SEARCH · Engineering Papers

Results for “large diameter telescope”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 109 records · Page 6

All sources NASA NTRS DOE OSTI

NASA NTRS2017

EXEP: Mountaintop Starshade Concept Study

Starshades are external occulters which would be used in conjunction with a space telescope. The starshade has a particular apodizing profile that effects strong suppression of starlight within the starshade’s shadow. Since starshades that would be used in space are large, typically 30 m diameter, performance is difficult to test on the ground at realistic scales. This paper examines the practical limits for testing starshades at smaller scales in the atmosphere and goes on to describe concepts for testing starshades using ground based telescopes and using starshades for astronomical observations.

Capps, R.↗

NASA NTRS1985

Optical detection of large meteoroids in space

CCD sensors placed across the focal plane of large Schmidt telescopes have great potential for detecting and measuring the very low flux in space of meteoroids with diameters larger than 1 meter. With the Palomar 'Big Schmidt', a detection rate of 1.4 per hour is obtained for meteoroids between 0.6 and 200 meters in diameter. For the Baker-Nunn 'Satellite Tracking Camera', the corresponding rate is about 0.8 per hour. The key to obtaining such high detection rates derives from approximately setting the sensor integration time equal to the time it takes a meteoroid to cross a pixel field of view. This minimizes signal to noise problems and is accomplished, in practice, by multiple summing of short integration time data records to obtain data records of longer effective integration times.

Zook, H. A.↗

NASA NTRSDate not supplied

TriTruss Packaging and Deployment Trade Study

An architecture and feasibility study of next generation In-Space Assembled Telescopes (iSAT) concluded that robotic in-space assembly of modular components is necessary to enable large (>15-meter diameter) primary apertures. The iSAT study recommended that the foundational structure be assembled from modular TriTruss modules that are packaged for launch, deployed on-orbit and robotically assembled into the final configuration. This paper will describe and summarize the results of a trade study that investigated viable concept of operations (ConOps) for the packaging and deployment (P&D) of individual planar TriTruss modules that could be assembled to form a large aperture iSAT. The ideal TriTruss P&D concept is defined as one that: allows for efficient packaging; has sufficient geometric versatility to be launch vehicle independent; provides a stiff and lightweight structure; has low mechanical complexity; and has component modularity. The P&D concept should allow for prelaunch subsystem or utility integration if required. The concept would be kinematically simple and be robotically deployed using a minimum number of specialized tools. In this first phase of an ongoing more comprehensive trade study, concepts were proposed and then evaluated based on initial metrics representing features of an ideal P&D concept. The P&D concepts evaluated are categorized as: core collapse, face collapse, and erectable structures. Sub-scale models were constructed to help understand the kinematics and mechanical complexity required to enable P&D. Based on a weighting scale, the most promising candidate P&D concepts have selected and will undergo more rigorous structural design, analysis, and testing in the study’s next phase. The ultimate goal of the comprehensive trade study will be to recommend a single TriTruss design and associated P&D concept that will be built and evaluated at NASA Langley Research Center’s In-Space Assembly Laboratory.

in-space assembly (ISA)↗

NASA NTRS2010

Large High Performance Optics for Spaceborne Missions: L-3 Brashear Experience and Capability

Brashear is a division of L-3 Communications, Integrated Optical Systems. Brashear is well known for the ground-based telescopes it has manufactured at its facilities and delivered to satisfied customers. Optics from meter-class up to 8.3 meters diameter have been fabricated in Brashear's facilities. Brashear has demonstrated capabilities for large spaceborne optics. We describe in this paper both legacy and new Brashear capabilities for high performance spaceborne optics.

Canzian, Blaise↗

NASA NTRS1984

A case for Gohrem - Geosynchronous orbit high resolution earth monitoring

Although the constant viewing geometry of the geostationary orbit simplifies quantitative monitoring of study areas, the high satellite altitude, in conjunction with the need for high spatial resolution, leads to large and complex sensors and spacecraft. State-of-the-art linear array detectors and a telescope of 1 m diameter and 10 m focal length can meet the requirements in question, which include a scan rate of the ground of at least 25 km/sec, the ability to cover a 150 X 150-km scene every several minutes, and an instantaneous field of view of 50 m in the visible portion of the spectrum and 1000 m in the IR.

