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Swift moves - can a space robot rescue this falling telescope?

A gold‑coloured space telescope with solar panels and a cylindrical black opening floats in space above the Earth.NASA

Artist's impression of the Swift observatory in orbit

A robot spacecraft has been launched on a daring mission to save a Nasa space telescope from falling back to Earth.

The telescope is called the Neil Gehrels Swift Observatory, but it is often just called Swift for short.

It was launched in 2004 and has spent more than 20 years studying some of the most powerful explosions in the Universe.

These include gamma-ray bursts, which are huge blasts of energy that can happen when massive stars die or when objects in space crash together.

Swift is special because it can react very quickly. When it spots a sudden burst of energy, it can turn towards it and help other telescopes know where to look.

But now Swift has a problem...

A grainy image of concentric purple and yellow circles made up of small points. The centre is bright yellow and the outer corners of the image are black.NASA/Swift/A. Beardmore (University of Leicester)

In 2022, Swift captured this image of a gamma-ray burst from a massive star dying two billion light-years from Earth

In a bright yellow test chamber, six engineers in white lab coats and hairnets stand around a large, boxy spacecraft suspended from the ceiling. They reach up with tools and gloved hands, examining its exposed wires, pipes, and shiny metal panels during a precision vibration test.NASA/Scott Wiessinger

Engineers from Katalyst Space Technologies built their rescue robot in just eight months

Even though space seems empty, there are still tiny traces of Earth's atmosphere high above the planet.

This causes particles rub against satellites in low Earth orbit and slow them down. When a satellite slows down, it begins to drop lower.

A period of high activity from our Sun has made Earth's upper atmosphere expand even further into space, increasing this drag on Swift.

If nothing is done, Swift could fall into the atmosphere and burn up. That happens to satellites fairly often, but losing Swift would be a big blow for scientists because it still does valuable work.

To try and save Swift, Nasa has hired a company called Katalyst Space Technologies, based in Arizona in the US, to attempt the rescue.

In just eight months, the company built a spacecraft called LINK - which carried on a rocket that was carried high above the Pacific Ocean by an aircraft before being released to travel up into space.

The graphic has a black space background with Earth’s curved green edge at the bottom. A white dashed line shows the path of a small grey “Katalyst” spacecraft moving upward to a large yellow-and-blue Swift observatory satellite. Four red numbered circles mark stages: 1, Katalyst is launched into orbit; 2, it approaches and docks with Swift; 3, it fires engines, pushing Swift to a higher orbit, shown by an upward grey arrow; 4, Katalyst detaches, falls on a curved path, and burns up with an orange glow in Earth’s atmosphere. White text labels each step.

The rescue mission, launched on Friday, has never been attempted before, and Dr Simeon Barber, a space scientist at the Open University, has said it is "high risk".

"But Nasa obviously thinks it's worth a go... because it's an important telescope that enables us to study super high-energy phenomena that we have no other means to study."

LINK has cameras, sensors, small thrusters and three robotic arms. Over the next few weeks, it will check its systems and carefully move closer to Swift. This is difficult because both spacecraft are moving very fast around Earth.

If everything goes well, LINK will gently grab Swift and slowly move it to a higher, safer orbit. This will not be a quick shove. The rescue craft will use its small engines over several weeks to raise the telescope's path around Earth.

The mission is risky because Swift was never designed to be caught in space. But if LINK succeeds, it could help to show how future spacecraft might rescue other satellites - such as the famous Hubble Space Telescope - too.