arXiv subjects

Eric Cady

Publications and source records attributed to Eric Cady.

At least 19 recordsLinked to original sources

arXiv2026

The Roman Coronagraph Community Participation Program: early calibration plan and pilot observation of a companion

Roman is set to launch in weeks! The Coronagraph Instrument - technology pathfinder for future direct imaging missions - is ready to fly too. According to predictions, laboratory tests and high fidelity simulations, it will open a new contrast regime enabling the imaging of mature, giant planets in visible reflected light. The Community Participation Program is responsible for preparing a comprehensive observing program with associated data processing software and calibrations. We give a brief update about the on-going "baseline" calibration plan for the first months. Additionally, we describe a pilot program aiming for the stellar companion HD 29992 B at moderate ~1e-5 to ~1e-6 Band 1 (575 nm) contrast, to be carried out as soon as the instrument is operational. The idea is to generate a canonical data set with a self luminous companion that is easily recoverable. This functional checkout will be precious to best prepare our community, exercise our calibration plan and suite of tools.

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arXiv2026

The Roman Coronagraph Community Participation Program: trials and triumphs of designing an observing program for a technology demonstration instrument

The Coronagraph Instrument onboard the Nancy Grace Roman Space Telescope serves as a crucial technology pathfinder for the Habitable Worlds Observatory, with on-sky verification of high-contrast imaging techniques and the potential to image a Jupiter analog in reflected light for the first time. Together with the Roman Project Team, the Community Participation Program (CPP) is responsible for target selection, preparatory observations, developing an exposure time calculator, target database, data reduction pipeline, simulation tools, and engagement with the broader community. Here we present an overview of the CPP activities over the past two years with an emphasis on observation planning activities for the initial in-orbit checkout and the first six months of the observation phase. Finally, we present future opportunities for the astronomical community to interact with the data as it becomes public early in the mission.

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arXiv2026

The Roman Coronagraph Community Participation Program: Observation planning and data reduction for polarimetric mode

Reflected-light polarimetry of exoplanets constrains and resolves degeneracies in atmospheric properties, while polarized light observations of debris disks enable the characterization of dust-grain properties. The best-effort polarimetric mode of the Roman Coronagraph Instrument will be able to perform multi-wavelength observations of planetary systems using both the Hybrid Lyot Coronagraph (HLC) and the Shaped Pupil Coronagraph (SPC). This paper presents an overview of observation planning, simulations, and data reduction procedures for the polarimetric mode of the Roman Coronagraph. As an initial test of simulation and data reduction, a dataset of polarimetric observing sequences for the debris disk HD 172555 in HLC mode was generated using corgisim with estimated observation parameters, and data reduction was performed using corgidrp, incorporating all relevant noise factors and calibration products. Currently, mock calibration products are used in corgidrp; these will be replaced with simulated calibration products in future updates

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arXiv2025

High-order wavefront sensing and control for the Roman Coronagraph Instrument (CGI): architecture and measured performance

The Nancy Grace Roman Space Telescope (``Roman'') is a 2.4m space telescope scheduled for a 2026 launch. The Coronagraph Instrument (CGI) on Roman is a technology-demonstration instrument with a coronagraph and, for the first time in space, deformable mirrors and active wavefront control. This paper walks through the algorithmic and system-level architecture of the HOWFSC implementation for CGI, including the use of ground-in-the-loop (GITL) operations to support computationally-expensive operations, and reports on instrument performance measured during thermal vacuum testing in instrument integration and test. CGI achieved better than $5\times10^{-8}$ total raw contrast with two independent coronagraph architectures covering 3-9 and 6-20 $\lambda/D$ between them and a $360^{\circ}$ dark hole on each. The contrast limits appear to be driven by time available for testing, and do not appear to represent a floor in the achievable performance of CGI in flight.

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arXiv2024

Current laboratory performance of starlight suppression systems, and potential pathways to desired Habitable Worlds Observatory exoplanet science capabilities

We summarize the current best polychromatic (10 to 20 % bandwidth) contrast performance demonstrated in the laboratory by different starlight suppression approaches and systems designed to directly characterize exoplanets around nearby stars. We present results obtained by internal coronagraph and external starshade experimental testbeds using entrance apertures equivalent to off-axis or on-axis telescopes, either monolithic or segmented. For a given angular separation and spectral bandwidth, the performance of each starlight suppression system is characterized by the values of raw contrast (before image processing), off-axis (exoplanet) core throughput, and post-calibration contrast (the final 1 sigma detection limit of off-axis point sources, after image processing). To place the current laboratory results in the perspective of the future Habitable Worlds Observatory (HWO) mission, we simulate visible observations of a fiducial Earth/Sun twin system at 12 pc, assuming a 6m (inscribed diameter) collecting aperture and a realistic end-to-end optical throughput. The exposure times required for broadband exoearth detection (20% bandwidth around a wavelength of 0.55 microns) and visible spectroscopic observations (R=70) are then computed assuming various levels of starlight suppression performance, including the values currently demonstrated in the laboratory. Using spectroscopic exposure time as a simple metric, our results point to key starlight suppression system design performance improvements and trades to be conducted in support of HWO exoplanet science capabilities. These trades may be explored via numerical studies, lab experiments, as well as high contrast space-based observations and demonstrations.

