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At least 775 records · Page 43

Fiber optic and laser sensors IX; Proceedings of the Meeting, Boston, MA, Sept. 3-5, 1991

The present volume on fiber-optic and laser sensors discusses industrial applications of fiber-optic sensors, fiber-optic temperature sensors, fiber-optic current sensors, fiber-optic pressure/displacement/vibration sensors, and generic fiber-optic systems. Attention is given to a fiber-sensor design for turbine engines, fiber-optic remote Fourier transform IR spectroscopy, near-IR fiber-optic temperature sensors, and an intensity-type fiber-optic electric current sensor. Topics addressed include fiber-optic magnetic field sensors based on the Faraday effect in new materials, diaphragm size and sensitivity for fiber-optic pressure sensors, a microbend pressure sensor for high-temperature environments, and linear position sensing by light exchange between two lossy waveguides. Also discussed are two-mode elliptical-core fiber sensors for measurement of strain and temperature, a fiber-optic interferometric X-ray dosimeter, fiber-optic interferometric sensors using multimode fibers, and optical fiber sensing of corona discharges.

Depaula, Ramon P.↗

International Space Station (ISS) Accommodation of a Single US Assured Crew Return Vehicle (ACRV)

The following report was generated to give the International Space Station (ISS) Program some additional insight into the operations and issues associated with accommodating a single U.S. developed Assured Crew Return Vehicle (ACRV). During the generation of this report, changes in both the ISS and ACRV programs were factored into the analysis with the realization that most of the work performed will eventually need to be repeated once the two programs become more integrated. No significant issues associated with the ISS accommodating the ACRV were uncovered. Kinematic analysis of ACRV installation showed that there are viable methods of using Shuttle and Station robotic manipulators. Separation analysis demonstrated that the ACRV departure path clears the Station structure for all likely contingency scenarios. The payload bay packaging analysis identified trades that can be made between payload bay location, Shuttle Remote Manipulator System (SRMS) reach and eventual designs of de-orbit stages and docking adapters.

Mazanek, Daniel D.↗

Cloud Thickness from Diffusion of Lidar Pulses in Clouds

Measurements of the distribution of reflected light from a laser beam incident on an aqueous suspension of particles or "cloud" with known thickness and particle size distribution are reported. The distribution is referred to as the "cloud radiative Green's function", G. In the diffusion domain, G is sensitive to cloud thickness, allowing that important quantity to be retrieved. The goal of the laboratory simulation is to provide preliminary estimates of sensitivity of G to cloud thickness,for use in the optimal design of an offbeam Lidar instrument for remote sensing of cloud thickness (THOR, Thickness from Offbeam Returns). These clouds of polystyrene microspheres suspended in water are analogous to real clouds of water droplets suspended in air. The microsphere size distribution is roughly lognormal, from 0.5 microns to 25 microns, similar to real clouds. Density of suspended spheres is adjusted so mean-free-path of visible photons is about 10 cm, approximately 1000 times smaller than in real clouds. The light source is a ND:YAG laser at 530 nm. Detectors are flux and photon-counting Photomultiplier Tube (PMTS), with a glass probe for precise positioning. A Labview 5 VI controls positioning, and data acquisition, via an NI Motion Control board connected to a stepper motor driving an Edmund linear slider, and a 16-channel 16-bit NI-DAQ board. The stepper motor is accurate to 10 microns, and step size is selectable from the VI software. Far from the incident beam, the rate of exponential increase as the direction of the incident beam is approached scales as expected from diffusion theory, linearly with the cloud thickness, and inversely as the square root of the reduced optical thickness, and is independent of particle size. Near the beam the signal begins to increase faster than exponential, due to single and low-order scattering near the backward direction, and here the distribution depends on particle size. Results are being used to verify 3D Monte Carlo radiative transfer simulations, used to estimate signal-to-noise ratios for remotely sensed off beam returns, for both homogeneous and inhomogeneous clouds. Signal-to-noise estimates show that unfiltered observations are straight forward at night, while narrow band pass filters are being studied for day.

