Nancy Grace Roman Space Telescope

• 1. Introduction

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  A camera of 300.8 megapixels sits at the center of the Nancy Grace Roman Space Telescope. Its images match the sharpness of the Hubble Space Telescope, yet each one covers a patch of sky 100 times larger than Hubble's imaging cameras can frame. Roman is a NASA infrared observatory that finished construction on the 25th of November 2025. It is scheduled to travel to a point in space called Sun-Earth L2, with launch expected no earlier than September 2026. The name honors Nancy Grace Roman, a former NASA Chief of Astronomy. This documentary asks how an observatory of such ambition came to be built around a second-hand mirror. It asks what Roman hopes to learn about the acceleration of the universe and about planets in the cold outer reaches of distant systems. And it asks how the mission survived repeated proposals to cut its funding.

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• 2. A Borrowed Mirror

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  In 2012, a ready-made telescope entered the planning. The National Reconnaissance Office, or NRO, offered to donate two telescopes made by Harris Corporation. Each was the same size as the Hubble Space Telescope, but with a shorter focal length and therefore a wider field of view.

  Before that offer, the plan studied in 2011-2012 was far more modest. That original concept was called WFIRST Design Reference Mission 1, with WFIRST standing for Wide-Field Infrared Survey Telescope. It used a 1.3 m unobstructed three-mirror anastigmat telescope and carried a single instrument, a visible to near-infrared imager with a slitless prism spectrometer. The design itself shares a heritage with several proposals for the Joint Dark Energy Mission, a project between NASA and the Department of Energy.

  The gift gave the project important political momentum. Yet the telescope represents only a modest fraction of the mission's cost, and the boundary conditions of the NRO design may push the total above that of a fresh design. A scientific and technical team matured the idea under the name WFIRST-AFTA, short for Astrophysics Focused Telescope Assets. Today it is the only NASA plan for using the NRO telescopes. The version that emerged is built around a 2.4 m primary mirror.

  The path there ran through many drafts. Teams studied the Joint Dark Energy Mission-Omega configuration, an Interim Design Reference Mission with a 1.3 m telescope, and Design Reference Mission 2 with a 1.1 m telescope. They also studied several iterations of the 2.4 m AFTA configuration. The design that emerged carried a coronagraph in its baseline, a feature aimed at imaging exoplanets directly.

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• 3. Hunting Dark Energy

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  Dark energy sits first on Roman's list of science objectives, and the mission frames it as two questions. The first asks whether cosmic acceleration comes from a new energy component or from a breakdown of general relativity on cosmological scales. The second applies if a new component is the answer. Is its energy density constant in space and time, or has it evolved over the history of the universe?

  The European Space Agency's Euclid mission works on the same problem, and Roman is designed to complement it. To get at the answer, Roman will use three independent techniques. They are baryon acoustic oscillations, observations of distant supernovae, and weak gravitational lensing.

  The stated end goal reaches beyond a single measurement. Roman aims to measure the effects of dark energy, test the consistency of general relativity, and map the curvature of spacetime. Along the way it will probe the chronology of the universe and the growth of cosmic structure.

  The survey has one more target on its list. Roman is also meant to detect primordial black holes.

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• 4. Planets Near and Far

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  Gravitational microlensing is the technique behind Roman's planet census, and it can find worlds with a mass of only a few times that of the Moon. The census is meant to help answer new questions about the potential for life in the universe. How common are solar systems like our own? What kinds of planets exist in the cold, outer regions of planetary systems? What determines the habitability of Earth-like worlds?

  The census would also include a sample of free-floating planets. Their masses are likely to reach down to that of Mars. These are worlds that do not orbit any star, and microlensing is one way to find them.

  A second approach works by direct imaging. The coronagraph is meant to deliver the first direct images and spectra of planets around our nearest neighbors, similar to our own giant planets.

  Roman will also establish a guest investigator mode. It will let researchers use survey investigations to answer diverse questions about our galaxy and the universe.

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• 5. Camera and Coronagraph

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  Eight science filters give the Wide-Field Instrument, or WFI, its range of vision. One is a wide band and seven are narrower. WFI is the mission's primary science instrument, and it covers visible to near-infrared light, from 0.48 to 2.30 micrometers. It offers both multiband imaging and spectroscopy.

