Artist’s depiction of Euclid in space. Credit: ESA/C. Carreau

It’s almost become expected that many space telescopes and probes can have “extended missions.” Both Voyagers are still sending data back 40+ years after their five-year primary mission ended. But figuring out what to do with those spacecraft after their primary mission takes some negotiation. One such craft that will reach its end-of-mission in 2030 is Euclid, which is currently on a mission to map the “dark universe” of dark energy and dark matter. According to a new paper from Luigi “Rolly” Bedin of the Astronomical Institute of Padua, which is available on the arXiv preprint server, for its second act we could turn Euclid into the most powerful astrometric telescope ever made.

Currently, calculations give Euclid an extended life of about eight years, thanks to the additional fuel the craft has on board. That would more than double the six-year original mission, which is already well underway. With that additional time, Dr. Bedin suggests Euclid do something completely outlandish—do the exact same thing that it did for the first six-year mission.

Why on Earth would we use Euclid to do the same thing that it had just spent most of its lifetime completing? Because getting a second data point would allow us to see what moved in those six years—an astronomical value called “proper motion.” This is a calculation of how closer objects (such as stars in the Milky Way) move against a background of further objects (like distant galaxies) over time. But the key is that, in order to calculate proper motion, you need a very long time between data points to ensure the motion is significant enough to be calculated. According to Dr. Bedin, about six years should do the trick for Euclid.

Fraser interviews Dr. Maggie Lieu about Euclid’s primary mission.

Those who have been keeping a close eye on currently functioning astronomical observatories are probably shouting, “But what about Gaia?” at this point. That sounds like exactly what Gaia is designed to do—it is supposed to create a 3D map of our galaxy, and to do that it already calculates the proper motion of stars in the Milky Way by taking multiple pictures of them with large differences in their timestamps.

The problem is Gaia has a faintness limit. Euclid, which is designed to look for extraordinarily faint objects, can see things that are five to six orders of magnitude fainter than what Gaia can find. So by utilizing Euclid as another astrometric observatory, scientists could find billions of fainter and further away sources that could be found by Gaia alone, no matter how long its mission is. In fact, Gaia’s datasets already inform Euclid to help calibrate its sister telescope, and there would be some overlap in what they could both see astrometrically that would allow them to improve the accuracy estimates for objects Gaia has already observed by a factor of 10.

Fraser has been singing Gaia’s praises for a while—here’s why.

But Dr. Bedin points out that Euclid has even more potential for new science. He suggests using the remaining time of Euclid’s fuel reserve to add a third “epoch” of observations, but this time attempting to calculate the “parallax” of a more limited set of stars. In astronomical terms, calculating parallax would involve taking a picture about six months apart when the telescope is on opposite sides of the sun, essentially creating an effect like what we use for depth perception with our two eyes. But for astronomical objects, this would let us estimate how distant they are.

Dr. Bedin points out there are a bunch of engineering challenges to this last use case, as Euclid was never designed for that kind of operation, but he believes none of them are insurmountable—and that there are essentially none for simply running the whole observational campaign again to get proper motion since it is literally just rehashing what Euclid was already designed to do. Given the length of time still left on the space telescope’s primary mission, there is plenty of time to do whatever engineering calculations necessary to see if that ambitious “third epoch” of observations is feasible. But at the very least, the project managers for one of ESA’s flagship missions should consider Dr. Bedin’s suggestions—they seem a simple and elegant use of resources to unlock some truly interesting new science.

More information: Luigi “Rolly’’ Bedin, The case for an Astrometric Mission Extension of Euclid. Extending Gaia by 6 magnitudes with Euclid covering one-third of the sky, arXiv (2025). DOI: 10.48550/arxiv.2510.23694

Journal information: arXiv

Citation: Euclid has eight extra years of fuel—a scientist has a brilliant plan to use it (2025, November 10) retrieved 10 November 2025 from https://phys.org/news/2025-11-euclid-extra-years-fuel-scientist.html

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