The NASA-led Nancy Grace Roman Space Telescope is scheduled to launch on 30 August 2026 at 07:26 EDT, 12:26 BST and 13:26 CEST from NASA’s Kennedy Space Center in Florida, USA.
With its wide field of view and advanced optical design, Roman will conduct detailed surveys of the sky in visible and near-infrared light. The telescope is designed to investigate the nature of dark energy and dark matter while searching for new exoplanets.
“ESA is contributing essential hardware to Roman, including the spacecraft’s star trackers, batteries, detectors for the coronagraph instrument, and communications support through its deep-space ground station network,” said Bethan James, ESA’s Roman Project Scientist. “Through the Mission of Opportunity programme, Europe contributes scientific expertise, helping guide and maximise the mission’s scientific return.”
ESA will also support data downloads from Roman through a new 35-metre antenna at New Norcia, Australia.
Looking Back at the Early Universe
Roman will conduct fast and detailed infrared surveys of the sky, providing observations of the early Universe and its expansion over time.
“It will combine Hubble-quality imaging with a field of view more than 200 times larger, allowing it to study billions of stars, millions of galaxies, thousands of exoplanets, and vast regions of previously unexplored space,” James explained. “This will enable astronomers to address some of the biggest open questions in astrophysics, from the nature of dark energy to the abundance of planets throughout our Milky Way galaxy.”
Studying Dark Matter and Dark Energy
Around 25% of the Universe appears to consist of invisible dark matter, which can be observed through its effects on the apparent shapes of galaxies. Light from distant galaxies is bent and distorted by concentrations of dark matter, causing galaxies to appear slightly warped. This effect is known as weak gravitational lensing.
One of Roman’s primary tasks will be to survey approximately 12% of the sky high above the plane of the Milky Way to study this lensing effect across millions of distant galaxies. By measuring small changes in galaxy shapes, Roman will help astronomers map the distribution of ordinary matter and dark matter throughout the history of the Universe and investigate galaxy evolution.
Roman will also study how the Universe has expanded over time. The expansion appears to be accelerating, with dark energy proposed as a possible cause. Scientists estimate that dark energy accounts for about 70% of the Universe, although its nature remains unknown. Like ESA’s Euclid mission, Roman will use multiple methods to investigate dark energy and how it has changed over time.
One method will involve observing exploding stars known as supernovae, particularly Type Ia supernovae, in distant galaxies. Because these explosions reach a predictable peak brightness, astronomers can use them to measure cosmic distances and gain insight into the rate at which the Universe is expanding.
Roman will also study how galaxies cluster across time and space to examine the effects of dark energy. The telescope will investigate baryonic acoustic oscillations, which are imprints of sound waves that travelled through the early Universe.
As the Universe cooled, these ripples became fixed in place. Galaxy clusters later formed along the resulting structures. As the Universe expanded, the ripples stretched and the distances between surrounding galaxies increased. By studying the distribution of galaxies across cosmic distances, astronomers can investigate how the Universe expanded and gain further insight into dark energy.
Searching for Exoplanets
Roman will also search for exoplanets, including planetary systems that may resemble our own. Its deep and wide field of view will allow it to observe towards the centre of the Milky Way, monitoring the light from millions of stars and measuring changes in their brightness over time.
The telescope will monitor microlensing events that could reveal more than 1,200 new worlds. Roman is also expected to identify more than 100,000 transiting planets, which cause a reduction in their host stars’ brightness when they pass in front of them.
Its advanced Coronagraph Instrument will allow astronomers to directly image some exoplanets by blocking the light from their host stars. The instrument is designed to enable observations even when a planet is more than 100 million times fainter than its host star.
Observing Extreme Cosmic Objects
Roman’s sensitivity will also allow it to detect extreme cosmic events, including the formation of black holes following neutron-star mergers and tidal disruption events. The mission will observe active galaxies containing extremely bright quasars at their centres, as well as faint, distant quasars from the period of reionisation.
A Wide-Field Telescope in Space
The Roman Space Telescope has a 2.4-metre primary mirror and carries two main instruments: the Wide Field Instrument (WFI) and the Coronagraph Instrument.
The WFI is a 300-megapixel, multi-band visible and near-infrared camera designed to produce detailed images and highly sensitive spectroscopic data.
The Coronagraph Instrument is a high-performance technology demonstrator designed to block starlight and search for faint planets around their host stars. It could enable direct imaging of reflected starlight from Jupiter-sized exoplanets in Jupiter-like orbits around their stars.
“Whenever astronomy opens a new window on the Universe, history has shown that some of the most important discoveries are the ones we never anticipated,” James said. “With its unprecedented combination of depth, area and image quality, Roman has every opportunity to surprise us.”