Cahalan, Robert F.↗

Diffuse Reflection of Laser Light From Clouds

Laser light reflected from an aqueous suspension of particles or "cloud" with known thickness and particle size distribution defines the "cloud radiative Green's function", G. G is sensitive to cloud thickness, allowing retrieval of that important quantity. We describe a laboratory simulation of G, useful in design of an offbeam Lidar instrument for remote sensing of cloud thickness. Clouds of polystyrene microspheres suspended in water are analogous to real clouds of water droplets suspended in air. The size distribution extends from 0.5 microns to 25 microns, roughly lognormal, similar to real clouds. Density of suspended spheres is adjusted so photon mean-free-path is about 10 cm, 1000 times smaller than in real clouds. The light source is a Nd:YAG laser at 530 nm. Detectors are flux and photon-counting PMTs, with a glass probe for precise positioning. A Labview 5 VI controls position and data acquisition, via an NI Motion Control board connected to a stepper motor driving an Edmund linear slider,and a 16-channel 16-bit NI-DAQ board. The stepper motor is accurate to 10 microns. Step size is selectable. Far from the beam, the rate of exponential increase in the beam direction scales as expected from diffusion theory, linearly with cloud thickness, and inversely as the square root of the reduced optical thickness, independent of particle size. Nearer the beam the signal increases faster than exponential and depends on particle size. Results verify 3D Monte Carlo simulations that demonstrate detectability of remotely sensed offbeam returns, without filters at night, with narrow bandpass filter in day.

Cahalan, R. F.↗

Use of MODIS-Derived Fire Radiative Energy to Estimate Smoke Aerosol Emissions over Different Ecosystems

Biomass burning is the main source of smoke aerosols and certain trace gases in the atmosphere. However, estimates of the rates of biomass consumption and emission of aerosols and trace gases from fires have not attained adequate reliability thus far. Traditional methods for deriving emission rates employ the use of emission factors e(sub x), (in g of species x per kg of biomass burned), which are difficult to measure from satellites. In this era of environmental monitoring from space, fire characterization was not a major consideration in the design of the early satellite-borne remote sensing instruments, such as AVHRR. Therefore, although they are able to provide fire location information, they were not adequately sensitive to variations in fire strength or size, because their thermal bands used for fire detection saturated at the lower end of fire radiative temperature range. As such, hitherto, satellite-based emission estimates employ proxy techniques using satellite derived fire pixel counts (which do not express the fire strength or rate of biomass consumption) or burned areas (which can only be obtained after the fire is over). The MODIS sensor, recently launched into orbit aboard EOS Terra (1999) and Aqua (2002) satellites, have a much higher saturation level and can, not only detect the fire locations 4 times daily, but also measures the at-satellite fire radiative energy (which is a measure of the fire strength) based on its 4 micron channel temperature. Also, MODIS measures the optical thickness of smoke and other aerosols. Preliminary analysis shows appreciable correlation between the MODIS-derived rates of emission of fire radiative energy and smoke over different regions across the globe. These relationships hold great promise for deriving emission coefficients, which can be used for estimating smoke aerosol emissions from MODIS active fire products. This procedure has the potential to provide more accurate emission estimates in near real-time, providing opportunities for various disaster management applications such as alerts, evacuation and, smoke dispersion forecasting.

Ichoku, Charles↗

Tracking capability for entry, descent and landing and its support to NASA Mars Exploration Rovers

This paper described a new capability recently deployed in the NASA Deep Space Network to support the entry, descent and landing of the two Mars Exploration Rovers - Spirit and Opportunity. This final segment of a 7-month journey was critical step in enabling successful mission operation. The EDL Data Analysis (EDA) equipment processed the open loop recording samples from the existing radio science receivers, extracted the MFSK-modulated tones, and provided information on the occurrence of associated events happened onboard spacecraft. The EDA software supported real-time as well as post pass processing. The design flexibility allowed the track to be divided into different segments, each could be processed with a configuration optimized for its signal conditions and uncertainties. The use of dynamic lock state concept enabled signal detection be done with minimum required computing power - less was spent when signal was steadily detected and more when signal fluctuated. With the server-client design, the EDA supported connections to different remote operation centers for monitor purpose. The paper also presented the field results from both Spirit and Opportunity landings. The detection were much better than anticipated. All critical event tones were seen in real time. Surprising detection of LCP signal was found with Spirit landing, resulted in a reconfiguration for Opportunity landing to maximize signal detection.

