WASHINGTON — A Pegasus XL launched a mission to re-boost NASA’s astrophysics spacecraft in what could be that rocket’s final flight.
After a three-day delay due to weather and technical problems, the Northrop Grumman Pegasus XL rocket was deployed from its L-1011 carrier aircraft at 4:36 a.m. Eastern on July 3. The rocket delivered its payload, the Catalyst Space Launch 425-kilogram Link spacecraft, into low Earth orbit about 13 minutes later.
NASA said in a statement more than seven hours later that controllers had established contact with Link but provided no additional information about the spacecraft’s position.
Catalyst Space developed Link under a $30 million NASA contract awarded last September for an effort to rescue the Neal Gehrels Swift Observatory, or Swift, spacecraft in low Earth orbit. That gamma-ray observatory is in a decaying orbit and is in danger of re-entry late this year or early next year.
The company repurposed the low Earth orbit technology demonstration of its satellite servicing technology already in development for the Swift Reboost mission, providing a launch-ready spacecraft within nine months of contract award.
“This is an absolutely unprecedented development timeline,” said Kieran Wilson, LINK’s principal investigator at Catalyst, at a prelaunch briefing on June 17.
Now in orbit, Catalyst will spend the next two weeks investigating the spacecraft in orbit, after which Link will begin its approach to Swift and survey the spacecraft, a process expected to take two to three weeks.
That survey will include examining Swift and determining the best locations on the spacecraft where Link’s three robotic arms can operate. Project officials said before launch that although they had identified locations on Swift where they thought the weapons could hold fire, they wanted to inspect the spacecraft to see if they were still suitable for capture.
“We believe that as long as we have a spacecraft that can function at a fundamental level, that gives us the freedom and flexibility to work through any issues we encounter during rendezvous and more challenging dynamic operations,” Wilson said. Swift is estimated to remain above an altitude of 300 kilometers, below which a reboost mission is not possible until at least October.
Swift will be able to assist in that effort by stepping up with the help of LINK. “Swift is an unprepared but cooperative participant in this encounter,” he said. “We will move through a group of maneuvers as a tandem team between Swift Mission Ops and Link Mission Ops teams to conduct observations at various ranges.”
If Link can connect to Swift, it will use its ion engine to raise the orbit, which is currently about 360 kilometers, to 550 to 600 kilometers. Link will then separate and use its remaining propellant to lower itself and accelerate its deorbit. The reboot process will take three months, and once the link is gone, Swift will resume science operations.
NASA has called the Swift reboost mission a “high-risk, high-reward” effort because of the challenges faced in trying to raise the orbit of a spacecraft not designed for service, as well as the Catalyst spacecraft’s limited space flight experience. However, the agency argues that if successful, it would also benefit other NASA missions and the broader industry.
“We didn’t want to set a precedent that anything coming out of orbit would be promoted,” said Shawn Domagal-Goldman, director of NASA’s Astrophysics Division, at a prelaunch briefing.
In the case of Swift, extending its mission helps the astrophysics community because of the mission’s importance in monitoring gamma-ray bursts and other high-energy events.
“This is an observatory with unique capabilities for astrophysics,” he said. “So we decided, yes, we want to save it this time because of how special it is.”
A successful Swift boost could enable similar efforts, including with the Hubble Space Telescope, whose orbit is also decaying and could re-enter in the first half of the 2030s. Domagal-Goldman said at an advisory committee meeting in June that he was open to a Hubble boost mission, provided the telescope’s operating costs could be reduced.
This launch is also the last scheduled flight of the Pegasus rocket. The air-launched rocket was developed by Orbital Sciences Corp. and first flown in 1990. The vehicle, which launched sometimes five to six times a year in the 1990s, has flown only six times in the past 15 years. The launch of Link was the first Pegasus launch since a reactive space mission in June 2021.
Catalyst Space chose Pegasus last November because of Swift’s unique orbit with an inclination of about 21 degrees. Northrop reportedly offered Catalyst a Pegasus rocket for storage at a reduced price for another customer.
At a prelaunch briefing, Wes Collier, vice president of launch systems at Northrop Grumman, left the door open for future Pegasus launches. “We are certainly open to follow-on contracts or new opportunities for Pegasus,” he said. “We think this is a great system for future reactive launch opportunities.”
Collier expressed similar sentiments in a Northrop statement after the launch.
“Ready for launch in less than eight months, Pegasus is the preferred choice for missions that need to land right now,” he said. “Its air-launch design and proven Orion motors mean payloads can reach orbits that are difficult for other rockets to reach.”
