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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS2011

Grazing Incidence Wavefront Sensing and Verification of X-Ray Optics Performance

Evaluation of interferometrically measured mirror metrology data and characterization of a telescope wavefront can be powerful tools in understanding of image characteristics of an x-ray optical system. In the development of soft x-ray telescope for the International X-Ray Observatory (IXO), we have developed new approaches to support the telescope development process. Interferometrically measuring the optical components over all relevant spatial frequencies can be used to evaluate and predict the performance of an x-ray telescope. Typically, the mirrors are measured using a mount that minimizes the mount and gravity induced errors. In the assembly and mounting process the shape of the mirror segments can dramatically change. We have developed wavefront sensing techniques suitable for the x-ray optical components to aid us in the characterization and evaluation of these changes. Hartmann sensing of a telescope and its components is a simple method that can be used to evaluate low order mirror surface errors and alignment errors. Phase retrieval techniques can also be used to assess and estimate the low order axial errors of the primary and secondary mirror segments. In this paper we describe the mathematical foundation of our Hartmann and phase retrieval sensing techniques. We show how these techniques can be used in the evaluation and performance prediction process of x-ray telescopes.

Saha, Timo T.↗
NASA NTRS2021

LUVOIR-ECLIPS Closed-Loop Adaptive Optics Performance and Contrast Predictions

One of the primary science goals of the Large UV/Optical/Infrared Surveyor (LUVOIR) mission concept is to detect and characterize Earth-like exoplanets orbiting nearby stars with direct imaging. The success of its coronagraph instrument ECLIPS (Extreme Coronagraph for Living Planetary Systems) depends on the ability to stabilize the wavefront from a large segmented mirror such that optical path differences are limited to tens of picometers RMS during an exposure time of a few hours. In order to relax the constraints on the mechanical stability, ECLIPS will be equipped with a wavefront sensing and control (WS\&C) architecture to correct wavefront errors up to temporal frequencies $\gtrsim$1 Hz. These errors may be dominated by spacecraft structural dynamics exciting vibrations at the segmented primary mirror. In this work, we present detailed simulations of the WS\&C system within the ECLIPS instrument and the resulting contrast performance. This study assumes wavefront aberrations based on a finite element model of a simulated telescope with spacecraft structural dynamics. Wavefront residuals are then computed according to a model of the adaptive optics system that includes numerical propagation to simulate a realistic wavefront sensor and an analytical model of the temporal performance. An end-to-end numerical propagation model of ECLIPS is then used to estimate the residual starlight intensity distribution at the science detector. We show that the contrast performance depends strongly on the target star magnitude and the spatio-temporal distribution of wavefront errors from the telescope. In cases with significant vibration, we advocate for the use of laser metrology to mitigate high temporal frequency wavefront errors and increase the mission yield.

Sirbu, Dan↗
NASA NTRS2018

LUVOIR Primary Mirror Segment Alignment Control With Joint Laser Metrology and Segment Edge Sensing

An approach is developed for the alignment and stability maintenance of the LUVOIR segmented primary mirror using a segment state estimation and wavefront control method based on a hybrid segment motion sensing architecture of laser truss metrology and segment edge sensors. Our current computer model was generated for LUVOIR Architecture Option A with a 15-meter aperture, 120segment primary mirror. The methodology and simulation results will be presented and analyzed. JPL has a long history of technology development in laser metrology and edge sensors, including work in SIM [7], Keck and TMT [8], CCAT [3] and LUVOIR [1]. We will discuss our current efforts of LUVOIR laser metrology and edge-sensor models development, showing sensitivities of sensor measurements to various mirror eigenmodes, removing global modes and strengthening weak modes by performing joint (hybrid) laser-metrology and edge sensing. We will define and derive an important performance metric called wavefront error multiplier (WEM), and show that WEM provides a simple link between sensor errors and the closed-loop (controlled) system wavefront error. We will show WEM values for several hybrid sensor configuration options studied. We will discuss an algorithm for mirror shape control and maintenance through segment state and wavefront estimations using joint edge-metrology sensing. We will compare simulated performance of mirror state estimation, wavefront estimation and wavefront control based on joint edge-metrology sensing among several sensor configurations, and show the impact of sensor error distributions on the segmented mirror alignment performance. Mirror shape control performance will be also be evaluated in terms of imaging contrast between inner working angles (IWA) and outer working angles (OWA) of a LUVOIR coronagraph. The research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. LUVOIR is a mission concept under study for the next astronomy Decadal Survey—the information presented in this paper is pre-decisional and is provided for planning and discussion purposes only.

