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At least 145 records · Page 8

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NASA NTRS1980

Secondary mirror subassembly in the 2.4 m NASA optical telescope

The secondary mirror is a circular disc provided with a shoulder. Three clamps located 120 deg apart support the mirror shoulder. On one side of the mirror shoulder, a coated graphite-epoxy ring connects the three clamps. Three axial flexures with a low radial compliance extend out from a support platform constructed of coated graphite-epoxy box structs and invar corners, and provide a nominal in-plane zero coefficient of thermal expansion. In each invar corner piece, a ball joint provides a connection to a expansion. In each invar corner piece, a ball joint provides a connection to a six-degree-of-freedom adjustment system that can move the secondary mirror with a high degree of precision in defocus, decenter, and tilt. Thermal controls that maintain structural-element temperature variations within specified limits insure that the assembly exceeds stability and figure control requirements on the secondary mirror.

Ahmed, N.↗

NASA NTRS1982

Requirements and design of the graphite/epoxy structural elements for the optical telescope assembly of the space telescope

The production of the Space Telescope's Metering Truss Structure (MTS) and Focal Plane Structure (FPS), which are of graphite/epoxy, is described. Graphite/epoxy laminates were chosen because of their high strength and stiffness, low weight, and a controlled coefficient of thermal expansion approaching zero. Photocopy masters, which are dimensionally accurate and stable photographic reproductions of full size engineering drawings, allowed the exact assembly of bonded or bolted parts by assembly mechanics, cutting costs and speeding production. While moisture absorption, high through-the-thickness coefficient of thermal expansion effects, and labor-intensive layup costs are potentially problematic in some cases, it is expected that solutions can be found through analytical and developmental programs.

Golden, C. T.↗

NASA NTRS1985

An overview of optical telescope technology

Telescopes had tended to follow established designs until costs made it essential to look toward significant departures from conventional designs. Attempts to introduce some new concepts were without success until the Multiple Mirror Telescope broke the established pattern. Now several new possibilities are being engineered for the very large telescopes of the future.

Meinel, A. B.↗

NASA NTRS1986

The measured performance of a grazing incidence relay optics telescope for solar X-ray astronomy

The design, fabrication, and test performance of a grazing-incidence diverging magnifier (GIDM) for use in high-resolution X-ray imaging of the solar corona are described. The GIDM, designed to be mounted in front of the focus of a 30.48-cm Wolter-Schwarzschild primary, is an Ni-coated Be hyperboloid-hyperboloid structure of principal diameter 3.15 cm; the two components are mounted on a central steel plate which acts as a support and spacer. The combined instrument has overall length 1.9 m, effective focal length 5.4 m, and plate scale 26.0 micron/arcsec. In point- and line-source measurements in an 89.5-m vacuum test facility, the on-axis resolution is shown to be equal to that of the primary alone. The field of view for 1-arcsec resolution is limited to 1.25 arcmin in radius, but the effective-area limitation is less significant when CCD detectors of high quantum efficiency are used instead of film.

Moses, Dan↗

NASA NTRS1988

Design of the Extreme Ultraviolet Explorer long-wavelength grazing incidence telescope optics

Designing optics for photometry in the long-wavelength portion of the EUV spectrum (400-900) A) poses different problems from those arising for optics, operating shortward of 400 A. The available filter materials which transmit radiation longward of 400 A are also highly transparent at wavelengths shortward of 100 A. Conventional EUV optics, with grazing engles of less than about 10 deg, have very high throughput in the EUV, which persists to wavelengths shortward of 100 A. Use of such optics with the longer-wavelength EUV filters thus results in an unacceptably large soft X-ray leak. This problem is overcome by developing a mirror design with larger graze angles of not less than 20 deg, which has high throughput at wavelengths longer than 400 A but at the same time very little throughput shortward of 100 A.

Finley, David S.↗

NASA NTRS1992

System concepts for a series of lunar optical telescopes

The Lunar Telescope Working Group of the Marshall Space Flight Center, NASA, has conducted conceptual studies of an evolutionary family of UV/ optical/IR telescopes to be based on the lunar surface. Included are: (1) the 16-m aperture Large Lunar Telescope; (2) the 4-m aperture precursor Lunar Cluster Telescope Experiment; and (3) the 2-m Lunar Transit Telescope proposed by John McGraw of the Steward Observatory. Development and emplacement of these advanced astronomical facilities would parallel the buildup of an initial lunar exploration site, an early lunar outpost, and a permanent lunar base. The Working Group has examined the feasibility of constructing such telescopes and assessed technology, subsystem, system, transportation, and operations requirements for their development and emplacement. Influences of the lunar environment and site selection on telescope design and operation were also evaluated.

Nein, Max E.↗

NASA NTRS1992

Design of a support and foundation for a large lunar optical telescope

Design analysis and considerations are presented for the support structure and the foundation of the 16-m large lunar telescope (LTT). The proposed graphite/magnesium composite hexapod structure will support the 16-m mirror through a gimbal and trunnion assembly, with each hexapod leg consisting of seven 51-mm diameter 2-mm thick tubes bundled together. The foundation consists of three 152-cm diameter spud-can type footings. Results of the finite element analysis of the load-displacement characteristics of the support structure and the foundation are reported.

