The Nancy Grace Roman Space Telescope is poised to become one of humanity’s most successful celestial observatories, but first NASA must complete its construction. The agency has taken a big step closer to this goal, having recently installed the Roman coronagraph instrument that will eventually merge with the telescope. Although the coronagraph is just a technology demonstration, the team hopes Roman will be able to see more. exoplanetspaving the way for more advanced planetary studies in the future.

The Roman Telescope is being built at NASA’s Goddard Space Flight Center, where the coronagraph recently arrived after being built at NASA’s Jet Propulsion Laboratory. This observatory is often compared to Hubble because it uses a similar 2.4 meter primary mirror. Although it is the same size as Hubble, the Roman telescope has a much sharper 300 MP wide-field instrument image sensor, and the mirror weighs less than a quarter. NASA says the Roman telescope will be able to provide Hubble-like sharpness over a field of view 100 times larger than the old telescope.

Hubble, the VLT, the new James Webb space telescope have sometimes succeeded in directly image gas giant exoplanetsbut only when the conditions are right. Even though we know that there are planets orbiting a star from a radial velocity or transit photometrythe star’s light makes it almost impossible to detect visually. This is where a coronagraph comes in handy.

A coronagraph is used to block direct light from a star, allowing fainter objects like exoplanets to be discerned. The Roman coronagraph’s masks and active mirrors could give the telescope the ability to see exoplanets orbiting distant stars. However, NASA still views this instrument as a stepping stone to more advanced planet-hunting equipment, such as the Habitable Worlds Observatory project.

“In order to get to where we want to be, we need the Roman coronagraph to demonstrate this technology,” said Rob Zellem, Roman Project Scientist. “We will apply these lessons learned to the next generation of NASA’s flagship missions that will be explicitly designed to search for Earth-like planets.”

A NASA technician works under the Instrument Carrier while recording the coronagraph. Credit: NASA/Sydney Rohde

The Roman coronagraph is now attached to the instrument holder, a grid-like structure that will eventually be integrated between the mirror and the spaceship bus (communication, propulsion and power). JPL designed a custom adapter to mount the coronagraph, which NASA describes as being the size and shape of a small grand piano. The adapter attaches to a mechanism called a horizontal integration tool, which allows technicians to align and connect the coronagraph to the instrument holder. The adapter and horizontal integration tool are then deleted.

The coronagraph is designed to operate at room temperature, so Goddard staff applied layers of insulation during installation. Next, the team will examine the Roman coronagraph to ensure it is properly aligned and secure, as even a small mismatch could render it useless. After completing work on the coronagraph, NASA plans to move on to integrating the main wide-field instrument. NASA currently hopes to launch the Roman Telescope in May 2027.