Shelton, Chris↗
NASA NTRS2022

Modeling and Performance Analysis of the LUVOIR Coronagraph Instrument

Future space missions such as the Large UV/Optical/Infrared Surveyor (LUVOIR) and the Habitable Exoplanet Observatory, when equipped with coronagraphs with active wavefront control to suppress starlight, will allow the discovery and characterization of habitable exoplanets. The Extreme Coronagraph for Living Planetary Systems (ECLIPS) is the coronagraph instrument on the LUVOIR Surveyor mission concept, an 8- to 15-m segmented telescope. ECLIPS is split into three channels, namely, UV (200 to 400 nm), optical (400 to 850 nm), and near IR (850 nm to 2 μm), with each channel equipped with two deformable mirrors for wavefront control, a suite of coronagraph masks, a low-order/out-of-band wavefront sensor, and separate science imagers and spectrographs. The apodized pupil Lyot coronagraph and the vector vortex coronagraph are the baselined mask technologies for ECLIPS to enable the required 10−10 contrast for observations in the habitable zones of nearby stars for LUVOIR-A (15-m telescope) and LUVOIR-B (8-m telescope), respectively. Their performance depends on active wavefront sensing and control, as well as metrology subsystems to compensate for aberrations induced by segment errors (e.g., piston and tip/tilt), secondary mirror misalignment, and global low-order wavefront errors. Here, we present the latest results of the simulation of these effects for the LUVOIR coronagraph instrument and discuss the achieved contrast for exoplanet detection and characterization after closed-loop wavefront estimation and control algorithms have been applied. Finally, we show simulated observations using high-fidelity spatial and spectral input models of complete planetary systems generated with the Haystacks code framework.

Roser Juanola-Parramon↗
NASA NTRS2019

The LUVOIR Extreme Coronagraph for Living Planetary Systems (ECLIPS) II. Performance Evaluation, Aberration Sensitivity Analysis and Exoplanet Detection Simulations

Future space missions such as the Large UV-Optical-Infrared Surveyor (LUVOIR) and the Habitable Exoplanet Observatory (HabEx) require coronagraphs with active wavefront control to suppress starlight to discover and characterize habitable exoplanets. The Extreme Coronagraph for Living Planetary Systems (ECLIPS) is the coronagraph instrument on the LUVOIR Surveyor mission concept, an 8–15m segmented telescope. ECLIPS is split into three channels: UV (200 to 400 nm), optical (400 nm to 850 nm), and NIR (850 nm to 2.0 microns), with each channel equipped with two deformable mirrors for wavefront control, a suite of coronagraph masks, a low-order/out-of-band wavefront sensor, and separate science imagers and spectrographs. The Apodized Pupil Lyot Coronagraph (APLC) and the Vector Vortex Coronagraph (VVC) are the baselined mask technologies for ECLIPS to enable the required 10 -10 contrast for 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 aberrations induced by segment errors (piston and tip/tilt, among others), secondary mirror misalignment, and global low-order wavefront errors. Here we present the latest results of the simulation of these effects for the two technologies and discuss the achieved contrast for exoplanet detection and characterization after closed-loop wavefront estimation and control algorithms have been applied. Finally, we show simulated observations using high-fidelity spatial and spectral input models of complete planetary systems generated with the Haystacks code framework.

Roser Juanola-Parramon↗
NASA NTRS2018

Laser Metrology for Ultra-Stable Space-Based Coronographs

Sensing starlight rejected from a coronagraph is essential in stabilizing the telescope pointing and wavefront drift, but performance is degraded for dim stars. Laser Metrology (MET) provides a different, complementary sensing method, one that can be used to measure changes in the alignment of the optics at high bandwidth, independent of the magnitude of the host star. Laser metrology measures changes in the separation of optical fiducial pairs, which can be separated by many meters. The principle of operations is similar to the laser metrology system used in LISA-Pathfinder to measure the in-orbit displacement between two test masses to a precision of ~10 picometers. In closed loop with actuators, MET actively maintains rigid body alignment of the front-end optics, thereby eliminating the dominant source of wavefront drift. In the case of a segmented, active primary mirror, MET provides six degrees of freedom sensing, replacing edge sensors. MET maintains wavefront control even during attitude maneuvers, such as slews between target stars, thereby avoiding the need to repeat time-consuming speckle suppression. These features can significantly improve the performance and observational efficiency of future large-aperture space telescopes equipped with internal coronagraphs. We evaluate MET trusses for various proposed monolithic and segmented space-based coronagraphs and present the performance requirements necessary to maintain contrast drift below 10^-11.

