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NASA NTRS2019

An Update on the CCSDS Optical Communications Working Group Interoperability Standards

International space agencies around the world are working together in the Interagency Operation Advisory Group (IOAG) and the Consultative Committee for Space Data Systems (CCSDS) to develop interoperability standards for optical communications. The standards support optical communication systems for both Near Earth and Deep Space robotic and human-rated spacecraft. The standards generally address both free space links between spacecraft and free space links between spacecraft and ground. This paper will overview the history and structure of the CCSDS Optical Communications Working Group and provide an update on the set of optical communications standards being developed. The paper will address the ongoing work on High Photon Efficiency communications, High Data Rate communications, and Optical On/Off Keying communications. It will also cover the working being done within CCSDS on documenting atmospheric measurement techniques and link operations concepts.

Edwards, Bernard L.↗

NASA NTRS2015

A Magnetron Sputter Deposition System for the Development of X-Ray Multilayer Optics

The project objective is to establish the capability to deposit multilayer structures for x-ray, neutron, and extreme ultraviolet (EUV) optic applications through the development of a magnetron sputtering deposition system. A specific goal of this endeavor is to combine multilayer deposition technology with the replication process in order to enhance NASA Marshall Space Flight Center's (MSFC's) position as a world leader in the design of innovative x-ray instrumentation through the development of full shell replicated multilayer optics. The development of multilayer structures are absolutely necessary in order to advance the field of x-ray astronomy by pushing the limit for observing the universe to ever-increasing photon energies (i.e., up to 200 keV or higher), well beyond Chandra's (approx.10 keV) and NuStar's (approx.75 keV) capability. The addition of multilayer technology would significantly enhance the x-ray optics capability at MSFC and allow NASA to maintain its world leadership position in the development, fabrication, and design of innovative x-ray instrumentation, which would be the first of its kind by combining multilayer technology with the mirror replication process. This marriage of these technologies would allow astronomers to see the universe in a new light by pushing to higher energies that are out of reach with today's instruments. To this aim, a magnetron vacuum sputter deposition system for the deposition of novel multilayer thin film x-ray optics is proposed. A significant secondary use of the vacuum deposition system includes the capability to fabricate multilayers for applications in the field of EUV optics for solar physics, neutron optics, and x-ray optics for a broad range of applications including medical imaging.

Broadway, David↗

NASA NTRS2004

An Infrared Telescope for Planet Detection and General Astrophysics

NASA plans to launch a Terrestrial Planet Finder (TPF) mission in 2014 to detect and characterize Earth-like planets around nearby stars, perform comparative planetology studies, and obtain general astrophysics observations. During our recently completed a TPF Mission Architecture study for NASA/JPL we developed the conceptual design for a 28-meter telescope with an IR Coronagraph that meets these mission objectives. This telescope and the technology it embodies are directly applicable to future Far-IR and Submillimeter space missions. The detection of a 30th magnitude planet located within 50 milli-arc-seconds of a 5th (Visual) magnitude star is an exceptionally challenging objective. Observations in the thermal infrared (7-17 microns) are somewhat easier since the planet is "only" 15(sup m) fainter than the star at these wavelengths, but many severe challenges must still be overcome. These challenges include: 1. Designing a coronagraph for star:planet separations less than or equal to lambda/D. 2. Developing the deployment scheme for a 28m space telescope that can fit in an existing launch vehicle payload fairing. 3. Generating configuration layouts for the IR telescope, coronagraph, spacecraft bus, sunshade, solar array, and high-gain antenna. 4. Providing: Structural stability to within 10 microns to support the optics. Thermal control to achieve the necessary structural stability, as well as providing a stable (approx. 30K) thermal environment for the optics. Dynamics isolation from potential jitter sources. 5. Minimizing launch mass to provide the maximum payload for the science mission Interfacing to an EELV Heavy launch vehicle, including acoustic and stress loads for the launch environment. 6. Identifying the key technologies (which can be developed by 2009) that will enable TPF mission to be performed. 7. Generating a manufacturing plan that will permit TPF to be developed at a reasonable cost and schedule. Many of these design challenges result in inherently conflicting requirements on the design of TPF. Drawing on our experience with large space telescopes such as the Chandra X-ray Observatory and the Next Generation Space Telescope, we have created a conceptual design for TPF that successfully meets these challenging requirements. This paper describes our solution to these challenges.

