NASA’s Neil Gehrels Swift Observatory is expected to descend and burn up in Earth’s atmosphere after increased solar activity expanded the atmosphere and intensified drag on the spacecraft. NASA tried to raise Swift’s orbit over the summer, but the effort failed, and no established observational replacement is waiting in the wings.
Swift weighs 3,200 pounds (1,452 kilograms) and orbits about 200 miles (325 kilometers) above Earth. Engineers estimate it will become difficult to operate once it drops below 185 miles (300 kilometers) in early to mid-October. Then it will keep descending. It’s expected to burn up.
Why Swift is falling
Solar activity has increased over the past couple of years as the sun reached the peak of its 11-year cycle in 2024. Intense flares and coronal mass ejections expanded Earth’s atmosphere, which increased drag on the observatory. NASA scientists therefore predicted its descent in the fall.
Swift launched in November 2004 and has operated in low-Earth orbit as an astrophysics observatory. Its mission was to study gamma-ray bursts, described in the source as the universe’s most powerful explosions. It also observed other cosmic flashes, asteroids and comets. Named after fast-flying birds, Swift can rapidly turn to observe events such as flaring black holes. Its predicted re-entry comes just shy of the 22nd anniversary of its launch.
Swift’s mission scientists have gradually turned its instruments back on to collect data and make observations until the end. They’d shut the instruments off for months to reduce power use and keep the observatory from sinking. Turning them back on has accelerated its decline.
The failed rescue attempt
NASA and Arizona-based Katalyst Space Technologies tried to boost Swift’s orbit with LINK, a satellite developed, built and launched in nine months. LINK launched in early July but spun out of control in space. NASA Astrophysics Division director Shawn Domagal-Goldman said, “Without intervention, Swift was going to re-enter the atmosphere by year’s end.” He called the operation “a high-risk, high-reward mission.”
Katalyst went ahead with a planned mid-August rendezvous as a demonstration rather than a rescue, since LINK had ongoing orientation issues. Engineers used its thrusters to slow the unexpected spin and uploaded new flight software, but the maneuver depleted propellant. Katalyst said LINK no longer had enough fuel to safely carry out the planned capture and orbit-raising phase.
In the first week of September, LINK came within 7.5 to 9 miles (12 to 15 kilometers) of Swift, testing how a future servicing mission might approach a satellite or telescope not designed for servicing in space. LINK deployed its three robotic arms, originally intended to grab Swift, and fired its three electric propulsion thrusters. Katalyst said LINK operated in space for 85 days before it re-entered Earth’s atmosphere on September 25.
What the mission leaves behind
Katalyst Space CEO Ghonhee Lee said the company hadn’t achieved every objective, but had moved from mission concept to launching and operating what he called “the first commercial space robot” in less than a year. Katalyst plans to apply LINK’s data and lessons to its next generation of spacecraft for servicing existing space missions.
Domagal-Goldman said the effort advanced U.S. spacecraft-servicing technology, tested how satellites could be operated to extend their time in low Earth orbit and challenged the team to meet unprecedented mission timelines. Swift principal investigator S. Bradley Cenko said its namesake would have celebrated the effort as part of the observatory’s legacy.
A statement from space-tracking company LeoLabs said some Swift hardware could survive re-entry because of the spacecraft’s size, but the probability of debris causing significant property damage or physical harm was “very small.” LeoLabs said surviving debris was more likely to fall into the ocean or uninhabited land. NASA didn’t respond to a request for comment on potential re-entry risks.