tracking↗

Portable Intravenous Fluid Production Device For Ground Use Project

Several medical conditions require the administration of intravenous (IV) fluids,but limitations of mass, volume, shelf-life, transportation, and local resources can restrict the availability of these important fluids. Such limitations are expected in long-duration space exploration missions and in remote or austere places on Earth. This design uses regular drinking water that is pumped through two filters to produce, in minutes, sterile, ultrapure water that meets the stringent quality standards of the United States Pharmacopeia for Water for Injection (Total Bacteria, Conductivity, Endo - toxins, Total Organic Carbon). The device weighs 2.2 lb (1 kg) and is 10 in. long, 5 in. wide, and 3 in. high (≈25, 13, and 7.5 cm, respectively) in its storage configuration. This handheld device produces one liter of medical-grade water in 21 minutes. Total production capacity for this innovation is expected to be in the hundreds of liters. The device contains one battery powered electric mini-pump. Alternatively, a manually powered pump can be attached and used. Drinking water enters the device from a source water bag, flows through two filters, and final sterile production water exits into a sealed, medical-grade collection bag. The collection bag contains pre-placed crystalline salts to mix with product water to form isotonic intravenous medical solutions. Alternatively, a hypertonic salt solution can be injected into a filled bag. The filled collection bag is detached from the device and is ready for use or storage. This device currently contains one collection bag, but a manifold of several pre-attached bags or replacement of single collection bags under sterile needle technique is possible for the production of multiple liters. The entire system will be flushed, sealed, and radiation-sterilized. Operation of the device is easy and requires minimal training. Drinking water is placed into the collection bag. Inline stopcock flow valves at the source and collection bags are opened, and the mini-pump is turned on by a switch to begin fluid flow. When the collection bag is completely filled with the medical- grade water, the pump can be turned off. The pump is designed so it cannot pump air, and overfilling of the collection bag with fluid is avoided by placing an equal amount of water in the source bag. Backflow is avoided by inline check valves. The filled collection bag is disconnected from its tubing and is ready for use. The source bag can be refilled for production of multiple liters, or the source bag can be replaced with an input tube that can be placed in a larger potable water source if the device is attended. The device functions in all orientations independent of any gravity fields. In addition to creating IV fluids, the device produces medical-grade water, which can be used for mixing with medications for injection, reconstituting freeze-dried blood products for injection, or for wound hydration or irrigation. Potential worldwide use is expected with medical activities in environments that have limited resources, storage, or resupply such as in military field operations, humanitarian relief efforts, submarines, commercial cruise ships, etc.

Technology Portfolio System↗

Robust Modal Filtering and Control of the X-56A Model with Simulated Fiber Optic Sensor Failures

The X-56A aircraft is a remotely-piloted aircraft with flutter modes intentionally designed into the flight envelope. The X-56A program must demonstrate flight control while suppressing all unstable modes. A previous X-56A model study demonstrated a distributed-sensing-based active shape and active flutter suppression controller. The controller relies on an estimator which is sensitive to bias. This estimator is improved herein, and a real-time robust estimator is derived and demonstrated on 1530 fiber optic sensors. It is shown in simulation that the estimator can simultaneously reject 230 worst-case fiber optic sensor failures automatically. These sensor failures include locations with high leverage (or importance). To reduce the impact of leverage outliers, concentration based on a Mahalanobis trim criterion is introduced. A redescending M-estimator with Tukey bisquare weights is used to improve location and dispersion estimates within each concentration step in the presence of asymmetry (or leverage). A dynamic simulation is used to compare the concentrated robust estimator to a state-of-the-art real-time robust multivariate estimator. The estimators support a previously-derived mu-optimal shape controller. It is found that during the failure scenario, the concentrated modal estimator keeps the system stable.