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arXiv2023

Nancy Grace Roman Space Telescope Coronagraph Instrument Overview and Status

The Nancy Grace Roman Space Telescope Coronagraph Instrument is a critical technology demonstrator for NASA's Habitable Worlds Observatory. With a predicted visible-light flux ratio detection limit of 1E-8 or better, it will be capable of reaching new areas of parameter space for both gas giant exoplanets and circumstellar disks. It is in the final stages of integration and test at the Jet Propulsion Laboratory, with an anticipated delivery to payload integration in the coming year. This paper will review the instrument systems, observing modes, potential observing applications, and overall progress toward instrument integration and test.

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arXiv2023

Planet Search with the Keck/NIRC2 Vortex Coronagraph in Ms-band for Vega

Gaps in circumstellar disks can signal the existence of planetary perturbers, making such systems preferred targets for direct imaging observations of exoplanets. Being one of the brightest and closest stars to the Sun, the photometric standard star Vega hosts a two-belt debris disk structure. Together with the fact that its planetary system is being viewed nearly face-on, Vega has been one of the prime targets for planet imaging efforts. Using the vector vortex coronagraph on Keck/NIRC2 in Ms-band at 4.67 $\mu$m, we report the planet detection limits from 1 au to 22 au for Vega with an on-target time of 1.8 h. We reach a 3 Jupiter mass limit exterior to 12 au, which is nearly an order of magnitude deeper than existing studies. Combining with existing radial velocity studies, we can confidently rule out the existence of companions more than ~8 Jupiter mass from 22 au down to 0.1 au for Vega. Interior and exterior to ~4 au, this combined approach reaches planet detection limits down to ~2-3 Jupiter mass using radial velocity and direct imaging, respectively. By reaching multi-Jupiter mass detection limits, our results are expected to be complemented by the planet imaging of Vega in the upcoming observations using the James Webb Space Telescope to obtain a more holistic understanding of the planetary system configuration around Vega.

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arXiv2020

Starshade formation flying I: optical sensing

A key challenge for starshades is formation flying. To successfully image exoplanets, the telescope boresight and starshade must be aligned to ~1 m at separations of tens of thousands of kilometers. This challenge has two parts: first, the relative position of the starshade with respect to the telescope must be sensed; and second, sensor measurements must be combined with a control law to keep the two spacecraft aligned in the presence of gravitational and other disturbances. In this work, we present an optical sensing approach using a pupil imaging camera in a 2.4-m telescope that can measure the relative spacecraft bearing to a few centimeters in 1 s, much faster than any relevant dynamical disturbances. A companion paper will describe how this sensor can be combined with a control law to keep the two spacecraft aligned with minimal interruptions to science observations.

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arXiv2020

The Habitable Exoplanet Observatory (HabEx) Mission Concept Study Final Report

The Habitable Exoplanet Observatory, or HabEx, has been designed to be the Great Observatory of the 2030s. For the first time in human history, technologies have matured sufficiently to enable an affordable space-based telescope mission capable of discovering and characterizing Earthlike planets orbiting nearby bright sunlike stars in order to search for signs of habitability and biosignatures. Such a mission can also be equipped with instrumentation that will enable broad and exciting general astrophysics and planetary science not possible from current or planned facilities. HabEx is a space telescope with unique imaging and multi-object spectroscopic capabilities at wavelengths ranging from ultraviolet (UV) to near-IR. These capabilities allow for a broad suite of compelling science that cuts across the entire NASA astrophysics portfolio. HabEx has three primary science goals: (1) Seek out nearby worlds and explore their habitability; (2) Map out nearby planetary systems and understand the diversity of the worlds they contain; (3) Enable new explorations of astrophysical systems from our own solar system to external galaxies by extending our reach in the UV through near-IR. This Great Observatory science will be selected through a competed GO program, and will account for about 50% of the HabEx primary mission. The preferred HabEx architecture is a 4m, monolithic, off-axis telescope that is diffraction-limited at 0.4 microns and is in an L2 orbit. HabEx employs two starlight suppression systems: a coronagraph and a starshade, each with their own dedicated instrument.

