FLOCK 4BE-19

The Arctic Weather Satellite (AWS) is an Earth-observation technology demonstrator operating in low Earth orbit under the management of the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT). Cataloged by the United States Space Force under NORAD ID 60563 and carrying the international designator 2024-149CZ, the satellite was launched on August 15, 2024, and remains operational in orbit. Although tracked under the alternate name FLOCK 4BE-19 in the satellite catalog, the spacecraft is universally identified within the meteorological community by its program designation: Arctic Weather Satellite. It is a compact, purpose-built platform intended to advance the state of atmospheric sounding technology in polar and sub-polar regions, with direct relevance to future operational weather satellite systems in Europe.

Mission and Purpose

The Arctic Weather Satellite was conceived as a proof-of-concept mission to test and validate microwave sounding technology in an orbit that provides consistent coverage of high-latitude and polar regions—areas notoriously underserved by conventional geostationary weather platforms. Geostationary satellites, parked at fixed positions over the equator, view the poles at extreme angles, severely degrading the quality of data retrieved from those regions. Improving the accuracy of numerical weather prediction over the Arctic and sub-Arctic has long been a priority for European meteorological agencies, since weather systems originating in those regions frequently propagate southward and affect populated areas across Europe and beyond.

To address this gap, ESA and EUMETSAT jointly directed the development of AWS as a pathfinder mission, with the goal of demonstrating whether a relatively small, cost-efficient spacecraft could carry a microwave radiometer capable of sounding atmospheric temperature and humidity profiles with sufficient accuracy to be of operational value. If successful, the data and engineering lessons from this demonstrator are intended to inform the design and deployment of the EPS-Sterna constellation—a planned network of satellites that would provide far more frequent revisit times over polar regions than any single platform could achieve alone. AWS thus represents not an operational mission in its own right, but a deliberate step in a longer program of capability development.

The satellite is registered with an owner country of the United States in the catalog, a reflection of the administrative and launch logistics involved rather than the nationality of the program itself, which is fundamentally European in character. The operator of record is EUMETSAT, the intergovernmental organization headquartered in Darmstadt, Germany, responsible for European weather satellite operations.

Orbit and Tracking

AWS occupies a sun-synchronous orbit (SSO), a particular class of near-polar orbit in which the orbital plane precesses at a rate that keeps it at a nearly constant angle relative to the Sun throughout the year. This geometry ensures that the satellite passes over any given location at approximately the same local solar time on every orbit, providing consistent illumination conditions for sensors and predictable data collection schedules. Sun-synchronous orbits are the standard choice for Earth-observation and meteorological satellites requiring global, repeatable coverage.

The satellite's current orbital parameters place its apogee at 440 km and its perigee at 436 km, indicating an almost perfectly circular orbit with minimal eccentricity. This tight altitude band is entirely consistent with a mission designed for sustained low-Earth-orbit operations: low enough to maximize instrument sensitivity and spatial resolution, while remaining above the most significant atmospheric drag effects that would cause rapid orbital decay. The orbital inclination is 97.4°, which is the retrograde tilt characteristic of sun-synchronous trajectories. At this inclination, AWS passes over the poles on every orbit, ensuring that the high-latitude regions central to its scientific objectives receive regular observational coverage.

The orbital period is 93.2 minutes, meaning the satellite completes roughly 15 to 16 full orbits around Earth each day. Over the course of these daily passes, its ground track shifts progressively westward relative to Earth's rotating surface, eventually building up global coverage over a span of days. For a microwave sounder focused on atmospheric profiling, this pattern of coverage is well suited to feeding data into numerical weather prediction models, which assimilate observations from multiple sources on regular time cycles.

The satellite launched from Vandenberg Space Force Base in California, which is the primary US West Coast launch facility used for polar and sun-synchronous payloads, as its geographic position allows rockets to fly southward over open ocean into high-inclination orbits without overflying populated areas.

