The American space agency mission will observe the Sun’s outer atmosphere – the corona – to learn how the mass and energy there become the solar wind.

Four suitcase-sized spacecraft will be used to build 3D maps of the corona, as part of attempts to improve space weather forecasting.

The camera systems installed on the spacecraft were developed by RAL Space, based in Harwell, Oxfordshire.

Solar wind is usually harmless, and is responsible for producing the Northern and Southern Lights displays.

However, severe solar storms can interfere with aspects of everyday life including GPS systems, power grids, and vital global communications on Earth.

The Nasa mission aims to explore how solar wind evolves as it expands outwards from the the Sun’s atmosphere into the wider solar system.

It’s hoped that by capturing images of the Sun’s corona and the solar wind together, scientists will be able to better understand a region of space known as the inner heliosphere.

The region is effectively a vast magnetic bubble that surrounds the Sun that is formed by the solar wind.

As part of the operation, scientists, engineers and technicians from RAL Space have developed four specialised cameras that the company said would “capture a new perspective of the evolving solar wind”.

Once the spacecraft are in orbit, RAL Space will also be responsible for making sure the equipment on the satellites can provide accurate measurements back to Earth.

Dr Jackie Davies, from RAL Space, said the latest mission built on the company’s “extensive heritage in leading, and contributing to, solar and solar wind imaging instruments”.

She said the company was “thrilled” to be working alongside Nasa and over US based teams on the “pioneering” project.

She added that she “can’t wait to see what new insights our technological and scientific input will reveal in the coming months”.

Nasa’s Polarimeter to Unify the Corona and Heliosphere (PUNCH) mission is set to launch in the early hours of Friday, UK time.

The four ten-and-a-half stone (67kg) satellites will orbit the Earth for the duration of the mission, which is expected to last two years.

Ms Williams and fellow astronaut Butch Wilmore were due to return to Earth after a week-long mission in June 2024 but their return has been delayed because of a technical issue.

They now won’t be back until late March or possibly April.

Ms Williams – an experienced astronaut who has conducted many spacewalks during previous stays aboard the ISS – teamed up with astronaut Nick Hague on Thursday to perform maintenance on the craft.

Their tasks include repairing equipment that governs station orientation, patch light filters on the NICER X-ray telescope, and replacing a reflector device on an international docking adapter.

Additionally, the pair will check access areas and connector tools that will be used for future maintenance work on the Alpha Magnetic Spectrometer, a particle physics experiment module mounted on the ISS.

Ms Williams will conduct a second spacewalk on 23 January with Mr Wilmore.

Together, they will remove a radio frequency group antenna assembly (a collection of components designed to transmit and receive radio waves) and collect surface samples for microorganism analysis.

They will also prepare a backup elbow joint for the Canadarm2 robotic arm by positioning the joint in the optimal configuration for a quick replacement if needed.

Each spacewalk is expected to last about six and a half hours.

Nasa is providing live coverage of both spacewalks that can be viewed here.

Nicole McElroy, a Flight Director at Nasa, said in a press briefing before the spacewalk that “The road to our preparations for all of these EVAs (extra-vehicular activity) has been going well.

“The crew on board has been studying their procedures, getting familiar with all of the tasks, and are really excited and looking forward to going out the door.”

Ms Williams and Mr Wilmore went on what was meant to be an eight day mission to the ISS aboard Boeing’s Starliner in June 2024.

However, technical issues including helium leaks and thruster malfunctions meant that the Starliner was unsafe for their return.

Nasa plans to bring them back to Earth in late March aboard a spaceship built by SpaceX, a rival company of Boeing.

Despite these setbacks, the astronauts have continued their work aboard the ISS while awaiting a safe journey home.

The Parker Solar Probe is plunging into our star’s outer atmosphere, enduring brutal temperatures and extreme radiation.

It’s out of communication for several days during this burning hot fly-by and scientists will be waiting for a signal, expected on 27 December, to see if it has survived.

The hope is the probe could help us to better understand how the Sun works.

