Dmitry Savransky

Want to cite the work this poster was based on? Read our open access publication "Identifying surface degeneracies in single-visit reflected light observations of modern Earth using the Habitable Worlds Observatory" by A. S. Zelakiewicz et al. 2026 in the HWO JATIS special edition on SciX.Poster Abstract:Upcoming observatories, such as the space-based Habitable Worlds Observatory (HWO) and the ground-based Extremely Large Telescope (ELT), will revolutionize our understanding of terrestrial exoplanets through reflected-light observations. These telescopes will suppress the on-axis stellar PSF through coronagraphy to capture the unique spectral fingerprint of these worlds. Reflected-light observations will enable the first exploration of rocky exoplanet surfaces, revealing potential biosignatures through biopigments, such as the chlorophyll-induced vegetation/photosynthetic red edge on Earth. However, constraints on surface pigmentation are dependent on the precise classification of bulk planetary parameters and atmospheric properties. Here, we show results from single-visit optical and near-infrared observation models with the HWO Exploratory Analytical Case (EAC) 5 design, the largest of the EAC designs, equipped with a charge-6 vector vortex coronagraph. We analyzed synthetic HWO datasets of modern Earth using state-of-the-art atmospheric retrieval algorithms. We find that we need to develop a strategy to reduce degeneracies in identifying surface materials. Planetary radius, surface pressure, cloud coverage, and surface materials can produce consistent solutions with simulated single-visit observations at the spectral resolution of HWO. Specifically, constraints on planetary radius are necessary to normalize the planet-star flux ratio and accurately determine the coverage of surfaces that do not exhibit unique VIS/NIR spectral features. We also identify how the selection of representative surface spectra can bias atmospheric retrieval results. Strategies to break the degeneracies inherent in reflected-light observations are critical before first light for these next-generation observatories.

Want to cite the work this poster was based on? Read our open access publication "Identifying surface degeneracies in single-visit reflected light observations of modern Earth using the Habitable Worlds Observatory" by A. S. Zelakiewicz et al. 2026 in the HWO JATIS special edition on SciX.Poster Abstract:Upcoming observatories, such as the space-based Habitable Worlds Observatory (HWO) and the ground-based Extremely Large Telescope (ELT), will revolutionize our understanding of terrestrial exoplanets through reflected-light observations. These telescopes will suppress the on-axis stellar PSF through coronagraphy to capture the unique spectral fingerprint of these worlds. Reflected-light observations will enable the first exploration of rocky exoplanet surfaces, revealing potential biosignatures through biopigments, such as the chlorophyll-induced vegetation/photosynthetic red edge on Earth. However, constraints on surface pigmentation are dependent on the precise classification of bulk planetary parameters and atmospheric properties. Here, we show results from single-visit optical and near-infrared observation models with the HWO Exploratory Analytical Case (EAC) 5 design, the largest of the EAC designs, equipped with a charge-6 vector vortex coronagraph. We analyzed synthetic HWO datasets of modern Earth using state-of-the-art atmospheric retrieval algorithms. We find that we need to develop a strategy to reduce degeneracies in identifying surface materials. Planetary radius, surface pressure, cloud coverage, and surface materials can produce consistent solutions with simulated single-visit observations at the spectral resolution of HWO. Specifically, constraints on planetary radius are necessary to normalize the planet-star flux ratio and accurately determine the coverage of surfaces that do not exhibit unique VIS/NIR spectral features. We also identify how the selection of representative surface spectra can bias atmospheric retrieval results. Strategies to break the degeneracies inherent in reflected-light observations are critical before first light for these next-generation observatories.

Abstract The upcoming Roman Coronagraph will be the first high-contrast instrument in space capable of high-order wave front sensing and control technologies, a critical technology demonstration for the proposed Habitable Worlds Observatory (HWO) that aims to directly image and characterize habitable exoEarths. The nominal Roman Coronagraph observing plan involves alternating observations of a science target and a bright, nearby reference star. High contrast is achieved using wave front sensing and control, also known as “digging a dark hole,” where performance depends on the properties of the reference star, requiring V < 3, a resolved stellar diameter <2 mas, and no stellar multiplicity. The imposed brightness and diameter criteria limit the sample of reference star candidates to high-mass main-sequence and post-main-sequence objects, where multiplicity rates are high. A future HWO coronagraph may have similarly restrictive criteria in reference star selection. From an exhaustive literature review of 95 stars, we identify an initial list of 40 primary and 18 reserve reference star candidates relevant to both the Roman Coronagraph and HWO. We present results from an initial survey of these candidates with high-resolution adaptive optics imaging and speckle interferometry and identify no new companions. We discuss the need for higher-contrast observations to sufficiently vet these reference star candidates prior to Roman Coronagraph observations, along with the implications of reference star criteria on observation planning for Roman and HWO.

