How NASA turned a spy satellite into the Nancy Grace Roman Space Telescope | Scientific American
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New Issue: Orbital Catastrophe Ahead? Read Now<br>August 18, 2026<br>12 min read<br>Add Us On GoogleAdd SciAm<br>How NASA turned a spy satellite into its new dark energy telescope
NASA’s Nancy Grace Roman Space Telescope will soon launch to unravel the mysteries of dark energy and dark matter
By Jonathan O'Callaghan edited by Clara Moskowitz
The Nancy Grace Roman Space Telescope is prepared for launch in a clean room at the NASA Goddard Space Flight Center in Greenbelt, Md.
NASA/Chris Gunn
Alan Dressler stared in awe at the line of Hubble telescopes stretching out in front of him. It took NASA two decades to design and build its own Hubble Space Telescope, which transformed our understanding of the galaxies and stars after its 1990 launch. Now, standing inside a New York defense contractor’s clean room in 2012, Dressler faced an assembly line of Hubble clones. They weren’t astronomy telescopes. They were spy satellites of equal capability. And one of them was being given to NASA for free.<br>So begins the saga of the Nancy Grace Roman Space Telescope, which now sits in Florida, ready to launch on a SpaceX Falcon Heavy rocket within weeks. Roman will offer unprecedented knowledge of dark energy and dark matter, the mysterious components of the universe that explain our very existence. It will find more alien worlds outside our solar system than ever before, and it will also test a crucial technology that may one day reveal life on such worlds. It is, in the words of Julie McEnery of the NASA Goddard Space Flight Center and the mission’s senior project scientist, a telescope capable of “spectacular things.”<br>And the story of how Roman arrived at the launchpad is as amazing as the science it will perform. The observatory’s core was built to spy on America’s adversaries in a post-9/11 world. When that program collapsed, the National Reconnaissance Office (NRO) found itself with spare telescopes it no longer needed. Would NASA like any of them, officials asked? The space agency jumped at the offer.<br>On supporting science journalism<br>If you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.<br>Roman’s story is not only a tale of important science and unlikely interagency cooperation but also one of unusual efficiency. It is set to launch under budget and ahead of schedule, a feat almost unheard of for complex astronomical observatories. “When we get things right and have success stories like Nancy Grace Roman, let’s learn from some of the magic that created that outcome,” NASA administrator Jared Isaacman said in an April press conference.<br>Not only did the spacecraft begin its life in a bizarre twist of fate, but it also has evaded death on multiple occasions. It’s a telescope that for many reasons simply shouldn’t exist, yet here it stands, ready to cast its eye onto the heavens. And in a way, its ultimate mission isn’t so far off from what it was built for. It will still be spying for secrets, after all—but this time, for the secrets of the cosmos.<br>At the end of the millennium, astronomers made a Nobel Prize–winning discovery that upended modern cosmology. Looking at exploding stars called type Ia supernovae, they found an odd pattern—the supernovae farthest away were dimmer than expected. Scientists had known for decades that the universe was expanding, but this new finding pointed at something even more remarkable: the expansion was speeding up.<br>To explain this acceleration, astronomers came up with dark energy, an invisible force or pressure that was driving galaxies apart faster and faster and accounted for more than two thirds of the universe’s mass and energy. Albert Einstein had predicted the existence of such an effect in 1917—he invented a “cosmological constant” to explain why the universe was static. He nixed it, though, after the discovery in the 1920s that the universe was expanding. About a century later his prediction is back on the table as a possible reason for the accelerating expansion.<br>Not only did the spacecraft begin its life in a bizarre twist of fate, but it also has evaded death on multiple occasions.
Solving the mystery of dark energy will require better observations of supernovae across the universe, plus measurements of the shapes and positions of as many galaxies as possible, which scientists will use to study the cosmic structure dictated by the other component of the universe’s dark sector—dark matter. By the end of the 2000s understanding this dark universe had become one of the highest priorities in astrophysics, and in 2010 the National Academies of Sciences, Engineering, and Medicine...