NASA’s upcoming SPHEREx mission will be able to scan the entire sky every six months and create a map of the cosmos unlike any before. Scheduled to launch no later than April 2025, it will probe what happened within the first second after the big bang, how galaxies form and evolve, and the prevalence of molecules critical to the formation of life, like water, locked away as ice in our galaxy. Achieving these goals will require cutting-edge technology, and NASA has approved final plans for all the observatory’s components.

“We’re at the transition from doing things with computer models to doing things with real hardware,” said Allen Farrington, SPHEREx project manager at NASA’s Jet Propulsion Laboratory in Southern California, which manages the mission. “The design for the spacecraft, as it stands, is confirmed. We have shown that it’s doable down to the smallest details. So now we can really start building and putting things together.”

To answer big questions about the universe, scientists need to look at the sky in different ways. Many telescopes, like NASA’s Hubble Space Telescope, are built to focus on individual stars, galaxies, or other cosmic objects, and to study them in detail. But SPHEREx (which stands for Spectro-Photometer for the History of the Universe, Epoch of Reionization and Ices Explorer) belongs to another class of space telescopes that quickly observe large portions of the sky, surveying many objects in a short period of time. SPHEREx will scan over 99% of the sky every six months; by contrast, Hubble has observed about 0.1% of the sky in more than 30 years of operations. Although survey telescopes like SPHEREx can’t see objects with the same level of detail as targeted observatories, they can answer questions about the typical properties of those objects throughout the universe.

For example, NASA’s recently launched James Webb Space Telescope will target individual exoplanets, measuring their size, temperature, weather patterns, and makeup. But do exoplanets, on average, form in environments that are conducive to life as we know it? With SPHEREx, scientists will measure the prevalence of life-sustaining materials like water that reside in icy dust grains in the galactic clouds from which new stars and their planetary systems are born. Astronomers believe the water in Earth’s oceans, thought to be essential to life starting on Earth, originally came from such interstellar material.

In order to pursue big-picture questions, the SPHEREx team first had to answer more practical ones, such as whether the instrument onboard could survive the environment in space, and if all its components could be packed together and operate as a system. Last month, the team’s final plans were approved by NASA, a step that the agency calls critical design review or CDR. This marks a major milestone for the mission on the way to launch.

For more information about the SPHEREx mission, visit https://www.jpl.nasa.gov/missions/spherex/.