ESA's Proba-3 mission involves two satellites working together to observe the sun's atmosphere like never before. The mission will be launched in September and will use innovative technology to reduce light diffraction and enhance solar observation capabilities. Scientists will test Proba-3's instruments during the upcoming solar eclipse.
Flying in precise millimeter-level formation, the twin satellites that make up ESA's Proba-3 will accomplish a previously impossible mission in space: cast a precise shadow from one platform to another, blocking out the blazing sun in the process for long-lasting observations of the ghostly atmosphere around it.
Scientists who will use Proba-3 for observations will be able to see the satellite first-hand before it is launched together later this year. Members of the team will test the hardware developed for the mission during an actual terrestrial solar eclipse in the northern United States next April.
The two satellites are currently undergoing final integration at Redwire's facility near Antwerp, Belgium. They were visited by the Proba-3 Scientific Working Group, which consists of 45 solar physicists from Europe and around the world.
Many of these experts are regular visitors to global terrestrial eclipses, but they all look forward to the new perspective Proba-3 will open on the faint corona. Coronal mass ejections are massive bursts of charged particles that trigger solar storms and affect the speed of the solar wind, which is central to determining space weather.
Innovative design and technology
Joe Zender, Proba-3 project scientist at ESA, explained: "The satellite hardware is very noticeable at close range. I was particularly impressed by the fact that the camera head on the Coronagraph spacecraft is less than one meter away from the solar array. While the solar array relies on higher solar illumination, the camera must be kept in complete darkness, There can't be any stray light. This gives us a real sense of how precisely the small shadows cast by the Occulter are maintained. We also get a glimpse of the carefully machined edge of the Occulter spacecraft's disk - which is usually placed under a protective shield before launch. The curve of this edge is specially designed to minimize the spillage of diffracted sunlight that would otherwise affect imaging performance."
Also present was Russell Howard, a renowned American astrophysicist at the Johns Hopkins University Applied Physics Laboratory who played a leading role in NASA's Parker Solar Probe and the ESA-NASA SOHO mission: "This spacecraft is smaller than any I've been involved in - mainly because it's a single solar observation imager with two small "But the concept of this mission is very unique: placing an occluder 150 meters from the telescope to image very close to the edge of the sun, which has never been done before, as if the occluder spacecraft were a small moon. We will not see the edge of the prominence as close as during a terrestrial eclipse, but compared to the 5-10 minutes of a solar eclipse event, it will be very spectacular to see such images for several hours."
Mission Strategy and Challenges
Before traveling to the Royal Observatory of Belgium in Brussels, the team continued to discuss preparations for the mission, including plans for processing and distributing data, plans for joint observations with other space missions, and an assessment of the relative performance of Proba-3 compared with existing "coronagraphs" used for corona observations.
These telescopes use an internal occultation disk to obscure the solar disk. The problem is that light still spills over the edges of these inner occultation disks, known as diffraction, obscuring even the faintest relevant signals.
Damien Galano, ESA's Proba-3 project manager, pointed out: "The best way to reduce diffraction is to increase the distance between the occluder and the coronagraph, which is exactly what Proba-3 will do. For the first time, we will fly the coronagraph and the occluder on different platforms, with each orbit 150 meters apart, with a flight time of up to 6 hours, and use a series of positioning techniques to keep them in fixed positions."
By definition, comprehensive end-to-end testing of Proba-3 is impossible on Earth. But the meeting heard how the same set of filter wheels developed for Proba-3's ASPIICS (Association for Coronal Polar and Imaging Survey Spacecraft) could be used with parallel liquid crystal imaging technology to observe the solar eclipse over North America on April 8, 2024.
Scientific objectives and instruments
Qiao added: "The filter wheel allows you to observe the corona at different polarization angles, just like switching between different polarized sunglasses. The benefit of observing during an actual solar eclipse is that we don't need any occluders to understand exactly what we will get from Proba-3."
The scientific working group also discussed Proba-3's second instrument, the Digital Absolute Radiometer (DARA), which will measure total solar irradiance - how much energy the sun is releasing at any one time.
"Assuming that the energy output from the sun affects Earth's climate, we have to measure any changes as accurately as possible," Qiao points out.
Proba-3 will be launched by India's PSLV launch vehicle in September this year.
Compiled source: ScitechDaily