Design of double-bend and multibend achromat lattices with large dynamic aperture and approximate invariants
Not Available
36 MATERIALS SCIENCE↗
SEARCH · Search NASA
Results for “large aperture optics”
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.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Perception for a large deployable reflector telescope
Optical science and technology concepts for a large deployable reflector for far-infrared and submillimeter astronomy from above the earth's atmosphere are discussed. Requirements given at the Asilomar Conference are reviewed. The technical challenges of this large-aperture (about 20-meter) telescope, which will be diffraction limited in the infrared, are highlighted in a brief discussion of one particular configuration.
Breckinridge, J. M.↗
Zone plate lens antennas for millimeter and submillimeter wavelengths
Zone plate lenses are a type of focusing element which function essentially as differential phase shifters, having a relatively few, coarsely quantized phase delays across the incident beam of radiation. The major advantages are ease of fabrication and much reduced thickness, compared to conventional refractive focusing elements. These considerations are both of particular importance for the submillimeter range, in which manufacturing tolerances for curved optical elements can pose significant problems, and where the absorption of readily available dielectric materials is quite large. In this presentation we briefly review the theory of zone plate lens operations, present a relatively simple method for calculating the aperture efficiency of zone plate lenses used as antennas, and show some theoretical and measured results in the 100 GHz range.
Goldsmith, Paul F.↗
The pursuit of heavy elements in the HgMn-type star Chi Lupi: Observations with the GHRS in the COSTAR era
Observations of the ultra-sharp-lined HgMn star Chi Lupi made with the Goddard High Resolution Spectrograph (GHRS) after the Hubble Space Telescope (HST) First Servicing Mission display the effect of the Corrective Optics Space Telescope Axial Replacement instrument (COSTAR) upon the spectral resolution of several observing modes. The resolution is restored to levels expected in the absence of the telescope spherical aberration for all observations made through the GHRS Large Science Aperture (LSA). The Small Science Aperture (SSA) spectra are nearly identical in resolution to the pre-COSTAR values while benefiting from higher throughput. The line spread function for the LSA relative to the SSA shows little wavelength dependence and reflects a Gaussian profile approximately 20%-30% broader than for SSA spectra. Absorption features containing components of As II and Bi II represent upper limit enhancements of 2.9 and 2.1 dex for As II and Bi II, respectively, relative to meteoritic abundance determinations.
Wahlgren, Glenn M.↗
Coronagraph Design Optimization for Segmented Aperture Telescopes
The goal of directly imaging Earth-like planets in the habitable zone of other stars has motivated the design of coronagraphs for use with large segmented aperture space telescopes. In order to achieve an optimal trade-o between planet light throughput and di racted starlight suppression, we consider coronagraphs comprised of a stage of phase control implemented with deformable mirrors (or other optical elements), pupil plane apodization masks (gray scale or complex valued), and focal plane masks (either amplitude only or complex-valued, including phase only such as the vector vortex coronagraph). The optimization of these optical elements, with the goal of achieving 10 or more orders of magnitude in the suppression of on-axis (starlight) di racted light, represents a challenging non-convex optimization problem with a nonlinear dependence on control degrees of freedom. We develop a new algorithmic approach to the design optimization problem, which we call the "Auxiliary Field Optimization" (AFO) algorithm. The central idea of the algorithm is to embed the original optimization problem, for either phase or amplitude (apodization) in various planes of the coronagraph, into a problem containing additional degrees of freedom, speci cally ctitious "auxiliary" electric elds which serve as targets to inform the variation of our phase or amplitude parameters leading to good feasible designs. We present the algorithm, discuss details of its numerical implementation, and prove convergence to local minima of the objective function (here taken to be the intensity of the on-axis source in a "dark hole" region in the science focal plane). Finally, we present results showing application of the algorithm to both unobscured o -axis and obscured on-axis segmented telescope aperture designs. The application of the AFO algorithm to the coronagraph design problem has produced solutions which are capable of directly imaging planets in the habitable zone, provided end-to-end telescope system stability requirements can be met. Ongoing work includes advances of the AFO algorithm reported here to design in additional robustness to a resolved star, and other phase or amplitude aberrations to be encountered in a real segmented aperture space telescope.
