The Nancy Grace Roman Space Telescope, NASA’s latest and greatest cosmic cartographer, is ready to fly. Named after the agency’s first chief astronomer, the $4.3 billion telescope will use its sharp infrared vision to capture sweeping views of the stars.

Roman is expected to chart billions of galaxies, hundreds of black holes and dusty planet-forming disks, as well as a hundred thousand new worlds beyond our solar system. The telescope promises a cosmic panorama so wide and so crisp that it would take over half a million high-definition TVs to display in full.

Its data will be used to probe the mysterious nature of dark matter, an invisible substance shaping the structure of our universe, and dark energy, a repulsive force threatening to rip the cosmos apart. Astronomers will also use Roman to complete the census of planets across the Milky Way. Part of the appeal, however, lies in the unexpected.

In Roman’s treasure trove of data, who knows what scientists might find.

Where is the launch and how can I watch it?

Roman is expected to lift off from the Kennedy Space Center in Florida as early as 7:26 a.m. Eastern time on Sunday. SpaceX will launch the telescope on a Falcon Heavy rocket and is providing a livestream of the flight on its website and social media. You can also watch NASA’s livestream.

In a news conference on Saturday morning, an official from the U.S. Space Force said that the weather forecast for the launch was 50 percent favorable. Should weather or another reason prevent liftoff on Sunday, a backup launch opportunity is scheduled for Monday at 7:22 a.m., with another window planned for Tuesday morning.

How will Roman chart the universe?

The telescope’s primary instrument is a 300-megapixel infrared camera that can capture a piece of sky wider than the apparent size of a full moon. Astronomers will stitch the images together to create maps of what the universe looked like as far back as when it was only a few hundred million years old.

Within this data, scientists will look for different kinds of gravitational lensing, an effect that occurs when matter distorts the light radiating from an object behind it. The presence of dark matter can be inferred by the way its gravity bends the light of more distant galaxies in the background.

Charting the structure and distribution of dark matter across cosmic time will also offer insight into how the universe has expanded over billions of years. This will help scientists better understand the puzzling behavior of dark energy, which is pushing the cosmos outward at an accelerating rate.

There are two other ways Roman can shed light on dark energy. The telescope will detect a certain type of supernova that explodes with a signature amount of light; observing the apparent brightness and distance of these explosions will provide a second measurement of the universe’s expansion. Studying the ever-widening separation of galaxies in different eras of cosmic time offers a third.

What about exoplanets?

According to NASA, astronomers have discovered 6,354 exoplanets. With Roman, they expect to push that number to more than 100,000.

One of Roman’s planet-finding techniques relies on microlensing, a type of gravitational lensing that happens on a smaller scale. Planets orbiting stars in the foreground can create brief boosts in the light radiating from stars in the background. The telescope can also capture planets crossing in front of their own stars, which cause a temporary dip in brightness.

Roman will use its infrared camera to collect evidence of new worlds. But it has a second instrument called a coronagraph that will photograph already discovered exoplanets. This will demonstrate a technique that may one day be used to hunt for faraway Earths with NASA’s proposed Habitable Worlds Observatory.

How does Roman compare to other space telescopes?

The Hubble Space Telescope, which NASA launched in 1990 and which is still collecting data, transformed the way astronomers saw the universe. Roman has the same-size mirror and about the same infrared resolution as the Hubble, which collects mostly visible light. But the new telescope’s gaze is at least a hundred times wider and up to a thousand times faster: In one month, Roman will complete a survey of the sky that could take Hubble a century.

The James Webb Space Telescope, launched by NASA in 2021 and, like Roman, primarily collects infrared light. But what Roman offers in breadth, the Webb makes up for in depth. It peers back to nearly the beginning of time and captures breathtaking scenes of the infant universe as it appeared a few million years after the Big Bang.

And then there is Euclid, a telescope launched by the European Space Agency in 2023. Euclid is perhaps most similar to Roman in that it is also designed to survey broad strokes of the universe to study dark energy and dark matter. It scans wider than Roman will, charting about a third of the sky, but with less precision and depth than Roman, which will image only about 12 percent.

Who is Nancy Grace Roman?

NASA recruited Nancy Grace Roman as its first chief astronomer six months after its founding. She was the first woman executive at NASA, and she played a pivotal role in securing federal funding for the Hubble Space Telescope. Dr. Roman is often referred to as the “mother of Hubble.”

But her influence spans beyond NASA’s first great space observatory. Dr. Roman was integral to building out the agency’s space astronomy program at a time when it was largely focused on landing men on the moon. Decades later, that legacy has grown into a rich collection of discoveries about our universe.

Dr. Roman died in 2018, and NASA dedicated the space telescope in her honor two years later.

The Roman Space Telescope is the second major U.S.-funded observatory to be named after a woman. The first was the Vera C. Rubin Observatory in Chile, named after the astronomer whose work confirmed the existence of dark matter.

Where is Roman going?

After liftoff, Roman will travel nearly a million miles from Earth to orbit around a location known as the second Lagrange point, or L2. The gravitational pulls from the sun and Earth cancel out at L2, allowing spacecraft at this point to save fuel.

L2 is a strategic location for Roman because it is far from the sun, moon and Earth, which emit infrared light that can interfere with more distant cosmic signals. It also allows Roman to survey wide swaths of sky without the moon or Earth blocking its view.

It will take about 100 days for Roman to arrive at L2 and begin science observations. Roman’s primary mission length is five years, though NASA has equipped the telescope with enough fuel to last a decade.