Abstract We present confirmation of HD 143811 AB b, a substellar companion to spectroscopic binary HD 143811 AB through direct imaging with the Gemini Planet Imager (GPI) and Keck NIRC2. HD 143811 AB was observed as a part of the GPI Exoplanet Survey in 2016 and 2019 and is a member of the Sco-Cen star formation region. The exoplanet is detected ∼430 mas from the host star by GPI. With two GPI epochs and one from Keck/NIRC2 in 2022, we confirm through common proper motion analysis that the object is bound to its host star. We derive an orbit with a semimajor axis of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>6</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>4</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>14</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>32</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> au and eccentricity <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>0.23</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.16</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.24</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> . Spectral analysis of the GPI H -band spectrum and NIRC2 L′ photometry provides additional proof that this object is a substellar companion. We compare the spectrum of HD 143811 AB b to PHOENIX stellar models and Exo-Radioactive-Convective Equilibrium Model (REM) exoplanet atmosphere models and find that Exo-REM models provide the best fits to the data. From the Exo-REM models, we derive an effective temperature of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>104</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>132</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>178</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> K for the planet and translate the derived luminosity of the planet to a mass of 5.6 ± 1.1 M Jup assuming hot-start evolutionary models. HD 143811 AB b is the first directly imaged planet around a binary that is not on an ultrawide orbit. Future characterization of this object will shed light on the formation of planets around binary star systems.

Abstract HD 143811 AB is the host star to the directly imaged planet HD 143811 AB b, which was recently discovered using data from the Gemini Planet Imager and Keck NIRC2. A member of the Sco-Cen star-forming region with an age of 13 ± 4 Myr, HD 143811 AB is somewhat rare among hosts of directly imaged planets, as it is a close stellar binary, with an ∼18-day period. Accurate values for the orbital and stellar parameters of this binary are needed to understand the formation and evolutionary history of the planet in orbit. We utilize archival high-resolution spectroscopy from FEROS on the MPG/ESO 2.2 m telescope to fit the orbit of the binary, and we combine with unresolved photometry to derive the basic stellar properties of the system. From the orbit, we derive precise values of orbital period of 18.59090 ± 0.00007 days and mass ratio of 0.886 ± 0.003. When combined with stellar evolutionary models, we find masses of both components of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mi>M</mml:mi> <mml:mi mathvariant="normal">A</mml:mi> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>1.3</mml:mn> <mml:msubsup> <mml:mn>0</mml:mn> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.05</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.03</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> M ⊙ and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mi>M</mml:mi> <mml:mi mathvariant="normal">B</mml:mi> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>1.1</mml:mn> <mml:msubsup> <mml:mn>5</mml:mn> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.04</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.03</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> M ⊙ . While the current data are consistent with the planet and stellar orbits being coplanar, the 3D orientations of both systems are currently poorly constrained, with additional observations required to more rigorously test for coplanarity.

Abstract Science yield studies will drive the development of future direct imaging telescopes, such as the Habitable Worlds Observatory. These studies rely on a metric called completeness, which represents the fraction of planets from an assumed planet population that can be detected for a given observing scenario. Completeness is often calculated by comparing the brightness of planets in the population to the “photometric constraint,” or the dimmest planet detectable in a given observing scenario. The photometric constraint has also been used to calculate the probability of directly imaging a planet detected by the radial velocity method. This work shows how to numerically and analytically invert the analytic exposure time calculator used by the Nancy Grace Roman Space Telescope’s coronagraph instrument to calculate a precise photometric constraint that accounts for planet–star separation, integration time, zodiacal light brightness during observation, and assumed exozodiacal light. This refined photometric constraint is then used to calculate completeness and probability of detection in an efficient manner. Finally, we show that the probability of detection values calculated using the refined photometric constraint closely tracks the planet’s true detectability. We validate our approach by generating realistic planetary systems, simulating an extreme-precision radial velocity survey, performing orbit fits, and computing the probability of directly imaging the fitted planets with a telescope design similar to the future Habitable Worlds Observatory. Our validation tests show that the probability of detection values predicts the number of direct imaging detections to within 4% when scheduling observations at high probability of detection values.

The upcoming Roman Coronagraph will be the first high-contrast instrument in space capable of high-order wavefront sensing and control technologies, a critical technology demonstration for the proposed Habitable Worlds Observatory (HWO) that aims to directly image and characterize habitable exoEarths. The nominal Roman Coronagraph observing plan involves alternating observations of a science target and a bright, nearby reference star. High contrast is achieved using wavefront sensing and control, also known as "digging a dark hole", where performance depends on the properties of the reference star, requiring V&lt;3, a resolved stellar diameter &lt;2 mas, and no stellar multiplicity. The imposed brightness and diameter criteria limit the sample of reference star candidates to high-mass main sequence and post-main sequence objects, where multiplicity rates are high. A future HWO coronagraph may have similarly restrictive criteria in reference star selection. From an exhaustive literature review of 95 stars, we identify an initial list of 40 primary and 18 reserve reference star candidates relevant to both the Roman Coronagraph and HWO. We present results from an initial survey of these candidates with high-resolution adaptive optics imaging and speckle interferometry and identify no new companions. We discuss the need for higher-contrast observations to sufficiently vet these reference star candidates prior to Roman Coronagraph observations along with the implications of reference star criteria on observation planning for Roman and HWO.

