March 31, 2020 Seminar Recording
Title: Method for deriving optical telescope stability specifications for Earth-detecting coronagraphs
Speaker: Bijan Nemati (UAH) Presentation Slides
We present an approach to arrive at wavefront stability requirements for high contrast direct imaging applications. The method begins by setting requirements on the flux ratio noise based on the science objectives (target flux ratio and desired SNR). Next we use a diffraction model to arrive at a coronagraph’s basic performance parameters such as core throughput and contrast. Using these parameters and an analytical model of photometric errors, we propose a method for deriving a basic top level error budget, including allocations for wavefront instability. Next, we use the diffraction model to derive the sensitivity of the given telescope/coronagraph combination to the expected wavefront error instabilities that might be encountered. We describe a simple weighting algorithm that can be the basis of a first-cut set of allocations to each instability mode in a system engineering process. Using this algorithm and the computed sensitivities, we arrive at requirements for stability in each mode. We end by demonstrating the utility of this method for comparing the ability of several monolithic and segmented telescope and coronagraph combinations to detect an exo-Earth at 10 pc.
Title: Exoplanet detection with the LUVOIR coronagraph instrument - Performance evaluation and aberration sensitivity requirements
Speaker: Roser Juanola-Parramon (NASA/GSFC) Presentation Slides
Future space missions such as the Large UV-Optical-Infrared Surveyor (LUVOIR) and the Habitable Exoplanet Observatory (HabEx) require large apertures and coronagraphs with active wavefront control to suppress starlight so that faint planets can be detected and characterized adjacent to their parent star. The Extreme Coronagraph for Living Planet Systems (ECLIPS) is the coronagraph instrument on the LUVOIR Surveyor mission concept, an 8-15-meter segmented telescope. ECLIPS is split into three wavelength channels: UV (200 to 400 nm), optical (400 nm to 850 nm), and NIR (850 nm to 2.0 microns), each equipped with two deformable mirrors for wavefront control, a suite of coronagraph masks, a low-order/out-of-band wavefront sensor, and dedicated imaging cameras and spectrographs.
The Apodized Pupil Lyot Coronagraph (APLC) and the Vector Vortex Coronagraph (VVC) are the baselined mask technologies for ECLIPS. Both mask types enable 10-10 contrast observations in the habitable zones of nearby stars. Their performance depends on active wavefront sensing and control, as well as metrology subsystems to compensate for static and dynamic aberrations. We have simulated the effect of static aberrations induced by segment errors (piston and tip/tilt, among others), secondary mirror misalignment, global low-order wavefront errors, as well as the effects of dynamic aberrations due to segment jitter and segment drift.
Here we present the latest results of the simulation of these effects for the two mask technologies and discuss the achieved contrast for exoplanet detection and characterization after closed-loop wavefront estimation and control algorithms have been applied. With respect to dynamic wavefront aberrations, both designs maintain their target contrast of 1e−10 with segment jitter and drift wavefront error levels of around 32pm and 12pm, respectively. For a 3-sigma detection, the segment jitter and drift required is of the order of 20pm and 7pm, respectively. Finally, we show simulated observations using high-fidelity spatial and spectral input models of complete planetary systems generated with the Haystacks scene framework.
December 16, 2019 Seminar Recording Presentation Slides
Title: The Standard Definitions and Evaluation Team Final Report: A common comparison of exoplanet yield
Speaker: Rhonda Morgan (JPL/Caltech)
The Exoplanet Standard Definition and Evaluation Team (ExSDET) has performed an unbiased exo-earth yield analysis of the LUVOIR and HabEx large mission concepts using a transparent and documented set of common inputs, assumptions and methodologies. The Standards Team established science metrics for yield to allow for a common comparison of the point-designs presented in the final reports: LUVOIR A (15 m on-axis), LUVOIR B (8 m off-axis), HabEx 4H (4 m with coronagraph and starshade), HabEx 4C (4 m with coronagraph only), and HabEx 3.2S (3.2m with starshade only). Yield analysis shows that these concepts can directly image and spectrally characterize earth-like planets in the habitable zone and that each architecture has complementary strengths and provides different quality of science products.
