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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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Radiometric accuracy of the Diffuse Infrared Background Experiment (DIRBE)

The Diffuse Infrared Background Experiment (DIRBE) is a cryogenically-cooled 10-band photometer with a large field-of-view (0.886 x 0.886 sq deg) which scans by rotation of the Cosmic Background Explorer about a spin axis. In-orbit calibration requires that the DIRBE detect and measure with precision the signatures of compact sources as they transit the field-of-view. Analysis of the conceptual optical design revealed that response of the 10 bands would vary significantly as a function of source position in the field-of-view, caused by anamorphic pupil distortion and field separation. The optical design reported in this paper is the result of changes which greatly improve the response uniformity and radiometric accuracy of the DIRBE.

Howell, B. J.↗
NASA NTRS1973

A Method of Monitoring Non-Resonant Raman Lidar Returns During Daylight Hours

A method for using non-resonant Raman lidar during daytime hours is presented. A dual (or quadruple) arrangement of electro-optical channels is set up in the lidar receiver. Each channel contains its own optical spectral response as determined by an appropriate set of interference filters. The incoming signal is split and fed into two channels, filtered (simultaneously) and then inserted into the input terminals of an operational amplifier. The difference signal is selected and amplified whereas the common portion of the signal is highly attenuated (Common Mode Re.jection Ratio = 75-80db). For the present hardware, daylight intensities 10(exp 2)-10(exp 3) times Raman signals are received simultaneously. Mean values of intensities of daylight signals which give rise to a constant differences merely shift the value of the measured variable at the ground. These mean value signals have their common part highly attenuated. The differences of the fluctuation portions of the daylight signal represents a noise signal. Identical (space-time) optical paths for each component of the daylight signal produce the same fluctuational spectra in each channel. Hence noise levels, much less than signal levels, are anticipated. First a N2-H2 ) signal pair is differenced. Then an N2-O2 pair is differenced and used for instrumental normalization purposes. Signal levels to be encountered are quite well known as a result of prior field work. Improved optical design of laser system can reduce mean value of daylight intensities by 10(exp 2). Thus the mean daylight intensity can be set equal to the expected signal levels by more advanced optical design. Performance characteristics of photomultiplier pairs are discussed in this connection.

Cooney, John↗
NASA NTRS1990

Reluctant glass formers and their applications in optical lens design

Over ten years ago, it was shown that glasses with high index of refraction and some with low dispersion could be produced from a number of pure refractory oxides, including the lanthanides, by containerless processing. By containerless processing it is possible to minimize surface heterogeneous nucleation and produce larger glass samples of the materials than by other methods. The use of proposed high temperature containerless processing facilities in space permits the fabrication of benchmark samples of new unique glass compositions for optical property determination as well as for glass formation. It was shown that glasses with high refractive indices and large Abbe numbers can be formulated using this technology. These glasses lie in the classical forbidden region of the glass map. Preliminary study of the impact of having such unusual glasses available for the lens designer was made. Results indicate that significant improvements can be realized over the use of only conventional glasses. A cursory survey of a number of nationally recognized lens designers indicated a general agreement that such glasses would be highly desired and could be expected to lead to completely new designs as well as simplifying existing designs.

Ethridge, Edwin C.↗
NASA NTRS2015

Design Evolution of the Wide Field Infrared Survey Telescope using Astrophysics Focused Telescope Assets (WFIRST-AFTA) and Lessons Learned