Abstract The HWO Target Stars and Systems 2025 (TSS25) list is a community-developed catalog of potential stellar targets for the Habitable Worlds Observatory (HWO) in its survey to directly image Earth-sized planets in the habitable zone. The TSS25 list categorizes potential HWO targets into priority tiers based on their likelihood to be surveyed and the necessity of obtaining observations of their stellar properties prior to the launch of the mission. This target list builds upon previous efforts to identify direct imaging targets and incorporates the results of multiple yield calculations assessing the science return of current design concepts for HWO. The TSS25 list identifies a sample of target stars that have a high probability to be observed by HWO (Tiers 1 and 2), independent of assumptions about the mission’s final architecture. These stars should be the focus of community precursor science efforts in order to mitigate risks and maximize the science output of HWO. This target list is publicly available and is a living catalog that will be continually updated leading up to the mission.

NASA is currently developing the Habitable Worlds Observatory (HWO) in response to the recommendations of the 2020 decadal survey. One of the objectives of this mission will be to discover and characterize Earth-like exoplanets residing in the habitable zones of their host stars via reflected-light imaging. In order to ensure success for missions such as HWO, it is imperative to be able to project the impacts of engineering design decisions on potential mission outcomes (or science yields). As we do not yet know the exact demographics of Earth-like exoplanets, nor know of the specific objects that HWO will observe, these projections must be inherently probabilistic. Our past work has demonstrated that scheduling constraints can potentially have a large, and often underestimated, impact on science yield. Here, we refine our previously developed methodology (based on efficient graph searches) for estimating the effects of schedulability on mission yield. We apply this methodology to an analysis of detection observations of Earth-like exoplanets about likely HWO targets. In particular, we explore the deviation between optimal mission yield (computed by maximizing accumulated completeness with no scheduling constraints) and expected mission yield under scheduling constraints.

Habitable Worlds Observatory (HWO) will search for biosignatures from Earth-size exoplanets in the habitable zones of nearby stars. The wavelength range is a critical driver for HWO architecture designs and science return. We evaluate the NUV, Visible, and NIR spectral characterization yields in a large parameter sweep over aperture diameter, optical system throughput, starlight suppression system inner working angle, core throughput, contrast, contrast stability, exozodi brightness and exozodi calibration residual. We also explore discrete options in wavelength cutoff (for the NUV and NIR), spectral resolution, and SNR. We train a Random Forest model on the parameter sweeps and invert it to find regions of architecture space which yield 25 exo-Earths in the visible and indicate which parts of architecture space may best enable NUV and NIR yields.

We present confirmation of HD 143811 AB b, a substellar companion to spectroscopic binary HD 143811 AB through direct imaging with the Gemini Planet Imager (GPI) and Keck NIRC2. HD 143811 AB was observed as a part of the Gemini Planet Imager Exoplanet Survey (GPIES) in 2016 and 2019 and is a member of the Sco-Cen star formation region. The exoplanet is detected $\sim 430$ mas from the host star by GPI. With two GPI epochs and one from Keck/NIRC2 in 2022, we confirm through common proper motion analysis that the object is bound to its host star. We derive an orbit with a semi-major axis of $64 ^{+32}_{-14}$ au and eccentricity ${0.23 ^{+0.24}_{-0.16}}$. Spectral analysis of the GPI $H$-band spectrum and NIRC2 \textit{L'} photometry provides additional proof that this object is a substellar companion. We compare the spectrum of HD 143811 AB b to PHOENIX stellar models and Exo-REM exoplanet atmosphere models and find that Exo-REM models provide the best fits to the data. From the Exo-REM models, we derive an effective temperature of $1042^{+178}_{-132}$ K for the planet and translate the derived luminosity of the planet to a mass of $5.6 \pm 1.1~M_\textrm{Jup}$ assuming hot-start evolutionary models. HD 143811 AB b is the first directly imaged planet around a binary that is not on an ultra-wide orbit. Future characterization of this object will shed light on the formation of planets around binary star systems.

HD~143811~AB is the host star to the directly imaged planet HD~143811~AB~b, which was recently discovered using data from the Gemini Planet Imager and Keck NIRC2. A member of the Sco-Cen star-forming region with an age of $13 \pm 4$ Myr, HD~143811~AB is somewhat rare among hosts of directly imaged planets as it is a close stellar binary, with an $\sim$18 day period. Accurate values for the orbital and stellar parameters of this binary are needed to understand the formation and evolutionary history of the planet in orbit. We utilize archival high-resolution spectroscopy from FEROS on the MPG/ESO 2.2-meter telescope to fit the orbit of the binary, and combine with unresolved photometry to derive the basic stellar properties of the system. From the orbit, we derive precise values of orbital period of $18.59098 \pm 0.00007$ days, and mass ratio of $0.885 \pm 0.003$. When combined with stellar evolutionary models, we find masses of both components of $M_A = 1.30^{+0.03}_{-0.05}$ M$_\odot$ and $M_B = 1.15^{+0.03}_{-0.04}$ M$_\odot$. While the current data are consistent with the planet and stellar orbits being coplanar, the 3D orientations of both systems are currently poorly constrained, with additional observations required to more rigorously test for coplanarity.

