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All sourcesNASA NTRSDOE OSTI
NASA NTRS2018

Evaluation of Usability and Workload Associated with Paper Strips as Compared to Virtual Flight Strips Used for Ramp Operations

This paper describes a study comparing the use of paper strips with virtual flight strips depicted on a new user interface, the Ramp Traffic Console (RTC), designed for use by ramp controllers to be used in place of paper strips. A Human-In-the-Loop (HITL) experiment was performed as the fifth in a series of six HITL simulation studies designed to evaluate a pushback Decision Support Tool (DST) concept for Charlotte Douglas International Airport (CLT). Workload and usability were assessed in post-run and post-study questionnaires. In the RTC virtual flight strip condition, post-run questionnaire results show lower workload ratings across all aspects of workload; additionally a trend is found toward increased usability ratings. Post-study questionnaire results indicate a preference for RTC over paper strips. Additional research is suggested with more training runs and a greater number of participants to increase statistical power. It is also suggested that this new technology be re-evaluated as a part of the ATD-2 (Airspace Technology Demonstration 2) field testing activities.

Human Factors↗
NASA NTRSDate not supplied

Evaluating SAR Radiometric Terrain Correction Solutions: Optimal products for applied users

Operational applications of Synthetic Aperture Radar (SAR) are under development around the world, driven by the regularly-acquired, free-and-open source C-band SAR observations provided by ESA’s Sentinel-1 sensor constellation since 2014. Groups like SERVIR, a joint NASA and USAID initiative, are at the forefront of remote sensing applications for societal benefit. A takeaway from SERVIR’s experience is the need for appropriately geocoded and fully calibrated SAR data that is ready to use for a range of ecosystems-related applications. Radiometric Terrain Corrected (RTC) data are key entry-level products for multiple applications that range from ecosystems to hazards. This work fills a gap in current research by evaluating several RTCs produced by open-source software solutions (SNAP-7 and ISCE-2), the gold standard commercial software (GAMMA), a Google Earth Engine (GEE) based workflow, and the uncorrected GRD products currently available in GEE. RTCs were analyzed for geolocation quality, absolute radiometric calibration, and fidelity of the radiometric terrain flattening over ten sites representing varied terrains. In addition, a time series analysis was conducted over two locations. Overall, no significant differences for radiometric calibration were found across RTC products. However, all RTCs performed better than uncorrected GRD products. The main differences between products were found in geolocation quality. These results not only demonstrate the need for the uptake and distribution of RTC products for ecosystems applications, but demonstrate the ability to do so with open source methods, adding value to developing affordable operational applications.

Helen Blue Parache↗
NASA NTRS1985

Role of long-wavelength degrees of freedom in the rod-to-coil transition in polymers

An analytical model is fitted to experimental data to show that rod-to-coil (RTC) transformations in single strand polymers (SSPs) are close to true phase transitions. The RTC are known to occur when the temperature or pH of a solvent in which the SSP is immersed is varied abruptly. Long wavelength degrees of freedom in the SSPs induce long range interactions in the molecule which lead to a first order phase transition. The Landau formalism suggests that a long-range ordered state can appear at a low temperature. A microscopic model of the phonon degrees of freedom identifies the nonzero temperature threshold at which the phase transition will occur. The phenomenology described is similar to a previous model for transitions in double-strand polymers.

Goldenfeld, N.↗
NASA NTRS1986

Real-time combiner loss

Telemetry signals from several channels are aligned in time and combined by the Real-Time Combiner (RTC) in order to increase the strength of the total signal. In this article, the impact of the timing jitter in the RTC on the bit/symbol error rate is investigated. Equations are derived for the timing jitter loss associated with the coded and uncoded channels. Included are curves that depict the bit-symbol error rate vs. E sub b/N sub 0 and E sub s/N sub 0 for some typical telemetry conditions. The losses are typically below 0.1 dB.

