Loon: A Balloon-Based Platform for Scientific Experiments in the Lower Stratosphere

Loon LLC, a subsidiary of Alphabet, operates a fleet of balloons at the edge of space. Typically flying at 15 to 21 kilometers altitude, these superpressure helium balloons carry a communications payload designed to connect people around the world where deploying traditional terrestrial mobile networks is difficult due to challenging and inaccessible terrain. The balloons typically fly for 3 to 4 months, with some flights as long as 190 days. Loon software autonomously navigates the balloons to target service areas around the world by changing the balloon’s altitude and thus leveraging the winds that blow in different directions at different altitudes in the stratosphere. Both the platform and the communications payload are powered by solar energy, with solar panels generating power during the day and batteries providing power at night. Balloons are manufactured at scale and launched from Loon’s custom launch sites with the capability to launch a balloon every 30 minutes. To date, Loon balloons have travelled over 27 million kilometers in the stratosphere. Given their ability to carry a payload and navigate on long duration missions, the Loon balloons are more akin to atmospheric satellites than traditional weather or other types of balloons.

In addition to communications services, the Loon platform is well suited to a variety of scientific missions that could leverage Loon’s long-duration balloon-based stratospheric flights. Loon already carries a suite of sensors for improving Loon’s understanding of the stratosphere and the balloon vehicle’s operational performance. These sensors include measurements of temperature, pressure, upwelling infrared radiation, and wind velocity (derived from GPS position data). Loon has developed a repository of such data from prior balloon flights stretching back several years and continues to collect this data in on new flights. The data is relayed back in real time, using a satellite connection when balloons are outside the range of other communication means.

Furthermore, the Loon platform is capable of carrying additional payloads that may benefit from a balloon-based flight. Such payloads include scientific, earth, and space observation missions, as well as payloads targeting future space missions that are looking to increase their technology readiness level via a balloon flight. For small payloads, the Loon platform can accommodate such payloads as a secondary rideshare mission. Larger payloads would require a dedicated flight in lieu of the primary communications mission. In all cases, the payload can leverage Loon’s solar and battery power system, telemetry and command data handling system, as well as the ability to dowlink mission data through high speed backhaul links.

In this paper, we provide a description of Loon’s existing sensor suite, an overview of prior scientific work leveraging Loon sensor data, and high-level specifications of Loon’s hosted payload capabilities.