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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 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Systematic adaptation of data delivery

This disclosure describes, in part, a system management component for use in a power grid data network to systematically adjust the quality of service of data published by publishers and subscribed to by subscribers within the network. In one implementation, subscribers may identify a desired data rate, a minimum acceptable data rate, desired latency, minimum acceptable latency and a priority for each subscription and the system management component may adjust the data rates in real-time to ensure that the power grid data network does not become overloaded and/or fail. In one example, subscriptions with lower priorities may have their quality of service adjusted before subscriptions with higher priorities. In each instance, the quality of service may be maintained, even if reduced, to meet or exceed the minimum acceptable quality of service for the subscription.

24 POWER TRANSMISSION AND DISTRIBUTION↗
NASA NTRS2016

Human Flight to Lunar and Beyond - Re-Learning Operations Paradigms

For the first time since the Apollo era, NASA is planning on sending astronauts on flights beyond Low-Earth Orbit (LEO). The Human Space Flight (HSF) program started with a successful initial flight in Earth orbit, in December 2014. The program will continue with two Exploration Missions (EM) to Lunar orbit: EM-1 will be unmanned and EM-2, carrying astronauts, will follow. NASA established a multi-center team to address the communications, and related navigation, needs. This paper will focus on the lessons learned in the team, planning for the missions' parts that are beyond Earth orbit. Many of these lessons had to be re-learned, as the HSF program after operated for many years in Earth orbit. Fortunately, the experience base from tracking robotic missions in deep space by the Deep Space Network (DSN) and close interaction with the HSF community to understand the unique needs (e.g. 2-way voice) resulted in a ConOps that leverages of both the deep space robotic and the Human LEO experiences. Several examples will be used to highlight the unique operational needs for HSF missions beyond Earth Orbit, including: - Navigation. At LEO, HSF missions can rely on Global Positioning System (GPS) devices for orbit determination. For Lunar-and-beyond HSF missions, techniques such as precision 2-way and 3-way Doppler and ranging, Delta-Difference-of-range, and eventually on-board navigation will be used. - Impact of latency - the delay associated with Round-Trip-Light-Time (RTLT). Imagine trying to have a 2-way discussion (audio or video) with an astronaut, with a 2-3 sec delay inserted (for Lunar distances) or 20 minutes delay (for Mars distances). - Balanced communications link. For robotic missions, there has been a heavy emphasis on the downlink data rates, bringing back science data from the instruments on-board the spacecraft. Uplink data rates were of secondary importance, used to send commands to the spacecraft. The ratio of downlink-to-uplink data rates was often 10:1 or more. For HSF, rates for uplink and downlink, at least for high-quality video, need to be similar.

Kenny, Ted↗
NASA NTRS2015

Ka-Band Parabolic Deployable Antenna (KaPDA) Enabling High Speed Data Communication for CubeSats

CubeSats are at a very exciting point as their mission capabilities and launch opportunities are increasing. But as instruments become more advanced and operational distances between CubeSats and earth increase communication data rate becomes a mission-limiting factor. Improving data rate has become critical enough for NASA to sponsor the Cube Quest Centennial Challenge when: one of the key metrics is transmitting as much data as possible from the moon and beyond Currently, many CubeSats communicate on UHF bands and those that have high data rate abilities use S-band or X-band patch antennas. The CubeSat Aneas, which was launched in September 2012, pushed the envelope with a half-meter S-band dish which could achieve 100x the data rate of patch antennas. A half-meter parabolic antenna operating at Ka-band would increase data rates by over 100x that of the AMOS antenM and 10,000 that of X-band patch antennas.

Sauder, Jonathan F.↗
NASA NTRS1985

A sequential decoding performance analysis for International Comet Explorer

The effect of a noisy reference carrier on the performance of International Comet Explorer (ICE) Sequential decoder is analyzed. Ideal reference models for frame deletion probability are given for the Telemetry Processing Assembly (TPA) and the Linkabit (LS4815) sequential decoders. Based on these ideal reference models the deletion probability in the presence of noisy reference carrier is computed for both the high and the low data rate cases. A medium data rate performance model is then derived using an interpolation method. The derived medium rate performance model depends on the phase locked loop bandwidth-integration time product. Results are obtained for frame length 1024 bits, data bit rates of 1024 bps and 512 bps, modulation index of 60 deg, and threshold loop bandwidths of 10 Hz and 3 Hz. The medium rate model agrees with experimental data to within measurement uncertainty. For the 10 Hz loop bandwidth and modulation index of 60 deg at frame deletion rate of 0.0001, the required total received power to noise ratio is 36 dB. The analysis given is general and applicable to any sequential decoder, provided that the ideal reference model of the decoder is available.

