The Roman Space Telescope will have the first advanced coronagraph in space, with deformable mirrors (DMs) for wavefront control (WFC), low-order wavefront sensing and maintenance, and a photon-counting detector. It is expected to be able to detect and characterize mature, giant exoplanets in reflected visible light. Over the past decade, the performance of the coronagraph in its flight environment has been simulated with increasingly detailed diffraction and structural/thermal finite-element modeling. With the instrument now being integrated in preparation for launch within the next few years, the present state of the end-to-end modeling, including the measured flight components such as DMs, is described. The coronagraphic modes, including characteristics most readily derived from modeling, are thoroughly described. The methods for diffraction propagation, WFC, and structural and thermal finite-element modeling are detailed. The techniques and procedures developed for the instrument will serve as a foundation for future coronagraphic missions, such as the Habitable Worlds Observatory.
The Nancy Grace Roman Space Telescope (“Roman”) was prioritized by the 2010 Decadal Survey in Astronomy & Astrophysics and is NASA’s next flagship observatory. Launching no earlier than 2026, Roman will explore the nature of dark energy, as well as expand the census of exoplanets in our galaxy via microlensing. Roman will also demonstrate key technology needed to image and spectrally characterize extra-solar planets. Roman’s large field of view, agile survey capabilities, and excellent stability enable these scientific objectives, yet present unique challenges for the design, test, and verification of its optical system. The Roman optical system comprises an optical telescope assembly (OTA) and two instruments: the primary science wide-field instrument (WFI) and a technology demonstration coronagraph instrument (CGI), and the instrument carrier (IC), which meters the OTA to each instrument. This paper presents a status of the optical system hardware as it begins integration and test (I&T), as well as describes key optical test, alignment, and verification activities as part of the I&T program.
The Nancy Grace Roman Space Telescope is NASA’s flagship astrophysics mission planned for launch in 2026. The Coronagraph Instrument (CGI) on Roman will demonstrate the technology for direct imaging and spectroscopy of exoplanets around nearby stars. It will work with the 2.4-meter diameter telescope to achieve starlight suppression and point source detection limits that are 2–3 orders of magnitude deeper than previous space-based and groundbased coronagraphs by using active wavefront control with deformable mirrors. CGI has passed its Critical Design Review (CDR) in April of 2021, and System Integration Review (SIR) in June of 2022. We describe the status of CGI’s development and plans for the upcoming integration and testing phase.
The Habitable Exoplanet Observatory Mission (HabEx) is one of four missions under study for the 2020 Astrophysics Decadal Survey. Its goal is to directly image and spectroscopically characterize planets in the habitable zone around nearby sun-like stars. Additionally, HabEx will perform a broad range of general astrophysics science enabled by 115 to 1700 nm spectral range and 3x3 arc-minute FOV instruments. Critical to achieving its science goals is a large, ultra-stable UV/Optical/Near-IR (UVOIR) telescope. The baseline HabEx telescope is a 4-meter off-axis unobscured three-mirroranastigmatic, diffraction limited at 400 nm with wavefront stability on the order of a few 10s of picometers. This paper summarizes the opto-mechanical design of the HabEx baseline optical telescope assembly, including a discussion of how science requirements drive the telescope’s specifications, and presents analysis that the baseline telescope structure meets its specified tolerances.
The Habitable-Zone Exoplanet Observatory Mission (HabEx) is one of four large missions under review for the 2020 astrophysics decadal survey. Its goal is to directly image and spectroscopically characterize planetary systems in the habitable zone around nearby Sun-like stars. In addition, HabEx will perform a broad range of general astrophysics science enabled by a 115- to 1700-nm spectral range and 3 × 3 arcminute field of view. Critical to achieving its science goals, HabEx requires a large, ultrastable UV/optical/near-IR telescope. Using science-driven systems engineering, HabEx specified its baseline telescope to be a 4-m off-axis, unobscured three-mirror anastigmatic architecture with diffraction-limited performance at 400 nm, and wavefront stability on the order of a few tens of picometers. We summarize the systems-engineering approach to the baseline telescope assembly’s optomechanical design, including a discussion of how science requirements drive the telescope’s specifications. We also present structural thermal optical performance analysis showing that the baseline telescope structure meets its specified tolerances. We report new and updated analysis that is not in the HabEx final report.
