Phocidae Borealis

Artist's concepts of NASA's Nancy Grace Roman Space Telescope (left) and NASA's Hubble Space Telescope (right), highlighting the 7.9-foot (2.4-meter) primary mirrors that sit in the heart of each observatory.

At the observatory’s heart sits a mirror that’s 7.9 feet (2.4 meters) across and 410 pounds (186 kilograms), or about the length and weight of a protoceratops! Roman’s primary mirror is the same size as the Hubble Space Telescope’s main mirror, but less than one-fourth the weight thanks to major improvements in technology.

Technicians installed Roman’s primary instrument, the Wide Field Instrument (pictured at left), in the fall of 2025.

The mission’s 300-megapixel infrared camera, called the Wide Field Instrument, is over 8 feet (about 2.5 meters) tall, which is about the length of a triceratops skull. It will give Roman the same angular resolution as Hubble while capturing an area of sky at least 100 times larger. The mission will gather data up to 1,000 times faster than Hubble.

Its sweeping cosmic surveys will help scientists discover new information about planets beyond our solar system, untangle mysteries like dark energy, and map how both normal matter and dark matter are structured and distributed throughout the universe. Casting such a wide, deep “net” into space will give astronomers plenty of cosmic bycatch as well; Roman’s crisp, panoramic views will offer practically limitless opportunities for astronomers to do all kinds of exciting science.

The Coronagraph Instrument was installed on Roman’s instrument carrier in October 2024.

Roman’s Coronagraph Instrument is about as wide (5.5 feet, or 1.7 meters) as a velociraptor is long. The Coronagraph is designed to demonstrate new technologies for directly imaging planets around other stars. It will block the glare from a star and make it possible for scientists to see the faint reflected light from planets in orbit around them.

The Coronagraph aims to photograph worlds and dusty disks around nearby stars in visible light to help us see giant worlds that are older, colder, and in closer orbits than the hot, young super-Jupiters direct imaging has mainly revealed so far.

This photo shows Roman’s 18 detectors, which are the heart of the mission’s 300-megapixel camera.

Roman’s “eyes,” 18 saltine cracker-sized detectors in its primary instrument, are each about as tall as an allosaurus tooth. They each have about 16.8 million tiny pixels for a total of 300 million, which means Roman’s images will be super hi-res. Each detector is made of millions of mercury-cadmium-telluride photodiodes (sensors that convert light into an electrical current), one for each pixel.

Principal technician Billy Keim installs a cover plate over Roman’s detectors.

The detectors are secured to a silicon electronics board that will help process the light signals using indium, a soft metal that has roughly the same consistency as chewing gum. Together, these ultra-sensitive detectors can capture vast areas of sky in a single shot while still revealing incredibly fine detail, allowing Roman to map the cosmos faster and more precisely than ever before.

Roman’s electrical wiring was installed on the spacecraft flight structure in the summer of 2023.

There are 1,000 pounds, or 450 kilograms, (the weight of a pachycephalosaurus) of electrical cabling, made up of about 32,000 wires and 900 connectors, laced throughout the observatory. If the wires were laid out end-to-end they would span 45 miles — nearly enough to trace the entire perimeter fence in the imagined Jurassic Park! Functioning as the Roman’s “nervous system,” the cabling enables different parts of the observatory to communicate with one another, provides power, and helps the central computer monitor the observatory’s function.

The Roman observatory was fully integrated on Nov. 25, 2025, at NASA’s Goddard Space Flight Center in Greenbelt, Md.

Roman’s six solar panels each measure about 7 by 10 feet (2 by 3 meters), collectively giving Roman a “wingspan” similar to a pteranodon’s! Together, they will provide a total of 4 kilowatts of power, which is about the same rate that a modest rooftop solar panel system produces during the daytime.

Over the course of two days in June 2025, eight technicians installed Roman’s solar panels onto the outer portion of the observatory.

The panels are covered in a total of 3,902 solar cells that will convert sunlight directly into electricity much like plants convert sunlight to chemical energy. When tiny bits of light, called photons, strike the cells, some of their energy transfers to electrons within the material. This jolt excites the electrons, which start moving more or jump to higher energy levels. In a solar cell, excited electrons create electricity by breaking free and moving through a circuit, sort of like water flowing through a pipe. The panels are designed to channel that energy to power the observatory.

Roman’s high-gain antenna will provide the primary communication link between the spacecraft and the ground.

The radio dish that will send data across a million miles of intervening space back to Earth spans 5.6 feet (1.7 meters) in diameter. That’s about the size of the largest known dinosaur footprints, yet it weighs only 24 pounds (10.9 kilograms). Its large size will help Roman send radio signals across a million miles of intervening space to Earth. The dual-band antenna will use one frequency band to receive commands and send back information about the spacecraft’s health and location. It will use another frequency band to transmit a deluge of data at up to 500 megabits per second.

We’re only a few months out from launch, and so close to a completely new understanding of the universe and our place within it. Follow along with Roman’s road to launch at nasa.gov/roman, and virtually tour the Roman observatory here.