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An air-launched Northrop Grumman Pegasus XL rocket is scheduled to fly for the very last time early Tuesday morning (June 30), sending a private spacecraft on a rescue mission to save one of NASA's most iconic space telescopes from falling back to Earth.

The Swift Boost mission will send the LINK satellite, built by Arizona-based Katalyst Space Technologies, to grapple NASA's Neil Gehrels Swift Observatory and tow it to a stable orbit, saving it from impending destruction as its trajectory dips farther into the atmosphere . LINK, aboard Pegasus, will take off from Bucholz Army Airfield at Kwajalein Atoll in the Marshall Islands, secured to Northrop Grumman's L-1011 Stargazer jet.

Liftoff is scheduled for 6:23 a.m. EDT (1023 GMT), Tuesday. Pegasus will be released by Stargazer once the aircraft reaches about 39,000 feet (12,000 meters), traveling at Mach 0.82. Five seconds later, the rocket will ignite its engine and ascend to orbit.

Pegasus is a three-stage, solid rocket-propelled launch vehicle that measures 55 feet in length (16.9 meters), capable of delivering up to 1,000 pounds (454 kg) into low-earth orbit (LEO). Following its separation from the Stargazer, the rocket's stages are ignited in sequence to reach its intended altitude in about 10 minutes.

Pegasus debuted in 1990, and has since flown 45 missions. Its aerial deployment and flexibility to take off from different airfields allows the rocket to enter hard-to-reach orbital inclinations that are inaccessible from many major spaceports. That's one of the reasons Pegasus is launching LINK, a robotic servicing satellite that can reach Swift's low 20.6-degree inclination relative to Earth's equator.

Another reason NASA chose the Pegasus rocket for this mission was time, which is running out for Swift. The $500 million Swift Observatory was launched in November 2004 to study gamma-ray bursts and other high-energy events across the universe. And, despite its more than 20 years of operation, Swift is still providing scientific value.

Its orbit, though, has begun to dip dangerously low, where recent solar activity has increased atmospheric drag at higher LEO altitudes and will soon overcome the spacecraft, dragging it to its ultimate demise. Swift, unfortunately, was not designed to be serviced, and wasn't built with the thrusters it needs to raise its own orbit.

Enter LINK.

After its release from Pegasus' payload bay and initial systems checkouts, the Katalyst spacecraft will begin its long course to rendezvous with Swift. Before beginning its final approach, LINK will spend two to three weeks performing observations of Swift to assess optimal grapple points on the observatory.

Stargazer flight path prior to Pegasus XL deployment. (Image credit: Northrop Grumman) LINK measures about 4.9 feet (1.5 m) tall, and is equipped with three robotic arms that will be used to capture Swift, which stretches about 12.7 feet (3.9 m). Once a grab-point is chosen and Swift secured, LINK will fire a set of gentle ion thrusters that will slowly raise the pair's orbit over the next several months.

LINK is poised to be the first private spacecraft to attempt to capture an uncrewed U.S. government satellite. NASA selected Katalyst for the task in September 2025, with less than a year to carry out LINK's design, manufacture and testing. Despite its urgency and the relative short notice to get LINK in orbit, the entire Swift rescue mission and launch only cost NASA $30 million.

"While NASA could have allowed Swift to re-enter the atmosphere, the situation presented an opportunity to demonstrate a key capability for the future of space exploration. This daring approach also extends Swift’s scientific lifetime and is more affordable than replacing the observatory’s unique capabilities," NASA states on the Swift Boost mission page .

The goal is to return Swift to its original altitude of about 373 miles (600 km), which will extend the observatory's life expectancy by a number of years, provided its systems continue to operate as designed.