European satellites launched in demo to create artificial solar eclipses

Two European satellites have rocketed into orbit on a mission to create artificial solar eclipses through formation flying in space.

Each fake eclipse should last six hours once operations begin next year, which is considerably longer than the few minutes of totality offered by a natural eclipse on Earth, and will allow for prolonged study of the sun’s corona, or outer atmosphere.

The launch took place from India.

“We are a very happy science team here,” the European Space Agency’s mission scientist Joe Zender said.

Billed as a tech demo, the two satellites will separate in a month or so and fly 492ft (150 metres) apart after reaching their destination high above Earth, lining up with the sun so that one spacecraft casts a shadow on the other.

This will require extreme precision, within just one millimetre, equivalent to a fingernail’s thickness, according to the European Space Agency (ESA). To maintain their position, the satellites will rely on GPS, star trackers, lasers and radio links, flying autonomously.

Each cube-shaped spacecraft is less than 5ft (1.5 metres) wide.

The shadow-casting satellite holds a disk to block the sun from the telescope on the other satellite. This disk will mimic the moon in a natural total solar eclipse, with the darkened satellite posing as Earth.

The launch has “huge scientific relevance” as well as testing high-precision formation flying, said ESA technology and engineering director Dietmar Pilz.

Scientists need the glaring face of the sun completely blocked to scrutinise the wispy crown-like corona encircling it, getting an especially good look close to the solar rim on this mission.

They are particularly interested to learn why the corona is hotter than the surface of the sun, and also want to better understand coronal mass ejections, eruptions of billions of tons of plasma with magnetic fields out into space.

The resulting geomagnetic storms can disrupt power and communication on Earth and in orbit. Such outbursts can also produce stunning auroras in unexpected places.

With a lopsided orbit stretching from 370 to 37,000 miles (600 to 60,000 kilometres) away, the satellites will take nearly 20 hours to circle the world. Six hours — at the farther end of certain orbits — will be spent generating an eclipse.

Other orbits will be strictly for formation flying experiments, according to the ESA.

The first eclipse results should be available in March.

Mr Zender said eclipses will be created at least twice a week, with six hours of totality each time for corona observations. The frequency will depend on solar activity and it will help scientists who currently travel across the world for three to five minutes of totality during the occasional eclipse.

The 210 million dollar (£165 million) mission, dubbed Proba-3, is aiming for at least 1,000 hours of “on demand” totality during its two-year operation. Once their job is done, both satellites will gradually drop lower until they burn up in the atmosphere, likely to be within five years.

Liftoff was delayed for a day by a last-minute issue with the back-up propulsion system of one of the satellites, crucial for precision formation flying. The ESA said engineers relied on a computer software fix.