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Exoplanet imaging requires super polished off-axis parabolas (OAP) with the utmost surface quality. In this paper we describe an innovative manufacturing process combining 3D printing and stress polishing, to create a warping harness capable of producing any off axis parabola profile with a single actuator. The warping harness is manufactured by 3D printing. This method will be applied to the production of the WFIRST coronagraphs off axis parabolas. The evolution of the warping harness design is presented, starting from a ring warping harness generating astigmatism, to an innovative thickness distribution harness optimised to generate an off axis parabola shape. Several design options are available for the prototyping phase, with their advantages and disadvantages which will be discussed.
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The Coronagraph Instrument (CGI) for NASAs Wide Field Infrared Survey Telescope (WFIRST) will constitute a dramatic step forward for high-contrast imaging, integral field spectroscopy, and polarimetry of exoplanets and circumstellar disks, aiming to improve upon the sensitivity of current ground-based direct imaging facilities by 2-3 orders of magnitude. Furthermore, CGI will serve as a pathfinder for future exo-Earth imaging and characterization missions by demonstrating wavefront control, coronagraphy, and spectral retrieval in a new contrast regime, and by validating instrument and telescope models at unprecedented levels of precision. To achieve this jump in performance, it is critical to draw on the experience of ground-based high-contrast facilities. We discuss several areas of relevant commonalities, including: wavefront control, post-processing of integral field unit data, and calibration and observing strategies.
The Coronagraph Instrument (CGI) on the Nancy Grace Roman Space Telescope will demonstrate the high-contrast technology necessary for visible-light exoplanet imaging and spectroscopy from space via direct imaging of Jupiter-size planets and debris disks. This in-space experience is a critical step toward future, larger missions targeted at direct imaging of Earth-like planets in the habitable zones of nearby stars. This paper presents an overview of the current instrument design and requirements, highlighting the critical hardware, algorithms, and operations being demonstrated. We also describe several exoplanet and circumstellar disk science cases enabled by these capabilities. A competitively selected Community Participation Program team will be an integral part of the technology demonstration and could perform additional CGI observations beyond the initial tech demo if the instrument performance warrants it.
The science investigation teams (SITs) for the WFIRST coronagraphic instrument have begun studying the capabilities of the instrument to directly image reflected light off from exoplanets at contrasts down to contrasts of ~10^-9 with respect to the stellar flux. Detection of point sources at these high contrasts requires yield estimates and detailed modeling of the image of the planetary system as it propagates through the telescope optics. While the SITs might generate custom astrophysical scenes, the integrated model, propagated through the internal speckle field, is typically done at JPL. In this white paper, we present a standard file format to ensure a single distribution system between those who produce the raw astrophysical scenes, and JPL modelers who incorporate those scenes into their optical modeling. At its core, our custom file format uses FITS files, and incorporates standards on packaging astrophysical scenes. This includes spectral and astrometric information for planetary and stellar point sources, zodiacal light and extragalactic sources that may appear as contaminants. Adhering to such a uniform data distribution format is necessary, as it ensures seamless work flow between the SITs and modelers at JPL for the goals of understanding limits of the WFIRST coronagraphic instrument.
Pandeia is the exposure time calculator (ETC) system developed for the James Webb Space Telescope (JWST) that will be used for creating JWST proposals. It includes a simulation-hybrid Python engine that calculates the two-dimensional pixel-by-pixel signal and noise properties of the JWST instruments. This allows for appropriate handling of realistic point spread functions, MULTIACCUM detector readouts, correlated detector readnoise, and multiple photometric and spectral extraction strategies. Pandeia includes support for all the JWST observing modes, including imaging, slitted/slitless spectroscopy, integral field spectroscopy, and coronagraphy. Its highly modular, data-driven design makes it easily adaptable to other observatories. An implementation for use with WFIRST is also available.
The Astro2010 Decadal Survey recommended a Wide Field Infrared Survey Telescope (WFIRST) as its top priority for a new large space mission. The report of the WFIRST-AFTA Science Definition Team (SDT) presents a Design Reference Mission for WFIRST that employs one of the 2.4-m, Hubble-quality mirror assemblies recently made available to NASA. The 2.4-m primary mirror enables a mission with greater sensitivity and higher angular resolution than the smaller aperture designs previously considered for WFIRST, increasing both the science return of the primary surveys and the capabilities of WFIRST as a Guest Observer facility. The option of adding an on-axis, coronagraphic instrument would enable imaging and spectroscopic studies of planets around nearby stars. This short article, produced as a companion to the SDT report, summarizes the key points of the WFIRST-2.4 DRM. It highlights the remarkable opportunity that the 2.4-m telescope affords for advances in many fields of astrophysics and cosmology, including dark energy, the demographics and characterization of exoplanets, the evolution of galaxies and quasars, and the stellar populations of the Milky Way and its neighbors.
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