the door of the sun painter, with an arrow pointing to the small one "the thumb" added as a hack to cover the sun and only look at ambient light.

Solar Orbiter ‘Hack’ Allows Us to Pee Deeper into the Sun’s Atmosphere

Spacecraft equipment is unique and can take years to design, build, and test. But a last-minute hack in one of the instruments on ESA’s Solar Orbiter allowed the spacecraft to take difficult observations it otherwise would not have been able to take.

It’s all because of one astrologer and an instrument door.

ESA launched the Solar Orbiter in February 2020 to study the Sun’s inner heliosphere and polar regions in high resolution.

Every six months, it makes a close approach to the Sun, and studies this region repeatedly. The idea is to monitor the build-up of magnetic activity that is a precursor to solar flares and explosions. Within that, it has specific scientific goals.

The spacecraft carries instruments to achieve its objectives, and one of them is the Extreme Ultraviolet Imager (EUI.) Belgium contributed the EUI to the mission, and its task is to image the layers and structures in the Sun’s atmosphere from the chromosphere. in corona.

The EUI is actually three instruments in one: a full image of the Sun and two high-resolution telescopes. The Full Sun image shows the general shape of the Sun in coronal temperatures, and a pair of telescopes work in selected wavelength bands.

They reveal beautiful structures visible in the closest views of the Sun the spacecraft gets during its perihelion phase.

The challenge all Sun-observing spacecraft and instruments must overcome is the intense light emitted by the star. The strong light of the Sun hides important details. EUI is not. Telescopes often use coronagraphs to block strong light and make details in the Sun’s atmosphere visible.

During the final stages of building the instrument, a member of the Solar Orbiter team had a brilliant vision. The EUI has its own safety door to protect it during flight and when not in use. What if that door could be modified to improve image performance?

“It was really a blast,” said Frédéric Auchère, Institut d’Astrophysique Spatiale, Université Paris-Sud, and member of the EUI team.

“I had the idea to do it and see if it would work. It’s really a very simple modification to the device.”

The weight of the spacecraft was calculated accurately, but Auchère thought that a few grams would not matter. It adds a small, protruding ‘thumb’ to the door that can block the Sun panel during operation when the door is half-opened rather than fully open.

With the excess light from the Sun’s disk blocked by a thumb at the door, the EUI can effectively see the UV light from the surrounding corona, which is millions of times fainter than the disk. This means the instrument can see deep into the Sun’s atmosphere.

the door of the sun painter, with an arrow pointing to the small one "the thumb" added as a hack to cover the sun and only look at ambient light.
This picture shows a small “thumb” added to the door of the Full Sun Imager, part of the EUI. The occulting disk is held on the outside of the shutter by two support rods and is placed over the lens in this image. Rotating the lid on its axis (red cross) closes the door, and rotating it counterclockwise opens it. (Auchère et al. 2023)

The group calls this door the thumb and the half-open door as the magic mode of operation. It’s basically a new type of device. It combines a coronagraph and a camera in one device instead of requiring a separate coronagraph.

They have been testing the EUI in this way since 2021 and have published a paper in Astronomy and Astrophysics detailing the results. Frédéric Auchère, the astronomer who came up with the idea, is the lead author.

“We have shown that this works so well that you can now consider a new type of instrument that can image the Sun and the corona around it,” said Daniel Müller, ESA’s Solar Orbiter Project Scientist.

Auchère’s small addition to the EUI tool door solves the problem that plagues extreme UV images. The depth of the Sun’s atmosphere is beyond the reach of most of them, and various traditional coronagraphs often cover this region unnecessarily. But EUI’s new occulter can image more easily in this difficult area than before.

“Physics is changing there, magnetic structures are changing there, and we haven’t looked very well before. There must be secrets there that we can find now,” said David Berghmans, Royal Observatory of Belgium, and Principal Investigator of the EUI.

The little thumb added to the door was a late addition to the EUI kit. So it’s in the lowest form – the best. That means, among other limitations, it requires prolonged exposure to work. Some of the test images on the paper required 1000-second exposures.

But now that the performance of this design has been demonstrated, it can be improved on future devices for future operations.

“With small changes, the efficiency of the FSI-based chorograph can be increased by two orders of magnitude, which would allow images like the one shown here to be obtained in 10 seconds,” the authors wrote in their conclusion.

This means that EUV instruments may begin to replace visible light instruments and coronagraphs.

“Compared to the VL coronagraph, the EUV instrument offers several advantages,” the authors explain.

They wrote: “There is nothing behind spreading dust.” Not only is the stray light from the device easy to control, but it also “…makes the EUV Coronagraph unnecessary in terms of pointing accuracy and stability.”

It looks like our view of the Sun is about to advance.

This article was originally published by Universe Today. Read the first article.

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