Chua, Koon M.↗

NASA NTRS2004

Multivariable Parametric Cost Model for Ground Optical: Telescope Assembly

A parametric cost model for ground-based telescopes is developed using multi-variable statistical analysis of both engineering and performance parameters. While diameter continues to be the dominant cost driver, diffraction limited wavelength is found to be a secondary driver. Other parameters such as radius of curvature were examined. The model includes an explicit factor for primary mirror segmentation and/or duplication (i.e. multi-telescope phased-array systems). Additionally, single variable models based on aperture diameter were derived.

Stahl, H. Philip↗

NASA NTRS2005

Spherical Primary Optical Telescope (SPOT): An Architecture Demonstration for Cost-effective Large Space Telescopes

This paper summarizes efforts underway at the Goddard Space Flight Center to demonstrate a new type of space telescope architecture that builds on the rigid, segmented telescope heritage of the James Webb Space Telescope but that solves several key challenges for future space telescopes. The architecture is based on a cost-effective segmented spherical primary mirror combined with a unique wavefront sensing and control system that allows for continuous phasing of the primary mirror. The segmented spherical primary allows for cost-effective 3-meter class (eg, Midex and Discovery) missions as well as enables 30-meter telescope solutions that can be manufactured in a reasonable amount of time and for a reasonable amount of money. The continuous wavefront sensing and control architecture enables missions in low-earth-orbit and missions that do not require expensive stable structures and thermal control systems. For the 30-meter class applications, the paper discusses considerations for assembling and testing the telescopes in space. The paper also summarizes the scientific and technological roadmap for the architecture and also gives an overview of technology development, design studies, and testbed activities underway to demonstrate it s feasibility.

Feinberg, Lee↗

NASA NTRS2004

Spherical Primary Optical Telescope (SPOT): An Architecture Demonstration for Cost-effective Large Space Telescopes

This paper summarizes efforts underway at the Goddard Space Flight Center to demonstrate a new type of space telescope architecture that builds on the rigid segmented telescope heritage of the James Webb Space Telescope but that solves several key challenges for future space telescopes. The architecture is based on a cost-effective segmented spherical primary mirror combined with a unique wavefront sensing and control system that allows for continuous phasing of the primary mirror. The segmented spherical primary allows for cost-effective 3-meter class (e.g., Midex and Discovery) missions as well as enables 30-meter telescope solutions that can be manufactured in a reasonable amount of time and for a reasonable amount of money. The continuous wavefront sensing and control architecture enables missions in low-earth-orbit and missions that do not require expensive stable structures and thermal control systems. For the 30-meter class applications, the paper discusses considerations for assembling and testing the telescopes in space. The paper also summarizes the scientific and technological roadmap for the architecture and also gives an overview of technology development, design studies, and testbed activities underway to demonstrate its feasibility.

Feinberg, Lee D.↗

NASA NTRS1994

SIRTF Telescope Optical Engineering

SIRTF has undergone recent replanning to address new cost constraints while defining a scientifically compelling mission faithful to the Bahcall report priorities and responsive to recent scientific developments.

cryogenic infrared observatory heliocentric orbit ↗

NASA NTRS2005

Multivariable Parametric Cost Model for Ground Optical Telescope Assembly

A parametric cost model for ground-based telescopes is developed using multivariable statistical analysis of both engineering and performance parameters. While diameter continues to be the dominant cost driver, diffraction-limited wavelength is found to be a secondary driver. Other parameters such as radius of curvature are examined. The model includes an explicit factor for primary mirror segmentation and/or duplication (i.e., multi-telescope phased-array systems). Additionally, single variable models Based on aperture diameter are derived.

Stahl, H. Philip↗

NASA NTRS2011

Cost Modeling for Space Optical Telescope Assemblies

Parametric cost models are used to plan missions, compare concepts and justify technology investments. This paper reviews an on-going effort to develop cost modes for space telescopes. This paper summarizes the methodology used to develop cost models and documents how changes to the database have changed previously published preliminary cost models. While the cost models are evolving, the previously published findings remain valid: it costs less per square meter of collecting aperture to build a large telescope than a small telescope; technology development as a function of time reduces cost; and lower areal density telescopes cost more than more massive telescopes.

Stahl, H. Philip↗

NASA NTRS2012

Prospects for Observing Ultracompact Binaries with Space-Based Gravitational Wave Interferometers and Optical Telescopes

Space-based gravitational wave interferometers are sensitive to the galactic population of ultracompact binaries. An important subset of the ultracompact binary population are those stars that can be individually resolved by both gravitational wave interferometers and electromagnetic telescopes. The aim of this paper is to quantify the multimessenger potential of space-based interferometers with arm-lengths between 1 and 5 Gm. The Fisher information matrix is used to estimate the number of binaries from a model of the Milky Way which are localized on the sky by the gravitational wave detector to within 1 and 10 deg(exp 2) and bright enough to be detected by a magnitude-limited survey.We find, depending on the choice ofGW detector characteristics, limiting magnitude and observing strategy, that up to several hundred gravitational wave sources could be detected in electromagnetic follow-up observations.

Littenberg, T. B.↗

NASA NTRS2014