NASA has taken a new major step in preparations for the next generation of space astronomy: construction of the Nancy Grace Roman Space Telescope is fully complete, an ambitious infrared observatory that is scheduled to head towards orbit around the L2 point of the Earth-Sun system in the second half of this decade. In the largest clean room at NASA's Goddard Space Flight Center in Greenbelt, Maryland, technicians physically connected the two main segments of the observatory on November 25, 2025 – the inner “telescope” part and the outer part with systems for power, communications, and flight control.

This marks the completion of the construction of the entire Roman Space Telescope, moving the mission from the assembly phase to the final testing phase. This is a key moment for NASA's portfolio of large astrophysics missions: Roman is intended to complement the work of the Hubble and James Webb telescopes and answer some of the deepest questions about the origin of the universe, the role of dark energy and dark matter, and the frequency of planetary systems like ours.

A New “Big View” of the Universe

The Nancy Grace Roman Space Telescope, which was long developed under the earlier name WFIRST (Wide-Field Infrared Survey Telescope), is conceived as an infrared observatory with an extremely wide field of view. Its primary mirror is 2.4 meters in diameter – the same as Hubble's – but the combination of optics and detectors allows it to “capture” an area of the sky about one hundred times larger than the field of view of Hubble's camera in a single shot. The goal is for the telescope to conduct systematic sky surveys and collect massive amounts of data on galaxies, stars, black holes, and exoplanets during its primary five-year mission.

Roman will be placed in a halo orbit around the L2 point, approximately 1.5 million kilometers from Earth, where the gravitational pull of the Earth and Sun and the orbital motion of the telescope balance in a way that allows for stable observation of the universe with minimal thermal and geometric disturbances. Such a position has already proven ideal for scientific missions like the James Webb Telescope, as it offers a stable environment, good protection from sunlight, and a relatively simple observation schedule.

According to NASA's plans, Roman should be ready for launch no later than May 2027, with the possibility of an earlier launch as soon as the fall of 2026. The contract provides for a launch on a SpaceX Falcon Heavy rocket from launch pad LC-39A at the Kennedy Space Center in Florida. After final tests at the Goddard center, the observatory should be transported to Florida during the summer of 2026, where final flight preparations and integration with the rocket will follow.

What Was Completed on November 25, 2025?

The construction of the Roman Space Telescope took place over years in multiple parallel streams – the telescope assembly (optical mirror, supports, and precision pointing systems) and the spacecraft carrying the telescope (the so-called “spacecraft bus”, with power, communications, propulsion, and computer systems) were developed separately. The final mating of these two large segments created a fully integrated observatory, built to full size and in the configuration in which it will be launched.

In practical terms, the team in the clean room carefully lifted and aligned the telescope module and connected it to the load-bearing structures of the spacecraft. every mechanical joint and cable connection underwent detailed checks, because after launch there is no longer physical access to the system. The connection lasted several hours, but behind that operation lie years of design, test models, prototypes, and individual subsystem testing.

NASA emphasizes that the completion of construction is more than a symbolic step: only at this stage is it possible to conduct comprehensive tests of the observatory's behavior in conditions similar to those in space. Thermal-vacuum tests, vibration tests simulating launch loads, and a long series of checks on optical alignment, instrument functionality, and communication with the control center will follow.

The Road to Launch: Testing Under Extreme Conditions

In the coming months, Roman will undergo, as NASA likes to say, “torture testing” – a series of rigorous checks without which such a complex mission must not go into space. In thermal-vacuum chambers, the telescope and spacecraft are exposed to temperatures and conditions similar to those in deep space, while the instruments must simultaneously operate within designed parameters. Engineers are particularly interested in the structure's reactions to sudden temperature changes, as any microscopic shift can affect focus and optical performance.

Another key set of tests includes vibration tests and acoustic testing. The telescope is mounted on special tables shaken by powerful equipment, simulating the vibrations and loads that occur during launch on a Falcon Heavy rocket. Acoustic testing involves exposure to very strong sound waves, which imitate the noise of rocket engines and airflow around the rocket. Only when the observatory passes all these checks without damage and while preserving precise optics and mechanics can the mission get the “green light” for delivery to the launch site.

Additionally, the team must verify the complete electronic and software architecture. Every data path between instruments, memory, communication units, and orientation systems is tested in various scenarios – from nominal observation campaigns to simulated anomalies. The goal is to discover any potential “bug” while it is still possible to intervene, instead of the problem emerging only in space, where every intervention is limited or impossible.

Two Key Instruments: Wide Field Camera and Coronagraph

Roman will carry two main scientific instruments into orbit: the Wide Field Instrument (WFI) and the Coronagraph Instrument, with the second formally designated as a demonstration of new technologies, and the first as the workhorse of the mission.

