An Eclipse Of The Sun For Six Hours Each Week? Europe’s Jaw-Dropping Plan To Fake Eclipses In Space Using Lasers
It’s nature’s greatest naked-eye sight—and it’s happening tomorrow—but the spectacle of a total solar eclipse could soon be faked in space almost at will if Europe’s Proba-3 mission goes to plan.
The world’s first “precision formation flying” mission, Proba-3 will see two satellites fly in formation to form an external coronagraph in space, with one satellite eclipsing the Sun to allow the second to study the otherwise invisible solar corona.
Remember that hallowed two minutes-or-so of totality during the “Great American Eclipse” of 2017? That’s nothing compared to the six hours Proba-3 will be capable of—twice each week!
“We can keep the spacecraft aligned with each other and the Sun—formation flying—which will can do for six hours at a time,” said Andrei Zhukov from the Royal Observatory of Brussels and Principal Investigator for the coronagraph instrument on the ESA Proba-3 mission. “We could have a six hour total solar eclipse every day, the only limitation being fuel—so we’re doing 1,000 hours of formation flying over the whole two-year mission,” said Zhukov.
That’s two six-hour total solar eclipses per week!
What is Proba-3?
A couple of technology demonstration spacecraft, the European Space Agency’s (ESA) mission is an attempt to perfect the art of “precise formation flying.”
It will take one image per minute for six hours during totality to produce short HD videos of the corona, but that can be increased to 30 seconds, or even two seconds, when there’s a coronal mass ejection (CME) on the Sun.
What will the two spacecraft do?
One will attempt to stay within the shadow of the other. Precise formation flying will be needed for the Coronagraph Spacecraft (CSC) spacecraft to artificially “occult” the Sun with a coronagraph while the other Occulter Spacecraft (OSC) spacecraft studies the Sun’s corona using an optical refractor telescope—and records the images.
The CSC will be about 144 meters behind the OSC and both spacecraft will have to maintain accurate positioning to just a few millimeters.
During the totality it creates it will be able to study the structure and dynamics of the Sun’s corona.
What is a total solar eclipse and why are they so rare?
During a total solar eclipse the Moon and the Sun align perfectly, with the former blocking out the latter. They can only occur at New Moon, when the Moon is between the Earth and the Sun.
Why we need to study the Sun’s corona
The hotter, outer part of the Sun’s atmosphere that’s usually hidden by its glare, corona is Latin for crown. Close-up studies of the corona are the only way for solar physicists to tease-out the inner workings of the Sun—and, hopefully, model it.
Only then can scientists begin to predict the Sun’s activity and the resulting “space weather” that can be so dangerous to our technological civilisation.
Why we need to create artificial solar eclipses
Trouble is, total solar eclipse aren’t common. There’s a one roughly one every 18 months, though since one total solar eclipse is not related to another, they can be as little as a year apart, and as much as two years. Totality is also only viewable from a very narrow path across the Earth’s surface, so getting a good view of the solar corona requires international travel to remote places and good luck with clear skies. Beside, most of them last only a couple of minutes.
“The trick is to observe the inner corona, and to do it in a way that would simulate a total solar eclipse,” said Zhukov. “Coronagraphs can make observations of the corona similar to an eclipse, but if you just take a telescope or coronagraph it produces a lot of stray light.”
How is this different to NASA’s SOHO?
NASA’s SOHO/LASCO spacecraft has two coronagraphs. However, it’s very close to the telescope. “It can only observe from 2.2 solar radii,” said Zhukov. “It can’t see the lowest part of the solar corona.” NASA’s STEREO mission gets that down to 1.4 solar radii and allows a lot fo stray light in.
During the fake eclipses, scientists should be able to observe the Sun’s inner corona with very low levels of stray light. The aim is to observe the corona down to 1.1 solar radius—so very close to the Sun’s surface—in the visible wavelength range.
“The further your occulter is from your telescope, the better,” said Zhukov. “We can observe the corona from very close to the solar surface—like during a natural total solar eclipse.”
Without Earth’s perturbing atmosphere it should look even better than what eclipse-chasers see from Earth.
Proba-3, Solar Orbiter and Parker Solar Probe
Proba-3 will be up in orbit while the ESA’s Solar Orbiter is taking high resolution image of the Sun from three-quarters of the way to the Sun from the Earth—26 million miles from the Sun. Solar Orbiter will also photograph the Sun’s poles for the first time and be able to make the first full observation of the solar wind.
Meanwhile, NASA’s Parker Solar Probe is making observations of the outer corona of the Sun and will get to just four million miles from the Sun in 2024.
How Proba-3 will achieve formation flying in space
Proba-3 will see a lot of new positioning tech tested, with the two spacecraft using GPS, star trackers and radio links between them to get roughly aligned, then a visual-based sensor that uses cameras and LED lights to get more closely aligned.
Finally the CSC will shine a laser on the OSC to achieve millimeter precision.
When will Proba-3 launch?
It’s due to launch in mid-2023 on a commercial PSLV-XL launcher from India. It will be placed into a high Earth orbit, between 330-373 miles/530-600 kilometers out, from where it takes about 19.7 hours to loop around the planet.
After about four months of commissioning observations will begin to be made—so we should expect “fake” total solar eclipses around the time of the next “Great American Eclipse.”
When is the next total solar eclipse?
The next total solar eclipse will take place just after dawn on Saturday, December 4, 2021 and be visible only from Antarctica. After that’s Western Australia, Timor Leste or West Papua on April 20, 2023.
Wishing you clear skies and wide eyes.