Otterman, J.↗

NASA NTRS1986

Development of the EXITE detector - A new imaging detector for 20 - 300 keV astronomy

The development and testing of a detector to be used in the Energetic X-ray Imaging Telescope Experiment (EXITE) are reported. It consists of a 34 cm diameter NaI(Tl) crystal coupled directly to a single large image intensifier tube with associated silicon PIN diode readout. The measured spatial and energy resolutions at 122 keV are 6mm (FWHM) and 9 percent (FWHM), respectively. This energy resolution is about 50 percent better than that of any previously flown hard X-ray experiment. These resolutions decrease with the square root of the energy of the incident X-ray, indicating that they are determined by the number of photons emitted in the NaI(Tl) scintillator light flash.

Garcia, M. R.↗

NASA NTRS2017

Optical Design of the STAR-X Telescope

Top-level science goals of the Survey and Time-domain Astrophysical Research eXplorer (STAR-X) include: investigations of most violent explosions in the universe, study of growth of black holes across cosmic time and mass scale, and measure how structure formation heats majority of baryons in the universe. To meet these goals, the field-of-view of the telescope should be about 1 square-degree, the angular resolution should be 5 arc-seconds or below across large part of the field-of-view. The on-axis effective area at 1 KeV should be about 2,000 sq cm. Payload cost and launch considerations limit the outer diameter, focal length, and mass to 1.3 meters, 5 meters, and 250 kilograms, respectively. Telescope design is based on a segmented meta-shell approach we have developed at Goddard Space Flight Center for the STAR-X telescope. The telescope shells are divided into 30-degree segments. Individual telescopes and meta-shells are nested inside each other to meet the effective area requirements in 0.5 - 6.0 KeV range. We consider Wolter-Schwarzschild, and Modified-Wolter-Schwarzschild telescope designs as basic building blocks of the nested STAR-X telescope. These designs offer an excellent resolution over a large field of views. Nested telescopes are vulnerable to stray light problems. We have designed a multi-component baffle system to eliminate direct and single-reflection light paths inside the telescopes. Large number of internal and external baffle vane structures are required to prevent stray rays from reaching the focal plane. We have developed a simple ray-trace based tool to determine the dimensions and locations of the baffles. In this paper, we present the results of our trade studies, baffle design studies, and optical performance analyses of the STAR-X telescope.

Saha, Timo T.↗

NASA NTRS2017

Design of the STAR-X Telescope

Saha, Timo T.↗

NASA NTRS1980

Large Deployable Reflector (LDR)

The feasibility and costs were determined for a 1 m to 30 m diameter ambient temperature, infrared to submillimeter orbiting astronomical telescope which is to be shuttle-deployed, free-flying, and have a 10 year orbital life. Baseline concepts, constraints on delivery and deployment, and the sunshield required are examined. Reflector concepts, the optical configuration, alignment and pointing, and materials are also discussed. Technology studies show that a 10 m to 30 m diameter system which is background and diffraction limited at 30 micron m is feasible within the stated time frame. A 10 m system is feasible with current mirror technology, while a 30 m system requires technology still in development.

Alff, W. H.↗

NASA NTRS2019

Modular Active Self-Assembling Space Telescope Swarms

The Phase I study included a detailed exploration of a specific mission concept based on this architecture - a 31-meter diameter version of the LUVOIR (Large Ultraviolet Optical Infrared Surveyor) mission concept with the same wavelength coverage and wave-front quality requirements. The study focused on establishing the feasibility of the proposed concept with respect to what were identified as the most challenging aspects of the mission: the ability to find orbital solutions using solar sail propulsion for both the initial transfers and subsequent rendezvous trajectories; and the ability to generate the required final primary mirror surface out of uniformly polished individual module mirrors using deformation via mechanical degrees of freedom. As a result of the Phase I work it was shown that both orbital and optical solutions are feasible, but will require technology advancement in multiple key areas. In particular, improvements to solar sail areal densities and loading factors will allow us to more easily find fully general solutions for the transfer trajectories, while lower mass, ultra-precise cryogenic linear actuators will likely be needed to form the final mirror shape. However, it was found that current state of the art in solar sails was sufficient for rendezvous trajectories once on-orbit, that the requisite wave-front quality could be achieved with actuation requirements not more stringent than those being carried by LUVOIR, and that there exists a well-defined design space in which the module spacecraft designs can be optimized. The technology development required to progress this work overlaps significantly with numerous NASA technology roadmaps, as well as the Exoplanet Exploration Program's technologies gap list, meaning that continued development of this concept would directly benefit a variety of NASA programs, as well as enabling the completely unique capabilities provided by a 31-meter optical space telescope...Our architecture requires only a single module type allowing us to directly leverage the cost and efficiency benefits of true mass production, in direct contrast to previously explored self-assembling swarm concepts, which typically include multiple module types.