Divsalar, D.↗
NASA NTRS1991

An algorithm to design a multiple-channel communications system

The authors present a novel algorithm to design a phase-modulated residual carrier communications system for optimum performance. The algorithm has been developed as an aid in the design of two telemetry data channels operating simultaneously with a turn-around ranging signal. The algorithm provides the selection of an optimum subcarrier frequency and modulation indices for minimizing the mutual interferences among the channels to achieve desired link performance margins. The set of modulation indices provided by this algorithm will also achieve an optimum power division between the carrier, the ranging and the high data rate and low data rate channels. Finally, a software program using this algorithm has been developed for use with personal computers. This program provides the computation of the optimum subcarrier frequencies and modulation indices for a standard case that is recommended by the international Consultative Committee for Space Data Systems.

Nguyen, Tien M.↗
NASA NTRS2011

The Impact of Traffic Prioritization on Deep Space Network Mission Traffic

A select number of missions supported by NASA's Deep Space Network (DSN) are demanding very high data rates. For example, the Kepler Mission was launched March 7, 2009 and at that time required the highest data rate of any NASA mission, with maximum rates of 4.33 Mb/s being provided via Ka band downlinks. The James Webb Space Telescope will require a maximum 28 Mb/s science downlink data rate also using Ka band links; as of this writing the launch is scheduled for a June 2014 launch. The Lunar Reconnaissance Orbiter, launched June 18, 2009, has demonstrated data rates at 100 Mb/s at lunar-Earth distances using NASA's Near Earth Network (NEN) and K-band. As further advances are made in high data rate space telecommunications, particularly with emerging optical systems, it is expected that large surges in demand on the supporting ground systems will ensue. A performance analysis of the impact of high variance in demand has been conducted using our Multi-mission Advanced Communications Hybrid Environment for Test and Evaluation (MACHETE) simulation tool. A comparison is made regarding the incorporation of Quality of Service (QoS) mechanisms and the resulting ground-to-ground Wide Area Network (WAN) bandwidth necessary to meet latency requirements across different user missions. It is shown that substantial reduction in WAN bandwidth may be realized through QoS techniques when low data rate users with low-latency needs are mixed with high data rate users having delay-tolerant traffic.

prioritization↗
NASA NTRS2011

The Impact of Traffic Prioritization on Deep Space Network Mission Traffic

A select number of missions supported by NASA's Deep Space Network (DSN) are demanding very high data rates. For example, the Kepler Mission was launched March 7, 2009 and at that time required the highest data rate of any NASA mission, with maximum rates of 4.33 Mb/s being provided via Ka band downlinks. The James Webb Space Telescope will require a maximum 28 Mb/s science downlink data rate also using Ka band links; as of this writing the launch is scheduled for a June 2014 launch. The Lunar Reconnaissance Orbiter, launched June 18, 2009, has demonstrated data rates at 100 Mb/s at lunar-Earth distances using NASA's Near Earth Network (NEN) and K-band. As further advances are made in high data rate space telecommunications, particularly with emerging optical systems, it is expected that large surges in demand on the supporting ground systems will ensue. A performance analysis of the impact of high variance in demand has been conducted using our Multi-mission Advanced Communications Hybrid Environment for Test and Evaluation (MACHETE) simulation tool. A comparison is made regarding the incorporation of Quality of Service (QoS) mechanisms and the resulting ground-to-ground Wide Area Network (WAN) bandwidth necessary to meet latency requirements across different user missions. It is shown that substantial reduction in WAN bandwidth may be realized through QoS techniques when low data rate users with low-latency needs are mixed with high data rate users having delay-tolerant traffic.

quality of service↗
NASA NTRS1972

An improved learning decoder

Learning decoder was developed which operates at system data rate without limiting data rate. Decoder is much simpler than those in existence, operates near Shannon's channel capacity, and automatically recovers operation after loss of signal.

Doland, G. D.↗
NASA NTRS1972

Tracking and data relay satellite system configuration and tradeoff study. Volume 7: Telecommunications system summary, part 1

The baseline Tracking and Data Relay Satellite telecommunication system is described. The configurations of the user spacecraft terminal and the ground based terminal are illustrated. The system service and performance summary is developed to show the link support, modes of operation, and link performance to the low data rate and medium data rate user spacecraft. The link budget calculation is included to show a typical computation for each space-to-space and space-to-ground link with the assumptions used in each calculation.

