The Membrane Optical Imager (for) Real-time Exploitation (MOIRE) programs’ primary optics are constructed using a membrane material. Using a membrane enables the goal of the MOIRE program to launch large, greater than 10m aperture, optics while simultaneously reducing the weight of the optic. Achieving the desired performance of the membrane as an optical material is highly dependent upon the ability to control that membrane through the design and fabrication process via an understanding of the material properties of the membrane. This paper will cover the material property characterization, testing performed and lessons learned about the unique attributes of membranes, both as a material and as an optic.

The desire to field space-based telescopes with apertures in excess of 10 meter diameter is forcing the development of extreme lightweighted large optomechanical structures. Sparse apertures, shell optics, and membrane optics are a few of the approaches that have been investigated and demonstrated. Membrane optics in particular have been investigated for many years. The MOIRE approach in which the membrane is used as a transmissive diffractive optical element (DOE) offers a significant relaxation in the control requirements on the membrane surface figure, supports extreme lightweighting of the primary collecting optic, and provides a path for rapid low cost production of the primary optical elements. Successful development of a powered meter-scale transmissive membrane DOE was reported in 2012. This paper presents initial imaging results from integrating meter-scale transmissive DOEs into the primary element of a 5-meter diameter telescope architecture. The brassboard telescope successfully demonstrates the ability to collect polychromatic high resolution imagery over a representative object using the transmissive DOE technology. The telescope includes multiple segments of a 5-meter diameter telescope primary with an overall length of 27 meters. The object scene used for the demonstration represents a 1.5 km square complex ground scene. Imaging is accomplished in a standard laboratory environment using a 40 nm spectral bandwidth centered on 650 nm. Theoretical imaging quality for the tested configuration is NIIRS 2.8, with the demonstration achieving NIIRS 2.3 under laboratory seeing conditions. Design characteristics, hardware implementation, laboratory environmental impacts on imagery, image quality metrics, and ongoing developments will be presented.

The ability to fabricate 4-level diffractive structures with 1 µm critical dimensions has been demonstrated for the creation of fast (∼f/3.1 at 633 nm) Fresnel zone lenses (FZLs) with >60% diffraction efficiency into the -1 focusing order and nearly complete suppression of 0 and +1 orders. This is done using tooling capable of producing optics with 800 mm apertures. A 4-level grating fabricated in glass at 300 mm aperture is shown to have <15  nm rms holographic phase error. Glass FZLs have also been used as mandrels for casting zero-thermal-expansion, 20 µm thick polymer films created with the 4-level structure as a route to mass replication of efficient diffractive membranes for ultralight segmented space-based telescope applications.

The Membrane Optical Imager Real-time Exploitation (MOIRE) program is developing technology to reduce the mass of large optical space telescopes through the use of a membrane primary optical element. Applications in astronomy and Earth observation envision apertures in excess of 10 m in diameter, which are too massive to launch even with the best current lightweight mirror designs. The primary aperture of the MOIRE telescope is a transmissive membrane etched with a diffraction pattern that achieves as much as a factor of 7 in mass savings per unit aperture area compared to lightweight mirrors. The transmissive primary significantly reduces the sensitivities to out of plane motion as compared to reflective systems while at the same time reducing the manufacturing time and costs. This paper focuses on the ground demonstration of the MOIRE telescope concept that traces to the design of a geosynchronous space-based demonstration system with a 10 m primary aperture. The primary purpose of the ground demonstration, or Brassboard, is to prove the ability to capture a high-quality scene image using diffractive membrane collection optics with narrowband incoherent spectral illumination. The Brassboard demonstrates the manufacturability and efficacy of the optical train, in particular the segmented diffractive optical elements of the membrane primary and the glass chromatic dispersion corrector. While the initial goal for the broadband optical image quality was to show tracability to an equivalent NIIRS 3.5 rating, the test bed setup at the time of this writing permits only a single diffractive element to be used for imaging, resulting in an expected equivalent NIIRS performance of 2.8. Images taken with the test bed yield a NIIRS value of 2.3, where the 0.5 knockdown in performance is a result of laboratory humidity and atmospheric turbulence. The MOIRE ground demonstration test bed establishes the ability to capture images using a diffractive telescope with a membrane primary, proving that a larger, lighter, and cheaper telescope can be manufactured and used to provide imagery of interest.