The design of the Wide Field Infrared Survey Telescope using Astrophysics Focused Telescope Assets (WFIRST-AFTA) continues to evolve as each design cycle is analyzed. In 2012, two Hubble sized (2.4 m diameter) telescopes were donated to NASA from elsewhere in the Federal Government. NASA began investigating potential uses for these telescopes and identified WFIRST as a mission to benefit from these assets. With an updated, deeper, and sharper field of view than previous design iterations with a smaller telescope, the optical designs of the WFIRST instruments were updated and the mechanical and thermal designs evolved around the new optical layout. Beginning with Design Cycle 3, significant analysis efforts yielded a design and model that could be evaluated for Structural-Thermal-Optical-Performance (STOP) purposes for the Wide Field Imager (WFI) and provided the basis for evaluating the high level observatory requirements. Development of the Cycle 3 thermal model provided some valuable analysis lessons learned and established best practices for future design cycles. However, the Cycle 3 design did include some major liens and evolving requirements which were addressed in the Cycle 4 Design. Some of the design changes are driven by requirements changes, while others are optimizations or solutions to liens from previous cycles. Again in Cycle 4, STOP analysis was performed and further insights into the overall design were gained leading to the Cycle 5 design effort currently underway. This paper seeks to capture the thermal design evolution, with focus on major design drivers, key decisions and their rationale, and lessons learned as the design evolved.

Thermal Design↗
NASA NTRS2015

Design Evolution of the Wide Field Infrared Survey Telescope Using Astrophysics Focused Telescope Assets (WFIRST-AFTA) and Lessons Learned

The design of the Wide Field Infrared Survey Telescope using Astrophysics Focused Telescope Assets (WFIRST-AFTA) continues to evolve as each design cycle is analyzed. In 2012, two Hubble sized (2.4 m diameter) telescopes were donated to NASA from elsewhere in the Federal Government. NASA began investigating potential uses for these telescopes and identified WFIRST as a mission to benefit from these assets. With an updated, deeper, and sharper field of view than previous design iterations with a smaller telescope, the optical designs of the WFIRST instruments were updated and the mechanical and thermal designs evolved around the new optical layout. Beginning with Design Cycle 3, significant analysis efforts yielded a design and model that could be evaluated for Structural-Thermal-Optical-Performance (STOP) purposes for the Wide Field Imager (WFI) and provided the basis for evaluating the high level observatory requirements. Development of the Cycle 3 thermal model provided some valuable analysis lessons learned and established best practices for future design cycles. However, the Cycle 3 design did include some major liens and evolving requirements which were addressed in the Cycle 4 Design. Some of the design changes are driven by requirements changes, while others are optimizations or solutions to liens from previous cycles. Again in Cycle 4, STOP analysis was performed and further insights into the overall design were gained leading to the Cycle 5 design effort currently underway. This paper seeks to capture the thermal design evolution, with focus on major design drivers, key decisions and their rationale, and lessons learned as the design evolved.

WFIRST↗
NASA NTRS2015

Requirements and Design Reference Mission for the WFIRST-AFTA Coronagraph Instrument

The WFIRST-AFTA coronagraph instrument take s advantage of AFTA s 2.4 -meter aperture to provide novel exoplanet imaging science at approximately the same instrument cost as an Explorer mission. The AFTA coronagraph also matures direct imaging technologies to high TRL for an Exo-Earth Imager in the next decade. The coronagraph Design Reference Mission (DRM) optical design is based on the highly successful High Contrast Imaging Testbed (HCIT), with modifications to accommodate the AFTA telescope design, service-ability, volume constraints, and the addition of an Integral Field Spectrograph (IFS). In order to optimally satisfy the three science objectives of planet imaging, planet spectral characterization and dust debris imaging, the coronagraph is designed to operate in two different modes : Hybrid Lyot Coronagraph or Shaped Pupil Coronagraph. Active mechanisms change pupil masks, focal plane masks, yot masks, and bandpass filters to shift between modes. A single optical beam train can thus operate alternatively as two different coronagraph architecture s. Structural Thermal Optical Performance (STOP) analysis predict s the instrument contrast with the Low Order Wave Front Control loop closed. The STOP analysis was also used to verify that the optical/structural/thermal design provides the extreme stability required for planet characterization in the presence of thermal disturbances expected in a typical observing scenario. This paper describes the instrument design and the flow down from science requirements to high level engineering requirements.

