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Episode 13

Can a Rocket Launch Throw Off Your Phone's GPS?

Artemis II tore a hole over 4,000 km long in the ionosphere, the charged layer GPS signals cross. Here is how that can put your phone's blue dot metres off.

6 November 20266 min readVideo 8:08

A moon rocket can throw off GPS because every GPS signal is slowed as it crosses the ionosphere, a layer of charged air, and a single-frequency receiver corrects for that with a rough model of an ordinary day. Rocket exhaust wipes out the layer's charge across thousands of kilometres, so the correction is wrong by up to several metres until the sky refills. A storm on the Sun does the same on a far bigger scale.

Watch the episode: A Moon Rocket Can Throw Off Your GPS 8:08

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The hole Artemis II left over America

Artemis II launched on 1 April 2026 from Kennedy Space Center in Florida, with four astronauts on a 10-day trip around the Moon. It was the first time in more than 50 years that astronauts travelled around the Moon. It also left a hole in the sky.

Researchers at National Cheng Kung University in Taiwan found it using US ground GPS stations built to measure tectonic plates. Stations meant to watch continents creep turned out to be good at catching a rocket. They saw changes in the ionosphere equal to positioning errors of several metres, in holes stretching over 4,000 km east to west across most of the US. The study came out as a preprint in July 2026 and has not yet been peer reviewed.

How does your phone work out where it is?

There are 31 GPS satellites carrying atomic clocks. A receiver uses signals from at least four and works out each distance from how long the signal took. Basic GPS is accurate to about 7 metres, 95% of the time.

The satellites orbit about 20,200 km up, so every signal has to pass through the ionosphere, the charged layer that starts about 50 km up. Its free electrons slow the signal, and a late signal makes you look further away than you are. For a single-frequency receiver, the effect can reach several tens of metres. Sunlight makes those electrons during the day and they recombine at night, so the delay depends on the place, the hour and the Sun's activity.

So the satellites also broadcast a guess. The Klobuchar model (1987) was designed to need as few numbers as possible: a fixed value for night and a smooth curve for the day. It removes about 50% of the ionosphere's error worldwide, which is decent for something small enough to fit in a radio broadcast. The GPS Joint Program Office had asked Jack Klobuchar to write it. In Google Maps, a light blue circle around the blue dot shows when Maps isn't sure where you are.

Receivers that listen on two frequencies remove more than 99.9% of the delay. That is the dual-frequency gear used for farming and surveying, accurate to a few centimetres, against a metre or less for single-frequency GPS in calm conditions. The model only knows ordinary days. It cannot see a rocket go through.

What does a rocket do to the ionosphere?

Rocket engines spray water and carbon dioxide into the ionosphere, cutting its charge by as much as 70%. The reaction glows red, the colour of red auroras. After a Falcon 9 launch in July 2023, a red glow spread over Arizona for almost 20 minutes. On 19 June 2022 another lit the sky from New York to the Carolinas, and many people took it for the northern lights.

This has been going on for years, and it is getting more common with record numbers of launches. On 25 August 2017, a Falcon 9 launching Taiwan's FORMOSAT-5 made a hole four times bigger than California. The holes are short-lived, because the ionosphere refills as soon as the Sun comes up, but they can cause sudden GPS errors.

The first large-scale hole measured came from the launch of Skylab on 14 May 1973: 1,000 to 2,000 km wide for 2 to 3 hours, caused by hydrogen and water from the Saturn V's exhaust. It was found by Mendillo, Hawkins and John A. Klobuchar. Yes, the same Klobuchar, who spent more than 25 years on how the ionosphere affects navigation signals and later wrote the model that cannot see a rocket.

Why the smaller burn made the bigger hole

Artemis II disturbed the ionosphere more than any other rocket launch to date, up to 10 times more than Starship test launches, though Starship has twice the liftoff thrust. Its 65-metre core stage left one hole. About 2 hours after liftoff, the upper stage fired at about 185 km, inside the ionosphere, and disturbed it far more.

Artemis II caused three separate disturbances, and study co-author Charles Lin says it was the first known mission to cause three:

Liftoff, with about 80 times the thrust of the second burn and 318 times the third.
About 2 hours later, the upper-stage burn. Its disturbance covered almost the entire US continent, the biggest ever recorded.
Over 24 hours later, the translunar injection burn, done by Orion's own main engine on its European Service Module.

The later burns were the weaker ones, yet they disturbed the ionosphere more. For a self-driving car, Lin said, a couple of metres is enough to change lanes. The researchers reported no widespread GPS outage, and the study has no evidence that self-driving cars or drones went wrong.

When the Sun does it instead

A rocket's effect is much shorter than a severe solar storm's, which can last days. On 10 May 2024, the Gannon storm, the first G5 geomagnetic storm in over two decades, hit Earth. It pushed auroras as far south as Mexico, Portugal and Spain.

In central US states, GPS signals were off by up to 70 m. The peak lasted about six hours, and disruption up to two days. In a severe storm, GPS can't model the changes, so errors rise to tens of metres or more.

It hit at planting season. Midwest farmers said their GPS-guided tractors acted "possessed", and corn planting was delayed. About 70% of planted acres in the US rely on GPS automated guidance, and Terry Griffin of Kansas State University put the cost to Midwest farmers at more than $500 million. Farms that were hit lost about $17,000 each on average. Aircraft landing on GPS can absorb errors up to 4 metres; the storm went far beyond that.

The Sun reached the maximum period of its 11-year cycle in 2024, solar maximum ran through 2025, and it is now in its declining phase. Rockets are not slowing down. Lin expects that with many more missions to the Moon and Mars, these effects will become much more significant.

When your blue dot drifts

Your phone crosses a layer of sky it cannot see and corrects with a guess about an ordinary day. A rocket, or the Sun, makes the day less ordinary. Next time your blue dot wanders into a river, look for the light blue circle around it, and then look up.

Has your phone's map ever put you somewhere you definitely weren't?

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