We will discuss the design, specification, construction, and assembly of the 4 mirror systems that make up the Solar
Dynamics Observatory (SDO) Atmospheric Imaging Array (AIA). We will include the extensive imaging performance
measurements made on the mirror throughout the post-polishing mirror processing period.
We report on the design, fabrication, and on-sky performance of the Florida Image Slicer for Infrared Cosmology and Astrophysics (FISICA) - a fully-cryogenic all-reflective image-slicing integral field unit for the FLAMINGOS near-infrared spectrograph. Designed to accept input beams near f/15, FISICA with FLAMINGOS provides R~1300 spectra over a 16x33-arcsec field-of-view on the Cassegrain f/15 focus of the KPNO 4-meter telescope, or a 6x12-arcsec field-of-view on the Nasmyth or Bent Cassegrain foci of the Gran Telescopio Canarias 10.4-meter telescope. FISICA accomplishes this using three sets of "monolithic" powered mirror arrays, each with 22 mirrored surfaces cut into a single piece of aluminum. We review the optical and opto-mechanical design and fabrication of FISICA, as well as laboratory test results for FISICA integrated with the FLAMINGOS instrument. Finally, we present performance results from observations with FISICA at the KPNO 4-m telescope and comparisons of FISICA performance to other available IFUs on 4-m to 8-m-class telescopes.
One of the key instruments on the Reconnection and Microscale (RAM) Solar-Terrestrial Probe mission is a normal incidence multilayer x-ray telescope designed to provide 10 milli-arc-sec imaging of the solar corona. To achieve this level of imaging it will be necessary to fabricate meter-class reflective optics with diffraction limited performance at 193 Angstroms. Because of the use of multilayer optics, surface micro-roughness must also be maintained at very low levels (a few Angstroms rms) to maintain good reflectance. To ease fabrication constraints and the sometimes competing requirements of micro-roughness and figure, we have explored a number of potential designs and fabrication approaches for RAM. Figure error budgets and optical designs are shown, demonstrating that RAM can be built with existing mirror fabrication technology.
We report on the design and status of the Florida Image Slicer for Infrared Cosmology and Astrophysics (FISICA) - a fully-cryogenic all-reflective image-slicing integral field unit for the FLAMINGOS near-infrared spectrograph. Designed to accept input beams near f/15, FISICA with FLAMINGOS provides R~1300 spectra over a 16x33-arcsec field-of-view on the Cassegrain f/15 focus of the KPNO 4-meter telescope, or a 6x12-arcsec field-of-view on the Nasmyth or Bent Cassegrain foci of the Gran Telescopio Canarias 10.4-meter telescope. FISICA accomplishes this using three sets of “monolithic” powered mirror arrays, each with 22 mirrored surfaces cut into a single piece of aluminum. We review the optical and opto-mechanical design and fabrication of FISICA, as well as laboratory test results for FISICA integrated with the FLAMINGOS instrument. We also discuss plans for first-light observations on the KPNO 4-meter telescope in July 2004.
We discuss the design, fabrication, assembly, and testing of the prototype Florida Image Slicer for Infrared Cosmology and Astrophysics (FISICA) Integral Field Unit (IFU). FISICA is intended for large telescopes with f/numbers close to f/15, such as the KPNO 4-m and GTC 10.4-m telescopes. It implements an image slicing approach, wherein the initial image plane is optically sliced into thin strips and the strips are optically rearranged end-to-end, whereupon the composite slit image is fed into a conventional spectrograph. We divide the field of view into 22 slices, while accommodating the entire f/15 viewing solid angle. The all-reflective instrument resides in a cryogenic dewar at the initial focal plane, and places the composite slit image output precisely at the initial focus, allowing it to interface to the existing FLAMINGOS spectrograph. The mirrors were diamond turned using various tool geometries and state-of-the-art, multi-axis tool control. The mirrors are made from a single billet of aluminum, and the optical bench and mounts are made of the same alloy as the mirrors for optimum performance during cryogenic cooling. We discuss the key design efforts, emphasizing tradeoffs among performance, volume, fabrication difficulty, and alignment requirements. We describe the fabrication, and present preliminary laboratory test results.