The Wide Field Instrument is a camera with a resolution of approximately 300 megapixels, composed of 18 highly sensitive detectors covering the visible and near-infrared range from about 0.48 to 2.3 micrometers. Each individual shot will be wide enough to encompass an area of the sky larger than the apparent size of the full Moon. Compared to Hubble's classic cameras, Roman will be able to survey the sky about one hundred times faster, because it captures a far larger field of view in a single frame with comparable image sharpness.

Thanks to this combination of width and resolution, during the five-year primary mission, it is expected that Roman will collect about 20,000 terabytes of data, or 20 petabytes. This “data deluge” should contain information on billions of galaxies, hundreds of millions of stars, and at least 100,000 exoplanets discovered by various methods. The volume of data is precisely crucial for statistical analyses with which astronomers want to examine how the universe is expanding, how the structure of galaxies has changed through cosmic time, and how common planetary systems of different types are.

The second instrument, the Coronagraph, represents a bold technological leap. It is a complex assembly of masks, prisms, filters, detectors, and deformable mirrors that should “extinguish” the glare of stars in visible and near-infrared light and allow direct imaging of the very faint light of their planets and surrounding dust disks. For success, it is necessary to suppress the light of the parent star by up to a billion times relative to the surroundings, which represents an extreme technological challenge.

The Coronagraph on Roman is officially a technology demonstrator: its main task is not the mass production of scientific results, but the proof that such extreme suppression of starlight is feasible in space. Success would open the door to future, even larger telescopes dedicated to direct imaging of potentially habitable planets around stars close to the Sun. But even as a demonstrator, the Coronagraph should collect valuable data on giant exoplanets and structures of dusty disks around nearby stars.

Three Monumental Surveys of the Universe

Most of the time during the primary mission – about 75% – will be dedicated to three large scientific programs, or sky surveys, which are carefully designed to answer key questions of cosmology and planetary science.

The first of them, the High-Latitude Wide-Area Survey, is focused on a wide area of the sky at relatively high galactic latitudes, where the influence of our galaxy on observations is somewhat smaller. Using a combination of deep images and spectroscopy, astronomers will track the distribution of galaxies and their clustering across a large range of distances, or through different cosmic eras. Based on these data, it is possible to reconstruct how the “web” of dark matter developed over time on a large scale, and how dark energy affects the expansion of the universe.

The second key program, the High-Latitude Time-Domain Survey, also focuses on areas outside the plane of our galaxy, but with an emphasis on variability. Roman will image the same area of the sky multiple times over years, so that the appearance and evolution of supernovae, variable stars, and other transient phenomena can be tracked. The role of these observations is particularly important in the study of dark energy: Type Ia supernovae serve as “standard candles” for measuring distance, and the combination of their brightness and redshift allows for precise mapping of the history of the universe's expansion.

The third large program, the Galactic Bulge Time-Domain Survey, turns its gaze toward the interior of our galaxy – toward the dense central “bulge” of the Milky Way. There, the density of stars is extremely high, which creates ideal conditions for observing gravitational microlensing. When an object – a star, planet, or compact remnant like a black hole – passes almost exactly in front of a background star, its gravity temporarily amplifies the light of that background star. This short-lived increase in brightness carries information about the object that caused the lensing.

Roman's microlensing observations should reveal planets located in the habitable zones of their stars, but also colder, more distant worlds like Jupiter, Saturn, or Uranus. Additionally, the same method will be sensitive to “rogue planets” – objects of planetary mass that are not gravitationally bound to a star at all and wander freely through the galaxy. Microlensing should also reveal isolated black holes and neutron stars, which normally do not radiate enough to be directly visible, but their gravitational influence on background stars leaves a clear signature.

More Than One Hundred Thousand New Worlds

One of the most exciting aspects of the Roman mission is the potential hunt for exoplanets. The combination of transit observations (when a planet passes in front of its star and slightly dims its light) and microlensing should lead to the discovery of at least about 100,000 new planets in the first five years of operation. Unlike many earlier missions, which were particularly sensitive to planets in close orbits around stars, Roman's microlensing observations will complete the picture of colder and more distant worlds, including objects of mass comparable to Earth or even smaller.

In this way, Roman will significantly supplement the statistics built by missions like Kepler and TESS. While Kepler showed that planets are common and that many stars have compact systems of “super-Earths” and mini-Neptunes, Roman should clarify how common analogs of our Solar System are, with planets arranged at greater distances and in colder regions. In combination with other data, astronomers will be able to ask more precise questions about how typical or exceptional our system is.

The Coronagraph, although primarily a technological demonstrator, should also contribute with direct images of giant exoplanets around relatively nearby stars. Such images allow for the study of the atmosphere, temperature, and clouds of those planets, especially if combined with spectroscopy. Although Roman will not be specialized for detailed study of potentially habitable worlds like the future Habitable Worlds Observatory, every advance in direct imaging and characterization of exoplanets is considered a key step towards the long-term quest to identify planets with conditions similar to Earth's.