Kepler is NASA's first space mission dedicated to the study of exoplanets. The primary scientific goal is statistical-to estimate the frequency of planetary systems associated with sun-like stars, especially the detection of earth-size planets in the habitable zones. Kepler was launched into an Earth-trailing heliocentric "drift-away"orbit (period 372 days) in March 2009. The instrument detects the faint photometric signals of transits of planets across the stellar disks of those systems with orbital planes fortuitously oriented in our line of sight. Since the probability of such alignments is small, Kepler must observe a large number of stars. In fact, Kepler is monitoring approximately 150,000 stars with a 30-min cadence. The scientific goals led to the choice of a classical Schmidt telescope, and requirements on field-of-view, throughput, spectral bandpass, image quality, scattered light, thermal and opto-mechanical stability, and in-flight adjustment authority. We review the measurement requirements, telescope design, prelaunch integration, alignment, and test program, and we describe the in-flight commissioning that optimized the performance. The stability of the flight system has enabled increasing recognition of small effects and sophistication in data processing algorithms. Astrophysical noise arising from intrinsic stellar variability is now the dominant term in the photometric error budget. (C) The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

X-ray telescope architectures currently being examined for future missions such as concepts like the International X-ray Observatory (IXO) are composed of thousands of extremely thin mirror elements (0.2 to 0.4 mm thick) arranged in closely spaced arrays. The precise positioning, integration, and testing of those optical elements are some of the fundamental challenges for fabrication of future X-ray telescopes. We will describe a novel pneumatic actuator and initial testbed results for positioning a single mirror and subsequently an array of mirrors.

The desire to field space-based telescopes with apertures in excess of 10 meter diameter is forcing the development of extreme lightweighted large optics. Sparse apertures, shell optics, and membrane optics are a few of the approaches that have been investigated and demonstrated. Membrane optics in particular have been investigated for many years. The majority of the effort in membrane telescopes has been devoted to using reflective membrane optics with a fair level of success being realized for small laboratory level systems; however, extending this approach to large aperture systems has been problematic. An alternative approach in which the membrane is used as a diffractive transmission element has been previously proposed, offering a significant relaxation in the control requirements on the membrane surface figure. The general imaging principle has been demonstrated in 50-cm-scale laboratory systems using thin glass and replicated membranes at long f-number (f/50). In addition, a 5-meter diameter f/50 transmissive diffractive optic has been demonstrated, using 50-cm scale segments arrayed in a foldable origami pattern. In this paper we discuss Membrane Optical Imager Real-time Exploitation (MOIRE) Phase 1 developments that culminated in the development and demonstration of an 80 cm diameter, off-axis, F/6.5 phase diffractive transmissive membrane optic. This is a precursor for an optic envisioned as one segment of a 10 meter diameter telescope. This paper presents the demonstrated imaging wavefront performance and collection efficiency of an 80 cm membrane optic that would be used in an F/6.5 primary, discusses the anticipated areal density in relation to existing space telescopes, and identifies how such a component would be used in previously described optical system architectures.

Kepler is NASA's first space mission dedicated to the study of exoplanets. The primary scientific goal is statistical - to estimate the frequency of planetary systems associated with sun-like stars, especially the detection of earth-size planets in the Habitable Zones. Kepler was launched into an Earth-trailing heliocentric "drift-away" orbit (period = 372 days) in March 2009. The instrument detects the faint photometric signals of transits of planets across the stellar disks of those systems with orbital planes fortuitously oriented in our line-of-sight. Since the probability of such alignments is small Kepler must observe a large number of stars. In fact, Kepler is monitoring approximately 150,000 stars with a 30-minute cadence. These scientific requirements led to the choice of a classical Schmidt telescope, and requirements on field-of-view (FOV), throughput, spectral bandpass, image quality, scattered light, thermal and opto-mechanical stability and in-flight adjustment authority. We review the pre-launch integration, alignment and test program, and we describe the in-flight commissioning that optimized the optical performance of the observatory. The stability of the flight system has enabled increasing recognition of small effects and increasing sophistication in data processing algorithms. Astrophysical noise arising from intrinsic stellar variability is now the dominant term in the photometric error budget.

Measurement of the distance to an object can be done in a number of ways based on system constraints such as minimum or maximum range, range accuracy, measurement update rate, and system power, with a considerable variation in resulting system complexity.Active approaches used in laser rangefinders yield submillimeter accuracy in laboratory or survey exercises while time-of-flight or flash LIDAR yields centimeter-scale range accuracy from mapping platforms in low Earth orbit. High ranging sensitivity, in excess of one part in 10(6), can be achieved, but generally requires fairly sophisticated control of the output pulse phase, shape, and energy, and also relies on fairly high speed pulse detection and processing.Passive approaches based purely on parallax imaging can determine distances to centimeter accuracies over moderate distances. The accuracy that can be achieved with this type of system is highly dependent on the overall SNR and the parallax angle, with a range sensitivity of one part in 1000 being typical for this approach.A low-cost passive range metrology system is described based on geometrical imaging with distance measurement sensitivity to better than one part in 10,000. The approach uses knowledge of the relationship between features on the target and the imaging parameters of the metrology camera, as in the parallax/centroid approach, but incorporates a specific target encoding that optimizes the performance. Results are presented using a standard machine vision camera in room ambient lighting conditions, showing a range sensitivity of 100 microns with a target-camera separation of 1200 mm.

