The GOES-R series is the latest in a long line of American geostationary weather satellites operated by NOAA (National Oceanic and Atmospheric Administration). The Solar Ultraviolet Imager (SUVI) is an instrument onboard Geostationary Operational Environmental Satellites, GOES-R series, part of NOAA's (National Oceanic and Atmospheric Administration) space weather monitoring fleet. GOES-16 SUVI is in operation and the GOES-17 SUVI has completed initial calibrations.
SUVI is a generalized Cassegrain telescope with a large field of view that employs multilayer coatings optimized to operate in six extreme ultraviolet (EUV) narrow bandpasses centered at 9.4, 13.1, 17.1, 19.5, 28.4 and 30.4 nm. The SUVI EUV line set provides the best comprehensive feature and dynamics information for revealing and correlating both the low coronal signatures of coronal mass ejections (CME) triggers (for example, flares) and the high coronal signatures of the actual CME. SUVI acquires full disk images in EUV band pass every few minutes and telemeters the data to the ground for digital processing. These data will enable NOAA to monitor solar activity and to issue accurate near real-time alerts when space weather may possibly affect the performance and reliability of space-borne and ground-based technological systems and human endeavors.
This paper describes key design drivers in the development of SUVI, methods used in the autonomous on-orbit calibration of the instrument, and the automated monitoring of the health and safety of the instrument during operations.
The NIRCam instrument on the James Webb Space Telescope (JWST) will provide a coronagraphic
imaging capability to search for extrasolar planets in the 2 - 5 microns wavelength range. This capability is
realized by a set of Lyot pupil stops with patterns matching the occulting mask located in the JWST
intermediate focal plane in the NIRCam optical system. The complex patterns with transparent apertures
are made by photolithographic process using a metal coating in the opaque region. The optical density
needs to be high for the opaque region, and transmission needs to be high at the aperture. In addition, the
Lyot stop needs to operate under cryogenic conditions. We will report on the Lyot stop design, fabrication
and testing in this paper.
This paper presents the optical design of the Dilute Aperture Visible Nulling Coronagraph Imaging (DAViNCI).
DAViNCI's dilute aperture approach to the TPF-C extra-solar earth-like detection mission reduces cost and technical
risk compared to other filled aperture approaches. DAViNCI has been studied in an ASMCS (Astrophysics Strategic
Mission Concept Study) and is included within the ASTRO2010 Decadal review . The DAViNCI team is led by
Michael Shao (PI) of JPL.
Three of the recently completed NASA Astrophysics Strategic Mission Concept (ASMC) studies addressed the
feasibility of using a Visible Nulling Coronagraph (VNC) as the prime instrument for exoplanet science. The VNC
approach is one of the few approaches that works with filled, segmented and sparse or diluted aperture telescope systems
and thus spans the space of potential ASMC exoplanet missions. NASA/Goddard Space Flight Center (GSFC) has a
well-established effort to develop VNC technologies and has developed an incremental sequence of VNC testbeds to
advance the this approach and the technologies associated with it. Herein we report on the continued development of the
vacuum Visible Nulling Coronagraph testbed (VNT). The VNT is an ultra-stable vibration isolated testbed that operates
under high bandwidth closed-loop control within a vacuum chamber. It will be used to achieve an incremental sequence
of three visible light nulling milestones of sequentially higher contrasts of 108, 109 and 1010 at an inner working angle of
2*λ/D and ultimately culminate in spectrally broadband (>20%) high contrast imaging. Each of the milestones, one per
year, is traceable to one or more of the ASMC studies. The VNT uses a modified Mach-Zehnder nulling interferometer,
modified with a modified "W" configuration to accommodate a hex-packed MEMS based deformable mirror, a coherent
fiber bundle and achromatic phase shifters. Discussed will be the optical configuration laboratory results, critical
technologies and the null sensing and control approach.
