ESA Prepares To Create Solar Eclipses To Study the Sun

Andrew Jones reports via IEEE Spectrum: The European Space Agency will launch a mission late this year to demonstrate precision formation flying in orbit to create artificial solar eclipses. In a press conference last week, the agency announced details of the mission and the technology the orbiters will use to pull off its exquisitely-choreographed maneuvers. ESA's Proba-3 (PRoject for On-Board Autonomy) consists of a pair of spacecraft: a 300-kilogram Coronagraph spacecraft and a 250-kilogram Occulter. The pair are now slated to launch on an Indian PSLV rocket in September and ultimately enter a highly elliptical, 600-by-60,530-kilometer orbit. The aim, the agency says, is to move the separate spacecraft to some 144 meters apart, with the Occulter, as a disc, blocking out the sun.

Achieving this formation will allow the Coronagraph to study our star's highly ionized, extremely hot atmosphere -- but also demonstrate the technology as a precursor for more ambitious, future, formation-flying endeavors. [...] ESA has science objectives for Proba-3, using observations made in space to study solar astrophysics without any intervention of the Earth's atmosphere. The agency's Association of Spacecraft for Polarimetric and Imaging Investigation of the Corona of the Sun (ASPIICS) coronagraph will help to discern why the solar corona is significantly hotter than the Sun itself. This could further our understanding of the Sun and assist solar weather predictions. However, it is the precision formation flying that Proba-3 aims to demonstrate which could help unlock future breakthroughs. [...]

Precisely-controlled Occulter spacecraft could be used with space telescopes to block light from a star in order to directly detect potential orbiting planets, while a constellation of spacecraft can, through interferometry, create large-scale observatories, achieving large apertures and long focal lengths than possible with large solo satellites. Further applications include Earth observation, space-based gravitational wave detection, and a range of missions in which two or more spacecraft need to interact, such as rendezvous, docking, and in-orbit servicing.

Haha

[backslashdot]

Can't wait for the anti-vaxxer flat-earther types like Marjorie Taylor Greene to start screaming "see, we told you they are creating these eclipses!" Reference: https://twitter.com/mtgreenee/... [twitter.com]

Re:

[christoban]

To do that, she'd have to admit space exists.

Re:

[Opportunist]

Just tell them what they should have been told a long time ago and what would maybe have nipped that in the bud:

"Yes dear, mommy is very proud of you. Now go play and let the grownups do their work".

Not an Eclipse

[Roger W Moore]

Well they asked for it by calling what they are doing an eclipse. An eclipse is defined as one celestial body obscuring the illumination from another. Similarly, putting one object into the shadow of another is not an eclipse unless those objects are planets or moons. This is why we don't call holding our hand up to shade our eyes or standing under a tree on a sunny day a solar eclipse.

Re:

[twms2h]

It would be funny, but unfortunately she acutally seems to believe this and is in a position of power so she can act on her believes.

I don't get why scientists need real eclipses

[Rosco P. Coltrane]

I understand that, by sheer coincidence, the moon has the right size and is currently at the right distance to mask the just enough of the sun and let only photons from the sun's upper atmosphere and corona through, making their observation easier.

But why is the moon needed? Why are even clever sun-blocking satellites needed? Do sun-blocking things need to be placed far away to observe the corona? Couldn't a beer coaster placed a few feet away from the telescope serve the same purpose?

I'm oversimplifying of course, but you get the idea.

The only reason I can think of is that the farther the sun-blocking object, the less fuzzy its boundary is when the observed through a telescope focused at infinity, making the moon truly useful when observing the thin boundary layer between the sun and the corona. Other than that, I don't see why a beer coaster - or perhaps a larger round object placed a bit farther out - wouldn't do the job.

Perhaps a reader who is better versed in solar observations can shed some light (pun not intended :)

Re:

[Anonymous Coward]

But why is the moon needed? Why are even clever sun-blocking satellites needed? Do sun-blocking things need to be placed far away to observe the corona? Couldn't a beer coaster placed a few feet away from the telescope serve the same purpose?

Well yes, of course. That's how literally all telescopes observing the sun currently do it.

I think you missed the detail that making an eclipse is not at all needed here.
The entire point, and the only point, of this mission is demonstrating their new precision formation flying process.

They are showing that their "occulter" spacecraft can turn and stop on a dime, so to speak.

Which is a pretty good visual actually. Imagine building a small flying RC type drone that is able to track where you are moving and

Re:

[Rosco P. Coltrane]

Well yes, of course. That's how literally all telescopes observing the sun currently do it.

Then my questions stands: why do teams of scientists chase lunar eclipses around the world at great expense? What's the added value of a real eclipse.

I think you missed the detail that making an eclipse is not at all needed here.

Not really, because I didn't in fact read the article :) My question about the value of eclipses for solar observation is tangentially related to the satellite thing, which doesn't really interest me at all.

Re:I don't get why scientists need real eclipses

[test321]

Eclipses have the advantage of no direct sunlight that scatters into the earth atmosphere, and scatters inside the coronograph telescope; it does scatter off the moon but this is so far away it does not matter. Explanation taken from https://www.washingtonpost.com... [washingtonpost.com]

Re:

[Rosco P. Coltrane]

Thanks!

Not Eclipses, Precision Formation

[Roger W Moore]

Then my questions stands: why do teams of scientists chase lunar eclipses around the world at great expense?

The _main_ point is to test precision positioning of satellites, not make shadows. For example, one very good scientific use of precision formations is that there are plans to have orbital gravitational wave detectors such as LISA [wikipedia.org]. This will require three satellites flying in a very precise formation creating a triangular interferometer with 2.5 million km arms. This should be sensitive to difference frequencies of gravitational waves than the current earth based detectors like LIGO.

Re:

[ceoyoyo]

A regular coronograph usually focuses the light onto an imaging plane, then puts an occulter on that plane to block the sunlight. Sometimes it's a mirror with a hole in it. Stars are much harder because their angular size is a millionth of the sun. Putting the occulter far away makes all the required tolerances bigger.

We can make occultation telescopes for stars now, but it requires sophisticated games manipulating the phase of the light, and it doesn't work as well as a straight up opaque block.

Re:

[backslashdot]

This is very very easy for you to try. Just go outside when the sun is out and align the sun up near a building such that a corner of the building blocks the sun out. Did you see a corona? There's your answer.

SCHWEET

[Shaitan]

Now they can deploy the formation to block the solar winds depleting the Martian atmosphere and we can terraform that biotch.

Gravitational Waves

[Roger W Moore]

I suspect the more likely plan is that this is a test of the precision formation technology they will need to build orbital gravitational wave detectors like LISA [wikipedia.org] that will be sensitive to a different region of the GW spectrum that current ground-based detectors.

Re:

[Shaitan]

I'd agree that is more likely but also far less likely to inspire funding dollars and there is no reason they have to choose just one.

Apollo-Soyuz Test Project (1975)

[Mirnotoriety]

Not the first time two spacecraft were used to create an artificial ellipse:

“The first international partnership in space wasn’t the International Space Station. It wasn’t even the Shuttle-Mir series of missions. It was the Apollo-Soyuz Test Project [nasa.gov], the first international human spaceflight.”