Before NASA’s Nancy Grace Roman Space Telescope arrives at its Lagrange 2 destination and begins performing years of observations, the cutting-edge observatory that started life as a National Reconnaissance Office (NRO) spy satellite will deploy and calibrate its suite of instruments.
These include a primary mirror, a Wide Field Array sensor, and a Coronograph Instrument technology demonstration designed to block out starlight to enable direct imaging of exoplanets.
Here is a quick peek at those instruments, which will help Roman image exoplanets, search for signs of dark matter and dark energy, and add huge amounts of raw scientific data that will keep scientists busy for years to come.
Nancy Grace Roman Space Telescope Instruments: The Primary Mirror
Designed and built at L3Harris Technologies in Rochester, New York. Roman’s primary is 7.9 feet across (2.4 meters). That is the same size as the one on NASA’s legacy Hubble Space Telescope.
However, NASA said Roman’s main mirror, which weighs 410 pounds (186 kilograms), is just one-fourth the weight of Hubble’s, “thanks to major improvements in technology.” They also noted that the weight difference was critical to the Lagrange Point 2 mission’s viability.
The Wide Field Instrument
While the main mirror will gather light, Roman’s Wide Field Instrument, or WFI, will gather digital images of the cosmos. According to NASA’s mission fact sheet, the 300-megapixel infrared camera “will give Roman the same angular resolution as Hubble but with a field of view at least 100 times larger.”
“Using this instrument, each Roman image will capture a patch of the sky bigger than the apparent size of a full moon,” the space agency explained.
Unlike many telescopes designed to focus incoming light toward a central point, NASA said Roman is designed to “see the most detail in a ring around the center.” That’s because the WFI’s millions of detectors are laid out in an arch shape. The space agency said this design “helps Roman capture a much wider area with equally sharp imaging and also lets both instruments operate simultaneously.”
Due to the hardware and software improvements, NASA said the WFI will gather data “up to 1,000 times faster than Hubble. When Roman’s five-year mission is completed, mission planners said they expect to gather “up to 20,000 terabytes (20 petabytes)” of data.
“Its sweeping cosmic surveys will help scientists discover new information about planets beyond our solar system, untangle mysteries like dark energy, and map how matter is structured and distributed throughout the cosmos,” the agency said when detailing WFI’s capabilities, adding that the mission’s “broad, crisp view will produce an extraordinary resource for a wide range of additional investigations.”
WFI’s Detectors
In a fact sheet, NASA said that the detector array at the heart of Roman’s WFI contains 18 “saltine cracker-sized” detectors. The space agency also said that each detector contains roughly 16.8 million tiny pixels (for a total of 300 million), “providing the mission with exquisite image resolution.”
Each cutting-edge detector comprises millions of photodiodes, which convert light into electrical current. NASA said this number of detectors, made from mercury-cadmium-telluride photodiodes (sensors that convert light into an electrical current), provides “one for each pixel.”
The space agency also noted that individual detectors are secured to a silicon electronics board that will help process the light signals using indium. Unlike steel, indium is a soft metal that has roughly the same consistency as chewing gum.
When they are working together, NASA said that 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.”
The Experimental Coronagraph
Astronomers typically infer the existence of exoplanets by the gravitational effects they exert on their host star or the dimming of the star’s light. However, directly imaging exoplanets has remained challenging because the star’s extremely bright light dwarfs the much dimmer light reflected by the planet. As a result, only a few of the largest, young “super Jupiters” have been directly imaged to date.
To block enough of a star’s light to capture an image of an exoplanet, Roman’s engineers have installed a novel Coronagraph. NASA describes this experimental device as “a system of optics, masks, self-flexing mirrors, and sensors designed to demonstrate the most advanced technologies ever flown in space for directly imaging planets around other stars.”
After its mid-flight deployment, Roman’s Coronagraph team will begin conducting a series of pre-planned observations. Mission planners said these observations “are scheduled for a total of three months spread across the mission’s first year-and-a-half of operations.”
“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,” the space agency explained.
The Roman team expects to release new images by early 2027. For detailed updates, follow the
Roman blog at science.nasa.gov/blogs/roman.
Christopher Plain is a Science Fiction and Fantasy novelist and has spent the last six years as Associate News Editor and Head Science Writer at The Debrief. Follow and connect with him on X, learn about his books at plainfiction.com, or email him at christopher@thedebrief.org.