The Advanced Technology Large-Aperture Space Telescope (ATLAST) is a set of mission concepts for the next generation of UVOIR space observatory with a primary aperture diameter in the 8-m to 16-m range that will allow us to perform some of the most challenging observations to answer some of our most compelling questions, including Is there life elsewhere in the Galaxy? We have identified two different telescope architectures, but with similar optical designs, that span the range in viable technologies. The architectures are a telescope with a monolithic primary mirror and two variations of a telescope with a large segmented primary mirror. This approach provides us with several pathways to realizing the mission, which will be narrowed to one as our technology development progresses. The concepts invoke heritage from HST and JWST design, but also take significant departures from these designs to minimize complexity, mass, or both. Our report provides details on the mission concepts, shows the extraordinary scientific progress they would enable, and describes the most important technology development items. These are the mirrors, the detectors, and the high-contrast imaging technologies, whether internal to the observatory, or using an external occulter. Experience with JWST has shown that determined competitors, motivated by the development contracts and flight opportunities of the new observatory, are capable of achieving huge advances in technical and operational performance while keeping construction costs on the same scale as prior great observatories.

A key consideration in designing optical systems, instruments, or test setups requiring windows or beam combiners is the potential for ghost images to be produced from reflections off the window/combiner surfaces. These ghost images will affect the optical system performance and the level to which that performance can be demonstrated during verification testing. Two common solutions for this are to use anti-reflection coatings and to use wedged substrates. Each has performance implications when used in spectrally broadband systems. The use of coatings alone on windows/combiners results in modest reduction (<100X) of ghost image intensity that can be inadequate when using or testing systems designed to find weak targets near bright objects. Using wedged substrates to shift ghost images outside an image region of interest will introduce chromatic aberrations that limit the fundamental broadband system imaging performance. In this paper we present design parameters for window/combiner assemblies that shift ghost images from a region of interest while controlling the chromatic aberrations to a level whereby the system imaging performance is not adversely affected even for broadband imaging systems with high angular resolution. We then present an example demonstrating the performance of a typical low dispersion, ghost-controlled window/combiner assembly.

The Kepler instrument is designed to detect Earth size planets in the "habitable zone" orbiting 9<mv< 16, F through M type stars. A 0.95 m aperture Schmidt telescope feeds the 96 million pixel Kepler focal plane array resulting in similar to 13 degrees diameter FOV, so that greater than 100,000 suitable stars in the FOV are continuously monitored over a three and a half year mission. Detection of planetary transits is made possible through 20 ppm differential photometry using pixel data from a focal plane array specifically developed for Kepler. The Kepler focal plane array is suspended above the primary mirror and consists of twenty one 2K x 2K Science CCD modules mounted on a curved Invar substrate with four output taps per module. Four fine guidance sensor (FGS) CCD modules are mounted to the corners of the Invar substrate to gather additional pointing information for the Attitude Control System in order to attain the required <2.5 milli-pixel pointing accuracy. A space staring radiator and a closed loop thermal control system maintains the CCD module temperatures at -85 degrees C with <10mK thermal stability. Low noise electronics reads out both the Science and FGS CCD modules at a 3 MHz pixel rate. In order to achieve a 4-sigma detection of an Earth-sized planet orbiting a 12th magnitude Sun-like star, the overall noise budget allocates 150 e- to the read noise of each Science CCD module output. This paper discusses key elements of the Kepler focal plane array design, development, characterization and performance results.

Ball Aerospace has constructed a new collimator for interferometric and image quality testing of meter scale optical systems under cryogenic, vacuum conditions. Termed the Vertical Collimator Assembly (VCA), it features 1.5 m diameter off-axis parabolic and calibration flat mirrors. In order to preserve as large a volume as possible for the unit under test, the main platform is suspended inside its vacuum chamber by a hexapod, with the parabolic mirror mounted overhead. A simultaneous interferometer facilitates collimator alignment and monitoring, as well as wavefront quality measurements for the test unit. Diffusely illuminated targets may be employed for through-focus image quality measurements with pinholes and bar targets. Mechanical alignment errors induced by thermal and structural perturbations are monitored with a three-beam distance measuring interferometer to enable mid-test compensation. Sources for both interferometer systems are maintained at atmospheric pressure while still directly mounted to the main platform, reducing vibration and stability problems associated with thermal vacuum testing. Because path lengths inside the ambient pressure vessels are extremely short, problems related to air turbulence and layering are also mitigated. In-chamber support equipment is insulated and temperature controlled, allowing testing while the chamber shrouds and test unit are brought to cryogenic temperatures.