Abstract Building off the foundation of a physics-based end-to-end model for event-based vision sensors (EVS) observing resident space objects (RSOs), we apply new techniques to model realistic low-light sensor noise. While previous approaches simulate memorized current leakage and apply temporal noise models, our methods improve on these approaches and additionally account for current-following noise as an event source. These improvements are key components for accurate event-generating simulators which can advise requirements and concepts of operations for dedicated event-based Space Domain Awareness (SDA) architectures. The EVS pixel’s independent and asynchronous recording of changes in photocurrent produces data with high temporal resolution and dynamic range making it an attractive technology for SDA. EVS are particularly appealing as a space-based payload because of their sparse data output reducing the need for downlink, computational, and power resources. However, truth data is limited for space-based architectures. Therefore, simulation of the underlying physics is particularly important. Our physics-based end-to-end model now includes noise based on induced photocurrent to generate simulated events closer to known truth. We introduce a new Poisson-based method to model the noise generated by the temporal variation of the dark current and a method to tune high-frequency white noise on the induced photocurrent to model the noise on signals above the dark current. These techniques demonstrably improve EVS noise modeling by closely matching observed event rate and polarity behavior, moving EVS one step closer to operational space-based SDA usage.

Linear methods are ubiquitous for control and estimation problems. In this work, we present a number of tensor operator norms as a means to approximately bound the error associated with linear methods and determine the situations in which that maximum error is encountered. An emphasis is placed on induced norms that can be computed in terms of matrix or tensor eigenvalues associated with coefficient tensors from higher-order Taylor series. These operator norms can be used to understand the performance and range of applicability of an algorithm exploiting linear approximations in different sets of coordinates. We examine uses of tensor operator norms in the context of linear and higher-order rendezvous guidance and to present a unified treatment of nonlinearity indices for dynamic systems. Tensor norm computations can offer insights into these problems in one to two orders of magnitude less time than similarly accurate sampling methods while providing more general understanding of the error performance of linear or higher-order approximations.

This paper presents an analytical framework for optimizing refueling strategies for space missions using electric propulsion assuming the availability of in-space refueling stations. The authors derive analytical expressions for key performance metrics, including normalized payload and structure mass, firing time ratio, and specific propellant consumption. They demonstrate that an evenly distributed refueling sequence maximizes the payload mass and that the optimal specific impulse decreases as the number of refueling stations increases. Additionally, the authors extend the concept of the Stuhlinger characteristic velocity to incorporate refueling. Finally, an optimization problem is formulated to determine the ideal refueling sequence that maximizes payload under constraints on the mission time within practical mission constraints. Using the SMART-1 mission as a case study, the authors illustrate the potential of their refueling optimization approach to significantly increase payload mass and reduce specific propellant consumption at the expense of a slightly longer mission time.

Abstract Directly imaged substellar companions with well-constrained ages and masses serve as vital empirical benchmarks for planet formation and evolution models. Potential benchmark companions can be identified from astrometric accelerations of their host stars. We use Gaia DR3 and Hipparcos astrometry to identify 166 northern hemisphere stars with astrometric accelerations consistent with a substellar companion between 0 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover> <mml:mrow> <mml:mo>.</mml:mo> </mml:mrow> <mml:mrow> <mml:mtext>″</mml:mtext> </mml:mrow> </mml:mover> </mml:math> 5 and 1″. For this accelerating sample we identify young stars using Apache Point Observatory/ARCES spectra and TESS light curves. From spectroscopic screening of the sample, we measure ages for 24 stars with detectable amounts of lithium, place lower age limits on 135 stars with lithium nondetections, and measure ages from <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mi>R</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>H</mml:mi> <mml:mi>K</mml:mi> </mml:mrow> <mml:mrow> <mml:mo accent="true">′</mml:mo> </mml:mrow> </mml:msubsup> </mml:math> for 34 stars. A total of 129 stars have TESS light curves, from which we measure ages for 20 stars with rotation rates &lt;15 days, and we identify three eclipsing binaries. We present median ages and confidence intervals of age posteriors for the entire sample and discuss how the overall age distribution of our sample compares to a uniform star formation rate in the solar neighborhood. We identify 47 stars with median ages &lt;2 Gyr, 31 stars with median ages &lt;1 Gyr, and 14 stars with median ages &lt;0.5 Gyr, making them high-priority targets for direct imaging follow-up.

