A faint layer of air high above Earth is becoming an important concern for satellite tracking operators. NASA is now offering up to USD 500,000 to individual winning teams that can develop a practical way to monitor it. The US space agency opened the Orbital Clarity Challenge on August 19, asking researchers and companies to develop instruments that can determine how much drag spacecraft experience in low Earth orbit. Up to four teams can win the top prize, taking the potential total award to USD 2 million.

The focus is the thermosphere, a region that begins about 80 kilometres above Earth and extends hundreds of kilometres into space. The air here is extremely sparse, but spacecraft moving through it still encounter enough resistance to gradually alter their orbits.

That resistance does not remain constant. When the Sun becomes more active, bursts of energy can heat the upper atmosphere. The thermosphere expands, increasing the amount of gas encountered by satellites. The resulting increase in drag can change their altitude and make their future position harder to calculate. For spacecraft operators, even a small difference can matter when several objects are moving through the same orbital region.

A Gap in the Data

NASA already relies on computer models to estimate atmospheric drag. But those calculations depend on how well scientists understand conditions in the upper atmosphere at a particular time and location. The agency wants new technology that can provide more direct information.

Under the competition, proposed instruments should be inexpensive enough to be deployed widely. NASA says they could potentially be carried aboard commercial spacecraft as hosted payloads, allowing measurements to be collected from several points in orbit rather than from a limited number of dedicated missions.

The competition will run through several stages, with NASA aiming to move successful ideas from an initial concept towards an instrument that can eventually be tested in space. Winning teams are also expected to receive an opportunity for an orbital demonstration. Applications for the first stage close in November 2026.

Satellite Tracking: Why this Matters?

The number of spacecraft operating in low Earth orbit has grown rapidly, with satellites supporting communications, navigation, Earth observation and scientific research.

Their paths are affected by several forces, including the thin atmosphere at orbital altitude. During periods of strong solar activity, atmospheric drag can rise sharply and contribute to changes in orbital altitude. Better information about those changes could help operators plan manoeuvres more accurately and improve forecasts of when satellites will descend from orbit.

NASA’s prize is therefore aimed at a relatively small piece of the space infrastructure puzzle: getting a clearer picture of the air that satellites are still moving through, even hundreds of kilometres above the ground.

French astronaut Sophie Adenot has become the first Frenchwoman to perform a spacewalk, spending 6 hours and 23 minutes outside the International Space Station to begin repairs to its exterior communications system.

French astronaut Sophie Adenot made European space history on Tuesday by becoming the first French woman to perform a spacewalk outside the International Space Station. Adenot, 44, stepped outside the orbiting laboratory alongside American astronaut Anil Menon, floating roughly 400 kilometres above the Earth for 6 hours and 23 minutes to begin a repair of the station’s exterior communications equipment.

“I’m out,” Adenot said as she exited the station. “I feel very good now.”

A Repair Job That Ran Long The astronauts’ task was to replace an aging space-to-ground antenna on the station’s Z1 truss — the primary link carrying high-speed data, voice calls and video between the station and mission control in Houston. The antenna had stopped tracking NASA’s data relay satellites since November and had been out of service since, with a second antenna carrying the station’s communications load in the meantime.

Menon and Adenot successfully removed the failed antenna and secured it to the truss structure, but disconnecting its electrical cables and loosening its mounting bolts took longer than planned, leaving no time to install the replacement unit. NASA has scheduled a second spacewalk for Tuesday, August 25, to complete the installation. The station’s communications were not affected by the delay, as the backup antenna continued operating throughout.

Inside the station, astronauts Jack Hathaway and Jessica Meir coordinated the operation from the control desk, operating the station’s robotic arm and monitoring the spacewalkers’ life support systems throughout.

Days of Preparation Before the Hatch Opened Spacewalks demand days of preparation before the airlock ever opens. In the lead-up, Adenot and Menon spent dozens of hours readying their gear inside the station — inspecting safety tethers, organising tools, servicing backup emergency jetpacks, charging suit batteries, checking for pressure leaks, and testing biomedical sensors and radios.

Spacewalk complete. ✅

After 6 hours and 23 minutes outside the International Space Station, @Soph_astro is safely back inside.

With today’s EVA, Sophie becomes the first French woman to perform a spacewalk. 🇫🇷 pic.twitter.com/i3BghrdaRK— European Space Agency (@esa) August 18, 2026

“A successful [spacewalk] starts long before the hatch opens, and that’s where my focus has been these past few days: rehearsing, preparing and focusing,” Adenot said on social media before the excursion.

