In a spotlessly clean room, engineers at Redwire's facilities in Belgium have completed the assembly of a key part of the European Space Agency's (ESA) ALTIUS ozone mission. With this, the crucially important satellite platform is now fully formed and ready to receive its measurement instrument, marking a key milestone in the project aimed at detailed monitoring of the recovery of Earth's protective atmospheric shield. This step moves the mission from the development phase to the verification and integration phase, where experts will begin connecting and rigorously testing all onboard systems as a single cohesive unit.

ALTIUS, which stands for "Atmospheric Limb Tracker for Investigation of the Upcoming Stratosphere," is a next-generation Earth observation satellite specifically designed to monitor the concentration of ozone and other trace gases in the atmosphere. Its mission is of vital importance for understanding the complex processes that affect our climate and protecting life on Earth.

The importance of monitoring the planet's shield

The story of the importance of monitoring atmospheric ozone dates back to the 1970s, when scientists discovered an alarming thinning of the ozone layer, especially over the South Pole, resulting in the phenomenon known as the "ozone hole." Atmospheric ozone, located in the stratosphere at an altitude of 15 to 30 kilometers, acts as Earth's natural filter for solar radiation, absorbing most of the ultraviolet radiation, especially the harmful UV-B rays. Exposure to excessive amounts of UV-B radiation is directly linked to an increased risk of skin cancer and cataracts in humans, but it also causes significant damage to plants, marine ecosystems, and the entire animal world.

Thanks to a global response and the implementation of the Montreal Protocol of 1987, tremendous progress has been made. This international treaty, ratified by all countries in the world, successfully restricted the use of ozone-depleting chemicals, such as chlorofluorocarbons (CFCs) that were widely used in refrigerators and aerosols. Scientific assessments confirm that this atmospheric shield is on the path to recovery. It is predicted that the ozone layer over Antarctica will return to 1980 levels by around 2066, while recovery in other areas is expected even earlier. Despite positive trends, continuous and precise monitoring is crucial to confirm the recovery and understand all the chemical and dynamic processes involved. In addition, ozone affects the temperature of the stratosphere and plays a role in heat absorption, which directly impacts global circulation patterns. Therefore, precise ozone data improves climate prediction models.

Innovative observation technique

Unlike many other satellite missions that measure ozone by looking straight down (nadir observation), ALTIUS is designed to perform "limb sounding." This sophisticated technique involves scanning the Earth's atmosphere along the horizon, or the "limb" of the planet. Such an approach allows for the observation of ozone at different altitudes simultaneously, thereby obtaining detailed vertical profiles of gas concentrations with a very high resolution of about one kilometer. This provides scientists with a three-dimensional picture of the distribution of ozone and other compounds.

The heart of the mission, a versatile spectral imager, uses three independent spectral channels operating in the ultraviolet, visible, and near-infrared spectrum. This combination allows for the detection of a wide range of gases, including nitrogen dioxide (NO2), water vapor (H2O), methane (CH4), and aerosols. The mission will achieve global coverage in a cycle of just three days, providing regular and comprehensive data to the scientific community.

The technical backbone of the mission

The satellite platform, whose assembly is now complete at Redwire's facilities, represents the technical backbone of the entire satellite. It is responsible for all the key functions that enable the scientific instrument to operate in orbit. This includes power supply via solar panels and its management, precise thermal control that protects sensitive equipment from extreme temperatures in space, navigation, pointing, and orbit control. The platform also ensures communication with Earth and overall system and data management. Although ALTIUS is a relatively small satellite, with a height of 1.3 meters, a solar panel span of 4.5 meters, and a mass of less than 300 kilograms, its development requires exceptional precision, collaboration, and a high level of engineering skill. Michael Francois, the ALTIUS project manager at ESA, pointed out that the completion of the platform is an important milestone that is the result of the dedicated work and technical expertise of the team at Redwire.

International cooperation and future steps

While the platform is ready, work is underway at the facilities of OIP Sensor Systems, also in Belgium, on the assembly of the very heart of the mission: the versatile spectral imager. The first parts taking shape are the optical benches – high-precision components crucial for capturing atmospheric data. The development of the ALTIUS mission is taking place within ESA's Earth Watch program and is primarily funded by Belgium, with support from Canada, Luxembourg, and Romania. This international cooperation reflects the global importance of the mission, whose scientific concept was originally proposed by the Belgian Institute for Space Aeronomy (BIRA-IASB).

Given that the platform is assembled and testing is about to begin, the ALTIUS mission team is on track for a launch scheduled for late 2027 from the space center in Kourou, French Guiana. If all goes according to plan, this new satellite guardian will soon be orbiting the Earth, with its eyes firmly fixed on the fragile veil of gases that protects all life below.