Lillie, C. F.↗

NASA NTRS1987

Passive isolation/damping system for the Hubble space telescope reaction wheels

NASA's Hubble Space Telescope contain large, diffraction limited optics with extraordinary resolution and performance for surpassing existing observatories. The need to reduce structural borne vibration and resultant optical jitter from critical Pointing Control System components, Reaction Wheels, prompted the feasibility investigation and eventual development of a passive isolation system. Alternative design concepts considered were required to meet a host of stringent specifications and pass rigid tests to be successfully verified and integrated into the already built flight vehicle. The final design employs multiple arrays of fluid damped springs that attenuate over a wide spectrum, while confining newly introduced resonances to benign regions of vehicle dynamic response. Overall jitter improvement of roughly a factor of 2 to 3 is attained with this system. The basis, evolution, and performance of the isolation system, specifically discussing design concepts considered, optimization studies, development lessons learned, innovative features, and analytical and ground test verified results are presented.

Hasha, Martin D.↗

NASA NTRS2000

Three-Layered Atmospheric Structure in Accretion Disks Around Stellar-Mass Black Holes

Modeling of the x-ray spectra of the Galactic superluminal jet sources GRS 1915+105 and GRO J1655-40 reveals a three-layered atmospheric structure in the inner region of the inner accretion disks. Above the cold and optically thick disk with a temperature of 0.2 to 0.5 kiloelectron volts, there is a warm layer with a temperature of 1.0 to 1.5 kiloelectron volts and an optical depth around 10. Sometimes there is also a much hotter, optically thin corona above the warm layer, with a temperature of 100 kiloelectron volts or higher and an optical depth around unity. The structural similarity between the accretion disks and the solar atmosphere suggests that similar physical processes may be operating in these different systems.

Zhang, S. N.↗

NASA NTRS2014

High Efficiency Quantum Well Waveguide Solar Cells and Methods for Constructing the Same

Photon absorption, and thus current generation, is hindered in conventional thin-film solar cell designs, including quantum well structures, by the limited path length of incident light passing vertically through the device. Optical scattering into lateral waveguide structures provides a physical mechanism to increase photocurrent generation through in-plane light trapping. However, the insertion of wells of high refractive index material with lower energy gap into the device structure often results in lower voltage operation, and hence lower photovoltaic power conversion efficiency. The voltage output of an InGaAs quantum well waveguide photovoltaic device can be increased by employing a III-V material structure with an extended wide band gap emitter heterojunction. Analysis of the light IV characteristics reveals that non-radiative recombination components of the underlying dark diode current have been reduced, exposing the limiting radiative recombination component and providing a pathway for realizing solar-electric conversion efficiency of 30% or more in single junction cells.

Welser, Roger E.↗

NASA NTRS2018

High Efficiency Quantum Well Waveguide Solar Cells and Methods for Constructing the Same

Welser, Roger E.↗

NASA NTRS2003

Simultaneous Temperature and Strain Sensing for Cryogenic Applications Using Dual-Wavelength Fiber Bragg Gratings

A new technique has been developed for sensing both temperature and strain simultaneously by using dual-wavelength fiber-optic Bragg gratings. Two Bragg gratings with different wavelengths were inscribed at the same location in an optical fiber to form a sensor. By measuring the wavelength shifts that resulted from the fiber being subjected to different temperatures and strains, the wavelength-dependent thermo-optic coefficients and photoelastic coefficients of the fiber were determined. This enables the simultaneous measurement of temperature and strain. In this study, measurements were made over the temperature range from room temperature down to about 10 K, addressing much of the low temperature range of cryogenic tanks. A structure transition of the optical fiber during the temperature change was found. This transition caused splitting of the waveforms characterizing the Bragg gratings, and the determination of wavelength shifts was consequently complicated. The effectiveness and sensitivities of these measurements in different temperature ranges are also discussed.