Hill, T. E.↗
NASA NTRS1979

Multiple speed expandable bit synchronizer

A multiple speed bit synchronizer was designed for installation in an inertial navigation system data decoder to extract non-return-to-zero level data and clock signal from biphase level data. The circuit automatically senses one of four pre-determined biphase data rates and synchronizes the proper clock rate to the data. Through a simple expansion of the basic design, synchronization of more than four binarily related data rates can be accomplished. The design provides an easily adaptable, low cost, low power alternative to external bit synchronizers with additional savings in size and weight.

Bundinger, J. M.↗
NASA NTRS1996

New TDRSS communications options for small satellites

The NASA uses a space network which includes the tracking and data relay satellite system (TDRSS) for the provision of reliable low data rate and high data rate relay services between user spacecraft in earth orbit and the ground. In relation to future small satellite designs, new communication options for the TDRSS support of small spacecraft missions are reported on. The technologies considered include new transponder technologies, evolution to Ka band frequencies and a TDRSS demand access service capability. Multiple access aspects are considered.

Zillig, David J.↗
NASA NTRSDate not supplied

NASA Lunar Exploration – Gateway’s Power and Propulsion Element Communications Links

As a key part of NASA’s Artemis program to return to the moon, the Lunar Gateway will provide a platform for staging lunar missions, for gaining experience in operations beyond earth orbit, and for creating sustainable infrastructure. Of specific interest, the Lunar Gateway will provide communications support to landers, orbiters, and surface systems, including in the South Polar Region where direct line of sight (LOS) to Earth is limited or non-existent. A foundational segment of the Gateway is the Power and Propulsion Element (PPE), which will carry: solar arrays to provide power to the Gateway; electric propulsion to maintain the Gateway in its operational orbit; and communication links between the Earth and Gateway, the Moon and Gateway, and relays from the Moon to the Earth. PPE Communication Links include an X-band link to Earth for Command, Ranging, and Telemetry (CR&T), which also carries low to medium rate data; a Ka-band Direct to Earth(DTE) link for high rate data transmissions; and a Ka-band Lunar link for high data rate connections to lunar systems. This paper describes the PPE communication links from a technical perspective. Other Gateway links supported by other modules are outside the scope of this paper.

ARTEMIS↗
DOE OSTI2023

Apparatus and methods for managing packet transfer across a memory fabric physical layer interface

An apparatus and method for managing packet transfer between a memory fabric having a physical layer interface higher data rate than a data rate of a physical layer interface of another device, receives incoming packets from the memory fabric physical layer interface wherein at least some of the packets include different instruction types. The apparatus and method determine a packet type of the incoming packet received from the memory fabric physical layer interface and when the determined incoming packet type is of a type containing an atomic request, the method and apparatus prioritizes transfer of the incoming packet with the atomic request over other packet types of incoming packets, to memory access logic that accesses local memory within an apparatus.

Blagodurov, Sergey↗
NASA NTRS1987

Analysis of the Continuous Stellar Tracking Attitude Reference (CSTAR) attitude rate processor

The Continuous Stellar Tracking Attitude Reference (CSTAR) system is an in-house project for Space Station to provide high accuracy, drift free attitude and angular rate information for the GN&C system. The outputs of the solid state star trackers are processed to provide attitude information; rate data is then derived from the attitude. Rate derivation is based on discrete time polynomial approximation techniques. This gives simple algorithms which allow for interpolation by other users. Attitude rate is modeled as a constant with low amplitude, low frequency sinusoids superimposed. The rate processor is parameterized to account for the effects of random errors, sample rate, data processing rate and perturbation frequency. The baseline system may be characterized as follows: the three sigma attitude accuracy is 0.01 degrees, the three sigma rate accuracy is 0.0001 degrees per second, the sample rate is 100 Hertz, the sampled signal is bandlimited to 0.5 Hertz, and the data processing rate is 10 Hertz. The above system requires a differentiator of length 127. This will track rate perturbations of frequencies less than 0.01 Hertz with low systematic errors.

