NASA tool prepares to obtain images of distant planets

A technology demonstration on the Nancy Grace Roman Space Telescope will help increase the variety of distant planets that scientists can directly image.

The Roman Coronagraph Instrument on NASA’s Nancy Grace Roman Space Telescope will help pave the way in the search for habitable worlds outside our solar system by testing new tools that block starlight, revealing planets hidden by the glow of their stars mother. The technology demonstration was recently shipped from NASA’s Jet Propulsion Laboratory in Southern California to the agency’s Goddard Space Flight Center in Greenbelt, Maryland, where it joined the rest of the space observatory in preparation for launch in May 2027.

Before its cross-country trip, the Roman coronagraph underwent the most comprehensive test yet of its ability to block starlight: what engineers call “digging the dark hole.” In space, this process will allow astronomers to observe light directly from planets around other stars or exoplanets. Once demonstrated on Roman, similar technologies on a future mission could allow astronomers to use that light to identify chemicals in an exoplanet’s atmosphere, including those that potentially indicate the presence of life.

The Roman Coronagraphic Instrument aboard NASA’s Nancy Grace Roman Space Telescope will improve scientists’ ability to directly image planets around other stars. As the most powerful coronagraph ever flown in space, it will demonstrate new technologies that could be used in future missions such as NASA’s proposed Habitable Worlds Observatory. Credit: NASA/JPL-Caltech/GSFC

For the dark hole test, the team placed the coronagraph in a sealed chamber designed to simulate the cold, dark vacuum of space. Using lasers and special optics, they replicated the light of a star as it would be seen if observed by the Roman telescope. When light hits the coronagraph, the instrument uses small circular obscurations called masks to effectively block the star, like a car visor blocking the Sun or the Moon blocking the Sun during a total solar eclipse. This makes fainter objects near the star easier to see.

Coronagraphs with masks already fly in space, but they cannot detect an Earth-like exoplanet. From another star system, our home planet would appear about 10 billion times dimmer than the Sun, and the two are relatively close to each other. Therefore, trying to obtain a direct image of the Earth would be like trying to see a speck of bioluminescent algae next to a lighthouse 3,000 miles (about 5,000 kilometers) away. With previous coronagraphic technologies, even the glare from a masked star overwhelms an Earth-like planet.

The Roman coronagraph will demonstrate techniques that can remove more unwanted starlight than space coronagraphs of the past by using several moving components. These moving parts will make it the first “active” coronagraph to fly in space. His main tools are two deformable mirrors, each only 2 inches (5 centimeters) in diameter and backed by More than 2,000 small pistons that move up and down. The pistons work together to change the shape of the deformable mirrors so they can compensate for unwanted stray light spilling around the edges of the masks.

The deformable mirrors also help correct imperfections in other optics of the Roman telescope. Although they are too small to affect Roman’s other highly precise measurements, the imperfections can send stray starlight into the dark hole. The precise changes made to the shape of each deformable mirror, imperceptible to the naked eye, compensate for these imperfections.

“The defects are so small and have such a small effect that we had to do more than 100 iterations to get it right,” said Feng Zhao, deputy project manager for the Roman Coronagraph at JPL. “It’s like when you go to see an optometrist and they put different lenses on you and ask you, ‘Is this one better?’ What about this one?’ And the coronagraph worked even better than we expected.”

During the test, readings from the coronagraph camera show a doughnut-shaped region around the central star that slowly dims as the team directs more starlight away from it; hence the nickname “digging the dark hole.” In space, an exoplanet hidden in this dark region would slowly appear as the instrument does its work with its deformable mirrors.

How does the Roman coronagraph instrument work? This video shows how it removes unwanted starlight to reveal planets around other stars. Credit: NASA Goddard Space Flight Center

More than 5,000 planets have been discovered and confirmed around other stars in the last 30 years, but most have been detected indirectly, meaning their presence is inferred based on how they affect their parent star. Detecting these relative changes in the parent star is much easier than seeing the signal from the much fainter planet. In fact, fewer than 70 exoplanets have been directly imaged.

The planets that have been directly imaged to date are not like Earth: most are much larger, hotter, and usually farther from their stars. These characteristics make them easier to detect but also less hospitable to life as we know it.

To search for potentially habitable worlds, scientists need to image planets that are not only billions of times dimmer than their stars, but also orbit them at the right distance for liquid water to exist on the planet’s surface. a precursor to the type of life found. on earth.

Developing the ability to directly image Earth-like planets will require intermediate steps like the Roman coronagraph. At its maximum capacity, it could image a Jupiter-like exoplanet around a star like our Sun: a large, cold planet just outside the star’s habitable zone.

What NASA learns from the Roman Coronagraph will help pave the way for future missions designed to directly image Earth-sized planets orbiting the habitable zones of Sun-like stars. The agency’s concept for a future telescope called Habitable Worlds Observatory aims to image at least 25 Earth-like planets using an instrument that will build on what the Roman Coronagraph Instrument demonstrates in space.

“Active components, such as deformable mirrors, are essential if the goals of a mission like the Habitable Worlds Observatory are to be achieved,” said Ilya Poberezhskiy, systems engineer for JPL’s Roman Coronagraph project. “The active nature of the Roman coronagraph instrument allows ordinary optics to be taken to a different level. It makes the whole system more complex, but we couldn’t do these amazing things without it.”

The Nancy Grace Roman Space Telescope is managed at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, with participation from JPL and Caltech/IPAC in Southern California, the Space Telescope Science Institute in Baltimore, and a scientific team composed of scientists from various research institutions. Major industrial partners are BAE Space and Mission Systems in Boulder, Colorado; L3Harris Technologies in Melbourne, Florida; and Teledyne Scientific & Imaging in Thousand Oaks, California.

The Roman coronagraph instrument was designed and built at JPL, which manages the instrument for NASA. Contributing were ESA (the European Space Agency), JAXA (the Japanese Aerospace Exploration Agency), the French space agency CNES (Centre National d’Études Spatiales) and the Max Planck Institute for Astronomy in Germany. Caltech, in Pasadena, California, manages JPL for NASA. The Caltech/IPAC Roman Science Support Center partners with JPL on data management for the Coronagraph and instrument command generation.

For more information about the Roman telescope, visit:

Calla Cofield
Jet Propulsion Laboratory, Pasadena, California.
[email protected]

Claire Andreoli
NASA Goddard Space Flight Center, Greenbelt, Maryland.
[email protected]