Wu, Meng-Chou↗

NASA NTRS1978

Control concepts for large space structures

A comprehensive program to develop the required control technology was started at Rockwell International's Space Division. A few of the concepts under consideration for attitude, figure, and vibration control of large, flexible space systems are highlighted. In addition, an overview of the Space Division's independent research and development (IR&D) is presented. The direction of the IR&D program was influenced by requirements for electro-optical systems, shuttle erectable structures and satellite power stations.

Quartararo, R. C.↗

NASA NTRS2013

NASA Applications of Structural Health Monitoring Technology

This presentation provides examples of research and development that has recently or is currently being conducted at NASA, with a special emphasis on the application of structural health monitoring (SHM) of aerospace vehicles. SHM applications on several vehicle programs are highlighted, including Space Shuttle Orbiter, the International Space Station, Uninhabited Aerial Vehicles, and Expendable Launch Vehicles. Examples of current and previous work are presented in the following categories: acoustic emission impact detection, multi-parameter fiber optic strain-based sensing, wireless sensor system development, and distributed leak detection.

Fiber Optic Sensors↗

NASA NTRS1998

A 2 THz Heterodyne Array Receiver for SOFIA: Summary of Research

We proposed to perform a comprehensive design study of a 16-element heterodyne array receiver for SOFIA. The array was designed to utilize hot-electron bolometers in an efficient, low-cost waveguide mount to achieve low noise performance between approximately 1500 and 2400 GHz. Due to the prevailing physical conditions in the interstellar medium, this frequency range is one of the richest in the Far-Infra Red (FIR) portion of the spectrum. An array designed for this wavelength range will make excellent use of the telescope and the available atmospheric transmission, and will provide a new perspective on stellar, chemical, and galactic evolution in the present as well as past epochs. A few of the most important molecular and atomic species which the instrument will sample are CII, OI, CO, OH, NII, and CH. The system used the most sensitive detectors available in an efficient optical system. The local oscillator was a compact CO2 pumped far-infrared laser currently under development for SOFIA. The backend spectrometer was an array acousto-optic spectrometer (aAOS). The spectrometer utilizes proven hardware and technologies to provide broadband performance (> 1 GHz per AOS channel) and high spectral resolution (1 MHz) with the maximum sensitivity and minimum complexity and cost. The proposed instrument would be the fastest and most sensitive heterodyne receiver ever to operate in the 1.5 - 2.4 THz band. One of the key technologies developed for the proposed instrument is the laser micromachining of waveguide structures. These structures provide both the optical link between the instrument and the telescope (via an array of efficient feedhorns) and the impedance transformation between the detectors and free space. With the assistance of funds provided from this grant, we were able to fabricate and test the world's first laser micromachined feedhorns. The quality of the waveguide structure is far better than that obtainable using any other fabrication technique. The beam parameters are an excellent match to what is expected from theory. The success of this experiment demonstrates the viability of using laser micromachined components in the development of high performance, large format array receivers. We have continued our development efforts and will propose to build a 2nd generation instrument based on the same design concepts.

Walker, Christopher K.↗

NASA NTRS2006

Cryogenic Test Capability at Marshall Space Flight Center's X-ray Cryogenic Test Facility

Marshall Space Flight Center's X-ray & Cryogenic Test Facility (XRCF) has been performing sub-liquid nitrogen temperature testing since 1999. Optical wavefront measurement, thermal structural deformation, mechanism functional & calibration, and simple cryo-conditioning tests have been completed. Recent modifications have been made to the facility in support of the James Webb Space Telescope (JWST) program. The chamber's payload envelope and the facility s refrigeration capacity have both been increased. Modifications have also been made to the optical instrumentation area improving access for both the installation and operation of optical instrumentation outside the vacuum chamber. The facility's capabilities, configuration, and performance data will be presented.