As NASA’s next facility-class x-ray mission, Constellation X will provide high-throughput, high-resolution spectroscopy for addressing fundamental astrophysical and cosmological questions. Key to the Constellation-X mission is the development of lightweight grazing-incidence optics for its Spectroscopy X-ray Telescopes (SXT) and for its Hard X-ray Telescopes (HXT). In preparation for x-ray testing Constellation-X SXT and HXT development and demonstration optics, Marshall Space Flight Center (MSFC) is upgrading its 100-m x-ray test facility, including development of a five degree-of-freedom (5-DoF) mount for translating and tilting test articles within the facility’s large vacuum chamber. To support development of alignment and assembly procedures for lightweight x-ray optics, Goddard Space Flight Center (GSFC) has prepared the Optical Alignment Pathfinder Two (OAP2), which will serve as a surrogate optic for developing and rehearsing x-ray test procedures. In order to minimize thermal distortion of the mirrors during x-ray testing, the Harvard-Smithsonian Center for Astrophysics (CfA) has designed and implemented a thermal control and monitoring system for the OAP2. CfA has also built an aperture wheel for masking and sub-aperture sampling of the OAP2 to aid in characterizing x-ray performance of test optics.
The Constellation-X SXT mirrors and housings continue to evolve toward a flight-like design. Our second-generation alignment housing, the Optical Alignment Pathfinder 2 (OAP2), is a monolithic titanium structure that is nested inside the OAP1 alignment jig, described in a previous paper (J. Hair, et. al., SPIE 2002). In order to perform x-ray tests in a configuration where the optical axis is horizontal, and continue to develop more flight-like structures, we needed to design a strong, but lightweight housing that would impart minimal deformations on the thin segmented mirrors when it is rotated from the vertical orientation used for optical alignment to the horizontal orientation that is used for x-ray testing. This paper will focus on the design of the OAP2 housing, and the assembly and alignment of the optics within the OAP1 plus OAP2 combination using the Centroid Detector Assembly (CDA). The CDA is an optical alignment tool that was successfully used for the HRMA alignment on the Chandra X-ray Observatory. In addition, since the glass we are using is so thin and flexible, we will present the response of the optical alignment quality of a Wolter-I segment to known deformations introduced in by the OAP1 alignment housing.
The Constellation-X mission will perform X-Ray science with improvements in energy resolution and effective area over its predecessor missions. The primary instrument on each of the four Constellation-X spacecraft is the Spectroscopy X-Ray Telescope (SXT). The SXT is a 1.6m diameter grazing incidence mirror assembly comprised of approximately 4000 optic elements. In order for the optic elements to work together to achieve the required 15 arcsec image resolution for the telescope, each optic must be aligned very precisely. To enable the alignment of the optic elements to the required tolerances, new technology must be developed through a series of technology demonstrators. The first step in this process is the production of the Optical Assembly Pathfinder (OAP). The OAP represents a small section, or module, of the complete SXT and has been designed to facilitate the evaluation and development of the optic element support, alignment, and adjustment concepts, processes, and procedures. To do this, one pair of optic elements, primary and secondary, will be aligned using optical alignment methods including the Centroid Detector Assembly (CDA) and Interferometry. Ten Optic Adjustment Arms will support the optic elements such that their position and figures can be adjusted. Currently, one section, the primary section, of the OAP has been assembled and is awaiting the installation of an optic element for testing.
The Constellation-X mission is a follow-on to the current Chandra and XMM missions. It will place in orbit an array of four identical X-ray telescopes that will work in unison, having a substantial increase in effective area, energy resolution, and energy bandpass over current missions. To accomplish these ambitious increases new optics technologies must be exploited. The primary instrument for the mission is the Spectroscopy X-Ray Telescope (SXT), which covers the 0.2 to 10 keV band with a combination of two x-ray detectors: a reflection grating spectrometer (RGS) with CCD readout, and
a micro-calorimeter. Mission requirements are an effective area of 15,000 cm2 near 1.25 keV, 6,000 cm2 near 6 keV, and a 15 arcsec (HPD) resolution requirement with a goal of 5 arcsec. The Constellation-X SXT uses a segmented design with lightweight replicated optics. A technology development program is being pursued with the intent of demonstrating technical readiness prior to the program new start. Key elements of the program include the replication of the optical elements, assembly and alignment of the optics into a complete mirror assembly and demonstration of production techniques needed for fabrication of multiple units. In this paper we present the development of SXT assembly and alignment techniques and describe recent work and current status on the first of these assemblies, the Optical Assembly Pathfinder, in which precision mechanical techniques and optical metrology are used to assemble and align the flexible optical elements.
