Roman Coronagraph Instrument
Coronagraph Instrument
The Roman Coronagraph will premiere in space the technologies needed by future missions to image and characterize rocky planets in the habitable zones of nearby stars. By demonstrating these tools in a system with end-to-end, scientific observing operations, NASA will reduce the cost and risk of a future flagship mission.
The Coronagraph architecture consists of three observing modes --- Direct Imaging narrow, Direct Imaging wide, and Spectroscopy --- implemented with three different sets of masks and filters. These modes share the same optical beam train, with two wavefront control loops to achieve high contrast, i.e., better than 10-8. The fully-supported narrow field-of-view mode imaging ("Band 1") will be implemented via a Hybrid Lyot stop mask, whereas the best-effort-supported R~50 prism spectroscopy ("Band 3") and wide field-of-view imaging modes ("Band 1" and "Band 4") will use a Shaped Pupil mask.
Figure 1: Predicted Roman Coronagraph Instrument performance in the context of known planets and existing and planned high-contrast instruments. The Coronagraph Instrument will bridge the gap between massive self-luminous planets in the infrared and reflected light exo-Earths in the optical (Credit, V. Bailey, JPL, https://github.com/nasavbailey/DI-flux-ratio-plot)
After demonstration of the Level-1 requirement on the Instrument, other observations that could be undertaken include known planets which are self-luminous at visible wavelengths; the potential first-ever images and spectroscopy of a true Jupiter analog in reflected light; low surface brightness debris disks; and, the potential first-ever visible light images of exozodi.
The Coronagraph Community Participation Program (CPP) will work with the Coronagraph Instrument team to plan and execute its technology demonstration high-contrast observations. The principals of each selected investigation, together with the Coronagraph project and international partner representatives, form the basis of the CPP Team.
The Roman Science Support Center at IPAC, working with partners at the Jet Propulsion Laboratory (JPL), is responsible for the Coronagraph Instrument operations, data processing and management, and support for the exoplanet community.
Optical Layout of the Coronagraph
Figure 2: The optical layout of the Roman Coronagraph Instrument. The instrument's beam path begins at the fast steering mirror (FSM) and ends at the direct imaging detector (labeled DI FPA). This visually conveys how each observation requires a complex and time-intensive sequence, underscoring operational limitations like long setup times and calibration needs.
Below we list the Precision Alignment Mechanisms (PAMs) acronyms featured in the diagram, as these are the configurable settings that make up the listed observing modes:
SPAM: Shaped Pupil Alignment Mechanism
FPAM: Focal Plane Alignment Mechanism
LSAM: Lyot Stop Alignment Mechanism
FSAM: Field Stop Alignment Mechanism
CFAM: Color Filter Alignment Mechanism
DPAM: Dispersion Polarizer Alignment Mechanism