There are a number of possible mitigation strategies that have been identified in the event a hazardous asteroid is discovered. NASA’s DART mission recently demonstrated the kinetic impactor technique [1]. The gravity tractor (GT) is attractive as the next technology for demonstration since other techniques may be prohibited by cost and legality [2]. A GT demonstration mission would align with NASA’s goal to "develop preliminary mission designs for future NEO deflection mission campaigns” [3]. Here, we present the design of a mission that would demonstrate a GT by changing the orbit of the secondary in an asteroid binary system.The GT concept for deflecting asteroids involves bringing a spacecraft near an asteroid and controlling the spacecraft so that the asteroid’s orbit is altered by the spacecraft’s gravity [4]. This slow-pull mitigation strategy can achieve greater precision in an asteroid’s post-deflection orbit than impulsive mitigation techniques. GT also has the benefits of being agnostic to the material properties of the asteroid and not requiring contact between the spacecraft and asteroid. A GT may be used as the “primary” mitigation technique for hazardous asteroids that are found sufficiently far in advance of their Earth impact dates, or as a “secondary” mitigation technique applied after a “primary” impulsive technique to ensure the avoidance of gravitational keyholes. Inspired by the success of the DART mission, we are studying whether GTs will be more easily tested in a binary asteroid system in the same way that kinetic impactors are: a small velocity change on the order of what would be necessary in a real emergency is more easily detected and measured on an asteroid satellite's orbit than it is on a single asteroid’s heliocentric orbit [5]. We report on the design of a GT demonstration mission to a binary asteroid system. We identify three main goals that a GT mission to a binary asteroid should achieve: (1) guide and navigate the spacecraft to the vicinity of the secondary and precisely control its relative position (within a few body radii), (2) measure the change in the secondary’s orbit due to the GT, (3) demonstrate long-duration tractoring operations in close proximity to the asteroid. We present mission requirements needed to achieve these mission goals. These requirements are used to define a concept of operations for a binary asteroid system “characterization phase” and “tractor phase,” which would lead to a measurable deflection of the secondary within a 12-month timeframe for asteroid proximity operations. We present the mission design and baseline payload that would meet these investigation requirements. In sum, this report outlines a demonstration mission of a GT at reasonable cost that will accomplish NASA’s goal of demonstrating a slow-pull asteroid deflection technique. References[1] Chabot, N., et al. (2024). Planet. Sci. J. 5 49[2] Abell, P. and Frazier (2021). Planetary Defense Missions: Rapid Mission Architecture Study. Planetary Science Decadal Survey: Mission Concept Study Report.[3] NASA Planetary Defense Strategy and Action Plan (2023). NASA. https://go.nasa.gov/3UO2mmt[4] Lu, E. T. and Love, S. G. (2005). Nature, 438, 177–178.[5] Merrill, C., et al., Planetary Defense Conference 2025.

Estimating the exoplanet scientific productivity of the Habitable Worlds Observatory requires estimating science exposure times. From exoplanet yields to spectral retrievals, exposure times are at the heart of our understanding of the capabilities of this future mission. As such, ensuring accuracy and consistency between different exposure time calculators (ETCs) is critical. We summarize the efforts of the Exoplanet Science Yield sub-Working Group's ETC Calibration Task Group, which conducted a calibration study from March 4 to June 30 of 2024. We compare three commonly-used coronagraphic exposure time calculators. We find that the ETCs use a broad variety of differing methods, assumptions, and inputs that produce variation in the final exposure times at the ~60% level. The causes for the disagreement have largely been identified, flagged for further development efforts, and in some cases retired since the conclusion of this effort. We expect that addressing the flagged efforts will bring the ETCs to within better than ~30% agreement.

In Cislunar space, spacecraft are able to exploit naturally periodic orbits, which provide operational reliability. However, these periodic orbits only exist in a limited volume. Enabled by low-thrust propulsion, spacecraft can produce a greater number of periodic trajectories in Cislunar space. We describe a methodology for producing mass-optimal trajectories that enforce periodic structure in the circular-restricted three body problem and study the thrust-limited reachable set around a reference trajectory. In this study, we find that the thrust-limited mass-optimal reachable set is a superset of the energy-limited energy-optimal reachable set in the xy-plane.

This paper presents a comprehensive framework for optimizing refueling strategies for space missions utilizing electric propulsion assuming the availability of in-space refueling stations. We derive analytical expressions for key performance metrics, including normalized payload and structure mass, firing time ratio, and specific propellant consumption. We demonstrate that an evenly distributed refueling sequence maximizes the payload mass and that the optimal specific impulse decreases as the number of refueling stations increases. Additionally, we extend the concept of the Stuhlinger characteristic velocity to incorporate refueling. Finally, an optimization problem is formulated to determine the ideal refueling sequence that maximizes payload under constraints on the mission time within practical mission constraints. Using the SMART-1 mission as a case study, we illustrate the potential of our refueling optimization approach to significantly increase payload mass and reduce specific propellant consumption at the expense of a slightly longer mission time.

A Turn-and-Burn maneuver is a continuous-high-thrust trajectory. This maneuver utilizes Hamilton-Jacobi-Bellman time optimality to achieve a minimum time solution. Where previous investigations into the viability of a Turn-and-Burn maneuver assume some unknown propulsive capability and sought minimum time solutions, this investigation explores the premise of using Nuclear Thermal Propulsion in a Turn-and-Burn Style maneuver. With larger upfront mass costs of Nuclear Thermal Propulsion as opposed to chemical propulsion systems, significant savings are to be had operating a smaller NTP engine continuously rather than a large one impulsively. While the specific impulse of current NTP technology is still too low for interplanetary Turn-and-Burn maneuvers, cis-lunar spacecraft present a unique opportunity to exploit the savings of a Turn-and-Burn style maneuver. Specifically, we find that a turn and burn maneuver combined with an NTP system can reduce transfer times to Lunar capture. This paper presents trajectory optimization for this maneuver, along with system performance results for a range of thrust limits and transfer times.