Moore, Dustin↗
NASA NTRS1993

Advanced technology development multi-color holography

This is the final report of the Multi-color Holography project. The comprehensive study considers some strategic aspects of multi-color holography. First, various methods of available techniques for accurate fringe counting are reviewed. These are heterodyne interferometry, quasi-heterodyne interferometry, and phase-shifting interferometry. Phase-shifting interferometry was found to be the most suitable for multi-color holography. Details of experimentation with a sugar solution are also reported where better than 1/200 of a fringe order measurement capability was established. Rotating plate glass phase shifter was used for the experimentation. The report then describes the possible role of using more than two wavelengths with special reference-to-object beam intensity ratio needs in multicolor holography. Some specific two- and three-color cases are also described in detail. Then some new analysis methods of the reconstructed wavefront are considered. These are deflectometry, speckle metrology, confocal optical signal processing, and phase shifting technique related applications. Finally, design aspects of an experimental breadboard are presented.

Vikram, Chandra S.↗
NASA NTRSDate not supplied

End-to-end Modeling of Lyot Coronagraph for LUVOIR: Sensitivity to Segment-Level Aberrations

Direct imaging and spectroscopic characterization of atmospheres of Earth-like exoplanets require starlight suppression to detect a faint planetary signal at small angular separations. Future space telescopes will require segmentation to survey a statistically significant population of nearby stars systems by increasing aperture size beyond the limits set by traditional monolithic apertures; however, segmentation also represents an additional challenge due to the introduction of temporal pupil discontinuities in terms of both phase and amplitude. For this study, a baseline Lyot coronagraph is used with the Large UV / Optical /Infrared (LUVOIR) mission’s 15-m on-axis, segmented optical telescope assembly (OTA). We present a high-fidelity, end-to-end modeling approach developed as part of the Segmented Coronagraph Design and Analysis (SCDA) group that includes diffractive optical propagations at the 1e-10 contrast level across the entire optical train including the OTA and intermediate re-imaging optics inside the coronagraph instrument. We perform a tolerancing analysis to assess the contrast sensitivity to wavefront perturbations for a set of key telescope terms including segment-level low-order and mid-spatial frequency aberrations. As an input to the end-to-end telescope model, we use two industry-provided segment-level wavefront aberration datasets pertaining: (1) thermal gradients and accelerations (courtesy of Ball-Aerospace and L3-Harris), and (2) telescope dynamics including line-of-sight and segment jitter (courtesy of Lockheed-Martin). Contrast performance outputs of the coronagraph are fed into a mission design reference simulator to assess the scientific yield sensitivity. End-to-end modeling will incorporate performance improvements due to active wavefront sensing and control and/or segment-level metrology to improve system performance.

Optics↗
NASA NTRS2022

Defining Pupil Knowledge Requirements for Roman Space Telescope Integrated Payload Assembly Testing

This thesis examines the use of phase retrieval to characterize an optical system under testing conditions with pupil knowledge error. The purpose of this research is to define pupil knowledge requirements for the integrated payload testing of the Roman Space Telescope (RST). I have conducted a Monte Carlo study to determine how uncertainty in the location of the ground support equipment relative to the payload will affect the ability to use image-based wavefront sensing during the test to characterize system alignment. This test will be conducted in the Space Environment Simulator (SES) with the presence of Wavefront Error (WFE) due to gravity sag on the primary mirror. In this study, I incrementally decentered a piece of ground support equipment, the SubAperture Metrology System (SAMS), and evaluated how the phase retrieval algorithm attempted to fit the wavefront with the pupil mismatch. The results of this study are a factor in the overall Integrated Payload Assembly (IPA) testing WFE budget.

