NASA is just days away from launching its next major space observatory.
The Nancy Grace Roman Space Telescope is set to lift off Aug. 30 aboard a SpaceX Falcon Heavy rocket from the Kennedy Space Center in Florida, heading for a spot roughly 930,000 miles (1.5 million kilometers) from Earth.
Unlike the James Webb Space Telescope, which trades panoramic views for a narrow field of view to peer deeply into small, specific patches of the sky, Roman is built for scale. Its field of view is 100 times larger than the Hubble Space Telescope‘s, meaning that in just the five years of its primary scheduled mission, it will capture more than 50 times as much sky as Hubble did in its first 30 years. With that kind of reach, Roman is expected to map roughly 20 billion stars, measure light from more than a billion galaxies, and turn up as many as 200,000 new exoplanets, according to NASA.
The instruments that will make this mission possible are tucked inside the observatory that looks, oddly enough, like a helicopter frozen mid-flight. With a nose-like front end housing the telescope, a pair of flat solar panels stretched out to either side and an antenna perched on top, the resemblance turns out to be a handy way to understand the key instruments that make Roman’s mission possible.
The telescope
Just like a helicopter’s nose holds critical navigation and visibility instruments, the front of Roman is home to the telescope, which gathers starlight and sends it to the science instruments behind.
At the heart of the telescope is a primary mirror 7.9 feet (2.4 meters) across, the same size as Hubble’s, while a smaller secondary mirror that’s just under 2 feet (0.5 meters) wide sits in its front. Both mirrors are kept cold, chilled to about 19 degrees Fahrenheit (-7 degrees Celsius), to prevent heat from the telescope itself from interfering with observations, according to NASA.
The telescope is also kept in optimal optical working condition with the help of the Deployable Aperture Cover, or DAC. Located at the very front of Roman, this hat-like shade pops open once the observatory reaches orbit, blocking stray light from entering the telescope barrel and helping protect the telescope’s sensitive optics throughout the mission.
Solar Array Sun Shield
A helicopter’s wings would look a lot like the flat panels stretched out on either side of Roman — except these panels are built for power, not lift.
The Solar Array Sun Shield, or SASS, consists of six solar panels. Two remain fixed to the spacecraft, while four more will unfold after Roman reaches orbit. Angled toward the sun, the array generates the electricity needed to power the observatory. It also throws shade over much of the spacecraft, helping keep the sensitive instruments at the low temperatures they need to operate.
The Wide Field Instrument
The workhorse of the mission is the Wide Field Instrument, of WFI, which is essentially a giant infrared camera with so much power and sensitivity that each image it takes captures a slice of sky bigger than the full moon as seen from Earth.
It can do this thanks to a mosaic of 18 detectors arranged in an arc, each packing more than 16 million pixels, which collect light from astronomical sources and convert it into electrical signals that can ultimately be turned into images. Because each image covers such an enormous field of view, scientists expect virtually every exposure to be packed with information.
The data will help scientists uncover new insights into planetary systems around other stars and map how matter is structured and distributed throughout the cosmos, offering fresh clues about the elusive nature of dark energy.
The Coronagraph
The coronagraph, nicknamed “Starglasses,” is designed to block the glare of stars so that planets orbiting them can come into view — including those far fainter than what scientists can currently see.
The instrument works by using two deformable mirrors equipped with thousands of tiny actuators. As starlight streams through the telescope, those actuators subtly reshape the mirrors in real time, correcting for imperfections in the telescope’s optics smaller than the width of a strand of DNA. Specialized masks work alongside the mirrors to suppress the way light bends around internal edges such that together, the system dramatically dims a star’s glare while allowing some of the much fainter light from an orbiting planet to shine through.
“I think of this as doing magic with physics,” Julie McEnery, Roman senior project scientist, said during a press conference in July. We’re taking advantage of the wave properties of light to cancel out the light from a star, so that we can image planets next to it.”
Scientists expect this capability to allow Roman to directly image Jupiter-size planets around sun-like stars, as well as capture sharp images of fledgling planetary systems still surrounded by the dusty disks where planets are forming.
As a bonus, the whole instrument also doubles as a proving ground for future missions, including NASA’s planned Habitable Worlds Observatory, which aims to directly image Earth-like planets around nearby stars.
High-Gain Antenna
Standing in for a helicopter’s rotor is the antenna dish on top of Roman. The roughly 6-foot (1.8-meter) dish high gain antenna, or HGA, is the observatory’s communications link to Earth, handling routine spacecraft data as well as high-speed science-data downloads. It is meant to transmit information home at speeds of up to 500 megabits per second.
Motorized gimbals allow the dish to swivel and remain locked onto ground stations even as Roman turns to look at different parts of the sky, ensuring that the enormous amounts of data collected by the telescope can make their way back to Earth.
If all goes to plan, once Roman is at its station in space, Lagrange Point 2 (L2) these components together will give the observatory both the breadth and precision needed for its ambitious survey of the universe, from mapping billions of galaxies to hunting for distant planets and probing one of cosmology’s biggest mysteries, dark energy.
