NASA plans to soon launch a new space telescope that will study a billion galaxies to track how the universe evolved over time, all courtesy of the US spy program and decades of research in detector technology. The telescope, known as the Nancy Grace Roman Space Telescope, was first developed by the National Reconnaissance Office, before being transferred to NASA in 2012. The intelligence agency no longer needed the hardware for its future missions, so it sent the unused telescope to NASA. The space agency spent more than a decade making modifications and aims to launch the telescope into space on August 30, 2026. Once in position, the telescope will take data that astronomers like me hope will help answer some of the field’s most vexing questions. Roman’s scientific goals A number of interesting discoveries can be expected from the new telescope because it was built to observe the universe and study the three-dimensional distribution of dark matter. Although scientists have not observed it directly before, dark matter produces invisible effects on objects in the universe, similar to those produced by visible matter. Likewise, Roman will see exploding stars called supernovae that allow astronomers to measure how fast the universe has been expanding. Those measurements will help astronomers gauge the universe’s varying expansion rate. Dark matter and dark energy, which have also not yet been directly observed, together are the source of the vast majority of the universe’s energy, but their physical nature is unknown. Closer to home, Roman will monitor small variations in the light of stars near the center of the Milky Way to infer the presence of rogue planets drifting between the stars. When a planet passes in front of a star, it briefly disturbs and magnifies the light from the star behind it, confirming its presence. Finally, Roman has a coronagraph instrument that will test the technology for future missions that plan to detect Earth-like planets around other stars. A coronagraph blocks most of a star’s light so astronomers can detect the much fainter planets orbiting it. For an Earth-like planet around a Sun-like star, the host star can be 10 billion times brighter than the planet. The Roman telescope’s coronagraph will help you study distant planets as they pass in front of a star. From Spy Telescope to Universe Exploration When NASA welcomed Roman, he turned a challenge about the telescope’s spy design into an opportunity. The telescope has a wide field of view, at least compared to most space telescopes made for astronomy. This means you can see a large swath of the sky at once. There is an opportunity: While telescopes like the Hubble Space Telescope see narrow fields very deeply, Roman will be able to see much larger fields. The Roman telescope’s wide field will allow it to see a much wider portion of the sky in a single image, compared to the Hubble Space Telescope. The Roman camera at NASA’s Goddard Space Flight Center has such a wide field because its origins as a spy telescope give it unusually fast optics. This means that it has a relatively short focal length (the distance between the mirror and the point where the light is focused) for the diameter of its mirror. Effectively, it can project a much larger portion of sky onto a fixed area of the telescope, called the focal plane. Its mirror is about the same diameter as Hubble’s, but it can capture an area about a hundred times larger per image. Big science, big detectors One modification NASA made included building a large focal plane, the light-gathering component of the telescope, made up of 18 wide-area near-infrared detectors. These detectors are almost identical to those on the James Webb Space Telescope, but have four times as many pixels. They will absorb infrared light, which has longer wavelengths than the light human eyes can see. But while each one on Webb is 4 megapixels, or 4 million pixels, Roman’s detectors are about 16 megapixels, bringing the total coverage of the 18 detectors to about 300 megapixels. The focal plane system of the Roman telescope is made up of 18 detectors. NASA/Chris Gunn, CC BY-NC These detectors are modern marvels in their own right and represent the culmination of a long heritage of new technology enabling new discoveries. I worked with colleagues in the early 2000s to advance the technology used in this type of detector, versions of which have been used at Hubble and Webb. We measured in the laboratory how the detectors performed in a simulated space environment. We needed to make sure they could still detect even tiny signals in space, which would allow the telescope to pick up light from very faint planets, stars and galaxies. We now see the fruits of those efforts in the beautiful images Webb has produced, including those of puzzling young galaxies in the early universe. I’m excited to see the images Roman will produce using the newest version of this technology. New technology and a legacy of discovery Astronomers are already eagerly awaiting the astronomical discoveries that Roman and his ultrasensitive infrared detectors will produce. But how can we have such high expectations for a space observatory that hasn’t even taken off from Earth? It’s because technology precedes discovery. Roman’s detectors are the latest version of a long story of scientific success. Countless Nobel Prize winners can be directly linked to the telescope. The team of physicists who inferred the existence of dark energy received the Nobel Prize in 2011. The observations they used came from new families of sensitive digital imaging detectors called charge-coupled devices, or CCDs, invented in the early 1970s. These devices helped astronomers measure the speed at which stars moved through space, supporting the idea that space is permeated with some unknown “dark” matter. An important validation of that Nobel Prize-winning research came from near-infrared detectors that used the same technology as Roman. Likewise, the Nobel Prize for the discovery of the supermassive black hole at the center of the Milky Way was awarded to researchers who used various infrared instruments in large ground-based telescopes. All of these telescopes had been equipped with newly available infrared detectors. In fact, this Nobel Prize highlights the impact of three technologies: infrared detectors, large telescopes and adaptive optics. Part of a continuous cycle People often think of scientific discovery as a eureka light bulb on the head of a brilliant scientist, but discovery rarely happens that way. More often, someone uses a new technology to observe something that, until then, had not been seen. Galileo used a telescope to observe the never-before-seen moons of Jupiter. Then the next technological iteration replaced the human eye with photographic plates in the 19th century, leading to the first sensitive all-sky surveys. These studies yielded a host of astronomical discoveries, including that the universe is expanding. An illustration of the Italian astronomer and physicist Galileo using a telescope, circa 1620. Hulton Archive/Getty Images In the 1970s, electronic detectors replaced photographic plates, increasing detector sensitivity by an order of magnitude. These advances were then transferred to infrared light, rather than just visible light, opening a new window on the universe and another wave of discoveries. And now it’s Roman’s turn. But Roman won’t be at the forefront for long, because NASA is already designing the next space telescope. The agency is developing the Habitable Worlds Observatory, a future space mission with the goal of directly imaging Earth-like planets around nearby stars and identifying signs of life in the universe. Let’s hope Roman has a smooth trip to space. Meanwhile, scientists are already planning the next generation of discoveries, one new detector at a time.
