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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.

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At least 451 records · Page 25
All sourcesNASA NTRSDOE OSTI
NASA NTRS2016

The Habitable Exoplanet (HabEx) imaging mission concept: preliminary science drivers and technical requirements

HabEx is one of 4 possible NASA flagship mission concepts studied for a possible launch in the 2030s. It will be optimized for direct imaging and spectroscopy of habitable exoplanets, and will also enable a wide range of general astrophysics observations. HabEx shall characterize full planetary systems around nearby solar-type stars for the first time, including rocky planets, possible water worlds, gas giants, ice giants, and faint circumstellar debris disks. It will in particular explore our nearest neighbor planetary systems and search for signs of habitability and bio-signatures in the atmospheres of rocky planets. Such high spatial resolution high contrast observations require a large (~3.5 to 8m) stable diffraction- limited optical space telescope, which also opens new unique capabilities for studying the formation and evolution of stars and galaxies. We present here some preliminary science objectives identified for HabEx by our Science and Technology Definition Team (STDT), together with a first look at the key challenges and design trades ahead.

Mennesson, Bertrand↗
NASA NTRS2022

ORCAS - Keck Instrument Development - ORKID

A new breed of space-ground hybrid observatory, the Orbiting Configurable Artificial Star (ORCAS) mission is working with the W. M. Keck Observatory (WMKO) to demonstrate the viability of diffraction-limited visible imaging from large ground telescopes. To support that, we have built and delivered ORKID (The ORCAS Keck Instrument Demonstrator) as an early visible-wavelength performance demonstration with the Keck II Adaptive Optics (AO) system. By enabling AO and flux calibration observations, the low-cost ORCAS/ORKID mission will deliver highly detailed images to support many scientific advances. A community driven observation plan will provide Great Observatory quality capabilities open to all US observers. These observations will result in unique science for the mission, while also complementing and extending space-borne science.

Eliad Peretz↗
NASA NTRS2022

Phasing the Webb Telescope

The James Webb Space Telescope (JWST) is a segmented deployable telescope, currently operating at L2. The telescope utilizes 6 degrees of freedom for adjustment of the Secondary Mirror (SM) and 7 degrees of freedom for adjustment of each of its 18 segments in the Primary Mirror (PM). After deployment, the PM segments and the SM arrived in their correct optical positions to within a ~1 mm, with accordingly large wavefront errors. A Wavefront Sensing and Controls (WFSC) process was executed to adjust each of these optical elements in order to correct the deployment errors and produce diffraction-limited images across the entire science field. This paper summarizes the application of the WFSC process.

JWST↗
NASA NTRSDate not supplied

In-Space Modular Assembly: An Approach for Reliable, Affordable, Precision Space Apertures

In-space assembly will revolutionize the creation, upgrade, and evolution of future space systems. In-space assembly represents an alternative deployment strategy that is not constrained by the requirement of using a single launch vehicle and enables a greater freedom of design for the initial emplacement of assets and their evolution over time. In-space assembly enables assets, such as observatories and science platforms, to become persistent, evolving over time like their terrestrial counterparts. Also, in-space assembly provides a direct path for utilization of in-space manufactured components designed exclusively for the operational environment. To highlight the advantages of an in-space assembly approach, the modular assembly of a 3 m to 4 m precision optical aperture based on thin meniscus technology coupled with structurally efficient TriTruss modules is presented. The 3 m to 4 m aperture stows compactly within two standard ride share slots (0.61 m by 0.71 m by 0.97 m). Placing instruments and the robotic system used for assembly in an adjacent ride share slot enables a capable observatory to be placed into service via modest ride share opportunities. Further, recent hardware assembly tests of similar modules and progress toward hardware tests to validate the overall architecture via diffraction limited testing will be summarized.

Design↗
NASA NTRS2023

2023 Astrophotonics Roadmap: Pathways to Realizing Multi-Functional Integrated Astrophotonic Instruments

Photonic technologies offer numerous functionalities that can be used to realize astrophotonic instruments. The most spectacular example to date is the ESO Gravity instrument at the Very Large Telescope in Chile that combines the light-gathering power of four 8 m telescopes through a complex photonic interferometer. Fully integrated astrophotonic devices stand to offer critical advantages for instrument development, including extreme miniaturization when operating at the diffraction-limit, as well as integration, superior thermal and mechanical stabilization owing to the small footprint, and high replicability offering significant cost savings. Numerous astrophotonic technologies have been developed to address shortcomings of conventional instruments to date, including for example the development of photonic lanterns to convert from multimode inputs to single mode outputs, complex aperiodic fiber Bragg gratings to filter OH emission from the atmosphere, complex beam combiners to enable long baseline interferometry with for example, ESO Gravity, and laser frequency combs for high precision spectral calibration of spectrometers. Despite these successes, the facility implementation of photonic solutions in astronomical instrumentation is currently limited because of (1) low throughputs from coupling to fibers, coupling fibers to chips, propagation and bend losses, device losses, etc, (2) difficulties with scaling to large channel count devices needed for large bandwidths and high resolutions, and (3) efficient integration of photonics with detectors, to name a few. In this roadmap, we identify 24 key areas that need further development. We outline the challenges and advances needed across those areas covering design tools, simulation capabilities, fabrication processes, the need for entirely new components, integration and hybridization and the characterization of devices. To realize these advances the astrophotonics community will have to work cooperatively with industrial partners who have more advanced manufacturing capabilities. With the advances described herein, multi-functional integrated instruments will be realized leading to novel observing capabilities for both ground and space based platforms, enabling new scientific studies and discoveries.