Since the 2010 Decadal Survey, the technologies needed for direct imaging of exoplanets advanced significantly. NASA investment in these technologies, prioritized in the 2010 Decadal Survey, have ripened to a maturity to enable direct imaging of earthlike exoplanets. For the first time since the discovery of exoplanets, a direct imaging mission can be conceived to start in less than ten years, possibly as soon as five years.
The HabEx Observatory Concept design utilizes technologies that are state of the art or near to state of the art with clear paths of development. The philosophy of the design favors as high a Technology Readiness Level (TRL) as possible to minimize risk. We discuss the HabEx technology challenges and assess the TRL expected by the submission of the Final Report in 2019. Many of the enabling technologies are at, or expected to be at, TRL 5 by 2019, and the remaining technologies are at TRL 4. We update the technology maturity roadmap with technology advances in the past year and expand it to include an Architecture option which is a 3.2 m diameter on-axis segmented aperture with a starshade only. The starshade suppresses starlight before it enters the telescope, allowing the telescope optical performance and stability to be significantly looser than for a coronagraph, thus enabling a segmented primary mirror design that can meet stability requirements with minimal advancement from the state of the art. We assess the exoplanet-driven technologies of HabEx, including starshades, coronagraphs, deformable mirrors, wavefront control, 4 m aperture mirrors, jitter mitigation, segmented mirror stability, and low-noise detectors.
The Habex study, commissioned by NASA in preparation for the 2020 Decadal Survey, is evaluating a 4 meter space telescope for high contrast imaging and spectral characterization of extrasolar terrestrial planets. Its off-axis configuration, active structural metrology, and low-disturbance pointing control provide an optimal system for coronagraphs. We present predictions of the Habex performance using a charge 6 vortex coronagraph that have been obtained using numerical modeling techniques developed for the WFIRST coronagraph. The models include realistic optical surface and polarization-induced aberrations, pointing jitter, and thermally-induced wavefront variations. Wavefront control using dual deformable mirrors is simulated to create a dark, high-contrast hole around the star. The results show that current technologies can closely approach the Habex performance goals, and with some additional development in key areas (e.g., deformable mirror surface quality, low-polarization coatings, etc.) over the next few years they should reliably meet them.
The HabEx study has developed a baseline concept for a 4 m aperture next generation space telescope operating from the ultraviolet to the infrared, capable of compelling general astrophysics and exoplanet science. HabEx carries four instruments, a UV spectrometer/imager (UVS) together with a general purpose astrophysics camera/spectrograph (HWC) and for exoplanet work, a coronagraph and a starshade. UVS reaches down to 115 nm with resolution up to 60,000 and a 3’x3’ field of view. HWC operates between 370 nm and 1800 nm, again with a 3’x3’ field of view; the spectral resolution is 1000 and it carries a suite of science filters. The telescope is capable of tracking both deep space and solar system objects. The coronagraph enables observations and spectroscopy at up to R=140 with instantaneous 20% bandwidth between wavelengths of 450 and 1800 nm and is intended to be used in a survey mode. However, it also backs up most of the functionality of the accompanying starshade instrument which will have superior performance for spectroscopy. The 52 m diameter starshade flies 76,600 km from the telescope and at that range has a broadband suppression of the starlight between 300 and 1000 nm. A single observation at 108% bandwidth covers a very wide spectral band at a resolution up to 140. Both coronagraph and starshade are equipped with integral field spectrometers to enable simultaneous spectroscopy of exoplanets within the field of view. This paper details the design of the telescope, the four science instruments and associated optical systems.