contrast↗
NASA NTRSDate not supplied

Prism Assembly for Roman Space Telescope Wide Field Instrument Slit-less Spectroscopy

The Roman Space Telescope (RST) is a three mirror anastigmat design with a 2.4 m primary mirror. RST will be based in L2 orbit, from where it will provide science information on exoplanets and dark energy using the Coronagraph Instrument (CGI) and Wide Field Instrument (WFI). The WFI features a 300 megapixel near-infrared detector array which provides a field of view 100 times larger than that of Hubble Space Telescope. The Prism Assembly is a small add-on instrument to the Roman Space Telescope’s Wide Field Instrument (WFI), installed in a slot in WFI’s element wheel. The Prism assembly has a passband from 0.75 µm to 1.8 µm, enabling a survey of redshifts in the range 0.2 to 1.7 µm. It provides low resolution slit-less spectroscopy with a spectral resolution R > 70 for all wavelengths, and R < 170 for λ > 0.8 µm across the full field. The Prism Assembly has the potential to provide more supernova spectra than ground-based spectroscopy during the mission lifetime. Being a late add-on to the RST mission, the Prism Assembly has had restrictions on size, weight and geometry, and a challenging schedule, which has dictated much of the implementation. Despite these challenges, the Prism Assembly is a pocket-sized high-performance spectrographic element, implemented as a refractive, all-spherical optical design using only two elements, one S-TIH-1 glass and one CaF2. This presentation will give an overview of the Prism Assembly, from design and implementation, through alignment, test and calibration. (100 words): The Roman Space Telescope is a three mirror anastigmat design with a 2.4 m primary mirror, which will provide science information on dark energy and exoplanets. The Prism Assembly is a small add-on instrument to the telescope’s Wide Field Instrument, enabling low resolution slit-less spectroscopy with a spectral resolution 70 < R < 170 across the full field from λ= 0.75 µm to 1.8 µm. The Prism Assembly is a refractive, all-spherical optical design using a glass and a CaF2 element. This presentation will give an overview of the Prism Assembly, from design and implementation, through alignment, test and calibration.

Space Instrumentation↗
NASA NTRS1984

Image-plane processing of visual information

Shannon's theory of information is used to optimize the optical design of sensor-array imaging systems which use neighborhood image-plane signal processing for enhancing edges and compressing dynamic range during image formation. The resultant edge-enhancement, or band-pass-filter, response is found to be very similar to that of human vision. Comparisons of traits in human vision with results from information theory suggest that: (1) Image-plane processing, like preprocessing in human vision, can improve visual information acquisition for pattern recognition when resolving power, sensitivity, and dynamic range are constrained. Improvements include reduced sensitivity to changes in lighter levels, reduced signal dynamic range, reduced data transmission and processing, and reduced aliasing and photosensor noise degradation. (2) Information content can be an appropriate figure of merit for optimizing the optical design of imaging systems when visual information is acquired for pattern recognition. The design trade-offs involve spatial response, sensitivity, and sampling interval.

Huck, F. O.↗
NASA NTRS2008

Instrument Performance of GISMO, a 2 Millimeter TES Bolometer Camera used at the IRAM 30 m Telescope