Modal Filtering↗

Portable Remote Imaging Spectrometer (PRISM): Laboratory and Field Calibration

We report the characteristics of the Portable Remote Imaging Spectrometer, an airborne sensor specifically designed for the challenges of coastal ocean research. PRISM has high signal to noise ratio and uniformity, as well as low polarization sensitivity. Acquisition of high quality data has been demonstrated with the first engineering flight.

imaging spectrometer↗

The DESDynI Synthetic Aperture Radar Array-Fed Reflector Antenna

DESDynI is a mission being developed by NASA with radar and lidar instruments for Earth-orbit remote sensing. This paper focuses on the design of a largeaperture antenna for the radar instrument. The antenna comprises a deployable reflector antenna and an active switched array of patch elements fed by transmit/ receive modules. The antenna and radar architecture facilitates a new mode of synthetic aperture radar imaging called 'SweepSAR'. A system-level description of the antenna is provided, along with predictions of antenna performance.

Chamberlain, Neil↗

Fiber-Based, Trace-Gas, Laser Transmitter Technology Development for Space

NASA’s Goddard Space Flight Center (GSFC) is working on maturing the technology readiness of a laser transmitter designed for use in atmospheric CO2 remote-sensing. GSFC has been developing an airplane-based CO2 lidar instrument over several years to demonstrate the efficacy of the instrumentation and measurement technique and to link the science models to the instrument performance. The ultimate goal is to make space-based satellite measurements with global coverage. In order to accomplish this, we must demonstrate the technology readiness and performance of the components as well as demonstrate the required power-scaling to make the link with the required signal-to-noise-ratio (SNR). To date, all the instrument components have been shown to have the required performance with the exception of the laser transmitter.In this program we are working on a fiber-based master oscillator power amplifier (MOPA) laser transmitter architecture where we will develop a ruggedized package and perform the relevant environmental tests to demonstrate TRL-6. In this paper we will review our transmitter architecture and progress on the performance and packaging of the laser transmitter.

Laser↗

Robust Modal Filtering and Control of the X-56A Model with Simulated Fiber Optic Sensor Failures

The X-56A aircraft is a remotely-piloted aircraft with flutter modes intentionally designed into the flight envelope. The X-56A program must demonstrate flight control while suppressing all unstable modes. A previous X-56A model study demonstrated a distributed-sensing-based active shape and active flutter suppression controller. The controller relies on an estimator which is sensitive to bias. This estimator is improved herein, and a real-time robust estimator is derived and demonstrated on 1530 fiber optic sensors. It is shown in simulation that the estimator can simultaneously reject 230 worst-case fiber optic sensor failures automatically. These sensor failures include locations with high leverage (or importance). To reduce the impact of leverage outliers, concentration based on a Mahalanobis trim criterion is introduced. A redescending M-estimator with Tukey bisquare weights is used to improve location and dispersion estimates within each concentration step in the presence of asymmetry (or leverage). A dynamic simulation is used to compare the concentrated robust estimator to a state-of-the-art real-time robust multivariate estimator. The estimators support a previously-derived mu-optimal shape controller. It is found that during the failure scenario, the concentrated modal estimator keeps the system stable.

Modal Filtering↗

Leveraging Medical Operations in the Work of HRP Exploration Medical Capability

Aerospace Medicine focuses on humans in the space and aviation environments. Particularly, through medical system design, advancing technologies for clinical care in remote and extreme environments, and studying the complex physiological changes that occur when humans are placed in these extreme environments, it seeks to prepare humans for the next step of exploration. For reasons of organization and funding, there has historically been a division between NASA’s medical operations team, responsible for clinical care and near-term operations, and the research team, responsible for longer-term exploration mission work. Clinicians typically work for one group or the other. Recently, however, a new “blended clinician” position was created that functions as a bridge between medical operations and research, bringing insight and expertise to both teams.