This talk presents an overview of the astrophysical assumptions and inputs, including recent developments such as the results of the LBTI HOSTS survey of exozodical dust brightness and the incorporation of radial velocity occurrence rates and application of theoretical constraints to the SAG-13 exoplanet occurrence rates. The approaches for the two different design reference mission simulation codes is described: Altruistic Yield Optimization (AYO) by Chris Stark and the Exoplanet Open-Source Imaging Mission Simulator (EXOSIMS) by Dmitry Savransky et al. The individual observing scenarios of each concept is delineated and the subsequent yield metrics descripted. The common comparison of LUVOIR to HabEx to the various metrics is presented, including the impact of observation scheduling. The talk concludes with a brief look at the potential impact of precursor knowledge from a potential extreme precision radial velocity instrument.
November 12, 2019 Seminar Recording Presentation Slides
Title: Results from the NASA-Chartered In-Space Assembled Telescope (iSAT) Study: Implications for Future Space Observatories
Speaker: Nick Siegler (NASA ExEP, Jet Propulsion Laboratory/California Institute of Technology)
The recent top recommendation of the National Academies’ Exoplanets Science Strategy Report for NASA to commission a telescope capable of directly imaging exoplanets and conducting reflection spectroscopy opens up the possibility that a large aperture telescope may also be recommended by the 2020 Decadal Survey. While large apertures offer the possibility of greater exoplanets yield the current paradigm of folding large telescope into smaller fairings and deploying them from single launch vehicles also pose the risk of great cost and risk. An alternative to the current paradigm is a combination deployment and assembly in space where key elements of the telescope, its sunshade, and its instruments are architected as individual modules capable of being robotically assembled. Multiple, currently existing, medium-lift commercial launch vehicles would then be used to transport the modules to a space platform and orbit where the assembly and checkout would occur. This talk will present final report findings and recommendations of a NASA Astrophysics Division chartered study whose objective was to assess the cost and risk benefits, if any, of this new paradigm.
May 20, 2019 Seminar Recording
Title: Segmented Space Telescopes for the Search for Life: Key Findings from System-Level Segmented Space Telescope Studies
Speaker: Larry Dewell (Lockheed Martin Space) Presentation Slides
Achieving ultra-stability of large segmented optical systems with integrated coronagraphs, such as envisioned on NASA’s generation-after-next great space-based observatories, involves the integration of high-performance subsystems, including isolation, reaction-cancelling fast steering mirrors, wavefront sensing and control and segment relative position control, to name a few. This presents significant systems engineering and integrated design challenges, and a rigorous approach to system-level modeling is necessary to quantify the performance and assess compliance. In this talk, a comprehensive integrated model of a segmented optical space telescope is described, using the LUVOIR 15-meter architecture as a specific example, including optical sensitivities realistic disturbance sources. Predicted dynamic line-of-sight and wavefront errors during steady-state coronagraph science operations are presented, and preliminary results on the settling time of such errors after a repositioning slew maneuver is examined. With this modeling approach, the technical viability of this LUVOIR architecture is established versus the coronagraph instrument requirements, and important system design implications that were observed are enumerated that have application to other large telescope architectures under the Astro2020 purview.
Speaker: Laura Coyle (Ball Aerospace and Technologies Corp.) Presentation Slides
This presentation documents the key findings from the Ultra-Stable Large Telescope Research and Analysis (ULTRA) study. The contract was awarded to our industry team (Ball Aerospace, Harris Corp., Northrop Grumman Corp. Aerospace Systems, Northrop Grumman Corp. Innovation Systems, SGT and the Space Telescope Science Institute) through the NASA ROSES-17 solicitation, element D.15 – which calls for a one-year system-level engineering design and modeling study for a >10-m class UV/optical/IR segmented-aperture telescope with sub-nanometer wavefront stability.
