The 1.2-m diameter main mirror of ESA's Euclid mission to unveil the dark universe, seen during assembly, integration and testing. Using this mirror, the spacecraft will map the 3D distribution of billions of galaxies up to 10 billion light years away—looking beyond the Milky Way galaxy to image around a third of the observable universe. By revealing the universe's large-scale structure, and its pattern of expansion, the mission will cast light on the mysterious dark energy and dark matter making up 95% of the cosmos.

All six of Euclid's Korsch configuration mirrors, plus the telescope itself—comprising more than 30 parts as well as the mirrors—as well as the more than 10 parts making up the mission's Near Infrared Spectrometer and Photometer and the optical bench that surrounds them are all made from the same material: not glass, but a ceramic only found naturally in space.

Silicon carbide (SiC) is one of the hardest materials known, used to make cutting tools, high-performance brakes and even bulletproof vests, while being much lighter than glass. It is similar to a metal in having high thermal conductivity but unlike metals can undergo extreme temperature shifts without deforming—making it very attractive for space-based astronomy.

Reusable launch vehicles have been a boon for the commercial space industry. By recovering and refurbishing the first stages of rockets, launch providers have dramatically reduced the cost of sending payloads and even crew to space. Beyond first-stage boosters, there are efforts to make rockets entirely reusable, from second stages to payload fairings. There are currently multiple strategies for booster recovery, including mid-air retrieval using helicopters and nets. Still, the favored method involves boosters returning to a landing pad under their own power (the boost-back and landing maneuver).

This strategy requires additional rocket propellant for the booster to land again, which comes at the expense of payload mass and performance for the ascent mission. As an alternative, researchers from the National Office Of Aerospace Studies And Research (ONERA) propose two new types of strategies that would allow boosters to return to their launch site.

The European Space Agency's (Esa) Euclid mission will launch into space on a Falcon9 rocket from SpaceX on July 1, or soon after. Many of us who have worked on it will be in Florida to watch the nail-biting event.

The mission is specifically designed to study the dark universe, probing both "dark matter" and "dark energy"—unknown substances thought to make up 95% of the energy density of the universe.

But it will also be able to test some strange, alternative models of gravity—potentially challenging Albert Einstein's great theory of general relativity.

Scientists have known about the existence of dark matter for nearly a century now. It was proposed after astronomers noted that galaxies in clusters had mysteriously high speeds. Such speeds should cause the clusters to evaporate unless there was some extra mass holding them together. As this matter wasn't shining in the same way as the visible galaxies, it was dubbed dark matter.

Gravitational lensing is a new tool to see this dark material. This effect relies on our understanding of general relativity.