In this work, we investigate trajectories that require thrust to maintain periodic structure in the circular restricted three-body problem (CR3BP). We produce bounds in position and velocity space for the energy-constrained reachable set of initial conditions. Our trajectories are energy-optimal and analyzed via linear analysis. We provide validation for our technique and analyze the cost of deviating in various directions to the reference. For our given reference, we find that it is relatively expensive to decrease perilune distance for orbits in the Earth-Moon system.

The imaging search for exoplanets is mainly limited by quasi-static speckle noise that have lifetimes between milliseconds and hours. Attempts to remove this noise using post-processing by building a point spread function (PSF) model from diversity in time, wavelength, and so-forth are limited to a small improvement due to the evolution of the noise along these same axes. The Calibration 2 (CAL2) system, being built by an international team, is a National Research Council of Canada (NRC) funded facility-class focal plane wavefront sensor for the Gemini Planet Imager 2 (GPI2) upgrade. The project consists of a complete rebuild of the GPI calibration (CAL) system. Based on the self-coherent camera concept and the FAST focal plane mask, a fraction of the near-infrared (NIR) science bandpass is extracted using a new dichroic wheel to perform focal plane wavefront sensing, with the goal to do science while also improving the contrast for the GPI2 IFS, up to a factor of 100x on bright stars. The project is at the final design review stage, and construction is expected to start summer/fall 2024, with assembly late fall 2024, and shipping to the Gemini North observatory middle of 2025.

The Gemini Planet Imager (GPI) is a high-contrast imaging instrument designed to directly detect and characterise young, Jupiter-mass exoplanets. After six years of operation at the Gemini South Telescope in Chile, the instrument is being upgraded and moved to the Gemini North Telescope in Hawaii as GPI 2.0. Several improvements have been made to the adaptive optics (AO) system as part of this upgrade. This includes replacing the current Shack-Hartmann wavefront sensor with a pyramid wavefront sensor (PWFS) and a custom EMCCD. These changes will increase GPI’s sky coverage by accessing fainter targets, improving corrections on fainter stars and allowing faster and ultra-low latency operations on brighter targets. The PWFS subsystem was independently built and tested to verify its performance before being integrated into the GPI 2.0 instrument. This paper will present the pre-integration performance test results, including pupil image quality, throughput and linearity without modulation.

Linear methods are ubiquitous for control and estimation problems. In this work, we present a number of tensor operator norms as a means to approximately bound the error associated with linear methods and determine the situations in which that maximum error is encountered. An emphasis is placed on induced norms that can be computed in terms of matrix or tensor eigenvalues associated with coefficient tensors from higher-order Taylor series. These operator norms can be used to understand the performance and range of applicability of an algorithm exploiting linear approximations in different sets of coordinates. We examine uses of tensor operator norms in the context of linear and higher-order rendezvous guidance, coordinate selection for a filtering measurement model, and to present a unified treatment of nonlinearity indices for dynamical systems. Tensor norm computations can offer insights into these problems in one to two orders of magnitude less time than similarly accurate sampling methods while providing more general understanding of the error performance of linear or higher-order approximations.

In preparation for the operational phase of the Nancy Grace Roman Space Telescope, NASA has created the Coronagraph Community Participation Program (CPP) to prepare for and execute Coronagraph Instrument technology demonstration observations. The CPP is composed of 7 small, US-based teams, selected competitively via the Nancy Grace Roman Space Telescope Research and Support Participation Opportunity, members of the Roman Project Team, and international partner teams from ESA, JAXA, CNES, and the Max Planck Institute for Astronomy. The primary goals of the CPP are to prepare simulation tools, target databases, and data reduction software for the execution of the Coronagraph Instrument observation phase. Here, we present the current status of the CPP and its working groups, along with plans for future CPP activities up through Roman’s launch. We also discuss plans to potentially enable future commissioning of currently-unsupported modes.

The Nancy Grace Roman Space Telescope’s Coronagraph Instrument will for the first time demonstrate active wavefront sensing and control for a space-based coronagraph, and may image the first planet in reflected light. The Community Participation Program has been initiated to engage members of the broader scientific community in the preparation for its planned launch in late 2026/early 2027. Here we will present the on-going work of the Data Reduction and Simulations working group, one of the four working groups within the Community Participation Program. The working group is charged with the development of the data reduction and postprocessing pipeline for the on-sky data and the development of a simulation suite to aid in the preparation and planning of Roman Coronagraph observations.

