NASA made a good bet when it built the Swift Space Telescope. Launched in 2004, Swift has spent more than a generation observing gamma ray bursts—the most powerful forms of energy since the Big Bang. The bursts last a few milliseconds to a few hundred seconds, and are thought to be caused by the merger of two neutron stars (the short bursts), or the collapse of large stars, creating a black hole (the long ones). Whatever the source, Swift has long been on the case, and at a relative bargain—just $250 million. The James Webb Space Telescope, launched in 2021, cost $10 billion.
But Swift is in trouble. The satellite ordinarily orbits the Earth at an altitude of 370 miles. However, atmospheric drag, even at that nosebleed elevation, has slowly pulled Swift down to 210 miles and falling, putting it on target to reenter and burn up as soon as the end of this year—and taking NASA’s quarter-billion-dollar investment with it. The so-called solar maximum, when the sun is at the most energetic point in its 11-year cycle, hasn’t helped any. Solar maximum was reached in late 2024, heating and puffing the Earth’s atmosphere, increasing the drag on all satellites.
NASA, however, has a rescue mission ready to go. Poised on a tarmac on the Kwajalein Atoll in the western Pacific and set to fly as early as tomorrow, July 3, is an L-1011 Stargazer jet, carrying a three-stage Pegasus rocket under its belly; the Pegasus is itself carrying a refrigerator-sized satellite called Link. If all goes according to plan, the plane will fly to 40,000 ft. and there release the Pegasus, which will fire its engines and deliver Link into an orbit matching Swift’s. From there, Link will rendezvous with Swift, take hold of it with its three grappling arms and use its thrusters to carry it to a higher orbit. That’s what the checklist calls for, at least, but there are an awful lot of steps that have to go just-so for the mission to work as planned.
For starters there’s the Pegasus, a 55-ft. long three-stage rocket using rubbery, solid fuel as a propellant. En route to orbit, each of the three stages has to fire on time, in sequence if the payload is to get where it’s going. Pegasus rockets were introduced in 1990 and have since flown 45 missions successfully. But this time around the charm was broken. Launch of the Swift rescue mission was originally scheduled for July 2, and the L-1011 jet did get off the ground, but mission controllers detected an undisclosed problem in the Pegasus system and called the plane back to the hangar.
“The date of the next launch attempt for this mission … will be determined after teams have reviewed data from today’s attempt,” NASA said in a short-on-details statement.
Whenever Pegasus does get to space, things won’t be as simple as just releasing Link to speed toward Swift and carry it out of danger. It will take as much as a month to find and maneuver to the space telescope in the first place, with Link relying on slow, gentle ion thrusters to get it where it’s going. When the rescue ship does reach Swift it will spend another two to three weeks pirouetting around it, looking for promising grappling points for its robotic arms to grab onto. Only when it finds them will it take hold of Swift and begin the slow two- or three-month process of raising its orbit.
All of these handle-with-care protocols are necessitated by the design and condition of Swift. The telescope was not built to be serviced the way the Hubble Space Telescope has been numerous times since its 1990 launch and thus was not designed with handles or brackets to accommodate robotic arms. What’s more, Swift has been in space so long its thermal insulation blankets might have grown brittle meaning too much jostling or too much speed in getting from place to place could damage the ship.
If the mission does come off as planned, it will be a capstone to the career of the Northrop-Grumman-built Pegasus line, which had not flown since 2021 and was expected to be retired in favor of more advanced jet-launched rockets in the development pipeline. It was just by chance that Northrop-Grumman had one more Pegasus in inventory when NASA came calling last year with its plans for the Swift rescue. That was good news, since launching Link atop a traditional rocket like the Falcon 9 was not an option.
That’s because Swift flies in an orbit inclined 20.6° to the equator to avoid passing through the Van Allen radiation belts. That’s a shallow inclination compared to the 28.5° tilt at which the space shuttles flew and the 51.6° orbit the International Space Station inscribes. Swift’s orbit is hard to reach from fixed launch pads that a vertical rocket like the Falcon 9 would use, but an air launch provides much more flexibility in picking an inclination. An air launch is also cheap—as these things go. The Swift rescue mission carries a price tag of just $30 million—which is significantly less than the $74 million it costs to buy the services of a Falcon 9, and far less than the $250 million it would cost to abandon and replace Swift.
Launching by plane also means an easy liftoff—just gas up and go, as opposed to the extensive preparations necessary to get a rocket off the ground. As soon as the Pegasus engineers figure out what caused the recent abort they can thus proceed with saving Swift. The telescope has done yeoman’s work for the past two decades, and with luck, it has years more ahead of it.