An international team led by Dr. Maya Patel at the Royal Observatory in Edinburgh has begun tracking the gradual descent of SpaceX’s Starlink satellites to measure subtle shifts in Earth’s upper atmosphere. The project, launched in early 2025, monitors how the drag on these satellites changes as the thermosphere expands and contracts with seasonal and solar variations.
By analysing precise orbital decay data from more than 400 operational satellites, the researchers can infer density changes at altitudes between 340 and 550 kilometers. The method relies on high‑resolution laser ranging and radar observations from ground stations across Europe, North America, and Australia. „Every time a satellite slows down, it tells us something about the air it’s moving through,” Patel explained. The approach offers a continuous, global barometer that complements traditional satellite drag models, which often rely on sparse data from occasional rocket launches.
The team’s calculations show that during the recent solar minimum, the thermosphere cooled and contracted, increasing drag on the satellites by up to 12 percent compared with the previous solar maximum. This heightened drag caused several older Starlink units to re‑enter the atmosphere earlier than expected, some within weeks of their scheduled de‑orbit. The researchers cross‑checked these findings with data from the International Space Station’s onboard accelerometers, confirming a consistent pattern of density fluctuations.
Patel’s group also discovered regional variations linked to geomagnetic storms. „When a storm hits, we see a spike in atmospheric density that can shave off a few meters from a satellite’s orbit in a single day,” she noted. Such rapid changes were previously difficult to capture, but the dense network of tracking stations now provides near‑real‑time updates. The results are already being used to refine re‑entry predictions for defunct spacecraft, improving safety for both ground populations and operational assets in orbit.
Critics have questioned whether commercial constellations are suitable for scientific monitoring, citing concerns over orbital debris and data continuity. Patel argues that the sheer number of satellites—over 4,000 in the constellation—offers statistical robustness that older, single‑purpose missions lack. „Even if a few satellites fail or are de‑commissioned, the overall dataset remains strong enough to detect long‑term trends,” she said.
The study also highlights the potential for collaboration between private operators and the scientific community. SpaceX has begun sharing telemetry data with the research team, allowing for more precise drag coefficient calculations. This partnership could pave the way for future „science‑as‑a‑service” models, where commercial space assets double as environmental sensors.
The ability to monitor the upper atmosphere continuously has far‑reaching implications. Accurate density profiles help improve satellite navigation, extend the lifespan of low‑Earth‑orbit missions, and enhance predictions of space weather impacts on communications and power grids. As solar activity is expected to rise in the coming years, the planetary barometer built from sinking Starlink satellites could become a vital tool for anticipating atmospheric changes that affect both technology and climate models.
How does satellite drag reveal atmospheric density? When a satellite travels through the thin upper atmosphere, it experiences drag that slows its orbit. By measuring the rate of orbital decay, scientists can calculate the surrounding air density at that altitude.
Why focus on Starlink satellites instead of dedicated scientific probes? Starlink’s large, continuously replenished fleet provides a dense, global sample that is far cheaper and more frequent than launching dedicated atmospheric probes.
What are the risks of using commercial satellites for scientific data? Potential risks include data gaps if satellites are de‑commissioned and concerns about space debris. However, the sheer number of units and growing cooperation with operators mitigate these issues.