Simon, M. K.↗
NASA NTRS1989

AMTEC recirculating test cell component testing and operation

Alkali metal thermoelectric converter operation in a recirculating test cell (RTC), which requires a small electromagnetic pump (EM) and a high-temperature beta-double-prime alumina-solid-electrolyte (BASE)-to-metal seal, is discussed. The design of a pump and an active metal braze seal and the initial operation of a cell using these components are described. The pump delivered 0.25 cu cm/min against a 28-psia head. A braze seal system was selected after shear strength tests of Ta or Nb brazed to BASE by a variety of fillers including TiCuNi, TiNi, and TiNiCr. The TiCuNi filler was chosen for environment cell testing and showed no failure or observable degradation after short-term tests up to 1055 K. The pump and the Nb/TiCuNi/BASE seal were used in a test that demonstrated all the operational functions of the RTC for the first time. An increase in the radiation reduction factor at constant input power was observed, indicating that the condenser was being wet by sodium resulting in an increased reflectivity.

Underwood, M. L.↗
NASA NTRS1993

Network and user interface for PAT DOME virtual motion environment system

The Device for Orientation and Motion Environments Preflight Adaptation Trainer (DOME PAT) provides astronauts a virtual microgravity sensory environment designed to help alleviate tye symptoms of space motion sickness (SMS). The system consists of four microcomputers networked to provide real time control, and an image generator (IG) driving a wide angle video display inside a dome structure. The spherical display demands distortion correction. The system is currently being modified with a new graphical user interface (GUI) and a new Silicon Graphics IG. This paper will concentrate on the new GUI and the networking scheme. The new GUI eliminates proprietary graphics hardware and software, and instead makes use of standard and low cost PC video (CGA) and off the shelf software (Microsoft's Quick C). Mouse selection for user input is supported. The new Silicon Graphics IG requires an Ethernet interface. The microcomputer known as the Real Time Controller (RTC), which has overall control of the system and is written in Ada, was modified to use the free public domain NCSA Telnet software for Ethernet communications with the Silicon Graphics IG. The RTC also maintains the original ARCNET communications through Novell Netware IPX with the rest of the system. The Telnet TCP/IP protocol was first used for real-time communication, but because of buffering problems the Telnet datagram (UDP) protocol needed to be implemented. Since the Telnet modules are written in C, the Adap pragma 'Interface' was used to interface with the network calls.

Worthington, J. W.↗
NASA NTRS2014

Robot Task Commander with Extensible Programming Environment

A system for developing distributed robot application-level software includes a robot having an associated control module which controls motion of the robot in response to a commanded task, and a robot task commander (RTC) in networked communication with the control module over a network transport layer (NTL). The RTC includes a script engine(s) and a GUI, with a processor and a centralized library of library blocks constructed from an interpretive computer programming code and having input and output connections. The GUI provides access to a Visual Programming Language (VPL) environment and a text editor. In executing a method, the VPL is opened, a task for the robot is built from the code library blocks, and data is assigned to input and output connections identifying input and output data for each block. A task sequence(s) is sent to the control module(s) over the NTL to command execution of the task.

Hart, Stephen W↗
NASA NTRS2019

Impact of Slot Substitution on CTOP Performance

The Air Traffic Management community has made important progress in collaborative trajectory management through the introduction of an FAA traffic management initiative called a Collaborative Trajectory Options Program (CTOP). A CTOP is also collaborative in that it permits airlines to provide a set of preferred reroute options (called a Trajectory Options Set or TOS) around an FCA. Airlines also specify a Relative Trajectory Cost (RTC) for each trajectory option that specifies cost of each route relative to the most preferred option. CTOP also airlines to do slot substitution. In this report, we discussed a specific scenario where airlines can reduce their delays by specifying relative slot cost as RTC and using subbing aggressively.

