On Tuesday, an L-1011 Stargazer aircraft will take off from the Marshall Islands, 2,300 miles southwest of Hawaii. A rocket will drop from the plane, then rise to carry a spacecraft called LINK into low Earth orbit. LINK’s mission is to saving one of the most scientifically productive operating astronomical facilities: that of NASA Neil Gehrels Swift Observatory, which astronomers call “Swift”.
Swift sinks. The satellite circled the Earth about once every hour and a half for more than two decades, and over time, friction with particles in the upper atmosphere caused its orbit to disintegrate. Unusually intense solar activity in recent years has accelerated the decline. If nothing is done, the spacecraft and the three telescopes on board will burn up in the atmosphere within months.
To save Swift, NASA hired Arizona-based Katalyst Space Technologies to build LINK. Katalyst had just nine months to design, build, test and launch a satellite to do something that has never been done: recover a spacecraft that was not designed to be serviced (the “capture” stage of the mission), then return it to its original orbit (the “boost”). If successful, the mission will demonstrate an important capability for the commercial space industry and give Swift decades of additional life at a much lower cost, in much less time, than it would have taken to build a new space observatory.
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The challenges for my own research became very clear one day in February. As an astronomer, I did what I’ve done nearly 100 times before: I filled out a short web form, called a “target of opportunity” (ToO) request, to ask Swift to pivot and point at a particular part of the sky. My colleagues and I had discovered a supernova in a distant galaxy, and we urgently needed X-ray and ultraviolet data: the star had exploded just days before, and the glow from the debris would soon be too faint to study. As usual, we turned to Swift, named after an agile insect-hunting bird: although it’s as long as a pickup truck, Swift can point anywhere in space in a matter of minutes. I expected a response within 24 hours, so when I didn’t hear anything for a day, I contacted a member of the operations team, who told me that Swift had stopped taking ToO requests in order to point in any direction that minimized orbital drag. I knew Swift was in danger, but that’s when I realized that without it I wouldn’t be able to get the data I needed.
Capture is the riskiest step in LINK’s mission. The tentative plan is for the spacecraft’s robotic arms to grab solid metal panels from Swift’s corners. But the observatory is covered in some kind of aluminum foil for thermal insulation, and no one knows what condition that layer is in because no one has seen Swift up close in 20 years.
Engineers from Katalyst Space Technologies in Flagstaff, Arizona, stabilize their LINK robotic servicing spacecraft as it moves through a vibration chamber at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, April 15, 2026. The vibration chamber simulates the intense shaking LINK will experience during launch.
NASA/Scott Wiessinger
When LINK arrives in orbit, it will first conduct a photoshoot, imagining Swift in different orientations and lighting conditions to determine which part it should try to capture. The boost phase of the mission is less risky than the capture, but it is also complicated. Once LINK seizes Swift, LINK will use its ion propulsion thrusters to push the pair into higher and higher orbits for several months. During this time, LINK must follow many rules regarding the direction the spacecraft can head in order to charge its solar panels and protect Swift’s mirrors and instruments. When they reach an altitude close to Swift’s original orbit, LINK will let go. At this point, astronomers will take over to restore the observatory to its role as the most important tool for ephemeral astronomy.
Transitional astronomy is the study of cosmic phenomena that come and go on a human scale, notably star explosions in the form of supernovae. Swift was originally designed to study a rare type of transient called gamma bursts – flashes of gamma rays lasting seconds that result from the most energetic explosions in the universe. Swift discovered nearly 2,000 gamma-ray bursts and revolutionized our understanding of their origins, helping to establish that they can arise from merging neutron stars in addition to single star explosions, and he even found bursts originating from the first generations of stars in the universe.
Swift has also contributed to the discovery of new and unexpected phenomena, driven by its users: any astronomer, anywhere in the world, can submit a ToO request in a short time. For example, in 2018, a ground-based optical facility called ATLAS (Asteroid Terrestrial-Impact Last Alert System) discovered a transient that moved so quickly and was so bright that astronomers all thought it must be some sort of prominent source in the Milky Way. Liliana Rivera Sandoval, now an assistant professor at the University of Texas Rio Grande Valley, submitted a ToO request to Swift, which, to everyone’s surprise, revealed bright X-rays – a sure sign that it was much further away and therefore much, much more energetic than something in our own galaxy. This event, AT2018cow (“the Cow”), turned out to be one of the most exciting objects I studied as a doctoral student and became the prototype for a fascinating new class of travelers: today the menagerie includes events we nickname the Camel, the Tasmanian Devil and the Whippet. Without Swift, it probably would have taken weeks instead of days to convince us that the source was interesting.
No other existing or planned telescope can simultaneously observe multiple ranges of the electromagnetic spectrum in such a short time frame. Additionally, Swift has the ability to take risks. In 2023, 87% of Swift’s time was spent on ToO observations: on average five requests are received each day, and a small operational team evaluates the requests scientifically (“Is this interesting?”) and practically (“Is it feasible?”). Swift receives more annual observing requests than any NASA facility except the James Webb Space Telescope, and its scientific portfolio is vast, extending to comets and planets in other solar systems.
Swift’s capabilities are only growing in importance. So far, ephemeral astronomers have documented about 200,000 cosmic explosions, most discovered by optical telescopes when they are days or weeks old. Today, the landscape of discovery is transforming. With new facilities coming online, we are about to discover a large number of transients in unexplored parts of the electromagnetic spectrum. For example, Israel’s ULTRASAT (Ultraviolet Transient Astronomy Satellite), launched in 2027, and NASA’s UVEX (Ultraviolet Explorer), scheduled to launch in 2030, will be the first transient space telescopes dedicated to the high-energy ultraviolet part of the spectrum. And the Rubin Observatory in Chile, opened last year, is expected to discover 10 times more transients than previous optical telescopes. Gravitational wave detectors should detect merging black holes and neutron stars, even in the most distant parts of the universe. And it will become much more common to discover explosions when they are only minutes old, thanks to facilities like the Argus Array, under development in Texas.
However, discovering tens of millions of possible transients every night is not enough. We need Swift to measure their fundamental properties such as temperature and explosion size. Swift will also help us determine where exactly these explosions are occurring, allowing other telescopes to point to that location and decide which ones are unusual and therefore worth studying in more detail. If the LINK mission is successful, it will give Swift new life at just the right time so we can answer long-standing questions about the most powerful explosions known in nature.
