"The Roman Space Telescope will conduct multiple large-scale surveys designed to study dark energy, dark matter, exoplanets, and galactic structures."
NASA’s Nancy Grace Roman Space Telescope has completed final integration and is scheduled for launch no earlier than September 2026, with a contractual deadline of May 2027. The observatory will conduct multiple large-scale surveys designed to study dark energy, dark matter, exoplanets, and galactic structures. Recent studies also indicate the telescope may be capable of detecting isolated neutron stars through gravitational microlensing.
Telescope Assembly and Launch
On November 25, 2025, engineers at NASA's Goddard Space Flight Center completed the final integration of the telescope, joining the spacecraft and telescope assemblies. The telescope measures approximately 42 feet (12.7 meters) tall and weighs 9,184 pounds (4,166 kilograms).
Project scientists confirmed at the 247th Meeting of the American Astronomical Society on January 5, 2026, that the earliest likely launch date is September 28, 2026. The telescope was originally introduced in 2016 as the Wide Field Infrared Survey Telescope (WFIRST) and was later renamed after Nancy Grace Roman, NASA's first chief astronomer. Construction began in February 2016 and remained within its initial $4.3 billion budget.
The telescope will launch aboard a SpaceX Falcon Heavy rocket from NASA's Kennedy Space Center in Florida. It is scheduled to be transported approximately 900 miles (1,450 km) from Goddard to the launch site in June 2026. Following launch, mission scientists require approximately 90 days for calibration before data collection can begin.
Orbit and Destination
Roman will be positioned at the Sun-Earth L2 Lagrange point, approximately 1 million miles (1.6 million kilometers) from Earth. This location is also utilized by the James Webb Space Telescope (JWST) and the European Space Agency's Gaia and Euclid telescopes.
Instruments and Capabilities
The telescope carries two primary instruments:
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Wide Field Instrument (WFI): A camera with a 7.9-foot (2.4-meter) primary mirror, similar in size to Hubble's. The WFI includes a 300-megapixel visible-to-near-infrared camera and a slitless spectrometer. Its field of view is at least 100 times larger than Hubble's, enabling it to survey 200 times more sky per image.
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Coronagraph Instrument: A device designed to block light from distant stars, enabling direct imaging of exoplanets. The coronagraph can detect planets approximately 100 million times fainter than their host stars.
Planned Surveys
Roman's five-year primary mission includes three core observation programs:
High-Latitude Wide-Area Survey
This survey will cover over 5,000 square degrees (approximately 12% of the sky) within approximately 1.5 years. The telescope will observe regions away from the dusty plane of the Milky Way to obtain clear views of the distant cosmos.
The survey will combine imaging and spectroscopy to analyze galaxies across cosmic time. Astronomers will study gravitational lensing, where massive objects warp spacetime and distort background objects. The mission anticipates observing over a billion galaxies, with approximately 600 million suitable for weak gravitational lensing analysis.
The survey will collect spectra from approximately 20 million galaxies to measure redshift, enabling the creation of a 3D map extending approximately 11.5 billion light-years. This mapping will reveal baryon acoustic oscillations (BAOs), which are frozen echoes of ancient sound waves that act as a cosmic ruler approximately 500 million light-years wide.
Galactic Bulge Time-Domain Survey
This survey will focus on the densely populated region around the Milky Way's center, known as the galactic bulge. It will consist of repeat visits to six fields covering a total of 1.7 square degrees (approximately 8.5 full moons), with one field targeting the galactic center.
Observations will occur over six seasons, with each field being viewed every 12 minutes during two 72-day periods each spring and fall, totaling 438 days over five years. Less intensive observations will also be conducted to detect long-term microlensing events.
The survey is optimized to detect microlensing events, where a foreground object's gravity bends light from a background star, temporarily amplifying the background star's brightness. This survey is projected to discover over 1,000 new exoplanets using microlensing, including planets ranging in mass from smaller than Mars to gas giants. It may also detect "rogue planets" that lack a host star.
Additional Scientific Applications
A study published in Astronomy and Astrophysics suggests that Roman may identify and characterize dozens of isolated neutron stars using gravitational microlensing. The telescope can measure both the brightening (photometric microlensing) and positional shift (astrometric microlensing) of background stars caused by intervening neutron stars. The astrometric signal enables direct mass measurements.
Only a few thousand neutron stars have been detected, mostly as pulsars; estimates suggest tens to hundreds of millions exist in the Milky Way. Current neutron star mass measurements come only from binary systems. Even a single mass measurement of an isolated neutron star would provide significant data for models of stellar evolution.
Data and Expected Output
Roman is expected to produce approximately 500 terabytes of data per year. During its initial five-year mission, NASA anticipates the telescope will collect more than 20,000 terabytes of data.
The Roman Science Support Center at Caltech/IPAC will manage high-level scientific data processing. All observations will be made publicly available after a short processing period.
Precursor and Support Observations
The Hubble Space Telescope began a precursor survey in spring 2025, covering much of the same area as Roman's Galactic Bulge Time-Domain Survey. The Hubble survey aims to build a catalog of 20–30 million point sources. By obtaining pre-microlensing images, astronomers can identify properties of lensing objects before events occur, enabling direct mass measurements of stars and planets. The Hubble data are available via the Mikulski Archive for Space Telescopes. A paper describing the work was published on May 11, 2026, in the Astrophysical Journal.
Collaborating Institutions
The Nancy Grace Roman Space Telescope project is managed by NASA's Goddard Space Flight Center, with contributions from NASA's Jet Propulsion Laboratory, Caltech/IPAC, the Space Telescope Science Institute, Lawrence Livermore National Laboratory, and various research institutions and industrial contractors.