The Habitable Exoplanet Observatory Mission (HabEx) is one of four missions under study for the 2020 Astrophysics Decadal Survey. Its goal is to directly image and spectroscopically characterize planetary systems in the habitable zone around nearby sun-like stars. Additionally, HabEx will perform a broad range of general astrophysics science enabled by 100 to 2500 nm spectral range and 3 × 3 arc-minute FOV. Critical to achieving its the HabEx science goals is a large, ultrastable UV/Optical/Near-IR (UVOIR) telescope. The baseline HabEx telescope is a 4-meter off-axis unobscured threemirror- anastigmatic, diffraction limited at 400 nm with wavefront stability on the order of a few 10s of picometers. This paper summarizes the opto-mechanical design of the HabEx baseline optical telescope assembly, including a discussion of how science requirements drive the telescope’s specifications, and presents analysis that the baseline telescope structure meets its specified tolerances.
The Habitable-Exoplanet Observatory (HabEx) is a candidate flagship mission being studied by NASA and the astrophysics community in preparation of the 2020 Decadal Survey. The first HabEx mission concept that has been studied is a large (~4m) diffraction-limited optical space telescope, providing unprecedented resolution and contrast in the optical, with extensions into the near ulttraviolet and near infrared domains. We report here on our team’s efforts in defining a scientifically compelling HabEx mission that is technologically executable, affordable within NASA’s expected budgetary envelope, and timely for the next decade. We also briefly discuss our plans to explore less ambitious, descoped missions relative to the primary mission architecture discussed here.
The Habitable Exoplanet Imaging Mission (HabEx) Study is one of four studies sponsored by NASA for consideration by the 2020 Decadal Survey Committee as a potential flagship astrophysics mission. A primary science directive of HabEx would be to image and characterize potential habitable exoplanets around nearby stars. As such, the baseline design of the HabEx observatory includes two complimentary starlight suppression systems that reveal the reflected light from the exoplanet – an internal coronagraph instrument, and an external, formation-flying starshade occulter. In addition, two general astrophysics instruments are baselined: a high-resolution ultraviolet spectrograph, and an ultraviolet, visible, and near-infrared (UV/Vis/NIR), multi-purpose, wide-field imaging camera and spectrograph. In this paper, we present the baseline architecture concept for a 4m HabEx telescope, including key requirements and a description of the mission and payload designs.
KEYWORDS: Exoplanets, Solar system, Astrophysics, UV optics, Galactic astronomy, Space telescopes, Near ultraviolet, Near infrared, Planets, Scientific research
The Habitable-Exoplanet Imaging Mission (HabEx) is a candidate flagship mission being studied by NASA and the astrophysics community in preparation of the 2020 Decadal Survey. The HabEx mission concept is a large (~4 to 6.5m) diffraction-limited optical space telescope, providing unprecedented resolution and contrast in the optical, with extensions into the near UV and near infrared domains.
The primary goal of HabEx is to answer fundamental questions in exoplanet science, searching for and characterizing potentially habitable worlds, providing the first complete “family portraits” of planets around our nearest Sun-like neighbors and placing the solar system in the context of a diverse set of exoplanets.
At the same time, HabEx will enable a broad range of Galactic, extragalactic, and solar system astrophysics, from resolved stellar population studies that inform the stellar formation history of nearby galaxies, to characterizing the life cycle of baryons as they flow in and out of galaxies, to detailed studies of bodies in our own solar system.
We report here on our team’s efforts in defining a scientifically compelling HabEx mission that is technologically executable, affordable within NASA’s expected budgetary envelope, and timely for the next decade. In particular, we present architectures trade study results, quantify technical requirements and predict scientific yield for a small number of design reference missions, all with broad capabilities in both exoplanet science and cosmic origins science.
