Nancy Grace Roman telescope

The Nancy Grace Roman Space Telescope (formerly WFIRST) is NASA’s premier next-generation wide-field infrared observatory. Operating from the Sun-Earth Lagrange point 2 (L2), Roman is engineered to map the cosmos at unprecedented speeds, complementing the narrow-field depth of the James Webb Space Telescope (JWST) and the ultraviolet-visible imaging of the Hubble Space Telescope.

Core Specifications & Optical Design

Roman pairs a Hubble-sized primary mirror with an optical layout optimized for massive structural field coverage.

Parameter	Specification
Primary Mirror Diameter	2.4 meters (7.9 feet)
Field of View	0.281 deg², over 100 times larger than Hubble’s near-IR view
Optical Design	Three-mirror anastigmat telescope
Wavelength Range	0.48 to 2.3 micrometers (visible to near-infrared)
Orbit	Halo orbit around Sun-Earth L2
Design Lifetime	5-year primary mission (10-year goal)
Data Volume	~11 Terabits downlinked per day

Scientific Instrumentation

Roman carries two main instruments integrated into its payload carrier:

1. Wide Field Instrument (WFI)

Detector Array: 300.8-megapixel focal plane array consisting of 18 Teledyne HgCdTe (Mercury-Cadmium-Telluride) detectors (4096 × 4096 pixels each).
Capabilities: 8 broad-band imaging filters, a slitless high-dispersion grism, and a low-dispersion prism for multi-object spectroscopy.
Function: Serves as the primary survey engine, capturing vast swaths of the sky with Hubble-like resolution (0.11 arcseconds per pixel) in fractions of the time.

2. Coronagraph Instrument (CGI)

Technology Demonstration: A high-contrast imaging system designed to perform direct imaging of exoplanets and circumstellar disks.
Key Optics: Features advanced starlight-suppression masks combined with active wavefront control (two deformable mirrors driven by thousands of actuators).
Performance: Capable of dimming a central star’s light by a factor of 100 million to 1 billion, allowing direct detection of Gas Giants and sub-Neptune planets in visible light.

Primary Science Objectives

Dark Energy & Cosmic Acceleration: By mapping billions of faint galaxies across cosmic time, Roman will measure weak gravitational lensing, baryon acoustic oscillations, and redshift-space distortions to test General Relativity and evaluate dark energy models.
Exoplanet Microlensing Survey: By monitoring tens of millions of stars in the inner Milky Way bulge, Roman will detect planetary systems via gravitational microlensing. This technique is sensitive to exoplanets far from their host stars—including sub-Earth mass bodies and rogue planets wandering without a star.
Core Community Surveys: Roman will execute open-access legacy sky surveys, assembling massive deep-field datasets to explore galaxy evolution, black hole demographics, and local structure.