Redding, Dave↗
Statistical Analysis of Fading Power Vectors for Real-Time Atmospheric Channel Emulation
The design and testing of a free-space optical communication system requires assessment of the impact of random fluctuations in received power from a laser beam transmitted over an atmospheric channel. A number of methods for generating fading power vectors for in-lab emulation of an atmospheric channel have previously been reported. These techniques include spectral shaping and filtering of a signal from a normally distributed pseudo-random number generator, full wave optics simulations with random phase screens, and pre-recorded measurements from experimental free-space links. In this work, a statistical analysis of atmospheric fading is presented with the goal of producing a practical engineering model for the fading channel suitable for generating synthetic fade vectors in real-time for long-duration receiver testing with channel interleaving. Specifically, a parametric model is developed for turbulence-induced fade on space-to-ground links with large-aperture receivers, including aperture-averaging and the effects of aperture size on the instantaneous coupling efficiency for mode- limited receivers. In particular, we analyze the probability density function and temporal power spectrum for fluctuations of the coupling efficiency for few-mode fibers in a range of turbulence conditions.
free-space optical communication↗
Statistical Analysis of Fading Power Vectors for Real-Time Atmospheric Channel Emulation
The design and testing of a free-space optical communication system requires assessment of the impact of random fluctuations in received power from a laser beam transmitted over an atmospheric channel. A number of methods for generating fading power vectors for in-lab emulation of an atmospheric channel have previously been reported. These techniques include spectral shaping and filtering of a signal from a normally distributed pseudo-random number generator, full wave optics simulations with random phase screens, and pre-recorded measurements from experimental free-space links. In this work, a statistical analysis of atmospheric fading is presented with the goal of producing a practical engineering model for the fading channel suitable for generating synthetic fade vectors in real-time for long-duration receiver testing with channel interleaving. Specifically, a parametric model is developed for turbulence-induced fade on space-to-ground links with large-aperture receivers, including aperture-averaging and the effects of aperture size on the instantaneous coupling efficiency for mode-limited receivers. In particular, we analyze the probability density function and temporal power spectrum for fluctuations of the coupling efficiency for few-mode fibers in a range of turbulence conditions.
free-space optical communication↗
A transmitted-beam diagnostic for the wavelength-tunable UV drive beam on OMEGA
A transmitted-beam diagnostic (P9TBD) was developed as part of a new experimental platform used to study laser–plasma interactions on OMEGA. Located in the opposing port to the wavelength-tunable (350 nm to 353 nm) UV drive beam, the P9TBD characterizes the beam after it propagates through an undersense plasma. The instrument consists of a large-aperture window that allows light to exit the target chamber and project onto a thin sheet of semi-transparent diffuser material. Light transmitted through the diffuser is recorded using a time-integrated camera and a fiber-optically coupled streaked spectrometer, providing measurements of the energy, power, fluence, polarization, and spectrum of the transmitted beam. Here, the diagnostic enables direct observation of a variety of cross-beam energy transfer phenomena, such as wavelength detuning, polarization effects, and gain saturation.
47 OTHER INSTRUMENTATION↗
Far UV camera/spectrograph
In March 1610, Galileo Galilei reported the first use of a telescope to view mountains and maria on the Moon. On April 21, 1972, the Apollo 16 commander pointed a somewhat more complex optical instrument at the Earth from the Moon and obtained several remarkable photographs showing atmospheric rather than surface features. The optical part of the far UV camera (aperture, 7.5 cm) was not much larger than Galileo's telescope. Like his, this instrument was also pointed at other celestial objects that Galileo viewed, including the Milky Way and Jupiter, and the Large Magellanic Cloud (LMC), which is not visible from Italy. More important, the far UV camera/spectrograph recorded light in the invisible band of wavelengths between 50 and 160 nm, approximately one-third the wavelength that can penetrate the atmosphere of the Earth to ground-based telescopes. As described in more detail in this section, these UV observations from the Moon allow study of the entire atmosphere of the Earth and the geocorona. The photographs show hydrogen and other gases in the solar wind and interplanetary media, and they provide new data on stars, nebulae, and galaxies much farther away. When used as a spectrograph, the instrument distributes the light it receives according to wavelength, and the resulting spectrum shows bright lines or gaps known to be characteristic of various gases, such as hydrogen (H), helium (He), oxygen (O), nitrogen (N), and neon (Ne). If a gas cloud is hot, the atoms are excited and the spectrum shows bright emission lines; if it is cool, the atoms absorb light, leaving gaps or absorption lines. The far UV camera is blind to ordinary visible light; for that reason, the photographs show very few of the stars mapped by ground-based telescopes. Only the very-high-temperature (blue) stars of spectral classes O, B, and possibly A (temperatures from 50000 ° down to 10000°K) are expected to be recorded. Image blackness or density on the negatives also depends on the brightness of the star, which astronomers measure in an inverted logarithmic scale of magnitudes. A star of 6 magnitudes (mag.) can barely be seen with the unaided eye. An 11-mag. star is 100 times fainter, and a 12-mag. star is 2.5 times fainter yet. The faintest star recorded by the far UV camera is at least 11 mag., which is called the limiting magnitude.