The opto-mechanical design of the 6.6 meter James Webb Space Telescope(1) (JWST), with its actively-controlled secondary and 18-segment primary mirror, presents unique challenges from a system engineering perspective. To maintain the optical alignment of the telescope on-orbit, a process called wavefront sensing and control (WFS & C) is employed to determine the current state of the mirrors and calculate the optimal mirror move updates. The needed imagery is downloaded to the ground, where the WFS & C algorithms to process the images reside, and the appropriate commands are uploaded to the observatory. Rather than use a dedicated wavefront sensor for the imagery as is done in most other applications, a science camera is used instead.For the success of the mission, WFS & C needs to perform flawlessly using the assets available among the combination of separate elements (ground operations, spacecraft, science instruments, optical telescope, etc.) that cross institutional as well as geographic borders. Rather than be yet another distinct element with its own set of requirements to flow to the other elements as was originally planned, a novel approach was selected. This approach entails reviewing and auditing other documents for the requirements needed to satisfy the needs of WFS & C. Three actions are taken: (1) when appropriate requirements exist, they are tracked by WFS & C; (2) when an existing requirement is insufficient to meet the need, a requirement change is initiated; and finally (3) when a needed requirement is missing, a new requirement is established in the corresponding document. This approach, deemed a "best practice" at the customer's independent audit, allows for program confidence that the necessary requirements are complete, while still maintaining the responsibility for the requirement with the most appropriate entity.This paper describes the details and execution of the approach; the associated WFS & C requirements and verification documentation; and the implementation of the primary database tool for the project, DOORS (Dynamic Object-Oriented Requirements System).

From its orbit around the Earth-Sun second Lagrange point some million miles from Earth, the James Webb Space Telescope (JWST) will be uniquely suited to study early galaxy and star formation with its suite of infrared instruments. To maintain exceptional image quality using its 6.6 meter segmented primary mirror, wavefront sensing and control (WFS&C) is vital to ensure the optical alignment of the telescope throughout the mission. WFS&C design architecture includes using the Near-Infrared Camera (NIRCam) to provide imagery for ground-resident image processing algorithms which determine the optimal alignment of the telescope. There are two distinct mission phases for WFS&C, both of which use algorithms and NIRCam imagery to determine the required segment updates. For the first phase, WFS&C commissioning, the telescope is taken from its initial deployed state with each of the 18 primary mirror segments acting like independent telescopes, to its final phased state with each segment acting in concert as a part of a single mirror. The second phase, Wavefront Monitoring and Maintenance, continues for the rest of the mission. Here the wavefront quality is evaluated, and when needed, the mirror positions are updated to bring it back to an optimal configuration. This paper discusses the concept of operations for the commissioning and on-going maintenance of the telescope alignment using WFS&C.

Precise testbeds are required to investigate the physics and engineering aspects of suppressing extrasolar starlight sufficiently to discern faint companion planets. In addition, testbeds that can simultaneously produce star and planet stimuli will be necessary ground support equipment for. evaluating instruments designed for imaging and characterizing extrasolar planets. Integral to this is the ability to represent the broad spectral bands and relative geometry of stars and planets. We have built upon the Terrestrial Planet Finder Coronagraph (TPF-C) requirements as well as those of programs like Extrasolar Planet Imaging Coronagraph (EPIC) and Eclipse to develop a star/planet simulator (SPS) that, in conjunction with other testbed modules, can facilitate the pursuit of pertinent questions. The star/planet simulator developed has a broadband visible light source that illuminates independently adjustable star and planet sources (angular separation and orientation, relative magnitude). It is capable of providing either collimated or direct imaged light to proposed instruments and can be configured to produce the source stimuli in a vacuum environment. We will describe the physical set-up, measurements, and initial observations as well as the plans for combining with a coronagraphic testbed.

The one-meter Testbed Telescope (TBT) has been developed at Ball Aerospace to facilitate the design and implementation of the wavefront sensing and control (WFS&C) capabilities of the James Webb Space Telescope (JWST). The TBT is used to develop and verify the WFS&C algorithms, check the communication interfaces, validate the WFS&C optical components and actuators, and provide risk reduction opportunities for test approaches for later full-scale cryogenic vacuum testing of the observatory. In addition, the TBT provides a vital opportunity to demonstrate the entire WFS&C commissioning process. This paper describes recent WFS&C commissioning experiments that have been performed on the TBT.

The use of wavefront measurements to deduce the state of multiple optics in a telescope beam train - their misalignments and figure errors - can be confused by the fact that there are multiple potential sources for the same measured error. This talk applies Kalman filtering techniques as a tool for separating true telescope errors from artifactual testing errors in the alignment and testing of NASA's James Webb Space Telescope, a large segmented-aperture cryogenic telescope to be launched after 2010.