In November of 2007 we demonstrated a monolithic Backshort-Under-Grid (BUG) 8x16 array in the field using our 2 mm wavelength imager GISMO (Goddard IRAM Superconducting 2 Millimeter Observer) at the IRAM 30 m telescope in Spain for astronomical observations. The 2 mm spectral range provides a unique terrestrial window enabling ground-based observations of the earliest active dusty galaxies in the universe and thereby allowing a better constraint on the star formation rate in these objects. The optical design incorporates a 100 mm diameter silicon lens cooled to 4 K, which provides the required fast beam yielding 0.9 lambda/D pixels. With this spatial sampling, GISMO will be very efficient at detecting sources serendipitously in large sky surveys, while the capability for diffraction limited imaging is preserved. The camera provides significantly greater detection sensitivity and mapping speed at this wavelength than has previously been possible. The instrument will fill in the spectral energy distribution of high redshift galaxies at the Rayleigh-Jeans part of the dust emission spectrum, even at the highest redshifts. Here1 will we present early results from our observing run with the first fielded BUG bolometer array. We have developed key technologies to enable highly versatile, kilopixel, infrared through millimeter wavelength bolometer arrays. The Backshort-Under-Grid (BUG) array consists of three components: 1) a transition-edge-sensor (TES) based bolometer array with background-limited sensitivity and high filling factor, 2) a quarter-wave reflective backshort grid providing high optical efficiency, and 3) a superconducting bump-bonded large format Superconducting Quantum Interference Device (SQUID) multiplexer readout. The array is described in more detail elsewhere (Allen et al., this conference). In November of 2007 we demonstrated a monolithic 8x 16 array with 2 mm-pitch detectors in the field using our 2 mm wavelength imager GISMO (Goddard IRAM Superconducting 2 Millimeter Observer) at the IRAM 30 m telescope in Spain for astronomical observations. The 2 mm spectral range provides a unique terrestrial window enabling ground-based observations of the earliest active dusty galaxies in the universe and thereby allowing a better constraint on the star formation rate in these objects. The optical design incorporates a 100 mm diameter silicon lens cooled to 4 K, which provides the required fast beam yielding 0.9 lambda1D pixels. With this spatial sampling, GISMO will be very efficient at detecting sources serendipitously in large sky surveys, while the capability for diffraction limited imaging is preserved. The camera provides significantly greater detection sensitivity and mapping speed at this wavelength than has previously been possible. The instrument will fill in the spectral energy distribution of high redshift galaxies at the Rayleigh-Jeans part of the dust emission spectrum, even at the highest redshifts. Here I will we present early results from our observing run with the first fielded BUG bolometer array.

Staguhn, Johannes↗
NASA NTRS1992

optical Instruments for Remote Sensing from Space

This review covers the optical design of passive remote sensing optical instruments. The review concentrates on the design of spaceborne multispectral cameras and imaging spectometers. The major designs that have been produced over the past ten years are discussed, and new designs for future imaging spectrometers are presented.

Optical Instruments Remote Sensing↗
NASA NTRS1988

Optical system design alternatives for the Moderate-Resolution Imaging Spectrometer-Tilt (MODIS-T) for the Earth Observing System (EOS)

The MODIS consists of two synergistic sensors with a total of 104 spectral bands in the 0.4-14.2-micron range. MODIS-T (Tilt) is one of these sensors. It is a 64-channel imaging spectrometer with a required 10 nm spectral resolution (FWHM) in the 400 to 1040 nm spectral range. The system will have a 1 km IFOV, a wide scan for global coverage in three days, and be capable of being pointed fore and aft of nadir by + or - 50 degrees.

Maymon, Peter W.↗
NASA NTRS1993

Overview of microoptics: Past, present, and future

Through advances in semiconductor miniaturization technology, microrelief patterns, with characteristic dimensions as small as the wavelength of light, can now be mass reproduced to form high-quality and low-cost optical components. In a unique example of technology transfer, from electronics to optics, this capability is allowing optics designers to create innovative optical components that promise to solve key problems in optical sensors, optical communication channels, and optical processors.

Veldkamp, Wilfrid B.↗
NASA NTRS2017

Habitable Exoplanet Imager Optical-Mechanical Design and Analysis

The Habitable Exoplanet Imager (HabEx) is a space telescope currently in development whose mission includes finding and spectroscopically characterizing exoplanets. Effective high-contrast imaging requires tight stability requirements of the mirrors to prevent issues such as line of sight and wavefront errors. PATRAN and NASTRAN were used to model updates in the design of the HabEx telescope and find how those updates affected stability. Most of the structural modifications increased first mode frequencies and improved line of sight errors. These studies will be used to help define the baseline HabEx telescope design.

Habe↗