astrophotonics↗
NASA NTRSDate not supplied

In-Space Modular Assembly: An Approach for Reliable, Affordable, Precision Space Apertures

In-space assembly will revolutionize the creation, upgrade, and evolution of future space systems. In-space assembly represents an alternative deployment strategy that is not constrained by the requirement of using a single launch vehicle and enables a greater freedom of design for the initial emplacement of assets and their evolution over time. In-space assembly enables assets, such as observatories and science platforms, to become persistent, evolving over time like their terrestrial counterparts. Also, in-space assembly provides a direct path for utilization of in-space manufactured components designed exclusively for the operational environment. To highlight the advantages of an in-space assembly approach, the modular assembly of a 3 m to 4 m precision optical aperture based on thin meniscus technology coupled with structurally efficient TriTruss modules is presented. The 3 m to 4 m aperture stows compactly within two standard ride share slots (0.61 m by 0.71 m by 0.97 m). Placing instruments and the robotic system used for assembly in an adjacent ride share slot enables a capable observatory to be placed into service via modest ride share opportunities. Further, recent hardware assembly tests of similar modules and progress toward hardware tests to validate the overall architecture via diffraction limited testing will be summarized.

Design↗
NASA NTRS2006

Electromagnetic Properties of Filled, Pixellated Arrays

Filled arrays of bolometers are currently being employed for use in astronomy from the far-infrared through millimeter parts of the electromagnetic spectrum. Because of the large range of wavelengths for which this is applicable, the number of modes supported by a bolometric pixel will vary according to specific application. Withington et al. (2003) have built a formalism for treating the electromagnetic properties of such bolometers by propagating the second order statistical properties of the radiation through a canonical optical system. In this work, we use this formalism to construct beam pattern images of square pixels for various ratios of p/lambda where p is the pixel size and lambda is the wavelength. In the low mode limit, the diffraction effects cause the beam pattern to be circular with a quadrupole dependence of Stokes Q and U. High mode cases approach the geometric limit. The polarization in these cases can be seen to trace the pixel edges. The effective size of the beam has a direct impact on the inter-pixel coupling and sets the number of independent detectors in an astronomical focal plane. This technique illustrates and quantifies the relationship between pixel size and angular resolution limits for a given wavelength and telescope. This is especially true in the limit of low p/lambda. In this case, the diffraction due to pixelization is non-negligible for the calculation of the overall angular resolution of the telescope. In addition, for instruments that are polarization sensitive, this method also provides a quantitative method for determining the contribution of the instrument to the measured polarization.

Chuss, David T.↗
NASA NTRS2002

Diffraction hardware testbed and model validation

Optical systems, which operate over a wide range of Fresnel numbers, are often times performance-limited by diffraction effects. In order to characterize such effects at the 40-100 picometer level, a diffraction testbed has been built which has the capability of measuring diffraction effects at this level. Concurrently, mathematical diffraction modeling tools have been developed that propagate an input wavefront through an optical train, while retaining amplitude and phase information at a grid resolution sufficient for yielding picometer-resolution diffraction test data. This paper contains a description of this diffraction hardware testbed, the diffraction modeling approach, and a comparison of the modeled and hardware test results, which then serves as validation of the diffraction modeling methodology.

optical↗
NASA NTRS1998

Comparative Analysis of Thaumatin Crystals Grown on Earth and in Microgravity

The protein thaumatin was studied as a model macromolecule for crystallization in microgravity environment experiments conducted on two U.S. Space Shuttle missions (second United States Microgravity Laboratory (USML-2) and Life and Microgravity Spacelab (LMS)). In this investigation we evaluated and compared the quality of space- and Earth-grown thaumatin crystals using x-ray diffraction analysis and characterized them according to crystal size, diffraction resolution limit, and mosaicity. Two different approaches for growing thaumatin crystals in the microgravity environment, dialysis and liquid-liquid diffusion, were employed as a joint experiment by our two investigative teams. Thaumatin crystals grown under a microgravity environment were generally larger in volume with fewer total crystals. They diffracted to significantly higher resolution and with improved diffraction properties as judged by relative Wilson plots. The mosaicity for space-grown crystals was significantly less than for those grown on Earth. Increasing concentrations of protein in the crystallization chambers under microgravity lead to larger crystals. The data presented here lend further support to the idea that protein crystals of improved quality can be obtained in a microgravity environment.

