🇸🇪 ESA balloon mission to provide new insights into Earth’s atmosphere

September 4, 2026

On August 26, at 20:34 local time, the Keystone TV BALLET (Terahertz/Visible BALLoon ExperimenT) balloon was launched from Esrange Space Center in northern Sweden. The balloon had a volume of 334,000m3 and reached an altitude of 32,000 meters, where the onboard instruments studied atomic oxygen levels in the upper atmosphere while also testing technology and measurement methods for future ESA missions.

SSC Space has now passed 700 balloon launches from Esrange. The flight time was extended to 22 hours and 16 minutes thanks to active piloting between different wind layers in the atmosphere during its journey over Sweden and Finland. The payload gondola landed safely by parachute in Finland and was recovered within hours after landing.

The upper part of the atmosphere plays an important role in processes that affect climate, space weather, and satellite motion. Yet despite its importance, it remains one of the least explored regions of Earth’s environment.

The goal was to study the amount of atomic oxygen in the upper atmosphere and test the technology and measurement methods that could support the ESA Earth Explorer mission 12 candidate mission Keystone. The results will help mature the concept for a potential future space mission by providing unique insights into the physics and chemistry of Earth’s upper atmosphere.

A key focus for Keystone is atomic oxygen, the dominant gas at these altitudes. Atomic oxygen influences atmospheric chemistry and affects satellites by contributing to drag, which can impact their lifetime in especially lower orbits. Global and long-term measurements of atomic oxygen are still limited. The region is difficult to study directly because it lies too high for aircraft and too low for satellites to make direct measurements.

To address this challenge, Keystone uses a new type of terahertz instrument to measure atomic oxygen and several other important gases from their spectral signature, while scanning different atmospheric layers from the side. The mission combines these observations with infrared and ultraviolet measurements to provide a more complete picture of processes in the upper atmosphere.

The payload consisted of the THz spectrometer OSAS-B provided by the German Aerospace Center (DLR) and the UV/VIS spectrometer OSIRIS-3 provided by the University of Saskatchewan, Canada. Both instruments delivered unique data about the upper atmosphere of the Earth.

Balloon flights of this kind allow researchers to test new technology in a near-space environment at lower cost and with shorter development timelines than a satellite mission. If the concept moves forward, Keystone could become an important step toward improving our understanding of the interaction between Earth’s atmosphere and space.

“Reaching 700 balloon launches from Esrange is a milestone that reflects decades of expertise, teamwork, and trust from the international research community. There are only a handful of places in the world capable of carrying out missions of this scale and complexity, and Esrange is one of the leading ones. As scientific demand for access to the upper atmosphere continues to grow, we are proud to help enable missions that expand knowledge, test new technologies, and pave the way for future space exploration,” says Lennart Poromaa, Head of Esrange Space Center.

More information

For more information on ESA Keystone, visit the ESA website or SSC Space.

Originally published on September 4, 2026 by SSC Space.