The LINK spacecraft (centre) is tested at NASA’s Goddard Space Flight Center. The craft is scheduled to blast off as early as 27 June on a satellite-rescue mission.Credit: NASA/Sophia Roberts
The mission is risky, daring and unprecedented: save an ageing NASA satellite from an impending fiery death. The rescue effort, which is slated to begin as early as this week, could pave the way towards extending the life of other space observatories — even, maybe, the Hubble Space Telescope.
The goal of the upcoming mission is to raise the orbit of the Neil Gehrels Swift Observatory, an astronomy satellite that launched in 2004 that is still gathering valuable data on cosmic explosions. Engineers will send a small spacecraft to fly to Swift, grab it with extendable arms and ferry it upwards by around 200 kilometres. That should be high enough to get Swift past the atmospheric drag that would otherwise force it to fall out of the sky by the end of this year.
If the mission succeeds, it will be the first time that a robotic spacecraft has carried a science satellite to a higher orbit to extend its lifespan. “I do think it’s a proof of concept for [Hubble] and similar future spacecraft,” says Jonathan McDowell, a spaceflight historian based in Bromley, UK.
Space tug
Although this mission would be a first for a science satellite, a few crewed space stations have received a boost, such as by docking with small spaceships that then fire their thrusters. Astronauts also used the space shuttle to boost Hubble’s orbit during five servicing visits between 1993 and 2009. But most satellites eventually fall towards Earth as their orbits degrade over time.
For Swift, this would have happened earlier this year had NASA not realized that it was falling faster than expected and stepped in to adjust it. The satellite was falling rapidly because the Sun is near the peak of its 11-year cycle of activity, and solar storms hitting Earth have caused the planet’s atmosphere to expand slightly. That caused more atmospheric drag on Swift, which began its life 600 kilometres up but is now just 370 kilometres above Earth’s surface.
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Despite its age, Swift still plays an important part in identifying high-energy cosmic explosions and alerting other observatories so that they can study them. Among its many discoveries, Swift has probed mysterious gamma-ray explosions and monster black holes. Its last scientific target before NASA turned it off in February to prepare for the re-boost mission was a blazar, an intensely luminous galactic core.
All of that research made Swift a worthy target for a hail-mary mission. “We want to go save this one, this time,” says Shawn Domagal-Goldman, head of astrophysics at NASA in Washington DC.
NASA awarded US$30 million to Katalyst Space Technologies, an aerospace company based in Flagstaff, Arizona, to boost Swift. As early as 27 June, a rocket will launch from Kwajalein Atoll in the Marshall Islands, carrying a small, blocky spacecraft named LINK that will take several weeks to make its way to Swift.
After careful manoeuvring, LINK will extend up to three grappling arms to attach itself to the observatory. It will then fire its engines to raise both itself and Swift higher, over the course of another month or two, to around 600 kilometres above Earth’s surface. In a best-case scenario, Swift could be doing science again well before the end of the year, says John Nousek, an astronomer at the Pennsylvania State University in University Park who oversees Swift’s mission operations.