NASA wants to launch a Terrestrial Planet Finder (TPF) mission in 2014 to detect and characterize Earth-like planets around nearby stars, perform comparative planetology studies, and obtain general astrophysics observations. The detection of a 30th magnitude planet located within 80 milli-arcseconds of a 5th (Visual) magnitude star is an exceptionally challenging objective. Observations in the thermal infrared (7-17 mm) are somewhat easier since the planet is 'only' 15m fainter than the star at these wavelengths, but many severe challenges must still be overcome, including: Designing a spacecraft, a telescope and an IR coronagraph for star-planet separations equal to λ/D;(i) Providing a stable (~30K) thermal environment for the optics and isolating them from vibration sources; (ii)Developing a deployment scheme for a 28-m space telescope that can fit in an existing launch vehicle; (iii) Minimizing telescope mass to enable launch to L2 or a driftway orbit with a single launch vehicle; (iv) Generating a manufacturing plan that will permit TPF to be developed at a reasonable cost and schedule; (v) Identifying the key enabling technologies for TPF. This paper describes the IR Coronagraph we designed during our recent TPF Mission Architecture study in an effort to meet these challenges.
NASA plans to launch a Terrestrial Planet Finder (TPF) mission in 2014 to detect and characterize Earth-like planets around nearby stars, to perform comparative planetology studies, and to obtain general astrophysics observations. As part of our recently completed TPF Mission Architecture study for NASA/JPL we developed the conceptual design for a Large Aperture IR Coronagraph that meets these mission objectives. This paper describes the optical design of the telescope and the coronagraph to detect and characterize exo-solar planets. The telescope design was optimized to provide a well-corrected image plane that is large enough to feed several instruments and control scattered light while accommodating packaging for launch and manufacturing limitations. The coronagraph was designed to provide a well corrected field of view with a radius > 5 arcsec around the star it occults in the 7-17 microns wavelength region. A design for this instrument as well as results of a system simulation model are presented. The methodology for wavefront error correction and control of scattered and diffracted light are discussed in some detail as they are critical parameters to enable detecting planets at separations of down to ~λ/D.
A hot, magnetized plasma such as the solar corona has the property that much of the physics governing its activity takes place on remarkably small spatial and temporal scales, while the response to this activity occurs on large scales. Observations from SMM, TRACE, SOHO and Yohkoh have shown that typical solar active regions have loops ranging in temperature from 0.5 to 10 MK, and flares up to 40MK. The spatial and temporal domains involved have been heretofore inaccessible to direct observations from Earth, so that theory has relied heavily on extrapolations from more accessible regimes, and on speculation. The RAM Solar-Terrestrial Probe consists of a set of carefully selected imaging and spectroscopic instruments that enable definitive studies of the dynamics and energetics of the solar corona.
We describe a new noncontacting approach for obtaining the full aperture, absolute aspheric profile of large optical surfaces. The metrology instrument is placed in close proximity to the test piece instead of at the center of curvature, and is thus equally useful for measuring concave, flat, and convex optics - even fast (low f-number) optics. It combines the data from multiple probes in a manner that makes the measurement completely self-referencing, and completely insensitive to any small relative rigid body motions between the instrument and the test piece. The relative compactness of the instrument combined with its inherent rigid body insensitivity make it suitable ultimately for in situ measurements. Furthermore, replacement of the noncontacting optical probes with contacting mechanical probes would make the instrument suitable for profiling ground surfaces to a very small fraction of a micron. We have built a prototype instrument to prove the concept, and have demonstrated sub-nanometer capabilities for the optical probes, with full surface figure accuracy capabilities of a few nanometers in an uncontrolled thermal environment. The full surface figure accuracy is improving as we implement modest environmental controls. In this paper, we first describe the underlying theory of the measurement approach, and then describe the prototype instrument. Finally, we summarize the measurements made to date, and discuss likely future applications and projected accuracies.