This research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
HabEx Architecture A is a 4m unobscured telescope mission concept optimized for direct imaging and spectroscopy of potentially habitable exoplanets, and also enables a wide range of general astrophysics science. The exoplanet detection and characterization drives the enabling core technologies. A hybrid starlight suppression approach of a starshade and coronagraph diversifies technology maturation risk. In this paper we assess these exoplanet-driven technologies, including elements of coronagraphs, starshades, mirrors, jitter mitigation, wavefront control, and detectors. By utilizing high technology readiness solutions where feasible, and identifying required technology development that can begin early, HabEx will be well positioned for assessment by the community in 2020 Astrophysics Decadal Survey.
We present an update to our paper from last year on the design and capabilities of the Ultraviolet Spectrograph (UVS) instrument on the Habitable Exoplanet Observatory (HabEx) concept. The design has been matured to be both more compact and serviceable while delivering all the required capabilities that the original Science Traceability Matrix (STM) demanded. Since last year the project has begun design considerations for a second Architecture for the overall mission, and we present design changes that optimize the performance of the instrument when combined with that Optical Telescope Assembly (OTA). Results of a start at a community driven Design Reference Mission (DRM) are also included to illustrate the anticipated performance of the instrument.
The Habitable Exoplanet Imaging Mission (HabEx) is a concept for a mission to directly image planetary systems around Sun-like stars and to perform general astrophysics investigations being studied as part of a number of mission concepts for the upcoming 2020 Astrophysics Decadal Survey. HabEx would help assess the prevalence of habitable planets in our galaxy, searching in particular for potential biosignatures in the atmospheres of planets in habitable zones. More generally, HabEx would image our neighboring solar systems and characterize the variety of planets that inhabits them. Its direct imaging capability would also enable the mission to study the structure and evolution of debris disks around nearby stars, and their dynamical interaction with planets. Additionally, it will explore a number of more general astrophysics phenomena in our solar system, galaxy, and beyond, in the UV through NIR range. The exoplanet science goals lead to a mission concept with requirements for high contrast imaging and the continuous spectral coverage. The baseline for HabEx is a 4-meter diameter off-axis telescope designed to both search for habitable planets and perform general astrophysics observations, possibly combined with a starshade. In this paper, the initial flight system design for both the telescope and the starshade are presented, focusing on the key and driving requirements and subsystems, as well as the trajectory and station keeping and formation flying technique. Furthermore, some of the initial design trades undergone are described, as well as the key challenges and enablers. Finally, some of the future design and architecture trades to be performed within the flight systems as part of the continuing effort in the HabEx study are discussed.
HabEx is one of four candidate flagship missions being studied in detail by NASA, to be submitted for consideration to
the 2020 Decadal Survey in Astronomy and Astrophysics for possible launch in the 2030s. It will be optimized for direct
imaging and spectroscopy of potentially habitable exoplanets, and will also enable a wide range of general astrophysics
science. HabEx aims to fully characterize planetary systems around nearby solar-type stars for the first time, including
rocky planets, possible water worlds, gas giants, ice giants, and faint circumstellar debris disks. In particular, it will
explore our nearest neighbors and search for signs of habitability and biosignatures in the atmospheres of rocky planets
in the habitable zones of their parent stars. Such high spatial resolution, high contrast observations require a large
(roughly greater than 3.5m), stable, and diffraction-limited optical space telescope. Such a telescope also opens up
unique capabilities for studying the formation and evolution of stars and galaxies. We present some preliminary science
objectives identified for HabEx by our Science and Technology Definition Team (STDT), together with a first look at
the key challenges and design trades ahead.
KEYWORDS: Mirrors, Telescopes, Optical design, Space telescopes, Staring arrays, Sensors, James Webb Space Telescope, Infrared telescopes, Observatories, Ray tracing
The WFIRST-AFTA Wide-Field Infrared Survey Telescope TMA optical design provides 0.28-sq°FOV Wide Field Channel at 0.11” pixel scale, operating at wavelengths between 0.76-2.0μm, including a spectrograph mode (1.35-1.95μm.) An Integral Field Channel provides a discrete 3”x3.15” field at 0.15” sampling.