Kegley, Jeffrey↗

NASA NTRS1996

A 2 THz Heterodyne Array Receiver for SOFIA

We proposed to perform a comprehensive design study of a 16-element heterodyne array receiver for SOFIA. The array was designed to utilize hot-electron bolometers in an efficient, low-cost waveguide mount to achieve low noise performance between approx. 1500 and 2400 GHz. Due to the prevailing physical conditions in the interstellar medium, this frequency range is one of the richest in the FIR portion of the spectrum. An array designed for this wavelength range will make excellent use of the telescope and the available atmospheric transmission, and will provide a new perspective on stellar, chemical, and galaxy evolution in the present as well as past epochs. A few of the most important molecular and atomic species which the instrument will sample are CII, OI, CO, OH, NII, and CH. The system used the most sensitive detectors available in an efficient optical system. The local oscillator was a compact CO2 pumped far-infrared laser currently under development for SOFIA. The backend spectrometer was an array acousto-optic spectrometer (aAOS). The spectrometer utilizes proven hardware and technologies to provide broadband performance (greater than or equal to 1 GHz per AOS channel) and high spectral resolution (1 MHz) with the maximum sensitivity and minimum complexity and cost. The proposed instrument would be the fastest and most sensitive heterodyne receiver ever to operate in the 1.5 - 2.4 THz band. One of the key technologies developed for the proposed instrument is the laser micromachining of waveguide structures. These structures provide both the optical link between the instrument and the telescope (via an array of efficient feedhorns) and the impedance transformation between the detectors and free space. With the assistance of funds provided from this grant, we were able to fabricate and test the world's first laser micromachined feedhorns. The quality of the waveguide structure is far better than that obtainable using any other fabrication technique. The beam parameters are an excellent match to what is expected from theory. The success of this experiment demonstrates the viability of using laser micromachined components in the development of high performance, large format array receivers. Unfortunately, our instrument proposal was not selected as a first generation SOFIA instrument. However, we have continued our development efforts and will propose to build a 2nd generation instrument based on the same design concepts.

Walker, Christopher K.↗

NASA NTRS1993

Evolutionary time scales for circumstellar disks associated with intermediate- and solar-type stars

The frequency with which massive, optically thick disks form around solar-type and intermediate mass stars is determined. Criteria are developed for diagnosing massive, optically thick disks, and the fraction of young, optically visible stars surrounded by such disks is determined. The range of survival times for massive, optically thick disks is determined by determining the fraction of stars surrounded by such disks as a function of stellar age. The existence of the probable descendents of massive, optically thick disks - optically thin dust disks, perhaps analogous to the structures surrounding Vega and Beta Pictoris - is established. The existence of structures in transition between those which are optically thick from the stellar surface outward, and those which are optically thin throughout is established.

Strom, Stephen E.↗

NASA NTRS1997

On the existence of debris clouds in the Space Station orbit: Final results of the EuroMir 1995 impact detector

A flight experiment flown onboard the Mir space station as a part of the Euromir 95 mission is considered. The aim of the experiment was to develop a greater understanding of the effects of the space environment on materials. In addition to the active enumeration of particle impacts and trajectories, the aim was to capture hypervelocity particles for their return to earth. Postflight measurements were performed to determine the flux density, diameters and subsequent effects on various optical thermal control and structural materials. Sensors actively measured the atomic oxygen flux, the contamination depostion and their effects during the mission. Two clouds of small particles were detected during a period of 100 days onboard Mir. It is concluded that the measured momenta of these particles suggests that their size and velocity are such that they cause damage to optics and thermal control surfaces.