This challenging stability requirement is driven by the science goal to directly image and characterize exo-Earths with a high contrast coronagraph. Two mission concepts requiring sub-nanometer stability are the Large UV/Optical/Infrared Surveyor (LUVOIR) and the Habitable Exoplanet Observatory (HabEx), both of which are under consideration by the 2020 Astrophysics Decadal Survey. This study augments the work completed by the LUVOIR and HabEx Science and Technology Definition Teams (STDTs) and their NASA center engineering teams by identifying and prioritizing key technologies for near-term development that will result in credible system architectures. While this study uses these mission concepts (especially LUVOIR) to perform specific assessments, the findings are applicable to similar architectures with comparable stability needs.
Our approach is a holistic systems architecture study treating the observatory, telescope and coronagraph as a complete system and considering the impacts of instability in both the temporal and spatial domains. It is guided via the formalism of error budgets, where sub-system allocations are compared to current capabilities, often including trade studies of potential technologies or approaches. Technology gaps are identified where current capabilities will not meet allocations and roadmaps are provided to prioritize and propose a path forward for development of the most urgent technologies.
April 11, 2019
Title: SISTER: Starshade Imaging Simulation Toolkit for Exoplanet Reconnaissance Presentation Slides
Speaker: Sergi Hildebrandt (JPL)
SISTER (Starshade Imaging Simulation Toolkit for Exoplanet Reconnaissance) is a versatile tool aimed at quantifying mission designs with starshade. SISTER allows one to control: (1) the starshade design in use, (2) the exoplanetary system, (3) the optical system (telescope) and (4) the detector characteristics (camera). The simulations may be stored on disk for data analysis, or plotted with its own plotting interface. SISTER is a live, open source project that will continue to grow and support current and future starshade studies
March 13, 2019 Seminar Recording
Title: S5: The Starshade Technology Development Activity
Speaker(s): Phil Willems (NASA ExEP; S5 Deputy Manager) Presentation Slides
In 2016, NASA decided to reorganize its starshade technology development from competitively funded grants into a centralized directed activity, with the goal of closing all starshade technology gaps by driving their core technologies to TRL5. In 2018 NASA’s Astrophysics Division approved the plan for this activity, which is called ‘S5’. We will present a summary of starshade technology, the plan to close the technology gaps, and recent results.
October 29, 2018 Seminar Recording
Title: Architecture for space-based exoplanet spectroscopy in the mid-infrared
Speaker: Joe Green (JPL) presentation slides
Characterizing exo-Earths at wavelength about 10 micron offers many benefits over visible coronagraphy. Apart from providing direct access to a number of significant bio-signatures, direct-imaging in the mid-infrared can provide 1000 times or more relaxation to contrast requirements while greatly shortening the time-scales over which the system must be stable. This in turn enables tremendous relief to optical manufacturing, control and stability tolerances bringing them in-line with current technology state of the art. In this talk, we explore a reference design that co-optimizes a large, segmented, linearized aperture telescope using one-dimensional phase-induced aperture apodization to provide high-contrast imaging for spectroscopic analysis. By rotating about a parent star, the chemical signatures of its planets are characterized while affording additional means for background suppression.
October 5, 2018 Seminar Recording
Title: Terrestrial exoplanet characterization enabled by quasi-random structured-pupil
Speaker: James Breckinridge (Caltech/University of Arizona) Slides
Here we introduce the concept of the structured telescope pupils whose unique diffraction pattern significantly reduces the non-uniform distribution of background radiation. Diffraction patterns from these pupils are compared to the monolithic filled aperture, the classical Cassegrain, the 60-degree symmetry of the hexagonal segments (JWST, E-ELT, etc.). Diffraction “spikes” are reduced by at least 105 . We discuss advantages to spectroscopy, image processing, and observatory operations. We assert that, segment fabrication, alignment and mounting of curved-sided mirrors is not more difficult than fabrication of the classic hexagonal mirror segments.
May 30, 2018
Title: Cost Drivers for Traditional Space Telescope Missions
Speakers: Keith Warfield (NASA/JPL) Slides and Phil Stahl (NASA/MSFC)
Note: the colloquium recording is NASA-internal only, please contact Brendan Crill to request access.