  For spectroscopy across a wide field without a slit, WFI carries a high-dispersion grism and a lower-dispersion prism assembly. It also has a dark element made of spectralon. That element can block out light from space and reflect calibration light onto the detector. The eight filters, two spectroscopy elements and dark element all sit on an Element Wheel Assembly. The wheel rotates one into the active position at a time, so scientists can choose the colors a mission needs or switch between imaging and spectroscopy.

  The detector is a HgCdTe-based focal-plane array. It captures a 0.28 square degree field of view at a resolution of 0.11 arcseconds. The array is built from 18 H4RG-10 detectors. On-board calibration helps scientists tell subtle changes in an image from ordinary distortions of the optics or the array. Hexapod actuators can also reposition the focal plane into its best focus, based on analysis from the ground. WFI was completed and shipped to NASA in August 2024.

  The Coronagraph Instrument, or CGI, has a narrower job. It works at shorter wavelengths, from 575 nanometers to 825 nanometers, and uses dual deformable mirror technology to suppress starlight. The goal is a suppression of one part per billion. That would allow detection and spectroscopy of planets as close as 0.15 arcseconds to their host stars.

  CGI is also intended as a technology demonstrator. Its lessons are meant to feed an exoplanet imaging instrument on a future large space observatory, such as the Habitable Worlds Observatory.

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• 6. Fights Over Money

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  In 2010, the National Research Council's Decadal Survey committee recommended this mission as the top priority for the next decade of astronomy. Money then trailed the ambition. Congress provided $56 million in fiscal year 2014 and $50 million in 2015. The fiscal year 2016 spending bill gave $90 million, far above NASA's own request of $14 million.

  That money opened the next stage. On the 17th of February 2016, the mission was approved for development and launch. NASA announced on the 18th that Roman had formally become a project rather than a study. The AFTA portion of the name was dropped at that point, since only that approach was being pursued. Expected cost stood at more than $2 billion. NASA's 2015 estimate of around $2.0 billion in 2010 dollars corresponds to around $2.7 billion in inflation-adjusted dollars.

  In April 2017, NASA commissioned an independent review to check that scope and cost were aligned. The review praised the mission's "groundbreaking and unprecedented survey capabilities for dark energy, exoplanet, and general astrophysics". It also told the project to cut cost and complexity to fit the $3.2 billion target set at the start of Phase B. NASA announced reductions in January 2018. By March 2018 the estimated life cycle cost was back to $3.2 billion, and the Phase B decision was on track for the 11th of April 2018.

  A political threat arrived in February 2018. The Trump administration proposed a fiscal year 2019 budget that would have delayed funding, citing higher priorities within NASA and the telescope's rising cost. Professional astronomers criticized the proposal. The American Astronomical Society expressed "grave concern" and noted that the estimated lifecycle cost had not changed over the previous two years.

  Congress sided with the astronomers. It approved a fiscal year 2018 budget for Roman on the 22nd and the 23rd of March 2018, in excess of the administration's request. Lawmakers stated that they rejected "the cancellation of scientific priorities recommended by the National Academy of Sciences decadal survey process". The President announced that he had signed the bill on the 23rd of March 2018. On the 15th of February 2019, a fiscal year 2019 appropriations bill gave Roman $312 million and reasserted a planning budget of $3.2 billion.

  In March 2019, the administration again proposed to defund Roman, this time in its fiscal year 2020 budget. NASA Administrator Jim Bridenstine hinted at the mission's future in testimony on the 27th of March 2019. He said that "WFIRST will be a critical mission when James Webb is on orbit". A day earlier, NASA Astrophysics Division Director Paul L. Hertz had told a National Academies committee that NASA needed $542 million in fiscal year 2020 to stay on track. NASA announced completion of the Preliminary Design Review on the 1st of November 2019, though it warned that Senate shortfalls threatened further delay.