Astronomy↗

NASA NTRS1994

The giant molecular cloud Monoceros R2. 1: Shell structure

We have obtained a 45 sec resolution, Nyquist-sampled map in CO J = 1-0 covering approximately a 3 deg x 3 deg region of the giant molecular cloud Monoceros R2. The map consists of 167,000 spectra observed with the 15 element focal-plane array system on the FCRAO 14 m telescope. The data reveal that the large-scale structure of Mon R2 is dominated by a is approximately 30 pc diameter largely hemispherical shell containing approximately 4 x 10(exp 4) solar mass of molecular material and expanding at approximately 3-4 km s(exp -1) with symmetric axis roughly along the line of sight. The dynamical timescale of the shell is estimated to be approximately 4 x 10(exp 6) yr, which is consistent with the age of main-sequence stars powering the clusters of reflection nebulea in this region. There is no evidence for a redshifted shell on the far side of the interior 'bubble,' which is largely devoid of molecular material. Distortions of the shell are obvious, suggesting inhomogeneity of the cloud and possible presence of a magnetic field prior to its formation. Dense clumps in Mon R2, including the main core and the GGD 12-15 core, appear to be condensations located on the large shell. The reflection nebulea with their illuminating stars as well as embedded IRAS sources suggest that triggered star formation has taken place over a large part of the Mon R2 shell.

Xie, Taoling↗

NASA NTRS2004

The Constellation-X Spectroscopy X-Ray Telescope

The status of technology development for the Constellation-X Spectroscopy X-ray Telescope (SXT) mirror is presented. The SXT mirror combines a large (1.6 m) aperture with modest (12 arc sec half power diameter) angular resolution and low mass (750 kg). The overall collecting area, larger than 9,600 square cm at 0.25 keV, requires high throughput, and thus nesting of a substantial number of thin reflectors. A phased development program is underway to develop reflectors, mounting and alignment approaches, and metrology techniques for components and the mirror has a whole. The latest results in all these areas are summarized, along with an overview of results of optical testing of reflector performance.

Petre, Robert↗

NASA NTRS2018

VLTI-GRAVITY Measurements of Cool Evolved Stars I. Variable Photosphere and Extended Atmosphere of the Mira Star R Peg

Context. Dynamic model atmospheres of Mira stars predict variabilities in the photospheric radius and in atmospheric molecular layers which are not yet strongly constrained by observations. Aim. Here we measure the variability of the oxygen-rich Mira star R Peg in near-continuum and molecular bands. Methods. We used near-infrared K-band spectro-interferometry with a spectral resolution of about 4000 obtained at four epochs between post-maximum and minimum visual phases employing the newly available GRAVITY beam combiner at the Very Large Telescope Interferometer (VLTI). Results. Our observations show a continuum radius that is anti-correlated with the visual lightcurve. Uniform disc (UD) angular diameters at a near-continuum wavelength of 2.24 m are steadily increasing with values of 8.7 0.1 mas, 9.4 0.1 mas, 9.8 0.1 mas, and 9.9 0.1 mas at visual phases of 0.15, 0.36, 0.45, 0.53, respectively. UD diameters at a bandpass around 2.05 m, dominated by water vapour, follow the near-continuum variability at larger UD diameters between 10.7 mas and 11.7 mas. UD diameters at the CO 2-0 bandhead, instead, are correlated with the visual lightcurve and anti-correlated with the near-continuum UD diameters, with values between 12.3 mas and 11.7 mas. Conclusions. The observed anti-correlation between continuum radius and visual lightcurve is consistent with an earlier study of the oxygen-rich Mira S Lac, and with recent 1D CODEX dynamic model atmosphere predictions. The amplitude of the variation is comparable to the earlier observations of S Lac, and smaller than predicted by CODEX models. The wavelength-dependent visibility variations at our epochs can be reproduced by a set of CODEX models at model phases between 0.3 and 0.6. The anti-correlation of water vapour and CO contributions at our epochs suggests that these molecules undergo different processes in the extended atmosphere along the stellar cycle. The newly available GRAVITY instrument is suited to conducting longer time series observations, which are needed to provide strong constraints on the model-predicted intra- and inter-cycle variability.

photospheric radius↗

NASA NTRS2001

A Geosynchronous Lidar System for Atmospheric Winds, Temperature, and Moisture Measurements