March 1, 2018 Seminar Recording
Title: Stability of Mid-Infrared Detectors for Future Space-based Transit Spectroscopy Measurements
Speaker: Craig McMurtry (Rochester) Presentation Slides
The future space missions that are designed to observe exo-planets using transit spectroscopy, e.g. OST (Origins Space Telescope), will require the detector arrays and their controllers to be stable to < 5 ppm. OST’s MISC (Mid-IR Imager, Spectrometer, Coronagraph) covers the mid-IR range 5 – 38 um. The current baseline includes Si:As and Si:Sb BIB detector arrays to cover the 5-38 um wavelength range. We suggest that long wave HgCdTe, which we have developed, is an attractive alternative for 5-15 um, while Si:As BIB detector arrays would cover out to 27um, and Si:Sb BIB detector arrays are the only alternative that works out to 38 um. We will discuss those three detector technologies and some development that may be needed to reach the required stability. Further, both the Read-Out Integrated Circuit (ROIC) and any associated data acquisition controllers may need to be redesigned for several reasons.
October 24, 2017
Title: Multi-Star Wavefront Control: A Method for Exoplanet Imaging in Multi-Star Systems
Speaker: Ruslan Belikov (NASA/Ames) Presentation Slides
The technology to directly image exoplanets has been steadily advancing for more than a decade. It enables future space missions such as WFIRST, LUVOIR, and HabEx to directly image planets by reflected light and possibly find evidence of life on them. However, many prime multi-star systems are reluctantly omitted from the target lists of missions because mature starlight suppression technology for multi-star systems does not yet exist. Enabling the study of multi-star systems is very important because more than half of Sun-like stars belong to multi-star systems. This includes Alpha Centauri A and B, which would probably be the best target for any direct imaging mission (by a large margin), if it was not a binary.
This talk will cover the science motivation as well as the progress in technology development of Multi-Star Wavefront Control (MSWC), a method to directly image planets and disks in multi-star systems. This method works with almost any coronagraph (or external occulter with a DM) and requires little or no change to existing and mature hardware. Because of the ubiquity of multistar systems, this method potentially broadens the science yield of many missions and concepts such as WFIRST, Exo-C/S, HabEx, LUVOIR, and potentially enables the detection of Earth-like planets (if they exist) around our nearest neighbor star, Alpha Centauri, with a small and low-cost space telescope such as ACESat or Project Blue, in addition to the larger missions.
September 28, 2017
Title: GAIA design considerations and lessons learned
Speaker: Alessandro Atzei (ESA/ESTEC) Presentation Slides
This presentation will focus on the considerations that led to the GAIA design as well as the key lessons learned from the mission. The presentation will focus on the (system) engineering aspects.
Title: Flight Operations Experience on the GAIA mission
Speaker: David Milligan (ESA/ESOC) Presentation Slides
This presentation will focus on the mission operations experience gained in flying Gaia through the first years of the mission (covering the launch, LEOP, commissioning and Routine Ops phases).
September 5, 2017
Speaker: Eduardo Bendek (NASA/Ames)
Measuring masses of long-period planets around F, G, K or brighter stars is necessary to characterize exoplanets and assess their habitability. Imaging stellar astrometry offers a unique opportunity to measure exoplanet masses. However, its accuracy is limited by the non-systematic dynamic distortions that arise from perturbations in the optical train. We have tested a novel approach to measure and calibrate field distortion potentially enabling better than 1µas imaging astrometry accuracy. In this talk, we will review the architecture, milestones, and performance of the simultaneous astrometry and high-contrast imaging laboratory built at NASA Ames Research Center as part of a TDEM program. We will also discuss the impact and benefits of applying this technology to future flagship exoplanet missions, such as HABEX, STEP, and Theia.