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arXiv2019

The ExoEarth Yield Landscape for Future Direct Imaging Space Telescopes

The expected yield of potentially Earth-like planets is a useful metric for designing future exoplanet-imaging missions. Recent yield studies of direct-imaging missions have focused primarily on yield methods and trade studies using "toy" models of missions. Here we increase the fidelity of these calculations substantially, adopting more realistic exoplanet demographics as input, an improved target list, and a realistic distribution of exozodi levels. Most importantly, we define standardized inputs for instrument simulations, use these standards to directly compare the performance of realistic instrument designs, include the sensitivity of coronagraph contrast to stellar diameter, and adopt engineering-based throughputs and detector parameters. We apply these new high-fidelity yield models to study several critical design trades: monolithic vs segmented primary mirrors, on-axis vs off-axis secondary mirrors, and coronagraphs vs starshades. We show that as long as the gap size between segments is sufficiently small, there is no difference in yield for coronagraph-based missions with monolithic off-axis telescopes and segmented off-axis telescopes, assuming that the requisite engineering constraints imposed by the coronagraph can be met in both scenarios. We show that there is currently a factor of ~2 yield penalty for coronagraph-based missions with on-axis telescopes compared to off-axis telescopes, and note that there is room for improvement in coronagraph designs for on-axis telescopes. We also reproduce previous results in higher fidelity showing that the yields of coronagraph-based missions continue to increase with aperture size while the yields of starshade-based missions turnover at large apertures if refueling is not possible. Finally, we provide absolute yield numbers with uncertainties that include all major sources of astrophysical noise to guide future mission design.

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arXiv2019

Key Technologies for the Wide Field Infrared Survey Telescope Coronagraph Instrument

The Wide Field Infrared Survey Telescope (WFIRST) Coronagraph Instrument (CGI) is a high-contrast imager and integral field spectrograph that will enable the study of exoplanets and circumstellar disks at visible wavelengths. Ground-based high-contrast instrumentation has fundamentally limited performance at small working angles, even under optimistic assumptions for 30m-class telescopes. There is a strong scientific driver for better performance, particularly at visible wavelengths. Future flagship mission concepts aim to image Earth analogues with visible light flux ratios of more than 10^10. CGI is a critical intermediate step toward that goal, with a predicted 10^8-9 flux ratio capability in the visible. CGI achieves this through improvements over current ground and space systems in several areas: (i) Hardware: space-qualified (TRL9) deformable mirrors, detectors, and coronagraphs, (ii) Algorithms: wavefront sensing and control; post-processing of integral field spectrograph, polarimetric, and extended object data, and (iii) Validation of telescope and instrument models at high accuracy and precision. This white paper, submitted to the 2018 NAS Exoplanet Science Strategy call, describes the status of key CGI technologies and presents ways in which performance is likely to evolve as the CGI design matures.

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arXiv2019

Lessons for WFIRST CGI from ground-based high-contrast systems

The Coronagraph Instrument (CGI) for NASA's 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.

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arXiv2018

A deep search for planets in the inner 15 au around Vega

We present the results of a deep high-contrast imaging search for planets around Vega. Vega is an ideal target for high-contrast imaging because it is bright, nearby, and young with a face-on two-belt debris disk which may be shaped by unseen planets. We obtained $J-$ and $H-$band data on Vega with the coronagraphic integral-field spectrograph Project 1640 (P1640) at Palomar Observatory. Two nights of data were obtained in 2016, in poor seeing conditions, and two additional nights in more favorable conditions in 2017. In total, we obtained 5.5 hours of integration time on Vega in moderate to good seeing conditions (<1.5"). We did not detect any low mass companions in this system. Our data present the most sensitive contrast limits around Vega at very small separations (2-15 au) thus far, allowing us to place new constraints on the companions which may be sculpting the Vega system. In addition to new constraints, as the deepest data obtained with P1640, these observations form the final legacy of the now decommissioned instrument.

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arXiv2018

Review of high-contrast imaging systems for current and future ground-based and space-based telescopes II. Common path wavefront sensing/control and Coherent Differential Imaging

The Optimal Optical Coronagraph (OOC) Workshop held at the Lorentz Center in September 2017 in Leiden, the Netherlands, gathered a diverse group of 25 researchers working on exoplanet instrumentation to stimulate the emergence and sharing of new ideas. In this second installment of a series of three papers summarizing the outcomes of the OOC workshop (see also~\citenum{ruane2018,snik2018}), we present an overview of common path wavefront sensing/control and Coherent Differential Imaging techniques, highlight the latest results, and expose their relative strengths and weaknesses. We layout critical milestones for the field with the aim of enhancing future ground/space based high contrast imaging platforms. Techniques like these will help to bridge the daunting contrast gap required to image a terrestrial planet in the zone where it can retain liquid water, in reflected light around a G type star from space.