Abstract We present a new method for fitting exoplanet orbits to direct astrometric measurements, using nonlinear batch estimation and nonsingular orbital elements. Our estimation technique is based on the unscented transform, which approximates probability distributions using finite, deterministic sets of weighted sample points. Furthermore, we use Gaussian mixtures to account for the strong nonlinearities in the measurement model. As a fitting basis, we use a set of orbital elements developed specifically for directly observed exoplanets, combining features of the Thiele–Innes constants and the Cohen–Hubbard nonsingular elements. We validate the new method using simulated exoplanet orbits, and we demonstrate its use with real exoplanet data. Compared to state-of-the-art Markov Chain Monte Carlo and Bayesian rejection sampling techniques, the new method is found to give orbit estimates of comparable or higher accuracy but with much faster execution.

The Coronagraphic Instrument onboard the Nancy Grace Roman Space Telescope is an important stepping stone towards the characterization of habitable, rocky exoplanets. In a technology demonstration phase conducted during the first 18 months of the mission (expected to launch in late 2026), novel starlight suppression technology may enable direct imaging of a Jupiter analog in reflected light. Here we summarize the current activities of the Observation Planning working group formed as part of the Community Participation Program. This working group is responsible for target selection and observation planning of both science and calibration targets in the technology demonstration phase of the Roman Coronagraph. We will discuss the ongoing efforts to expand target and reference catalogs, and to model astrophysical targets (exoplanets and circumstellar disks) within the Coronagraph's expected sensitivity. We will also present preparatory observations of high priority targets.

Habitable Worlds Observatory (HWO) will search for biosignatures from Earth-size exoplanets in the habitable zones of nearby stars. The wavelength range for biosignatures used by the HabEx and LUVOIR mission concept studies was 200 nm to 2 microns and, as such, this is a candidate wavelength range for HWO. The visible wavelength range (500-1000 nm) provides for detection of water, oxygen, and Raleigh scattering; the near-ultraviolet is valuable for detection of ozone; and the near-infrared enables detection of carbon dioxide and methane for Earth-like atmospheres. Damiano et al. 2023 showed the significant improvement in spectral retrieval reliability when the NUV and NIR are both used with the visible. However, the challenge of the NUV, in addition to the technological and engineering challenges of starlight suppression in the NUV, is the drop in flux of host stars. In the NIR, the challenge is the geometric access to the habitable zone due to the wavelength dependency of the inner working angle limit of coronagraphs. For these reasons, exoplanet yields are lower in the NUV and NIR than in the visible and some instrument parameters are more critical for improving NUV and NIR yields than others. In this paper we present a new capability for performing a large number of end-to-end yield modeling simulations to enable large, multivariate parameter sweeps. We utilize this capability to calculate the Visible, NIR, and NUV yield sensitivities to the instrument parameters: aperture diameter, coronagraph core throughput, contrast, and inner working angle (IWA). We find that parameter interactions are important in determining yield, the most important of which is the interaction between contrast and IWA, but that the strength of that interaction is different in each of the three wavebands.

The Gemini Planet Imager (GPI) is a dedicated high-contrast imaging facility instrument. After six years, GPI has helped establish that the occurrence rate of Jovian planets peaks near the snow. GPI 2.0 is expected to achieve deeper contrasts, especially at small inner working angles, to extend GPI’s operating range to fainter stars, and to broaden its scientific capabilities. GPI shipped from Gemini South in 2022 and is undergoing an upgrade as part of a relocation to Gemini North. We present the status of the upgrades including replacing the current wavefront sensor with an EMCCD-based pyramid wavefront sensor, adding a broadband low spectral resolution prism, new apodized-pupil Lyot coronagraph designs, upgrades of the calibration wavefront sensor and increased queue operability. Further we discuss the progress of reintegrating these components into the new system and the expected performance improvements in the context of GPI 2.0’s enhanced science capabilities.

The proposed Habitable Worlds Observatory (HWO) aims to study the atmospheres of Earth-like exoplanets with direct imaging. Understanding an individual Earth-like planet could require weeks of observation time split over multiple visits. The mission concept studies that inspired HWO, HabEx and LUVOIR, both suggested that precursor observations, or detecting the planets with indirect methods before the mission’s launch, can significantly reduce the time required per planet and should be a priority. The radial velocity method is currently thought to be the most capable of finding Earth-like exoplanets and has several surveys planned and underway. In this work, we investigate how different designs for HWO can affect the usefulness of precursor science. We focus on how the size of HWO’s field of regard, primarily determined by the pitch requirements, impacts our ability to schedule observations of planets potentially detectable by the current radial velocity surveys. Our yield simulations indicate that the field of regard of HWO can change the number of Earth-like exoplanets that can be directly imaged three times by up to 34%.

Dynamic completeness–the probability of detecting an exoplanet on the ith observation of a particular target star–is an invaluable tool for exoplanet mission simulation and analysis. The evaluation of this quantity requires the marginalization of the propagation of a particular sample of planetary parameters. This process is either approximated via Monte Carlo, or by a much coarser approximation that assumes a near-constant value for the dynamic completeness after some characteristic ‘breaktime’ after the initial observation. The former approach is computationally costly, whereas the latter approach is frequently not sufficiently accurate for simulating realistic observing scenarios, and, depending on the population of planets being investigated, the breaktime may actually be longer than the mission duration. Here, we discuss alternative techniques for computing dynamic completeness, including a semi-analytical technique for evaluating the conditional density functions of parameters required to compute dynamic completeness at arbitrary points in time.

