NASA Tool Gets Ready to Image Faraway Planets

At JPL on May 17, members of the Roman Coronagraph Instrument team use a crane t
At JPL on May 17, members of the Roman Coronagraph Instrument team use a crane to lift the top portion of the shipping container that the instrument was stored in for its journey to NASA’s Goddard Space Flight Center.
The deformable mirrors also help correct for imperfections in the Roman telescope’s other optics. Although they are too small to affect Roman’s other highly precise measurements, the imperfections can send stray starlight into the dark hole. Precise changes made to each deformable mirror’s shape, imperceptible to the naked eye, compensate for these imperfections.

"The flaws are so small and have such a minor effect that we had to do over 100 iterations to get it right," said Feng Zhao, deputy project manager for the Roman Coronagraph at JPL. "It’s kind of like when you go to see an optometrist and they put different lenses up and ask you, ’Is this one better’ How about this one?’ And the coronagraph performed even better than we’d hoped."

During the test, the readouts from the coronagraph’s camera show a doughnut-shaped region around the central star that slowly gets darker as the team directs more starlight away from it - hence the nickname "digging the dark hole." In space, an exoplanet lurking in this dark region would slowly appear as the instrument does its work with its deformable mirrors.

This graphic shows a test of the Roman Coronagraph Instrument that engineers call "digging the dark hole." At left, starlight leaks into the field of view when only fixed components are used. The middle and right images show more starlight being remov... Credit: NASA/JPL-Caltech"

Habitable Worlds

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 far easier than seeing the signal of the much fainter planet. In fact, fewer than 70 exoplanets have been directly imaged.

The planets that have been directly imaged to date aren’t like Earth: Most are much bigger, hotter, and typically farther from their stars. These features make them easier to detect but also less hospitable to life as we know it.

To look 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 for the kind of life found on Earth.

Developing the capabilities to directly image Earth-like planets will require intermediate steps like the Roman Coronagraph. At its maximum capability, it could image an exoplanet similar to Jupiter around a star like our Sun: a large, cool planet just outside the star’s habitable zone.

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

"The active components, like deformable mirrors, are essential if you want to achieve the goals of a mission like the Habitable Worlds Observatory," said JPL’s Ilya Poberezhskiy, the project systems engineer for the Roman Coronagraph. "The active nature of the Roman Coronagraph Instrument allows you to take ordinary optics to a different level. It makes the whole system more complex, but we couldn’t do these incredible things without it."

More About the Mission

The Nancy Grace Roman Space Telescope is managed at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, with participation by JPL and Caltech/IPAC in Southern California, the Space Telescope Science Institute in Baltimore, and a science team comprising scientists from various research institutions. The primary 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. Contributions were made by 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 Roman Science Support Center at Caltech/IPAC partners with JPL on data management for the Coronagraph and generating the instrument’s commands.