Dark Energy, Dark Matter, and the Structure of the Universe

Besides hunting for planets, Roman is fundamentally designed as a cosmological mission. One of the great questions that emerged at the end of the 20th century is why the expansion of the universe is accelerating. This acceleration is attributed to a still poorly understood component known as dark energy. Roman's wide-field, deep observations of galaxies, weak gravitational lensing (tiny distortions of galaxy shapes caused by dark matter in the intervening space), and supernovae should enable independent measures of the expansion of the universe and the growth of cosmic structures through different periods of cosmic history.

Roman will use three complementary techniques: tracking baryon acoustic oscillations in the distribution of galaxies, weak gravitational lensing statistics, and precise distance measurements using Type Ia supernovae. By combining this data, scientists will be able to verify whether Einstein's general theory of relativity holds even on the largest scales or if it is necessary to introduce new physical concepts, and whether the density of dark energy is constant or changes over time.

Dark matter, although “invisible”, manifests itself through gravitational influence on visible matter. Roman's observations will provide detailed maps of mass distribution in the universe, from individual galaxy clusters to the cosmic web at the largest scales. This will further test scenarios of structure formation in the universe and dark matter models, including the possibility of the existence of new particles or even alternative theories of gravity.

Open Data and the Role of the Global Scientific Community

One of the more important organizational aspects of the Roman mission is data access. NASA plans to make all scientific data publicly available without long exclusive periods for a limited number of teams. This means that astronomers around the world, from large research institutions to smaller university teams, will be able to work with the same datasets and present their own analyses, catalogs, and discoveries almost simultaneously.

In addition to the three main sky surveys, about a quarter of the time during the primary mission will be reserved for programs proposed by the broader scientific community through the so-called General Investigator Program. Teams will compete for observation time by proposing specific scientific projects – from detailed studies of certain galaxies or gas clouds to tracking exotic, transient phenomena. This model has proven very successful with the Hubble and James Webb telescopes, where it opened space for unexpected discoveries that were not foreseen by the original mission plan.

The enormous volumes of data that Roman will generate will also require completely new approaches to processing and analysis. Intensive application of machine learning methods and advanced statistics is expected to extract useful information from the pile of images and catalogs. Tools are already being developed that will allow future researchers to search databases faster, discover unusual objects, and link Roman's observations with other missions and telescopes.

The Legacy of Nancy Grace Roman and Mission Symbolism

The telescope was named in honor of Nancy Grace Roman, NASA's first chief astronomer and one of the key people responsible for the creation of the Hubble Space Telescope. Ever since the 1960s, Roman advocated the idea of taking telescopes outside Earth's atmosphere to avoid turbulence and the absorption of parts of the electromagnetic spectrum. Because of her role in the development of space astronomy, she was often called the “Mother of Hubble”.

The decision to name the new large infrared mission specifically after Nancy Grace Roman carries strong symbolism: a telescope that will provide “100 Hubbles” in terms of field of view width is directly connected to the person who pushed the idea of the first large space telescope decades ago. The Roman mission continues her vision of space observatories that produce huge amounts of data open to the entire community, from professional astronomers to citizen scientists.

Along with NASA, international partners participate in the mission, including the European Space Agency (ESA), the French agency CNES, the Japanese agency JAXA, and research institutions like the Max Planck Institute for Astronomy. They contribute to instrumentation, calibrations, data processing, and preparation of scientific programs. Roman is thus also an example of global cooperation, in which knowledge, technology, and costs are shared among multiple countries, with the aim of common progress in understanding the universe.

What Follows After Completion of Construction?

The completion of construction on November 25, 2025, does not mean that Roman is immediately ready for launch, but it marks the transition to the final phase where the greatest focus is placed on risk reduction. Every new test can reveal an unexpected weakness or irregularity – whether in electronics, mechanics, or software – so teams at Goddard and partner centers analyze results and conduct corrections if necessary.

If everything goes according to plan, after final tests at the Goddard center, the observatory will be packed into a special shipping container, air-conditioned and protected from vibrations, and transported to the Kennedy Space Center in Florida. There, a new series of checks awaits it as part of preparations for integration with the Falcon Heavy rocket: from testing interaction with rocket systems to a “dress rehearsal” of the launch, in which all key steps from the countdown to the separation of the telescope in space are simulated.

Launch, when it happens, is just the beginning. After separation from the rocket, Roman will spend several months in the commissioning phase: unfolding protective structures, precisely focusing optics, calibrating instruments, and first test observations. Only after that period, if all systems prove stable and within specifications, will the mission move into regular scientific operation, with the first large sky surveys scheduled to begin within the first year after launch.

For now, the completion of construction and entry into the final testing phase confirm that Roman is on a good track towards a launch planned no later than May 2027. If the schedule of tests and preparations continues at a favorable pace, a scenario in which the Nancy Grace Roman Space Telescope begins its journey towards point L2 as early as late 2026 is very realistic, ready to provide us with a completely new view of the universe in the coming years.