Dr Nicola Fox, head of science at Nasa, told BBC News: “For centuries, people have studied the Sun, but you don’t experience the atmosphere of a place until you actually go visit it.

“And so we can’t really experience the atmosphere of our star unless we fly through it.”

Parker Solar Probe launched in 2018, heading to the centre of our Solar System.It has already swept past the Sun 21 times, getting ever nearer, but the Christmas Eve visit is record-breaking.

At its closest approach, the probe is 3.8 million miles (6.2 million km) from our star’s surface.

This might not sound that close, but Nasa’s Nicola Fox puts it into perspective: “We are 93 million miles away from the Sun, so if I put the Sun and the Earth one metre apart, Parker Solar Probe is four centimetres from the Sun – so that’s close.”

The probe will have to endure temperatures of 1,400C and radiation that could frazzle the onboard electronics.

It’s protected by a 11.5cm (4.5 inches) thick carbon-composite shield but the spacecraft’s tactic is to get in and out fast.

In fact, it will be moving faster than any human made object, hurtling at 430,000mph – the equivalent of flying from London to New York in less than 30 seconds.

So why go to all this effort to “touch” the Sun?Scientists hope that as the spacecraft passes through our star’s outer atmosphere – its corona – it will solve a long standing mystery.

“The corona is really, really hot, and we have no idea why,” explains Dr Jenifer MIllard, an astronomer at Fifth Star Labs.

“The surface of the Sun is about 6,000C or so, but the corona, this tenuous outer atmosphere that you can see during solar eclipses, reaches millions of degrees – and that is further away from the Sun. So how is that atmosphere getting hotter?”

The mission should also help scientists to better understand solar wind – the constant stream of charged particles bursting out from the corona.

When these particles interact with the Earth’s magnetic field the sky lights up with dazzling auroras.

But this so called space weather can cause problems too, knocking out power-grids, electronics and communication systems.

“Understanding the Sun, its activity, space weather, the solar wind, is so important to our everyday lives on Earth,” says Dr Millard.

Nasa scientists face an anxious wait over Christmas while the spacecraft is out of touch with Earth.

Nicola Fox says that as soon as a signal is beamed back home, the team will text her a green heart to let her know the probe is OK.

She admits she’s nervous about the audacious attempt, but she has faith in the probe.

“I will worry about the spacecraft. But we really have designed it to withstand all of these brutal, brutal conditions. It’s a tough, tough little spacecraft.”

Butch Wilmore and Suni Williams were due to be back after just a week when they blasted off in June.

Their stay was extended to February next year because of technical issues with the experimental spacecraft, Starliner, built by Boeing.

Now – following a delay in launching a new capsule to the ISS – the pair won’t be back until late March or possibly April.

Nasa said the delay posed no risk to the astronauts.

In a statement Nasa stated: “The International Space Station recently received two resupply flights in November and is well-stocked with everything the crew needs, including food, water, clothing, and oxygen.

The resupply spacecraft also carried special items for the crew to celebrate the holidays aboard the orbital platform.”

Most space station missions last six months, with a few reaching a full year. So the extension to Butch and Suni’s already overdue stay in space should not be a problem, according to Dr Simeon Barber, from the Open University.

“I’m sure that they are already disappointed that they were going to miss Christmas back home with the folks. But this is only another two months on an already quite long mission, and I’m sure if you ask them, I’m sure they would tell you that the space station is where they love to be,” he said.

A new crew needs to launch before Wilmore and Williams can return and the next mission has been delayed by more than a month, according to the space agency.

Nasa’s next crew of four for the ISS was supposed to have been launched in February 2025. The capsule carrying that crew was due to be the one bringing Butch and Sunni home, as well as NASA astronauts Nick Hague and Roscosmos cosmonaut Aleksandr Gorbunov as part of the normal crew rotation.

But there has been a delay by the private sector firm SpaceX in preparing a brand-new Dragon capsule for the mission. That is now scheduled for flight readiness no earlier than late March.

Nasa said it considered using a different SpaceX capsule to fly up the replacement crew to keep the flights on schedule.

But it has now decided the best option is to wait for the new capsule to transport the next crew.