Ng, Joseph D.↗
NASA NTRS1997

Protein Crystal Movements and Fluid Flows During Microgravity Growth

The growth of protein crystals suitable for X-ray crystal structure analysis is an important topic. The methods of protein crystal growth are under increasing study whereby different methods are being compared via diagnostic monitoring including Charge Coupled Device (CCD) video and interferometry. The quality (perfection) of protein crystals is now being evaluated by mosaicity analysis (rocking curves) and X-ray topographic images as well as the diffraction resolution limit and overall data quality. Choice of a liquid-liquid linear crystal growth geometry and microgravity can yield a spatial stability of growing crystals and fluid, as seen in protein crystallization experiments on the unmanned platform EURICA. A review is given here of existing results and experience over several microgravity missions. The results include CCD video as well as interferometry during the mission, followed, on return to earth, by rocking curve experiments and full X-ray data collection on LMS and earth control lysozyme crystals. Diffraction data recorded from LMS and ground control apocrustacyanin C(sub 1) crystals are also described.

Boggon, Titus J.↗
NASA NTRS1998

Protein Crystal Movements and Fluid Flows During Microgravity Growth

The growth of protein crystals suitable for x-ray crystal structure analysis is an important topic. The quality (perfection) of protein crystals is now being evaluated by mosaicity analysis (rocking curves) and x-ray topographic images as well as the diffraction resolution limit and overall data quality. In yet another study, use of hanging drop vapour diffusion geometry on the IML-2 shuttle mission showed, again via CCD video monitoring, growing apocrustacyanin C(sub 1) protein crystal executing near cyclic movement, reminiscent of Marangoni convection flow of fluid, the crystals serving as "markers" of the fluid flow. A review is given here of existing results and experience over several microgravity missions. Some comment is given on gel protein crystal growth in attempts to 'mimic' the benefits of microgravity on Earth. Finally, the recent new results from our experiments on the shuttle mission LMS are described. These results include CCD video as well as interferometry during the mission, followed, on return to Earth, by reciprocal space mapping at the NSLS, Brookhaven, and full X-ray data collection on LMS and Earth control lysozyme crystals. Diffraction data recorded from LMS and ground control apocrustacyanin C(sub 1) crystals are also described.

Boggon, Titus J.↗
NASA NTRS1997

A Critical Assessment of Protein Crystal Growth in Microgravity

Experiments to grow higher diffraction quality protein crystals in the microgravity environment of an orbiting spacecraft are one of the most frequently flown space experiments. Ground-based research has shown that convective flows occur even about protein crystals growing in the Earth's gravitational field. Further, this research has shown that the resultant flow velocities can cause growth cessation, and probably affect the measured X-ray data quality obtained. How flow deleteriously affects protein crystal growth (PCG) is still not known, and is the subject of ongoing research. Failing a rational method for ameliorating flow effects on Earth, one can, through NASA and other nations space agency sponsored programs, carry out protein crystal growth in the microgravity environment of an orbiting spacecraft. Early first generation PCG hardware was characterized by a very low success rate and a steep design learning curve. Subsequent hardware designs have improved upon their predecessors. Now the crystal grower has a wide variety of hardware configurations and crystal growth protocols to choose from, many of which implement "standard" laboratory protein crystal growth methods. While many of these are first or early second generation hardware the success rate, defined as growing crystals giving data better than has been obtained on Earth, is at least 20% overall and may be considerably higher if one only considers latter experiments. There are a large number of protein crystals grown every year, with hundreds of structures determined. Those crystallized in microgravity represent a small proportion of this total, and there is concern that the costs of the microgravity PCG program(s) do not justify such limited returns. Empirical evidence suggests that optimum crystal growth conditions in microgravity differ from those determined on Earth, further exacerbating the chances of success. Microgravity PCG is probably best suited for "mature" crystallizations, where one has considerable experience with the particular macromolecular system and has reached an apparent limit in diffraction resolution. Under such circumstances the cost of one or two successful flight experiments may more than offset the equivalent cost of several years effort to obtain the same improvement in data quality.

Pusey, Marc↗
NASA NTRS1973

A technique for designing active control systems for astronomical telescope mirrors

This paper considers the problem of designing a control system to achieve and maintain the required surface accuracy of the primary mirror of a large space telescope. Control over the mirror surface is obtained through the application of a corrective force distribution by actuators located on the rear surface of the mirror. The design procedure is an extension of a model control technique developed for distributed parameter plants with known eigenfunctions to include plants whose eigenfunctions must be approximated by numerical techniques. Instructions are given for constructing the mathematical model of the system, and a design procedure is developed for use with. typical numerical data in selecting the number and location of the actuators. Examples of actuator patterns and their effect on various errors are given.

Active optics↗
NASA NTRS1994

Imaging Domains In Magnetic Garnets By Use Of TSMFM

Tunneling-stabilized magnetic-force microscopy (TSMFM) demonstrated to yield images of magnetic domains in low-coercivity magnetic garnets with perpendicular anisotropy. Ability to generate images of domain walls and minute vertical Bloch lines aids study of vertical-Bloch-line magnetic memory devices that contain garnets. TSMFM provides desired resolution because its resolution not limited by diffraction.

Katti, Romney R.↗