How the SATELLITE DRAG figure on our residence leaf is made, and what it's telling us. Sept. 2026.
Starlink has many downsides. The megaconstellation interferes alongside astronomy, pollutes the ambiance alongside metal re-entry debris, and has pushed Low Earth Orbit to the brink of the Kessler Syndrome.
On the another hand, it makes a terrific barometer.
Earth is entirely surrounded by Starlink satellites. More than 11,000 of them are circling our earth correct now. Without exception, they all skim the outermost layers of our atmosphere, and so they cognition aerodynamic drag. Drag pulls them down, and they have to combat rear alongside thrusters. This makes them ad hoc detectors of air pressure. Every day, we peruse those detectors and abscess the outcome downward to one number: the descend rate.
What the figure means
The descend charge is the answer to a uncomplicated question. If a representative Starlink at 480 km switched off its thrusters today, how many meters of altitude would it endure in a day? A value of, say, 30 m/day method it would descend 30 meters. Why 480 km? Because that's anywhere most Starlinks are.
The figure changes all day in reply to sun-related activity. In 2026 it has ranged from 19.7 m/day on Aug. 10th, the quietest air of the year, to 127.6 m/day on Jan. 20th, during the year's biggest geomagnetic storm. That's a aspect of six. The satellites didn't change; the air did.
Here's a way to awareness the numbers. At 40 m/day, a deceased moon at 480 km would obtain approximately four years to autumn out of orbit. At the January storm charge it would arrive downward in a small complete one year. These are paces, not forecasts, since the air never stays the identical for a year. But they display why area climate matters to anyone who owns a satellite.
Strictly speaking, drag measures the density of the air, not its pressure. We call it a barometer anyway. When the high ambiance heats up, force and density increase together, and "densitometer" is not a term anyone wants to read.
2026 so far
The twelvemonth opened alongside a bang. On Jan. 19-21 a G4 geomagnetic storm (Kp 9-, Ap 144 on the 20th) heated the thermosphere and the descend charge jumped to 127.6 m/day, concerning five times the quiet-day floor. It took two weeks for the air to resolve down. Smaller storms in March (G3 on the 22nd), April, May, June and July (G3 on the 4th) all produced a keen spike. Storms weaker than concerning Ap 45 are buried in the background.
Then came summer. As Solar Cycle 25 continued its decline, the air thinned to the year's minimum on Aug. 10th. Starlinks were sinking lone 19.7 meters a day.
Look closely at the orange bands. Each one marks a extend of days whenever the Starlink fleet's median altitude sagged by additional than 8 m/day or rebounded by additional than 10 m/day. That's SpaceX fighting back. There were eight specified episodes in 2026, and all one of them sits on or fair following a spike in Ap. We didn't nourish the storm calendar into the software. The maneuvers established it on their own.
How we do it
Monitoring is easy, since person alternatively does the difficult part. Using radar, the US Space Force's 18th Space Defense Squadron tracks all entity in orbit and, two or three times a day, publishes caller orbital elements (also known as "TLEs") for all one. They are distributed through Space-Track and CelesTrak.
Buried in all TLE is a drag term, called B* ("B-star"). Here's the trick: the orbit example that says a TLE assumes a fixed atmosphere. When the genuine ambiance swells, the moon slows downward additional than the example expects, and the fitted B* has to develop to keep the orbit matching the tracking. B* is anywhere the air density ends up.
Any one satellite's B* is noisy. The fits are blurred complete one to three days, and station-keeping burns corrupt them. So we never rely a sole satellite. We prosecute a fixed example of 1,000 Starlinks launched before 2026, and for all one we difference today's B* to that satellite's own quiet-air floor. Then we obtain the median throughout the entire cohort. The median of hundreds of satellites is the instrument. The noise of any one of them falls away.
That gives a ratio: how many times denser the air is today than on a quiescent day. One calibration changeless turns it into meters per day, and the Planet Labs Doves supplied it. In a quiescent week of May 2026 their measured fall, scaled to 480 km, fixed the value at 35.7 m/day per component of the index. Then came the check. During the January storm week, the Doves' genuine decay rosy 2.74-fold and the Starlink indicator rosy 2.71-fold. Two autonomous methods accepted to one percent.
