Space Weather Dooms Starlink Cluster

SpaceX revealed today that almost all of the 49 Starlink satellites it launched last week were affected by a geomagnetic storm and will reenter or have already. Such “space weather” storms are created by the interaction of solar particles with the atmosphere.

SpaceX successfully launched the satellites on Thursday at 1:13 pm ET from Kennedy Space Center, FL on a Falcon 9 rocket. They are part of SpaceX’s growing constellation of thousands of small (260 kilogram/573 pound) satellites providing global broadband Internet service. Over 2,000 Starlink satellites have been launched already, not even half of the total planned for this first phase of the system. Eventually there will be as many as 42,000.

The Starlink satellites are initially placed in a relatively low Earth orbit for checkout, after which they use onboard propulsion to raise their altitude to their operational orbit at 550 kilometers (340 miles).

SpaceX said tonight that when these satellites were still in their initial orbit with a perigee of 210 kilometers (130 miles), a geomagnetic storm substantially increased atmospheric density causing drag on the satellites to increase by 50 percent. They were commanded into safe mode to fly edge-on and reduce drag, but then they could not exit safe mode and begin the orbit raising maneuvers.

“Preliminary analysis show [sic] 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. The deorbiting satellites pose zero collision risk with other satellites and by design demise upon atmospheric reentry—meaning no orbital debris is created and no satellite parts hit the ground.”

It is just one example of the vulnerability of satellites to space weather, which is caused by solar activity. In this case a surge in solar emissions increased the density of the lower atmosphere and therefore drag. In general, low Earth satellites might have to compensate for atmopsheric drag about four times a year, but during periods of high solar activity it can be required every two-three weeks according to NOAA’s Space Weather Prediction Center.

SWPC did warn of a “moderate” geomagnetic storm February 2-3.

Although they lost the satellites, SpaceX put a positive spin on the event as a demonstration of its commitment to the sustainable use of space. The company, along with others planning similar or even larger constellations, are often cricitized for cluttering space to the detriment of other space operators and ground-based astronomers.

SpaceX pointed out that they put their satellites into the low orbit for checkout precisely because they will quickly reenter if anything goes awry. “While the low deployment altitude requires more capable satellites at a considerable cost to us, it’s the right thing to do to maintain a sustainable space environment.”

The February 3 launch was the third for Starlink just this year and at least one more is scheduled this month.