Embedding solid-state ceramic actuators in a bending style deformable mirror presents unique athermalization
challenges when operated at cryogenic temperatures. Approaches to athermally embed actuators in a substrate are
presented in this study. Each approach is rated according to established design criteria: unmatched displacement, range,
compliance ratio, bondline stress, design, and manufacturability. We show the results of our design that allows a large
thermal range of operation for the actuators.
We report on our recent laboratory results with the NASA/Goddard Space Flight Center (GSFC) Visible Nulling
Coronagraph (VNC) testbed. We have experimentally achieved focal plane contrasts of 1 x 108 and approaching 109 at
inner working angles of 2 * wavelength/D and 4 * wavelength/D respectively where D is the aperture diameter. The
result was obtained using a broadband source with a narrowband spectral filter of width 10 nm centered on 630 nm. To
date this is the deepest nulling result with a visible nulling coronagraph yet obtained. Developed also is a Null Control
Breadboard (NCB) to assess and quantify MEMS based segmented deformable mirror technology and develop and
assess closed-loop null sensing and control algorithm performance from both the pupil and focal planes. We have
demonstrated closed-loop control at 27 Hz in the laboratory environment. Efforts are underway to first bring the contrast
to > 109 necessary for the direct detection and characterization of jovian (Jupiter-like) and then to > 1010 necessary for
terrestrial (Earth-like) exosolar planets. Short term advancements are expected to both broaden the spectral passband
from 10 nm to 100 nm and to increase both the long-term stability to > 2 hours and the extent of the null out to a ~ 10 *
wavelength / D via the use of MEMS based segmented deformable mirror technology, a coherent fiber bundle,
achromatic phase shifters, all in a vacuum chamber at the GSFC VNC facility. Additionally an extreme stability
textbook sized compact VNC is under development.
We evaluate the feasibility of a balloon-borne nulling interferometer to detect and characterize an exosolar planet and the
surrounding debris disk. The existing instrument consists of a three-telescope Fizeau imaging interferometer with thre
fast steering mirrors and three delay lines operating at 800 Hz for closed-loop control of wavefront errors and fine
pointing. A compact visible nulling interferometer would be coupled to the imaging interferometer and in principle,
allows deep starlight suppression. Atmospheric simulations of the environment above 100,000 feet show that balloonborne
payloads are a possible path towards the direct detection and characterization of a limited set of exoplanets and
debris disks. Furthermore, rapid development of lower cost balloon payloads provide a path towards advancement of
NASA technology readiness levels for future space-based exoplanet missions. Discussed are the BENI mission and
instrument, the balloon environment and the feasibility of such a balloon-borne mission.
The NIRCam instrument on the James Webb Space Telescope will provide coronagraphic imaging from λ =1-5 μm of
high contrast sources such as extrasolar planets and circumstellar disks. A Lyot coronagraph with a variety of circular
and wedge-shaped occulting masks and matching Lyot pupil stops will be implemented. The occulters approximate
grayscale transmission profiles using halftone binary patterns comprising wavelength-sized metal dots on anti-reflection
coated sapphire substrates. The mask patterns are being created in the Micro Devices Laboratory at the Jet Propulsion
Laboratory using electron beam lithography. Samples of these occulters have been successfully evaluated in a
coronagraphic testbed. In a separate process, the complex apertures that form the Lyot stops will be deposited onto
optical wedges. The NIRCam coronagraph flight components are expected to be completed this year.
DAVINCI is a dilute aperture nulling coronagraph that has the potential of directly detecting an Earth in the habitable zone around ~100 nearby stars. The novel feature of this mission concept is to replace a filled aperture 5-6 meter telescope with 4 by 1.1 meter
telescopes in a phased array, dramatically reducing the cost by
potentially by a factor of 5-10.
This work presents a novel approach of modeling hysteresis using the Preisach model. Instead of relying entirely on the
Presisach model, the hysteretic behavior is separated into a non-linear least squares fit function and a Preisach model.
This separation allows for the independent analysis of the non-linear portion and hysterestic behavior of actuators. In
particular, the paper addresses the response modeling of deformable mirrors (DM) piezoceramic actuators for use in
adaptive optics. Several inversion algorithms have also been developed and presented here. These algorithms are used
in a feed-forward loop as part of the DM control algorithms.