Every dawn we fetch the newest TLEs, compute the day's value, and article it in the SATELLITE DRAG box on the residence page. TLEs are typically a day old, so the figure describes yesterday's air.
The three checks
Starlinks aren't the lone ones we're tracking. We detect three another autonomous constellations: Planet Labs' SuperDoves (107), Amazon's Kuiper satellites (391), and Eutelsat's OneWeb satellites (651). Each one answers a distinct question.
The SuperDoves, orbiting at 400-500 km, have no thrusters at all. They cannot combat the atmosphere, so they really do sink. Their measured decline is our dirt truth. In 2026 a representative Dove has been losing concerning 62 meters a day; between Jan. 1st and delayed August, the median Dove cut 15.5 km. They are exquisitely sensitive.
Amazon's Kuiper satellites, at concerning 630 km, pertain to a distinct company. Their maneuvers have nothing to do alongside SpaceX's. Anything the two fleets do in unison is the atmosphere, and they do a lot in unison: day to day, Kuiper and Starlink concur alongside a association of 0.94.
OneWeb orbits at 1,200 km, anywhere the air is so lean that sunlight force matters additional than drag. They are our null control, flat all year. Yet equal OneWeb twitched during the January storm, rising 1.3-fold. The exosphere felt it too.
The ambiance breathes
Using this new data stream, we can observe the ambiance breathe. The letter cover of air about our earth expands and contracts in reply to sun-related activity. Solar ultraviolet heats the thermosphere, and the descend charge tracks the sun's 10.7 cm broadcast flux alongside a two-day lag: the high ambiance takes concerning two days to answer a alter in the sun. Big geomagnetic storms puff up the ambiance faster than that and logic keen spikes in the descend rate.
Because our satellites fly at six distinct heights, we can observe the puff happen tier by layer. For the January storm, current is how much the drag rosy at all altitude (storm days compared to the five quiescent days before):
| Altitude | Constellation | Storm / quiet |
|---|---|---|
| 350 km | Starlink, low shell | 1.5× |
| 480 km | Starlink, chief shell | 2.1× |
| 555 km | Starlink, elevated shell | 3.0× |
| 630 km | Amazon Kuiper | 2.0× |
| 1,200 km | OneWeb | 1.3× |
The reply climbs alongside altitude to concerning 550 km, afterward turns complete and is nearly gone by 1,200 km. Heated oxygen expands upward until it thins out into the exosphere. Textbooks foretell the climb. The turnover is the benevolent of item you lone see alongside sensors at six heights.
Why it matters
The density of the thermosphere is the largest doubt in orbit prediction and collision avoidance. The norm ambiance models err by 20-30% on average days and by much additional during storms. A measured regular figure can calibrate them, day by day.
Research groups have used Starlink orbits before, most famously to dissect the February 2022 storm that killed 38 newly launched Starlinks at their 210 km insertion altitude. What's new current is a running, public, regular indicator alongside three autonomous constellations checking the answer. It's the kind of item nobody publishes daily. Now person does.
No device was launched for this. The swarm itself is the sensor, peruse from community tracking data.
Caveats
The indicator is relative. It measures air density as a multiple of all satellite's quiescent floor, converted to meters per day alongside one calibration constant. Absolute density motionless needs a model.
TLE fits blur complete one to three days, so keen events lag and smear a little.
SpaceX turns its satellites edge-on during storms to cut drag. Storm peaks peruse from Starlink are hence lesser bounds. The Doves, which cannot duck, are the check.
The measured document began Jan. 1, 2026. Scaling by sun-related flux, we evaluation that solar-minimum air would provision approximately 13 m/day, and quiescent days at the 2024 sun-related maximum approximately 150. Those are estimates, not measurements.
Data
Daily sequence for 2026: drag_sink_2026.csv (date, meters per day). Full-size chart: effective_sink_2026.png.
Orbits: Space-Track.org (18th Space Defense Squadron) and CelesTrak (T.S. Kelso). Satellites: SpaceX Starlink, Planet Labs, Amazon Kuiper, Eutelsat OneWeb. Ap and F10.7: GFZ Potsdam and DRAO Penticton via CelesTrak. Thermosphere Climate Index: Martin Mlynczak, NASA Langley. Method and analysis: Tony Phillips, Spaceweather.com, Sept. 2026.