  In April 2025, the second Trump administration again proposed cutting Roman, in its fiscal year 2026 budget draft. The wider plan would reduce NASA's science budget to $3.9 billion from $7.5 billion in fiscal year 2025. On the 25th of April 2025, the White House Office of Management and Budget announced a plan to cancel dozens of space missions, including Roman. Congress was still debating those cuts.

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• 7. Cost, Pandemic, Launch

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  On the 2nd of March 2020, NASA approved WFIRST to proceed to implementation. The expected development cost was $3.2 billion, with a maximum total of $3.934 billion. That figure included the coronagraph and five years of mission science operations. On the 20th of May 2020, Administrator Jim Bridenstine announced the new name, the Nancy Grace Roman Space Telescope. He cited Nancy Grace Roman's role in the field of astronomy.

  The COVID-19 pandemic then struck at a particularly important time in the telescope's development. On the 31st of March 2021, the NASA Office of Inspector General released a report on the effects. NASA expected a total impact of $400 million from the pandemic and its effect on subcontractors.

  On the 29th of September 2021, NASA announced that Roman had passed its Critical Design Review. With flight hardware fabrication due to finish by 2024, followed by mission integration, launch would come no later than May 2027.

  The ride to space was settled next. On the 19th of July 2022, NASA announced that Roman would fly on a Falcon Heavy launch vehicle. The contract specifies readiness by October 2026, at a launch cost of approximately $255 million. NASA's own launch commitment remains May 2027.

  Hardware milestones came quickly in 2024. In September, the satellite bus that will carry the telescope was substantially completed. In October, the telescope passed a major spin test. In December, the instruments and mirror assembly were successfully integrated onto a section called the instrument carrier, and both instruments were installed into the telescope.

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• 8. Orbit, Builders, Partners

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  Greenbelt, Maryland, is home to the Roman project office at NASA's Goddard Space Flight Center. Goddard holds responsibility for overall project management. It also leads development of the Wide-Field Instrument, the spacecraft and the telescope. The Coronagraph Instrument is being developed at NASA's Jet Propulsion Laboratory in Pasadena, California. Science support is shared among the Space Telescope Science Institute in Baltimore, which is the Science Operations Center, the Infrared Processing and Analysis Center in Pasadena, and Goddard.

  In May 2018, NASA awarded a multi-year contract to Ball Aerospace, now called BAE Systems Space & Mission Systems. It covers the Opto-Mechanical Assembly for the Wide-Field Instrument. In June 2018, Teledyne Scientific and Imaging won the contract for the instrument's infrared detectors. On the 30th of November 2018, NASA awarded the Optical Telescope Assembly contract to the Harris Corporation of Rochester, New York.

  Four international partners have joined NASA: the French space agency CNES, the European Space Agency, the Japan Aerospace Exploration Agency, and the Max Planck Institute for Astronomy. Beginning in 2016, NASA expressed interest in European contributions to the spacecraft, the coronagraph and ground station support. In 2016, JAXA proposed adding a polarization module and a polarization compensator to the coronagraph. Accurate polarimetry may strengthen the science case for exoplanets and planetary disks, which show polarization. Under an agreement signed in June 2022, the Max Planck Institute for Astronomy designed, built and provided all of the coronagraph's Precision Alignment Mechanisms, which operate, stabilize and control optical elements such as filters.

  The choice of orbit took time. The 2015 final report weighed geosynchronous orbit against an orbit around the Sun-Earth Lagrange point L2. L2 costs more in available data rate and propellant. It offers better observing constraints, better thermal stability and a more benign radiation environment. Some science cases, such as exoplanet microlensing parallax, improve there. Whether robotic servicing is possible at either location is unknown. By February 2016, a halo orbit around L2 had been chosen. Ground support will come from a new NASA station in White Sands, New Mexico, the Misasa station in Japan, and the European Space Agency's New Norcia station in Australia.

  The 2025 federal government shutdown briefly put the Goddard work in question. The center began closing multiple buildings and consolidating equipment in what the agency calls a pre-planned "strategic consolidation". A NASA spokesperson told CNN that Roman work would continue as an excepted operation. CNN also reported that an internal document compiled by Goddard staff cited potential impacts on specialized testing laboratories.

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