TX2i, and a custom two-axis gimbal for attitude control. The SOHIP mission was highly successful, resulting in nearly 500 occultations imaged at frame rates over 1,000 frames per second, along with a year's worth of valuable telemetry demonstrating the resilience and reliability of the payload processing system. This paper presents an overview of the SOHIP instrument and its operation, some of the challenges it encountered, and an initial look at the data that it collected during the mission lifetime.