George R. Carruthers↗
System architecture of MMIC-based large aperture arrays for space application
The persistent trend to use millimeter-wave frequencies for satellite communications presents the challenge to design large-aperture phased arrays for space applications. These arrays, which comprise 100 to 10,000 elements, are now possible due to the advent of lightwave technology and the availability of monolithic microwave integrated circuits. In this paper, system aspects of optically controlled array design are studied. In particular, two architectures for a 40 GHz array are outlined, and the main system-related issues are examined: power budget, synchronization in frequency and phase, and stochastic effects.
Herczfeld, P. R.↗
System architecture of MMIC-based large aperture arrays for space applications
The persistent trend to use millimeter-wave frequencies for satellite communications presents the challenge to design large-aperture phased arrays for space applications. These arrays, which comprise 100 to 10,000 elements, are now possible due to the advent of lightwave technology and the availability of monolithic microwave integrated circuits. In this paper, system aspects of optically controlled array design are studied. In particular, two architectures for a 40 GHz array are outlined, and the main system-related issues are examined: power budget, synchronization in frequency and phase, and stochastic effects.
Herczfeld, P. R.↗
Direct UV observations of the circumstellar envelope of alpha Orionis
Observations were made in the IUE LWP camera, low dispersion mode, with alpha Ori being offset various distances from the center of the Long Wavelength Large Aperture along its major axis. Signal was acquired at all offset positions and is comprised of unequal components of background/dark counts, telescope-scattered light, and scattered light emanating from the extended circumstellar shell. The star is known from optical and infrared observations to possess an extended, arc-minute sized, shell of cool material. Attempts to observe this shell with the IUE are described, although the deconvolution of the stellar signal from the telescope scattered light requires further calibration effort.
Stencel, R. E.↗
Heat-Exchange Driven Aircraft for Low Altitude and Surface Exploration of Venus: Phase 1 Study Final Report
Exploration of Venus below its clouds has long been impaired by the planet’s massive CO2 atmosphere, corrosive trace gases, and high opacity. Except for a few narrow spectral windows, the 20 km thick global cloud cover blocks light over the entirety of the ultraviolet through thermal infrared spectrum, impeding orbital studies of the surface and lower portion of the atmosphere. In addition to the cloud opacity, Rayleigh scattering through 80 bars of CO 2 in the lower 40 km of the atmosphere results in a Rayleigh scattering depth between 25 and1 in the visible through near infrared portion of the spectrum. That optically thick scattering, combined with the uniform angular distribution of the illumination provided by the highly diffusing clouds overhead greatly reduces even very large surface albedo contrasts (Crisp, pers. Comm.). To date, the surface has only been mapped via synthetic aperture radar by the Magellan mission at scales of 120 to 300 m/pixel. In addition to contributing to the difficulty of performing studies of the surface from orbit, the extreme temperatures and pressures at the surface also create a challenging environment to utilize a lander for exploration. The longest-lived lander on Venus’ surface survived for 2 hours. Hence, limited access to observe the surface and lower atmosphere of Venus arguably puts the surface and lower atmosphere of Venus as one of the least explored regions of the inner Solar System.
NIAC Phase I↗
From Monolithics to Tethers to Freeflyers: The Spectrum of Large Aperture Sensing from Space
As part of NASA's endeavor to push the envelope and go where we have never been before, the Space Science Enterprise has laid out a vision which includes several missions that revolutionize the collection of scientific data from space. Many of the missions designed to meet the objectives of these programs depend heavily on the ability to perform space-based interferometry, which has recently become a rapidly growing field of investigation for both the scientific and engineering communities. While scientists are faced with the challenges of designing high fidelity optical systems capable of making detailed observations, engineers wrestle with the problem of providing s-pace-based platforms that can permit this data gathering to occur. Observational data gathering is desired at's variety of spectral wavelengths and resolutions, calling for interferometers with a range of baseline requirements. Approaches to configuration design are as varied as the missions themselves from large monolithic spacecraft to multiple free-flying small spacecraft and everything in between. As will be discussed, no one approach provides a 'panacea' of solutions rather each has its place in terms of the mission requirements. The purpose here is to identify the advantages and disadvantages of the various approaches, to discuss the driving factors in design selection and determine the relative range of applicability of each design approach.