Air Traffic Management↗
NASA NTRS2020

The AERONET Version 3 Aerosol Retrieval Algorithm, Associated Uncertainties and Comparisons to Version 2

The Aerosol Robotic Network (AERONET) Version 3 (V3) aerosol retrieval algorithm is described, which is based on the Version 2 (V2) algorithm with numerous updates. Comparisons of V3 aerosol retrievals to those of V2 are presented, along with a new approach to estimate uncertainties in many of the retrieved aerosol parameters. Changes in the V3 aerosol retrieval algorithm include (1) a new polarized radiative transfer code (RTC), which replaced the scalar RTC of V2, (2) detailed characterization of gas absorption by adding NO2 and H2O to specify total gas absorption in the atmospheric column, specification of vertical profiles of all the atmospheric species, (3) new bidirectional reflectance distribution function (BRDF) parameters for land sites adopted from the MODIS BRDF/Albedo product, (4) a new version of the extraterrestrial solar flux spectrum, and (5) a new temperature correction procedure of both direct Sun and sky radiance measurements. The potential effect of each change in V3 on single scattering albedo (SSA) retrievals was analyzed. The operational almucantar retrievals of V2 versus V3 were compared for four AERONET sites: GSFC, Mezaira, Mongu, and Kanpur. Analysis showed very good agreement in retrieved parameters of the size distributions. Comparisons of SSA retrievals for dust aerosols (Mezaira) showed a good agreement in 440 nm SSA, while for longer wavelengths V3 SSAs are systematically higher than those of V2, with the largest mean difference at 675 nm due to cumulative effects of both extraterrestrial solar flux and BRDF changes. For non-dust aerosols, the largest SSA deviation is at 675 nm due to differences in extraterrestrial solar flux spectrums used in each version. Further, the SSA 675 nm mean differences are very different for weakly (GSFC) and strongly (Mongu) absorbing aerosols, which is explained by the lower sensitivity to a bias in aerosol scattering optical depth by less absorbing aerosols. A new hybrid (HYB) sky radiance measurement scan is introduced and discussed. The HYB combines features of scans in two different planes to maximize the range of scattering angles and achieve scan symmetry, thereby allowing for cloud screening and spatial averaging, which is an advantage over the principal plane scan that lacks robust symmetry. We show that due to an extended range of scattering angles, HYB SSA retrievals for dust aerosols exhibit smaller variability with solar zenith angles (SZAs) than those of almucantar (ALM), which allows extension of HYB SSA retrievals to SZAs less than 50∘ to as small as 25∘. The comparison of SSA retrievals from closely time-matched HYB and ALM scans in the 50 to 75∘ SZA range showed good agreement with the differences below ∼0.005. We also present an approach to estimate retrieval uncertainties which utilizes the variability in retrieved parameters generated by perturbing both measurements and auxiliary input parameters as a proxy for retrieval uncertainty. The perturbations in measurements and auxiliary inputs are assumed as estimated biases in aerosol optical depth (AOD), radiometric calibration of sky radiances combined with solar spectral irradiance, and surface reflectance. For each set of Level 2 Sun/sky radiometer observations, 27 inputs corresponding to 27 combinations of biases were produced and separately inverted to generate the following statistics of the inversion results: average, standard deviation, minimum and maximum values. From these statistics, standard deviation (labeled U27) is used as a proxy for estimated uncertainty, and a lookup table (LUT) approach was implemented to reduce the computational time. The U27 climatological LUT was generated from the entire AERONET almucantar (1993–2018) and hybrid (2014–2018) scan databases by binning U27s in AOD (440 nm), Angström exponent (AE, 440–870 nm), and SSA (440, 675, 870, 1020 nm). Using this LUT approach, the uncertainty estimates U27 for each individual V3 Level 2 retrieval can be obtained by interpolation using the corresponding measured and inverted combination of AOD, AE, and SSA.