Uhde-Lacovara, J.↗
NASA NTRS2006

General Solution for Theoretical Packet Data Loss Rate

Communications systems which transfer blocks ("frames") of data must use a marker ("frame synchronization pattern") for identifying where a block begins. A technique ("frame synchronization strategy") is used to locate the start of each frame and maintain synchronization as additional blocks are processed. A device which strips out the frame synchronization pattern [FSP] and provides an "end of frame" pulse is called a frame synchronizer. As clock and data errors are introduced into the system, the start-of-block marker becomes displaced and/or corrupted. The capability of the frame synchronizer to stay locked to the pattern under these conditions is a figure of merit for the frame synchronization strategy. It is important to select a strategy which will stay locked nearly all the time at bit error rates where the data is usable. ("Bit error rate" [BER] is the fraction of binary bits which are inverted by passage through a communication system.) The fraction of frames that are discarded because the frame synchronizer is not locked is called "Percent Data Loss" or "Packet Data Loss rate" [PDL]. A general approach for accurately predicting PDL given BER was developed in Theoretical Percent Data Loss Calculation and Measurement Accuracy, T. P. Kelly, LESC-30554, December 1992. Kelly gave a solution in terms of matrix equations, and only addressed "level" channel encoding. This paper goes on to give a closed-form polynomial solution for the most common class of frame synchronizer strategies, and will also address "mark" and "space" (differential) channel encoding, and burst error environments. The paper is divided into four sections and follows a logically ordered presentation, with results developed before they are evaluated. However, most readers will derive the greatest benefit from this paper by treating the results as reference material. The result developed for differential encoding can be extended to other applications (like block codes) where the probability is needed that a block contains only a certain number of errors.

Lansdowne, Chatwin↗
NASA NTRS2016

Human Flight to Lunar and Beyond - Re-Learning Operations Paradigms

For the first time since the Apollo era, NASA is planning on sending astronauts on flights beyond LEO. The Human Space Flight (HSF) program started with a successful initial flight in Earth orbit, in December 2014. The program will continue with two Exploration Missions (EM): EM-1 will be unmanned and EM-2, carrying astronauts, will follow. NASA established a multi-center team to address the communications, and related tacking/navigation needs. This paper will focus on the lessons learned by the team designing the architecture and operations for the missions. Many of these Beyond Earth Orbit lessons had to be re-learned, as the HSF program has operated for many years in Earth orbit. Unlike the Apollo missions that were largely tracked by a dedicated ground network, the HSF planned missions will be tracked (at distances beyond GEO) by the DSN, a network that mostly serves robotic missions. There have been surprising challenges to the DSN as unique modern human spaceflight needs stretch the experience base beyond that of tracking robotic missions in deep space. Close interaction between the DSN and the HSF community to understand the unique needs (e.g. 2-way voice) resulted in a Concept of Operations (ConOps) that leverages both the deep space robotic and the Human LEO experiences. Several examples will be used to highlight the unique challenges the team faced in establishing the communications and tracking capabilities for HSF missions beyond Earth Orbit, including: Navigation. At LEO, HSF missions can rely on GPS devices for orbit determination. For Lunar-and-beyond HSF missions, techniques such as precision 2-way and 3-way Doppler and ranging, Delta-Difference-of-range, and eventually possibly on-board navigation will be used. At the same time, HSF presents a challenge to navigators, beyond those presented by robotic missions - navigating a dynamic/"noisy" spacecraft. Impact of latency - the delay associated with Round-Trip-Light-Time (RTLT). Imagine trying to have a 2-way discussion (audio or video) with an astronaut, with a 2-3 sec or more delay inserted (for lunar distances) or 20 minutes delay (for Mars distances). Balanced communications link. For robotic missions, there has been a heavy emphasis on higher downlink data rates, e.g. bringing back science data. Higher uplink data rates were of secondary importance, as uplink was used only to send commands (and occasionally small files) to the spacecraft. The ratio of downlink-to-uplink data rates was often 10:1 or more. For HSF, a continuous forward link is established and rates for uplink and downlink are more similar.

Kenny, Edward (Ted)↗
NASA NTRS1988

Bandwidth and power efficient satellite TDMA demodulator and decoder

A proof-of-concept demodulator for TDMA applications requiring high total data rates composed of many low data rate users is proposed. High-spectrum efficiency is obtained via a bandwidth efficient combined modulation and coding system, and low TDMA overhead is obtained via a fast acquiring digital phase lock loop. The system employs a data rate of 200 Mb/s with a bit error rate of better than 5 x 10 to the -7th in the presence of adjacent channel interference 20 dB above the weakest user. The 8-PSK modulation combined with the rate 5/6 forward error correction coding results in a bandwidth efficiency of better than 2 bits/second per Hz.

Ames, Stephen A.↗