Roman Space Telescope↗
NASA NTRS2001

Adjustable Focus Optical Correction Lens (AFOCL)

This report describes a metrology plan that was developed for the characterization of PLZT-based devices, such as the Adjustable Focus Optical Correction Lens (AFOCL) in support of and as part of the deliverables for NASA contract NAS8-00118. The areas to be investigated include intensiometric effects (those that limit or alter the intensity of the light transmitted through the optic); interferometric effects (the phase change induced through the optic); and polarimetric effects (evaluating the differential lag between two polarization states propagating through the optic). These distinct phenomena are often coupled together in real applications consequently, there is a need to develop different standardized testing apparatus to: (1) isolate one effect from another; (2) gather information for understanding the physical effects; (3) anchor wavefront corrector modeling efforts; (4) develop the ability to decouple different effects; (5) demonstrate the suitability of PLZT technology to perform wavefront correction. The Center for Applied Optics (CAO) at the University of Alabama in Huntsville (UAH) is skilled in the characterization of transmission wavefront shaping devices using traditional interferometers available within the CAO Optical Metrology Laboratory and their Advanced Polarization Test Facility. Besides the imaging and interferometers available, the polarimetry facility has at its disposal, a Mueller Matrix Imaging Polarimeter (MMIP) which is well suited to the characterization of SLMs, polarizers, and thin film coatings within the visible and near-IR spectrums. In addition, the phase-shifting interferometry facilities at NASA-MSFC and the unique interferometers they processes are some of the most advanced available and may be of value especially for performing real-time optical performance evaluation of AFOCL test components.

Peters, Bruce R.↗
NASA NTRS2017

Wavefront sensing for a future HabEx space telescope.

HabEx is a concept study for a next generation space telescope having a 4 to 6.5 m primary mirror diameter. Primarily designed for exoplanet science, but also carrying general astrophysics instruments, it will have stability requirements orders of magnitude more stringent than any previously flown space-based observatory. Wavefront control, including active sensing/control of wavefront jitter and drift, will be essential to achieving and maintaining coronagraph performance. There are currently two complementary techniques that can be used to sense the wavefront drift. An attractive method is to use starlight rejected from the coronagraph to sense changes in the wavefront incident on the coronagraph mask. This method suffers from photon noise especially when imaging dim stars. It is also unavailable during slews between target stars. Laser metrology is a complementary system in which a laser “truss” enables rigid body displacements of the optics to be measured from changes in the separation of pairs of optical fiducials which can be separated by many meters. In closed loop with actuated optics, laser metrology actively maintains rigid body alignment of the front-end optics, thereby eliminating the dominant source of wavefront drift. This method can maintain rigid body stability of the telescope optics and thereby wavefront control, even during slews between targets.

Martin, Stefan↗
NASA NTRS2012

Stitching of near-nulled subaperture measurements

A metrology system for measuring aspheric test objects by subaperture stitching. A wavefront-measuring gauge having a limited capture range of wavefront shapes collects partially overlapping subaperture measurements over the test object. A variable optical aberrator reshapes the measurement wavefront with between a limited number of the measurements to maintain the measurement wavefront within the capture range of the wavefront-measuring gauge. Various error compensators are incorporated into a stitching operation to manage residual errors associated with the use of the variable optical aberrator.

Murphy, Paul↗
NASA NTRSDate not supplied

Picometer-Level Metrology on the Road to Habitable Worlds Observatory

The Habitable Worlds Observatory will revolutionize our understanding of the universe by directly detecting biosignatures on extrasolar planets and allow us to answer the question if we are alone in the universe. To accomplish the tight science goals associated with this mission, the development of an ultrastable observatory with a coronagraphic instrument is necessary. The observatory itself may need to stay stable on the order of 10 picometers over a wavefront control cycle, orders of magnitude more stable than what is required on current space missions. The metrology to verify stability requirements must be roughly a factor of ten more stable. The ultrastable laboratory at NASA’s Goddard Space Flight Center has further stabilized its testbed to allow for dynamic measurements on diffuse and specular objects on the order of single picometers, and we are currently measuring drifts on the orders of tens of picometers over different temporal bands. This paper will discuss the mechanical updates to the testbed setup, the analysis performed on several test articles, and the path forward on the road to measuring achieving the required stability for Habitable Worlds Observatory.

Inteferometry↗
DOE OSTI2023

At-wavelength characterization of X-ray wavefronts in Bragg diffraction from crystals

The advent of next-generation synchrotron radiation sources and X-ray free-electron lasers calls for high-quality Bragg-diffraction crystal optics to preserve the X-ray beam coherence and wavefront. This requirement brings new challenges in characterizing crystals in Bragg diffraction in terms of Bragg-plane height errors and wavefront phase distortions. Here, a quantitative methodology to characterize crystal optics using a state-of-the-art at-wavelength wavefront sensing technique and statistical analysis is proposed. The method was tested at the 1-BM-B optics testing beamline at the Advanced Photon Source for measuring silicon and diamond crystals in a self-referencing single-crystal mode and an absolute double-crystal mode. The phase error sensitivity of the technique is demonstrated to be at the λ/100 level required by most applications, such as the characterization of diamond crystals for cavity-based X-ray free-electron lasers.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRSDate not supplied