The most recent study of the Wide Field Infrared Survey Telescope (WFIRST) mission is based on reuse of an
existing 2.4m telescope. This study was commissioned by NASA to examine the potential science return and cost
effectiveness of WFIRST by using this significantly larger aperture telescope. We review the science program
envisioned by the WFIRST 2012-2013 Science Definition Team (SDT), an overview of the mission concept, and
the telescope design and status. Comparisons against the previous 1.3m and reduced cost 1.1m WFIRST design
concepts are discussed. A significant departure from past point designs is the option for serviceability and the
geostationary orbit location which enables servicing and replacement instrument insertion later during mission
life. Other papers at this conference provide more in depth discussion of the wide field instrument and the optional
exoplanet imaging coronagraph instrument.
The Wide Field Infrared Survey Telescope (WFIRST) mission concept was ranked first in new space astrophysics
missions by the Astro2010 Decadal Survey, incorporating the Joint Dark Energy Mission payload concept and multiple
science white papers. This mission is based on a space telescope at L2 studying exoplanets [via gravitational
microlensing], probing dark energy, and surveying the near infrared sky. Since the release of the Astro2010 Decadal
Survey, the team has been working with the WFIRST Science Definition Team to refine mission and payload concepts.
We present the current interim reference mission point design of the payload, based on the use of a 1.3m unobscured
aperture three mirror anastigmat form, with focal imaging and slit-less spectroscopy science channels. We also present
the first results of Structural/Thermal/Optical performance modeling of the telescope point design.
We present the start of the ground alignment plan for the SIM Lite Instrument. We outline the integration
and alignment of the individual benches on which all the optics are mounted, and then the alignment of the
benches to form the Science and Guide interferometers. The Instrument has a guide interferometer with only
a 40 arc-seconds field of regard, and 200 arc-seconds of alignment adjustability. This requires each sides of the
interferometer to be aligned to a fraction of that, while at the same time be orthogonal to the baseline defined
by the External Metrology Truss. The baselines of the Science and Guide interferometers must also be aligned
to be parallel.
The start of these alignment plans is captured in a SysML Instrument System model, in the form of activity
diagrams. These activity diagrams are then related to the hardware design and requirements. We finish with
future plans for the alignment and integration activities and requirements.
Main brassboard Michelson interferometer components have been recently developed for the future flight phase
implementations of SIM Lite mission. These brassboard components include two fine steering mirrors, pathlength
modulation and cyclic averaging optics and astrometric beam combiner assembly. Field-independent performance tests
will be performed in a vacuum chamber using two siderostats in retro-reflecting positions and a white light stimulus. The
brightness and color dependence of the angle and fringe tracking performance will be measured. The performance of
filtering algorithms will be tested in a simulated spacecraft attitude control system perturbation. To demonstrate
capability of a dim star observation, the angle and fringe tracking CCD sensors are cooled to -110 C using a cold diode
heat pipe system. The new feed-forward control (angle and path-length) algorithms for the dim star observation will be
tested as well. In this paper, we will report the recent progress toward the integration and performance tests of the
brassboard interferometer.
KEYWORDS: Mirrors, Simulation of CCA and DLA aggregates, Cameras, Camera shutters, Optical alignment, Staring arrays, Interferometry, Metrology, Mechanical engineering, Off axis mirrors
The Astrometric Beam Combiner (ABC) is a critical element of the Space Interferometry Mission (SIM) that
performs three key functions: coherently combine starlight from two siderostats; individually detect starlight for
angle tracking; and disperse and detect the interferometric fringes. In addition, the ABC contains: a stimulus,
cornercubes and shutters for in-orbit calibration; several tip/tilt mirror mechanisms for in-orbit alignment; and
internal metrology beam launcher for pathlength monitoring. The detailed design of the brassboard ABC (which
has the form, fit and function of the flight unit) is complete, procurement of long-lead items is underway, and
assembly and testing is expected to be completed in Spring 2009. In this paper, we present the key requirements
for the ABC, details of the completed optical and mechanical design as well as plans for assembly and alignment.