Suit fitting was a major focus of the preparation: working inside a heavy, pressurised spacesuit for over six hours puts considerable strain on an astronaut’s hands and shoulders, and engineers on the ground worked closely with Adenot to customise her suit and reduce pressure points.

A Milestone for European Space Exploration Adenot brought extensive technical experience to the mission. A trained engineer and former helicopter test pilot, she was selected for astronaut training by the European Space Agency in 2022 and launched to the space station in February 2026, becoming only the second French woman in history to reach space, after physician-astronaut Claudie Haigneré in 1996. With Tuesday’s spacewalk, she also became the second European woman ever to conduct a spacewalk, after Italian astronaut Samantha Cristoforetti in 2022, and the fifth French citizen overall to do so. The last French citizen to walk in space was Thomas Pesquet.

Despite the milestone, Adenot credited the wider team behind the mission. “My deepest gratitude goes to everyone who made this possible — pioneers who came before us, but also the incredible teams working behind the scenes today,” she said after returning inside the station.

A Milky Way merger with a dwarf galaxy about 11.8 billion years ago has been uncovered by astronomers using the Hubble Space Telescope and ESA’s Gaia mission. The discovery provides new evidence about how the Milky Way formed and identifies a distinct population of ancient globular clusters linked to the merger.

Our home galaxy, the Milky Way, contains hundreds of billions of stars today. It grew to this size over billions of years by pulling in smaller neighbouring galaxies and absorbing them. Now, astronomers using the NASA/ESA Hubble Space Telescope and ESA’s Gaia mission have found evidence of a major merger that occurred near the very beginning of the Milky Way’s history.

By combining precise stellar age and chemical-composition measurements from Hubble with motion-mapping data from Gaia, the team pushed back the known timeline of the Milky Way’s formation by roughly 1.8 billion years. The findings, led by Davide Massari of the Astrophysics and Space Science Observatory of Bologna, Italy, were published this week in Nature Astronomy.

Evidence of an Ancient Milky Way Merger

Reconstructing the Milky Way’s earliest history is difficult: in its youth, the galaxy was smaller, more chaotic, and closer in size to the dwarf galaxies it collided with, and many physical traces of those early mergers have since been erased.

To work around this, the researchers studied 39 globular clusters — dense, ancient groupings of up to a few million stars — in the inner 20,000 light-years of the galaxy, where evidence of the earliest mergers is most likely to survive. Using Hubble’s high-resolution imaging, the team measured each cluster’s age and metallicity (its abundance of elements heavier than helium) with what the researchers describe as unprecedented precision.

“Thanks to the high resolution and depth of Hubble imaging, we could measure the age and the metal content of these clusters with unprecedented precision,” said Chiara Zerbinati, a co-author on the study at the University of Bologna, in a release issued by ESA Hubble. “Coupled with measurements from Gaia, this made it possible to distinguish a population of globular clusters that are different from the others.”

Identifying LKH

Cross-referencing Hubble’s age and metallicity data with Gaia’s motion measurements, the researchers identified a distinct third population of globular clusters — older than the ones known to have arrived during the Milky Way’s collision with the Gaia-Sausage-Enceladus dwarf galaxy about 10 billion years ago, but younger than the stars that formed within the Milky Way itself.

That pattern pointed to a separate, earlier merger: the absorption of a dwarf galaxy roughly 11.8 billion years ago — about two billion years after the Big Bang — carrying a total stellar mass of around 500 million times the mass of the Sun, a significant share of the Milky Way’s total mass at the time.

The researchers named the dwarf galaxy Low-energy-Kraken-Heracles, or LKH, after three earlier papers that had proposed the idea of an early merger in the Milky Way’s history.

“Our home is the Milky Way galaxy, but we do not know how our house was built,” Massari said. “In this paper we discover where the first significant batch of bricks came from: a dwarf galaxy that we call LKH.”

Rewriting Early Galactic History

The finding challenges an earlier assumption that the Milky Way’s oldest stellar populations formed almost entirely in place, showing instead that external galaxies contributed to its structure far earlier than previously established.

The team plans to extend the analysis to additional globular clusters across the galaxy, aiming to build a more complete map of the mergers that shaped the Milky Way over cosmic history.