In the search for life in our galaxy, and for understanding the origins of our solar system, the direct imaging and characterization of Earth-like exoplanets is key. In a step towards achieving these goals, the Superluminous Tomographic Atmospheric Reconstruction with Laser-beacons for Imaging Terrestrial Exoplanets (STARLITE) mission uses five CubeSats in a highly elliptical orbit as artificial guide stars to enable tomographic reconstruction of the atmosphere for extreme multi-conjugate adaptive optics (MCAO). Through the use of current and next-generation extremely-large ground-based telescopes, the STARLITE constellation at its ∼350,000 km apogee can provide brighter than -10 magnitude artificial guide stars from a 10 cm launching telescope in a sub-arcminute field of view for up to an hour. Careful selection and design of the ∼760 nm on-board laser will allow O₂ detection and characterization of exoplanet atmospheres. At a size of 12U, each satellite weighs only 19 kg and utilizes mostly commercially available off-the-shelf components to keep costs per satellite around $2M. In this paper, we will present the satellite mission concept and early system design for the STARLITE constellation.

The Gemini Planet Imager 2.0 (GPI 2.0) is an upgrade to the original GPI, an instrument for directly imaging exoplanet systems, which is being moved to the Gemini North telescope atop Mauna Kea, Hawaii. Major changes involve improved coronagraph designs and upgrading the adaptive optics (AO) system with a new pyramid wavefront sensor (PWFS). The addition of these new components require revised models for evaluating the performance and understanding the limitations of the system. This in turn helps us inform the broader GPI 2.0 science goals. We run end-to-end AO simulations, to assess the performance of GPI 2.0 AO under typical atmospheric conditions on Mauna Kea. We use these simulations to help us determine operating parameters such as the limiting stellar magnitude, maximum Strehl ratio, and the contrast achieved by the joint AO-coronagraph system before speckle-suppression. This information will be used to predict the science performance on a range of targets and design observing strategies.

The Gemini Planet Imager (GPI) is a high contrast imaging instrument that aims to detect and characterize extrasolar planets. GPI is being upgraded to GPI 2.0, with several subsystems receiving a re-design to improve its contrast. To enable observations on fainter targets and increase performance on brighter ones, one of the upgrades is to the adaptive optics system. The current Shack-Hartmann wavefront sensor (WFS) is being replaced by a pyramid WFS with an low-noise electron multiplying CCD (EMCCD). EMCCDs are detectors capable of counting single photon events at high speed and high sensitivity. In this work, we characterize the performance of the HNü 240 EMCCD from Nüvü Cameras, which was custom-built for GPI 2.0. Through our performance evaluation we found that the operating mode of the camera had to be changed from inverted-mode (IMO) to non-inverted mode (NIMO) in order to improve charge diffusion features found in the detector’s images. Here, we characterize the EMCCD’s noise contributors (readout noise, clock-induced charges, dark current) and linearity tests (EM gain, exposure time) before and after the switch to NIMO.

Given a known parent object, we determine the epoch and velocity distribution of an orbital break-up given unassociated observations of the debris cloud positions at multiple times. Using a tentative guess of the break-up time, we solve Lambert’s problem to determine an initial velocity distribution for each debris cloud observation. Agreement of proposed initial velocity distributions depends on the assumed break-up time. We use maximal mean discrepancy in a reproducing kernel Hilbert space to quantify the difference between tentative initial velocity distributions, and optimize this metric to determine the time of break-up.

Contact binary asteroids are ubiquitous in the solar system: the Kuiper belt, main belt, and near-Earth populations all house these complex aggregates. Although contact binaries account for up to 30% of small bodies in the solar system, the formation of one has yet to be observed. We present a preliminary mission design to create a contact binary asteroid and observe its formation using a binary NEO system, a kinetic impactor, and an observer spacecraft. Not only does this mission address an important gap in planetary science, it also serves the planetary defense community: it will further demonstrate planetary defense technology to provide unique observation opportunities. A binary system offers a convenient natural laboratory for this mission, as the ability to form a contact binary using a kinetic impactor depends greatly on the size of the target and the proximity to its parent body. From among all known binary near-Earth objects, binary asteroid system (350751) 2002 AW was chosen for this case study. A spacecraft can achieve rendezvous with this system from low-Earth orbit with a cheap total ΔV ≈ 4.3 km/s. A pair of spacecraft launch on the same launch vehicle and separate before asteroid impact. The two spacecraft are (1) an impactor that has been adapted from the DART spacecraft and (2) an observer spacecraft that will rendezvous with the binary system and observe the creation of the contact binary. The spacecraft impact must be designed such that it redirects the secondary into a collision course with the primary while not catastrophically disrupting the target asteroid. Impact parameters such as angle of impact, catastrophic disruption limit, and the β factor have been considered. Among other design decisions, we present our target-selection methodology, launch-vehicle considerations, and launch opportunities.