Design and Operators

AWS was constructed by a consortium led by OHB Sweden, a satellite manufacturing subsidiary of the German space group OHB SE. OHB Sweden has particular expertise in small satellite platforms and has been involved in a range of scientific and Earth-observation missions. The consortium approach brought together relevant European industrial expertise under a single program structure directed by ESA, with EUMETSAT providing the operational and scientific requirements that would guide the mission's design.

The satellite has a mass of 125 kg, placing it firmly in the category of small satellites—large enough to house a meaningful scientific payload but small enough to be launched as part of a rideshare or on a relatively modest launch vehicle. This mass class reflects a broader trend in Earth observation toward smaller, more affordable spacecraft that can be built and launched more quickly than traditional large platforms, enabling faster iteration and technology validation.

The manufacturer listed in catalog records is Thales Alenia Space, one of Europe's largest and most experienced satellite manufacturers, which may reflect the supply of key payload hardware or subsystems within the broader industrial consortium. The integration of contributions from both OHB Sweden and Thales Alenia Space illustrates the collaborative industrial model common to ESA-directed programs, in which prime contractors and major subcontractors are often distributed across multiple European member states.

The spacecraft carries a microwave radiometer as its primary instrument, designed to measure natural thermal emissions from oxygen and water vapor molecules in the atmosphere at multiple frequencies. By analyzing the intensity of these emissions at different spectral channels, it is possible to retrieve vertical profiles of atmospheric temperature and humidity—data of central importance to weather forecasting. The instrument is optimized for the viewing geometry and orbital parameters of a low-altitude polar orbit, where the combination of high inclination and low altitude allows fine spatial resolution over the Arctic.

Significance and Current Status

The Arctic Weather Satellite occupies a strategically important position in the roadmap for European meteorological satellite capability. The EPS-Sterna constellation it is designed to precede represents a significant investment by EUMETSAT and ESA in next-generation polar weather observation. Where current polar-orbiting meteorological satellites—such as those in the EUMETSAT Polar System (EPS) series—rely on single platforms making relatively infrequent passes, a constellation of smaller satellites could dramatically increase the frequency with which polar atmospheric profiles are collected. More frequent observations translate directly into better initialization of weather forecast models, which is particularly valuable for short-range and medium-range prediction.

By flying AWS as a demonstrator before committing to full constellation procurement, ESA and EUMETSAT are following an approach increasingly common in both commercial and institutional space programs: use a low-cost, lower-risk precursor to validate technology, refine requirements, and reduce uncertainty before scaling up. Should AWS demonstrate the performance needed, it will provide an empirical basis for the instrument and platform designs that will underpin EPS-Sterna. Should it reveal limitations or unexpected challenges, those findings can be incorporated into subsequent designs at relatively low cost.

As of the time of writing, AWS remains in orbit, having completed its ascent to the intended circular orbit at approximately 437–440 km altitude. Mission status details beyond orbital presence are not publicly recorded in the satellite catalog, and EUMETSAT has not yet announced formal mission completion. The satellite was launched in August 2024 and continues to be tracked by the US Space Surveillance Network under its NORAD catalog entry.

How to Spot It

At an altitude of approximately 437–440 km and with a mass of only 125 kg, the Arctic Weather Satellite is a small and relatively dim object in the night sky, and it is not generally considered a prominent naked-eye target. However, under favorable conditions—when the satellite is sunlit and the ground observer is in twilight—it may be detectable with binoculars or a small telescope as a fast-moving point of light crossing the sky.

Its 93.2-minute orbital period and 97.4° inclination mean it passes over virtually every point on Earth's surface at least once per day, and observers at high latitudes in particular may find that it transits nearly overhead during favorable passes. Dedicated satellite-tracking tools can generate precise pass predictions for any location using the orbital elements derived from its NORAD ID 60563. Passes occurring within an hour of local sunrise or sunset offer the best visibility, as the satellite will be illuminated by sunlight while the ground below remains dark enough to see it against the background sky.