We have developed performance simulations for a precision attitude determination system using a focal plane star
tracker on an infrared space telescope. The telescope is being designed for the Destiny mission to measure
cosmologically distant supernovae as one of the candidate implementations for the Joint Dark Energy Mission. Repeat
observations of the supernovae require attitude control at the level of 0.010 arcseconds (0.05 microradians) during
integrations and at repeat intervals up to and over a year. While absolute accuracy is not required, the repoint precision is
challenging. We have simulated the performance of a focal plane star tracker in a multidimensional parameter space,
including pixel size, read noise, and readout rate. Systematic errors such as proper motion, velocity aberration, and
parallax can be measured and compensated out. Our prediction is that a relative attitude determination accuracy of 0.001
to 0.002 arcseconds (0.005 to 0.010 microradians) will be achievable. Attitude control will have a jitter of around 0.003
arcseconds and stability/repeatability to around 0.002 arcseconds.
The Extrasolar Planetary Imaging Coronagraph (EPIC) is a NASA Astrophysics Strategic Mission Concept
under study for the upcoming Exoplanet Probe. EPIC's mission would be to image and characterize
extrasolar giant planets, and potential super-Earths, in orbits with semi-major axes between 2 and 10 AU.
EPIC will provide insights into the physical nature of a variety of planets in other solar systems
complimenting radial velocity (RV) and astrometric planet searches. It will detect and characterize the
atmospheres of planets identified by radial velocity surveys and potentially some transits, determine orbital
inclinations and masses, characterize the atmospheres of gas giants around A and F stars, observed the
inner spatial structure and colors of inner Spitzer selected debris disks. EPIC would be launched into a
heliocentric Earth trailing drift-away orbit, with a 3-year mission lifetime (5 year goal) and will revisit
planets at least three times.
The starlight suppression approach consists of a visible nulling coronagraph (VNC) that enables high order
starlight suppression in broadband light. To demonstrate the VNC approach and advance it's technology
readiness the NASA/Goddard Space Flight Center and Lockheed-Martin have developed a laboratory VNC
and have demonstrated white light nulling. We will discuss our ongoing VNC work and show the latest
results from the VNC testbed.
Smithsonian Astrophysical Observatory (SAO) has set up a program to study coronagraphic techniques. The program consists of the development of new fabrication methods of occulter masks, characterization of the manufactured masks, and application of the masks to study speckle reduction technique. Our occulter mask fabrication development utilizes a focused ion beam system to directly shape mask profiles from absorber material. Initial milling trials show that we can shape nearly Gaussian-shaped mask profiles. Part of this development is the characterization of absorber materials, poly(methyl methacrylate) doped with light-stable chromophores. For the characterization of the masks we have built a mask scanner enabling us to scan the transmission function of occulter masks. The real mask transmission profile is retrieved applying the maximum entropy method to deconvolve the mask transmission function from the beam profile of the test laser. Finally, our test bed for studying coronagraphic techniques is nearing completion. The optical setup is currently configured as a classical coronagraph and can easily be re-configured for studying speckle reduction techniques. The development of the test bed control software is under way. This paper we will give an update of the status of the individual program elements.
SAO has set up a testbed to study coronagraphic techniques, starting with Labeyrie's multi-step speckle reduction technique. This technique expands the general concept of a coronagraph by incorporating a speckle corrector (phase and/or amplitude) in combination with a second occulter for speckle light suppression. Here we are describing the initial testbed configuration. In addition, the testbed will be used to test a new approach of the phase diversity method to retrieve the speckle phase and amplitude. This method requires measurements of the speckle pattern in the focal plane and slightly out-of-focus. Then we will calculate a phase of the wave from which we can derive a correction function for the speckle corrector. Furthermore we report results from a parallel program which studies new manufacturing methods of soft-edge occulter masks. Masks were manufactured using the spherical caps method. Since the results were not satisfying we also investigated the method of ion beam milling of masks. Here we will present the outline of this method. Masks manufactured with both methods will be fully characterized in our mask tester before their use in the testbed.