Leitner, Jesse↗
Feed System Design Considerations for Large Space Antenna Systems. Part 2: Single Aperture with Overlapping Feeds
Contiguous multiple beams are used to make use of the set of frequency bands at different beams at different geographical locations and achieve the most efficient use of precious frequency allocation. This is feasible only if the interference among cochannel beams is below some acceptable level, by carrier/interference (C/I) ratio. Individual beam patterns of very low sidelobes, which in turn necessitates narrow feed are required. A physically realizable solution to this problem entails either more than one reflector, more complicated optics, or breaking of each feed into a cluster of smaller elements, some of which would then be shared by adjacent beams. The latter, however, requires a complicated beamforming network (BFN) for the proper feeding of the elements. The feedpacking problem is not unique to reflector antennas and exists in lens type antennas as well. The BFN and associated problems are present in the phased array antennas and on a much larger scale. Poor scan capabilities are associated with reflector systems. The scan properties of offset fed reflector systems can be improved by choosing a very large focal length to parent reflector diameter ((F/Dp) ratio, which requires a longer boom to support the feed. In the case of reflectors with cluster feed arrangements, the scan capability for smaller F/Dp ratios is improved by proper adjustment of cluster element excitations. Such a system seems to be appropriate for up to 10 beamwidths scan. For a larger number of beams, systems with wider scan capabilities, such as phased arrays or phased array/reflector combinations, become more appealing.
Jamnejad, V.↗
MOD-Amp System Design Spring: Spring 2026 – Georgetown University, SYSM–5620
High-energy lasers (HELs) play an important role in both national defense and scientific research. In defense applications, HELs are used for target detection, tracking, and engagement. In research environments, they support studies of extreme physical conditions relevant to fusion energy and plasma science. These systems depend on the amplification of light through stimulated emission of radiation, allowing optical energy to be increased to the levels required for operation. This amplification occurs when light passes through an energized gain medium that receives energy from an external optical or electrical source. To achieve the desired output, laser systems often use multiple amplification stages, including high-gain preamplifiers and lower-gain power or booster amplifiers. At Lawrence Livermore National Laboratory (LLNL) and other national laboratories, many large-aperture laser amplifier systems are aging and rely on system-specific hardware, obsolete technologies, and incomplete documentation. These legacy systems create challenges for maintenance, supportability, and long-term operation. Their lack of standardization also increases the difficulty of sustaining reliable performance over time. As this infrastructure continues to age, the likelihood of unplanned downtime grows, which can negatively affect both national security missions and scientific research programs that depend on dependable HEL capabilities. The purpose of this document is to demonstrate the application of systems engineering fundamentals and design thinking through the development of a laser amplifier case study. The proposed system concept is intended as an academic exercise and not as a finalized engineering design. As a result, the development presented in this document is incomplete and may contain technical assumptions or errors that would require further investigation before any real-world implementation.
42 ENGINEERING↗
Evaluation of the thin deformable active optics mirror concept
The active optics concept using a thin deformable mirror has been successfully demonstrated using a 30 in. diameter, 1/2 in. thick mirror and a 61 point matrix of forces for alignment. Many of the problems associated with the design, fabrication, and launch of large aperture diffraction-limited astronomical telescopes have been resolved and experimental data created that can provide accurate predictions of performance in orbit.
Robertson, H. J.↗
Synthesis of offset dual shaped subreflector antennas for control of Cassegrain aperture distributions
The method presented for antenna upgrading involves a redesign of only the subreflector portion of a Cassegrain antenna or the introduction of a subreflector feed system for a paraboloid. A pair of offset subreflectors are synthesized which will produce a controllable high gain amplitude distribution in the aperture of the large paraboloid. The synthesis method is based on the approximate formulation for an offset dual shaped high gain antenna first presented by Galindo-Israel and Mittra (1977). It is pointed out that in their approximate formulation, the geometrical optics energy was scattered from a subreflector and then from a second large reflector, which reflected a uniform phase distribution. In the offset dual shaped subreflector (DSS) antenna proposed here, the second reflection is from a smaller (sub) reflector, and it scatters a spherical wave that feeds a hyperboloid or feeds a large paraboloid directly. The DSS synthesis is tested on the 210-ft-diameter Cassegrain antenna at Goldstone, California.
Galindo-Israel, V.↗