We have developed a new noncontacting approach for obtaining the full aperture, absolute aspheric profile of optical surfaces. The approach has many advantages for a wide range of optics, including self-referencing and motion-insensitive operation; extremely high accuracy; compact size; and the ability to test concave, flat and convex optics over a wide range of spatial frequencies. In a separate paper, we describe the underlying theory of operation, a prototype instrument, preliminary measurement results, and projected accuracies. In this paper, we discuss the specific advantages that are especially relevant for Extreme Ultra Violet (EUV) lithography components. These mirrors are responsible for the fabulously accurate imaging of the reticle onto the wafer. They therefore have typical surface accuracy requirements of a fraction of a nanometer, with the need to characterize the errors over an enormous range of spatial frequencies. The need to provide diffraction-limited imaging at EUV wavelengths over large Fields Of View (FOVs) and Numerical Apertures (NAs) puts a premium on freedom in the optical design. Specifically, the use of aspheres and convex mirrors can be of great help. Therefore, performance, FOV, and NA all benefit from the most accurate and flexible metrology. All of these factors make this new profiling technique well suited to the unique requirements of EUV lithography mirrors.
Rapid, three-dimensional profilometry with resolution similar to that of mechanical coordinate measuring machines has long been a goal of vision system developers. Some success has been had using structured light projectors, flying spot scanners and the like. However, these techniques are limited by restrictions on the height variation and stability of the target object. This paper describes a phase measuring projected fringe interferometer that overcomes many of these problems. Using data from a high speed mega pixel class camera viewing high precision spatial modulation of a periodic illumination pattern on the target, new software unwraps the surface phase information and rapidly computes a true three dimensional surface. An important capability of the software is to avoid errors due to islands of missing data or high slope regions on the target. Interchangeable camera lenses permit measurements of a wide range of object sizes with a height resolution ratio on the order of 20 microns per meter of test piece size. The current application of the instrument is measurement of structural deflections of hypersonic aircraft structural components. In previous work, the technique has successfully measured the profile of coins and jet engine turbine blades and the curvature of a human spine. We summarize the special qualities of this instrument that make it well suited to such a wide range of measurements. Finally, we discuss some preliminary experimental results and compare them with typical accuracy requirements.
The High Resolution Mirror Assembly (HRMA) of the Advanced X-ray Astrophysics Facility (Imaging) (AXAF-I) consists of four nested paraboloids and four nested hyperboloids, all of meter-class size, and all of which are to be assembled and aligned in a special 15 meter tower at Eastman Kodak Company in Rochester, NY. The goals of the alignment are (1) to make the images of the four telescopes coincident; (2) to remove coma from each individually; and (3) to control and determine the final position of the composite focus. This will be accomplished by the HRMA Alignment Test System (HATS), which is essentially a scanning Hartmann test system. The scanning laser source and the focal plane of the HATS are part of the Centroid Detector Assembly (CDA), which also includes processing electronics and software. In this paper we discuss the design and the measured performance of the CDA.
We have previously described a new noncontact profiling technique that involves measuring the test surface curvature on a point-by-point basis. Curvature is measured by simultaneously measuring the test surface slope at two slightly displaced locations. As the pair of sensing beams is scanned along the test piece, a profile of curvature is built, from which the height profile is deduced. The sensing of curvature eliminates the need for a reference surface, and makes the approach insensitive to all types of vibration and drift, both in surface height and in surface slope. In this paper, we discuss some of our more recent calibration and measurement efforts in testing steep optics. We also discuss test piece alignment. This aspect of metrology is always of concern, especially in the case of steep optics in general, and steep aspheres in particular. We show that the curvature profiling technique is inherently much less sensitive to unknown misalignments and variations in scanning geometry than a height profiling or slope profiling technique.
Metrology has historically been one of the most formidable hurdles in fabricating large, generalized aspheres. The heart of the problem is that exotic aspheres preclude the classical technique of interferometrically testing from the center of curvature with a spherical beam, driving the need for null correctors. Although the null corrector approach is feasible, the difficulty of certification and the fact that each corrector allows the testing of only a single aspheric form make it expensive and time consuming. The problems are of course much worse for large convex optics, where the center of curvature is not available. Finally, these problems only accentuate the problem of measuring figure during the transition from grinding to polishing. In this paper we discuss a new, non-interferometric instrument currently under development. Non-interferometric techniques are usually not chosen for aspheric metrology, either because they are too inaccurate, involve mechanical contact, or cannot accommodate a large test piece. Our approach is noncontacting and self-referencing, and can be easily expanded from its broadband capacity of 0.5 meter. The instrument consists of a three- dimensional coordinate reference system and a measurement head whose location is tracked within the reference system. The reference system involves no physical reference surfaces, but instead uses an arrangement of laser beams whose positions are monitored with position sensitive detectors. The measurement head uses a new autofocus technique that allows accurate testing even before the surface is polished. Using this head, there is no loss of knowledge during the tricky transition from grinding to polishing. We present here the overall instrument concept, as well as current status and expected performance levels.