The Near Infrared Camera (NIRCam) instrument for NASA's James Webb Space Telescope (JWST) is one of the four science instruments installed into the Integrated Science Instrument Module (ISIM) on JWST intended to conduct scientific observations over a five year mission lifetime. NIRCam's requirements include operation at 37 kelvins (K) to produce high resolution images in two wave bands encompassing the range from 0.6 microns to 5 microns. In addition NIRCam is used as a metrology instrument during the JWST observatory commissioning on orbit, during the initial and subsequent precision alignments of the observatory's multiple-segment 6.3 meter primary mirror. This paper describes some preliminary performance results of prototype coronagraph masks.
The Near Infrared Camera (NIRCam) instrument for NASA's James Webb Space Telescope (JWST) is one of the four science instruments installed into the Integrated Science Instrument Module (ISIM) on JWST intended to conduct scientific observations over a five year mission lifetime. NIRCam's requirements include operation at 37 kelvins (K) to produce high resolution images in two wave bands encompassing the range from 0.6 microns to 5 microns. In addition NIRCam is used as a metrology instrument during the JWST observatory commissioning on orbit, during the initial and subsequent precision alignments of the observatory's multiple-segment 6.3 meter primary mirror. This paper describes the integration and test (I&T) processes used to verify the Imaging Optical Assembly (IOA) to the defined requirements.
Large deployable space telescopes like the James Webb Space Telescope (JWST) may have large errors after deployment that must be corrected in situ. One approach is to correct the errors successively. In this paper, we present a new approach to correct large phase aberrations during the coarse figuring stage of the initial alignment. Intensity data is obtained from multiple planes: pupil plane and additional planes in the nearfield of the pupil plane. The irradiance transport equation is used in a new manner used to estimate the phase aberrations at the pupil. The technique was demonstrated in the lab to estimate phase aberrations approaching 20 waves.
Much recent attention has been paid to wavefront sensing by phase-diverse phase retrieval (PDPR): estimating the wavefront in an exit pupil based on point-spread function measurements that incorporate known additional aberrations. The Next-Generation Space Telescope (NGST), for example, is expected to rely on this technology. This paper studies narrowband PDPR via "point-by-point" reconstruction, which estimates the phase at each sampled point in the pupil plane without using basis functions. The performance of an iterative, point-by-point phase diversity (PD) algorithm is demonstrated on data from an NGST-oriented wavefront sensing and control testbed as well as simulated data. Encouraging performance is exhibited in simulation and on experimental images in the presence of mild, continuous aberrations; however, in the presence of larger, discontinuous aberrations the experimental performance is poorer. The estimation algorithm is also used to compute Cramer-Rao bounds (CRBs) for a simulated PDPR problem and to analyze their sensitivity to system parameters such as field-of-view, wavelength, and the amount of focus diversity.
Large segmented and distributed aperture telescopes increasingly rely on innovative imaging techniques such as phase diversity and phase retrieval. These algorithms obtain the phase aberration in a dynamic system by different estimation techniques using the information from in-focus and out-of-focus images of extended objects and point objects, respectively. These estimation techniques are generally iterative and suffer from the usual pitfalls of CPU demands and failure modes.
An alternative method would be to obtain an expression for the wavefront directly from the phase diversity measurements. The optimal wavefront expression would be expressed as a polynomial times the unaberrated OTF derived from the aberrated PSF. In this paper, we first obtain the expansion of the aberrated PSF with an explicit dependence on the amount of diversity and explore the implications of varying amounts of diversity as well as different numbers of diversity planes. Finally, we discuss solutions for the wavefront expression.
Dispersed fringe sensor (DFS) using broadband point source can unambiguously estimate piston to several hundred microns. We demonstrate a rapid technique to analyze the data from a DFS. The technique is less susceptible to higher order aberrations and returns the average phase difference between two aperture elements.