Title: Detector Metrology for Ultra Precise Astrometry on LUVOIR
Speaker: Mike Shao (JPL) Presentation Slides
Astrometry at the sub-micro-arcsec level can detect and Earth mass planets in the habitable zone around a large number of nearby FGK stars. Reducing and/or calibrating instrumental systematic errors is the key to achieving very high astrometric accuracy. There are two major sources of systematic error for astrometry with a large focal plane detector, one optical distortion the optics and the second is imperfections in the focal plane. This talk discusses the imperfections in the focal plane, how they can be calibrated both on the ground and in orbit. The metrology system is part of the LUVOIR high definition imager instrument concept and we'll summarize what the capabilities of such an instrument would be for exo-Earth detection.
May 11, 2017
Title: MEMS Deformable Mirrors for Astronomical Adaptive Optics
Speaker: Paul Bierden, Boston Micromachines Corporation
As the astronomical community continues its excitement about the progress being made toward the building of the high contrast imaging telescopes, technical development is ongoing for the components needed for these instruments. This presentation will show the progress that has been made by Boston Micromachines on the design and fabrication of micro-electromechanical (MEMS) deformable mirrors that will be needed for future scientific progress. Large actuator count, high yield, and stable deformable mirrors are being made for on-sky planet finding instruments as well as test beds where the next generation instruments are being developed. The challenges addressed in this design and fabrication and the results achieved will be presented as well as how this will translate to meet future needs. Also, presented will be the results from current instruments and test beds. Finally, future plans for mirror development will be presented.
April 11, 2017
Title: Colloidal Micro-Newton Thrusters for Precision Attitude Control
Colloid micronewton thrusters offer a precise, low-mass, low-vibration (0.1 µN thrust precision with ≤0.1 µN/rtHz thrust noise) solution for fine pointing of space observatories. These electric thrusters can meet pointing requirements of <0.1 milliarcseconds for Hubble-class telescopes, exceeding the state-of-the art for reaction wheels while using less mass and similar power levels. Vibrations induced by the thrusters have been shown to produce less than 4nm displacements for a 500 kg spacecraft. This technology has been advanced to a high level of readiness (TRL 7) through the Space Technology 7 Disturbance Reduction System (ST7-DRS) technology demonstration payload, which was part of LISA Pathfinder's test of precision, drag-free control for the future LISA gravitational wave observatory. Continuing technology development now focuses on validating thruster lifetime and improving reliability for a flagship class science mission.
Speaker: John Ziemer (JPL)
January 23, 2017
Title: Edge Sensors for Segmented Mirrors
Future astronomical telescopes in space will have architectures that must meet complex and demanding requirements in order to meet science goals. The missions now under consideration by NASA for imaging exoplanets and characterizing their atmospheres have technical challenges that are near or beyond the state of the art of telescope stability. This colloquium describes segment edge sensing and control technologies developed for ground based telescopes, and shows how they might be used to stabilize space telescopes to picometer-class wavefront errors.
November 29, 2016
Title: Segmented Coronagraph Design and Analysis (SCDA) Study
Reaching high contrast ratios at close angular proximity to a star is an extremely challenging undertaking for a coronagraph with a filled-aperture telescope and is even more challenging with segmented, partially obscured apertures proposed for a large space-borne observatory. The primary goal of the ExEP-funded SCDA study is to identify coronagraph designs that maximize exo-Earth detectability with a variety of segmented apertures including hexagonal-segment and pie-wedge segment architectures. Both on-axis and off-axis designs are considered. The SCDA study is funding the design of pupil-plane, image-plane, and hybrid coronagraph designs. In this presentation, we discuss the progress in coronagraph designs and science yield performance since the study began in January 2016
The intention of these web seminars is to provide a forum for sharing key technology advances and results that enable or enhance the direct imaging and characterization of exoplanets. Topics may include recent coronagraph and starshade demonstration results, advances in detector technology, deformable mirrors, LOWFS/C, telescope stability, polarization, RV, starshade tutorials, etc. Our target audience is the engineers and scientists working on the WFIRST project and the HabEx, LUVOIR, and OST study concepts, but all are welcome to attend.
The series will be recorded and publically archived on this page so that they can be viewed at later dates.
To subscribe to the colloquium series, receive announcements, or suggest topics for future telecons, please contact Brendan Crill, Organizer