Maag, Carl R.↗

NASA NTRS1998

A 2 THz Heterodyne Array Receiver for SOFIA

We proposed to perform a comprehensive design study of a 16-element heterodyne array receiver for SOFIA. The array was designed to utilize hot-electron bolometers in an efficient, low-cost waveguide mount to achieve low noise performance between approx. 1500 and 2400 GHz. Due to the prevailing physical conditions in the interstellar medium, this frequency range is one of the richest in the FIR portion of the spectrum. An array designed for this wavelength range will make excellent use of the telescope and the available atmospheric transmission, and will provide a new perspective on stellar, chemical, and galaxy evolution in the present as well as past epochs. A few of the most important molecular and atomic species which the instrument will sample are CII, OI, CO, OH, NII, and CH. The system used the most sensitive detectors available in an efficient optical system. The local oscillator was a compact CO2 pumped far-infrared laser currently under development for SOFIA. The backend spectrometer was an array acousto-optic spectrometer (aAOS). The spectrometer utilizes proven hardware and technologies to provide broadband performance (greater than or equal to 1 GHz per AOS channel) and high spectral resolution (1 MHz) with the maximum sensitivity and minimum complexity and cost. The proposed instrument would be the fastest and most sensitive heterodyne receiver ever to operate in the 1.5 - 2.4 THz band. One of the key technologies developed for the proposed instrument is the laser micromachining of waveguide structures. These structures provide both the optical link between the instrument and the telescope (via an array of efficient feedhorns) and the impedance transformation between the detectors and free space. With the assistance of funds provided from this grant, we were able to fabricate and test the world's first laser micromachined feedhorns. Figure 1 is a photograph of the 2 THz double feedhorn structure designed and constructed under the auspices of this grant. The quality of the waveguide structure is far better than that obtainable using any other fabrication technique. Figure 2 is the beam pattern obtained from it. The beam parameters are an excellent match to what is expected from theory. The success of this experiment demonstrates the viability of using laser micromachined components in the development of high performance, large format array receivers. Figure 3 is an illustration of the focal plane array concept we developed lot- SOFIA base upon this work. Un- fortunately, our instrument proposal was not selected as a first generation SOFIA instrument. However, we have continued our development efforts and will propose to build a 2nd generation instrument based on the same design concepts. Our work under NAG 2-1057 was very rewarding and we appreciate the opportunity provided by NASA to pursue it. The research led directly to publishing 2 papers (listed below) and the award of an NSF grant to our group to construct a laser micromachining system on the University of Arizona campus.

Walker, Christopher K.↗

NASA NTRS2012

Quasi-Monolithic Structures for Spaceflight Using Hydroxide-Catalysis Bonding

Future space-based missions will take measurements of the universe with unprecedented results. To do this, these missions will require materials and bonding techniques with ever-increasing stability in order to make their measurements. As an example, the Laser Interferometer Space Antenna (LISA) will detect and observe gravitational waves in the 0.1 mHz to 1 Hz frequency range with strain sensitivities on the order of 10(exp -21) at its most sensitive frequency. To make these measurements, critical components such as the optical bench or telescope support structure, will need to have path-length stabilities of better than 1 pm/(square root)Hz. The baseline construction method for the LISA optical bench is to affix fused silica optical components to a Zerodur baseplate using hydroxide-catalysis bonding (HCB). HCB is a recently developed technique that allows the bonding of glasses, some metals, and silicon carbide with significant strength and stability with a bond thickness of less than a few micrometers. In addition, a wide range of surface profiles can be bonded using only a small amount of hydroxide solution. These characteristics make HCB ideal for adhering optical components in complex optical systems. In addition to being used to construct the LISA optical bench, the HCB technique shows great promise for constructing other structures such as hollow retroreflectors to be used for lunar laser ranging, or a visible nulling coronograph to be used for exo-planet detection. Here we present construction techniques that could be used to make an optical bench, hollow retroreflector, nulling coronograph, or other quasi-monolithic structures using HCB. In addition, we present dimensional stability results of an optical bench that was made using HCB, as well as HCB strength measurements.

Preston, Alix↗

NASA NTRS1987

Radial image transfer by cylindrical, step-index optical waveguides

The theoretical extent of image transfer by perfect, cylindrical, step-index optical waveguides is examined. Azimuthal image structure is essentially removed by such waveguides, while substantial radial image structure is transmitted. The consequences of this behavior for optical-fiber image scramblers are discussed; such devices may be unsuitable for simple photometric applications but appear to be potentially useful in reducing zonal errors in slit spectroscopy.

Heacox, William D.↗