The Space Interferometry Mission (SIM) is a space-based stellar interferometry instrument, consisting of up to
three interferometers, which will be capable of micro-arc second resolution. Alignment knowledge of the three
interferometer baselines requires a three-dimensional, 14-leg truss with each leg being monitored by an external
metrology gauge. In addition, each of the three interferometers requires an internal metrology gauge to monitor
the optical path length differences between the two sides. Both external and internal metrology gauges are
interferometry based, operating at a wavelength of 1319 nanometers. Each gauge has fiber inputs delivering
measurement and local oscillator (LO) power, split into probe-LO and reference-LO beam pairs. These beams
experience power loss due to a variety of mechanisms including, but not restricted to, design efficiency, material
attenuation, element misalignment, diffraction, and coupling efficiency. Since the attenuation due to these sources
may degrade over time, an accounting of the range of expected attenuation is needed so an optical power margin
can be book kept. A method of statistical optical power analysis and budgeting, based on a technique developed
for deep space RF telecommunications, is described in this paper and provides a numerical confidence level for
having sufficient optical power relative to mission metrology performance requirements.
The Space Interferometry Mission (SIM) is a microarcsecond interferometric space telescope that requires picometer level precision measurements of its truss and interferometer baselines. Single-gauge metrology errors due to non-ideal physical characteristics of corner cubes reduce the angular measurement capability of the science instrument. Specifically, the non-common vertex error (NCVE) of a shared vertex, double corner cube introduces micrometer level single-gauge errors in addition to errors due to dihedral angles and reflection phase shifts. A modified SIM Kite Testbed containing an articulating double corner cube is modeled and the results are compared to the experimental testbed data. The results confirm modeling capability and viability of calibration techniques.
In order to achieve micro-arcsecond astrometry, SIM must make measurements of various optical pathlengths at the picometer level. In this regime of precision, nearly every simplifying assumption in optics must be reexamined as a potential source of systematic error. SIM makes extensive use of physics-based models to predict the form and level of systematic errors affecting instrument performance. Since many of the modeling areas represent new frontiers in optical modeling, the validation of these physical models is a significant challenge that SIM must meet. In the case of the external metrology truss, the model must account for the imperfections in the corner cubes as well as the distance measuring interferometers ("beam launchers"). This model is being validated using the Kite testbed, a 2-D metrology truss with picometer-level accuracy in displacement measurements. We present the model, and the results of the model validation tests on the Kite testbed.
To accomplish micro-arcsecond astrometric measurement, stellar interferometers such as SIM require the measurement of internal optical path length delay with an accuracy of ~10 picometers level. A novel common-path laser heterodyne interferometer suitable for this application was proposed and demonstrated at JPL. In this paper, we present some of the experimental results from a laboratory demonstration unit and design considerations for SIM's internal metrology beam launcher.
Picometer scale optical metrology specifications for the Space
Interferometry Mission require precision calibration functions
involving the optical and orientation characteristics of corner
cube retroreflectors. Accurate knowledge of such parameters as
the index of refraction of the reflective coating, dihedral
between facets, and the orientation of the retroreflector with
respect to the interrogating metrology beam and its polarization
state is critical. Knowledge errors result in optical path
differences that are shown to be on the order of nanometers. These
sensitivities are determined from Zemax-generated models and
measured parameters. Due to the stringent requirements of SIM,
accurate and consistent experimental measurements of corner cube
characteristics are required for improved calibration of mission
metrology systems. Initial dihedral measurements to within 0.05
arcsecond and refractive indices to within 1% are obtained and
integrated into the models.
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