E.R. Stratton↗

Innovative Approaches to the Decommissioning of a Redundant Plutonium Processing Facility - 20147

At Sellafield, in the North West of the United Kingdom (UK), there are a number of redundant plutonium processing facilities. Over the past three decades several decommissioning strategies have been deployed to clean up these redundant facilities. Whilst there have been many successes previously reported, there remain many challenges. As previously presented at WM2017 (Paper Ref 17081) some of these challenges have recently been addressed through a new approach which introduced a number of innovations. The purpose of these innovations is to seek ways to significantly reduce risks to both decommissioning personnel and the environment by minimising the extent of physical 'hands on' decommissioning activities and by simplifying the waste production process. This paper provides an update on the progress of these innovations since 2017. Additionally, the paper also provides details of the new decommissioning technologies which have been introduced over the past 2 years to enable the most challenging aspects of the redundant plutonium processing facility to be decommissioned. These new decommissioning technologies address challenges associated with the preparation of process vessels and pipework to enable their safe in-situ size reduction by remote means: - New decommissioning techniques have been introduced to allow penetrations to be remotely cut into process vessels and pipework to provide a means of accessing and controlling the venting of any potential hydrogen gas present. - Additionally, a new large scale bespoke remote diamond wire cutting machine has been designed and manufactured to enable the process vessels to be size reduced in situ. Both of these new cutting technologies have involved collaborative working with specialist equipment suppliers including extensive development, trialling demonstration and commissioning prior to bringing the equipment into operational service. Several years of work have now culminated in reaching the final stages of decommissioning of the redundant plutonium processing facility with decommissioning of the final process vessels now underway and completion expected by the end of 2019. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

Automated Fluid Interface System (AFIS)

Automated remote fluid servicing will be necessary for future space missions, as future satellites will be designed for on-orbit consumable replenishment. In order to develop an on-orbit remote servicing capability, a standard interface between a tanker and the receiving satellite is needed. The objective of the Automated Fluid Interface System (AFIS) program is to design, fabricate, and functionally demonstrate compliance with all design requirements for an automated fluid interface system. A description and documentation of the Fairchild AFIS design is provided.

Source record↗

Hand controller commonality evaluation process

Hand controller selection for NASA's Orbiter and Space Station Freedom is an important area of human-telerobot interface design and evaluation. These input devices will control remotely operated systems that include large crane-like manipulators (e.g., Remote Manipulator System or RMS), smaller, more dexterous manipulators (e.g., Flight Telerobotic Servicer or FTS), and free flyers (e.g., Orbital Maneuvering Vehicle or OMV). Candidate hand controller configurations for these systems vary in many ways: shape, size, number of degrees-of-freedom (DOF), operating modes, provision of force reflection, range of movement, and 'naturalness' of use. Unresolved design implementation issues remain, including such topics as how the current Orbiter RMS rotational and translational rate hand controllers compare with the proposed Space Station Freedom hand controllers, the advantages that position hand controllers offer for these applications, and whether separate hand controller configurations are required for each application. Since previous studies contain little empirical hand controller task performance data, a controlled study is needed that tests Space Station Freedom candidate hand controllers during representative tasks. This study also needs to include anthropometric and biomechanical considerations.

Stuart, Mark A.↗

Remote sensing of wetlands

The concept of using remote sensing to inventory wetlands and the related topics of proper inventory design and data collection are discussed. The material presented shows that aerial photography is the form of remote sensing from which the greatest amount of wetlands information can be derived. For extensive, general-purpose wetlands inventories, however, the use of LANDSAT data may be more cost-effective. Airborne multispectral scanners and radar are, in the main, too expensive to use - unless the information that these sensors alone can gather remotely is absolutely required. Multistage sampling employing space and high altitude remote sensing data in the initial stages appears to be an efficient survey strategy for gathering non-point specific wetlands inventory data over large areas. The operational role of remote sensing insupplying inventory data for application to several typical wetlands management problems is illustrated by summary descriptions of past ERIM projects.

Roller, N. E. G.↗

Remotely controlled models slash tunnel time

The employment of a remote-control model system makes it possible to reduce the wind-tunnel time and cost required to define the aerodynamics f a configuration. In support of the Space Shuttle program, several wind-tunnel models with remote-controlled elevons, body flap, and rudder were designed, built, and tested. The models have been tested at Mach numbers in the range from 0.30 to 4.5 and dynamic pressures greater than 2,000 psf. Attention is given to a model for Shuttle approach and landing tests, a model to define the aerodynamic characteristics of the final Shuttle Orbiter configuration, and the time savings made with a remotely controlled model.

Ware, G. M.↗