The Nancy Grace Roman Space Telescope is a next-generation observatory that will peer through dust and across vast stretches of space and time to survey the infrared universe. The mission will help us solve some of the most profound mysteries in astrophysics, such as how the universe has evolved, its ultimate fate, and whether we are alone.

To make Roman’s sensitive measurements possible, the telescope will observe from a vantage point about 930,000 miles (1.5 million km) away from Earth in the direction opposite the Sun. At this special place in space, called the second Sun-Earth Lagrange point, or L2, gravitational forces balance to keep objects in steady orbits with very little assistance.

Roman Space Telescope satellite

Roman’s barrel-like shape will help block out unwanted light from the Sun, Earth, and Moon, and the spacecraft’s distant location will help keep the instruments cool. The thermal stability of an observatory at L2 will provide a ten-fold improvement beyond Hubble in much of the data Roman will gather.

The amount of detail these observations will reveal is directly related to the size of the telescope’s mirror, since a larger surface gathers more light. Roman’s primary mirror is 7.9 feet (2.4 meters) across. While it’s the same size as the Hubble Space Telescope’s main mirror, it is less than one-fourth the weight. Roman’s mirror weighs only 410 pounds (186 kilograms) thanks to major improvements in technology.

The primary mirror, in concert with other optics, will send light to Roman’s two science instruments – the Wide Field Instrument and Coronagraph.


Wide Field Instrument

The Wide Field Instrument is a 300-megapixel infrared camera that will allow scientists to look very far back in time. Seeing the universe in its early stages will help unravel how it has expanded throughout its history, which will hint at how it may continue to evolve.

Each Roman image will capture a patch of the sky bigger than the apparent size of a full Moon. Hubble’s widest exposures, taken with its Advanced Camera for Surveys, are nearly 100 times smaller. Over the first five years of observations, Roman will image over 50 times as much sky as Hubble covered in its first 30 years.

Roman’s large field of view will allow scientists to conduct extensive research that would otherwise be impractical. The wide field instrument will enable all of Roman’s surveys, which will explore:

  • Near-infrared surveys - a vast astrophysics treasure trove allowing the exploration of everything from nearby stars to distant galaxies
  • Dark energy – a mysterious antigravity pressure that accounts for about 68 percent of the total contents of the cosmos and may be changing as the universe evolves (or indicate a breakdown of Einstein’s general theory of relativity)
  • Dark matter – almost completely undetectable matter whose existence is implied to explain an excess of gravity measured in galaxies and galaxy clusters
  • Exoplanets – planets orbiting other stars, discovered primarily through a process called microlensing

Roman’s surveys will also pinpoint large numbers of elusive cosmic objects, enhancing the science return from other observatories. While telescopes such as Hubble and the James Webb Space Telescope will provide excellent in-depth observations of some of the most intriguing objects in the cosmos, their narrow fields of view make it difficult to find many to study.

Roman will dramatically increase the sample size of objects like quasars – extremely bright cores of distant active galaxies – and supernova explosions by capturing hundreds of thousands of galaxies in each image. Scientists will be able to identify especially interesting regions and use other observatories to take a closer look.


The coronagraph demonstrates technology that eliminates the glare of nearby stars and allows astronomers to directly image planets in orbit around them. It will be far more powerful than any other coronagraph ever flown, seeing planets that are almost a billion times fainter than their host star.

Results from the coronagraph, which is being built at NASA’s Jet Propulsion Laboratory, will demonstrate the technology that will enable future missions to observe and characterize rocky planets in the habitable zone of their star – the range of orbital distances where liquid water could potentially exist on a planet’s surface. Studying the physical properties of exoplanets that are more similar to Earth will take us a step closer to discovering habitable planets and possibly learning whether we are alone in the cosmos.

Once the technology is successfully demonstrated over the first 18 months of the mission, the coronagraph could become open to the scientific community. A Guest Observer program would invite a broader variety of observers to conduct experiments beyond the demonstration phase.

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