Aliaksandr Siniuk↗
NASA NTRS2020

An Efficient Area-Based Algorithm for SAR Radiometric Terrain Correction and Map Projection

This article presents a projection algorithm based on the representation of radar samples as area elements, rather than point elements as traditionally done in previous works. Each area element in the geographic grid (geogrid) is associated with a set of samples in the radar grid that intersect completely or partially the area element according to the topography and the radar geometry. Accurate geocoding with adaptive multi-looking is achieved by successively assigning the weighted average of the radar samples to the corresponding geogrid elements. Analogously, the slant-range projection of geocoded data is improved by projecting the geogrid pixels onto the radar grid according to their projected area. When our slant-range projection approach is used within previously-published radiometric terrain correction (RTC) algorithms, the processing time is significantly reduced, performing 3.6 to 5.2 times faster over multi-looked data and up to 8.9 over single-look data. We demonstrate the strength of the area projection algorithm for RTC and geocoding using UAVSAR and Sentinel-1 data, and evaluate the results in the context of the upcoming NISAR mission.

Shiroma, Gustavo H↗
NASA NTRS2020

Design and Performance of the PALM-3000 3.5 kHz Upgrade

PALM-3000 (P3K), the second-generation adaptive optics (AO) instrument for the 5.1 meter Hale telescope atPalomar Observatory, was released as a facility class instrument in October 2011 and has since been used on-skyfor over 600 nights as a workhorse science instrument and testbed for coronagraph and detector development.In late 2019 P3K underwent a significant upgrade to its wavefront sensor (WFS) arm and real-time control(RTC) system to reinforce its position as a state-of-the-art AO facility and extend its faint-end capability forhigh-resolution imaging and precision radial velocity follow-up of Kepler and TESS targets. The main featuresof this upgrade include an EM-CCD WFS camera capable of 3.5 kHz framerates, and an advanced Digital SignalProcessor (DSP) based RTC system to replace the aging GPU based system. Similar to the pre-upgrade system,the Shack-Hartmann wavefront sensor supports multiple pupil sampling modes using a motorized lenslet stage.The default sampling mode with 64×64 subapertures has been re-commissioned on-sky in late 2019, witha successful return to science observations in November 2019. In 64×mode the upgraded system is alreadyachieving K-band Strehl ratios up to 85% on-sky and can lock on natural guide stars as faint as mV=16. A16×16 subaperture mode is scheduled for on-sky commissioning in Fall 2020 and will extend the system’s faintlimit even further. Here we present the design and on-sky re-commissioning results of the upgraded system,dubbed P3K-II.

Vasisht, Gautam↗
NASA NTRS2018

ATD-2 Integrated Arrival/Departure/Surface (IADS) System Software Version 3.1.x Releases and Notes

This document summarizes the change reports for the ATD-2 V3.1.x series of software releases to Charlotte-Douglas International Airport (CLT). These list all the changes since the previous release. The Release Notes for Distribution are meant to be more readable by stakeholders. [Includes updates to changes for RTC (Ramp Traffic Console), Scheduler, STBO (Surface Trajectory-Based Operations), and Surface Metering Display (graphical-user interface, GUI) clients.]

RTC↗
NASA NTRS1976

Viking magnetic properties investigation - Further results

The amounts of magnetic particles held on the reference test chart and backhoe magnets on lander 2 and lander 1 are comparable, indicating the presence of an estimated 3 to 7 percent by weight of relatively pure, strongly magnetic particles in the soil at the lander 2 sampling site. Preliminary spectrophotometric analysis of the material held on the backhoe magnets on lander 1 indicates that its reflectance characteristics are indistinguishable from material within a sampling trench with which it has been compared. The material on the RTC magnet shows a different spectrum, but it is suspected that the difference is the result of a reflectance contribution from the magnesium metal covering on the magnet. It is argued that the results indicate the presence, now or originally, of magnetite, which may be titaniferous.

Hargraves, R. B.↗
NASA NTRS1986

Steady-state probability density function of the phase error for a DPLL with an integrate-and-dump device

The steady-state behavior of a particular type of digital phase-locked loop (DPLL) with an integrate-and-dump circuit following the phase detector is characterized in terms of the probability density function (pdf) of the phase error in the loop. Although the loop is entirely digital from an implementation standpoint, it operates at two extremely different sampling rates. In particular, the combination of a phase detector and an integrate-and-dump circuit operates at a very high rate whereas the loop update rate is very slow by comparison. Because of this dichotomy, the loop can be analyzed by hybrid analog/digital (s/z domain) techniques. The loop is modeled in such a general fashion that previous analyses of the Real-Time Combiner (RTC), Subcarrier Demodulator Assembly (SDA), and Symbol Synchronization Assembly (SSA) fall out as special cases.

