Thirty years is a long time to wait for a picture. In 1996, scientists using Germany's ROSAT space telescope noticed something unexpected while observing a comet: Earth itself was glowing. The source was the solar wind, a stream of charged particles from the Sun, exchanging charges with atoms in Earth's magnetosphere and releasing faint X-rays in the process. The discovery was real. The instrument to image it took three decades to build.
That instrument is SMILE — the Solar Wind Magnetosphere Ionosphere Link Explorer — and it launched April 9 on a Vega-C rocket from Kourou, French Guiana at 06:29 UTC, according to Wikipedia. The European Space Agency and China's Chinese Academy of Sciences jointly developed the spacecraft. This is the first mission in which ESA and CAS selected, designed, built, launched, and operate a space science mission together, ESA reported. Double Star, launched 2003-2004, was the first ESA-CAS joint project but placed ESA experiments on Chinese satellites rather than a fully shared mission. ESA Director of Science Prof. Carole Mundell approved the mission for launch after it passed its qualification review in November 2025.
The core instrument is the Soft X-ray Imager, which uses lobster-eye optics — a design inspired by the way a lobster's compound eye funnels light through square tubes onto detectors. The University of Leicester led development of the telescope optics using this micropore technology. The optics are genuinely novel: standard X-ray telescopes use grazing-incidence mirrors that can only focus at narrow angles. Lobster-eye optics can capture a wider field of view, which matters when your target is a dynamic boundary region extending hundreds of thousands of kilometers from Earth.
SMILE will orbit from 5,000 kilometers at its closest approach to 121,182 kilometers at apogee — far enough out to observe the magnetosphere's nose, the boundary where the solar wind first hits Earth's magnetic field, per Wikipedia. The spacecraft weighs 2,250 kilograms at launch. Unlike conventional Earth-observation satellites, SMILE won't downlink continuously; it will store data during each orbit and download during the close pass, sustaining observations for up to 40 hours per orbit.
The science is solar wind charge exchange imaging — essentially, taking an X-ray photo of the invisible boundary that shields Earth's atmosphere from the Sun's particle stream. The magnetosphere does this job constantly, but its shape and response change with solar activity. During intense solar storms, the boundary can compress dramatically, exposing low-orbit satellites to direct particle bombardment. Understanding that response has practical stakes: the satellites that modern infrastructure depends on fly through that boundary zone.
This is also a geopolitical mission in a narrow technical sense. ESA and CAS have collaborated before, but never on a mission where both sides had equal design authority and shared operations end-to-end. The ESA-CAS joint statement frames it as a model for future cooperation. Whether that model replicates elsewhere is a different question — scientific collaboration between Europe and China operates in a different register than it did in 2003.
The first images won't arrive immediately after launch; the spacecraft needs time to reach operational orbit and calibrate instruments. What SMILE images on first light is an open question. The 1996 discovery that launched this mission was, as ESA's own account notes, made somewhat by accident. Thirty years of planning is no guarantee the instrument behaves exactly as modeled. The optics are novel. The orbit is demanding. The physics is better understood than it was in 1996, but better understood and completely understood are different things.
What happens if SMILE sees something the models do not predict? That is the actual reason to watch this mission. The glow was a surprise in 1996. The next surprise — whatever form it takes — is what the instrument was built to find.