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arXiv2018

Review of high-contrast imaging systems for current and future ground-based and space-based telescopes III. Technology opportunities and pathways

The Optimal Optical CoronagraphWorkshop at the Lorentz Center in September 2017 in Leiden, the Netherlands gathered a diverse group of 25 researchers working on exoplanet instrumentation to stimulate the emergence and sharing of new ideas. This contribution is the final part of a series of three papers summarizing the outcomes of the workshop, and presents an overview of novel optical technologies and systems that are implemented or considered for high-contrast imaging instruments on both ground-based and space telescopes. The overall objective of high contrast instruments is to provide direct observations and characterizations of exoplanets at contrast levels as extreme as 10^-10. We list shortcomings of current technologies, and identify opportunities and development paths for new technologies that enable quantum leaps in performance. Specifically, we discuss the design and manufacturing of key components like advanced deformable mirrors and coronagraphic optics, and their amalgamation in "adaptive coronagraph" systems. Moreover, we discuss highly integrated system designs that combine contrast-enhancing techniques and characterization techniques (like high-resolution spectroscopy) while minimizing the overall complexity. Finally, we explore extreme implementations using all-photonics solutions for ground-based telescopes and dedicated huge apertures for space telescopes.

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arXiv2017

Electric Field Conjugation for Ground Based High-Contrast Imaging: Robustness Study and Tests with the Project 1640 Coronagraph

The electric field conjugation (EFC) algorithm has shown promise for removing scattered starlight from high-contrast imaging measurements, both in numerical simulations and laboratory experiments. To prepare for the deployment of EFC using ground-based telescopes we investigate the response of EFC to unaccounted for deviations from an ideal optical model. We explore the linear nature of the algorithm by assessing its response to a range of inaccuracies in the optical model generally present in real systems. We find that the algorithm is particularly sensitive to unresponsive deformable mirror (DM) actuators, misalignment of the Lyot stop, and misalignment of the focal plane mask. Vibrations and DM registration appear to be less of a concern compared to values expected at the telescope. We quantify how accurately one must model these core coronagraph components to ensure successful EFC corrections. We conclude that while the condition of the DM can limit contrast, EFC may still be used to improve the sensitivity of high-contrast imaging observations. Our results have informed the development of a full EFC implementation using the Project 1640 coronagraph at Palomar observatory. While focused on a specific instrument our results are applicable to the many coronagraphs that may be interested in employing EFC.

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arXiv2016

Maximized ExoEarth Candidate Yields for Starshades

The design and scale of a future mission to directly image and characterize potentially Earth-like planets will be impacted, to some degree, by the expected yield of such planets. Recent efforts to increase the estimated yields, by creating observation plans optimized for the detection and characterization of Earth-twins, have focused solely on coronagraphic instruments; starshade-based missions could benefit from a similar analysis. Here we explore how to prioritize observations for a starshade given the limiting resources of both fuel and time, present analytic expressions to estimate fuel use, and provide efficient numerical techniques for maximizing the yield of starshades. We implemented these techniques to create an approximate design reference mission code for starshades and used this code to investigate how exoEarth candidate yield responds to changes in mission, instrument, and astrophysical parameters for missions with a single starshade. We find that a starshade mission operates most efficiently somewhere between the fuel- and exposure-time limited regimes, and as a result, is less sensitive to photometric noise sources as well as parameters controlling the photon collection rate in comparison to a coronagraph. We produced optimistic yield curves for starshades, assuming our optimized observation plans are schedulable and future starshades are not thrust-limited. Given these yield curves, detecting and characterizing several dozen exoEarth candidates requires either multiple starshades or an eta_Earth > ~0.3.

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arXiv2016

Characterization of the Companion to $\mu$ Her

$\mu$ Her is a nearby quadruple system with a G-subgiant primary and several low mass companions arranged in a 2+2 architecture. While the BC components have been well characterized, the Ab component has been detected astrometrically and with direct imaging but there has been some confusion over its nature, in particular whether the companion is stellar or substellar. Using near-infrared spectroscopy we are able to estimate the spectral type of the companion as a M4$\pm$1V star. In addition, we have measured the astrometry of the system for over a decade. We combined the astrometry with archival radial velocity measurements to compute an orbit of the system. From the combined orbit, we are able to compute the mass sum of the system. Using the estimated mass of the primary, we estimate the mass of the secondary as 0.32 M_sun, which agrees with the estimated spectral type. Our computed orbit is preliminary due to the incomplete orbital phase coverage, but it should be sufficient to predict ephemerides over the next decade.

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