Paul Glenn

Performance of ion-figured silicon carbide SUMER telescope mirror in the vacuum ultraviolet

Measured and theoretical encircled energy and small-angle scatter of the telescope mirror (SST) of the solar ultraviolet measurements of emitted radiation (SUMER) instrument are compared at the wavelength of 123.6 nm. Mirror performance modeling was accomplished with the Optical Surface Analysis Code software package. The modeling is based on measured mirror-surface figure error data and roughness characteristics covering all important spatial frequencies that affect imaging in the vacuum ultraviolet wavelength region. Mirror-surface errors were measured with a Zygo Mark IV interferometer, Bauer Model 200 Profiler, and WYKO Topo 2-D (two-dimensional) interferometer. Performance of the SST mirror, including encircled energy and small-angle scatter, was also directly measured. A good agreement is found between measured and theoretical encircled energy within 6 arcsec and small-angle scatter up to ~50 arcmin from the peak. The 80% encircled energy diameter of the SST mirror is ~1.9 arcsec, and the amount of scattered light drops to approximately 1.0 × 10(-10) of peak irradiance (normalized to 1 arcsec(2) in the focal plane) 50 arcmin from the peak. Vacuum ultraviolet performance of the mirror is degraded primarily by midfrequency errors.

FISICA: the Florida image slicer for infrared cosmology and astrophysics

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.

Constellation-X spectroscopy x-ray telescope segmented optic assembly and alignment implementation

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.

Constellation-X SXT optical alignment Pathfinder 2: design, implementation, and alignment

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.

Constellation-X spectroscopy x-ray telescope assembly and alignment

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.

Performance prediction of the AXAF Technology Mirror Assembly using measured mirror surface errors

We have developed a math model relating the measured parameters of the Technology Mirror Assembly (TMA) to its final performance. This scalar scattering model is valid for large and small amplitude features. It allows the user to specify power spectral densities and/or autocovariance functions within any spatial bandwidth, including microroughness. We present new TMA data in the bandwidth of ~0.1-1000 mm-1, predicting performance and comparing them with x-ray test data. We also account for assembly, alignment, and particulate contamination. Finally, we comment on improved performance expected after repolishing.

X-ray testing Constellation-X optics at MSFC's 100-m facility

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.

Design, fabrication, assembly, and testing of the Florida Image Slicer for Infrared Cosmology and Astrophysics (FISICA) integral field unit

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.

Infrared coronagraph for the Terrestrial Planet Finder Mission II: Instrument design and performance

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.

The reconnection and microscale (RAM) solar-terrestrial probe

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.