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Traditionally a coronagraph is something that blocks the bright disk of our Sun to make it easier to image the much dimmer corona. The first coronagraph is of course the Moon; during a solar eclipse it blocks the Sun and those who cautiously glance up at it during totality can see the corona.

Schemes to directly image exoplanet systems usually (always?) need at least some coronagraph-like functionality to block the star's light in order to image the planets that orbit it.

This usually happens within the telescope, often at an intermediate focal plane.

But space telescopes offer the possibility of the old-fashioned eclipsing coronagraph. The same way that our Moon just nicely blocks our Sun, and independent spacecraft several to several thousand kilometers away from a space telescope could eclipse the disk of another star, allowing for imaging of the exoplanet system around it.

Question: What will (likely) be the first separately-orbiting coronagraph to be deployed in space?


For an example of advanced coronagraphs integral to space telescopes, see

For an example of a separate coronagraph or "star shade", see

Results of a conventional coronagraph integrated within a space telescope, from How (the heck) does SOHO's SWAN camera image the entire 4π sr celestial sphere?

Below: From This answer to What is this white dot and strange line in SOHO image? Yes those are the Pleiades whizzing past the Sun!

GIF of images from SOHO; yes those are the Pleiades whizzing past the Sun!

screenshot from 4 Future Space Telescopes NASA wants to build

screenshot from 4 Future Space Telescopes NASA wants to build

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    $\begingroup$ It feels like I've asked an orbital-mechanics questions about what kinds of orbits would allow separate star shades and space telescopes to remain co-aligned with a target exoplanet system to within a few meters over thousands of kilometers, but I can't find it right now (neither here nor Astronomy SE) $\endgroup$
    – uhoh
    Aug 21 at 0:01
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While the complete answer you are looking for would no doubt discuss near (hopefully!) future space telescopes, the "spaceflight firsts" record may already have been claimed in 1975.

Soyuz-Apollo test project

https://history.nasa.gov/apollo/apsoyhist.html (emphasis mine)

Undocking and Separation: The Apollo and Soyuz spacecraft undocked at 95:42 GET (8:02 am EDT July 19, 1975). While the spacecraft were in station-keeping mode, the crews photographed them and the docking apparatus, transmitting the pictures live on TV to earth. The Apollo spacecraft then served as an occulting disk, blocking the sun from the Soyuz and simulating a solar eclipse the first man-made eclipse. Leonov and Kubasov photographed the solar corona as the Apollo backed away from the Soyuz and toward the sun. The two spacecraft then redocked at 8:34 am EDT with the Apollo maneuvering and the Soyuz docking system active while good quality TV was transmitted to earth. The second docking was not as smooth as the first because a slight misalignment of the two spacecraft caused both to pitch excessively at contact.

So the first separately-orbiting coronagraph would seem to be the last Apollo spacecraft launched, with the observing telescope being Soyuz 19.

I'm looking for those photos.

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    $\begingroup$ Cute, but it was hardy a "deployed coronagraph". $\endgroup$
    – uhoh
    Aug 30 at 6:00
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    $\begingroup$ @uhoh Then you would have to amend your definition: "Traditionally a coronagraph is something that blocks the bright disk of our Sun to make it easier to image the much dimmer corona." While the Moon is not deployed by humans, the Apollo spacecraft certainly was. $\endgroup$ Aug 30 at 10:50
  • $\begingroup$ No, I've posted a Stack Exchange question titled "What will (likely) be the first separately-orbiting coronagraph to be deployed in space?"and containing several paragraphs explaining just what I'm asking about just in case someone doesn't think the title is specific enough, and I'm looking forward to answers that address that as written. I understand that you'd like to pull out a few words and answer that instead, but right now I'm focused on answers to the entire question as written. $\endgroup$
    – uhoh
    Aug 30 at 16:51

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