Picometer-level metrology of test articles on the road to Habitable Worlds Observatory

The Habitable Worlds Observatory will revolutionize our understanding of the universe by directly detecting biosignatures on extrasolar planets and allow us to answer the question if we are alone in the universe. To accomplish the tight science goals associated with this mission, the development of an ultrastable observatory with a coronagraphic instrument is necessary. The observatory itself may need to stay stable on the order of 10 picometers over a wavefront control cycle, orders of magnitude more stable than what is required on current space missions. The metrology to verify stability requirements must be roughly a factor of ten more stable. The ultrastable laboratory at NASA’s Goddard Space Flight Center has further stabilized its testbed to allow for dynamic measurements on diffuse and specular objects on the order of single picometers, and we are currently measuring drifts on the orders of tens of picometers over different temporal bands. This paper will discuss the mechanical updates to the testbed setup, the analysis performed on several test articles, and the path forward on the road to measuring achieving the required stability for Habitable Worlds Observatory.

Inteferometry↗
NASA NTRSDate not supplied

Picometer-Level Metrology of Test Articles on the Road to Habitable Worlds Observatory

The Habitable Worlds Observatory will revolutionize our understanding of the universe by directly detecting biosignatures on extrasolar planets and allow us to answer the question if we are alone in the universe. To accomplish the tight science goals associated with this mission, the development of an ultrastable observatory with a coronagraphic instrument is necessary. The observatory itself may need to stay stable on the order of 10 picometers over a wavefront control cycle, orders of magnitude more stable than what is required on current space missions. The metrology to verify stability requirements must be roughly a factor of ten more stable. The ultrastable laboratory at NASA’s Goddard Space Flight Center has further stabilized its testbed to allow for dynamic measurements on diffuse and specular objects on the order of single picometers, and we are currently measuring drifts on the orders of tens of picometers over different temporal bands. This paper will discuss the mechanical updates to the testbed setup, the analysis performed on several test articles, and the path forward on the road to measuring achieving the required stability for Habitable Worlds Observatory.

Inteferometry↗
NASA NTRS2002

Wavefront tilt feedforward for the formation interferometer testbad (FIT)

Separated spacecraft interferometry is a candidate architecture for several future NASA missions. The Formation Interferometer Testbed (FIT) is a ground based testbed dedicated to the validation of this key technology for a formation of two spacecraft. In separated spacecraft interferometry, the residual relative motion of the component spacecraft must be compensated for by articulation of the optical components. In this paper, the design of the FIT interferometer pointing control system is described. This control system is composed of a metrology pointing loop that maintains an optical link between the two spacecraft and two stellar pointing loops for stabilizing the stellar wavefront at both the right and left apertures of the instrument. A novel feedforward algorithm is used to decouple the metrology loop from the left side stellar loop. Experimental results from the testbed are presented that verify this approach and that fully demonstrate the performance of the algorithm.

formation flying↗
NASA NTRS2006

Results from SIM's Thermo-Opto-Mechanical (TOM3) Testbed

Future space-based optical interferometers, such as the Space Interferometer Mission Planet Quest (SIM), require thermal stability of the optical wavefront to the level of picometers in order to produce astrometric data at the micro-arc-second level. In SIM, the internal path of the interferometer will be measured with a small metrology beam whereas the starlight fringe position is estimated from a large concentric annular beam. To achieve the micro-arc-second observation goal for SIM, it is necessary to maintain the optical path difference between the central and the outer annulus portions of the wavefront of the front-end telescope optics to a few tens of picometers. The Thermo-Opto-Mecha nical testbed (TOM3) was developed at the Jet Propulsion Laboratory to measure thermally induced optical deformations of a full-size flight-like beam compressor and siderostat, the two largest optics on SIM, in flight-like thermal environments. A Common Path Heterodyne Interferometer (COPHI) developed at JPL was used for the fine optical path difference measurement as the metrology sensor. The system was integrated inside a large vacuum chamber in order to mitigate the atmospheric and thermal disturbances. The siderostat was installed in a temperature-controlled thermal shroud inside the vacuum chamber, creating a flight-like thermal environment. Detailed thermal and structural models of the test articles (siderostat and compressor) were also developed for model prediction and correlation of the thermal deformations. Experimental data shows SIM required thermal stability of the test articles and good agreement with the model predictions.

interferometry↗