Two new sentinels are heading to orbit. The European Space Agency has formally selected Hibidis and SOVA-S, a pair of Scout-class Earth observation missions designed to answer urgent questions about our changing planet—one peering deep into forest canopies to track biodiversity, the other watching invisible waves ripple through the atmosphere to improve weather forecasts.
The selection came after a rigorous 10-month review process by ESA's Earth Observation Program Board. These Scout missions represent a different philosophy in space science: fast, focused, and lean. With a budget cap of 35 million euros each and a mandate to launch within three years of selection, they embody the principle that groundbreaking Earth science doesn't always demand massive budgets or decades-long development cycles.
Hibidis, the Hyper-spectral Biodiversity Scout, will tackle a critical blind spot in our understanding of forest health. Using multi-angle imaging, it will examine the understory spectrum—the light reflected by plants deep within jungles and forests—to assess ecosystem and biodiversity health across regions where ground-based monitoring remains difficult or impossible. The mission is being built by Italy's SITAEL as the primary contractor, working alongside sub-partners Amos and Vito in Belgium and the University of Zurich. It will fly on SITAEL's new Empyreum small satellite platform, powered by SPARK, a low-cost electric propulsion unit designed to keep costs down and innovation high.
SOVA-S—the Satellite Observation of Waves in the Atmosphere—tackles a phenomenon that looks deceptively simple but carries enormous scientific weight. Using shortwave infrared imaging, it will routinely monitor gravity waves, the atmospheric ripples that often appear as moving rows of clouds across the sky. These waves are frequently mistaken for other phenomena, but they are distinct from gravitational waves, the astrophysical events created by colliding pulsars and black holes. What makes atmospheric gravity waves scientifically crucial is their role as energy transporters: they carry vast amounts of energy from lower altitudes to higher ones. By observing and recording these waves, SOVA-S will help scientists refine weather models and improve forecast accuracy.
Both missions will likely launch together on a rideshare flight from Vandenberg Space Force Base in California, heading into sun-synchronous orbit—a high-inclination polar path that passes over the same ground locations at consistent times and lighting angles, ideal for systematic Earth observation. This orbit type has long been favored for reconnaissance satellites, but increasingly it's becoming the standard for scientific missions seeking reliable, repeatable observations.
Hibidis and SOVA-S join a growing constellation of ESA Scout missions. HydroGNSS, the first Scout-class mission, launched in November on a Falcon 9 rideshare. Others in development include NanoMagSat, which will study space weather interactions, and Tango, monitoring industrial emissions. Four missions were under consideration; SIRIUS and NAIAD did not advance in this selection round.
As Simonetta Cheli, ESA's Earth Observation Program director, noted in a recent statement, these lean missions prove that speed and creativity can accelerate discovery. In an era when understanding environmental change has become urgent, Scout missions offer a pathway to answers—fast, affordable, and targeted. In the coming years, as Hibidis and SOVA-S take to space, they'll help us see what has long remained hidden.