A geosynchronous Lidar would enable synoptic measurement of atmospheric winds; temperature; and moisture, which are key first-order variables of the Earth's weather equation. Simultaneous measurement of these parameters at fast revisit rates promises large advancements in our weather predictive skills. Such capabilities would: a) yield greatly improved initial conditions for models, b) make obsolete existing (discrete) measurement approaches which are both costly and cumbersome, and c) obviate the use of numerical techniques needed to correct data obtained using present methods. Additionally, simultaneous synoptic Lidar observations would lead to improvements in model parameters, and in our knowledge of small-scale weather processes. A Dial Lidar system could simultaneously measure winds, temperatures, and humidity through a combination of Doppler and Differential Absorption techniques. Also, such a system would provide basic aerosol (dry dust) measurement capabilities that could have an impact on Earth radiation budget measurements. On the technical side, a geosynchronous Lidar DAR system would require transmit optics of a few meters in diameter, a hundred meter diameter receive telescope, fineness of both optical systems scaled to the wavelength, and scanning for the transmit system. Potential technology issues include optical quality of large transmit and receive telescope optics, the large detector area needed, the transmit scanning system, signal detection (S/N ratio of detector system) for the extremely weak return signal at GEO, and power demands in the KW range.

Emmitt, Dave↗

NASA NTRS2010

First Earth-Based Detection of a Superbolide on Jupiter

Cosmic collisions can planets cause detectable optical flashes that range from terrestrial shooting stars to bright fireballs. On 2010 June 3 a bolide in Jupiter's atmosphere was simultaneously observed from the Earth by two amateur astronomers observing Jupiter in red and blue wavelengths, The bolide appeared as a flash of 2 s duration in video recording data of the planet. The analysis of the light carve of the observations results in an estimated energy of the impact of (0.9-4,0) x 10(exp 15) J which corresponds to a colliding body of 8-13 m diameter assuming a mean density of 2 g/cu cm. Images acquired a few days later by the Hubble Space Telescope and other large ground-based facilities did not show any signature of aerosol debris, temperature, or chemical composition anomaly, confirming that the body was small and destroyed in Jupiter's upper atmosphere. Several collisions of this size may happen on Jupiter on a yearly basis. A systematic study of the impact rate and size of these bolides can enable an empirical determination. of the flux of meteoroids in Jupiter with implications for the populations of small bodies in the outer solar system and may allow a better quantification of the threat of impacting bodies to Earth. The serendipitous recording of this optical flash opens a new window in the observation of Jupiter with small telescopes.

Hueso, R.↗

NASA NTRS1983

Large Deployable Reflector Science and Technology Workshop. Volume 2: Scientific Rationale and Technology Requirements

The scientific rationale for the large deployable reflector (LDR) and the overall technological requirements are discussed. The main scientific objectives include studies of the origins of planets, stars and galaxies, and of the ultimate fate of the universe. The envisioned studies require a telescope with a diameter of at least 20 m, diffraction-limited to wavelengths as short as 30-50 micron. In addition, light-bucket operation with 1 arcsec spatial resolution in the 2-4 microns wavelength region would be useful in studies of high-redshifted galaxies. Such a telescope would provide a large increase in spectroscopic sensitivity and spatial resolving power compared with existing or planned infrared telescopes.

Hollenbach, D.↗

NASA NTRS2007

Structural Feasibility Analysis of a Robotically Assembled Very Large Aperture Optical Space Telescope

This paper presents a feasibility study of robotically constructing a very large aperture optical space telescope on-orbit. Since the largest engineering challenges are likely to reside in the design and assembly of the 150-m diameter primary reflector, this preliminary study focuses on this component. The same technology developed for construction of the primary would then be readily used for the smaller optical structures (secondary, tertiary, etc.). A reasonable set of ground and on-orbit loading scenarios are compiled from the literature and used to define the structural performance requirements and size the primary reflector. A surface precision analysis shows that active adjustment of the primary structure is required in order to meet stringent optical surface requirements. Two potential actuation strategies are discussed along with potential actuation devices at the current state of the art. The finding of this research effort indicate that successful technology development combined with further analysis will likely enable such a telescope to be built in the future.

space telescopes↗

NASA NTRS1984

Support structures for large infrared telescopes

An infrared telescope requires an accuracy of its reflecting surfaces of less than a micrometer. Future missions may require such accuracy from telescopes that are 20 meters or larger in diameter. The structure for supporting such a telescope will most probably take the form of a deep truss. Various approaches for constructing the primary mirror in space are illustrated. One that employs automated deployment of interconnected reflector-structure modules was described in detail. Estimates were made of the precision obtainable with properly configured truss structures and the required ability of active control systems for achieving the desired accuracy.

Hedgepeth, J. M.↗