In a historic first, Northrop Grumman is set to launch a rescue mission to save a NASA space telescope from plunging into the Earth's atmosphere using a service robot to capture the stricken craft and boost it into a new, safer orbit.
In November 2004, NASA launched the Neil Gehrels Swift Observatory to study gamma-ray bursts and monitor the afterglow in X-ray and UV/visible light at the location. For almost 22 years, the robotic satellite has carried out its mission, but, like thousands of spacecraft before it, the space telescope is now facing the inevitable fiery and fatal consequences of years of orbital decay that will cause it to reenter the atmosphere.
Until very recently, that would have been the end of the story. As has happened many times before, those who sent the telescope into orbit would have no choice but to resign themselves to watching helplessly while a perfectly good spacecraft met its end. However, that is changing thanks to advances in launchers and robotics that make a rescue mission feasible.
The plan is to use a Northrop Grumman air-launched Pegasus XL rocket carried aloft by the company's Stargazer L-1011 carrier aircraft and loaded with a roughly 880-lb (400-kg) LINK spacecraft built by Katalyst Space Technologies. After being released over the equatorial waters near Kwajalein Atoll in the Marshall Islands, the Pegasus will fire its solid-rocket motor and send LINK into Swift's precise orbital plane, which has an inclination of 20.6° to the equator.
Once separated from the Pegasus upper stage, LINK will use its own onboard propulsion system to chase Swift over a number of days or even weeks until it matches the trajectory of the space telescope, for an interception with both traveling at about 17,000 mph (27,000 km/h).
That may sound relatively simple, but it's far from it. Because of the latency of radio signals between mission control and LINK, the rescue craft must rely entirely on its autonomous onboard computers processing data from the optical cameras, LiDAR ranging sensors, guidance flight software, and real-time imaging.
All of this has to be very carefully considered regarding time and there isn't much of it. Swift was never designed for outside maintenance or docking with another spacecraft, so there are no standard docking rings, magnetic capture fixtures, or cooperative navigation beacons. In addition, the physical condition of the satellite is unknown after more than two decades.
As a result, LINK must scan Swift and assess the situation while looking for ground-handling fixtures originally used to transport the space telescope before being installed on the Delta rocket that launched it. If all goes well, LINK will extend three rather alarming looking robotic arms that will grasp these fixtures.
Once secured, LINK will take over control of Swift and use its onboard thrusters to boost the telescope to a new orbit of about 373 miles (600 km), extending the observatory's life for a comfortable number of years.
If successful, this will constitute the first capture of an unprepared US government satellite by a commercial vehicle and the first of a scientific satellite that was not designed for capture.
The launch of the rescue mission is currently scheduled for late June 2026.
"Pegasus has been instrumental in launching science satellites over the years, and doing this as a rapid response mission from Kwajalein Atoll truly highlights what Pegasus can do: quick assembly, testing, and global repositioning," said Steve Hollo, chief engineer of Pegasus. "The latest mission features a complete avionics upgrade to modernize the rocket while carrying forward decades of technological heritage. Plus, not being tied to a single launch site gives us incredible flexibility and responsiveness that few other vehicles can match."
Source: Northrop Grumman
