The rocket company, owned by Elon Musk, has launched over 1,500 of its Starlink satellites into orbit over the past several months with plans for thousands more on the way.
Circling the Earth in a region of space called low-Earth orbit (LEO), these satellites work by providing an internet connection to paying customers on the ground.
Operating in low-Earth orbit comes with benefits such as rapid transfer of information between the satellites and the Earth, known as latency. At the same time, operating relatively close to Earth means that the satellites are constantly being slightly slowed down by what’s left of our planet’s atmosphere at their operating height—around 210 kilometers or 130 miles.
According to the U.S. National Oceanic and Atmospheric Administration’s Space Weather Prediction Center (SWPC), atmospheric drag for satellites can be thought of as similar to walking against a high wind and feeling it push against the direction of travel.
In particular, drag has a significant impact on spacecraft in LEO, which is generally defined as any orbit below 1,200 miles.
The effect of the sun on atmospheric drag depends on how active the sun is in a particular time period, but it can be significant. The SWPC states that when the sun is quiet, satellites in LEO might have to boost their orbits using on-board thrusters about four times per year to make up for atmospheric drag. When the sun is at its highest level of activity within its 11-year solar cycle, satellites might have to boost their orbits once every two to three weeks.
On February 3rd, SpaceX launched a new batch of 49 Starlink satellites into orbit from the Kennedy Space Center in Florida.
Soon after launch, Earth was affected by a geomagnetic storm, which is a natural phenomenon that occurs when our planet is hit by particularly large amounts of energy from the sun, sometimes as a result of coronal mass ejections. These storms can cause all sorts of problems to electrical systems and satellite operations.
These storms also have the effect of heating up the atmosphere, which in turn increases the density of the atmosphere where the Starlink satellites operate. According to SpaceX, the fresh batch of Starlink satellites faced atmospheric drag up to 50 percent higher than during previous launches.
Faced with this extra atmospheric resistance, the fresh batch of Starlink satellites entered a “safe-mode” in which they flew edge-on with the atmosphere to minimize drag. Unfortunately for SpaceX, the satellites were unable to leave “safe-mode” in time to correct their orbits.
The company said on its website on Tuesday: “Preliminary analysis shows the increased drag at the low altitudes prevented the satellites from leaving safe-mode to begin orbit raising maneuvers, and up to 40 of the satellites will reenter or already have reentered the Earth’s atmosphere.”
SpaceX said the satellites “pose zero collision risk” to other satellites as they de-orbit and are designed to burn up as they re-enter the atmosphere so that “no satellite parts hit the ground”.
The value of the lost satellites was not immediately known.