The measurement of circularity of cylindrical grazing incidence optics is a formidable task, because required fabrication
accuracies are typically on the order of several micro-inches, with resulting measurement accuracies on the order of a
micro-inch or less. Such demanding accuracy requirements have evolved as the need for high resolution extreme
ultraviolet and X-ray systems has increased. Current measurement approaches involve rotating the element (or one or
more measurement probes) about the element's axis, and sensing the surface runout. Sensing can be mechanical or
interferometric, but in either case the approach is clearly sensitive to runout in the rotation itself. Even when multiple
probes are used to eliminate repeatable runout errors, nonrepeatable runout errors or drifts in probe position can
severely degrade accuracy. In this paper we discuss a new, noncontacting approach (patent pending) that involves
measuring the local circumferential curvature of the test piece by simultaneously measuring its circumferential slope at
two slightly displaced locations. As the pair of sensing beams is scanned along the circumference, a profile of curvature
is built, from which the circularity profile is deduced. The sensing of curvature not only makes the approach insensitive
to all types ofvibration and drift (both in surface height and in surface slope), but also makes it insensitive to runout
errors in the relative rotation. Thus, one can achieve absolute accuracies that are orders of magnitude smaller than
typical drifts and runouts. We summarize the special qualities of this approach which make it well suited to measuring
cylindrical optics, and which make it able to accommodate radii as small as twenty millimeters, working on either the
inside (concave) or the outside (convex) surface. Finally, we discuss some preliminary experimental results and
compare them with typical accuracy requirements.
The paper indicates the emerging requirements for profilometry instruments for use in the
fabrication and characterisation of modern optical systems. Important design principles are
covered, together with some of the problems which can be experienced. Examples of a number
of systems recently developed are given both stand alone systems and those which operate insitu
to the machining process.
In this paper we define a versatile new noncontacting profilometry approach that offers significant advantages in terms
of accuracy, robustness, and flexibility over conventional interferometric or slope measuring approaches. The approach
involves measuring the local curvature of the test piece by simultaneously measuring its slope at two slightly displaced
locations. As the pair of sensing beams is scanned along the test piece, a profile of curvature is built, from which the
height profile is deduced. The sensing of curvature eliminates the need for an interferometric reference surface, and
makes the approach insensitive to all types of vibration and drift, both in surface height and in surface slope. Thus, the
approach is extremely robust. We have already demonstrated sub-Angstrom accuracy for typical mid-spatial period
ranges extending from a fraction of a millimeter to tens of millimeters. In this paper, however, we emphasize several
extensions of the measurement technique that make it an extremely versatile profiling approach for a variety of
metrology needs. These extensions include beam expansion to make very long scans possible; measurement of
circularity and cone angle of near cylindrical optics; and measurement of absolute flatness. We summarize our
experimental results obtained to date, and define expected performance levels for these extended measurement
functions.
Grazing incidencesystems, such as extreme ultraviolet and x-ray telescopes, produce images that differ qualitatively from those of conventional normal incidence systems. Among the more well known effects
are increased scatter due to the short radiation wavelengths, and pronounced pupil diffraction patterns due to the high obscuration ratios. However,
a much less well known effect is the rapidly increasing intensity very near the center of the image. Within a substantial part of the image core,
the intensity can be shown to increase inversely with the image radius ("l/r" behavior). This behavior applies to both pupil diffraction and scatter
effects. One ofthe important implications is that the full-width-half-maximum (FWHM) for the image is inherently and misleadingly small and is thus
not a suitable image descriptor for grazing incidence systems. In this paper, we first review the well-known scatter and diffraction effects. We
then give some intuitive explanations for the less well known behavior of the intensity, derive the mathematics to define the effect quantitatively,
and give some examples.
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