Simon, M.↗
NASA NTRS1988

Ammonia transfer across rotating joints in space

Thermal control of future large space facilities, such as the space station, will require the transfer of anhydrous ammonia across rotating joints with near zero leakage. Anhydrous ammonia is the primary heat transfer fluid aboard the station, providing critical thermal management of habitat and payload systems. The solar radiator joints, as well as the various payload pointing systems, are obvious examples of the need for a reliable fluid transfer device. Low weight, tight temperature control, low parasitic drag torque, long life, and high reliability, in addition to near zero leakage, are important characteristics necessary for the successful operation of such a device. In late 1986, Lockheed initiated a project to develop a Rotary Transfer Coupling (RTC) directed toward space station requirements. Fabrication and assembly of this device is now complete and testing is scheduled. The design and development of the face seal-type rotary fluid coupling that utilizes a unique cover gas concept (an inert gas such as nitrogen) to provide full containment of the ammonia was addressed.

Warner, Mark H.↗
NASA NTRS1987

An Ada run-time control architecture for telerobots

This paper describes the architecture and Ada language implementation of a process-level run-time control subystem for the Jet Propulsion Laboratory (JPL) telerobot system. The concept of run-time control in a combined robot-teleoperation environment is examined and the telerobot system at JPL is described. An Ada language implementation of the JPL Telerobot Run-Time Controller (RTC) is described by highlighting the functional behavior of the subsystem, defining the internal modules, and providing a functional flow time sequence of internal module activity.

Balaram, J.↗
NASA NTRS1992

Anodized aluminum coatings for thermal control. II - Environmental effects and cracking

The environmental effects of thermal cycling and humidity on coating cracking are examined. Experimental measurements of thermal deflection were used to calculate values for the thermal expansion coefficient and the in situ elastic modulus of an anodized aluminum. The thermal expansion coefficient is found to be approximately the same as for alumina in bulk form. The modulus in atmospheres with less than 100 ppm water is about 12,500 ksi. Two sets of experiments are used to study cracking directly during thermal excursions: one determines the minimum temperature (Tc) at which cracks first appear during a single heating cycle and the other involves rapid thermal cycling (RTC) between fixed T max and T min values. Fatigue models for describing initiation of the first crack and the development of multiple cracking are presented, which can be used as the basis for prediction of LEO cracking.

Mcclung, R. C.↗
NASA NTRS1992

Efficiency of an AMTEC recirculating test cell, experiments and projections

The alkali metal thermal to electric converter (AMTEC) is an electrochemical device for the direct conversion of heat to electrical energy with efficiencies potentially near Carnot. The future usefulness of AMTEC for space power conversion depends on the efficiency of the devices. Systems studies have projected from 15 to 35 percent thermal to electric conversion efficiencies, and one experiment has demonstrated 19 percent efficiency for a short period of time. Recent experiments in a recirculating test cell (RTC) have demonstrated sustained conversion efficiencies as high as 10.2 percent early in cell life and 9.7 percent after maturity. Extensive thermal and electrochemical analysis of the cell during several experiments demonstrated that the efficiency could be improved in two ways. First, the electrode performance could be improved. The electrode for these tests operated at about one third the power density of state of the art electrodes. The low power density was caused by a combination of high series resistance and high mass flow resistance. Reducing these resistances could improve the efficiency to greater than 10 percent. Second, the cell thermal performance could be improved. Efficiencies greater than 14 percent could be realized through reducing the radiative thermal loss. Further improvements to the efficiency range predicted by systems studies can be accomplished through the development and use of an advanced condenser with improved reflectivity, close to that of a smooth sodium film, and the series connecting of individual cells to further reduce thermal losses.

Underwood, M. L.↗